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That’s what the new modular Adaptronic ecu is, but you don’t need a cable throttle because it already has a DBW module built in with the factory settings, which are also adjustable. I think there’d be a lot less monkeying around with it, but it sounds like your mind was already made up before discussing it.
I'm just comfortable with the Megasquirt and support is excellent. And I'm a luddite and hate DBW
JV, start an SM specific thread and then we can all post about our future hopes and dreams and help you brainstorm on your build, while still letting us play around in the much cheaper world of SP ;p
PS - the RX8 has the best DBW system I've experienced. Only ONE TIME has it ever been an issue, and I think the car was just pissed off since our codriver revved her up at the prosolo line to 8,000 rpm way too far in advance (probably 10 seconds before the lights dropped), and she said "F-U" and dropped revs to idle right as the lights dropped to launch LOL.
JV, start an SM specific thread and then we can all post about our future hopes and dreams and help you brainstorm on your build, while still letting us play around in the much cheaper world of SP ;p
I think Sipe already made one for him and then deleted it.
Still not quite in the final intended form yet, but can be run as-is if need be. I did finally figure how to get the #1 rotor front pipe in/out without removing the engine mount bracket; patience is a virtue. Have another Renesis-specific manifold mod idea up my sleeve that I’ve never seen anyone else do before
Revamping the muffler/sound attenuation on the rest of the exhaust system now. Not anything we haven’t already seen or know about, but a further variation of the application of it to keep flow high with low restriction yet meet the sound regulations. Will post it up when ready.
Broke a stud off in the trunk where the upper rear shock tower reinforcement brace bolts to the inner trunk wall. No way to access the back side of it. Thinking to cut it down even to the metal panel and seeing if I can find someone with a stud welder that can align and zap one in for me. Ugh ...
Hoping to start on the cooling fan and radiator shrouding this weekend. If it goes according to plan it will be different than anything else I’ve seen in an RX8. Will also be designing and routing new oil cooler lines to accommodate the changes.
I have a spare S2 trans listed in the FS area and may be taking out the one in the car too. With the new SP drivetrain strengthening allowances I’m looking at possibly trying to modify the S1 trans to be strong enough for my abuse since I have five of them (broken) sitting around. I much prefer the S1 gearing ratios, especially if 3rd gear ever comes into play.
Revamping the muffler/sound attenuation on the rest of the exhaust system now. Not anything we haven’t already seen or know about, but a further variation of the application of it to keep flow high with low restriction yet meet the sound regulations. Will post it up when ready.
Broke a stud off in the trunk where the upper rear shock tower reinforcement brace bolts to the inner trunk wall. No way to access the back side of it. Thinking to cut it down even to the metal panel and seeing if I can find someone with a stud welder that can align and zap one in for me. Ugh ...
Hoping to start on the cooling fan and radiator shrouding this weekend. If it goes according to plan it will be different than anything else I’ve seen in an RX8. Will also be designing and routing new oil cooler lines to accommodate the changes.
I have a spare S2 trans listed in the FS area and may be taking out the one in the car too. With the new SP drivetrain strengthening allowances I’m looking at possibly trying to modify the S1 trans to be strong enough for my abuse since I have five of them (broken) sitting around. I much prefer the S1 gearing ratios, especially if 3rd gear ever comes into play.
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The header looks amazing! I hope you see some pickups from it after all of that work. Our LT header only showed around 5 wheel torque in the midrange and a tiny bit peak HP increase, but I think the peak pickup was simply better tuning (EFI Logics). The RX8 is definitely a hard one to find power with.
I'm not even going to ask how you broke that stud.... but that SUCKS.
On the S1 vs S2 transmission, there isn't much of a difference in gearing. 2nd gear is about .5mph different (.5 not 5). 1st gear is a bit shorter on the S2 trans. I don't know about 3rd since we've only had to shift once LOL. The main benefit is the stronger second gear. The diff is where the big gearing change comes from. We are still running the S1 R&P since we decided the S2 R&P would put our gearing too short.... / we don't want to shift.
More a personal preference. My feeling now is the S1 trans with S2 rear gear is the way to go WRT my overall setup strategy. I also have an identical S1 rear diff/lsd setup just in case this doesn’t pan out, long fast course vs short windy, etc.
Not expecting any power from the header over my original race manifold. It’s slightly heavier in the current form too. My other manifold was too restricted for heat expansion and even with T321 high temp material it’s finally fatigued out. The “only” reason I built this tubular header and the way it’s built is to allow full freedom for heat expansion and long life.
No surprise you saw a power bump though because of what you were using previously. My position has always been max flow is the only Renesis exhaust benefit. There is a point where bigger accomplishes nothing useful, but there is no downside to bigger because there is no scavenging potential with an engine that has no port timing overlap. All you can do is get it out with as much freedom and lack of restriction as possible and then manage it the same to the exit point. On a Renesis all the harmonic tuning is in the intake system. The Renesis is a naturally aspirated mild-supercharger design in the general sense.
Trans/Diff combos based on a 24.9” dia tire, pro’s and con’s to all and assessing the differences is usually more difficult than people realize; the actual acceleration differences, where those occur relative to speed and track position of the comparison vehicles because it’ll be different for both, etc.
I went ahead and threw in the Motorsport gear for the track people (S2 trans/5.125 gear seems best, S1 trans/S2 gear would be next best if you can get it to survive.)
I can’t argue against the S2/S1 trans/diff making sense. The lower 1st gear helps it out of the hole almost equivalent to the S1/S2 (Pro Solo drag start only) and can carry a few more mph before the shift. Whether the S1/S2 trans/diff can make up for that by accelerating quicker, especially in 2nd gear out of slower turns, and getting to higher speeds in less time, is hard to put down on paper. You can see how the 2/3 shift drop is quite a bit larger for the S2/S1, would want to be avoided, and is a poor choice for an early shift; it has the potential to drop off the APV valve even with a 9k shift.
If the S1/S2 car is going faster at the same track position when it needs to make the 2/3 shift around 60 mph than when the S2/S1 car gets to that identical spot though, and being in the powerband can then have the room to carry it forward enough to be worthwhile, it could have potential if the downshifts can be managed. The S1/S2 acceleration potential in 3rd gear is also greater too (2x more than 2nd gear over the S2/S1 if it has to use 3rd), even with an early shift since 8600-8800 rpm shift point for durability is preferred. Some S2ks and certain other cars do it successfully. There is a 2nd gear acceleration advantage for the S1/S2 though, but the lower top 2nd gear speed is the payback. It’s the main gear we use so that makes it hard for me to ignore without making the effort to find out.
Well, if it works, you'll know when you start winning .
Not sure if I agree that going for 3rd is the best answer, but it will help against the more powerful cars in DSP; at least until you have to grab third.
You focus on 3rd too much, how much time accelerating on course is above 62 mph on average?
Lately, quite a bit. We hit limiter nearly every even this year topping out at 67. Not enough to need to shift (1-2 sec max), but if you hit limiter at 62 you would need to shift probably. Courses have been getting faster.
Ok, well I’ll always have the option of a rear swap or shift. I intend to cover the bases and adjust.
Try to remember that I was running the 245/30-17 Toyo R1R back in STX which was only 23.7” diameter. I used 3rd a lot to my advantage at a few events and made it work, but could overrev too if needed.
You have to start somewhere though ... just my reasoning, nothing more. I don’t hear anyone saying they did it both ways and decided xxx ....
You have to start somewhere though ... just my reasoning, nothing more. I don’t hear anyone saying they did it both ways and decided xxx ....
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No argument there. I haven't gotten to play with this variable yet, but from experience I particularly liked that 2nd was long, especially for a car that could hit mid 60s on a wide open enough autocross course.
My codriver told me at one of the local Devens events he went to, he was on the limiter for an entire slalom, which is one of those cases where I'd rather not shift. So, either shift earlier and lose the acceleration, or keep it in 2nd and try to ride the limiter.
Ideally, I'd like to shift early (about where the 5.125 would put 2nd) and keep it in third for the fast parts of the course. This works pretty well for the stock class cars that are geared that way, but it does add a bit of complication to the run.
Like anything in engineering, each approach has its own compromise. Choose the compromise you can live with, I'd say.
In that situation I agree 100% that it’s easier to drive it that way, but what if 3rd and technique is faster even if prone to occasional mistake and botching the run? Will my car slalom better than yours or not, better aero force use or not, and so on. Haven’t been out on the circuit for the last 4 years so my lack of what’s current there may be skewing me in the wrong direction. Building the car with specific goals to try and favor rpm acceleration where ever possible though; low weight, low inertia, etc..
If I can only only get part way up a course ahead of the next fastest car, but not maintain or improve upon that, then it would definitely be a two steps back reality. On the otherhand, if it were to improve enough to make 3rd a useable choice that could be a two step ahead situation.
I doubt that will be the case, but even if it’s just incremently get ahead & maintain then it favors being slightly faster overall for improved odds of coming out on top. Or not.
I understand the mechanics of why the car handles differently in 3rd, but it doesn't change the fact that it is an added level of difficulty. What I have found is that a car that is consistently easy to drive, wins more consistently, so we have been aiming to get my car to that level. We aren't there yet - still making too many changes since we are early in development. However, having driven the Davis' CSP car for two seasons, I know what the end goal is - because that car is forgiving to drive, inspires confidence, and is fast enough to take top index at nats repeatedly. One day we will get there with my RX8, I hope.
Also, we enjoy having friends codrive the car with us, and if it frequently required a shift to 3rd, that would also increase the chance of a money shift to 1st. Our clutch is already hard enough for people to drive (the disengagement point is much lower than a stock clutch, and apparently some people don't push their foot all the way to the floor before shifting), so if we also feared a money shift I don't think we would let people drive the car. That's no fun.
My rule of thumb is I want to be able to go 65mph in 2nd gear at a minimum. That's our preference though.... if a course doesn't require going much over 62mph OR if a driver is very skilled at shifting and familiar with 3rd gear handling and somehow magically reduces the time it takes to shift to next to nothing, the S2 R&P should be faster due to the improved acceleration.
The ultimate combo would probably be the S2 R&P and a greatly increased rev limiter so you can stay in 2nd and still go 65mph+. We haven't wanted to push the engine that hard though. We already rev to 9,300.
That’s ok. It wouldn’t be the first time I ended up with egg on my face
It’s all just blah-blah-blah until the pedal hits the metal. A forum is just a place to share and compare ideas.
Based on some of our personal discussions on overall setup philosophy, that trans/rear choice, etc. I can see your car being just as you say in 3rd gear. It makes sense to me. Not trying to say you’re wrong either. I apologize if the way my ideas are expressed might imply such a thing. I don’t mean it that way at all.
I didn't take it that way at all - no worries. I agree, it may work. I think on a slower course, having the S2 R&P will always be beneficial. I think if a course requires shifting, it becomes a mix of pros and cons.
Either way, get your car finished - we are all excited to see you out
Well there’s a reason I’m posting theory more than applying it recently. I’ve pretty much not told anyone other than my immediate family and coworkers being unsure of where the situation might be going, didn’t want anyone to treat me differently than usual (I know some of you wish I’d just die, it’s ok ), etc. In early October I was diganosed with throat cancer and am currently about half way through a 7 week radiation and chemo treatment regime.
My life is still fairly normal otherwise without any impact on my job and getting by with the essentials. Fortunately I work from home and am not getting out much except for the necessary life stuff; shopping, and such. Things are going about as good as can be expected and there’s a 98% chance of full recovery and never deal with it again result. I really want to be working on the car more and finishing it because it’s not really that far off from being done. All the things I have to do right now relative to the situation makes getting over there difficult right now. If all goes well I should be recovered and fully back to myself in February.
Damn, Mark, sorry to hear that. I hope everything trends towards the better with your health.
I'll agree with Tamra that courses have been getting faster, the first couple of years in Lincoln we had some pretty tight courses with lots of speed changes, but the last couple of years (and basically every year at the Pro Finale) we've had these big speed-maintenance courses. I've gone taller in rear gear every year since 2015, and haven't regretted it at all (and still had to go to third on the west course this year, only at the finish). The BMW doesn't slalom nearly as well as the RX-8 and should generate less steady state grip so if I'm running out of gear with a 67MPH second gear I'd think an RX-8 would want to be able to go at least that fast.
A couple years ago (2015) I wrote a Matlab script that analyzed all of my SoloStorm data from every course from that year to select the rear end ratio. Using the thrust at any given speed for any given rear-end ratio and the amount of time I'm WOT on every element on every course, it ended up telling me I needed to be way taller than I was at the time. Again, I haven't regretted it.
12-02-2017, 12:13 PM
Have another Renesis-specific manifold mod idea up my sleeve that I’ve never seen anyone else do before 
