How do i get brakes to hold boost???

[Vader 87]

How do you guys launch with all that boost??? All i can get is maybe a pound if im lucky I have the S10 cylinders and soft shoes.

 

[KEVINS]

I always thought that what we were doing was average. We have nothing done to the brakes at all and I can get 10+psi just on my radial street tires in the driveway. With the slicks I've held it for 17psi. I just stand on the brake pedal until my face looks like this . I push REAL HARD!!

Evidently it doesn't work for others and I have no idea why.
I'd like to try someone elses to see what it feels like. The pedal will hit a "stop" but I KEEP PUSHING further down. That's all I know..

Regards
KS

 

[TylerDurdenOLD]

you can also use the ebrake, i have held 15psi on them, although thats not the wisest thing to do, but holding 5psi on the ebrake is probably not hurting things
dan

 

[PsychoBuickBoy]

I also have pretty much the stock brake system and I have always been able to hold alot of boost too. I launch at 10 psi off my foot brake at the track (ET Streets). I wish I knew the secret!

 

[Chuck Leeper]

Foot brake boost

Holding the boost w/ the foot brake sometimes involves more than just using the right parts. ALOT of "soft shoes" AKA cheapos, do not make 100% or even close to it, contact w/ the drums.
Some drums are bellmouthed, out of round, warped, etc and only add to the lack of grip.
The backing plates, which are flimsy at best on these cars, can have the shoes out of parallel w/ the drum surface too.

The best attempts at getting hi boost hold involve correcting all the above and even checking the rear brake pressure. It's not always where it should be either.
Some of the vendors carry a "jumper" valve that increases the pressure for a launch.
The worst possible scenario is the park brake deal. Repeated hi boost launches will warp or even rip the brakes loose!!

HTH,
Back to my brake job

 

[TylerDurdenOLD]

I agree with chuck, using the ebrake for high psi launches all the time will cause damage, backing plates usually....its just one of those old school techniques, that works till you hit the limit of the system...what that limit is, is different for any can, i havent hit mine yet, and probably wont try anymore
dan

 

[Vader 87]

Im also guessing that the type of tires you have does MOST of the holding. Ex: ET streets will hold more psi than 235/60's w/no change in the braking system.
I was under the impression that it was all in the brakes.

 

[c&cgn]

Try a wildwood adjustable proportioning valve. They work like a charm. I haven't yet seen how much boost I can hold at the line with slicks and a prepped track, but the other day I held 9psi with Nitto's on the street while it was raining(and had been for several hours). Needless to say I was impressed with this little test and I hadn't even cranked the valve fully. You should be able to get one from Summit or Jegs.

 

[Vader 87]

whats the cost of a proportioning valve??? how hard is it to install??? is it bad on brake components???

 

[rick richardson]

holdingboost

my car holds 10 psi foot braking i was thinking something was wrong all my friends said there cars only hold3-6 psi but thay spin like hell my car does not i got the car just like this does not look like any upper or lower arms i dont know i am thinking about putting a air bag in right side any ideas thanks rick 87 gn NC

 

[c&cgn]

From Summit's website:

WIL-260-2220

Overview

--------------------------------------------------------------------------------

$39.95


Part# WIL-260-2220
Material Billet Aluminum
Finish Anodized Black

--------------------------------------------------------------------------------

This proportioning valve is adjustable between 100 and 1,000 psi with a twist of a knob and can reduce pressure up to 57 percent. It lets you adjust brake bias quickly and easily to compensate for changing track conditions or for big and little tire combinations. Wilwood machines this valve from billet aluminum and gives it a durable anodized finish.


I did not install mine myself. I don't want to mess around with these brakes I would rather have a pro do it. They should be able to do it in 2 hours. You will then be able to hold as much boost as you want.

 

[Tom87GN]

bad brakes too

Do any of you guys have vacuum brakes on your car? I have converted my GN to vacuum brakes due to a Slugmaster failure a few years back. I went to the track a few weekends back and could only hold 5 psi at the line. That sucks. I want 10 at least.

I do not have soft compound shoes or bigger cylinders yet. Any comments?

 

[Vader 87]

c&cgn....thanks for the info i really appreciate it....im going to look into getting one.........looked into it, im gettin one

 

[mad999]

I haven't even looked at my brakes since I bought my T. It will hold 5-6 psi no problem. Haven't tried it higher yet. I don't know what the difference is in them. I guess I will just be thankful that it does do it.

 

[Vader 87]

im guessing if you go with a proportioning valve then a line lock is now a MUST HAVE item.....Jason

 

[bob547]

Hi Vader, Let me tell you my experience with making boost and holding the car with the brakes. My fathers GN could make 10 lbs of boost by power braking at the line. When we changed to a bigger turbo, the car did not make any boost by power braking, the car was slower with the bigger Turbo because it was slow off the line. With all the modifications on your car, you need a higher stall speed converter, or a trans brake. My mother has an 89 turbo TA, when she blew the trans, I rebuilt it with all ART Carr parts and a new converter, the only problem was they sent the wrong converter, it stalled at only 1800 rpm! I thought something was wrong with the brakes. Art took back the converter and sent us a 9 inch non- lock up. The point is, your combination makes boost at a higher rpm, so there is no way to hold the car with the brakes and rev the engine to make boost. You need to go to the next step, a trans brake and a better converter.

 

[Turbonut]

Originally posted by bob547
Hi Vader, Let me tell you my experience with making boost and holding the car with the brakes. My fathers GN could make 10 lbs of boost by power braking at the line. When we changed to a bigger turbo, the car did not make any boost by power braking, the car was slower with the bigger Turbo because it was slow off the line. With all the modifications on your car, you need a higher stall speed converter, or a trans brake. My mother has an 89 turbo TA, when she blew the trans, I rebuilt it with all ART Carr parts and a new converter, the only problem was they sent the wrong converter, it stalled at only 1800 rpm! I thought something was wrong with the brakes. Art took back the converter and sent us a 9 inch non- lock up. The point is, your combination makes boost at a higher rpm, so there is no way to hold the car with the brakes and rev the engine to make boost. You need to go to the next step, a trans brake and a better converter.

FINALLY someone gave the correct answer!!!!!!! Yea! Thats why you need to know what rpm your at as well as boost. I don't give s#$% what the boost is unless you give rpm numbers to. The stock D5 converter is 24to 2600 stall period. Big turbos will not build much boost that low. It's simple science, I have vac. brakes and leave at 8psi, DS data shows 2850 when the MPH starts showing something going on. Sounds about right to me for a stock converter. 15psi launch with a stock conv is a bunch of $%$^% Maybe with slicks and a baby turbo. My 2cents worth.

 

[c&cgn]

Originally posted by Turbonut


FINALLY someone gave the correct answer!!!!!!! Yea! Thats why you need to know what rpm your at as well as boost. I don't give s#$% what the boost is unless you give rpm numbers to. The stock D5 converter is 24to 2600 stall period. Big turbos will not build much boost that low. It's simple science, I have vac. brakes and leave at 8psi, DS data shows 2850 when the MPH starts showing something going on. Sounds about right to me for a stock converter. 15psi launch with a stock conv is a bunch of $%$^% Maybe with slicks and a baby turbo. My 2cents worth.

Well, without messing with the prop valve at all, my car held 7psi @ 2050rpms on the stock D5. I can get it to 2500rpm easily, and usually flash it to 2800-3000rpm when I launch. If I crank up the prop valve I would guess I will be able to hold 12-15psi at 2800rpm+. No reason why not, I flash it to there already on a regular basis.

I seem to remember TTA89 saying he flashed his stock D5 to 4000rpms on several launches, but I suspect that would cook your convertor pretty quickly.

 

[W T- Type]

I also agree with sticky tires on street tires I can get about 2# but on sticky tires I can get about 13# big difference.But If you want to launch hard just get a transbrake and launch as hard as you want to until you brake something!I haven't launched on my stageright with my new turbo I will be trying to launch around 15#'s when I get some good slicks. I want to see how tough the stock tranny really is!With my te44 I launched easy and ran 92mph in the 1/8th I can't wait till I launch hard withthe 54 turbo.When I get a good converter.

 

[Turbonut]

Originally posted by c&cgn


Well, without messing with the prop valve at all, my car held 7psi @ 2050rpms on the stock D5. I can get it to 2500rpm easily, and usually flash it to 2800-3000rpm when I launch. If I crank up the prop valve I would guess I will be able to hold 12-15psi at 2800rpm+. No reason why not, I flash it to there already on a regular basis.

I seem to remember TTA89 saying he flashed his stock D5 to 4000rpms on several launches, but I suspect that would cook your convertor pretty quickly.

You must be using the factory tach! Whatever floats your boat.