First Dyno- cutout=0 hp over stock muffler?
#1
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First Dyno- cutout=0 hp over stock muffler?
Dyno'd the SS yesterday, am happy with results 343.6 rwhp/353.2rwtq. The only dissapointing thing was I got 341/349 on the first pull, cutout closed with a A/F of 12.3. Adjusted my MAFT 2% leaner and opened the cutout. Got 343/353 with A/F of 12.8. So I gained 2hp/4tq with leaning it out and opening the cutout? I would think most of this is due to better A/F. I was expecting at least 10hp from the cutout, I guess the stock SS muffler must flow pretty well.
#2
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Did you do one pull after opening the cutout? If so, that is why you saw so little gain. It takes the pcm another 2 to 3 pulls to notice the change. Everytime I have opened my cutout I have seen very little gain on the first pull. I make 2 more pulls and pick up close to 20rwhp.. Remember I have a bigger motor. Also, you have to measure the a/f at the cutout and not thru the muffler or your readings will be off.
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Originally Posted by VINCE
Did you do one pull after opening the cutout? If so, that is why you saw so little gain. It takes the pcm another 2 to 3 pulls to notice the change. Everytime I have opened my cutout I have seen very little gain on the first pull. I make 2 more pulls and pick up close to 20rwhp.. Remember I have a bigger motor. Also, you have to measure the a/f at the cutout and not thru the muffler or your readings will be off.
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Originally Posted by RyanJ
on a stock motor w/ the stock cam you won't gain that much from the cutout. Vince is probably right, but still...don't expect more than like 5 at the tires.
If it's the SS SLP Dual/Dual option then I would agree with you BUT if it's the GM stock SS exhaust you will see better gains then that which means that there are other factors at work.
#7
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with just LT's and a lid i gained 6rwhp 6rwtq on a back to back run.....
with all mods in sig i gained 20rwhp and 25rwtq on different days......
still blowing threw STOCK SS cat back.....
with all mods in sig i gained 20rwhp and 25rwtq on different days......
still blowing threw STOCK SS cat back.....
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#8
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Well what the hell? These were back to back runs. Only changed MAFT 2% lean and opened the cutout. Took about 5 min. between runs. Oh well, still happy with the #'s. Mainly wanted to make sure the A/F was good so I can hook up the nitrous kit I've had waiting around till I got the clutch in(it's in! )
*EDIT* Oh, and it's the base SS muffler.
*EDIT* Oh, and it's the base SS muffler.
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Originally Posted by RyanJ
on a stock motor w/ the stock cam you won't gain that much from the cutout. Vince is probably right, but still...don't expect more than like 5 at the tires.
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and here's another one. all stock exhaust then open exhaust. gained 11/13 after 3000 rpms. too bad i gained nothing at the track. doesn't take anytime for the computer to learn anything from opening the cutout.
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Someone correct me if I'm wrong, but I don't think leaning out the MAF calibration will do anything for a WOT run...
I think the only thing that really matters (fueling wise) is your PE table and if you're running positive LTFT's.
I think the only thing that really matters (fueling wise) is your PE table and if you're running positive LTFT's.
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Originally Posted by marc_w
Someone correct me if I'm wrong, but I don't think leaning out the MAF calibration will do anything for a WOT run...
I think the only thing that really matters (fueling wise) is your PE table and if you're running positive LTFT's.
I think the only thing that really matters (fueling wise) is your PE table and if you're running positive LTFT's.
#15
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I prefer to use a front O2 bung for the wideband, or as close the engine as feasible. If you have catalytic converters it will skew your reading a few tenths. But regardless of the wideband sensor location, the expected power didn't materialize. Whichever location you use, I'd not change it while adjusting AFR to keep things simple. Do you have the cut-out in the typical location right before the axle?
I have heard that for best performance one needs to drive the vehicle for a bit to let it adjust. But I also pickup 30rwhp when going from the stock catback to the cutout in back-to-back runs.
Altering the WOT dial on the MAFT only effects above ~3500RPM at WOT, but it does work if you have your base set correctly. I do know I run about a 1/2 point leaner on the street with the cutout open than with it closed at WOT.
I have heard that for best performance one needs to drive the vehicle for a bit to let it adjust. But I also pickup 30rwhp when going from the stock catback to the cutout in back-to-back runs.
Altering the WOT dial on the MAFT only effects above ~3500RPM at WOT, but it does work if you have your base set correctly. I do know I run about a 1/2 point leaner on the street with the cutout open than with it closed at WOT.
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Originally Posted by luv2spd
The MAF is the main authority at rpms over 4000 during steady state conditions so it would affect the afr at wot.
WOT will put the PCM in open loop...
#17
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Originally Posted by marc_w
Someone correct me if I'm wrong, but I don't think leaning out the MAF calibration will do anything for a WOT run...
I think the only thing that really matters (fueling wise) is your PE table and if you're running positive LTFT's.
I think the only thing that really matters (fueling wise) is your PE table and if you're running positive LTFT's.
I know that the MAFT is basically an obsolete "tuning tool" I was just hoping to use it as a temp. fix for the AFR till I can get HPTuners. Oh well, my WOT AFR is good, and I made good power(I think) for the mods I have.
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Sounds good...
I'm not familiar with MAFT's at all - I was just trying to offer some outside tuning help. I didn't realize they had something different for WOT mode...
You should really like HPT - you get free reign of your entire PCM.
I'm not familiar with MAFT's at all - I was just trying to offer some outside tuning help. I didn't realize they had something different for WOT mode...
You should really like HPT - you get free reign of your entire PCM.