How long does it take to build boost at the line?

Blazer406

Mechanical Engineer
Joined
May 2, 2002
You guys that race at the track.....

brakes locked..... or transbrake set....... from the instant you stomp the gas.....

How many seconds does it take to build boost?

What boost level do you launch at?

I checked our datalogs and ours is way slow (to build boost) in my opinion...... just wanted to see what everyone else was getting.....
 
Every combination is different bud. No one will have the same answer.

Some can build it next to instantly some have to wait a bit.

Practice, practice, practice.
 
Every combination is different bud. No one will have the same answer.

Some can build it next to instantly some have to wait a bit.

Practice, practice, practice.

I expect to find some variation in answers..... but I also expect to find quite a few that are going to be fairly instant..... even with a larger turbo. I am fairly convinced that the converter and tuneup is key to making that boost build quickly.
 
Well, it took me about 3 seconds to come up where I wanted it with a 6131 and a 3000 stall lock up. Journal bearing turbo with .63 AR.
 
1-1.5 sec to hit 15lbs if needed

Thanks Jason,

That is where we need to be headed.

Our current spoolup tune isn't too far off..... our technique for spooling and staging is all wrong......Dusty got us headed in the right direction......on the technique....... I expect significant improvement next time out.....

We will still probably tweak the tuneup up for spoolup a small bit.... between the two maybe we can be in the 1-1.5 sec range.....
 
Well, it took me about 3 seconds to come up where I wanted it with a 6131 and a 3000 stall lock up. Journal bearing turbo with .63 AR.


Ours is slower than that..... however we were starting too early........we have to get it loaded up a little before we transbrake it and mat the gas.....
 
Here's a vid of me staging as well as Todd staging his TSO car. You can hear and see we go in pretty hot to decrease spool time.

Dusty 5.05 Todd 5.55 - Car Videos on StreetFire

My car uses an extra rev limiter when in the prestage beam. I had it set at 3600 or 3800 rpm here in the vid so it takes less than 1 second to go from 3600-4200 rpm once I roll in. A good brake system is a necessity.
 
This would dependent on the converter size, turbo size, AR size and cubic inch. If its under 2 second to 15 psi, I would say its no longer streetable since the converter will be too loose to cruise at 2300 rpm or so on the highway...with that size turbo. I would see about 3 secs to 10 psi is average in a "street combo" with a .81 a/r or any 4 bolt turbo 70MM ish..on a 231 inch motor.
 
"Matting the pedal" is going to slow spooling quite a bit. You need to feather in the throttle & get it to 0 vac or 1 psi in the pre-stage then fully stage. It will build ALOT quicker that way. It's all in the technique used.
 
"Matting the pedal" is going to slow spooling quite a bit. You need to feather in the throttle & get it to 0 vac or 1 psi in the pre-stage then fully stage. It will build ALOT quicker that way. It's all in the technique used.


We are learning........ makes perfect sense as well....

In a not-so-similar comparison.... on my own car...... I had issues getting the car to stop at the lights if I pre-staged on the footbrake.... built a lb or two of boost.... then tried to ease into the lights..... it wanted to push past the lights...... but in a transbrake car...... shouldn't be an issue at all.....
 
My converter is a little on the tighter side which makes it nice to drive. I've watched the TSM/O guys go through the Pre-stage and stage process and it's awsome.
I wish I could setup mine to do that but I have a feeling it'd take a much looser converter than I'd want to deal with on the street. I'm not willing to change as I'm more toward 90% Street and 10% strip.
As you said yourself.. it's converter/tune and Turbo size. But watching the the TSM/O guy's who have perfected staging helps us learn how to do better at the tree.
~Scott
 
"Matting the pedal" is going to slow spooling quite a bit. You need to feather in the throttle & get it to 0 vac or 1 psi in the pre-stage then fully stage. It will build ALOT quicker that way. It's all in the technique used.


Good point, that's the procedure I always used. Pre stage, build up to 0-1#, then inch into the stage, only a little over a second to my desired launch boost. Takes good brakes though, you won't be doing this on vacuum brakes (unless you're running a trans brake).
 
My car idles at 2psi.:smile: Well OK not exactly but it spools faster than instant.:) OK maybe I'm still exaggerating but it is a 4.1 with a stock turbo and 3000 stall converter. :eek: I know you said RACE car.:tongue:
 
I guess I should update..... we got a few things working together..... FINALLY.... at Reynolds.... staging technique.... etc.... and got from 2 psi.... to 12 psi.... in less than 1.5 sec........ so we made a drastic improvement.

Car wen 10.31 @ 132 or so last year at Reynolds with an iron headed 231 cu in motor...... changed some stuff up..... and a fresh GN1 headed stroker bullet.... with a new hair drier....car went 9.44 @ 146.69 mph this year.... :eek:
 
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