SStillSSmokin

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.

VINCE

iTrader: (1)

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.

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.

kcshaner

I went from 479 to 522 just by opening my cutout on my turbo car last Friday

SStillSSmokin

Only one pull after opening it. Had never heard that the pcm needed to learn it before...interesting. And we did move the wideband pickup to the cutout. I guess it will help when I get to do more to the motor.

TheBowtieboy

iTrader: (6)

I challenge that.

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.

M6HuggerSS

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.....

SStillSSmokin

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.

BAIN

iTrader: (5)

When my car was stock internal it gained 15hp 20tq when I opened up the cut-out on the dyno. It also picked up .15 and 2mph at the track.

soslo

iTrader: (12)

back to back pulls...only lid & tuning...

mrr23

iTrader: (3)

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.

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.

RyanJ

well, i never gained nothin...maybe my mufflers just messed up

luv2spd

iTrader: (1)

The MAF is the main authority at rpms over 4000 during steady state conditions so it would affect the afr at wot.

JimMueller

iTrader: (9)

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.

marc_w

Isn't that 4000rpm in closed loop though?

WOT will put the PCM in open loop...

SStillSSmokin

The MAFT adjustment for WOT seems to work great! It has a base setting and a WOT setting. The computer seems like it learns the base setting after driving it awhile. I searched to see if this is fact or not, and couldn't find much on it. My avg. LTFT's were around -2% a couple days before the run, so the base should be good. When I made the WOT adjustment 2% leaner, it showed that it made a difference.
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.

marc_w

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.