TeamRX8

iTrader: (25)

the 18 x 9.5 +45 RPF1 is not so much of an issue. With the std RacingBrake 2-pc kit you only need a 7 or 8mm spacer. With their Enkei offset BBK you don't need any spacer as the kit was designed specifically for this wheel by offsetting the rotor and caliper further inboard

it's the 17" Enkei wheels that have brake caliper clearance issues on the RX-8

Modified Dave

Thanks guys, this is all really useful feedback. I appreciate it.

Those Enkei RC-T4 rims are super sexy. Sounds like in a 9.5'' wide rim even the RPF1's may work, depending on how the brake kit is designed. Wish the new PF01's came in a 17x9.5 or x10, but gotta step up to 18'' for those widths. Anyway, no hurry on selecting wheels since I'll probably run the 18x9'' wheels I have on the car for the better part of this season anyway.

On the subject of wheel width, you're always going to get better tire performance from a wider rim, or at least that's proven to be the case in my own testing. For example, going from a 17x8'' to a 17x9'' rim with 235/40R17 Toyo R888s on a Lexus IS300 World Challenge/CTCC Touring Car we saw significant improvements in tire wear, driving characteristics, and grip and I also found the same to be true when going from a 15x7'' to a 15x8'' on my Honda Civic racecar with 225/45R15s. Weight I've found to be less critical, though with a low torque engine like the Renesis wheel weight is going to be more important than it is with most cars.

Highway8, I'll have to check your thread again for updates on your cooling setup. I am thinking about going to a one big oil cooler setup so I can run a secondary radiator on the other side, or I may look at a custom V-mount setup once I go FI to see if I can generate enough cooling from a single high efficiency rad and some big honkin' pusher fans. I've "stacked" coolers in front of each other in the central location before (rad at the back, oil cooler in the middle, and intercooler out front) and the results were not good. As a fluid dynamics engineer later showed me, you need a surprisingly large air gap between the coolers so that airflow doesn't get pressurized/backed up and on most 'sport compact' type vehicles there just isn't enough real estate to get the required spacing. The 8 has quite a bit of space to work with though, so I am hoping your stacked approach (if you go that route) works out. I'll be watching your thread for updates!

I'm all about front grip, so I'll definitely fab up a custom splitter for the 8 like I did for my racecar. For the Civic I used a high density foam core wrapped in an inner layer of carbon and an outer layer of Kevlar (for better puncture and skid characteristics), but the 8 isn't going door bashing so I think I'll stick with 2 layers of carbon since the Kevlar is a bit of a PITA to work with. Here's some pics of my Civic splitter with chassis mounts:








The DJ Racecar/Wing Shop rear wing I have uses a moderate profile with respect to downforce, but it's also very low drag, so could be a good option for the 8 (ran this same wing on the turbocharged Scion tC I drove at the 25 Hour race in '06-'08 and it worked extremely well...got us down into the 1:58's when we were in the 2-minute flat range without it). Here's a little data on the wing (mine's the 183 single element):




I've seen the CFD simulations for the Kognition wing (10'' cord) and it's definitely a more aggressive wing than the DJ one I have, but if I get power up into the 350+ range then it starts to make sense (when matched with a front splitter, of course).

Ok, the wife is telling me to eat dinner now

Modified Dave

A couple more thoughts re: cooling.

Just flipping thru the new issue of Racecar Engineering and there's an interesting story on cooling and how F1 and IndyCar cores are tested and developed. Very high tech stuff, obviously, but the story mentions Mezzo Technologies and how their Dallara IndyCar radiators contain over five miles of 0.5mm bore pipework (which reminds me of Eric Meyer's comment about the C&R rads he uses in his RX-8s and how they have a lot more internal mileage). Since Highway8 has been doing some NASCAR oil cooler shopping on eBay, I wonder if maybe some IndyCar shopping for one of these Mezzo rads is worth exploring?

The other thing that comes to mind is adding a Laminova heat exchanger to the oil and water systems. Here's a little story I did on them for Modified a few years back, JIC you're not familiar with the technology:

http://www.modified.com/tech/modp-09...ger/index.html

Has anyone here tried a Laminova heat exchanger on a boosted RX-8?

9krpmrx8

iTrader: (46)

Funny you mention those, Hoss-05 and I looked into those when I was doing my single oil cooler conversion and they are great from everything I read but my 28" Fluidyne NASCAR cooler was just so much cheaper. Those Laminova coolers are expensive but awesome.

I looked into several different types of inline coolers but could never settle on one.

TeamRX8

iTrader: (25)

not so fast ...

Modified Dave

I can't sneak anything by you, eh Team? LOL. Yeah, I think you're right that this is the "rub" when it comes to heat exchanges and the Renesis (and probably rotaries in general). They make so much heat on both the oil and water sides that the benefits of a heat exchanger are probably lost. Normally they're used when you have extra cooling capacity on the water side and can therefore use them as an oil cooler, when it seems like water temp is actually the bigger battle when boosting a Renesis. Back to the drawing board...

9krpmrx8, where did you source your 28'' NASCAR oil cooler? eBay? How much do these things go for? I take it you bought a used one from a NASCAR team? Is this the same cooler Highway8 is using and fits well in the OE location and with the MS front bumper and cooler ducts? Do you guys use the OE lines or do you need to run custom lines to them (and speaking of, are you going to a larger dia. line for greater flow/capacity?). Time for me to go revisit Highway8's thread, huh...

Found this little tidbit on Mezzo radiators. Going to have to see if I can find out what the dimensions are of these IndyCar rads. Will post up any info I dig up.

http://www.indianapolismotorspeedway...hwitzer-award/

Actually, does anyone know the exact dimensions of the RX-8 radiator? I'd like to send specs to Mezzo to see about the cost of having them make me one that fits like OE.

9krpmrx8

iTrader: (46)

Dave, here is my thread on the subject.

https://www.rx8club.com/showthread.p...gle+oil+cooler

I paid like $100.00-$150.00 for it on ebay, it was off a Nascar. It goes for $600.00 new but you can find them fairly easily in different sizes. I used Taylor pushlock hose and fittings from a local hydraulic shop. It has been almost two years, no problems so far and cools great.

For my turbo build I am also using a water/air inter-cooler so that I don't have to move the oil cooler from the front crash bar. I will have a secondary radiator in one of the factory oil cooler locations and the radiator for my water/air inter-cooler in the other stock oil cooler location.

Keeping oil temps down is no issue with this cooler even with my higher oil pressure, but for me, keeping coolant temps down has been an issue so rather than bucking out for an expensive radiator, i will just use a secondary one.

Highway8

iTrader: (11)

The renesis is its own Heat Exchanger, no reason to add another one.

For the fluidyne oil cooler, just do an ebay search for fluidyne oil cooler and plenty of used coolers will come up. Type in nascar oil cooler and you will get even more options with different brands.

The 28" stacked unit does not fit in the OE location with any bumper. The 28" unit does fit under in the front grill opening under the crash bar but blocking the radiator, but thats not the prefered location and becomes very difficult to put it there with a FMIC. Which is why I had to do a custom crash bar, or you can just turn the stock crash bar upside down and modify the plastic grill. The single unit I am using in the OE location is a DB 30416 measuring 14 3/4" x 6 1/4" x 2 3/4"

For Cooler lines, I believe the stock lines are 10AN, but the coolers are 12AN, so I ran new 10AN lines to my oil thermostat and 12AN to the cooler.

TeamRX8

iTrader: (25)

ps: is that a splitter or a battering ram, lol ...

Modified Dave

Hah. Needs to be a bit of both when you go Touring Car racing. Only weighs 7 lbs though and is way more durable than the typical plywood or alumalite approaches. That being said, I may go with alumalite for the RX-8's splitter since it's so much cheaper and way less labor intensive compared to a composite one (plus I don't plan on bump drafting anyone in the 8).

A water/air intercooler is an interesting approach. I know FXMD went with a water/air intercooler on their 700+whp Time Attack NSX because of the unique challenges associated with a mid-engine car with very little frontage and a lot of space constraints in the side duct areas, but I think your idea of running one in an OE oil cooler location and a secondary rad in the other spot is an intriguing approach (along with that huge center mounted oil cooler). Hmmm, definitely some food for thought!

What about water/meth injection? Are any of the FI guys here running it to cool combustion and protect against detonation? Or running e85 for a similar effect?

9krpmrx8

iTrader: (46)

The 28" unit does make it a bit difficult to mount a large FMIC which is why I am going with a water/air unit. Also, a bigger inter-cooler is not always needed either, at least not for me anyway. But the Fluidyne oil cooler I have does not affect the radiator as far as I can tell, my coolant temps and oil temps are inline with each other most of the time.

It should also be noted that my max oil pressure increased with just the single oil cooler conversion alone.

Highway8

iTrader: (11)

Water/meth is not needed IMHO. If you were running 20 pounds of boost and the AIT were 100 deg over ambiant I would suggest it, but with 10-12LBS and a good intercooler your AIT will be fine. Several FI guys were tracking their car and sing Water/meth but have sense gone away from it. The key with FI is running a rich tune but more aggressive timing . It prevents Detonation, still makes power and keeps you EGT's low. High EGT will weaken your side seal springs and cause your motor to loose compression or blow early. Ths is true with both NA and FI motors.

My splitter is made from Alumalite and weighs a whole 3.6lbs not counting the chassis mount which is being changed right now along with the underpanel.

scorcherjf

Hey Dave,

Any updates? Been following your articles since I got my car last year and they've been awesome reads, lots of information both here and on the website.

Especially interested in your lap time progression since I frequent the same track and can actually have a baseline of what a good driver can do compared to my sloppyness =)

Anyway, my most recent day at cayuga was netting me low 1:27's to high 1:26's with my stock RX8 with 225 RE-11's. I was wondering if you think I should go for wheels/tires first or a decent set of coilovers?

On a side note... are you the same "Dave Pratt" that did the autoguide reviews for the BRZ and FR-S? The article showed that the BRZ got a 1:26.5 and the FR-S a 1:26.2 at Cayuga... those are some nice times for those prius tires!

Modified Dave

Sorry it's been so long since I've updated this thread. Fatherhood has been owning me. I don't even know where to start in terms of an update on the 8. How about I address your questions in reverse order since I'm dyslexic?

Yes, I am the same Dave Pratte (they left the e off the end of my name in one of those videos in a weak attempt to Anglicize it) for the AutoGuide videos. I'm a freelancer, so although Modified keeps me busy, I do a little work on the side for outlets including AutoGuide, Autoblog, and MotoIQ.

Your lap time on 225 RE-11's on stock wheels is very solid. Clearly you're not as sloppy as your wife may have been telling you Seriously though, I think I did mid 1:25's when I upgraded to 18x9 wheels and 265/35R18 RE-11's on an otherwise stock RX-8 and it sounds like if you did the same you wouldn't be fair behind at all (making you, quite possibly, the second fastest RX-8 driver in the world!).

But to answer your question, nothing improves grip and handling more than a tire upgrade, though you aren't going to see the same huge jump given that you're already running on an extreme performance summer tire, just in a size that's too narrow for maximum grip. I think 255's or 265's are a good fit for stock (or near stock) power levels -- you can still steer the car with the throttle, but grip in and out of the corners is much improved with wider rubber, so you can attack corner entry with less understeer and put the power down sooner coming out of corners and with less oversteer. Do it! Do it!

Suspension is definitely the next best bang-for-the-buck mod in terms of lowering lap times. Shoot me an email at planetdave "at" me.com if you want to discuss this. Too big a topic to cover here.

In terms of lap time progression in my RX-8, after the engine rebuild lap times dropped about 1-second into the low 1:23's and high 1:22's. I haven't actually had the car on a dyno yet since we're only about halfway thru the tuning process (been street tuning it using MazdaManiac's remote calibration service), but I'd guess it's currently making between 210-220whp. Not quite as much as I was hoping for, but the extra jam has definitely brought the car to life. It's a lot more fun at this power level and would be better still with, um, another 50-100-hp

Here's the engine build story:

2008 Mazda RX-8 - Building A Better Renesis - Project RX-8 - Modified Magazine

Currently the fastest she's gone is a 1:19.1 around TMP (Toronto Motorsports Park, the most popular track in the region for testing and Time Attack events), just a couple of weeks ago while testing BFG new R1S race rubber. Actually, here's a little video I threw together from that day. FYI the exhaust sound is thanks to a recently installed Pettit Racing/Milltek after-cat exhaust along with the extra revs of the new engine.


These are the new soft compound version of their R1 DOT race tire, but based on the grip it has it's really nothing like the original R1 -- it's like a Hoosier A6 or Hankook Z214 soft compound but with even more turn-in precision. I was blown away but how precisely I could position the car on these tires and how early I could get on the gas because of the huge grip level.

http://www.flickr.com/photos/77534829@N03/7850565264/http://www.flickr.com/photos/77534829@N03/7850565264/ by http://www.flickr.com/people/77534829@N03/, on Flickr

Mounted these up on TSW Interlagos RF 18x9 +32 wheels, which I'm super impressed by. A forged wheel (very strong and only weighs 18.3 lbs) that only costs $1k for the set? Mind = blown!

http://www.flickr.com/photos/77534829@N03/7850571480/http://www.flickr.com/photos/77534829@N03/7850571480/ by http://www.flickr.com/people/77534829@N03/, on Flickr

http://www.flickr.com/photos/77534829@N03/7850595612/http://www.flickr.com/photos/77534829@N03/7850595612/ by http://www.flickr.com/people/77534829@N03/, on Flickr

http://www.flickr.com/photos/77534829@N03/7850588550/http://www.flickr.com/photos/77534829@N03/7850588550/ by http://www.flickr.com/people/77534829@N03/, on Flickr

Here's a bit of data comparing the BFG R1S to the RE-11 street tires (blue line is speed on the BFGs, black line is speed on the RE-11, green line is lateral g's on the BFGs, red line is lateral g's on the RE-11). As you can see the BFGs allowed for much higher cornering speeds and produced a lot more lateral grip (as you'd expect), but interestingly I wasn't slowing with much more efficiency. You'd expect the blue speed line to drop more sharply on the BFGs given their superior grip, but I was into ABS so quickly that I wasn't able to use all of the tires grip while braking. I think a brake pad upgrade is in order, and I may try pulling the ABS fuse too to see if that helps.

http://www.flickr.com/photos/77534829@N03/7551148196/http://www.flickr.com/photos/77534829@N03/7551148196/ by http://www.flickr.com/people/77534829@N03/, on Flickr

Last weekend I also competed in the CSCS Time Attack at TMP, where I ran on a fresh set of Hankook TD soft compound (C70) semi-slicks so that I was legal for Super Street (or Limited) class. Managed a 1:20.7 (good for 11th fastest overall and 3rd in class, behind a race prepped Z06 and E90 M3...damn V8s! LOL) but I think I left a half-second on the table. I spent most of the day struggling to get the car's handling balance sorted out, since the Hankooks introduced a bunch of understeer. Started by checking tire temps and pressures after each session and adjusting the pressures to try to get some rotation, and then added a click of compression stiffness to the rear of the car with the Moton Clubsport dampers.

This dialled out the understeer, but during the official TA session the car was a bit too loose, so it felt like I left some time out there. Anyway, still a very respectable lap time for a treaded semi-slick tire, though I was a bit surprised they weren't closer to the BFG R1S given all the internet hype about the Hankooks. Don't get me wrong, it's a great tire and definitely class leading for a 80 UTQG semi-slick, but not quite as close to a non-treaded 40 UTQG offering (like the BFGs or Hoosiers) as some other reviewers might lead you to believe.

http://www.flickr.com/photos/77534829@N03/7820075260/http://www.flickr.com/photos/77534829@N03/7820075260/ by http://www.flickr.com/people/77534829@N03/, on Flickr

http://www.flickr.com/photos/77534829@N03/7850760918/http://www.flickr.com/photos/77534829@N03/7850760918/ by http://www.flickr.com/people/77534829@N03/, on Flickr

http://www.flickr.com/photos/77534829@N03/7850761552/http://www.flickr.com/photos/77534829@N03/7850761552/ by http://www.flickr.com/people/77534829@N03/, on Flickr

Hope this answers your questions. I should get back to work here, but I'll post some more details about the engine build and other aspects of the car's progression over the weekend if I get a chance.

pdxhak

iTrader: (2)

Thanks for the update Hard to believe those are 245s because they look really wide! How do they wear on the track?

Modified Dave

Tire manufacturers always cheat on the width of there race tires. These 245s were pretty much the same width as the 265 street tires. I could have gone with 265s but the hard R1 is slow to build heat so I decided to try a narrower tire for faster heat buildup. Turns out the R1S has no trouble heating up fast, so next time I'll try them in a 265 or 275. But I loved the car's balance on the 245, and being a bit smaller in diameter also helps gearing/acceleration so this smaller setup may actually prove to be the faster option. Hmmm, I think I smell a tech story for the mag here!

Oh, in terms of longevity, not sure how long the R1S lasts. I only had time to do a couple 3 lap sessions on them. Will be interesting to see how many heat cycles they take before I start to see a drop off in lap times.

I put 4 heat cycles on the Hankook TD and about 20 laps and they wore very little and showed no signs of slowing down.

TeamRX8

iTrader: (25)

You have Motons and adjustable swaybars, but are using tire pressure to adjust balance?

scorcherjf

Wow nice post, thanks for the reply. I'm afraid I can't compare my times to yours since mine is an R3 so the gearing alone should make it faster than the S1, I still stand by my sloppyness statement, lol.

Would it be okay if I shot you an email with a youtube video of some of my laps so you could point out some places I'm losing time? I'm still wondering what I should do in regards to suspension so I'd like to pick your brain a bit if it's okay... haha.

I'm still amazed you pulled a 1:26.2 with a stock FR-S on prius tires!

Modified Dave

Just Motons, still running the stock sway bars (though I often disconnect the rear bar). I will be putting an adjustable front bar on the car though. It's on the To-Do List.

In terms of tire adjustments, let me clarify -- I set them up to run in their optimum temp range so that they're making the maximum mechanical grip possible, ideally with about 10 degrees more temp on the inner third though that's not always possible given the camber limitations I have on this car and the way this track heavily loads the front left tire.

Once I get tire temps where I want them, I focus on handling balance which can include adjustments to a whole bunch of variables including damper settings, wheel alignment and tire pressures as well as driving style. Even small changes in pressure can have a big effect on both temp and handling, as I'm sure you know, but on this particular day track temps were quite mild so I had more room to play with pressures before getting into a scenario where the tires were overheating. So I was able to play with rear tire pressures quite a bit to get the car to rotate while still keeping the tire in the right temp range and leaving the rear dampers at relatively soft settings so that it squats and puts the power down more effectively (plus TMP is a bumpy track with lots of curbs that need to be used for a fast lap, so a soft setup is needed).

Anyway, the process of getting the tire temps where I want them is always intertwined with any adjustments being made to handling balance, since changes to handling balance affect tire temp and changes in tire pressure (and thus temp) affect handling balance. And then there are changing track conditions and temps, tire degradation, and the lunar cycles to consider...

scorcherjf, sure man shoot me an e-mail any time you want. I'll be at CSCS in Sept, so if you want to come for a ride in my 8, stop by. I'll also be at TMP on Sept 17th testing the Boss 302 vs the Evo X and then on the 24th testing the Mustang V6 Track Pack vs the Hyundai Genesis 3.8 R-Spec (both tests for AutoGuide).

I really was pretty shocked by the FR-S's lap times. There's no way it should be that fast based on its power:weight ratio, but this is a very special car. It achieves cornering speeds and lat g's that I would have though impossible on those crappy little all-season tires, but its so well balanced that it defies what's possible on low grip rubber. It's such a special car in the turns, it makes just about every other car I've tried feel like an understeering pig. If I didn't already have the 8, I'd have a FR-S in the garage right now.

FazdaRX_8

iTrader: (1)

any updates with this build?

really curious how the engine is holding up, and why there are no more published "rx8 project" stuff in the magazine

Lvis

what size tire are those? (on first page)

nice choice in rims

TIM33H

Great thread Dave!
I just finished reading it from start to finish.

Just sad to read this as your last paragraph

Modified Dave

Haha, the FR-S is a pretty special little car, but for less than half the money you can buy a used RX-8 and have just as much fun, so don't get me wrong, I'm not in a hurry to trade the 8 in on a Toybaru. But maybe the 8 will have gone as far as I can take it as a project next year, at which point maybe the BRZ STi is out. Who knows. I don't get to keep my cars forever, given the line of work I'm in.

Still lots more to come with the RX-8 though. Just prepping it for boost now, including some Inconel heat shields from Turbosource, some fresh engine mounts and longer ignition wires (so we can relocate the coils) from BHR, a big *** rad from Ron Davis, bigger injectors from ID, etc. We're going to start with a Pettit Racing kit I bought used from a local RX-8 racer (Gary Wood), but I may change it out for a turbo setup over the winter to really max this motor out as fully as possible.

Updates and stories in the mag have slowed lately because my wife and I just had our second son, so it's been tough to find time to wrench on the 8. But lots more coming over the next 6 months. I'll try to post some pics between diaper changes.

Lvis, the tires on the first page are 265/35R18.

FazdaRX_8: we've been PMing, but the built motor is holding together great. Time to stress it with some boost

TeamRX8

iTrader: (25)

a 245/40-18 is taller than a 265/35-18

try a 245/40-17 tire & wheel setup instead