93 LS1 Endurance Race Car Build / Questions
 

Hi Guys,

I'm currently working on a 93 LS1 swapped endurance race car build. My goal is to campaign this car in the GPX class with WRL and NASA TT3.

Here's where I'm at with it:

60k Mile LM4 V8 - 290HP (All aluminum LS1 variant)
T56 Magnum Trans
Oil cooler/w Improved racing baffled pan
Mishimoto Aluminum radiator (will be boxed in)

The swap is almost done, I'm just waiting on the driveshaft.

My goal is to end up with about a 9.0+ PWR to meet both TT3 rules and WRL rules. I'm hoping that I'll wind up at > 2610lbs at 290hp to meet the rules. (NASA TT is PWR calculated by wheel HP, WRL is PWR calculated by manufacture spec on engine).

Because I'd like to use this car for endurance racing I have some specific goals in mind:

The cost of running the car for 12 or 18 hours must be something that isn't too high - something I can pass on to my drivers. This means that I'd like to run a square tire setup/w 17" wheels and stick with stock brakes. This is also the reason I went for a LM4 engine - 500$ at local junk yards to replace.

Here is currently what I'm planning, any feedback is welcome!

Wheels:
17x9.5 +38 - RPF01

Tires:
275/40ZR17 - NT05

Brakes:
Stock calipers + brake ducts

Pads:
Dedicated race pads - I'd prefer to use ST43s but I'm open

Suspension:
No idea, given it is gonna be setup for endurance racing I'd prefer to go for a softer (less fatiguing to a diver over a 1 hour driving stint). I was thinking of starting off with some Tein Type Flex's and go with a large front anti-sway bar? Or perhaps the Tein Super Racing, but I worry they will be to stiff. Any other recommendations? My budget for coilovers is 2.5k or there abouts.

Other:
The car will have a professionally built cage, cool suit setup, appropriate racing seat and aero. Aero wise I still need to figure out what I'm doing but I plan on adding aero to the car. I plan on replacing the suspension bushing as well.

Thoughts? What would you change, what would you recommend?

Sounds like you are on the right track.

You'll want brake cooling, and possibly an accusump at minimum. Also you will probably need a diff cooler, at least get a diff temp gauge in the car. Do everything you can to keep exhaust heat out of the diff and wrap the exhaust in that area. If you have $2.5k for coilovers get something reasonably good that is set up appropriately. Ohlins, Fortune, something. It won't be too stiff if you get something that is properly valved. If you go too soft and then get aero you are going to be changing the valving and spring rates anyway.

Also I'd run NT01s at least.

Awesome thanks! So for WRL I'm linked to 180 TW Tires, for NASA TT I'll run NT01s, etc. Thanks for the tip on the diff, I'll make sure to do that, now that you've pointed it out.

I looked at the fortune stuff, I've never really looked at it before so I'll do the digging there!

Thanks!

Understood on the tires. You may be better with a newer 200 treadwear tire. Nt05s were good a few years ago, but there are better options now, even if you have to run a 255/40/17.

The Ohlins DFV are just in your coilover price range. I have never heard a complaint about them.

I have an FC but run Fortune 510 coilovers. They are $1650 shipped, I have been very happy with them. The 510s are hand built here in the USA with upgraded pistons and fluid. All the parts are good quality (I have had mine apart and found all Koyo Japan bearings, quality bump stops and hardware) and they will valve them to your chosen spring rate specs and dyno them. They are worth investigating.

Good point, so my ideal tire are star specs but that limits me to the 255/40/17's, think that will be ok with 2600lbs and 290hp?

Good to know!

My car is about 2650 or so with 400 WHP and was running 255/40/17s NT01s all around until recently. I think it will be just fine with 255s. Wider tire with a bit less grip vs. narrower with more grip. I might start with the Star Specs in 255. The problem is that a 275 40 is getting pretty tall for an FD. You'll have fewer issues with the 255 starting out, and it is shorter to get the hearing a little lower.

for suspension, i would go for the ohlins, they are worth every penny. the damper does 3 things, it needs to have the valving right so the car handles, it needs to soak up bumps without upsetting the chassis, and then there is ride quality. the Ohlins do all three out of the box, and you could duplicate it with koni/bilstein/other custom valved shock, but the ohlins doesn't need the R&D. they are serviceable stateside too.

for an endurance car, you wanna go with suspension bushings that are softer, as the car needs to be able to hit stuff and not break. stock rubber, or poly is good, sphericals are not. you will want all new bearings for the 25, and before you put em in the car take them apart and repack with a good synthetic grease.

i'd think big FD radiator + stock oil cooler, would be good enough for the V8. the 25 is in december, which helps. might investigate a hood vent of some kind.

for engines, you will probably want to pick up a spare, and have it rebuilt, or at least do rings/bearings/valves in it, the 25 is a long race... accusump and baffle plate are mandatory.

brakes: we've run on performance friction forever, and we can get a set of those to run the whole 25 if we needed too, that being said getting PFC's for an Rx7 is not easy, so i dunno.

wheels: run something easy/inexpensive. for the 25 you'll need like 20+ wheels.

tires: our slow tires this year are nittos, and we're only like a 1/2 second off the times with the hoosiers, but the nittos have done 7-8 events (we've done so many i haven't been to them all!).

275/40-17 is tall for the front of the FD. It will rub on front plastic fender liners, you might have to bend in the rear of the front fenders and it will bottom up top unless you run monster truck high.

FD can really only handle 25-25.3" max up front.

If you stick to 17" wheels you might find you the shorter 255/40-17 work better up front. If you still want the larger 275 rear (which I don't recommend) at least put the 255 on the same 9.5-10" width wheel up front to minimize understeer.

If you can afford 18" wheels 265/35-18 are a great fit up front. You can go with really cheap ($135) Federal 595RS-R for street tire events. They will be a hair slower than the stickiest extreme summer tires.

IDK what your class dictates, but if you can justify wider tires 18x10.5 +38 work front and rear. Again 285/30-18 Federal 595RS-R are super cheap ($140) for street tires and 295/35-18 R888 are relatively cheap at $240.

PF01 or RP01 will be $300-400 more a set in 18", but you can use the cheaper off brand wheels such as-

http://www.ebay.com/itm/HYPER-BLACK-F1R-F21-18X8-5-38-5X114-3-FIT-RSX-TSX-TL-CIVIC-RX7-RX8-RSX-ILX-RIM-/400886893770?hash=item5d56b88cca&vxp=mtr
That are $616 a set free shipping and not too heavy at 22lbs.

On my FD I ran ($1,400) 18x10.5 +38 Enkei PF01 with 265/35-18 Federal RS-R .

Now running ($1,400) 18x11 +45 Forgestar with 295/30-18 R888. You have to run coilovers and a 1" shorter front swaybar tube to clear the 18x11 +45 for full steering lock.

Yeah, I have a local shock shop which does Ohlins - I had them rebuild my AFCOs on my miata and I really appreciate a high quality damper. It's amazing how a high quality damper with quality valving can make a highly sprung car feel amazing.

Are you using the Ohlins in a racing application? If so with what spring rates?

My plan was to go with stock bushings - and repack the bearings the Redline CV2 grease.

My understanding is that for multiple reasons a hood vent is a good thing - so it is on my list.

So I was gonna try to avoid an accusump and instead start testing the car without it and add it if it is needed. But I may be crazy.

My plan right now is to put a crap ton of sensors on the car and feed them into the data acquisition to help discover potential problems.

Right now I have these sensors in place: Fuel rail pressure, oil pressure, oil temp, water temp, trans temp.

I am going to add diff temp, and perhaps fuel rail temp. (One of our competitors has been fighting endless fuel rail problems which the current suspect is fuel boiling in the lines).

Good to know!

Ok

Thanks for the input!

yeah, but on a pair of miatae. for a long race you'd probably want to be on the softer side, easier to drive



thats what we do! or poly if its a single axis pivot


we got a chance to see the ND spec miata car, and they are still in development, but they were logging shock position and speed, steering angle, brake pressure at each caliper, rotor, caliper and wheel hub temp, radiator in and out, diff, trans, engine oils, and that is just the stuff we could see. that is a LOT of data!

the FD is a little easier as its not a new car, but yeah

Having been through WRL tech I can add a little. They do adjust your PWR if you have certain mods so if you are really close to the 9.0 it could bump you under. They hit me for .2 for a header which I assume you will have with the V8 swap, they will also hit you for shocks that have any adjusters, I don’t know exactly how much since I argued that although I had coil-overs the actual struts were Bilstein which don’t have external adjusters, I have the Bilsteins on the car to be ChumpCar legal. On the good side they weigh the cars with a full tank so that helps some.

A word of advice - Most people realize they need an accusump the same day their engine develops knocking noises. It's only $400, and a lot less than that if you do a manual valve.

Good point! I'll add it to the list.

Thanks

So I got a chance to ask them, and they said "pff in GPX we really don't care what you do, what are we gonna do push out into the next non-existent class? Instead build the car for NASA TT and we'll sort it out when you show up."

I'm using an LM4/w stock truck exhaust manifolds, LS1 intake, and original truck injectors. I've avoided doing any performance mods - so it should be legit for WRL.

Now of course they are still trying to get their car count up, so they are probably more liberal then they'll be in the future.

So we'll see what happens. We do run two GP4 cars (FC RX7s in WRL) now and their classing has been reasonable so far - and since they reserve the right to re-class you depending upon your car's performance I think they have their basis covered.

My plan for NASA TT is to try to get the car into TT3 where we have lots of good competition. So we'll see how it goes.

I may get it on track this season if I can keep going at it.

How do you get an FC into GP4? My FB is in GP3, the class of doom, here in the southeast at the first race 3 of the top 5 finishers were GP3, and for AMP half of the field is GP3.

For better or worse you stick Miata motors in them.

I'm not sure if it is an act of brilliance or insanity, but it results in a very reliable FC RX7 which has good fuel efficiency and very reliable and out handles most of the other GP4 cars. Against rotary powered FCs they tend to be slightly slower, you have more grunt coming out of corners but give it up on the straight aways a little bit - so it is almost a wash.

But PWR they tend to be classed into GP4 (with roughly stock suspension).

Against a well driven and prepped FB they don't have a chance. But generally the FBs we've raced against don't appear to be easy to drive as they spin a lot.

Now you might ask why not just run a Miata? Because the team I'm picked up a cheap caged FC/w dead rotary and had a miata motor laying around.

After doing well with that car another attempt was made build a better one. And now there are two.

I would upgrade the rod bolts as the consistent hi rpm will make them fail. I've seen it, not pretty!


QUOTE=celer;11928108]For better or worse you stick Miata motors in them.

I'm not sure if it is an act of brilliance or insanity, but it results in a very reliable FC RX7 which has good fuel efficiency and very reliable and out handles most of the other GP4 cars. Against rotary powered FCs they tend to be slightly slower, you have more grunt coming out of corners but give it up on the straight aways a little bit - so it is almost a wash.

But PWR they tend to be classed into GP4 (with roughly stock suspension).

Against a well driven and prepped FB they don't have a chance. But generally the FBs we've raced against don't appear to be easy to drive as they spin a lot.

Now you might ask why not just run a Miata? Because the team I'm picked up a cheap caged FC/w dead rotary and had a miata motor laying around.

After doing well with that car another attempt was made build a better one. And now there are two.[/QUOTE]