Went out to do some testing on getting the turbo to spool faster this morning. My converter is a bit tight for this turbo so I have to sit on the trans brake for about 5-6 seconds at the track to get to 7psi.

Converter stalls to 2800-3000 without boost. Normal timing on the trans brake starts at 34 degrees and then tapers off as boost builds. It takes the longest time for my car to build is just getting the first 3-4 psi, after that it builds much faster.

1st config was just having the 2 step limiter at 4600 rpms which gets to 7psi in about 5-6 seconds. In this config the limiter prevents it from building any additonal boost for more consistant launches.


I then tried setting the 2 step to 3300 and had it pull 10 degrees of timing. In neutral I could build about 1-2 psi after banging off it for 3-4 seconds. I tried pulling an addition 10 degrees of timing out of the car for a total of 20 degrees pulled, same result. Tried 30 degrees total pulled and got some back firing but didn't seem any better and I didn't play with it any more after this.

I then tried going against the foot brake with the 3300 limiter and 10 degrees of timing pulled out of the base 34, it built 3 psi after sitting on it about 4 seconds and the tires started to spin. I then tried it again with the transbrake. I was able to reach a little over 4 psi after about 4-5 seconds but it didn't want to build any more and I don't like sitting on the trans brake for long periods of time.

With the same config I decided to try building 2-3 psi on the foot brake , then engage the transbrake and turn off the 3300 rpm limiter/retard. This seemed to work pretty good. I figure I can get the 2-3 psi on the foot brake/2 step/retard while staging, then grab the trans brake and it will build boost faster and be ready to launch. I just need another limiter to stop it from over boosting on the trans brake.

Once I get this setup wired into the car I think it will build boost faster. Right now I'm playing mcguyver with holding two stripped wires together while on the foot brake to turn on the luanch control, watch the boost gate, then having to grab the trans brake button and let go of the wires. I'm probably losing at least a second in this whole process.

I'm going to continue to play with this setup to see if I can improve the spool times without going to a looser converter. Maybe I'll find a better timing combination to build the boost faster on the foot brake.

 

Maybe a silly question, but is the exhaust wrapped back to the turbo?

 

Sounds like your wanting a 3rd limiter to bring it in on the brakes to pre-spool it? You could wire in another 2step so ones on the tbrake button, and another is brake pedal or button on the wheel.

The biggest issue is pushing through your rear brakes. Also, a multi stage boost control is needed to stage properly, this way you can adjust how much boost you actually leave with.

 

If it's not Knocking, I'd try adding some timing. Will make more power letting it push the converter higher making more power compounding that into more boost quicker. That's what I have found with my truck. My 2400 NA converter pushes right out to 3300 and 10 psi pretty fast on the foot brake.

 

Already tried that. I have the car setup so that it spools as fast as I can get it to with no 2 step which means lots of timing to get the converter up higher faster. 34 degrees seems to be my sweet spot.

Having the 10 degree retard and 3300 limiter on the foot brake seems to build boost faster than just the foot brake alone and at a lower RPM. I need to do more testing.

 

lean it out and add more timing...I have 40* of timing to get my big 98mm up on boost

 

What was the thought process on going with such a tight conveter? Im in the process of doing a t-brake and im not sure what stall speed to go with.

Alex

 

good street manners, 2.75 rear gears so I don't want a lot of slip and there is no lockup. It spooled faster with the T76 I use to have on it as well. I'll probably endup going to a different converter if I ever decide to stop being so cheap.

I probably shouldn't even worry about it since I've only been to the track once this year since our track sucks so bad. Last year when I was willing to deal with their incompetance on a regular basis I was able to make over 100 passes. This year i've hardly even driven the car anywhere.

 

hmmmmm i need to watch this thread close cause on the T-brake it takes ab out the same time for mine to build about 3-4 pounds of boost.Thinking some nitrous would help but i dont know what im doing yet so ill try to get it out a few times before i pull my hair out.Sure is alot different than my maggie was...

 

Lean it out. that should put alot more EGT's in it and spool it up with more timing.

 

It sounds like you have it about there....just need a limiter on the t-brake and possibly a good boost controller....which are you using? What computer system?

 

I'm using a Lingenfelter launch controller. The fueling is controlled by a Mega Squirt II and the rest of the car is controlled by the stock ECU so that I can pass emissions.

 

I've been reading a lot on this subject with no real clear answer on what to do.

Some say put a lot of timing into it, some say try retarding it, some say richen it, some say lean it. I've tried all of these things and have run upto 40 degrees of timing on the brake with no difference compared to the current low to mid 30's timing.

The combination that I tried today is the only one that seems to be showing promise, but i'm not against trying other things. I know that I NEED the timing to create the torque and push the converter stall speed higher. My theory behind retarding on the 2step foot brake is to get more heat in the exhaust without as much load, then give back the timing (torque) and turn off the limiter to shock the converter harder so it will build flash a bit faster.

Once I do some wiring work I'll log this setup vs just the trans brake to see if it does build boost faster.

 

manual trannies generally require more fuel + less timing
auto trannies generally need less fuel + more timing

 

Jeremy... good to see that that ST80 is working out so well for ya!! Hope to see some new numbers once you get it worked out!