I had my fast system tuned on a dyno last week and I am curious as to why the torque was so low. The best pull was at 597 hp/ 495 lbs at the wheels, maximum 6k rpm. The boost was 24lbs and the timimg was a safe 18 degrees and A/F at 11.05. Would the small cam 218/212 be the reason? Turbo is a t76 q trim with a 3.5 downpipe. Motor is a 280 inch stage 2 offcenter with gn1 heads. Champion stock style manifold with worked stock TB and hemco plenum.
dyno results low torque??
- Thread starter rtviper
- Start date
I talked with 1 of the buick gurus and he mentioned I was probably losing 50 hp or much more with the 18 degrees of timing. Could this be parrt of the problem? He said to go to 24 degrees. I want to be very safe with the 116 octane fuel and no knock detector.
Hmm, well the cam could be part of it. What rpm did you see max boost at? Was that all the boost the turbo would make, or was it wg setting limited? I assume at that power level it was probably still wastegating?
I agree, 18 deg advance is probably pretty conservative at that flow level. But I also agree with you, better safe than sorry there. It can probably handle 22-24 deg at that boost/flow level (again based on the above assumption that could be wrong), but is also probably getting near the edge by then IMO.
Another factor might be the "shape" of your timing curve. Often IME they get shaped pretty strange (lol) and that can leave torque on the table...
And how much stall speed do you have?
TurboTR
I agree, 18 deg advance is probably pretty conservative at that flow level. But I also agree with you, better safe than sorry there. It can probably handle 22-24 deg at that boost/flow level (again based on the above assumption that could be wrong), but is also probably getting near the edge by then IMO.
Another factor might be the "shape" of your timing curve. Often IME they get shaped pretty strange (lol) and that can leave torque on the table...
And how much stall speed do you have?
TurboTR
The motor has a heavy duty stock style wastegate on it set as low as it can be. As the car was tuned the boost kept rising as he raised the A/F ratio, to the 24 lb range where he stopped. He said the wastegate will not hold the boost at a lower level. The car has a 4500 stall so when the boost came on in the mid 4k it would run right up to the 24lbs and he let off when it hit 6k rpm for no reason other then my shift light was set at 6k. At the lower rpm level he had as much as 21 degrees of timing, to the 18 degrees as it came into boost. When it was very rich in the 9.9 A/F it would boost to 19lbs at 490 hp then as he leaned it out the boost would go up accordingly to the 24 lbs that he stopped at. He said no use in tuning untill I put on an external wastegate. If the change to 22 or 24 degrees is close to the edge I will live with the 18 degrees. If I can go to 24 and still be safe I will do that? Thanks
This dyno operator uses mph not rpm on his graphs. The motor came up to 500 hp at 70 mph in high gear T400 trans and climbed to the 590 mark by 85 mph and then it stops at 100 mph as the motor is shut down? If that is what you asked? I have 1 of the graphs and it is a lower one at 577hp and 489lbs and it has a line through it from top to bottom that represents x. The side note says X= 92.8 mph. Sorry but this is all greek to me. It is one of the 1st buick dyno tests that I have seen that torque is less then the hp ? Guess what I would really like to know is, am I really leaving 50 plus hp unused with the 18 degree of timing
Do you have a BHJ balancer and has it been checked to verify the timing is correct? I had to change the ref angle 3 deg in fast to make it read the same in the timing map as the timing light 
You really need to check this because i believe BHJ sets the reluctor ring on the retarded side to cover there butts To do this you need to make sure the TDC mark on the balancer is right so you have a known good ref for the timing light. If you dont check this it could be 15deg timing instead of the 18deg you think it is I would think 24deg timing at 24 # boost is safe with a target AFR at 11 to 1 and C16 Ive been running my car like that for years with 9.2 to 1 comp ratio
You really need to check this because i believe BHJ sets the reluctor ring on the retarded side to cover there butts To do this you need to make sure the TDC mark on the balancer is right so you have a known good ref for the timing light. If you dont check this it could be 15deg timing instead of the 18deg you think it is I would think 24deg timing at 24 # boost is safe with a target AFR at 11 to 1 and C16 Ive been running my car like that for years with 9.2 to 1 comp ratio Geno yes it has a BHJ balancer on it. I guess you can check that out for me when I have you put the wastegate on for me. I will contact you by the end of the week to see if you have time before turbo thunder. I may not use the razor kit I have at your shop as the car is really too noisy for a street car so I may just use it as a strip car and use c16 gas. Thanks
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