hi guys,

i'll be popping a 20b single turbo into my rx8 at mazsport. my car's already there!

i have a few questions for the 20b owners.

i have 285/35/19 rear right now. do you guys think that's wide enough for ~600whp? once i'm over 50mph, i want to be able to go full boosted throttle without any worry of loosing the rear end in the dry condition. drag slicks for 19" are pretty hard to come by, so any input would be appreciated.

i also wanted to ask whether anyone has installed 4port stoptech in both front & rear. i have 4 port in the front right now and that's been working beautifully, but i noticed that there's lot more braking grip left in the rear tires (front locks up first during hard braking). most important thing would be the balance during trail braking.. i'm actually thinking of moving the 4 port to the back & installing 6 or 8 port in the front. i wanted to ask for your opinion. most rx8 discussions are about improving the power, so i wanted to ask this question here.

thanks all.

 

While I don't have personal experience with those power levels, I recall talking with Peter Farrel's techs after he had built and tested The Black Car (the 3rd gen featured in the Car and Driver Supertuner Shootout). It had 285/40/17 tires on the rear, IIRC, and they gleeful recounted the car "doglegging" down I-66 when Peter gave it the boot.

I have about 2/3 the horsepower and mere 275s on the rear. My car will break the rear tires loose at 60 mph in fourth gear at a little over half-throttle, but it will continue to go straight. That's the best info I can offer. On the highway (where I'm paying attention to speed), I rarely go WOT, since it causes all those cars in front of me to rapidly accelerate in reverse.

On the track, where I can go WOT more safely, I don't pay attention to the speed.

 

The other 20B in our shop is 600+ and breaks the tires all the way through 4th gear at 115mph. It can not hook up anywhere and has drag radials on. He is going to have to go back and go with a different axle, ect. So no I do not think that rear will get it done.

 

thanks for the info.

may i ask what differential gear ratio you're using in the back? and your wheel size? i have 19"s and will be installing a 3.9, so i hope that it'll hook a little better at freeway speeds. i won't be racing on the freeway, but rather would like to avoid smoking my tires out unintentionally when accelerating on an onramp or loosing my rearend at a slight moment of concentration lapse on a curve...

but why is it that when i see videos of supra pulls from 60-150mph with 600-900whp, it seems like they're hooking just fine? is it their suspension geometry and heavier weight? well anything helps. i guess i can always turn down the boost accordingly.

any input on the brake upgrades?

 

What size and kind of tires are on the car?

 

Theres a few videos out there showing those high HP supras leaving twin rubber marks when they put the hammer down while going highway speeds. My guess is that when they hook and go like you've seen they aren't jamming the pedal to the floor and they are using a bit more control.

I believe there is also an aftermarket traction control system available too. I forget what the name is but I've seen it discussed on this board before. Might be something to consider for a high hp streetcar.

 

Race Logic TC.
Lots of Supra guys run it I guess.

 

mickey thompson drag radial 275s

 

I will be putting 335/30/18's on mine but Ive seen a 20b FD get completely sideways on the freeway while the driver was just trying to pass @ 80mph

 

It always cracks me up when people say they want to make 750-1000 rwhp with these cars. That's around the same HP Dee makes with his 8 sec drag car and it's not exactly easy to keep it pointed straight with drag slicks. IMO 600+rwhp is not that useful on street tires without 4wd unless you're interested in doing 120-160mph pulls. At lower speeds (with more mechanical leverage in lower gears) it would probably be more scary than fun. Also, if you get nailed by the law at 100+ the chances are you will be dealing with more than a mere speeding ticket.

There was a great article in the June issue of Motor Trend comparing a bunch of 600+ hp modded cars. They were struggling for traction below 120mph with 335+ tires that were larger in diameter than anything that could be put on an FD without hacking to the nth degree.

Traction control is one solution, but think about what it's doing -reducing hp. It has limitations. I know Racelogic claims something like 30% slip control, which most of the people I have talked to think is a bit unrealistic. Ignition retard alone is not going to be enough. Progressive ignition will be necessary to really drop power. Reducing the hp by turning the boost down would probably be more effective, feel smoother, and be better for the motor.

So what does all this mean? Personally I think I would be more than happy with 500-550rwhp. Everything over that is probably worth trading for better throttle response and a broader powerband.

 

Maybe, maybe not. If we are talking about the same Dee (reactive racing?), he tuned Tommy's car. Tommy will find a way to get it to hook, his whole goal was to make it run 8s, low 9s with a street car, which Dee and Jim at JPR think is fully possible. Though it is not for everyone...and not the faint of heart. When he first tried to get it down the track, he got partly sideways at 110, and broke traction at every gear resulting in a low 12s run. So, now back to the drawing board to get it to hook. Once he does, 8s-low 9s it is....

 

i won't be driving around with full boost. for street driving, i plan to just use the wastegate pressure, whatever it may be... i'm guessing it won't make more than 350whp with just the wastegate.

but at times, i would want to use the 600whp... such as when i'm up against a viper on a track. and on those days, if i forget to turn the boost back down for the return journey home, i don't want to end in a ditch or even worse a tree.

bottomline is... if i can foresee any problem that may arise and can install something now to avoid it, whatever it may be... i would want to get it. kinda like a roll cage. i hope it never happens, but u can't predict everything in life. i live some things to chance, but driving a 600whp car on a public road isn't one of those things...

 

That is the biggest thing I yell at tommy about, a lack of roll cage. Safety is first priority...and with that power, even a great driver could see a ditch or tree being careful...

 

mirabile, i think i would leave the suspension more or less stock. this won't be a drag car; that's why. i think with 600whp, the car'll do 10-11seconds comfortably with some drags, and that'll be enough for me.

not really looking to blow pass the 1/4 mi mark at over 160mph

reason for the 20b was mostly for the useable torque it'll deliver on a technical track. i'm still learning and still debating whether to install a widebody on the rx8 or not... it won't be a cheap option, so i'm still quite hesitant. if going 335+ in the rear would eliminate any potential problem, i would think it'll be worth it, but it doesn't look like that'll be the solution here for controlling 600whp. am i correct?

 

I would. My rear is re-done with cusco LSD and hardened axles. I would deff go widebody, if you look in my thread up in the 3rd gen section you will see I did. my rears are 13 wide each now...

 

mirabile, do you know anyone who would do a custom widebody on an rx8 near west penn? near tampa is fine too.

thanks.

 

Of course. How custom? Making a kit is probably beyond the skill set, but if you pick up the pieces, like fenders, ect, they would deff be able to fab it up for you. My shop is right outside Philly. You have to give them the time they need though...Just let me know if I can help.

 

nothing too crazy. just fender extensions that'll blend in with the car. there's one kit out by r-magic for ~$5500 with shipping included. but that's for an entire face-lift. i just have no clue as to how much a job like this will cost.

i guess i'll start looking for used hre's on ebay

i'd prefer the shop to have pretty decent experience with the custom body work... to avoid the drama that david had to go thru..

do you know mazsport in tampa? my car's over there, so anything close by over there would work as well. i don't like how pettit does it imho. it sorta looks like a patch work.

 

The 20B is very unique engine, more so than many people/shops realize. If this is a road race/ track day car, your going to run into some issues with it being turbo. Mostly with heat. A built non-turbo converted 20b like mine is my personal preference with a track car. What made you want 600rwhp? Are you used to 500rwhp already? Just seems like alot of power for a production baised Rx-8 on a road course. Good luck with the build, say hi to Louis for me.

 

nah 600whp is strech for me. last most powerful car i took to a track with a reasonably good confidence had about ~320whp. i plan on turning up the boost gradually. probably start out with wastegate at around 350whp then go from there.

why 600whp? i really don't have any good answer then again, why do we live? it's highly philosophical

i was debating on non-turbo myself, but there's a particular rush from a turbo tune that my m3 could never deliver, which i had sold to fund this project. anyhoo, i think i'm spending more money keeping it on the road then on power, so hopefully i'm on the right track.

thanks for looking out.

is there any good shop that can fab me a widebody near ohio/penn border u know of?

 

this is a dumb question, but could someone confirm that 'bump steering' is the kind of pseudo-steering you get when you hit a little bump on one front tire?

how's that affected by modifying the steering rack for instance, when you're installing a 20b? i should mention i have an rx8. hoepfully the steering rack will remain untouched during the 20b install, but in either case, i am curious nonetheless.

in simple terms... thanks. couldn't find any satisfactory explanation on the web and on the forum.

oh and how heavier are the 20b over the renesis? 20b with manifold vs. renesis with manifold. if renesis info is unavail here, 20b vs 13b comparison will also be okay.

i've been hearing anything from 20b being 300lbs heavier than a 13b which makes no sense to me, to 20-30lbs heavier, in which case, battery relocation should bring the balance right back. thanks all.

 

Bump steer is caused by the suspension arms, and the steering tie-rods not following the same arc, or should I say same pivot point. Which then as the suspension is going through its movement, the tires will have toe-in and toe-out. So like you said, you hit a bump, and it may make the car point in one way or the other, even though the steering wheel is straight.

If you move a steering rack at all, even 1/2" it will change the pivot points in relation to the stock suspension. So if the rack is moved lower, then a bump-steer correction kit is needed, which baiscally lowers the tie-rods the same amount on the knuckles. The real problem arises when the rack is droped over 1" and you car is lowered more than 1". Now you have 2" to space out on the knuckle, and welding/ brackets ect are needed and wheels wont fit ect ect, its all down hill. I looked at a few Rx-8's without engines, and performing the swap and keeping the stock rack in the stock place is going to be more than challenging. I am one of the few guys that keep the stock rack in stock location on the 20B FD, and it looked alot harder to do in the SE3P.

A turbo 20B, single turbo, and a custom intake setup like yours , will be in the 440-450lbs range. A stock Renesis is about 295lbs with everything. So your picking up about 145-155lbs at least. Making your weight balance est. 53/47% front/rear. That is with it shoved way back in there. Hope that helps you out a little!

 

hey that was really helpful. thank you.

they're installing a dry-sump system on my 20b, so hopefully they can fit it in without much issue. it'll also be new tranny and custom drive shaft, so hope that everything's being planned accordingly..

are there any disadvantage of having the dry-sump system over the oil pan (other than the initial cost & increased weight)? seems like it should be a more common thing among 20b community, but i'm surprised i don't see more of them.

maybe i should add some weight to the back. roll bar & battery are already being relocated... so hopefully it'll all balance in the end.

 

My 20b is dry-sumped.
One of the reasons for going dry-sump in any application is to eliminate the oil pan which enables you to have more freedom to position the engine where you want it; lower and further back. There are many more advantages too such as increased oil pressuere and overall capacity.

On that note, the capacity could be a neagaitve in some peoples minds since changing the oil may consist of several cases of oil. That is all part of the cost factor though. IMHO, a dry-sump system is really unneacassary unless you plan on road racing your car in which case it is a good idea because of the long 20b oil pan and its minimal capacity. Remeber, the oil is an integral part of the cooling system.