1979-1993 & 94 Conv [Subscribe to Daily Digest] |
I have a 2.1 liter LPT car (well, not really light pressure; it's up to about 11 psi w/~9.5:1 CR, no APC). I put a wideband O2 sensor on it to see how the original n/a LH2.2 ECU handled fuel. The wideband datalogging revealed that the n/a ECU *does not* richen the fuel mixture under boost -- instead, it will keep the AFR at 14.7:1 all the way up to WOT. This is a problem: you can run *considerable* boost before you trip the WOT switch, which is why running the n/a ECU isn't smart -- stoichiometric ratios on a turbo car under boost are too lean and thus potentially harmful, especially if you're running without an APC.
Adding Turbo injectors and a 3.0 bar FPR (giving 23#/hr, up from 19#/hr)*does not help* -- the n/a ECU still keeps the AFR at stoichiometric until WOT. (In fact, I tested the AFR with just such a set-up. Oh, the car's stock, narrow-band O2 sensor was brand new.)
Given the above findings, I personally would not run an LPT car with an n/a ECU. If you have LH2.2 or 2.4, consider swapping in a version from a Turbo. If you have a B212 car, I believe you can swap in an LH2.4.2 box for a turbo engine from a 9000. In all honesty, I have not tested a 900 Turbo ECU because I run a Volvo 740 Turbo ECU, which does, in fact, give a good, richened AFR on boost, but I can't believe that Saab engineers wouldn't richen the mixture on boost on their Turbo ECUs.
Regarding Timing -- I have had trouble running EZK together with a turbo distributor: I get predetonation at a couple PSI. This may be due to problems with my car's EZK system, or it may not. In any case, if you run both a Turbo dist. and EZK, you'll want to ensure you aren't getting predet. You can't hear it with the windows up.
Provided there are no problems with the EZK, my theory is that, as revs climb, EZK advances timing. Meanwhile, my little TE05 is doing a great job stuffing the cylinders with air, which, unfortunately, is a bit warm, even with an IC. Load is also high at this point. So, as EZK is advancing, the vacuum retard capsule on the Turbo distributor is starting to retard timing. The problem, I theorize, is that the EZK has advanced so far that the retarding turbo distributor isn't retarding it enough for the boost.
Anyway, these are just some things to consider...
posted by 128.95.20...
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