popping and breaking up under WOT
popping and breaking up under WOT I'm posting this question for a friend of mine seeing as how his computer is down right now. We were doing a little tuning to his car last night, Forged 370 Iron block H/C PT88 turbo, and while I was monitoring the A/R and Knock sensors he was driving and trying to watch his IAT and injector DC %.
When he would go WOT there would be a signifigant amount of popping while the car was still pulling like a freight train, with slight hesitations. I have seen some turbo civics make this same noise at the drag strip which kinda lead me to believe that it was partly normal, but I don't know my way around turbo cars that much. Is the spark getting blown out? He is only running TR-6 plugs now but is about to step down to a much colder in the .025 range.
Any help that could point us in the right direction would be greatly appriciated.
When he would go WOT there would be a signifigant amount of popping while the car was still pulling like a freight train, with slight hesitations. I have seen some turbo civics make this same noise at the drag strip which kinda lead me to believe that it was partly normal, but I don't know my way around turbo cars that much. Is the spark getting blown out? He is only running TR-6 plugs now but is about to step down to a much colder in the .025 range.
Any help that could point us in the right direction would be greatly appriciated.
I was watching it on the computer the whole time and it was never constant. To begin with it was a little lean under WOT (in the upper 13's). We added fuel from 3200rpm's to redline and then when he would hit the throttle the A/R would climb quickly to high 12's, then drop to 9's and start climbing quickly again but never get out of the 12's.
Ah, I have heard about those 2 steps on imports. He is going to change the plugs and step down two heat ranges, change to some new 8.5 MSD wires, but keep the stock coil packs. That should at least eliminate all problems but a screwed up coil.
Joined: Jun 2004
Posts: 1,501
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From: Ft. Irwin, California (But Virginia is home)
I'm posting this question for a friend of mine seeing as how his computer is down right now. We were doing a little tuning to his car last night, Forged 370 Iron block H/C PT88 turbo, and while I was monitoring the A/R and Knock sensors he was driving and trying to watch his IAT and injector DC %.
When he would go WOT there would be a signifigant amount of popping while the car was still pulling like a freight train, with slight hesitations. I have seen some turbo civics make this same noise at the drag strip which kinda lead me to believe that it was partly normal, but I don't know my way around turbo cars that much. Is the spark getting blown out? He is only running TR-6 plugs now but is about to step down to a much colder in the .025 range.
Any help that could point us in the right direction would be greatly appriciated.
When he would go WOT there would be a signifigant amount of popping while the car was still pulling like a freight train, with slight hesitations. I have seen some turbo civics make this same noise at the drag strip which kinda lead me to believe that it was partly normal, but I don't know my way around turbo cars that much. Is the spark getting blown out? He is only running TR-6 plugs now but is about to step down to a much colder in the .025 range.
Any help that could point us in the right direction would be greatly appriciated.
1. If you are seeing 12's and 13's in the AFR at WOT your friend is begging to roast his engine. The fact it's forged is probably the only reason it's still in one piece (for now). You want to see an AFR of 11.1 to 11.6 WOT.
2. AFR's dropping to the 9 to 1 range will cause a nasty hesitation from overfueling. The fuel is literally trying to put the spark out. Fuel ratios that actually burn are 8 to 1 to 24 to 1. At 9 to 1 it's near the point of being incombustible, thus the hesitation there.
So, to fix, here's the Q's.
1. What are you using to tune/scan with? HP Tuners, a Diablo Predator, etc. If the latter, you need to upgrade to HP Tuners, EFI Live, or similiar.
2. What is the PE table set to at WOT? Should be between the values I mentioned above.
3. Is the ar MAF tuned? If yes, how much boost are you running? If it's over 8PSI, darn good chance the MAF is maxing out and causing the lean-out condition (assuming the Ve Table was set correctly in the 1st place). With boost, a 2 or 3 bar SD tune (depending on the boost level) is the way to go.
4. What size injectors and what is the injector duty cycle? I'd expect your friend is running no less than 60lb/hr injectors. Less is begging to run out of fuel, especiallyover 7PSI.
5. What's the WOT timing set at? A factor of the Ve table + fuel delivery. 16-20degrees is the norm. Higher will knock/detonate.
6. Are you getting knock and what g/cyl value is it occuring?
More info is needed overall......but these are some of the major Q's to be answered. All will affect/cause your problems.
My $0.02....tell your friend to stay out of boost until you have some answers to the above....
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#1 is the plugs. 6's are not going to work -- try 7's or 8's. Sounds like you are blowing out the spark. What type of fuel system - fuel pump, injectors? Gas being used? You're trying to tune a good size turbo.
Tuning an LS1 is the same, but also different than imports. Our cars do not like anti-lag - at least going at WOT
Anti-lag is what you hear when the "big boys" or imports are doing on the line to build boost on the line.
Agree watch your A/F - mine is tuned to 11.5 across the board. Any Leaner is not good, but running super rich 9.0 is also not good.
David
Tuning an LS1 is the same, but also different than imports. Our cars do not like anti-lag - at least going at WOT
Anti-lag is what you hear when the "big boys" or imports are doing on the line to build boost on the line.Agree watch your A/F - mine is tuned to 11.5 across the board. Any Leaner is not good, but running super rich 9.0 is also not good.
David
Thanks for all the suggestions guys.
To answer some of the questions:
Fuel system = (for now) 255lph Walbro, 60lb high impedence injectors, 93 octane.
Our first incling was that the spark was being blown out also. He did say that the car seems to run better down low with a little more timing. We all agree that it is too lean up top and he will not go WOT again until all cells are adjusted. Right now the turbo only has an 8lb spring. He isn't new to tuning, just new to tuning a large turbo LSX engine.
Fuel system = (for now) 255lph Walbro, 60lb high impedence injectors, 93 octane.
Our first incling was that the spark was being blown out also. He did say that the car seems to run better down low with a little more timing. We all agree that it is too lean up top and he will not go WOT again until all cells are adjusted. Right now the turbo only has an 8lb spring. He isn't new to tuning, just new to tuning a large turbo LSX engine.
Not enough pump, not enough injectors. You need (and I believe you know you need) to upgrade. That is possibly why you are so lean on top end. Your duty-cycle must be about max'd - even before you go close to WOT.
You need to upgrade or there is a real possibility than you'll
And none of us would enjoy that.
David
You need to upgrade or there is a real possibility than you'll
And none of us would enjoy that.David
Thanks for all the suggestions guys.
To answer some of the questions:
Fuel system = (for now) 255lph Walbro, 60lb high impedence injectors, 93 octane.
Our first incling was that the spark was being blown out also. He did say that the car seems to run better down low with a little more timing. We all agree that it is too lean up top and he will not go WOT again until all cells are adjusted. Right now the turbo only has an 8lb spring. He isn't new to tuning, just new to tuning a large turbo LSX engine.
To answer some of the questions:
Fuel system = (for now) 255lph Walbro, 60lb high impedence injectors, 93 octane.
Our first incling was that the spark was being blown out also. He did say that the car seems to run better down low with a little more timing. We all agree that it is too lean up top and he will not go WOT again until all cells are adjusted. Right now the turbo only has an 8lb spring. He isn't new to tuning, just new to tuning a large turbo LSX engine.
Actually, the DC was not even at 90%. He is only running 8lbs right now.
