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How to launch without rolling forward?

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mini zilo

15+ Year Contributor
783
16
Jul 17, 2006
Chicago, Illinois
Ok, does anybody know the best way to use the brake booster to get the car not to roll when you stall up. After I get to about 10 psi, the car will start rolling forward a little. I have tried:

-Revving in Neutral and building vacuum to ~20 in. hg, then flooring the brakes and then putting it in drive once the RPMs fall back down, then stalling.

-Starting in drive, quickly blipping the throttle to build a little more vacuum, and then flooring the brake and then stalling.


So what is the best way to use the brake booster so that the car won't roll forward on a launch.
 
Between revving in neutral to build vacuum and holding the e-brake there is nothing more you can do.

Well if you get a bigger turbo you wont build as much boost at the line if you call that a fix...:)
 
Just use the E-brake. Hold It tell your ready to launch then let off it.

He already does that...

He ran consistent 1.7-1.8's and 12.6 -> 12.8's all day on Saturday :thumb:

I felt a 15+psi launch, it didn't seem to be moving forward either all day. Perhaps you wore out your brakes past their capabilities after all of those 109mph shutdowns :cool:

Time for some slotted brakes, SS lines and that IPT stall
 
He already does that...

He ran consistent 1.7-1.8's and 12.6 -> 12.8's all day on Saturday :thumb:

I felt a 15+psi launch, it didn't seem to be moving forward either all day. Perhaps you wore out your brakes past their capabilities after all of those 109mph shutdowns :cool:

Time for some slotted brakes, SS lines and that IPT stall


Just wondering how much boost was he running on the e3 16g to make those kind of passed on the auto. Was it on race or pump gas also?
 
If you are using the E brake while doing the neutral rev then you have exceeded your current brake systems holding capacity.

Issues like this will either need a better system ( calipers etc ), a 4 wheel line lock ( not recommended ) a more powerful braking system ( hydroboost, and they do not have a kit for the DSM's ) or a trans brake ( not available either ).

I would consider a bigger front braking system so your all around braking is better anyways.
 
Just wondering how much boost was he running on the e3 16g to make those kind of passed on the auto. Was it on race or pump gas also?

I was running 20 PSI of boost on pump gas for the 12.7-12.8 runs. I was running 24 psi (on a crap race gas tune) on 100 octane for the 12.6 run. I think if I lean it out to 12.0 a/f ratio on the 100 octane and run 25 psi of boost I can pull something lower than a 12.6. I was building about 18 psi off the line.
 
I was running 20 PSI of boost on pump gas for the 12.7-12.8 runs. I was running 24 psi (on a crap race gas tune) on 100 octane for the 12.6 run. I think if I lean it out to 12.0 a/f ratio on the 100 octane and run 25 psi of boost I can pull something lower than a 12.6. I was building about 18 psi off the line.

Thanx for the info. Just wanted to know what others were getting with your style setup. I am running a ported s16g so only expecting low 13's at the track in 2 weeks. To get back on topic though I was having the same creeping problem with my car till I upgraded to stainless lines all around and carbon fiber pads all around.
 
Hey Zilo, what RPM are you leaving at with the 18 launch??

You must be running on low timing, but what was the MPH on the 12.8 runs vs. the 12.6 runs??

I personally tune around the 11.8-12.0 area on my mixed race gas runs. No need to compensate for knock by running rich like most pump gasers do.
 
Oh, you ran 4psi more boost on a similar 60ft and your MPH didn't change??

What rpm did you go through the traps at with the 109MPH?

Something is choking off power up top, ignition, boost leak, intake, turbo out of steam. If you are on the stock side mount, intake, cams etc you probably have a ton of backpressure just itching to free up so you can make some top end power there. Even though your turbo shows only 24psi, it could be pushing the equivalent of 30psi on stock components. This is why many see madd power gains on FMIC's, Intakes, Cams etc.
 
Get a real brake kit. I offer 12.2 brake kits and 11.75 brake kits with wilwood parts specifically cause of this problem with auto's. And at a reasonable cost unlike everyone else charges.
 
I wouldn't go to bigger brakes, this just allows you to load the trans gears harder - which can strip the teeth on the center diff gear. All but one gear failure I've seen in autos are related to too much torque being held with the brakes. If the car spins the tires just as you let off the brakes, it is probably too much torque and you should adjust the launch via timing.

The best launch setup is a 2-step at the proper rpm to spin the tires the right amount for the first few feet. Then, set boost at launch via pulling timing at the 2-step (like via anti-lag). I actually set launch boost on my car with the wastegate so I can get a little tighter control than just with timing adjustments. On a really bad track I was in the low 1.5's, on a normal back track I'm in the mid-low 1.4's and on a good track mid-1.3's.

Kevin

Also, I forgot to add I'm using a vacuum pump to keep the brakes working as I stage the car. This doesn't make much of a difference until you start modulating the brakes to move into the staging beams. With the vacuum pump the brakes keep working, but the torque they can hold is the same as when you still have vacuum with the conventional setup.

Kevin
 
So doing this method is there a real reason to get a higher then stock stall on a mild set up like a 50 trim or so???


Will the stock convertor be able to tolerate it???
 
The converter still needs to be loose enough to spool the turbo loaded against the converter. You won't be able to spool at gt42 on a stock converter or anything crazy like that. A 50-trim will also need a looser converter than stock.

Kevin
 
Maybe you should try heating the brakes up if you have perfomance pads? Do some hard stops befor you try and launch?


Stock breaks, just make sure there up to normal temp?

I suggest a line lock man, best way to go




FYI

I used to launch my 5speed car with the Ebrake up, its a tricky and takes a bit to get used to but I lauched so fast and smooth like that. Thats another reason, i didnt have alot of trans problems drove the car good and didnt shock the awd


But it did see some full rev limiter launchs for awd burnouts
 
I wouldn't go to bigger brakes, this just allows you to load the trans gears harder - which can strip the teeth on the center diff gear. All but one gear failure I've seen in autos are related to too much torque being held with the brakes. If the car spins the tires just as you let off the brakes, it is probably too much torque and you should adjust the launch via timing.

The best launch setup is a 2-step at the proper rpm to spin the tires the right amount for the first few feet. Then, set boost at launch via pulling timing at the 2-step (like via anti-lag). I actually set launch boost on my car with the wastegate so I can get a little tighter control than just with timing adjustments. On a really bad track I was in the low 1.5's, on a normal back track I'm in the mid-low 1.4's and on a good track mid-1.3's.

Kevin

Also, I forgot to add I'm using a vacuum pump to keep the brakes working as I stage the car. This doesn't make much of a difference until you start modulating the brakes to move into the staging beams. With the vacuum pump the brakes keep working, but the torque they can hold is the same as when you still have vacuum with the conventional setup.

Kevin

Not sure if I'm the only one that's confused here but you're saying that if the tires spin when letting off the brakes it's probably too much torque. But then right after that you're saying to spin the tires the first few feet. So I totally don't get what you're saying here. Sorry if I'm just being a bit slow this morning.
 
He was saying if your in gear on the throttle and the brakes at the same time(brake boosting) and as soon as you let off the brakes of the tires started to spin you were holding too much torque on the trans. He suggested using two step and just launching without being on gas in gear.
 
Got it. Thanks for the clarification. Imagine loading up on the brakes AND the gas at the same time would put too much stress on the transmission anyway.
 
Reading over that again, that still wouldn't make sense because the turbo isn't going to be spooled at say 1k rpm's without hitting the gas. Can't get the converter to stall up to whatever it's for, etc, without hitting the gas. So what am I missing here?
 
This is digging back about 13 years! The target at launch is to just roll the tires over some. If it stands up on the tire with a lot of spin right at the hit, you are running too much 2-step rpm. Since this was originally written, I’ve seen a bunch of cars leave very strong at lower rpm and with a little more boost. Torque on the gears during the brake torque is related to rpm only, so this is a bit easier on parts.

You have to be loaded up and boost built for a decent launch. I was trying to convey a reasonable amount of load that could launch decently and not immediately break parts.

A couple things do still stand as reasonable. The rpm where the car makes 10psi with a normal tune (2.0l) is a reasonable start point for the 2-step. On the precision converters this is somewhere in the 4500rpm range. The tighter converters have less torque multiplication and need a little more rpm than the looser ones for the same torque (I know that sounds backwards), but they are all in the same general rpm range. Seems like stock and restalls are in the 3500-4000rpm range.
 
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