Steve in VC
07-13-2008, 04:45 PM
And it had nothing to do with the supercharger system. It was things I did, yet Tom supported me all the way - including figuring out what was wrong.
Flashback:
In the search of more power I tried modifying the crank position sensor on my 2000 Miata by drilling out the mounting hole to advance timing. I did it wrong, killed the crank position sensor, and both CAT's. I replaced the crank position sensor, and the car ran fine, but was throwing a CEL for a bad CAT. I have 112,000 miles, so the CAT didn't take much.
I installed the supercharger, but I was in a hurry and didn't tighten the bolts holding the top plate of the intake manifold. This gave me very strange symptoms. The transition between 2lbs to 5lbs of boost was very rough, I was running very rich in boost, and only got 8lbs of boost, not 10lbs to 11lbs. Below 2lbs of boost, the weight and belt tension of the supercharger held it down. Above 5lbs, the intake manifold cracked open bleeding air. Air that the MAF already measured, and provided fuel for. I couldn't detect this in the driveway, and only found it because Tom mentioned I was losing boost, but I had good vacuum. I had to find a "reed valve". The intake manifold fit the bill.
I fixed that, but, I was still running rich, and getting strange reading from my A/F meter.
I put the car on a dyno, only 150HP, and their instrumentation was worse than mine. The real time bar graph said I was at 10:1 A/F ratio, the A/F plot with the HP plot, said I was at 14:1!? Called Tom, he suggested pulling the plugs. #1 looked lean, 2 thru 4 looked really rich. We stopped the dyno run, and I ordered a new set of injectors (dealership $220 ea, Tom suggested a place, $60 ea!).
Installed the injectors, now #1 and #4 looked close to normal, #2 and #3 looked rich?!?
I used an ohm meter to verify the wiring and measure the signal to the injectors. The wiring looked OK (I will write trouble shooting notes in another post). Tom provided the injector duty cycle, and mine were running long.
I removed the belt, and tied the bypass open - my car still ran rich, and had a very hard time getting to redline. The problem had nothing to do with the supercharger, the ECU adding too much fuel.
I had been running really rich, so maybe the O2 sensor was failing. Talked to Tom, and the symptom fit. Changed the O2 sensor, no change.
Tom said fuel is controlled by O2, throttle position sensor, or the MAF. I have a Scangauge, and the TPS checked out OK.
My Miata is my daily driver, and Monday I have to drive to the airport. Tom packed up his spare MAF, and other test equipment ready to drive 6+ hours to do a house call (this was the second time he made the offer, this time I took him up on it).
Early Saturday morning, just before he left, he suggested I may have a plugged CAT (or two being a 2000). Fortunately, being I had killed the CAT earlier, I had what I needed to replace the exhaust system.
While Tom is driving in from AZ, I am replaced the exhaust manifold (first CAT). The car preformed better, but not good. I finished replacing the second CAT & resonator just as Tom arrived.
Went for a test drive, and it worked with only a little stumbling while I burn the crap off the plugs.
We were getting weird numbers from the wideband A/F meter. So we pulled the plugs, and they looked really good! (I will replace the wideband sensor, as being really rich probably gunked it up).
We tried to see any light through the CAT's, nothing, plugged really bad.
Before, my exhaust noise was like a jet, a loud whoosh, but no drone. Now that I fixed the CAT's, it sounds like a car again.
Hindsight being 20/20. I damaged very old CAT's with the CPS mod, I killed them by running really rich with my intake manifold "reed valve". This clogged the CAT's, so the car couldn't breath (maybe 40HP of back pressure), which caused it to run rich.
I was the first, and hopefully the last, to not bolt the top of the intake manifold down. The symptoms were really weird, but Tom hung in there, suggesting things to do, and asking the right questions until we got it working. Not the slightest sense of frustration even when he drove 12+ hours round trip yesterday only to take a test drive and check a set of spark plugs.
I couldn't be happier with the support!
And I am really happy with my Miata's performance!
Thanks Tom,
Steve in VC
Flashback:
In the search of more power I tried modifying the crank position sensor on my 2000 Miata by drilling out the mounting hole to advance timing. I did it wrong, killed the crank position sensor, and both CAT's. I replaced the crank position sensor, and the car ran fine, but was throwing a CEL for a bad CAT. I have 112,000 miles, so the CAT didn't take much.
I installed the supercharger, but I was in a hurry and didn't tighten the bolts holding the top plate of the intake manifold. This gave me very strange symptoms. The transition between 2lbs to 5lbs of boost was very rough, I was running very rich in boost, and only got 8lbs of boost, not 10lbs to 11lbs. Below 2lbs of boost, the weight and belt tension of the supercharger held it down. Above 5lbs, the intake manifold cracked open bleeding air. Air that the MAF already measured, and provided fuel for. I couldn't detect this in the driveway, and only found it because Tom mentioned I was losing boost, but I had good vacuum. I had to find a "reed valve". The intake manifold fit the bill.
I fixed that, but, I was still running rich, and getting strange reading from my A/F meter.
I put the car on a dyno, only 150HP, and their instrumentation was worse than mine. The real time bar graph said I was at 10:1 A/F ratio, the A/F plot with the HP plot, said I was at 14:1!? Called Tom, he suggested pulling the plugs. #1 looked lean, 2 thru 4 looked really rich. We stopped the dyno run, and I ordered a new set of injectors (dealership $220 ea, Tom suggested a place, $60 ea!).
Installed the injectors, now #1 and #4 looked close to normal, #2 and #3 looked rich?!?
I used an ohm meter to verify the wiring and measure the signal to the injectors. The wiring looked OK (I will write trouble shooting notes in another post). Tom provided the injector duty cycle, and mine were running long.
I removed the belt, and tied the bypass open - my car still ran rich, and had a very hard time getting to redline. The problem had nothing to do with the supercharger, the ECU adding too much fuel.
I had been running really rich, so maybe the O2 sensor was failing. Talked to Tom, and the symptom fit. Changed the O2 sensor, no change.
Tom said fuel is controlled by O2, throttle position sensor, or the MAF. I have a Scangauge, and the TPS checked out OK.
My Miata is my daily driver, and Monday I have to drive to the airport. Tom packed up his spare MAF, and other test equipment ready to drive 6+ hours to do a house call (this was the second time he made the offer, this time I took him up on it).
Early Saturday morning, just before he left, he suggested I may have a plugged CAT (or two being a 2000). Fortunately, being I had killed the CAT earlier, I had what I needed to replace the exhaust system.
While Tom is driving in from AZ, I am replaced the exhaust manifold (first CAT). The car preformed better, but not good. I finished replacing the second CAT & resonator just as Tom arrived.
Went for a test drive, and it worked with only a little stumbling while I burn the crap off the plugs.
We were getting weird numbers from the wideband A/F meter. So we pulled the plugs, and they looked really good! (I will replace the wideband sensor, as being really rich probably gunked it up).
We tried to see any light through the CAT's, nothing, plugged really bad.
Before, my exhaust noise was like a jet, a loud whoosh, but no drone. Now that I fixed the CAT's, it sounds like a car again.
Hindsight being 20/20. I damaged very old CAT's with the CPS mod, I killed them by running really rich with my intake manifold "reed valve". This clogged the CAT's, so the car couldn't breath (maybe 40HP of back pressure), which caused it to run rich.
I was the first, and hopefully the last, to not bolt the top of the intake manifold down. The symptoms were really weird, but Tom hung in there, suggesting things to do, and asking the right questions until we got it working. Not the slightest sense of frustration even when he drove 12+ hours round trip yesterday only to take a test drive and check a set of spark plugs.
I couldn't be happier with the support!
And I am really happy with my Miata's performance!
Thanks Tom,
Steve in VC