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Auto-X Project: Street Modified 2
2 Attachment(s)
I decided to try and take a stab at building a moderately competitive SM2 car for Solo next year.
My budget, including r-compound tires, is probably going to end up around $2-$3k. I do all of the work myself, and my Rx-8 serves as my DD. My current list of mods: Reman motor w/ stock ports Koyo radiator Stock twins w/ simplified sequential setup XS IC Manual boost controller PowerFC Pettit downpipe 3" Rx7store Hi-flow cat Apex'i GT catback 3" Apex'i Intake 4 x 850cc injectors Sard FPR Struct tower bar Ground control kit Koni Yellows Eibach springs: 700F 500R Brembo crossdrilled rotors 5zigen Pro Racer GN+ 17x9.5 +43 Wideband o2 Walbro 255lph fuel pump Removed A/C Removed all speakers and their enclosures Removed jacks + tools Keeping P/S and airpump Adding tow hitch for the tire trailer (the big 19lb one) May remove cruise control Mods I'm thinking of purchasing: Tires: 275/40 (Either V710 or A6), I am considering 295/35 for the A6. Battery relocation: lightweight and decent enough to go a few days without dying Lightweight seats Underdrive pulleys Widebody fenders Slotted or OEM rotors Brake pads Intake (I need something that takes up less space) All my fluids will need changing. That includes oil, brake, coolant, gear, etc. I know my budget doesn't allow me to buy everything. Maybe after accumulating this stuff over the next 2-3 years, I may, but that's not my priority. I want the best bang for buck. At my last Divisional, the car weighed in at 2750 w/ ~1/3 tank of gas. I removed a bunch of stuff since then, so I may end up in the mid-high 2600 range with any luck. Power-wise, the stock twins w/ the stock IC put down a mere 287whp with a nonfunctional airpump. The car doesn't burn gas at low RPMs. I'm thinking that fixing those two issues should push me over the 300 mark. I figured by starting this thread, I could track my progress and collect any suggestions about where to spend the money. I've been autocrossing for a little over two years now, and I feel that I have reached some (not ALL) of the limits of my car. I am open to whatever is legal for SM2 as long as it's not too crazy. I attached some photos. Excuse the poor quality, it's just a cellphone camera. |
Update to mod list:
- Removed antenna - Aluminum AST |
Shorter rear gears, 4.3 at least, and 4.77 if you can find them. Brake pads I would run Carbotech Panther +'s. I wouldn't bother with wider fenders unless you want to put wider tires and wheels, which I think would blow your budget. Stiffer springs, more like 900/700 would be better. At some point I'd ditch the stock turbos, but again I think that blows your budget, though not by much.
Gears are the big one. -Andy |
If you wanna lose more weight, I'd consider using a aluminum radiator that's thinner than a Koyo. (I see some on eBay that are about stock sized). And convert from an aluminum AST to AST elimination. Both of these will save in component weight and reduce the coolant required to fill the system.
If the car will see track use then the radiator downsize obviously won't make as much sense. Dave |
Originally Posted by dgeesaman
If you wanna lose more weight, I'd consider using a aluminum radiator that's thinner than a Koyo. (I see some on eBay that are about stock sized). And convert from an aluminum AST to AST elimination. Both of these will save in component weight and reduce the coolant required to fill the system.
If the car will see track use then the radiator downsize obviously won't make as much sense. Dave I don't think I could stomach going back to a stock radiator after seeing 110C during my 3rd auto-x run in +90F weather. |
Originally Posted by AMRX7
Shorter rear gears, 4.3 at least, and 4.77 if you can find them. Brake pads I would run Carbotech Panther +'s. I wouldn't bother with wider fenders unless you want to put wider tires and wheels, which I think would blow your budget. Stiffer springs, more like 900/700 would be better. At some point I'd ditch the stock turbos, but again I think that blows your budget, though not by much.
Gears are the big one. -Andy 4.33 gears might be nice to have as I don't have intentions on driving 160+ mph. Will having a 4.3 or 4.7 final gear force me to upshift to 3rd on longer courses? The turbos will be swapped after the stockers break. Thinking about BNR Stage III's to stay sequential. However, I can be talked into a single. |
Wow, that's a high temp. Are your fans rigged so you can run them full blast in the grid? Does ice-bagging the intake manifold help at all?
(Makes me wonder if it is illegal to spray your radiator in the grid? - probably) Dave |
Yes, the fan mod was one of the first to be done to the car when I bought it. The only thing that helped was keeping the car running the whole time I am in grid.
I can't find in the rules that you can't cool your engine in grid, only that you cannot preheat your tires. |
I ran the 4.77 gears when I had a bone stock reman motor, with redline set to 8500rpm. With the 275/40 17's, that should let you run mid-high 60's in 2nd gear. That should be fine for most courses. While the 4.3's are OK, the 4.77's are a huge help for getting off of low speed corners.
As far as cooling, you can spray all you want in grid. I water down my radiator and I/C between runs. If you want to run more tire, you might just upgrade only your rears. I had 275's on 10's, and 315's on 11's with stock fenders at one point. The rears did need to have the lip rolled completely flat, and a little flare. But that can be done with a fender roller. -Andy |
Sm2
Like Andy said, do the gears then BNR Sequential if you can. However I have to point out that Andy likes a very stiff car. He can handle it because of who he is. Some easier springs would be 375 rear 550 front, then 450 rear 600 front, then 600 rear 800 front, then Andy's rates.
Softer will make the car a little less edgy. Ask to drive a car with very stiff springs before you change yourself. Allan
Originally Posted by AMRX7
I ran the 4.77 gears when I had a bone stock reman motor, with redline set to 8500rpm. With the 275/40 17's, that should let you run mid-high 60's in 2nd gear. That should be fine for most courses. While the 4.3's are OK, the 4.77's are a huge help for getting off of low speed corners.
As far as cooling, you can spray all you want in grid. I water down my radiator and I/C between runs. If you want to run more tire, you might just upgrade only your rears. I had 275's on 10's, and 315's on 11's with stock fenders at one point. The rears did need to have the lip rolled completely flat, and a little flare. But that can be done with a fender roller. -Andy |
It is worth it to do the TII conversion while I'm in there? or is the FD torsen LSD better?
https://www.rx7club.com/3rd-generation-specific-1993-2002-16/differential-teardown-tii-lsd-install-writeup-535290/ |
Update
I just earned enough points at the latest event to secure the regional SM2 class, so I will be running in the PAX group for the rest of the season. The STS2 group here in Atlanta is going to be fast bunch this year at Nats. I'm going to need allot more than 300whp and 275's to keep up with those guys on index.
Nationals is off the menu for now, lack of money and time off work :(. But it is my intent to go next year. Here's what I did: - I got the 275/40 V710's and they are great tires! - Odyssey PC680 mini-batt. Holds a charge and cranks the motor no problem. - Brembo blanks. Found out these are ~4 lbs/ea heavier than stock. Wow. - Scored two Corbeau Forza seats for the price of one :) - The new intake/intercooler is a huge improvement from the stock one. Amazing how much more pick up it got after I replaced it. Can't wait to throw the car on the dyno to see how much of an improvement it made. - Hawk HPS pads (will be switching to Hawk HP+ or Carbotech next). These do fine, but I will likely need something more aggressive so I can keep my foot off the brake and on the throttle. - Various other things that sucked up a bunch of money before I was done. I will be looking for 4.777 or 4.3 gears over the next few months. I'm hoping it's not a terrible pain in the butt to take the diff out. Sticking to one task at a time helps, I guess. |
It is worth it to do the TII conversion while I'm in there? or is the FD torsen LSD better? The only time I notice my car understeering with the current set-up is accelerating at low speeds in 2nd when the rear locks up. Downshifting would fix this but then you have to fight the twitchy-ness of 1st gear wheelspin. Also, the locking and unlocking of the rear end in corners affects the chassis; basically, once it is locked you either have given it just enough throttle to get out cleanly or you are drifting until you can get it settled back in (meanwhile any throttle inputs are locking and unlocking the rear affecting the chassis.) The only time I can see the TII rear working better than the Torsen in Auto-X is if you pick up the inside rear wheel cornering, but I would regard that as a suspension issue that needs to be fixed. Those are my clutch type LSD gripes, what are the gripes of those that have Torsen LSD (besides their fragile nature)? |
I have inside rear wheel lift problem with Torsen LSD.
But the inside rear lift might be due to these short stroke japanese coilover. I remember GAB with GC coilover kit do not have this issue. |
I don't have the inside tire lift on Auto-X, but on the hillclimb if I get caught on the road crown wrong I don't have enough droop in my suspension (short stroke coilovers).
I would like to fix that w/ some tender springs as I can adjust the shock body down for more droop. |
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