Lets talking launching with boosted cars
I have a simple question..
I’m a blower guy coming over to the turbo world with very lil experience with turbos.
my f1 gto could never get anywhere close to seeing positive pressure in the manifold, I know the blower will act different but how does the turbo make any boost with bov being open as I dont see how the car could ever see enough throttle on the foot brake to build boost on the line.
Please help me understand how you build boost on the foot brake, with out pushing through the brakes
I’m a blower guy coming over to the turbo world with very lil experience with turbos.
my f1 gto could never get anywhere close to seeing positive pressure in the manifold, I know the blower will act different but how does the turbo make any boost with bov being open as I dont see how the car could ever see enough throttle on the foot brake to build boost on the line.
Please help me understand how you build boost on the foot brake, with out pushing through the brakes
OP try your 3 step(I'm guessing this is the one on the footbrake) at 3200 and get 2-4psi built. Set the 2 step(transbrake rpm limiter) at 3600-3800rpm and leave on 6-7psi.
As Dave was saying I don't know how you have your tune set-up and if you're just using the main timing tables for timing or if you're using some of the other adder tables that can add timing only during set circumstances in the ECU so I don't know how much of a spread you will need between footbrake rpm and transbrake rpm to get that boost built. Most cars that run race gas that can get aggressive with timing can have it all built within 5 seconds. You being on E85 you can most likely do the same as them unless your camshaft is stupid early on the IVC event.
Let me know if you have any more questions. I think you have a good running car and that it wont take much more to get it into the 5's.
There are a couple things you need to keep an eye on. Its not the transbrake RPM and boost as much as the RPM/boost you see when you get wheel speed. On our car, there is a .18-.22 delay from when the button gets released and wheel speed hits.
On a 1.29 sixty what is your wheel speed at 0.50, 1.0 and 1.29 ?
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Thread Starter
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From: Thomasboro, ILL
OP: If you can get the car to leave on more initial boost(more shaft speed) it will make a big difference on how quickly the rest will come in. I've got a 88 on a 5.3l engine and it has been on the bumper leaving at 12 psi or so. If I am track-tion limited and have to leave on less boost initially the car will leave similar to yours.
Charge pipes,, and DP are double wrapped. 2.25" charge, and 5" dp
Camshaft makes a lot of difference also.
OP try your 3 step(I'm guessing this is the one on the footbrake) at 3200 and get 2-4psi built. Set the 2 step(transbrake rpm limiter) at 3600-3800rpm and leave on 6-7psi.
As Dave was saying I don't know how you have your tune set-up and if you're just using the main timing tables for timing or if you're using some of the other adder tables that can add timing only during set circumstances in the ECU so I don't know how much of a spread you will need between footbrake rpm and transbrake rpm to get that boost built. Most cars that run race gas that can get aggressive with timing can have it all built within 5 seconds. You being on E85 you can most likely do the same as them unless your camshaft is stupid early on the IVC event.
Let me know if you have any more questions. I think you have a good running car and that it wont take much more to get it into the 5's.
OP try your 3 step(I'm guessing this is the one on the footbrake) at 3200 and get 2-4psi built. Set the 2 step(transbrake rpm limiter) at 3600-3800rpm and leave on 6-7psi.
As Dave was saying I don't know how you have your tune set-up and if you're just using the main timing tables for timing or if you're using some of the other adder tables that can add timing only during set circumstances in the ECU so I don't know how much of a spread you will need between footbrake rpm and transbrake rpm to get that boost built. Most cars that run race gas that can get aggressive with timing can have it all built within 5 seconds. You being on E85 you can most likely do the same as them unless your camshaft is stupid early on the IVC event.
Let me know if you have any more questions. I think you have a good running car and that it wont take much more to get it into the 5's.
Probably only takes samples around .050 (20 times per second) or .042 second (24 times per second) frames.....
Kinda need to set a goal. Looks like you might be on 325's and that was at NLR right?
Let's say 1.30 is the goal. Back in the day when I had my combo I really didn't know how to tune it, but helping on Andy's car I have a better sense of how it all relates.
What size turbo is that, I looked it up but is it a 94mm T6?
I think you want to leave on as much power as you can hook PLUS whatever rpm helps you get into your power band. If for example that turbo is laggy and doesn't turn on until 5500, you'd want to leave higher rather than lower rpm-wise.
Let's say 1.30 is the goal. Back in the day when I had my combo I really didn't know how to tune it, but helping on Andy's car I have a better sense of how it all relates.
What size turbo is that, I looked it up but is it a 94mm T6?
I think you want to leave on as much power as you can hook PLUS whatever rpm helps you get into your power band. If for example that turbo is laggy and doesn't turn on until 5500, you'd want to leave higher rather than lower rpm-wise.
Are your logging sample rate set to .02 seconds?
The rear tire size, rear gear ratio, engine torque, converter, and electronics all play a role in the time delay from when you release the TB and when you see wheel speed.
Kinda need to set a goal. Looks like you might be on 325's and that was at NLR right?
Let's say 1.30 is the goal. Back in the day when I had my combo I really didn't know how to tune it, but helping on Andy's car I have a better sense of how it all relates.
What size turbo is that, I looked it up but is it a 94mm T6?
I think you want to leave on as much power as you can hook PLUS whatever rpm helps you get into your power band. If for example that turbo is laggy and doesn't turn on until 5500, you'd want to leave higher rather than lower rpm-wise.
Let's say 1.30 is the goal. Back in the day when I had my combo I really didn't know how to tune it, but helping on Andy's car I have a better sense of how it all relates.
What size turbo is that, I looked it up but is it a 94mm T6?
I think you want to leave on as much power as you can hook PLUS whatever rpm helps you get into your power band. If for example that turbo is laggy and doesn't turn on until 5500, you'd want to leave higher rather than lower rpm-wise.
As long as he can build enough boost at a low enough rpm that when he releases the trans brake flashes it into it's power band it will leave just fine and won't be leaving much if any on the table.
I've always found letting the rpm's run up to the converters lock up point is faster than loading it up on the transbrake and letting it bog basically when it leaves or flat line the rpm's for 60-80' and then the rpm's rise.
I leave the line at 3-4psi off the trans brake around 4400rpm. Usually cut around 1.5 sixty foots but have seen a few 1.4X's. I need to get a BMR extreme sway bar because I feel that the stock sway bar is my limitiing factor when it comes to suspension.
Adjustable shocks?
Are you using a two step?
I have Hal QA-1 single adj. all around with the rears on 2-4 depending on track cond. and the fronts on 3-5.
No two step.
If you had a two step and were able to launch it around 3200-3400rpm you'd have some flash in the converter allowing it to flash to the lock up point of the converter you are using and accelerate a lot faster and not have that lag or flat spot for however long it does.
Yea without the two step on the transbrake you are loading the converter all the way up and I'd bet that the rpm's don't really start to rise until you get past the 60' mark do they?
If you had a two step and were able to launch it around 3200-3400rpm you'd have some flash in the converter allowing it to flash to the lock up point of the converter you are using and accelerate a lot faster and not have that lag or flat spot for however long it does.
If you had a two step and were able to launch it around 3200-3400rpm you'd have some flash in the converter allowing it to flash to the lock up point of the converter you are using and accelerate a lot faster and not have that lag or flat spot for however long it does.
http://youtu.be/ZiD-KB4WNXw
Last edited by Packy; Jul 6, 2012 at 09:25 PM.