09-03-2018, 09:58 AM | #1 |
700RWHP-650TQ
Drives: 2011 Forged LS3 Supercharged/Cammed Join Date: Aug 2010
Location: Shrewsbury Massachusetts
Posts: 5,269
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Bucking/Skip High RPM....?
Hello guys...Ive been chasing this issue all summer long. Here the mods.
Fully forged LS3 with SLP TVS2300 supercharger 2.8 Pulley (13psi). Comp Cam 216/246/ Id 850 injectors Txplugs Alky meth injection and more. Back to when the issue started was this past may. Went to exhaust shop and had resonators cut out on my current setup. Temps were cold, maybe 60 degrees. Wound up first about half way home and car bucked 2-3 times at high RPM under full boost. Quickly got out of it. Over the course of the following month it was very sporadic. Brought it to my tuner. Temps were now in the 80s and it never occurred for him. Changed out plugs and ran the months of june,july and august with zero problems. Tuesday I went back to the muffler shop and had them weld the muffler back on cause drone was killing me. Then just yesterday fired the car up. Temps outside were 86. checked my meth tank and noticed it was about 1/3 full. So i filled the tank with fresh meth. Took it out and bucking all over top end of first again. Happened 3 times on way back home. I quickly get out of it every time. It feels like the car just shuts off then on again and i cannot figure it out at all. I initial thought is some meth is pooling somewhere and then dumping in under boost causing the issue. I do drive aggressively every summer, however last summer i only went through 5 gallons of meth driving 1,700 miles. This summer I'm at 1,500 miles so far and have used 11 gallons and still going.. Do i have a leak somewhere or is this possible not related and could be various things. Car runs perfect otherwise and issue is sporadic. No lights or codes
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09-04-2018, 06:24 AM | #2 |
Interested in your issue as I have the same thing on my Whipple Blown ride. It bucks and cuts off at high RPMs, or when the wheels spin so fast that I can't pull a gear soon enough.
A fellow member suggested a re-tune, looking at these parameters listed here. I'm gonna get a re-tune prob late this fall or next spring, and ask my tuner if there is a way to soften up a full cutoff, as it is frustrating. But - don't want to blow up parts either. Cutoff Items: RPM Extreme Cutoff (choose a RPM) EOT Temp Wheel Speed Limit Spark - Enabled Fuel Cut - Disabled ETC - Enabled |
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09-04-2018, 09:21 AM | #3 |
700RWHP-650TQ
Drives: 2011 Forged LS3 Supercharged/Cammed Join Date: Aug 2010
Location: Shrewsbury Massachusetts
Posts: 5,269
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I hope i can somehow figure this out...its making me want to sell it
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09-04-2018, 09:29 AM | #4 |
Drives: 2015 SW 2SS 1LE Join Date: Jan 2018
Location: 78155
Posts: 308
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I think you guys are hitting the rev limiter, in 1st gear the tach can't keep up. You might think about installing a shift light. A friend of mine was going the same thing.
G/L
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Maggie 2650 @ 18psi/ 75mm 10 rib/ Dual alky nozzles/ Roto-fab/ ARH 2" Lt's/ GT-12 cam/ ZL1 3.23 Conv./MGW/RPS triple carbon clutch/RSG tranny upgrage/Pedders Ex. XA w/ remote cans and a lot of other crap 897/8??@tires
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09-04-2018, 10:02 AM | #5 |
700RWHP-650TQ
Drives: 2011 Forged LS3 Supercharged/Cammed Join Date: Aug 2010
Location: Shrewsbury Massachusetts
Posts: 5,269
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No way its the rev limiter.....Im breaking apart high 4k to mid 5,000rpm long before i normally shift
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09-04-2018, 10:40 AM | #6 |
I gotta shift light and it is set below 6000 RPM, but trust me the wheel speed under 3/4 up to full throttle on a 600+ HP car making boost will ramp up so fast that when the shift light go's off it is too late. Esp when doing "Burn Outs" for fun. My guess is a Dyno Pull tuning is not like real world street thrashing, and one or more parameters like RPM and Wheel Speed limits may be key factors. Issue has nothing to do with Traction Control On or Off, but find the car does not like the Traction Control On, and that is no fun anyway.
Wonder if anyone with tuning experience knows and can explain what these parameters are, and suggestions for settings to feed to my Tuner? "Cutoff Items: RPM Extreme Cutoff (choose a RPM) EOT Temp Wheel Speed Limit Spark - Enabled Fuel Cut - Disabled ETC - Enabled" But - I found this in a post, gonna try it: Bottom line is, there is a sensor on the clutch pedal that is setup to be extremely sensitive. If you even rest your foot on the clutch to get ready for the next shift (from 1-2nd, or 2nd-3rd)... it cuts off the spark to the engine so as to prevent over-revving it... and man, do you feel it. I've seen a few threads on this without any solution and I'm betting most of us will put a bit of pressure on the clutch right around that 5k mark, roughly... just unconsciously. It's not traction control or anything like that; it's a deliberate safety mechanism (as I suspected but, never realized I was "priming" the clutch getting ready for the next shift just a touch). I went out after reading it, and tried again - this time with my foot about 1" away from the clutch and stomped the pedal in track mode (no PTM or anything else set, all nannies were ON). Sure enough, it went smooth as butter (and violently awesome, I might add) to 6.5k redline like it should... and depressing the clutch throws it into 2nd very quickly. 2nd goes all the way to redline, and into 3rd now with ZERO problem. |
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09-05-2018, 02:58 PM | #7 |
Drives: 2013 Camaro 2SS Inferno Orange Join Date: Apr 2015
Location: Utah
Posts: 174
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im having the same issue and trust me its not fun its gotten worse for me to where the car will just die if you dont get out of it quick enough. Ive worked on it this whole week using various tools. i think i got is narrowed down.
When the car cuts out im loosing signal to the crank position sensor ive done a crank relearn and still the same. I pulled some diagrams this morning and im going to look at some data logs and freeze frames to start chasing some wires |
09-06-2018, 07:33 AM | #8 |
GPI Sales Consultant
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Sounds like a tuning issue - I would get a scanner on the car and find out what's actually going on, rather than continuing to guess.
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09-06-2018, 07:43 AM | #9 |
700RWHP-650TQ
Drives: 2011 Forged LS3 Supercharged/Cammed Join Date: Aug 2010
Location: Shrewsbury Massachusetts
Posts: 5,269
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Ive never data logged before so its a whole new learning curve. But thats my plan to get some data
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09-06-2018, 07:46 AM | #10 |
GPI Sales Consultant
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It's really a must-do in a situation like this. The car will pretty much tell you what the problem is, if you can collect and analyze the data correctly.
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GPI Max Package 2.0: Brodix BR7 heads/GPI porting, MAX3 cam, ST2116LSR, BSR Max Lift rockers, LS7 LSXR with 103mm TB, Vararam OTR, Mcleod RXT, G-Force/Strange 9" IRS setup with 4.63 gear. 551whp, 11.1@124mph.
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09-06-2018, 02:12 PM | #11 |
700RWHP-650TQ
Drives: 2011 Forged LS3 Supercharged/Cammed Join Date: Aug 2010
Location: Shrewsbury Massachusetts
Posts: 5,269
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Weird thing i noticed is the stability Trak light flashes when ever it happens. But it still happens when i turn everything off. so weird.
I tried data logging today but having issues downloading the software. Did about 25 pulls and only happened 1 time. and the 1 time it happened was when i was riding 1st gear at about 4,000 for a bit in traffic and then punched it. Never happened from a low rpm to high. According to my SCT tuner the highest RPM that i hit was 6550.5 so not hitting the rev limiter.
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