Rx7 time attack
 

Needing some help please,
I have an fd3s with 20b turbo with 780hp.
6 speed sequential
100% track car
seam welded
fully caged
strengthened sub frames

what is the best ride height to run?
I see people saying 25inch to fender but I dont have an original guard left on car they are all custom fibreglass does anyone else have any other measurements,

also do I need adjustable arms to achieve the right camber when car is lowered?

What is the best offset wheel to run?

Im running a rear radiator setup to help balance weight and driver mounting is moved back,
has anyone has success with rear radiator mounting.
iv got 2 12inch fans producing 1800cfm each plus some air deflected through air intakes into radiator. Do i need to run a full roof scoof (dont want to).

im trying to make the fastest rx7 i can. I live in nz and there are a few fast ones over here but I would like to give them a run for there money.

chassis is bare at the moment almost ready for paint so before I get it painted I thought id ask some questions incase I need to change something.

thanks so much for any help
sam

The questions you are asking dont really have answers.

They are variables based on the rest of your set-up which you did not provide details of.

Just get out there in your car and start driving on the track and you will start picking up on race car knowledge with the help of other enthusiasts.

there are a few things you can do, you can put the suspension together with no spring and run it through its travel. for most FC's the ride height is dictated by the tire hitting the body, we want 50-100mm of travel, and that would pretty much set the ride height. (how much travel depends on the roads/track and the springs you choose, smoother and stiffer = less travel, etc). the alignment you end up with depends on the tire you're running but us mere mortals on 205/225 tires want about -3.5 degrees of camber, so you should make sure your setup can do that.

the best offset is tricky, if you put wider fenders on it, it changed. best practice is probably to put a wheel and tire on it, and then space it out until it looks right/and can go through the whole travel without hitting stuff. stock was 40mm. if you're using really wide tires you should check the bump-steer, most race car books say to set it to zero, but with 800hp you might want a little. check is more to make sure you don't have too much

the rear is simpler, once you get the front mocked up you just want to check the camber/toe in the rear. usually we'd end up at about -1.5 to -2 camber in the rear, and zero toe.

i don't know what the final numbers would be for your setup, but in a race car you put it together and make sure you can get in range of, well the last race car you built. or i guess what works for the tires you picked. you will still have to tune it in once its running, but that is part of the fun

Top Tip: all the suspension arms should move freely, any binding will cause odd handling

oh i don't know about the rear radiators, if they get airflow it will work. my buddy wants to try it, but so far we haven't.

780 HP :eek: That'll be a lot to handle. In addition to the above, you may want to look into a front slitter if you don't have one (and assume you already have a large wing). You may also need a widebody kit with large sticky tires with that much power. I'm only running a measly 300 HP so i'm really just guessing.

Oh, and tracking a 20B, I assume you have deep pockets :)

Awsome thanks for the tips guys!

and no deep pockets isnt the case, im just a diesel mechanic that does way to many hours to go and play the silly game we are addicted to called racing. Wouldnt have it any other way!
front splitter wing ect ect all the aero will be there.
yip wont be short on hp thats for sure but iv got the tune all controlled to rpm/throttle/gear so the power is smoother and dont have full power in 1st gear ect. Boost rolls on.

and yes running a wide body kit to fit big wheels.

Ok im no doctor but i have a good you know what *points at temple* ; wouldnt you want to know what your roll centres are on whatever geometry suspension you have in there, and then get your ride height to correspond?

Be good to see this thing out on track.

I'm building my set-up around 18 x 11 +30 w 295/30R18's. I can tell you with this offset you will need to modify/clearance the headlight buckets to attain full lock and bump, factory guards also need trimming at the rear of the wheel arch. If you can visualise the amount the wheel moves fore and aft in the arch it is significant, unless you want to really cut up the front end I wouldn't go any more aggressive than this. My advice - have your wheels and tire sorted before paint!

Some have gotten away with 18 x 11's on here with a +50 offset, but with a widebody that's going to look a little awkward. Going more aggressive give you gains in track width but the downside of an increase of scrub radius - everything is a trade off.

I'd start by figuring out the maximum tire width you can run in whatever class it is that you plan on racing in, and work backward from there. As a starting point I can recommend the High Performance Academy offshoot, Racecraft. The introductory lesson covers the basics, you may wish to dig deeper in the forums.
https://www.racecrafthq.com/dashboar...heel-alignment

If you have time, map out your pickups in a program like Suspension Analyser, which will show you exactly how your set up behaves dynamically. I haven't yet for my RX7, but let me know if you do as it isn't a small task!
Performance Trends

I'm assuming you're aware of this guy? NA 20B, ton of aero. He may been keen to give you a few tips to get you started?
https://www.facebook.com/3rotorracing/

A light bulb just went on...did you buy Ricki's ex drift car?

Chris,

cool thanks for that info
Yea looking at running 11s on rear as well, car is already tube front and rear.

Will look into that suspension program.

yip bought rickys car, so far its a full bare chassis about to get a new cage put in. Fully seam welded now. Removed some parts for weight. Getting bit of a make over to change over to racing. Yea man iv watched heaps of 3rotor racing vids, found him on fb but got hit with the seen and no reply.
looking at ap front brakes, although iv got my eye on some endless fronts brembo rears that are for sale atm.

what set up do are you running?

The reference to 25" ride height was way too simplistic and should have never been made. Proper ride height really is dependent upon your shock travel. 25" with stock upper shock mounts with the integrated bump stops means you don't have enough travel for example. Granted you are running coil overs so that doesn't apply but gives you a start on what to look for as part of what j9 mentioned.

For a tight course I would talk to Andy Mckee and Eric Strelnieks who i believe have won a lot of titles in SCCA in the USA. They run big aero and big tires. For a roadcourse type of time attack find a good road course set up and loose as much weight as you can , and run big aero and tires. A ride height of 25" is what i run , stock control arms except rear trailing arm and toe link, solid bushings, offset upper front top control arm bushings ,1300 lb front spring , 1400 lb rear, medium sized front bar, stock rear bar. 3.5 front camber , 2.5 rear with 18 inch 345 hoosiers all around.