I recently hooked a WideBand up tp my 89 GTU with the following mods, No Cats, Bonez mid pipe, Racing Beat cat back, working 6-ports (set at 5.2K), K&N filter and Cold air box)

I was feeling a loss of power at about 7K (more than expected), after adding the racing beat exhaust and was thinking it was running lean... WELL, the wideband told us different.... Here are the numbers.. RPM then Wideband Reading...

5000 13.5

5500 13.1

6000 12.8

6500 12.3

7000 12.1

7500 11.8

These are average over several FWO pulls from 4K to 75000 in 2nd and 3rd

As you can see, she's getting richer as she gets higher in RPM... These numbers are closer to what my buddy's single turbo third gen runs at 20lbs of boost than i would expect for a N/A 2nd gen.... Doctor Dave at KD Rotary suggested low 13's all the way for an N/A.

SOOOOOOOO.......

Right now... I'm running from 15.1 to 15.4 Seconds consistently at the track....

Will adding an S-AFC and taking some fuel out in this range increase my horsepower on the top end enough to get me into the 14's, or aint it worth the 300 buckeroo's????

AND... is there anything else I should be looking for.. I know this car can go 14's without running a bottle.. but, if its going to take 10 grand to do it.. screw it.. i'll buy a TII!!!

 

with the mods you have, you should have already had an S-afc. The stock fuel system sucks ***. Get an S-afc, tune your car, then run it till it blows.

 

no, the stock fuel system can handle a lot. I've heard up to 190rwhp can be achieved with it. He's running RICH remember? That means he has too much fuel, which means that the fuel system is overly adequate.

 

Ther are definite gains to be had be leaning out those mixtures a bit. It won't be heaps, but it will be noticable. Tuning like this should only be done on the dyno though.

 

Decay, what fuel ratio are you targeting?

 

w/o a dyno an EGT gauge would help too...the NA fuel system is more than adequate for any NA setup that is still fuel injected. The ECU is what is making the mixture richer and richer as you wind the motor out. expect about 10 or less hp to the wheels from about 6K on when you take some fuel out. do it on the dyno though, really the best way to do these things. an NA should hit the 860 celcius mark as a ceiling for EGT numbers under 4th gear WOT (w/ the probe right after the manifold).

 

well, the Doctor told me to shoot for about 13.5 A/F... i thought 11.8 was way rich....

 

That's about right.... Racing beat techs have told me that while every engine is a little different (mods, etc)

The best power will com from around 13:1 in the low-mid to almost 14:1 at redline.

I LOVED my S-AFC. I don't think I got more than 10 peak hp at redline (well, maybe 15...) but the midrange increase was fantastic. Typically N/A's run rich in the midrange, and can be leaned out a LOT.... it brought back at least as much low-midrange as I had before I took out my 6port sleeves. Pretty cool!