FI help needed- Dyno Tuning problems
11-09-2006, 10:00 AM
#1
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FI help needed- Dyno Tuning problems My friend purchased a C5 that has a intercooled vortex system, TSP LT headers, 42lb inj, and everything else is stock LS1. The car has run like absolute crap since he received it. The seller stated that the tune was a mail order tune and it hadn't been adjusted to run with the 9lb pulley that was on the supercharger.
We take the car in to get dyno tuned and after the base line dyno run the tuner says that he saw the boost gauge get near 12 lbs. He checks his data log and it actually hit 14lbs. The car made 458 and 440!!!?? The tuner tells me that he can get it to run better but highly recommends that we change the pulley because he is affraid we are going to blow the stock bottom end. He makes a few more adjustment and he makes another pull and we put down 459 and 442 at over 15lbs this time. He told us to change the pulley and bring it back for a retune. Sounds good to us because we don't want to blow her up.
The car runs and drives better but it is obviously not making the power it should. I am new to FI motors, if someone could point me in the right directions here. Will changing the pulley solve my problems??? Is there anything I should check that could be causing such high boost and low power??
FYI- Before the tune we did a full tune up on it. Everything seems to be look good as far as the motor. Where do I start??
Thanks in advance,
J.R.
We take the car in to get dyno tuned and after the base line dyno run the tuner says that he saw the boost gauge get near 12 lbs. He checks his data log and it actually hit 14lbs. The car made 458 and 440!!!?? The tuner tells me that he can get it to run better but highly recommends that we change the pulley because he is affraid we are going to blow the stock bottom end. He makes a few more adjustment and he makes another pull and we put down 459 and 442 at over 15lbs this time. He told us to change the pulley and bring it back for a retune. Sounds good to us because we don't want to blow her up.
The car runs and drives better but it is obviously not making the power it should. I am new to FI motors, if someone could point me in the right directions here. Will changing the pulley solve my problems??? Is there anything I should check that could be causing such high boost and low power??
FYI- Before the tune we did a full tune up on it. Everything seems to be look good as far as the motor. Where do I start??
Thanks in advance,
J.R.
11-10-2006, 03:49 AM
#2
Was the tuner seeing spark knock? If he was, spark knock would pull timing out of the engine, resulting in the lower power output.
Was the fuel pressure being monitored? It should start out at 58 to 60 psi at idle, and only drop to approx 54 psi at wide open throttle.
Does the car still have the stock fuel pump? If the car has the stock pump, I would install an aftermarket performance fuel pump in it's place.
We normally shoot for 8 psi of boost on a stock bottom end, all you should have to do is install a larger pulley on the supercharger's head unit. Bob
Was the fuel pressure being monitored? It should start out at 58 to 60 psi at idle, and only drop to approx 54 psi at wide open throttle.
Does the car still have the stock fuel pump? If the car has the stock pump, I would install an aftermarket performance fuel pump in it's place.
We normally shoot for 8 psi of boost on a stock bottom end, all you should have to do is install a larger pulley on the supercharger's head unit. Bob
11-10-2006, 07:28 AM
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The car only had 9 deg of timing in the high and low octane tables with the mailorder tune. I added a few deg of timing and saw KR. I then recomended to swap to a larger blower pully.
A/F was 11.50's for most of the pull. Then went richer past 5000 rpms.
A/F was 11.50's for most of the pull. Then went richer past 5000 rpms.
11-10-2006, 07:43 AM
#4
15lbs is definetly too much boost for a stock bottom end. shoot for 7-8 lbs. Those are very poor numbers. did they monitor the A/F while dynoing? All the LS1's I have tuned with stock bottoms and 7-8 lbs of boost made 480-500 RWHP. I would lower the boost and get it tuned again and make sure they keep the A/F at a safe level......