Car cuts at high boost.
#1
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Hey guys i'm having problems with my car when it comes into high boost. Normally around 10psi but higher if im easier on the throttle. The car was fine last year with the same set-up. My boost cut is at 230 kpa, plugs are gapped all the way down to 22. Also im running toyota cops so ive ruled spark strength out i would think. Could it be a bad ground? I can post a data log if someone tells me how
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#2
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I've been out of the game for a while, but cutting out at high boost means one of two things:
- AFR is waaay off
- Spark blowing out
If your AFR-meter reads OK, then you're not sparking. Combustible mixture + spark = explosion. One of those two missing means no power.
Did you check your AFR? I would assume so....
Of course on my turboed BMW535i I had a problem like that and couldn't figure it out for weeks. At WOT it would sometimes cut out and in and out and in....
Eventually I realized that the old style fuse for the fuel pump was not clamped properly any more. The holder was bent open slightly. Under strong acceleration the fuse moved back a bit and lost contact. That would stop the flow of fuel and the car to decelerate. That would cause the fuse to move forward again, closing the circuit. Fuel starts flowing again, the car accelerates and the whole thing starts over again.
So it MAY be something really weird, but it is likely just the spark or the AFR.
- AFR is waaay off
- Spark blowing out
If your AFR-meter reads OK, then you're not sparking. Combustible mixture + spark = explosion. One of those two missing means no power.
Did you check your AFR? I would assume so....
Of course on my turboed BMW535i I had a problem like that and couldn't figure it out for weeks. At WOT it would sometimes cut out and in and out and in....
Eventually I realized that the old style fuse for the fuel pump was not clamped properly any more. The holder was bent open slightly. Under strong acceleration the fuse moved back a bit and lost contact. That would stop the flow of fuel and the car to decelerate. That would cause the fuse to move forward again, closing the circuit. Fuel starts flowing again, the car accelerates and the whole thing starts over again.
So it MAY be something really weird, but it is likely just the spark or the AFR.
#4
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If it leans out slowly and then you lose power, you're not getting enough fuel.
#5
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I'm having the same problem - full boost at sub 6krpm or less than about 10psi above 6k rpm is fine. Get above 6k with over about 10psi and I start running into misfire problems. Planning on replacing my spark plugs, and if that doesn't work, I'm going to buy a new COP and start searching for the bad one.
#11
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Hey guys sorry for no reply but im still having problems. It doesnt seem to be the amount of boost being a issue but more when the car is under heavy load. For example its bad if im cruising in 5th on the highway and lean into it hard it cuts out. I have switched coils, rewired the cops, re-did all the grounds and tried 2 sets of plugs. I'm currently running the non-resistor v power plugs on flyin miatas site. I had the same set-up last year with no issues. All i changed over the winter was a new clutch/flywheel and installed a resistor for the tach. Do i need a capacitor wired in if im running a resistor? Any help is appreciated i already bent a rod because of this.. :(
#12
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Hi Brad,
A few suggestions / questions:
- What is your AFR immediately before it cuts out?
- Does it stutter or cut out completely?
- When you increase throttle slowly in 5th, does it still cut out, or can you get all the way to full boost?
When you go from cruise to WOT, (leaning into it hard) the manifold pressure increases rapidly. This causes vaporized fuel to deposit on the intake runners which in turn causes a short ultra-lean condition. That's why you need accel-enrichment.
Suggestions:
- To make sure it's not boost related, wire open your wastegate. If it goes away it's boost related
- If you see a significant change in AFR, compensate for it
Good luck!
A few suggestions / questions:
- What is your AFR immediately before it cuts out?
- Does it stutter or cut out completely?
- When you increase throttle slowly in 5th, does it still cut out, or can you get all the way to full boost?
When you go from cruise to WOT, (leaning into it hard) the manifold pressure increases rapidly. This causes vaporized fuel to deposit on the intake runners which in turn causes a short ultra-lean condition. That's why you need accel-enrichment.
Suggestions:
- To make sure it's not boost related, wire open your wastegate. If it goes away it's boost related
- If you see a significant change in AFR, compensate for it
Good luck!
#14
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Check battery voltage on your datalogs. Maybe a loose alternator wire from the clutch job. Also, how are your COPs wired? Specifically, where are your grounds going? This sounds like a bad/intermittent electrical connection to me. Also, what firmware are you running?
Spark cutting out alone shouldn't bend rods unless spark is coming in when its not supposed to. Now, if you lose a substantial amount of electrical power across the board and your injectors cut out intermittently, that will break things by causing a temporarily lean condition that might not even show up in AFR readings, especially at the log rate of the MS. Check that voltage through several logs. Maybe you'll catch a big dip in one of them. Then check your main wiring: alternator +, battery + and -, power connections on your MS board, injector harness to main harness plug, ECU plug, etc.
Spark cutting out alone shouldn't bend rods unless spark is coming in when its not supposed to. Now, if you lose a substantial amount of electrical power across the board and your injectors cut out intermittently, that will break things by causing a temporarily lean condition that might not even show up in AFR readings, especially at the log rate of the MS. Check that voltage through several logs. Maybe you'll catch a big dip in one of them. Then check your main wiring: alternator +, battery + and -, power connections on your MS board, injector harness to main harness plug, ECU plug, etc.
#18
Boost Czar
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your accel enrichments are going crazy. Where is your MAP line spliced into?
you're running dangerously lean in boost...you're hitting 22psi.
what coils are you running, that's a lot of boost for stock coils/plugs.
your CAS is on the way out, you're getting crazy RPM spikes.
you're running dangerously lean in boost...you're hitting 22psi.
what coils are you running, that's a lot of boost for stock coils/plugs.
your CAS is on the way out, you're getting crazy RPM spikes.
#19
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your accel enrichments are going crazy. Where is your MAP line spliced into?
you're running dangerously lean in boost...you're hitting 22psi.
what coils are you running, that's a lot of boost for stock coils/plugs.
your CAS is on the way out, you're getting crazy RPM spikes.
you're running dangerously lean in boost...you're hitting 22psi.
what coils are you running, that's a lot of boost for stock coils/plugs.
your CAS is on the way out, you're getting crazy RPM spikes.
Running toyota cops
I'm going to re-run the vac lines to the ecu, I never thought my boost was that high my gauge never went past 14.... fml