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boosting_laser
Senior Member
Joined: Tue May 22, 2007 10:48 pm Posts: 781 Location: Whittier
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Re: Fuel cut
Yup! My first & only experience, I almost went through the windshield during the launch at the old dragway.
_________________Hugo Best 1/4 mile: 10.78 @ 131, 27psi, E85 Best 1/8 mile: 6.97 @ 101, 29 psi, E85531.5whp 414.8tq @ 29psi, FP3575 on Q16
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Wed Dec 01, 2010 2:50 pm |
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ninnyVR4
DSM Regular
Joined: Fri Nov 19, 2010 4:51 pm Posts: 115
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Re: Fuel cut
What happens is it does one big jolt. Could be blowing out spark, but not sure. The strange thing is it's intermittent. Last night it pulled through 3rd just fine. Let off at 90. I'll check the plugs. What should they be gapped at and also what plugs do most of you run? Colder spark or do you just run stock replacements
_________________98 Grand Prix GTP (L32 swapped, 286whp/368wtq) 13.8 @ 102mph - SOLD91 Galant VR4 #852/2000. SOLD97 Outback Legacy 5-speed... SOLD99 Mustang GT So sue me haha
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Wed Dec 01, 2010 4:21 pm |
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Black_gst
Death to Head Gaskets!
Joined: Tue Jan 27, 2009 10:38 am Posts: 1979
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Re: Fuel cut
If it feels like you hit a small wall or large dog its fuel cut. if it shakes like your running over small bumps on the fwy or hesitation it just missing
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Wed Dec 01, 2010 4:24 pm |
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CaptainTonus
Post Master
Joined: Mon Sep 20, 2010 12:25 pm Posts: 529 Location: San Diego, CA.
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Re: Fuel cut
_________________'91 GSX - 511fwhp & 352 lb/ft @ 25psi 110 octane, 7.68 @ 95.9mph 1/8th 91 octane @ 21psi '98 Volvo S70 T5 - DD http://www.facebook.com/captaintonus
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Wed Dec 01, 2010 4:26 pm |
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Illeagle
Talon of Doom
Joined: Wed May 23, 2007 10:07 am Posts: 3615 Location: Long Beach
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Re: Fuel cut
NGK coppers. BPR7ES or 8ES. the 7's should be good for a while, I've ran up to 30+ psi of boost on the 7's, just gotta gap them lower the higher boost you go. Stock ish boost = .030", 20psi = .020"~.024", 30psi = .016"~.020" or lower. Depending on your ignition system.
_________________1/4 ET-11.657@121.18mph w/ 1.682 60' 445whp/427tq on RRE Dyno All on 91 pump. Do you need your car tooned? Got some extra cash? PM me for details. I offer street and dyno tunes
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Wed Dec 01, 2010 7:28 pm |
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ninnyVR4
DSM Regular
Joined: Fri Nov 19, 2010 4:51 pm Posts: 115
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Re: Fuel cut
_________________98 Grand Prix GTP (L32 swapped, 286whp/368wtq) 13.8 @ 102mph - SOLD91 Galant VR4 #852/2000. SOLD97 Outback Legacy 5-speed... SOLD99 Mustang GT So sue me haha
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Wed Dec 01, 2010 7:47 pm |
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Illeagle
Talon of Doom
Joined: Wed May 23, 2007 10:07 am Posts: 3615 Location: Long Beach
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Re: Fuel cut
Ok, if you hit fuel cut, it means you over ran stock MAF Common on 1G. Could be too much airflow (big turbo, or high boost). Or you have a boost leak, and the turbo is pulling extra air through to sensor to compensate for the pressure drop due to the leak. I would still do a leak test anyways, and it should become a normal standard service like an oil change. At least twice a year. You'll be amazed how much faster the car is with all the leaks fixed.
_________________1/4 ET-11.657@121.18mph w/ 1.682 60' 445whp/427tq on RRE Dyno All on 91 pump. Do you need your car tooned? Got some extra cash? PM me for details. I offer street and dyno tunes
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Wed Dec 01, 2010 7:57 pm |
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ninnyVR4
DSM Regular
Joined: Fri Nov 19, 2010 4:51 pm Posts: 115
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Re: Fuel cut
Maybe one of you guys more knowledgable with this engine might be interested in helping me out. I'm used to a car with 2 vacuum lines so I wouldn't know where to start
_________________98 Grand Prix GTP (L32 swapped, 286whp/368wtq) 13.8 @ 102mph - SOLD91 Galant VR4 #852/2000. SOLD97 Outback Legacy 5-speed... SOLD99 Mustang GT So sue me haha
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Wed Dec 01, 2010 9:22 pm |
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CaptainTonus
Post Master
Joined: Mon Sep 20, 2010 12:25 pm Posts: 529 Location: San Diego, CA.
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Re: Fuel cut
_________________'91 GSX - 511fwhp & 352 lb/ft @ 25psi 110 octane, 7.68 @ 95.9mph 1/8th 91 octane @ 21psi '98 Volvo S70 T5 - DD http://www.facebook.com/captaintonus
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Wed Dec 01, 2010 11:24 pm |
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ninnyVR4
DSM Regular
Joined: Fri Nov 19, 2010 4:51 pm Posts: 115
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Re: Fuel cut
Well just checking, I had one lose vacuum line leading to the second stage of the boost controller and one torn line leading to the BOV. Other than that, can't see any other issues with the vacuum
_________________98 Grand Prix GTP (L32 swapped, 286whp/368wtq) 13.8 @ 102mph - SOLD91 Galant VR4 #852/2000. SOLD97 Outback Legacy 5-speed... SOLD99 Mustang GT So sue me haha
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Thu Dec 02, 2010 12:25 am |
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Illeagle
Talon of Doom
Joined: Wed May 23, 2007 10:07 am Posts: 3615 Location: Long Beach
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Re: Fuel cut
its not so much vacuum, its that EVERYTHING between the turbo and cylinders gets pressurized under boost. ANYTHING that leaks between point A and B is a leak. It is airflow that the ECu has already accounted for, and if it goes missing it has no idea and supplies fuel for it even though it has leaked out. The turbine itself will spin at a higher speed and draw more airflow through the sensor and turbo to compensate. Imaging you are a usher of a concert hall, and its free drink night 1 per customer. You count 2000 people entering, and make 2000 drinks. 300 people sneak out the back door. A lot of extra drinks. The car runs rich with leaks. As far as your fuel cut issue, there is a safety limitation built into the stock MAF for overboost protection. As more airflow moves into the engine, more fuel has to go with it. When an injector hits 100% duty cycle, it cant supply anymore fuel. In this scenario, the car leans out, and things start to melt. The ECU does a sort of protection not on duty cycle but MAF hz count because Hz count is THE MAIN thing that goes into fueling calculation. Higher Hz = higher IDC (injector duty cycle). How this plays into your fuel cut and boost leaks? Imagine a balloon it takes 4 lung fulls of air to fill it. I put a small pin hole in it, you can still inflate it, but you are huffing and puffing to keep it up. The turbo does the same and that extra huffing and puffing pulls more air through the MAF, thus a higher HZ count till it hits the limit and hence fuel cut. Why I say boost leak? I've rarely hit fuel cut on a stock turbo setup, even on a turbo setup mildly larger than stock. only times I have was when I had boost leaks. Speaking of misfires...I gotta clean and re-gap my plugs, they aren't liking the ignition-cut and 32psi of boost.
_________________1/4 ET-11.657@121.18mph w/ 1.682 60' 445whp/427tq on RRE Dyno All on 91 pump. Do you need your car tooned? Got some extra cash? PM me for details. I offer street and dyno tunes
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Thu Dec 02, 2010 2:32 am |
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ninnyVR4
DSM Regular
Joined: Fri Nov 19, 2010 4:51 pm Posts: 115
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Re: Fuel cut
A lot to take in haha. Makes sense. Heading over to my buddies today who has a better grasp of the 4g63 than I do (owns a highly modded 91 vr4, and 90 tsi). So Should get most of the issues worked out. I'll post otherwise though. Updates as well, and all that jazz
_________________98 Grand Prix GTP (L32 swapped, 286whp/368wtq) 13.8 @ 102mph - SOLD91 Galant VR4 #852/2000. SOLD97 Outback Legacy 5-speed... SOLD99 Mustang GT So sue me haha
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Thu Dec 02, 2010 12:49 pm |
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