help! down 100hp on chassis dyno
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help! down 100hp on chassis dyno I've got a 2002 ls1 with a 4l60e and i put 215cc afr heads with 59cc chambers on with a g5x4 cam and am only making 360hp at the rear wheels after a tune. Any thoughts on what could be wrong would be appreciated.
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We did a leak down and all 8 were under 5%. It has the LS6 intake and TB. All 8 header tubes were hot. I was using 4.7" chromemoly push rods. I have a trick flow fuel regulator, and it's set at 60PSI. One of my friends watched the gauge during a pull on the dyno and said I didn't loose any pressure. We did most of the pulls in drive with the torque converter locked up, but for testing we did 1 pull in 2nd gear and the #'s were the same. Then we changed to a smaller tire and higher gear in the rearend and the #'s were the same. The only thing on my engine that isn't a proven part that I know of it the headers. They are 1-3/4" mandrel bent, It's a set you have to weld up that I bought from speedway then had them ceramic coated. We did try a pull with a set of stock manifolds to see if my headers were total junk and of course we lost about 15 hp on that pull. I have an underdrive pulley on the crank and don't run AC so there is minimal loss in the accessories on the front of the motor. Thanks for the help, any other ideas like how to know for sure I have enough fuel? I can see in the fuel cell that at an idle there is a full stream coming out the -6 fittings on the return line back to the tank.
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Do the lifters go bad? That's one thing I was thinking about last night. Other thing could there be an electrical problem? I doubt the electrical problem because we'd see that on the tuner when it's hooked up at the dyno shop I assume???
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Injector size? Assuming you put in bigger injectors and changed the tune to correspond with them... I'm going to guess you have a valve train or air to fuel ratio problems. There are so many variables here. A dyno graph might help, but threads like this are always very difficult to diagnose because we need a lot more information than what was given in the first post.
QUICK EDIT: I assume you made a typo on the 4.7" pushrod length. No way could you possibly be using a pushrod that short. Plus I'd also be worried if you actually meant 7.4" pushrod because that seems like an awfully long pushrod to be using with a 59CC head.
QUICK EDIT: I assume you made a typo on the 4.7" pushrod length. No way could you possibly be using a pushrod that short. Plus I'd also be worried if you actually meant 7.4" pushrod because that seems like an awfully long pushrod to be using with a 59CC head.
Last edited by edwardzracing; Jun 17, 2011 at 07:41 PM.
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Verdad Gallardo We did a leak down and all 8 were under 5%. It has the LS6 intake and TB. All 8 header tubes were hot. I was using 4.7" chromemoly push rods. I have a trick flow fuel regulator, and it's set at 60PSI. One of my friends watched the gauge during a pull on the dyno and said I didn't loose any pressure. We did most of the pulls in drive with the torque converter locked up, but for testing we did 1 pull in 2nd gear and the #'s were the same. Then we changed to a smaller tire and higher gear in the rearend and the #'s were the same. The only thing on my engine that isn't a proven part that I know of it the headers. They are 1-3/4" mandrel bent, It's a set you have to weld up that I bought from speedway then had them ceramic coated. We did try a pull with a set of stock manifolds to see if my headers were total junk and of course we lost about 15 hp on that pull. I have an underdrive pulley on the crank and don't run AC so there is minimal loss in the accessories on the front of the motor. Thanks for the help, any other ideas like how to know for sure I have enough fuel? I can see in the fuel cell that at an idle there is a full stream coming out the -6 fittings on the return line back to the tank.
swap injectors bro just to be safe my afr was great but i was down 70 RWHP because of the spray pattern just put in a other set
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yep the pushrods are 7.4" not 4.7" I'll for sure try the bigger injectors when I get to the dyno again. My headers have short mufflers that don't to much on them so I can't hear if there is any noise from the motor. I do know that the knock sensors were only retarding the timing a degree or so during the pulls. With the possibility of fuel, has anyone had a set of lifters that aren't working right? It sounds like I should buy a new set of lifters when I put it back together.
Thanks for the help, and any other ideas are welcome.
The guys at LG said that stock length pushrods are what I need to be using for these heads. When we did a leakdown on the cylinders if I had the wrong length of pushrods I wouldn't have been able to maintain any pressure in the cylinder????
Thanks for the help, and any other ideas are welcome.
The guys at LG said that stock length pushrods are what I need to be using for these heads. When we did a leakdown on the cylinders if I had the wrong length of pushrods I wouldn't have been able to maintain any pressure in the cylinder????
I still don't see the injector size listed anywhere. If you're using stock size injectors, I can see this causing a huge problem with those heads and a good sized camshaft. Did they happen to mention what the duty cycle % was on the injectors? Or was any data logged during the pulls? I would assume so.
What type of lifter are you using? Did you replace them when you did the camshaft? What about valve spring? Are you using a valve spring capable of the amount of lift that your camshaft has? Fill us in.
What type of lifter are you using? Did you replace them when you did the camshaft? What about valve spring? Are you using a valve spring capable of the amount of lift that your camshaft has? Fill us in.
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From: Turnin' Wrenches Infractions: 005
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I bought a 5.3l out of a truck to put in the car and see what drive train loss is and it made 240hp at the rear wheels with my ls6 intake and headers on. So I've eliminated drive train loss. Now I'm down to replacing the lifters and getting the cam degree'd in properly. It's in the shortblock assy. so to speak. The motor is completely torn down now and there were no bad bearings and the pistons look fine. We have a tool coming to check the position of the reluctor wheel and will replace the lifters and degree in the cam and see what differences that has made.
Do you have a dyno graph? Why kind of dyno? Where was the power peak at?
Do you know what your AFR and injector D/C was?
Do you have a stall? If so how big? I know you said you locked it and didn't make the much difference. It's a super effecient converter or something else is amiss.
Was the dyno loaded/calibrated correctly? Can you take it to another dyno to compare numbers/graphs?
Do you know what your AFR and injector D/C was?
Do you have a stall? If so how big? I know you said you locked it and didn't make the much difference. It's a super effecient converter or something else is amiss.
Was the dyno loaded/calibrated correctly? Can you take it to another dyno to compare numbers/graphs?