Thoughts on what could cause a dyno graph like this?
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Teching In
Joined: Sep 2008
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Thoughts on what could cause a dyno graph like this? 
Car is going back to the shop that put the new engine in (about 10k miles ago) for logging and I'm confident he will take care of it, just curious of what you guys opinions would be. Car runs pretty well unless I really get into it and it's not throwing any codes.
It's a driver, not a racecar. ls6 intake and cam, full exhaust...that's about it so the numbers aren't terribly far off from where they should be I think.
No smoothing set? Bad pickup on the dyno for the RPMs? Most tunes with 0 smoothing look pretty jagged. If your fueling transitions or timing are all over the place, you can get stuff like that too.
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Teching In
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Even though it's not listed on there, I don't think it's a smoothing issue. Basically all this place does is dyno runs and also the car sounded pretty bad the more they got into it. The guy running the dyno didn't even want to push it to 6000+ after the first run.
It's losing power at/after 4500 rpm.
Maybe there's a tuning issue, and the fuel delivery isn't set right in the upper RPM range? (I'm not a tuner, just guessing)
Who did the tuning, and do they tune LS engine a lot?
Maybe there's a tuning issue, and the fuel delivery isn't set right in the upper RPM range? (I'm not a tuner, just guessing)
Who did the tuning, and do they tune LS engine a lot?
Thread Starter
Teching In
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I think he's a sponsor here, so I'm not going to name names and I really do have faith that if it is a tuning issue of some sort, he will make it right. Definitely has the experience. You could absolutely be correct...he'll be getting the car soon, just thought maybe someone else had seen something similar and had some ideas.
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Teching In
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Plugs only have about 10k miles on them so they should be good. Probably wouldn't hurt to change the wires so I'm planning on doing that this weekend. They have at least ~25k miles on them, maybe more. I was going to go ahead and pick some up, but all the local chain places only had the poorest of the poor choices available in store so I'm going to have to order some decent ones online.
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On The Tree
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Check the ground wires. A loose ground can do really weird stuff like that. I had a 91 caprice with perfectly good looking negative wires. Battery to engine, battery to frame. Added an additional cable from engine to frame and all my troubles went away. 91-96 caprices and road masters were notorious for poor grounding and issues with wires to the fuel pumps.
Other thoughts...
It's not always the computer. Remember the basics: air, fuel, spark.
Other thoughts...
- How old is the fuel pump? put a gauge on it and see if pressures are normal and stable. Your's could be on it's way out.
- Check/replace the fuel filter too
- Fuel pump solenoid
It's not always the computer. Remember the basics: air, fuel, spark.
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Teching In
Joined: Sep 2008
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Check the ground wires. A loose ground can do really weird stuff like that. I had a 91 caprice with perfectly good looking negative wires. Battery to engine, battery to frame. Added an additional cable from engine to frame and all my troubles went away. 91-96 caprices and road masters were notorious for poor grounding and issues with wires to the fuel pumps.
Other thoughts...
It's not always the computer. Remember the basics: air, fuel, spark.
Other thoughts...
- How old is the fuel pump? put a gauge on it and see if pressures are normal and stable. Your's could be on it's way out.
- Check/replace the fuel filter too
- Fuel pump solenoid
It's not always the computer. Remember the basics: air, fuel, spark.
I have no idea how old the fuel pump is, could very well be original for all I know. Maybe the fuel pressure will help narrow it down in that regard.
Thanks man.