Power falling hard after 5300RPMs
Power falling hard after 5300RPMs The power curve does not look right to me, and looks like the motor is choking.
The engine is a 03 5.3 stock long block with 56,000mi, a LPE GT2-3 cam and Patriot gold springs, and pushrods.
The turbo kit is a stock 02 Fbody manifold on the drivers side, 2.5" cross over feeding the back of a 3" log on the passenger side with 1 3/4" primaries going to a T4 flange and a TC78 with a .96 exhaust housing. 3.5" DP all the way out back to a Hooker Max Flow muffler. Wastegate is vented to atmosphere in the front/bottom of engine bay.
A/F is steady, first pull was ~10.2, leaned it out for the next pull to ~11.5 and picked up 10rwhp. When I went from 12* to 13* of timing it held peak power another 200 RPMs (peak was at 5300 with the timing), then fell off sharply again.
Made it to the dyno, still waiting to get the run files sent to me, but made a graph from memory. The car made 485hp/480tq on 10lbs pump gas and 13* of timing, then lost nearly 200hp from peak to 6300
Boost leak maybe?
The shop I was at at first thought the turbo was too small, so we verified that it was a 78mm.
I know I need to get a pressure reading in the exhaust to see if the restriction is possibly the turbo/turbo kit.
Any other ideas on where to look?
The engine is a 03 5.3 stock long block with 56,000mi, a LPE GT2-3 cam and Patriot gold springs, and pushrods.
The turbo kit is a stock 02 Fbody manifold on the drivers side, 2.5" cross over feeding the back of a 3" log on the passenger side with 1 3/4" primaries going to a T4 flange and a TC78 with a .96 exhaust housing. 3.5" DP all the way out back to a Hooker Max Flow muffler. Wastegate is vented to atmosphere in the front/bottom of engine bay.
A/F is steady, first pull was ~10.2, leaned it out for the next pull to ~11.5 and picked up 10rwhp. When I went from 12* to 13* of timing it held peak power another 200 RPMs (peak was at 5300 with the timing), then fell off sharply again.
Made it to the dyno, still waiting to get the run files sent to me, but made a graph from memory. The car made 485hp/480tq on 10lbs pump gas and 13* of timing, then lost nearly 200hp from peak to 6300
Boost leak maybe?
The shop I was at at first thought the turbo was too small, so we verified that it was a 78mm.
I know I need to get a pressure reading in the exhaust to see if the restriction is possibly the turbo/turbo kit.
Any other ideas on where to look?
i dont think the turbo is too small.im having the same issue.i changed out my valve springs last week.im hoping thats all it is but i have not had time to test.
i would look into springs and back pressure with a log/crossover style kit
i would look into springs and back pressure with a log/crossover style kit
Boost is holding pretty steady, I don't notice it on the gauge at all. It used to spike, might move 2-3KPA in the datalog. I have noticed a change by as much as .5psi depending on temp changes in the weather, 20-30degree changes. Im currently running a 3/16 line to a manual boost controller then to the wastegate, maybe 12" of rubber line in total going from the compressor housing, MBC, wastegate (JGS 50r).
The cold side is a 2.5-3" 90* coupler right off the turbo to 3" IC piping and a Ebay 31x12x4" core then 3" to the TB. When I get a chance I will check for a boost leak, I wonder if the BOV is leaking.
On the dyno we verified the 4" rubber coupler form the filter/turbo was not collapsing.
The valve springs have 2k miles on them now, and were heat cycled. Ill try and get a chance to pull the covers to make sure there are no broken inner springs.
The cold side is a 2.5-3" 90* coupler right off the turbo to 3" IC piping and a Ebay 31x12x4" core then 3" to the TB. When I get a chance I will check for a boost leak, I wonder if the BOV is leaking.
On the dyno we verified the 4" rubber coupler form the filter/turbo was not collapsing.
The valve springs have 2k miles on them now, and were heat cycled. Ill try and get a chance to pull the covers to make sure there are no broken inner springs.
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That is a much bigger drop than what I thought it was from what you posted on the local forum. I thought it just kinda tappered off, not fell like that. I still think the ls1 intake is hurting you, but I don't think it is your issue.
I think you are having a converter issue.
I think you are having a converter issue.
That is a much bigger drop than what I thought it was from what you posted on the local forum. I thought it just kinda tappered off, not fell like that. I still think the ls1 intake is hurting you, but I don't think it is your issue.
I think you are having a converter issue.
I think you are having a converter issue.
If I can find a LS6 intake to barrow, and do some back to back pulls with it I will.
Have you checked your fuel pressure? I had a similar issue and my fuse going to my fuel pump was acting up and the problem was completely discovered when the fuse eventually blew. We thought valvesprings, slipping clutch, etc. Turned out to be a stinking bad fuse.
When it was the fuse, was FP dropping as you made a pull? I got to watch mine on one of the pulls and it raised like it should and held until the end of the pull. I have had a fuel volume problem once before after driving the car for quite a bit, went to the track and the car kept leaning out at the top of every gear.
On the dyno fuel did not seem like a problem, A/F was pretty level/pressure was good. I did notice IDC is still climbing as the engine revs to 6400, yet power falls like a rock.
I currently have a single 255 intank, and 60lb injectors at 43.5psi and a 1:1 referenced regulator, stock 3/8th feed and 5/16 return.
On the dyno fuel did not seem like a problem, A/F was pretty level/pressure was good. I did notice IDC is still climbing as the engine revs to 6400, yet power falls like a rock.
I currently have a single 255 intank, and 60lb injectors at 43.5psi and a 1:1 referenced regulator, stock 3/8th feed and 5/16 return.
Measure the backpressure in the exhaust between the engine and turbo. It may be getting so high that it adds boost, taking away the effective boost in the cylinders. If it is too high, time to change to a larger AR housing.
Well my fuel pressure also jumped up like it was suppose too, but eyes went off the fp and on to the a/f on the dyno once it was holding steady b4 the rpm drop. Mine fell just like yours and my a/f started climbing once I hit that wall and we let off. My issue was a bad fuse.
When it was the fuse, was FP dropping as you made a pull? I got to watch mine on one of the pulls and it raised like it should and held until the end of the pull. I have had a fuel volume problem once before after driving the car for quite a bit, went to the track and the car kept leaning out at the top of every gear.
On the dyno fuel did not seem like a problem, A/F was pretty level/pressure was good. I did notice IDC is still climbing as the engine revs to 6400, yet power falls like a rock.
I currently have a single 255 intank, and 60lb injectors at 43.5psi and a 1:1 referenced regulator, stock 3/8th feed and 5/16 return.
On the dyno fuel did not seem like a problem, A/F was pretty level/pressure was good. I did notice IDC is still climbing as the engine revs to 6400, yet power falls like a rock.
I currently have a single 255 intank, and 60lb injectors at 43.5psi and a 1:1 referenced regulator, stock 3/8th feed and 5/16 return.
One idea is if HP would still fall if I ran the car on racegas, with more timing, or ramping in more timing as the RPMs increased to help pull the power band up.
[QUOTE=MaxxMitchell;11506780]
Made it to the dyno, still waiting to get the run files sent to me, but made a graph from memory. The car made 485hp/480tq on 10lbs pump gas and 13* of timing, then lost nearly 200hp from peak to 6300
13* of timing for 10lbs is a little on the low side but still it shouldnt drop off that drastically, graph looks smooth so it's not the valve springs, By the graph it looks like it is just loosing boost....Everything located in the proper location, ie wastegate, bov ....
Made it to the dyno, still waiting to get the run files sent to me, but made a graph from memory. The car made 485hp/480tq on 10lbs pump gas and 13* of timing, then lost nearly 200hp from peak to 6300
13* of timing for 10lbs is a little on the low side but still it shouldnt drop off that drastically, graph looks smooth so it's not the valve springs, By the graph it looks like it is just loosing boost....Everything located in the proper location, ie wastegate, bov ....
Hmm if the boost isn't dropping then its not backpressure. Something else is causing the problem. Especially at such low boost. I could see this being a problem at 17-20psi with a TC maybe, but not 10. Also log manifolds are always suspect for flow as well.
Also does the crossover pipe plumb back into the system and Y at the T4 flange or does it go also into the log?? If it goes into the log that is a big no-no. Same problem the old TTI kits had on the LT1's. Massive back pressure.