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Slow spool?

 
Old 01-26-2009, 09:10 PM
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Default Slow spool?

This is my first turbo car so I'm still getting accustomed to the whole spool concept. I'm just getting my car tuned and running right, but from what I've read it doesn't seem to be spooling as low as it should. I took a datalog and graphed it, does it look right? If it is spooling slower than it should any idea what could be causing it? This is a 4th gear pull and not significantly different than any other gear. X axis is RPMs, Y Axis is PSI.

boost.jpg

Excel file is also attached if you want to look at the individual values.

Specs on the car are:
'95 1.8 motor
BEGI S3 turbo kit
GT2560 turbo
Megasquirt PNP ecu
Cheap Ebay MBC
Currently running an 18" long 2.5" straitpipe off the downpipe

Any other questions let me know and I'll do my best to answer.
Attached Files
File Type: xls
boost.xls (840 Bytes, 7 views)
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Old 01-26-2009, 09:16 PM
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spool is WAYY late....is the wga tight?
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Old 01-26-2009, 09:22 PM
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wastegate is too loose
boost leak
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Old 01-26-2009, 09:37 PM
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When I first installed the kit I was hitting boost cut really bad, even up to 12psi. I had to adjust the wastegate actuator all the way out in order for it to keep boost right at 10psi. The wastegate lever thing (god I suck at this) is perpendicular to the motor when it's closed, which I'm assuming is correct.

I'll go double check for a boost leak. Any other recommendations?
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Old 01-26-2009, 09:39 PM
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tighten the wga....thats whats causing it
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Old 01-26-2009, 10:03 PM
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edit: nevermind, i wont advise it for a first turbo car.
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Old 01-26-2009, 11:21 PM
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Originally Posted by pdexta View Post
When I first installed the kit I was hitting boost cut really bad, even up to 12psi. I had to adjust the wastegate actuator all the way out in order for it to keep boost right at 10psi. The wastegate lever thing (god I suck at this) is perpendicular to the motor when it's closed, which I'm assuming is correct.

I'll go double check for a boost leak. Any other recommendations?
Sounds like terrible boost creep that you solved by adjusting the wastegate so far out that the turbo never fully spools.

Terms:
Wastegate can is the big round thing that fills with boost
Wastegate actuator rod is the thing that pokes out of the can
Wastegate lever arm is the thing that's on the turbo

The actuator rod should be lightly pulling the lever arm closed when you're off boost. To check this, pull the rod off the lever arm. You should have to tension the rod very slightly to get it to snap over the lever arm. If you pull it off, and you can close the lever arm more, you've got a problem.

If you do that, and you get boost overshoot, you need to port the wastegate.
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Basically I've come over to the camp of "If something is a reliability problem on the track, just ask Andrew and do what he says".
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Old 01-26-2009, 11:44 PM
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Originally Posted by 18psi View Post
tighten the wga....thats whats causing it
Wow, that seems to have solved the problem, and I do believe I picked up a little midrange power.

[email protected] > [email protected]

Thanks for the help guys. I'd never figure this stuff out on my own.
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Old 01-27-2009, 12:00 AM
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Thats awesome.. Hell of alot better now huh!!!
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Old 01-27-2009, 12:43 AM
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for comparison, post a datalog of a 4th gear pull now.
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Old 01-27-2009, 12:51 AM
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did you try running without the MBC at all?
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Old 01-27-2009, 12:54 AM
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Turbos definitely spool better when the wastegate is shut.
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Old 01-27-2009, 08:40 AM
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Originally Posted by ThePass View Post
for comparison, post a datalog of a 4th gear pull now.
Will do. Unfortauntely I blew the end of my boost controller off, no idea how I managed to do that, but I need to get a new one. Hopefully tonight I can get another graph up. It's definitely a huge improvement.

Originally Posted by akaryrye View Post
did you try running without the MBC at all?
After breaking the boost controller I played with it a bit and got it to run right at 8psi.

Originally Posted by patsmx5 View Post
Turbos definitely spool better when the wastegate is shut.
Most definitely.
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Old 01-27-2009, 11:17 AM
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ya that boost controller is designed to raise the boost, so if you ever get in that situation again, first thing to do is to take it off.
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Old 01-27-2009, 11:36 AM
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Originally Posted by akaryrye View Post
ya that boost controller is designed to raise the boost, so if you ever get in that situation again, first thing to do is to take it off.
I was originally hitting boost cut at 12psi w/o a boost controller. I adjusted the wastegate actuator out (obviously too much) and later installed the boost controller to raise boost back up to where I wanted.
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Old 02-06-2009, 12:51 PM
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Alright, I'm back again w/ more stupid questions....

The night I tightened the wastegate the car was awesome for a few minutes, then I the adjuster on my boost controller apparently came loose and blew the end off and the the spring went flying. I've been through a couple other boost controllers now but everytime I'm back to the same old problem of building boost very slowly.

The wastegate is tightened down now and I've checked thoroughly for boost leaks. I haven't tested for leaks yet but I'm 99.9% sure it isn't leaking anywhere. I checked my wastegate actuator and it does not hold suction (I can suck on the vacuum hose to it and it doesn't seal). Is it supposed to do that, or could that be my problem? 1 step forward and 2 steps back I guess. Again, any help is greatly appreciated.
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Old 02-06-2009, 02:00 PM
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Originally Posted by patsmx5 View Post
Turbos definitely spool better when the wastegate is shut.
Thats just a myth from the land of China. They flow better with the wastegate open.
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Old 02-06-2009, 10:03 PM
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Originally Posted by pdexta View Post
Alright, I'm back again w/ more stupid questions....

The night I tightened the wastegate the car was awesome for a few minutes, then I the adjuster on my boost controller apparently came loose and blew the end off and the the spring went flying. I've been through a couple other boost controllers now but everytime I'm back to the same old problem of building boost very slowly.

The wastegate is tightened down now and I've checked thoroughly for boost leaks. I haven't tested for leaks yet but I'm 99.9% sure it isn't leaking anywhere. I checked my wastegate actuator and it does not hold suction (I can suck on the vacuum hose to it and it doesn't seal). Is it supposed to do that, or could that be my problem? 1 step forward and 2 steps back I guess. Again, any help is greatly appreciated.
What did you connect the wastegate actuator vacuum line to in the intake system? Is it before or after the throttle?
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Old 02-07-2009, 02:18 PM
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Originally Posted by NA6C-Guy View Post
Thats just a myth from the land of China. They flow better with the wastegate open.
He said "spool", not flow.
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Old 02-08-2009, 02:22 PM
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Originally Posted by ZX-Tex View Post
What did you connect the wastegate actuator vacuum line to in the intake system? Is it before or after the throttle?
It's right off the turbo, way before the throttle.
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