Question about ambient air temp and BLM's/BPW
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Question about ambient air temp and BLM's/BPW
I just got everything all installed and functioning on my AMC 360 powered Jeep. I've still got a couple of lingering questions that I haven't found the answer to yet. Hopefully they aren't too noob-ish and I hope I didn't overlook it in the stickies and searches I've done...
On a 7747 ECM, there's no ambient air temperature sensor. How does it correct for temperature extremes from below freezing all the way to 120 degree desert heat? Should I be adjusting the fuel map to get the BLM's at 128 with the ambient temp being ~70 degrees or should I adjust it a bit lean or rich? I want to have one chip for all seasons and all the places I'll take this thing.
If I set the BPW and then later find that the VE1 + VE2 values are over 100 where there are still lean BLM's, is it okay to raise the BPW? Also, is there any upper limit to the BPW value?
On a 7747 ECM, there's no ambient air temperature sensor. How does it correct for temperature extremes from below freezing all the way to 120 degree desert heat? Should I be adjusting the fuel map to get the BLM's at 128 with the ambient temp being ~70 degrees or should I adjust it a bit lean or rich? I want to have one chip for all seasons and all the places I'll take this thing.
If I set the BPW and then later find that the VE1 + VE2 values are over 100 where there are still lean BLM's, is it okay to raise the BPW? Also, is there any upper limit to the BPW value?
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From: Moorestown, NJ
Car: 88 Camaro SC
Engine: SFI'd 350
Transmission: TKO 500
Axle/Gears: 9-bolt w/ 3.23's
It doesnt, nor could it really accuratly adjust for changes in air temp with a wetflow system. Just get the BLMs within 124-132 or so and call it a day. With the stock TBI systems, itll be hard to get it to run perfect at all times. The O2 will cover for most of that, though, so getting things within the ballpark should have you covered for most conditions.
If you find that the VEs are getting too high, then adjusting the BPW is acceptable, but ideally, it should be adjusted to match your displacement and injector size.
If you find that the VEs are getting too high, then adjusting the BPW is acceptable, but ideally, it should be adjusted to match your displacement and injector size.
Joined: Jan 2005
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From: Hurst, Texas
Car: 1983 G20 Chevy
Engine: 305 TPI
Transmission: 4L60
Axle/Gears: 14 bolt with 3.07 gears
Actually you'll are overlooking a small piece of equipment used on most every stock GM TBI car/truck. The heated air cleaner setup. I stuck an IAT in mine just for the hell of it when I was running the 8746 in the Van. After the initial 5-10 minute warmup it was never under 130*, even in very cold weather it was nice and toasty in there. In fact pretty much year round it ran between 125* and 135* in there. Only on a hot summer day would I see it creep up a little and obviously in cooler weather it took a few minutes to warm up to temperature.
Also don't forget that the stock manifold has a coolant cross-over passage in it that allows coolant to heat the manifold walls/floor.
Also don't forget that the stock manifold has a coolant cross-over passage in it that allows coolant to heat the manifold walls/floor.
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