New CTSC -- A/F Measurement

[jmp]

Just had the new CTSC installed in a 1991 with H/E/Cat Bypass/Lt. Flywheel. Dynoed using a Dynojet drawing from the tail-pipe today. BAD NEWS: Had to stop prematurely due to overly lean A/F (above 13 with fuel regulator as rich as the screw can adjust). GOOD NEWS: 6600 rpm's yielded 311 whp and sharply increasing.

Comptech believes the cat bypasses may be causing an erroneously lean reading frm the tail-pipe, and suggested having a temporary bung draw the A/F from the header.

Any insight, comments or experience with this would be greatly appreciated, while I wait to get the car to a dyno where they can install a bung??? Thanks.

 

[makena88]

Just had the new CTSC installed in a 1991 with H/E/Cat Bypass/Lt. Flywheel. Dynoed using a Dynojet drawing from the tail-pipe today. BAD NEWS: Had to stop prematurely due to overly lean A/F (above 13 with fuel regulator as rich as the screw can adjust). GOOD NEWS: 6600 rpm's yielded 311 whp and sharply increasing.

Comptech believes the cat bypasses may be causing an erroneously lean reading frm the tail-pipe, and suggested having a temporary bung draw the A/F from the header.

Any insight, comments or experience with this would be greatly appreciated, while I wait to get the car to a dyno where they can install a bung??? Thanks.

after putting in my AEM, Walbro Fuel Pump, AEM AFR, RC 550 Injectors, & AEM Wideband, I'm running 12:1 all the way across. (using high-boost)

I had the same problem as you before I upgraded to a AEM system

 

[MiamieNeSeX]

GOOD NEWS: 6600 rpm's yielded 311 whp and sharply increasing.

Not to good if it indeed was running lean. LEAN = MORE HP = CLOSER TO THE EDGE.


Armando

 

[jmp]

Armando,

Your point makes sense except that my earlier pulls (before we enriched the regulator) were running lower hp at same rpm, with higher A/F ratios. Mechanic thought the car was needing the fuel. Not sure what to think.

Comptech says to measure a/f at the header. Does this make sense to anyone?

 

[makena88]

Comptech says to measure a/f at the header. Does this make sense to anyone?

We did this at our shop and there was not too much difference, was still running lean. (13:1 to 14:1)

 

[MiamieNeSeX]

Do you still have the factory fuel pump installed?


Armando

 

[jmp]

yes, oem fuel pump. Soone suggested that the comptech regulator needs to be checked for volume/pressure also. Thoughts?

 

[BadCarma]

Not to good if it indeed was running lean. LEAN = MORE HP = CLOSER TO THE EDGE.


Armando

Armando is right on the money,its the first thing I thought of when you posted your hp.

makena88 posted some very useful info and just my o2 but I would goe his path with your setup if you want to stop chasing gremlins now and later.

best regards and good luck David

 

[ryan1926]

I am curious as to the Air/Fuel ratio variance between CTSC installs. I have a '95 with the new Autorotor unit and my Air:Fuel ratio is fine. I am assuming that you are running the ACM module, right?

http://www.nsxprime.com/forums/showpost.php?p=584691&postcount=16

 

[jmp]

Ryan1926,

Before Comptech ran the dyno/tuning what was your A/F ratio? Your thread link says you were lean before they tested it. When Comptech ran it where did they draw from? Thanks.

 

[ryan1926]

Ryan1926,

Before Comptech ran the dyno/tuning what was your A/F ratio? Your thread link says you were lean before they tested it. When Comptech ran it where did they draw from? Thanks.

Actually, no tuning was done. My original Air:Fuel ratio reading was done at Turbohoses where they measured at the tailpipe. Hoover at Turbohoses also used a stethoscope to listen for any detonation and he couldn't hear anything. I forgot to mention that when I first posted so it appeared that I was running lean because the cats were basically doing their job. I then took my car as is to Comptech and they tested it on their system. I'm not exactly sure where they measured it, but they plugged in somewhere in the engine bay, pre-cats of course. Maybe you can give Billy and Ryan a call at Comptech for a more accurate explanation. I hope this helps.