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Whats Up at 6200 ?

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Old Dec 1, 2007 | 08:29 AM
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Default Whats Up at 6200 ?

Got the tune in my LS1 GTO updated yesterday due to a FAST 90/90 (unported) and new catback install. Cam is TR224/224 with AFR 205s. Not unhappy with numbers....but tuner could not figure out whats happening at 6200 - and then we ran out of dyno time. He did 4 pulls on the Dynojet and they all looked about the same. He suspects maf issues - like not enough space / distance between filter and maf - or something. I did just change out to an delphi 85 mm truck maf (descreened) on my LS1 (casper harness) - and he did load new maf tables - but otherwise its an 05/06 oe gto maf / intake tube with a standard 05 lpe cai configuration - so why would insufficient space be an issue ?
Im not sure there is enough info here but anyway, anybody here have any suggestions on where to start looking ?
Attached Thumbnails Whats Up at 6200 ?-dyno120107crop.jpeg  

Last edited by gtodude; Dec 1, 2007 at 09:51 AM.
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Old Dec 1, 2007 | 07:22 PM
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The graph looked just like this one on each of the 4 pulls. Flakes-out at 6200 like clock-work. Thoughts ?
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Old Dec 1, 2007 | 08:08 PM
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fuel pump? injectors?
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Old Dec 1, 2007 | 08:42 PM
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Originally Posted by MattIROC
fuel pump? injectors?
was wondering bout that ..makes sense.
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Old Dec 1, 2007 | 09:36 PM
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what was the MAP reading?
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Old Dec 1, 2007 | 10:41 PM
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Originally Posted by MattIROC
fuel pump? injectors?
If that is caused by lack of fuel, it would be plainly evident in the A/F graph. It would have to be blow up lean to do that.
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Old Dec 1, 2007 | 10:42 PM
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Originally Posted by mrr23
what was the MAP reading?
I've seen cars gain 10 Kpa of vacuum, and not drop anything like that.
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Old Dec 2, 2007 | 07:17 AM
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ETC Fuel cutoff maybe?
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Old Dec 2, 2007 | 11:51 AM
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Originally Posted by Eurospec2
ETC Fuel cutoff maybe?
some sort of fuel or ignition cut-off was my first thought after the second and then the third pull showed power cutting off sharply and consistently pretty much at 6200 - 6250. I asked my tuner - and he said no - but worth following up on again.
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Old Dec 2, 2007 | 03:52 PM
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Originally Posted by edcmat-l1
I've seen cars gain 10 Kpa of vacuum, and not drop anything like that.
well, if it was bouncing around, it would indicate valve float.
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Old Dec 2, 2007 | 04:44 PM
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Originally Posted by mrr23
well, if it was bouncing around, it would indicate valve float.
Thats true. But again, it would have to be some wicked valve float to do that.
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Old Dec 3, 2007 | 04:03 AM
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6200-6250 is right about where the car gets shut off stock by the ecu correct? might wanna check into that
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Old Dec 9, 2007 | 02:12 PM
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i finally got my hands on an inch-pound torque wrench and found my best guess torque on the new fast 90 manifold was way short. I had maybe 50 inch pounds on the manifold bolts - was suppossed to be 89 inch-pounds. what kind of problems could that cause - could that be the source of my problem ?
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Old Dec 9, 2007 | 08:57 PM
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Originally Posted by DarkJuggalo
6200-6250 is right about where the car gets shut off stock by the ecu correct? might wanna check into that

Seems right to me. Tell your tuner to up your rev limit to 6500.
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Old Dec 9, 2007 | 09:16 PM
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I would think too much timing and a partial bad spark plug, or really lean or really rich and blowing out the spark.. Or some kind of restriction sucking up and plugging the air filter or VERY poor airflow going to the intake. Does it have a really harsh step going from the neck of the airfilter setup to the throttleblade?.
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Old Dec 9, 2007 | 10:01 PM
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Looks like a rev limiter or speed limiter.Valve float wouldn't do that or a loose intake..
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Old Dec 10, 2007 | 07:33 AM
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Originally Posted by Slowhawk
Looks like a rev limiter or speed limiter.Valve float wouldn't do that or a loose intake..
I agree. Looks to harsh of a drop off to be anything but a speed or rpm cut. Can you post up a tune and run log?
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