G35 1in Brake Master Cylinder + Willwood External Clutch Reservoir

Heyooo, so I hated the brake feel immediately and decided to play with some cheap OEM components as a fill in for some more fluid needed for the increased piston area. Low and behold, the 1in G35 MC bolts right on up to the booster, uses a dual channel output, and only required pretty minor mods to get it working.

I grabbed one from ebay, as well as a spare RX8 booster for mock up while I got everything working. The goal was to have as little tearup from the stock system as possible so that if my brakes completely and utterly fail to be good, I can slap back on the stock stuff in an afternoon.

Started by measuring the plunger depth to pushrod and managed to find a standoff on McMaster that would fit perfectly height wise. I believe the part number was: 93655A254. M6x1.0 14mm 26mm total legnth. This would let me drive in the standoff and the stock pushrod all the way for a perfect clearance, and a nice hard material that would be the interface with the MC.



Once I had that on the bench working, I had to grind it down to clear the inner part of the G35 booster that you can see in the background as the 13mm hex portion needed to be < 10mm.



And as much as I love angle grinder mods... I decided to chuck another on the lathe at work to make sure it wasn't ugly.



When I popped the MC in the vehicle I had the realization I needed a bracket for an external reservoir for the clutch system... and literally as I am typing this now, I realize I could have likely swapped over the RX8 reservoir instead of using the Nissan one... so... maybe more on that later hahaha!

Either way, I CADed up a design for a mount that would bolt on to the booster mounting and offset a Wilwood reservoir that was an overkill size. Still trying to finalize that one, but I have a rudimentary steel bent piece that works for now.

I bent up some lines, which took waaaay more time than anticipated, because using my Autozone flare tool made me want to jump off a bridge, so I splurged on the Eastwood bench mounted one. 10/10 tool, would recommend. What I had failed to do was give the lines enough length to fit in the jig to flare the tubes with the hardware on it, so I had to redesign my lines twice.

On the hardware note, it is a huge pain in the *** to find M12x1 1/4in inverted flare fittings. I could only find bubble flare fittings or fittings with a hole size of 6mm. 1/4in is 6.35mm, so they didn't fit around the line. I ended up using the fittings that came with the G35 master.

On the fittings note too: The Bosch ABS system uses bubble flares, and the G35 master uses inverted flares, so make sure if you end up doing this, you get the lines and fittings right. Either way, struggling on dumb things aside, I am really happy with the result.





When I went to bleed the system, I had one HELL of a trim trying to get it to bleed. I ordered myself a new motive adapter for the G35 res (which leaked like a damn sieve, by the way) to try to get some pressure in the system, but could only ever get the secondary channel to bleed. I took it out, spilled fluid all over, and tried to bench bleed it, but it just wasn't taking any fluid in.

Now, I've never actually taken apart a master cylinder before, but they are pretty simple and I figured that if I had a blown seal or the like on the primary, and I fucked up servicing it I'd be in the same boat of needing a new one, so I popped off the snap ring and tapped the plunger out along with the first stage.



Pretty damn schmooy.

Cleaned it up, popped it in, and it bled instantly. I figured that the reservoir feed port was clogged with some goop, so it was finally able to suck in fluid from the res. Easy once it works!

With everything bled decently, and completely flushed with VERY fresh brake fluid (thank you 2L of ATE type 200...), the brake feel was MASSIVELY improved, and based on my math it should be pretty perfect to work cohesively with the whole system.

Moved the car out and drove it up and down the driveway (more stuff is loose I need to wrap up before test drive), but the brakes work and feel phenomenal. Blasted the engine bay down to get the copious amounts of brake fluid out of every crevice, and now that it's off the lift I can finish up a bunch of little stuff.

So far, so happy!

 

only if converted to a manual braking system to eliminate the internal ABD proportional braking software function assigned to the ABS module.

Because it would otherwise compensate the braking bias to do just as it’s programmed to do.
.

 

Flocked Dash

Had some issues late last season with glare, and I've always wanted an excuse to give this a try. Really, the excuse was just wanting to live out my WRC car interior dreams, so to say I did this because of glare is a pretty large, but not entirely unfounded stretch. I figured this car was the perfect candidate for a flocked dash, and I wanted to do it on a car I didn't care too much in order to learn how to do it nicely.

When I was researching, the right way to do this is with an electrostatic gun... which I considered fabbing up.. but in the end I just wanted a quick single day project. I used a kit from Flock It, which seems to be the goto. I should have grabbed a small paint roller as the brush they give you is really not made for large objects like the dashboard. The flock applicator in the kit was fine enough for the job.

Pulled some stuff apart, taped some stuff up, slapped lacquer on it, and sent small bits all over the place. Looking back, I would have had a friend help apply the lacquer as part of the way through applying the lacquer I was worried about it drying up and sorta globbed some on and rushed the process. I did also miss some spots, but all in all am happy with the results. I'd say overall it's a 4/10 job, and the passenger airbag cover will definitely need to get redone but is quite a low priority. I'd also like to do the top of the cluster piece, but again was really just rushing through the job and didn't want to mask it off. Your outcome is always pretty proportional to the effort level haha.

 

Hi friends! Haven't updated this in a while because work and life got crazy, including working on this car to prep. Updating a bunch here this morning...

Things not worth mentioning in standalone posts:

-Resealed the oil pan
-Swapped the ebay G35 MC with a new one, old one actually blew out (and was likely already busted) the outer seal and dumped brake fluid into the booster
-Swapped to a new (used) booster
-Swapped out the brake line check valve as it was coated in brake fluid
-New leading and trailing spark plugs, slight misfire at 6k RPM no load resolved

 

Fuel Surge Tank Round 3

So, up to this point, I basically hated every modification I ever did with the fuel system, as it just made everything in tank not work. The root cause was that I was trying to stuff too much **** into one side of the tank sender, mainly caused by the fact there would no longer be a high pressure source to drive the siphon valve. If I could run a STOCK sender in tank with a nicely placed return line, in theory all of my problems would be solved.

The other issue was the placement. I threw the surge tank there in order to use minimal line and make things less prone to errors and to also make it quick. Adding a surge tank in between events last year was not the right move. I decided to do it right and throw it in the trunk this time while I was digging everything out.

This was the diagram I ended up using in order to map everything out, and the biggest change from before was that the siphon valve was going to be used externally. This was something I didn't really see done much, though it is pretty common for siphon lines on older saddle tanks (really, just Subarus... that's where the idea stemmed from) to go up and over the tank.. so I figured what would it matter if the valve was outside of the tank too!



So, off we went. I dropped the tank hoping I would have enough room to get at everything, and also planned to get rid of the pressure check stuff and charcoal canister while I was in there. More on that later...

Should also note, all photos may have some stuff out of sequence, or random parts thrown on the tank just to keep a sealed enough tank full of fuel covered up. 20 year old me wouldn't have cared, 30 year old me is way more scared of fuel tanks.. ugh.. age and mortality...



The idea was simple on the siphon side. Drill hole, add AN fitting, route line from the suction piece to the AN fitting. Easy. Before I did this, I ran some line a couple feet higher than the tank was sitting, and blew into the siphon valve to see if it would actually have the ability to move fluid much higher than the stock system could. Even with just my mouth, fluid was easily siphoned up so I continued on with project. I was really hoping that wouldn't have any issues, as the lack of suction would have been a show stopper.



I then weighed back and fourth between using an S1 or S2 sender as the lift pump. It wouldn't actually matter what I used.. but because I had already done some work with the S2 sender in place, and the clearance for fittings under the access panel was better, I chose to buy a new (used) S2 sender to use as the lift pump.

I did try to do it proper and buy a regulator block off from Fab9Tuning... but they decided to not get back to me after placing the order for a month. Only after sending them a "hello..." email did I get the response saying the parts weren't stocked and I could spend more money on some DeatschWerks something or other that wasn't at all relevant, so I just left the stock regulator in. The pressure should literally never get that high anyways.

I made sure to also drill the return line hole in a place where, once compressed, the line wouldn't hit anything to cause an uneven mating surface with the tank... the whole root issue of the last setup. Not shown in the photo is the Radium duckbill valve I ended up putting on the fitting end.




With that sorted, It was time to run some fuel lines. I chose to run them out and alongside the fuel filler as I knew I'd have clearance without hitting anything. On the passenger side, it was a bit tougher to clear the body of the car and it was smushed a bit more than I wanted... but that just means it wouldn't rub anything, right?!

The idea was to have all the lines run outside of the car, and then come up into the trunk into a serviceable bulkhead. It was at this point I realized I needed to get rid of all the charcoal canister stuff, and that the subframe needed to come out for proper access to clean everything up. No worries.

Random "we went to the track and broke a trans on the K Miata break!"

I was meant to be at the Gridlife event at Gingerman that weekend, but chose to not go as I knew the car would either: Leak fuel, and/or not have a safe fuel setup. So this work was all happening in parallel to a trans swap as well!



Okay, back to RX8s.

I mocked up kind of how I wanted everything to sit, and came up with this basic plan. The bolted in bulkhead was a tad smaller than I'd have liked, but all things said and done, it's perfectly fine. The biggest thing I wanted was access to the bottom side connections with the subframe in car, and it meets that criteria.



I'll spare everyone the agonizing pain of trying to get the right fittings and the right lengths, and having to completely change plans when one thing is sorted... but all you need to know is that for a week and a half, every 2 days I had an order into Summit Racing to get one or two more or different fittings in order to get everything sorted. This was the (mostly) end result.






For the fuel tank vent, I ended up putting all of the stock pressure measurement components back in, and used the stock vent with the purge line populated as it would, just bypassing the charcoal canister. I cut off the OEM 5/8 or so hose, and popped on some Subaru fuel hose I had laying around inline with a T. It worked out awesome, but I did have to kind of ziptie it up a bit higher than pictured to clear the diff once the rear subframe was back in. Not a huge deal, just will likely need to be serviced at some point in 5 years.

I should also note, I did away with the inline filter to the rail, as the in tank filter is now back in place. I kind of didn't like this, but in term of simplicity.. it is the right choice and there are multiple socks on multiple pumps to clean things up.

For wiring, I just made an inline extender from the existing harness to bridge the 2-3ft gap in cable, and used the same color wire as existing. Clean! I also added a 1/8 NPT port (blocked off currently) to add in a fuel pressure sensor to one of my boards to throw fuel pressure on CAN, because why not. Will swap a connector to run wiring for that, and have a bulkhead wiring connector plan coming later.

Things I am happy with:
-Line routing, tidied it up past that photo and with the subframe in everything hugs existing lines and has plenty of strain relief
-Bulkhead connections are easily accessed and labeled until the first time something leaks and melts the electrical tape (lol)
-Surge tank is well secured and plumbing is about as tight as I could get

Things I am not happy with:
-When rivnutting the bolt pattern for the bulhead, sheet metal got bent and now all the holes don't line up, 2/4 ain't too bad though
-Bulkhead is a little bit small
-Siphon fittings are a little bit janky and "not square"
-Diff clearance to purge lines is not ideal

The last task in all of this was getting some sort of "firewall". I use quotes, because it's more of a splash shield than a firewall.. mostly because doing it properly would require covering up the existing deck holes for the OEM speakers and amp. I did not do this, though I am planning to at least put in some cut metal block off plates at some point. The splash guard I did make was using some spare alumalite I had from the first splitter I made for the car. I attached it to the rear seat mounts to get a flat plane using rivnuts, and then drilled clearance holes for the mounting bolts. Easily removable if needed in the future!





I do plan to improve on this a bit in the future, but it works great for now as a minimum viable product.

That's all, fuel system works AWESOME, and worked great on the track (more on that in another post) down to ~2% fuel as read in on vehicle CAN at steady state. No leaks at the OEM pump interfaces anymore, and the siphon works fantastically. I would run ~20% fuel at the start of a session without cut until it was literally out of gas. HOT.

 

We put some decals on some cars

 

Gridlife Midwest Festival - Gingerman Raceway - June 6-9 , 2024

Heyoooo Midwest Fest. The best long track weekend ever has come around once again. These are getting significantly easier to write about as we all get better at the process of loading up tons of cars full of stuff and going racing. We had a crew of 4 cars (on track) and a few more support trucks/cars in our group this year, and the goal for me was simple. Test out new brakes, go faster than anything related to a 1:45 around this track. I had been locked in on that time since even before building the RX-8, so I REALLY wanted to get through that barrier. The other goal was to help my buddy in the K Miata get the engine dialed in a bit better, and bring him down in time. He had a shakedown at Gingerman two weeks prior, and we had a bunch of work to do to get the car 100%.

Everyone loaded up at my place early on Thursday morning, and while I'd love to apologize to the neighbors, I am pretty sure they get excited seeing cool cars too.





Got to the track, created home base, and that was that. Standard issue track things.

Because this was a festival event, we were running a festival competition style, which means we had 4 practice sessions that set the grid order for the first of 3 qualifying sessions. Times would only count towards competition in the qualifiers, with the top 5 going into a sprint session. I already knew I wasn't going to be in the top 5, but like I had mentioned my goals were totally abstracted from the competition itself.

The first practice session I went out and got a whole new feel for the car. The new brakes were FANTASTIC, and I was overbraking everywhere trying to dial back in my foot. Because I knew I was going to be slower, I also tried a few new things like not downshifting in spots, or trying 5th gear on the straight... it was a REALLY great session to just knock off cobwebs from the winter, and force myself into doing something different. For the first time in a long time, I felt like I had made some progress. The best time of the first session out was a 1:45.1... which was a PB by half a second. Boy howdy... I could work with that.

I was running tires from last season during this first session because I assumed I'd be way slower than anticipated. I had a new set of brand new tires I decided to swap on to for the next practice session of the day. My friend also said to stop braking and hucking the car into T2, and to just let the momentum of the car carry me though. My buddy in the Miata was doing this, and while in the last session I was overall faster than him, he had like a second on my because of that one turn. Message received.

After looking at some more data and determining is was NOT worth it to use 5th gear on the straight, and there was no point in downshifting into T7 if I just kept the momentum up and stopped using the brakes so much.

(Previous PB of a 1:45.6 and my first practice PB)


In the next session I went out for the next session and ran a 1:44.0. Turns out, there was a second in T2... good call! And with the new brakes a bit more understood, I could modulate them so much better to achieve more braking performance that ultimately led to more braking force without nose diving the **** out of the car and losing all the turn in grip that was required in such a low powered car. I was still overbraking a bit, but that's a limit I will forever creep up on instead of overdoing and backing off.

Track went cold at 8pm and the evening was spent eating awesome food made by my friend, and dialing in a really terrible open loop VE table on my buddy's K Miata. At the previous event his open loop fueling was running ~16:1 AFR at anything over 6800 RPM.. ooof. We also spent some time looking at data and talking about goals. We both had the goal of being in the 44s, with a stretch goal of being in the 42s for the weekend. I can't recall if he made it into the 44s at this point, but he was really fighting the engine not making any power.



9AM was the next morning's practice. I had cold tire pressures dialed in perfect, and the weather was about as good as it could ever be. This was going to be the last "good" session, as the drift cars and rabble rousers were going to be on track to kick off the weekend's festivalness and kick all sorts of marbles and dirt up on the track. In this session I battled a lot of traffic in the way, and not appropriately spacing myself out from cars. Typical time attack issues of a 450hp street car completely leaving you in the dust in the fast bits, only to be completely in the way on the twisties. In the fray, I was able to do a 1:43.9 while knowing there was a hell of a lot more time in there as on the hotlap the car giving me a bit of a tow down the back straight decided they needed to pit, and me souly being focused on "DO NOT MESS UP THIS LAP" going into T11, hit the brakes extremely early inline with the car pitting. No biggie, I was stocked with being in the 43!

Next up were the fun taxi sessions where we get to send TA/Drift/GLTC cars all out on track at the same with, with passengers! I love these sessions so much for the obvious reason of being able to share the fun we have with tons of people. I took a few people in our group out for rides who had never been on a track before, and it's just so awesome to watch someone experience that for the first time. 11/10 as always.

Last practice session of the day as just after lunch. It was a bit hotter out, the track had a lot of **** all of over, so I went out not really expecting much. I also still had some of that traffic in front of my on grid as we weren't running by class in the practice sessions, so I did what I called "turning off engineer brain" to stop pre-analyzing what the could COULD do with a given set of inputs, and just drove the snot out of it and reacted to what it WAS doing. Turns out, it's the right way to go about these things. I ran a 1:43.6 with ease with 3 other laps in that session being within .2 seconds. The car had a hell of a lot more in it, and I even messed up some turns and got held up (just a little) on that hot lap. After 3 years of scratching my head wondering how a 42 in this car was EVER possible, it finally seemed in reach and without a hail mary. Such great fun.

Practice was over, and it was time for the qualifiers and the actual competition to start. 5PM was the first session and I had a great position on grid with friend's both in front and behind me. I think it's really important to befriend those folks on the grid near you, it allows you to push each other further, and really not feel like you're in someone's way, or someone else is in your way. Team sport!

While sitting on grid waiting for the Sundae Cup cars to finish their session, I had an ABS light pop up on my dash. Huh. Well that's odd. I knew this would disable EBD and of course the ABS , so I tried a power cyle while on grid, but the ABS fault was still present. I figured I'd just deal with it on track, continuing the theme of turning my engineer brain off. As we were released I went in and did a brake check on the outside of the blend line in T2 and all felt pretty okay. The pedal was definitely not the same, but I could work through it. Go into T3 on the outlap, and just full lockup. I tried to modulate the brakes but no dice, and just went straight off. Looking back at the video what I could have done to keep on track was waaaay more obvious, but I think even with the failure the car would have been pretty undriveable even if I didn't fall of the track. It is funny to see myself turn the wheel after the fact as it's damn obvious that was never going to do anything, but that's the difference of being able to analyze without an impeding patch of grass coming up. I let everyone pass me by and took it easy enough and pitted out. The wheelspeed and GPS position data tells the story pretty well, haha!

(LF wheelspeed scaling is incorrect, so the number is wrong but the graph shape is the more important bit)



I pulled the car in and we checked for flatspots.. they didn't seem too too bad (more on this later... they were), and I ran the code to try to get start at what the issue was. FYI: If you run the car like an 02 Ford Focus, you can get ABS codes on most readers. Yay Ford braking parts!



I tried to hook up to the internet to see what the code meant in the service manual, and had 0 dice getting data. With thousands of people in the area this was always the case at festival. I assumed the pressure sensor was toast, but really needed more info to debug any further. Until then, I was scrubbing any other qualifying sessions. I decided to call my dad as cell phone service still existed, and asked him if he was in front of a computer. I had him look the code up in the service manual and this was the entry:

C1290: The pressure from the brake fluid pressure sensor when not braking exceeds specification

This still led me down the path that the sensor was broken, and I had new one sitting on a table in my garage. Of course. We checked all of the wiring to the sensor and unit, and it was all fine. I hooked up my tactrix and looked at the pressure data, which was reading totally fine. Hrm. I cleared the fault and wasn't able to get it to pop back up after some driving around the paddock, but this wasn't the confidence I needed to run the car on track with a potential failure at actual race pace. I decided to eat some dinner and drinks some beers and stew on what the issue was. I didn't think the pressure sensor was toast, I don't think it was because of heat that things went out of whack, and it wasn't until later it clicked. The brake switch. This is a tomorrow morning problem now.

I had adjusted the pedal a bit with the new MC and had just set the brake switch so that the lights weren't always on. I pulled up brake unit data again, and pinky toed the pedal. I was able to see MC pressure without the brake switch reading, and set the fault I had seen before immediately. Pressure in the system had in fact been detected without the module seeing that it was supposed to be braking. I clicked back the brake switch adjustment two clicks, popped it back in, and was no longer able to see MC pressure without the brake switch being pressed. Badass.

At this point I had missed the morning qualifier, so I went out for a test drive on Phoenix road to determine if my fix was vetted. Side note, I have no idea if the track or if the road was the right place to test this failure out or not... but it seemed slightly more moral to test on the street knowing what the failure mode was. All went well, so I had regained a bunch of confidence I had lost when you dance yourself off the track. I also didn't feel like the flat spots were too bad, and that I could drive through them. This would turn out to be a terrible choice after actually getting a good look at the tires, but these are things you learn the hard way sometimes.

I was able to grid up for the last qualifier after a chat with race control to get my name on the list. Since I didn't make a lap in the first quali, it was basically like I didn't even show up. My brain was back in engineer mode and with the tires vibrating like crazy, the best I was able to manage was a 1:44.4. A bit disappointing given the success I had in practice, but these are the struggles we all go through. I am sure I was not, am not, and will not be in the future the only person fighting a vehicle issue battle at these events. As disappointing as it was, I was all in all extremely happy with that time and was able to at least beat the few guys I had been on the grid next to the whole weekend. And hey! The car was fixed! That's a 10/10 issue debug if you ask me.

I ended up swapping the front tires back to the older ones for the taxi sessions he had left, and the grip the car had before the ABS failure was back. Live and learn.

Photo of one of the front tires back at home. Hindsight is a bitch, right?



I decided to party it up and call it a weekend even with one more session for us on Sunday morning. Being able to drop 2 seconds in a weekend and debug an issue with the car was all the satisfaction I needed. The fuel system worked flawlessly by the way, only to be bested by me literally not running enough gas in the car early on in the weekend, but being able to not cut any fuel (or leak any) down to 1% of tank read gas is awesome.

While trying to collect some thoughts after the fact, I wasn't exactly sure where the speed had come from. The only thing I did over the winter were the brakes, and 2 seconds to drop just driving is quite a lot. I think a lot of what I was able to do came from running the car at Lime Rock last year, a track where you are FORCED to use the momentum of the car to gain speed. I was able to limit drive the car a lot faster at that track, which I think gave me the confidence and knowledge that the car would be able to handing the extra speed I was giving it. Looking at previous lap data and videos, I am just faster all over the place and it makes sense to me that being forced to limit grip the car at faster speeds leads you to have much more grip confidence at lower speeds. Driving at new tracks is seriously the best way to hone driver skill. I am convinced.

We were also able to get my buddy's K Miata into the 43s as well, which was a 3 second improvement from 2 weeks ago. That's a hell of a weekend if you ask me.

Here are the results (holy hell 30 cars in class!):



Video of my fastest lap:

And of course, some badass photos:

 

Good job on the PBs and hopefully you can sort the abs nonsense out. It seems a lot of rx8 racers have gone to the way side of deleting DSC or starting with a non dsc chassis. Do you have a baseline time at this track before you did all the track mods?

 

I did a 1:48.31 with a relatively stock car with brake pads, tires, and coilovers in 2020, so I’m super happy with that progression.

I think the ABS issues are sorted, and going to a non DSC unit doesn’t really gain me much even though it would be the right starting point. With DSC disabled it’s basically the same unit. I don’t know what kind of EBD the sumitomo unit does, but I’m happy with the Bosch stuff currently. The fault it had was 100% my fault, not the unit.

 

Awesome!

Yeah, everybody I know who tracks/races or autocrosses RX8s is now on the nonDSC ABS unit. They all say it's much improve, not just in avoiding ice mode, but the ABS itself is better tuned. I'd def go that route. Finding the pumps still isn't crazy. Finding the mating harness is harder, but it's easy enough to just connect discrete wires with contacts to the mating pins on the pump and then pot it. On the other ends of the wires use any other type of connector like a Superseal or circular MIL, etc and use that to disconnect the pump from the harness.

 

it absolutely is not.

another member here ordered what we believe to be the non-ABS connector, but didn’t confirm to me if it was or not after it was ordered. Let me check on that.
.

 

Gridlife Circuit Legends- Lime Rock Park - August 16-17 , 2024

Headed back to what's starting to take over as my favorite event of the year 10 hours east at Lime Rock Park. This year, I was able to convince more friends to come, and our caravan and group was fantastic. We decided to rent a 34ft trailer and throw on two cars to make life a bit easier, and the trailer was so awesome we are going to be using it more.

We loaded up late Wednesday night ready for a 7am departure, and hoping for a 7pm arrival at the track.





I think part of what makes this event easy to do while being so far away is that the drive is really quite beautiful as you get through Ohio and into the mountains. Us flat state folks can only be jealous. My good buddy with a Track Mod Impreza decided to sell his driver's ticket, and instead brought along a few cameras to take some AMAZING shots throughout the weekend. I'll sprinkle in some of his photos because they are SERIOUSLY good.




14 hours later we arrived at the track where it was not quite pitch dark, but darker than we had hoped. Still, we beat last years arrival by about 3 hours. This gave us good headroom to get everything setup and actually get some sleep in before the early wakeup to get cars through tech and on track. The only unfortunate mistake we made was one of my friend's left the keys to his Miata sitting at home. DOH. We decided to just yank the column lock and ignition cylinder and run it to some switches. Good thing I brought extra wire!

On my side of the equation we were ready to rock come morning, and my other friend in the K swapped Miata was set to grid right behind me for our first session, perfect for a fast pace follow the leader session while he learned the track.

Morning came, and it was FOGGY. Luckily most of the sun cleared it up before our first session out.


After a few first laps getting back into the swing of things, I ran a 1:01.5, which was a PB by half a second already. Hell yeah, great start to the weekend! The car had INSANE high speed grip, though lots of slow corner understeer. Tire pressures were a little low, so most of day 1 was battling getting the pressures right as we had some big temperature swings. 50/60s in the morning, 90s by 2pm. I ended up swapping to my other set of tires on the front, which seemed to help just a bit. I was running a set of tires on the rear with one event on them, and god knows how many on the front set. I didn't want to buy a pair of tires after I roasted the two front new ones at Midwest due to lockup, and I think this ultimately gave the car a bit less balance than it wanted.

Times got slower throughout the day as the temperature increased, which is somewhat expected as this car REALLY struggles to make power at anything > 85 degF ambient. On out laps all the K swaps were just running away from me on the straights. I think it's also worth a note that this AEM intake does absolutely fuckall for power/IATs/etc, but the only thing I have noticed is an increase in water temp by about 8 degC. I am going to get rid of it and go back to my stock location piping. The last session of the day was hot, the car was getting hot, and there wasn't much I could do. Tomorrow was going to be cooler, so I just aimed for that.

Track sessions for time attack ended with a bunch of GLTC and other events still on the track, which was awesome because it gave me some time to enjoy the event for the many other things it has to offer. Concourse, drifting, vendors, and just the parking lot was full of amazing cars from all decades of racing.

After the track went cold, we went for a track walk. Walking (scooting) Lime Rock is always such a treat and you can really appreciate the hills and curbs of the place. Bombing down the final corner down the hill on a scooter is loads of fun.




Saturday morning came, and I ran a 1:01.6, back on pace. Then I ran a 1:01.2, and then a 1:01.1. Perfect progression while still dealing with the usual time attack things: traffic, heat, degraded track surface as drift cars and GLTC cars litter the track with marbles. My 1:01.1 was the fastest lap of the weekend, and nearly a 1 second improvement over last year. I ran a pretty gross lap when I got the time, so there's OBVIOUSLY more time in the car as it is. Almost nothing changed as far as car setup from last year, but most the time was gained by not using the brakes in the downhill. 1.8G at 104mph is intoxicating, and also terrifying. The best combo. There is a sub 1 minute in this car if I can get that front end grip back in check. My buddy with the K Miata also in Club TR ran a 1:00.9, so right on pace and ended up throwing a serpentine belt tensioner on the course in the last session. I think there are a few other spots on course where brakes aren't needed, but I am scared haha!

In class we both were solid mid pack, as usual, and the spread of times in the midpack was insanely close. Being 40-60hp down in class, I am more than stoked on this.



Fastest lap video:

Photos:












Off track shenanigans:

 

Totally not worth it own post, but added in a fuel pressure sensor since I had a spare port open on one of my old legacy boards. Yay data!

 

Enjoying your thread.

Coincidentally, I had a similar area of heat damage on my car. Wire wheeled the surface rust off and did the POR15 treatment then applied the heat reflecting material.
https://www.rx8club.com/rx-8-racing-...2/#post4996569


I need to check out your GROM stuff.

 

Good lord this thread is such a wealth of information. Thanks for sharing this and helping us all out dude!

 

Awesome pics, car looks great. What's your curb without driver or ballast looking like these days? You were well under 2700 lbs some time ago and curious how your efforts have played into where it currently sits. I wouldn't be surprised if you've dropped into the 25xx's and would imagine the vehicle feels exceptionally nimble at that weight.

 

Just realized I never did a write up on racing at ABCC at the end of the season. Ugh. Life.

Weight hasn't changed a whole lot since the last time I posted something about it. I do need to throw it on the scales though, and plan to in the spring.

 

HVAC Removal, Harness Reduction and Sensor Addition

Long winter, not a lot of work getting done on the car.. but finally decided to dig into it and clean up some wiring that became useless, and remove components no longer needed, while also adding in sensors that will be used for Flex Fuel (more on that in a below post too).

So, this main driver for all of this work was to condense all of my silly sensors into one spot in the car, as well as add in some additional sensors to use for FlexFuel tuning, and general curiosity. While I was in there I figured I'd yank out wires I wasn't using, delete immobilizer components (yay, made a free patch for immobilizer turning off!), and get rid of the HVAC boxes as they were no longer needed. Pretty simple work.

Reducing the harness was simple, yet kind of annoying. I wasn't expecting the harnesses to be completely potted at the ends where it is weatherproofed, but I guess in reality.. it makes sense. I wanted to pull out a bunch of wires I wasn't using (secondary air, fog lights, etc), and clean up the fuse box. Initally I was going to make my own fuse box, but the amount of work vs the benefit wasn't very favorable, so I ended up just removing circuits from the stock box.







Going through the harnesses again, I managed to remove... not very much, but the cleanup was well worth the time, and I needed to pull everything out to run my new sensor harness anyways. I used a middle revision of my own PCB to essentially pull in tons of sensors and output them via CAN to my display, the stock ECU for flex fuel, as well as add in a secondary bus for additional sensor logging without clogging up the OEM bus. At the end of the day the added sensors in the car are:

-2 EGT sensors, one per rotor housing
-Fuel pressure
-Fuel ethanol content
-Fuel temperature
-Rear differential temperature
-Oil temperature
-Oil pressure
-Wideband lambda, in the rear O2 slot

Alongside this information, as well as reverse engineering the ECU to get more CAN data from the module, I have everything I need for a full logging suite. Only things I will likely add in the future are individual brake pressure sensors.

I also decided to properly calibrate the sensor probes I was using, as well as the OEM OAT sensor with some equipment at my dayjob. I will post that information when I have some time for anyone to use.









I also finally picked up my own welder and popped in the EGT probes here:




And of course I only had to cover up, and reweld a bung once because it hit the engine mount... but it gave me a closer to the front housing measurement anyways.

And of course... my electronics needed some development to be auto grade... new board revision coming soon with PROPER circuitry.. but it'll keep me running for now.



Quick log in the middle of getting everything running!



Retaped up the front harnesses as well, and it's not a big change, but it's nice not having loose **** all over the place:




To cover up the holes, and also cleanly bring in the new sensors into the cabin I decided to prototype some sheet metal cuts with my new laser cutter, and then had them cut out of aluminum with some studs for easy removal. I also decided to cut some gasket material for the new bulkhead, because why not! Seal it up. Engraved the part as well, because why not!

I will upload my designs for use for anyone as 2D vector files. You can easily cut some out of steel if you'd like to weld them in for a more permanent install. I just decided to panel bond the old drain tube plate on.









Putting everything back together was pretty plain and simple. I moved the delayed power box for window operation to just attached on to the dash bar instead of the HVAC box, and got rid of the old Metra stuff running the HVAC controller that I didn't need anymore. I do still plan to run the OAT sensor, just because it's nice to have a "track temp" type indicator, but I am not sure how just yet... and it's such a low priority. I did write some software to be able to talk to the OEM red display.. but that thing is kind of heavy, and it's just not worth the effort right now.

To delete the HVAC controller, I just cut some oversized circles of black acrylic I had as some scrap and epoxied them into the controller holes on the facia. Minus some epoxy spillage, I think it came out great for the amount of effort put into it.

 

G-ROM Flex Fuel ECU Patch

Alrighty, this is the big one and I could drone on for hours about this (and plan to), but I want to keep this relatively short and sweet and will make another thread on it to cover it in depth.

THE SOURCE CODE IS AVAILABLE FOR FREE HERE: https://github.com/equinox311/RX8_FlexFuel
THE LOGGER IS AVAILABLE FOR FREE HERE: https://github.com/equinox311/RX8Defs

I've spent a pretty good chunk of time diving into reverse engineering the OEM ECU, more specifically the S1 USDM 6 port, 6 speed software. Info on that here:https://www.rx8club.com/series-i-eng...-guide-276137/

In doing this, I have also been able to write some other software for the Mazda engine controller to patch in alongside the existing engine control strategy to do flex fuel injection, as dynamic timing addition based on the ethanol content. How I did this is complicated but at the end of the day it's pretty simple. Here is my strategy broken down simply:

-Configure the OEM ECU to read in an additional new CAN message containing fuel ethanol content with some CAN timeouts and failsafing on the signal if the signal were to drop out mid drive
-Sensor gating, stopping the evaluation of flex fuel related metrics over an RPM or a load threshold
-Change the "base fuel ratio" used to by the ECU's current strategy to determine fuel volume from air mass dynamically based on the measured stoich fuel ratio. This calculation is also upstream of primary/secondary injector control, so the logic for turning on secondary injectors should remain unchanged
-Add timing "adder" tables to allow for user calibrated additional timing added to the base timing tables existing from the factory strategy
-Add timing "multiplier" to allow the "adder" table to be scaled in a user calibrated way based on read in ethanol content (read: octane amount)
-New Mode 22 PID handler to allow for all OEM PIDs, as well as ANY user defined PID to be added for CAN logging
-New compiled version of RomRaider ECU logger for use with Tactrix cables to log and view in realtime ANY Mazda ECU data, including additional Flex Fuel related data metrics

That's all that is in my patch currently, however for those seeking a bit more refinement, I do have cranking enrichment tables scaled to ethanol content planned for the future, and it's really just a matter of adding them in the software build. I already have a way to add additional cranking fueling to the cold start strategy.



Right now I have tested it without much engine load, but as the weather is getting nicer here, I'll be driving the car on this strategy and heading to the dyno for a full day of messing about. I've run up to 76% ethanol, and so far down to ~30% ethanol, and the closed loop control of the engine works amazing. Fuel trims stay within reasonable ranges, and lambda tracks properly at higher engine speed open loop.

As I confirm operation of everything, I will clean up the repo and release this patch as something you can add to your ROM, as well as a patcher tool utility to apply to your software if you already have other tuning done to it. The only additional hardware you need is something to provide the OEM ECU a CAN message. The CAN spec the patch requires will be posted up, and it's also in the source code. I do also plan to sell cheap GM ethanol sensor to CAN converters specifically for this patch for those wanting a simple solution... but that will take some time to get out the door, so don't expect anything super soon if this post has you super jazzed.

Also, if you want to collaborate.. please send me a PM! I'm just an idiot bumbling my way around engine control!

 

Kinda just dumping this inline of my other post since it really doesn't need it's own filing.

Flex Fuel Dyno daaaay! My buddy works at a place with a dyno. Buddy got us on the dyno. It's good to have good buddies.

We spent more time dialing in my buddy's K Miata, but I got the RX8 on there my with flex fuel patch to see if I could eek out that extra 10hp. The last time I dyno'd the car was in 2023 which is made 187hp/132ft-lbs. I got my tank of gas as high in ethanol as I could to run out my current calibration as close to 100% timing adders. I think, realistically, it would have run at 100% timing, but the ethanol blend I could get was only 65% or so.

Tossed it on the dyno and did 3 runs, and I called everything operational and needed to learn more to do anymore tuning.










It made 208hp/144ft-lbs which is a solid 20hp pickup since the last 2 years. I am STOKED about that.

It was moreso a confirmation day, than a day of tuning (my car at least), so there are many improvements to be made, but I am happy base lining what I have at the track. The fueling could be quite a bit leaned up to gain some more power but, I'd like to see the effect on EGT and other system temperatures. To me, dumping a ton of heat in the system and not being able to to more than a single hotlap isn't worth a 10hp gain when I have plenty of other areas to make up time, and would rather have the seat time in a working car. In order to understand the effect, I am going to baseline what I know works now, and start going from there. I think there's plenty more power to be made, and plenty more to learn.

 

Loving the content on this build thread! I've read it multiple times since you started. As a GLTC competitor myself, I have a pipe-dream of running my RX8 in it, instead of my Kmiata. But I just don't think a renesis could get the job done to stay mid-pack for w2w, different from time-attack of course.

I read back on your last mention of the coilovers. Did you ever change them? The car looks a tad pushy.

 

My intent is to run it in GLTC, as soon as I can get some time to get it built to spec. I definitely do agree with that assessment though.

I have some new suspension that's not going to be here in time for Midwest, but yeah.. the rates are not ideal and it does push juuuust a touch. This should fix it a bit, but this year I am running an engine program and not a suspension program haha.

 

Gridlife Midwest Festival - Gingerman Raceway - June 5-8 , 2025

Heyoooooo Midwest fest time!

As always, this is such a good event and typically the first of my season. I came into this event with a car that made a bunch more power than years prior, and a bunch of only barely proven out software and hardware on the car (that I made myself), so while I was expecting to go much faster, there were still many IFs that needed to get proven out.

To give some more perspective: I had only run the FlexFuel software for a few pulls on the dyno, and maybe 10 miles of street driving. While everything seemed to work perfectly, it still didn't have much drive time.. and a known software issue with some old sensor hardware I had made. The bug was essentially a sensor misread, and would report much higher ethanol content than in actuality, but only for a blip. This was due to some hardware limitations with REALLY old hardware I was using in the car, and I had really put in a ton of low pass filtering on both my sender, and on the Mazda ECU in order to damp this issue. Because of the misreported ethanol content, it could potentially cause the ECM to inject TOO MUCH fuel. Also to be clear, this bug is completely resolved in newer hardware I have, but I did not have a chance to get it into the car, so we were going to find out if my ECM filtering was enough to combat this known bug.

To make matters a tiny bit worse off, I had a set of new suspension that I had ordered back in April, though due to some delays on parts, they weren't set to ship out until after this event. I was really wishing this wasn't the case, but we will run we we brung.

We decided to load up quite early this year and to prep everything beforehand, that way getting into the track was as simple as possible.. this lead to what I think was the first group loadup that finished before the sun went down. The group of us had 3 cars running, and as it would turn out... we all ran extremely close to each other.



Once at the track, the paddock spots were few and far between, more so than years prior, and we had a bit of a rough start trying to secure some spots that were advantageous for easy parking and working on the cars. Either way, we were there and ready for practice sessions.




The first practice session out I had almost a full tank of E85 (read: 70% ethanol) as I wanted to understand the fuel consumption increase with the ethanol, as well as a fresh set of RT660+ tires. We all gridded up together and off we went.

The first straight away between turns 2-3 were perfect, car definitely had more power than it ever has had before, and turn in to 3 was quick and grippy off the hop. As soon as I got back on throttle for turn 3 exit.. instant misfire and no torque. Uh oh. This was accompanied by an ungodly amount of smoke out the exhaust completely smoke screening my friends on the first session outlap. I figured this was it, this is how this motor ends up going out. I limped it around T4-7 and it was still misfiring at partial throttle. I was just hoping I could limp it into the pits and not get a tow back. At this point in time I really had no idea if it was a mechanical issue, a fueling issue, or some other software related issue that was causing the engine to not operate correctly.

Down the back straight I decided to give it some gas and see what it was going to do, and to my surprise it seemed to clear up and be totally fine. Against likely better judgement, I decided to not pit in and go for another lap to see if it was going to be fine. As it would turn out, everything was totally fine after the initial smoke show and I managed to run a 1:42.35, a PB by a full second.While I was EXTREMELY happy with that result, there was no doubt that I had lost some confidence in the car and that wouldn't be resolved until I could figure out what caused the smoke show.

I pulled logs from the car, and began to investigate. What I had noticed was EGT in one rotor had gone down ~120 degC from the other, and my lambda was pegged rich. Okay cool, we had a spark based misfire in one rotor. That could be due to many things, but I wasn't sure why there was a smoke screen.




I decided to pull spark plugs and have a look. Rotor 1 leading definitely had some buildup on it compared to other plugs, but otherwise looked okay. I then pulled the MAF just to see if oil had been tossed into the intake. The MAF was COVERED in oil, so I had found the cause of the misfire, but no idea why it puked up so much oil.

I had likely overfilled the oil due to being on a steep incline in the paddock, after I had also drained the oil coolers at home to swap thermostats. I had run into misfires before due to oil overfilling, but never to this extent. Noted.

With some confidence gained back in the car knowing my issue was totally self inflicted and temporary, I went back out for another practice session that evening. I didn't run any faster, but was consistently at pace around the same times as my fastest of last year and the car had 0 issues.

As the sun went down, we all looked at data and started a fire. Everyone was already running faster than last year, so it was shaping up to be a hell of a weekend.




Woke up early, ate some healthy breakfast, and got ready to start our first timed sessions. Car did a 1:42.282, so a bit faster than in practice the day before. I definitely could feel a lot more time in it, and also after a few cans of E85 went through, noticed the ethanol content really wasn't going above 70%. This makes sense as it's likely about the max you're going to get from pumps. I decided that I would increase my timing multiplier a bit, which equates to ~1.5 degrees more of timing. I wasn't super concerned about knock, but I figured I'd be able to see it in data if it was past MBT, or knocking. I don't really have great data to read about knock on the engine, but I can look at EGT and long G/straight acceleration to see if power was decreased. I dunno!




In the afternoon sessions, the car was definitely a bit up in power, turns out a adding timing helps, however the track was too messy and greasy to go faster. I once again was running consistent and under my best time from last year, so I took that as a very good win. Also, the FlexFuel software was working flawlessly, which was another huge win.

Pulled pork and macaroni on the grille was for dinner, and man it was tasty. We decide to wonder around the race track after the sun went down, and to very much so from a distance check out the music festival, which was now based on "spectator hill" overlooking the entire venue. While I don't care for the festival music, It was a neat experience being able to be a viewer from turn 3 and 7, and able to heard the crowd from the entire track as we went around.



Morning came all too quickly, and we knew that this morning session was going to be the last of the fast ones. That's sort of how it goes at these events. This year though, they did start blowing off the race track during some time period, which actually did make for the CLEANEST track I've ever had at a Midwest Festival. Dealing with drift debris and touring car marbles was always part of the challenge, and while I enjoyed it, I did also enjoy a bit fresher of a track every morning.

Geared up for this morning session and I ran a 1:41.740. Unfortunately, there was a bit of confusion because the timing beacons had apparently dropped out, and I was one of the unlucky drivers to have passed by the start/finish line during this outtage. Luckily, talking to race control, they already had my number down as a car that went by, and they took my AIM data in as official. Big props to the Gridlife people, as they are so understanding and easy to work with. I also ran this time with a biiiit of traffic, and messing up T10 and T11, so I knew there was more time in it.. but I wasn't sure the track would allow it was the day went on.

My thoughts would turn out to be correct, as I was 2-3 seconds off pace on the later, hotter, messier track sessions. All in all, once again, FlexFuel was working flawlessly, and my friends were right on pace too with a few fixes to some Miata brake lines, and diagnosing MR2 fuel starvation issues, so everything was just a huge win.

The only other exciting thing during the day on Saturday was that during the Taxi sessions (passenger rides and all types of cars on track for fun), I started to develop a knocking sound from the FL corner. I kept going out, giving people their first track experience, but it kept getting worse. Pulled it in, and my buddy had let me know my brake caliper was hanging on by a single bolt.

OPE.

We got the tire off, checked everything, and off someone went to the Autozone for a new bolt and locktite. It was fixed up before the next session, and all was well. I am still not entirely sure how the bolt backed up, and the other bolt was loose, but seeing as the other side was completely tight, I had to chalk it up to me not tightning everything down during the winter, and missing those bolts on my checklist. I think I'll only do that once.

After the last TA session, we parked the cars for the night, and then decided to party it up like it was actually Midwest Festival.

So, general recap:
-FlexFuel is badass, car was probably making 215-218whp once I turned timing up.
-RT660+ tires seem to like to run hot, though wear quite quick. Not sure if they have more grip, but definitely more heat tolerance. I do expect them to heat cycle out though
-Optimized suspension would be extremely beneficial, there were some bumps and weight shifts I could use some better suspension characteristics to be able to go faster

I ended up 12/26 in class (will update once class based results are easy to find), which is pretty good considering if I ran .5 seconds faster, I would have jumped up 5 places. Really tight racing.

Best Lap:

Best lap was caught on the livestream as well!

Photos:








Bonus! My buddy had a few of his film cameras with him, and got some really greats shots that I really enjoy:

 

"we've seen him plenty of times" lol

pretty cool to be spotted as a regular by the commentators. Congrats on the event, looked like a great time.

 

Couple few mods I did after Midwest Fest that aren't super important to document:

-Spacers and splitter rod adjustment, noticed the splitter was tending towards a bit of an underbite at speed in photos causing a lack of front grip at higher speeds. Added some spacers and loaded the rods downward. Plan to do quite a bit more work on a new splitter soon.
-Fender liner holes. In an attempt to get some more front grip, I cut out the fender liners, and removed the rest to promote airflow through the fender vents. Seemed to help a smidge, but it's all witchcraft without proper testing and analysis. I am planning to do more with this, I just need the time to properly design stuff.
-Foam around the radiator, standard issue for RX-8s,I just never replaced it when I did the radiator swap
-OEM Caliper bolts went on the one that had fallen out, not that the other bolt wouldn't have worked I just hate having 7 different bolt head sizes on one part of the car