[Subscribe to Daily Digest] |
In the post below, you mentioned that you hoped to go back to the manifold pressure tap but somehow prevent the spikes. I don't think that temporarily bleeding the MAP or electronically tricking it is the best idea -- the spike would still be there. I can't imagine that such overboost spikes would be good for the engine over a long period of time. And then there's the fuel considerations...
What you'd really want to do is find a way for the wastegate to begin opening a small amount before the pressure reaches your set point. (This is the way that the expensive fuzzy-logic electronic controlers work.) You may recall my experiments with the releif/regulator valves last summer. What I was thinking is that you might be able to use a pressure regulator downstream of your present MBC (which is really just a pressure releif valve). Say, for example, that you want boost at 14.7psi max. First, set the MBC so boost peaks at 13.7psi (or whatever setting eliminates the boost spikes). Now, pull the MBC and install the regulator in its place. Set the regulator so that max boost reaches 14.7psi. (Keep in mind that spool up will be very slow with just the regulator, but you will reach a maximum eventually). Finally, put the MBC back in behind the regulator. With this setup, boost will run up to 13.7 with the wastegate completely closed. It will open up past 13.7, but the pressure regulator will ensure that max boost stays at 14.7psi. If you're still getting pressure spikes, dial back the MBC further. The MBC now controls only the rate of spoolup while the regulator controls max boost.
I can't say how well this will work as I've never tried using the manifold pressure tap, but it should in theory. I would recommend that, if you try it, you find a decent (all-metal) regulator. The plastic one I have is not accurate enough, and I don't think it likes the under-hood heat either.
Another option would be be to build a small logic circuit that's fed off pressure sensor at the manifold (could actually use the MAP, I have the voltage specs for it) and drives the stock BPC (which I also have the specs for).
posted by 128.2.111.1...
No Site Registration is Required to Post - Site Membership is optional (Member Features List), but helps to keep the site online
for all Saabers. If the site helps you, please consider helping the site by becoming a member.
 |
 |
 |
 |
 |
