1979-1993 & 94 Conv [Subscribe to Daily Digest] |
Mike,
You've modified your car much more than mine but several things popped into
my head as I read your post.
First are you using magnecor wires? I've tried both Bosch and Boge and found that magnecor wires work the best. I suspect that the heat from the turbo causes the wires to break down. At higher boost levels it's more difficult for the spark to jump the spark gap, possibly causing your problem.
On my car I found that if I disconnected the PVC tube from the air cleaner box and let it exhaust out into the atmosphere the car ran much stronger. I plugged the nipple that it connected to and I'm currently working on an inline filter. I have a theory that the crankcase gases are HOT and contain oil vapor which might cause the O2 sensor to indicate that it is richer than it really is. Additionally, the mass flow rate of the HOT crankcase gases increases with boost pressure so this effect might be more pronounced at higher boost levels. Give it a try, I helped me out.
You mentioned that you don't have any vacuum/boost leaks. Can you be
certain about that? That stupid little check valve on the vacuum tank could be leaking at high boost pressures, mine did. I've often ruled out vacuum leaks only to find out much later that I had one. One area that I often over looked was the connection between at the throttle body and at the turbo. I found a manufacturing defects on my tube, extra flashing from the casting that wasn't properly ground off, that were causing leaks. I often connect a voltmeter to the O2 sensor and monitor it while I spray flammable liquids on all the potential vacuum/boost leaks. Additionally, I connect a high pressure source (10+psi) to all the lines running away from the intake manifold and look for a leak down. I recently found a crack in a line, that has been causing me grief for months. I'm now going with silicon. Another possiblility is the injector seals.
I'd look at your duty cycle and make sure that for rpm >3700 it stays around 75% What boost pressure are you trying to get to?
Good Luck and let us know what you find
Todd
posted by 128.110....
, Wed, 17 Oct 2001 18:41:19
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