ChumpCar 1992 Lexus SC300

First of all, that is a very nice find! I would be sorely tempted to, after racing it at a few Chump events, tear it back apart and make it a "nice" track day car as budget allowed after graduation.

However, I must agree with the others about the stock fan. Put it back on. There are Mark-IV Supras out there running four-digit horsepower numbers utilizing that stock, belt-driven fan. There's nothing wrong with it, and it moves a lot of air.

Cool, lots of work down, but this will be a great car when you're done.

redzcstandardhatch wrote: what an awesome base for a chump car....phenomenal prep too man..wow! My lemons car got 1/10 the prep!

Thanks!

I was really tempted to just throw in a cage and go racin'! The problem is that it costs so much for a race and you loose all the money in entry fees and transportation if the car breaks. I can't really afford that, so I decided I might as well spend the time and a little more money now to (hopefully) ensure that we get the most track time for our money when race day comes.

Sky_Render wrote: First of all, that is a very nice find! I would be sorely tempted to, after racing it at a few Chump events, tear it back apart and make it a "nice" track day car as budget allowed after graduation. However, I must agree with the others about the stock fan. Put it back on. There are Mark-IV Supras out there running four-digit horsepower numbers utilizing that stock, belt-driven fan. There's nothing wrong with it, and it moves a lot of air.

Yeah, I will definitely hang on the the fan and spec a belt to use if needed. I totally agree that it will provide enough cooling - the reasons I removed it were to reduce the rotating mass of the engine, reduce horsepower loss at speed, reduce weight, and to free up more room in the engine bay.

I think the OE fan is overkill and for a road racing car. A good electric fan should do the trick in the pits and a fan shouldn't really be necessary at track speed.

I've noted your comments though, and will definitely keep an eye on this and have the fan available if needed. I'm mounting the electric fan to the OE shroud so swapping back to the mechanical fan should be fairly easy.

Suspension is all back in the car and it's pretty low up front - glad I didn't cut any more off the springs. Might have to cut a little out of the fenders at some point to keep them from rubbing over bumps, but it clears fine while sitting. (Pics to come).

Got the ECU reinstalled as well, only to find that it was running much worse than before!

Did some more reading and ran into this.
http://www.clublexus.com/forums/ls400/656360-all-my-crazy-lexus-issues-solved-ecu-leaking-capacitor.html

Needless to say we didn't use the fancy low-ESR caps, so we've ordered a set of those and they should be in tomorrow. Hoping that solves the issue, as I've been unable to find another SC300 ECU locally, and the GS300 ECUs I have access to don't work without some wiring changes that I don't want to get into at the moment. So, while the car has been laid up waiting for the ECU, I did some work on the interior.

Before installing the harnesses and bar padding I wanted to paint the cage tubing to keep it from rusting. Removed the dash and gauge cluster again and masked off the windshield and side glass (side glass will come out later, but it's staying in for the track day so I wanted to be able to see out of it).
Did some quick sanding on some of the bare metal and shot the tubing with a grey primer.
I'll leave it in primer for now.

While the dash was out, I painted that as well. I didn't really like the OE tan vinyl dash and thought it might be a little too reflective. So, I painted it with some bedliner that I used on my Miata gauge hood. Looks great IMO.

I also finally installed the sunroof delete panel that one of the drivers had cut for me weeks ago - thanks Darius. I applied a thin bead of outdoor silicone caulk around the edge of the OE opening, then riveted the panel in place. To help keep the panel tight and avoid excessive wrinkling, I drilled the rivet holes and inserted the rivets while the panel was hot (heated with with a propane torch, being careful not to get it hot enough to permanently deform). I still had to cut some stress-relief notches in the sides of the panel to reduce wrinkling, but heating definitely helped and the panel is taught now, which will help reduce wind noise and vibrations that could loosen the rivets.

You can see some scuff marks in the aluminum panel - it was a piece of scrap and had a bunch of fiberglass resin on it, which Darius removed with a flap disc before cutting it. Might paint it someday, but it'll stay unfinished for now.
Inside with painted cage tubing.

Looking great. I love how prepared you're getting it. Did you say when you're planning on racing it first?

I know you said they didn't work easily, but if a GS300 ECU can be helpful at all let me know. There's a '99 GS300 in a local yard and I'm planning on going there in a couple days to pull some parts. I can pull the ECU for you and ship it on for actual cost. I think they charge $35 for the ECU. Shipping would be around $6.

In reply to dculberson:

Thanks!

Yeah, I've learned during my (relatively short) time involved in racing that it's far easier/cheaper/less stressful to prepare than to repair. Hopefully it pays off!

As far as the ECU - thanks for the offer. I have a couple GS300 ones here, but it looks like they won't work without some modification to the wiring. If you happen to run into an SC300 ('92-'94) I'd definitely be interested in the ECU from that though.

Let me know when/if you're looking for team members! Also, might I humbly suggest racing this car at VIR.

In reply to Xceler8x:

Yeah, I'm hoping to make it to the 24 hr VIR race later this year. I'll definitely be posting here if I need to find more drivers.

Looking good. I have a spare 1993 SC300 ECU if you need one to borrow or buy. Also if your buddy has a template for the sunroof delete and could duplicate it let me know. Have you bypassed the fuel pump ecu? That's another common problem. PM me your info.

In reply to fried_rice:

Thanks for the offer on the ECU. I finally got it all sorted out today. Details to come later.

As far as the sunroof - Darius just took some measurements and cut it out on a bandsaw - nothing fancy.

Glad you got it figured out. I need to get more metal working tools and less parts, lol. My only metal cutting tool is a cutoff wheel/grinder, although I do pretty damn good with it. I almost got a 5spd SC300 yesterday for a chump car but someone got it before me, was listed for about 4 hours.

That thing is way to nice to be a Chump car. Beautiful work on the cage!

Sky_Render wrote: That thing is way to nice to be a Chump car. Beautiful work on the cage!

Thanks for the compliments. The cage did turn out very well, but seriously? Too nice for chumpcar? It still mostly looks like this on the outside!

Hopefully I'll be picking up a 5spd SC3 tomorrow, found the guy who bought it out from under me. I have been reading through the rulebook for mods to do. I currently have 4 rear supra wheels 17X9.5, which come stock on the TT Supra as rear wheels. I ran those with 400rwhp and they did great front and rear, clearing LS400 brakes with minimal grinding of the caliper, no spacers. The Supra TT front wheels 17X8.5 clear LS400 with no spacers, pnp.

You can get a set for about $400 with good tires. I know you already purchased wheels and tires, but these cars can fit massive wheels on them that clear the LS400 brakes without taking the $5 for wheel spacers. I'm sure they're good for 1-2+++ seconds a lap at least. They also will not break the 2x rule. Thanks for the inspiration! Hope to test and tune the car next weekend with nasa DE, got to do some major work to get it running in that time.

The 275/40/17's on my car were almost completely neutral, could save us from sway bar added value. Or even run the F8.5 in the rear to reduce understeer. I'm thinking I'll need an oil cooler, but I'll try to test with and without. Probably going to use an aluminum radiator, unless I can source a Supra TT radiator this week for testing.

EDIT. Got the car today.Car runs with a gas soaked rag in the TB. But the gas tank is rusted out, so I pulled it out to swap with my other cars tank. I weighed it and it weighs 25lbs, that goes against my initial reading that it weighed 55lbs. It also makes it less necessary for a fuel cell in the mean time for me.

Well unfortunately, I ran into some more issues with the suspension right before the track day. So, I don't have any glorious news to report from that. But I can give a couple minor updates.

First, some shots of the car with the cut springs up front.


If I remember correctly, this is with the wheel spacers installed. There's actually pretty adequate fender clearance. We'll probably chop off some of the fender lip anyway to give some safety margin though.

The bigger issue with this drop is the roll center. Not the greatest picture, but you can see the angle on the lower control arm is pretty bad. I don't have enough experience to say if there's enough benefit to the very low CG to make having a wonky roll center worth while. So, I got another set of junkyard springs/shocks, which I'll probably cut down a little less than this and at some point we can do a comparison. Also, note the fancy new tires, which I finally mounted and balanced. Still need to tape the weights though...
As I mentioned, the wheel spacers were finally finished. Our water-jet was down for repairs, so we had to make these the old-school way (since I'm too cheap to just go buy them). Matt and Darius, two of the drivers on the team, milled out the bore and stud holes.
After that, I chucked these up in the lathe and cut out the OD.
Didn't really have the right tooling for this, but made it work... Here are the spacers sitting on the LS400 rotors.
FYI, the spacers are 1/2" aluminum and give just enough clearance for the LS400 calipers with the 16x8 BBS wheels.

I have some more pictures of the brakes and other BS that we had to take care of last weekend and will try to upload that later tonight. Long story short, before going in for the alignment, I wanted to check all the eccentric bolts in the rear of the car, having had issues with the fronts. Turned out that 3 of the 4 were seized and the 4th had been badly damaged and replaced with a regular bolt. We ended up having to replace the whole rear subframe and swap over the wheel studs. Ended up breaking a stud in the process and generally just had a hell of a time with it.

The car is back on its wheels now though, has the LS400 brakes installed, cut rear springs are in, new subframe with good e-bolts is installed and is nearly ready for some track time if we can get something else lined up before the race.

I would use your cut springs and add a hard rubber donut to the top. That way you get higher spring rate with correct ride height.

In reply to wvumtnbkr:

Yeah, I had been thinking about that too. Might go that route. I don't want to end up with a suspension that it super under-damped, but it might be a net benefit. I'll have to give it some more thought.

Ok. So some updates from last week and the Fiasco that was last Friday. I don't have great pictures of everything from Friday since we were trying to get the car put back together in a few hours for the track day that didn't happen...

Earlier in the week, however, we got the rest of the mounting points for the harnesses installed. Lap belts attach to the factory belt anchor points (upper right of image). We welded in some thick steel plates and nuts to attach anchors for the sub belts as well. John Gattuso, one of the drivers, cut down the reinforcing plates and did the prep work and I welded the plates in with the TIG. I like using the eyelets and clip-on harness mounts so shorter belts can quickly be substituted for shorter drivers.

John also installed one of the 5-panel interior mirrors so we could test that out. Pics later.

Rear shocks/springs came out to be shortened. You can see the wheel spacers installed here.
This was about the time when I crawled under there and realized all the e-bolts were seized. Hit them with the impact gun, heat, breaker bar, nothing... So, we continued working on the springs and I made plans to get another subframe from the junkyard. Here's one of the rear springs cut down.

The OE spring has a very shallow angle to the helix near the bottom of the spring so that it sits on the shock perch without any risk of it coming off. We did grind flats into ours after shortening it, but it was still coming off the perch with vibration, so we welded a little rail onto the perch and blasted a small hole though the perch and spring with the plasma cutter and wound some safety wire though the two holes. This should keep the spring from coming off the perch even under extreme droop.

A slightly closer shot.
Here's Darius seating the spring.
Another random item to update - I was very concerned about not having any spare tires for the race. If we get into any minor scrapes and bend a fender, etc, I don't want to be out for good with a cut tire. So, I'd been looking for something to use as capable spares. Last week, some nice 18" Dunlop SP Sport 600's came up on Craigslist. Guy was asking $25 for the pair and they had lots of tread left, though one tire had two small punctures in the middle of the contact patch. Bonus - they're 200 treadwear, so they should be fairly competitive too. I picked them up and mounted them on some old Mitsu Eclipse wheels that I used to run on the RX-8 (they're the perfect size for a C-stock RX-8).

Very happy to have found these, though I think they'll only fit the back of the car so any front tire issues will require a rotation.

Having discovered this e-bolt issue Thursday, I made an early morning dash to the junkyard Friday after canceling my 8:00 AM appointment for the alignment. I had previously dropped an SC300 rear subframe and stashed it in the yard to have a spare differential, so I was able to get the complete subframe in about 15 minutes including all the suspension, brakes, shocks/springs, differential, etc. It ran me $251.74 - more than I was hoping to spend, but at least it gives us a lot of spares...

That night, after work, Matt, Darius, John and myself set to work trying to swap everything to make it to the track day.

Old subframe came out.
Here's Matt working on swapping parts.
While we were in there, the sway bar endlinks needed to be replaced as well. I had grabbed some spares from the junkyard, so those went in too.
The LS400 brakes went on the front that night after cleaning and greasing the slider pins.
Around 4:00 AM (I think?) after breaking a wheel stud we sat down and decided we wouldn't have time to do even a rough alignment, bleed the brakes, or install the harnesses before we needed to leave for the track (2 hours away in Alabama). It was raining hard and the thought of struggling all day in the cold and wet to get the car on track after pulling an all-nighter was not at all appealing, so we called it a night after getting the car back to a rolling state.

I'll be going through the suspension again this week to make sure nothing was overlooked in the last-minute rush. The wheel stud will be replaced and the axle nuts still need to be torqued appropriately. Then we'll bleed the brakes and get back to work on the remaining tasks - mostly safety items.

At least we have about a month before the race. Hopefully this will be the only last-minute struggle we have to deal with...

Ah, almost forgot the update on the ECU. So, after Josh started working on replacing those leaking capacitors, I couldn't get the car running correctly. At first we though it could have been a PCB trace that was damaged, then we though we might need some fancier low-ESR capacitors, which are highly-recommended by those familiar with the ECU. None of this made any improvement to the car which had trouble starting, wouldn't rev well and was bogging severely under load.

I hooked up the diagnostic jumper to pull any engine trouble codes and check to see if running in the basic "timing set" mode would make any improvement. Everything checked out fine with the issues persisting. While I was in there, I decided to bypass the fuel pump ECU (yes, this car has an ECU just for the fuel pump to reduce pump speed and noise at idle and low load). There's another jumper in the diagnostic port just for bypassing the fuel pump ECU and I thought the problems could be attributed to low fuel pressure, so I tired that and, BAM!, all problems solved!
I still don't know if the root cause is the signal from the engine ECU to the FP ECU, a problem with the connection between the two, or a purely coincidental failure of the FP ECU exactly when we removed the engine ECU (the two are physically separated). Failure of the FP ECU is common on these cars and it was on the list of items to remove anyway, so I guess I shouldn't be too surprised. Either way, the problem is solved. I'll be wiring in a permanent bypass as soon as I get the time.

You guys are doing some serious work. I've been working like mad on mine. I had to switch the gas tank, front control arms, and a bunch of other stuff. My Fuel pump ECU was toast too. I have a track day Saturday and Sunday to prep for the Road Atlanta sprint race. Just got the car on Sunday, it hadn't ran for a year or two. My Chump SC

Thanks for all the info with your build thread, it's really helpful. I've tracked a few of my SC's in different configurations for about 20 track days. I'm not an expert, but I do know the platform. So if you need anything let me know. If you all are going to be at Road Atlanta it'd be cool to help.

EDIT: Also if you are going to be at RA, I can bring a crap load of misc spare parts and about 5,000 nuts and bolts, lol.

In reply to fried_rice:

Nice.

Yeah, still planning to be at Road Atlanta in February. Hopefully we'll be pretty well stocked on spares, but the more the better. We'll be around for most of the weekend. (Up until the drift event).

Finally made it back to the shop last night to take care of some of the items left from last weekend.

Started with torquing the axle nuts and reinstalling the retaining plates and cotter pins.

Replaced the broken wheel stud. IIRC someone was torquing the axle nuts by bracing the hub with a crowbar through the studs, so not too surprised that it broke off. It wasn't a failure in tension, in any case, which would be really worrying. New stud installed.
While in there, I replaced the last of the swaybar endlinks (right rear this time).
Also had to bolt in the ABS sensors.
I wanted to get the last e-bolt out of the old subframe to have as a spare. Here's the process I had to go through to disassemble these:

Cut out the subframe around the bolt and press the steel sleeve and bolt out of the control arm.
Weld the sleeve to a piece of angle iron.
Get the sleeve really, really hot.
Torque the crap out of it with the impact gun, until if finally lets loose.
What a pain! At least it's something we should only have to go through once.

I also bled the front brakes so I could move the car around a little. I still need to do a proper job and go through all four corners in order, but that can wait until this weekend.