Superchips Tuner on 87 octane runs Better?

[Arnolds97]

Have any of you experience a Superchips Maxtuner that when you select the 91 over the 87 octane tune that it does not seem to run as good. With the 91 it seems to have a little more throttle response but midrange up it does no seem to run as good or rev as smooth. Less power? I have switched it back and forth several times and thought I was crazy but I don't think so. It also get less mpg with the 91 level. Custom tune need most likely instead of the cookie cutter one . Anyone?

Mods to engine are just bolt ons - C&L Upper manny with a 75mm BBK T, BBK cold Air, No cats H pipe and Dynomax Super Turbos (Replaced Flowmaster 50's on the Flowmaster catback , March UD pulley. Rearend and trans are 4.10 gears with 5 speed.

 

[wmburns]

Some underdrive pulleys can cause problems the quality of the crank shaft possition (CKP) sensor signal. Especially piggy back style. This can show up as misfire or loss of power.

The CKP signal can also be affected when the damper bolt has not been torqued correctly.

Since the 91 octane tune makes more power by advancing the timing, it is possible that the 91 tune may be more affected by an unstable CKP signal. For example, the extra power being made by the 91 tune is being offset by additional misfires caused by a weaker CKP signal.

 

[Arnolds97]

March Pulley.

I have the one piece March Pulley SFI version which is really nice. It had Piggys on it and I took it off. I do not know how this could be a problem. The Bolt was torqued to spec too. No wobble and aligned perfect with all the other pulleys so I know it is seated. It runs good without a miss but just seems rough or something not as smooth.

 

[trinity_gt]

Can you do some logs and see what the timing is doing for both tunes?

My suspicion would be that Superchips is simply trying to be too aggressive with the timing in their 91 tune. And you're right, a custom tune > cookie cutter any day.

Also, lose the IAT resistor. Trying to fool the PCM by lying to it about intake air temperature is only going to interfere with proper fuel and timing delivery. Ford spent thousands of hours of R&D and dyno time and incorporated all the physical and chemical properties of air into its calibration data and algorithms and they got it right. There's no benefit to making the PCM think the air is cooler than it actually is. If you want more fuel up top (e.g.) at WOT, use your tuner.

 

[wmburns]

Can you do some logs and see what the timing is doing for both tunes?

Also, lose the IAT resistor. Trying to fool the PCM by lying to it about intake air temperature is only going to interfere with proper fuel and timing delivery. Ford spent thousands of hours of R&D and dyno time and incorporated all the physical and chemical properties of air into its calibration data and algorithms and they got it right. There's no benefit to making the PCM think the air is cooler than it actually is. If you want more fuel up top (e.g.) at WOT, use your tuner.

Outstanding call/catch!

I went back and looked at the OP's sig and then saw the IAT resister. I agree 100%. An ODB2 PCM need accurate sensor data. It creates more problems trying to "lie" to the PCM. Better to create a tune from accurate data.

Also datalogging is a great idea to help narrow this down.