Roe SC a/f ratio?

[RStoker]

Just had my viper dyno'd with the new Roe SC installed. I wanted to make sure the a/f ratio was at an acceptable level. My a/f starts out at 12 and half way through the rpm range it's at about 11.8 or 11.7 and ends up at about 11.5. The guys at the shop said my a/f was a little on the fat side. What do you guys think? I had a 03 Cobra and the a/f on that stayed between 12.1 to 11.9. Do I have room to improve or should I just play it safe? BTW if anyone is interested it pulled 521 rwhp and 545 rwtq on the 5# pulley. My only other mods are smooth tubes, k&n filters, and hi-flo cats. Before the SC I pulled 410 rwhp so that's about a 28% increase.

 

[PBJ]

Rstoker,
I would go in and pull a little fuel out of the fuel RPM cells to bring it back up to 11.8 to 12.0. 12 to 1 is still a safe tune in my book. You should pick up some more horsepower and torque by smoothing out the a/f curve. Just go into each cell and add or subtract to smooth it out. I sat on the dyno for a couple of hours and pulled 618 and 633 on the last kit...it was a stock '97 with exhaust. If you don't have the software from sean, just send him the dyno sheet and a card and he will make the changes for you. If you do have the software, he will sent you a new program via e-mail. He is pretty cool about walking you through his software and helping you make changes. Once you get the hang of it, you will be making all sorts of changes to peak everything and customize Sean's base settings.
Hope that helps,
Joe

 

[whip383]

let me get this straight, Joe, u pulled almost an extra 100 rwhp,(approx. 200 from stock), more than RStroker? that is freakin awesome. Same set up? hum.........

Chan

 

[Sean Roe]

Hi Guys,
That's about right for a stock motor with a standard 6D card on 93 octane fuel (assuming). Before proceeding, I would make sure all my dyno testing conditions were correct, as in, proper tire pressure (36 PSI), oil level, carpet mat removed, full throttle checked, etc..).
Without seeing the curves and going by how Robert describes them, it sounds like a standard condition for how we program them "safe". If you were to want to optimize the program, the best approach would be to inspect the plugs first. If there is no sign of pre-ignition / detonation (looks like tiny beads on the porcelain), I would begin reducing the timing retard between the 4,000 and 6,000 RPM range on the VEC2 ignition RPM page. When the retard is reduced / timing advanced, the fuel is lit earlier and burned more completely in the combustion chamber. The result will be a net "leaner" exhaust AF ratio and the HP will go up accordingly. With a little tweak like this, the HP will go up to about 540-545 at the rear wheels and more if you want to run race gas and actually advance the timing in the midrange.

As Joe said, we can e-mail new programs to people and are happy to do so. Someone will fax us a dyno graph while their car is on the dyno, we'll make changes to the program they're using and e-mail it back to them. It all takes a matter of minutes.

In regard to the power Joe got out of that car, I think it was with 8 psi and a tweaked program.

Regards,
Sean

 

[RStoker]

Hi Guys,
That's about right for a stock motor with a standard 6D card on 93 octane fuel (assuming). Before proceeding, I would make sure all my dyno testing conditions were correct, as in, proper tire pressure (36 PSI), oil level, carpet mat removed, full throttle checked, etc..).
Without seeing the curves and going by how Robert describes them, it sounds like a standard condition for how we program them "safe". If you were to want to optimize the program, the best approach would be to inspect the plugs first. If there is no sign of pre-ignition / detonation (looks like tiny beads on the porcelain), I would begin reducing the timing retard between the 4,000 and 6,000 RPM range on the VEC2 ignition RPM page. When the retard is reduced / timing advanced, the fuel is lit earlier and burned more completely in the combustion chamber. The result will be a net "leaner" exhaust AF ratio and the HP will go up accordingly. With a little tweak like this, the HP will go up to about 540-545 at the rear wheels and more if you want to run race gas and actually advance the timing in the midrange.

As Joe said, we can e-mail new programs to people and are happy to do so. Someone will fax us a dyno graph while their car is on the dyno, we'll make changes to the program they're using and e-mail it back to them. It all takes a matter of minutes.

In regard to the power Joe got out of that car, I think it was with 8 psi and a tweaked program.

Regards,
Sean

Sean, the inside of the door jamb says to keep the tires at 29 psi cold so that's where I have them. What effect does this have on the dyno pull? BTW, it was a 6D card. Also, what will adding headers do for me?

 

[PBJ]

Rstoker,
Sorry, I didn't see the 5 # pulley reference. Sean was correct, mine was on a 8 # kit.
Joe