406_Talon
Supporting Member
- 116
- 13
- Jun 30, 2014
-
Kalispell,
Montana
Hello,
This is a "crosspost" with my post on the ECMlink forums, I thought I'd ask here as well to maximize exposure.
I am having some issues with my car, it's a 1995 GSX with a basic 2.0 7 bolt, Wiseco 8.5:1 pistons/eagle rods and crank bottom end, (built by me - first engine I've ever built
Attached is a log I took today while trying to get my car to idle with all parameters in line. I managed to get my ISC position to oscillate around 30, and my trims are pretty close, but my airflowperrev is way high at .4-.45 and my vacuum is consistently low, in the area of 10-12. Car idles fine and controls RPM, and it seems to run fine and drive well in closed loop (I've barely driven it - maybe 5 miles and 20 minutes just putting at varied rpm in closed loop to shake it down) I tried blocking the line to the aftermarket BOV as well, to see if it was leaking internally and affecting vacuum, it did not affect it at all.
Also attached is a second log, where I tried to dial things in further, I reduced VE in the Idle cells, then I dialed fuel back in to get Combined FT back in line. I got everything fairly close, but my Injector settings are way off from their calculated values... Can anyone offer any clarification on why this would be, if it is correct? Am I just compensating for low vacuum by pulling out fuel - it seems like that's not the right thing to do...?
Based on the low Vacuum, and some reading I've done here in a few threads, I'm concerned that I may have a mechanical issue. One suggestion I saw to a similar issue was that the exhaust cam out of time. I also saw suggestions that incorrect ignition timing (CAS adjustment) can cause this but I have a 95-96 style CAS, so I think I can eliminate that. I have three specific questions, but I would welcome any and all suggestions.
1. If the exhaust cam is to blame, would I likely need to retard or advance it? I have adjustable gears, but I installed the cams straight up as I was unable to find a degree wheel that would work. I can't really work out in my head which way would increase vacuum...
2. The motor has barely been run, I'm not totally confident that the rings are fully seated this point, could that be a contributing factor to my low vacuum? If that is the case should I run the engine more or drive more to seat the rings? I was told it would take 100 miles to get the rings fully seated, and wait that long to do a compression test to ensure accurate results...
3. Could my lower compression pistons and somewhat aggressive cams be causing this issue? Perhaps my VE is still a bit high in this area at .58ish?
Any help is appreciated, I'm really at my wit's end with this project haha.
This is a "crosspost" with my post on the ECMlink forums, I thought I'd ask here as well to maximize exposure.
I am having some issues with my car, it's a 1995 GSX with a basic 2.0 7 bolt, Wiseco 8.5:1 pistons/eagle rods and crank bottom end, (built by me - first engine I've ever built
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), GSC S2's & supporting valve train stuff, MLS HG, PTE 5862 and a FMIC running in SD with Mitsu MAP and GM IATwith Precision WG and GFB BOV. Stock Intake manifold and stock 2g TB. PCV system run correctly with 2 sealed catch cans. Passed a BLT with flying colors before I started the motor, but I could do another one. (All details in profile are up to date)Attached is a log I took today while trying to get my car to idle with all parameters in line. I managed to get my ISC position to oscillate around 30, and my trims are pretty close, but my airflowperrev is way high at .4-.45 and my vacuum is consistently low, in the area of 10-12. Car idles fine and controls RPM, and it seems to run fine and drive well in closed loop (I've barely driven it - maybe 5 miles and 20 minutes just putting at varied rpm in closed loop to shake it down) I tried blocking the line to the aftermarket BOV as well, to see if it was leaking internally and affecting vacuum, it did not affect it at all.
Also attached is a second log, where I tried to dial things in further, I reduced VE in the Idle cells, then I dialed fuel back in to get Combined FT back in line. I got everything fairly close, but my Injector settings are way off from their calculated values... Can anyone offer any clarification on why this would be, if it is correct? Am I just compensating for low vacuum by pulling out fuel - it seems like that's not the right thing to do...?
Based on the low Vacuum, and some reading I've done here in a few threads, I'm concerned that I may have a mechanical issue. One suggestion I saw to a similar issue was that the exhaust cam out of time. I also saw suggestions that incorrect ignition timing (CAS adjustment) can cause this but I have a 95-96 style CAS, so I think I can eliminate that. I have three specific questions, but I would welcome any and all suggestions.
1. If the exhaust cam is to blame, would I likely need to retard or advance it? I have adjustable gears, but I installed the cams straight up as I was unable to find a degree wheel that would work. I can't really work out in my head which way would increase vacuum...
2. The motor has barely been run, I'm not totally confident that the rings are fully seated this point, could that be a contributing factor to my low vacuum? If that is the case should I run the engine more or drive more to seat the rings? I was told it would take 100 miles to get the rings fully seated, and wait that long to do a compression test to ensure accurate results...
3. Could my lower compression pistons and somewhat aggressive cams be causing this issue? Perhaps my VE is still a bit high in this area at .58ish?
Any help is appreciated, I'm really at my wit's end with this project haha.