Plumbing to remove Trac? (91' LS)

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Spinnetti

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382
Location
KY
So, for whatever reason, Trac simply doesn't work reliably in racing conditions. It works for a while then gives up. It adds weight and isn't reliable, so I want to yank it, besides the fact that I put in a Supra Torsen in a SC300 4.27 diff :) ABS works great, and I want to keep that. I know the trac pump and whatnot is a simple yank, but what about all the plumbing at the trac actuator? Will it work if I just plug the port that goes to the trac pump and leave the actuator alone? I have the fuse out as it is, so trac is permanently off anyway. Seems like just plugging the one port is a lot easier than figuring out the plumbing mess.. thoughts?
 
Interesting idea. TRAC isn't working on my car anymore either. We've tried bleeding the actuator and pump, but it won't work anymore. It worked for our first year of racing, and we'd shut it off most of the time anyways. Now we're looking to get any weight out we can, so pulling the TRAC system might be a great idea. We do like the ABS though too.

Btw, what are you running for brakes now? We just finished running at Road America last weekend.
 
I pulled the whole pump and accumulator as well as the line to the abs. I cut off and welded up the fitting at the distribution block and capped off a short section of line at the master. Abs still works fine. I didn't remove the distribution bLock by the abs pump though because I didn't know which line went where. I've got 95 brakes I font and 91 brakes in the back. Works great. I did finally find the limit of the tires last week at gingerman with 2nd fastest lap of the event, and am going to try 235 up front on 8" wheels and 255 on 9" wheels in The back
 
Can I see some pictures? Also, what pads are you running again? We love our ST43's, but might move to something more aggressive to pull the rear end down more under braking. We get a lot of waggle under braking now. I love our 245's in front, and 275's in the rear. We're running Supra wheels, 17x8 in front, 17x9.5 in the rear. Do you have any bias control in your brakes?
 
Can I see some pictures? Also, what pads are you running again? We love our ST43's, but might move to something more aggressive to pull the rear end down more under braking. We get a lot of waggle under braking now. I love our 245's in front, and 275's in the rear. We're running Supra wheels, 17x8 in front, 17x9.5 in the rear. Do you have any bias control in your brakes?

Sure, pics are public on Facebook
http://www.facebook.com/media/set/?set=a.114096618029.102044.645133029&type=1&l=c51eb4fec1
There's no pics of the trac remove, as there's nothing to see!

I'm using the st43's too, at least in the front. This last event we were a lot faster, and the front rotors cracked up pretty good, but braking was phenomenal. We used the porterfields in the back, and went through a full set of those, but at 1/4 the price, that works out pretty well. No bias control. I let ABS sort that out. Though it wiggles a bit, we still out brake everybody. Car is awesome, but the fuel burn is twice the little cars, coupled with expensive tires and lots of synthetic fluids makes it expensive to operate. I'd love to run with you guys and see how we stack up. Look up Spinnetti on youtube to see a couple laps from Gingerman. on Day 2 at gingerman last weekend, when the flag dropped, I was on the back side of the track and passed 15 cars by the time I hit the start finish line! - it was nuts.
 
Which porterfields are you using in the rear? We got a ton of stress cracking at Road America, on brand new rotors. But you can't feel them, so they're probably still good for another race on a track that uses less brakes. Our brakes are phenomenal too, we outbrake the entire field, even the lightweights. We're trying to look not to see if we can shed unsprung weight and find some 2 piece front rotors. Totally agree on the expense to operate, its a fun car, but tires, fuel, brakes, and fluids get pricey. I'm still cutting our most recent videos, but I'll post when I get them up on youtube.

We're about 3000lb dry. Might be able to sneak out another 50lbs, 100lbs if we go with lighter weight wheels. Debating going back to 245 or 255 rear tires, not sure we really need the 275's.
 
Which porterfields are you using in the rear? We got a ton of stress cracking at Road America, on brand new rotors. But you can't feel them, so they're probably still good for another race on a track that uses less brakes. Our brakes are phenomenal too, we outbrake the entire field, even the lightweights. We're trying to look not to see if we can shed unsprung weight and find some 2 piece front rotors. Totally agree on the expense to operate, its a fun car, but tires, fuel, brakes, and fluids get pricey. I'm still cutting our most recent videos, but I'll post when I get them up on youtube.

We're about 3000lb dry. Might be able to sneak out another 50lbs, 100lbs if we go with lighter weight wheels. Debating going back to 245 or 255 rear tires, not sure we really need the 275's.



When I ran the stock 91' brakes I got amazingly good wear. I used the existing factory brake scoops and extended them - never got any cracking.

This last event (first with the 95 brakes), the brand new front rotors are all stress cracked, though both rotor and pad wear was good. (I had also CNC slotted my rotors)

I have R4S in the back. Used em up in one event, but are a LOT cheaper - we actually hit the backing plates, but didn't seem to increase stopping distances and we never noticed. I'm at least 100lb heavier than you guys too. I might have to go back to some brake ducts in the front, and might need to upgrade to the 95 rotors in the rear too.

Funny you mention backing off of 275 in the back... My calcs say 255 should be what I need for the drag/gearing/grip combo I'm after. I just ordered some wheels, but ends up being about the same overall weight as the stockers.

I still want to do a 5speed, but the controller is the hold up. If I keep doing this for much longer I may have to do it myself. Good winter project. I'd do full logic for auto downshift, lock and unlock of TC, shift mapping so it shifts at the optimal points and all that. I might not paddle shift it then, but just do a good race program for it and leave it full auto, always keeping the motor around the torque peak. The big benefit though is just having the extra gear in there. The 2-3 gap on the 4 speed is huge, though you can mitigate somewhat by gearing (smaller tires etc.)..
 
I don't mind the stress cracks, you can still run 'em. Just need to keep checking things depending on how long the race is. This year we're only running dual 7 hr races, so we can probably get another 7 hours out of our pads and rotors, and check them after. I'll look into the R4S, we might try some new rear pads.

How'd you do your calculation?

Yeah we've talked about making our software for a cheap PLC to control the solenoids, but we've never gotten around to actually doing the work. I'd love to have a rally style sequential shifter, rather then paddles. I agree on the 2-3 gap, our low speed acceleration is awful. The 4.27 gears made it less bad, but any car with a manual trans still pulls on us to start.
 
I don't mind the stress cracks, you can still run 'em. Just need to keep checking things depending on how long the race is. This year we're only running dual 7 hr races, so we can probably get another 7 hours out of our pads and rotors, and check them after. I'll look into the R4S, we might try some new rear pads.

How'd you do your calculation?

Yeah we've talked about making our software for a cheap PLC to control the solenoids, but we've never gotten around to actually doing the work. I'd love to have a rally style sequential shifter, rather then paddles. I agree on the 2-3 gap, our low speed acceleration is awful. The 4.27 gears made it less bad, but any car with a manual trans still pulls on us to start.

Trans is still stinky... we don't start passing people in earnest until 3rd kicks in. Any idea if its possible to swap the 4 lower gears from the 5 speed into the 4 speed? I don't care about having 5 speeds, but like the spread on that trans.
Also, what are auto trans failure modes (I don't know autos)? We had it not go into third for a lap, but then worked after that. Could that happen if we overfilled the trans? We had it too full, but I couldn't read it on the damn dipstick.

I didn't have much rotor wear, just the cracks. They are minor, but a lot of em. Didn't get them with the original brakes, but we are faster now, so lots more heat stress. I ordered some new rotors just in case, but will run them again most likely. Front pads are probably good for another event too. I forgot to measure them new, so not sure how much we used. I'll get a spare set of those too just in case.

On tire size, I wasn't scientific, but used the following criteria:
> Smallest diameter possible to improve gearing
> Lightest weight possible at the grip balance I want
> Stagger front and rear width to balance handling (oversteers now)
> Minimum rolling drag possible while getting the grip I want
> Balance power & grip. Over-tiring just wastes money, but with the 225's we have more power than grip, so I want to sneak up on it until they balance out. (kind of like control harmonization in an airplane)

Its actually pretty close on the 225's in front, but not in the rear, hence only going 235 in the front, but 255 in the back (8 & 9" wheels, and 1/2" spacers if they will fit). I also get more left side wear (natural consequence of track design) and the right side is perfect, so I'll run an asymmetric alignment with 1/4-1/2 degree more camber on the left (if there's any adjustment left), and possibly more caster on both sides. Suspension tuning is kinda my "thing", and we are darn close now. 3 of the 4 shocks are blown and it still handles great. I might try and drill those, change the oil and weld em back up, but not until I try out the new wheels and tires.
 
I agree on the transmission wholeheartedly. I don't know much about auto's either. I wish you could just change out the gear set, replace OD with 1:1, and make 1-3 a much closer ratio set. Which is really the only reason I want the 5 speed too.

Road America is known for eating brakes, and it definitely did this year for us. Granted we were going faster then last year, so it makes sense. Our pads are fine, and the rotors might make 1 more race, but I hate gambling with brakes.

We did the tire thing with trial and error too. Started with 225's on 16" wheels, 300 treadwear DZ101's. They did okay. Then upped to some 245's which barely fit on the 16" wheels, again 320-ish treadwear, I think Fuzion ZRi's. They did better. So we figured we might as well try the 200 treadwear like the fast teams in Chump. So we did 245/45R17 in front, and 275/40R17 in the rear. We knew we had to keep the the tire OD's the same to not freak out the speed sensors. Turns out 275's in the rear might be too much. Plus our stock Supra wheels weigh a ton. I think we're going to try 255's all around next. Its a slightly smaller OD, but keeping all 4 the same will keep the ABS happy.

We finally got our alignment adjusters all loose this winter, replacing the rears with new parts. But when setting our suspension for Road America, we couldn't get as much out of the front left as we used to. Turns out the crash from last year did bend stuff. So our alignment is limited and we can't quite run what we want. It'd be nice to get a little more negative camber in the front, without losing all of our caster.
 


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