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Auto-X Project: Street Modified 2

Old 12-24-06, 12:59 PM
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Auto-X Project: Street Modified 2

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.
Attached Thumbnails Auto-X Project: Street Modified 2-photo_122206_003.jpg   Auto-X Project: Street Modified 2-photo_122206_005-2-.jpg  
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Old 12-24-06, 02:35 PM
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Update to mod list:

- Removed antenna
- Aluminum AST
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Old 12-26-06, 02:09 AM
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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
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Old 12-26-06, 11:17 AM
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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
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Old 12-26-06, 11:54 AM
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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
This was one of my original thoughts regarding moving the car back into ASP.

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.
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Old 12-26-06, 12:07 PM
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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
Thanks for the input.

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.
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Old 12-26-06, 12:08 PM
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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
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Old 12-26-06, 12:17 PM
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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.
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Old 12-26-06, 12:58 PM
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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
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Old 12-28-06, 04:11 PM
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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
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Old 01-06-07, 07:50 PM
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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/
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Old 08-26-07, 10:03 PM
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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.
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Old 09-02-07, 02:57 PM
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It is worth it to do the TII conversion while I'm in there? or is the FD torsen LSD better?
I run a TII in SM2 and I do not like the clutch LSD.

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)?
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Old 09-18-07, 07:01 PM
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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.
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Old 09-19-07, 02:03 PM
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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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