Roe Sc and 91 octane

[varanus]

Is anyone running more than 5psi on a 96 to 99 forged car with 91 octane gas? Just wondering how much boost you ran and how much timimg you had to pull out. Or if you just ran some race gas mixed in.

 

[Sean Roe]

Hi Kevin,
If you run a 7 psi pulley, you (or I) could write a program to keep the timing down to about 18 degrees advance total when running 91 octane. When you put in higher octane fuel to mix, or an octane booster, you can slide in a higher timing program card, running 22 degrees advance total. With 100 octane, you can typically run about 28-29 degrees total advance. Let me know if you want me to help you write or e-mail you a program.
Regards,
Sean

 

[Bob D]

Kevin,
I have a 98 with a 7 psi pully with 91 octane and have no problems at all. I dynoed 610 rwhp/ 664 tq about 2 weeks ago. I picked up 15 hp and 68 tq by fine tuning the fuel on bank 1 and 2 separately with the VEC2 and LM-1 wide band. The total timing advance is 24 degrees but this is at 5500 ft elev. I think generally you can advance about 1 degree per 1000 ft elev. gain above sea level. This works out with Sean's 18 degrees at sea level. Soon I'm going to mix in some 100 octane and make a 93 or 94 octane card.

Bob David

 

[proracer1]

I am running a 8lb pulley and have the stock cam, cly head work. aftermarket pistons and rods(for strength) Making over 700 RWHP no probs.

 

[Bob D]

proracer1, Is that on 91 octane?

 

[varanus]

Bob, what size injectors are you running?

Did you have any detonation isues at all?

 

[Bob D]

Kevin,
I'm running 50 lb injectors. I tried the 40 lb but was running out of fuel around 5000 rpm. The stock fuel system seems fine, probably due to the altitude I'm at. The A/F ratio is adjusted to 11.8 at WOT. I'm running as much advance timing as I can without detonation. The only times I've had detonation is in testing how far I could go. One thing I've learned is that it's better to do all this tuning on the road. I found that I run about a half a point richer on a dynojet. If I tuned for max power on the dyno, it wood run leaner than I wanted to in real conditions on the road.

 

[varanus]

thanks Bob. I just got some 50lb injectors from Sean. Did you start a program from scratch or adapt one from sean? Did you tune on the dyno, then add fuel across the bord using a wideband 02 while driving to check?

How much more room to you think you have with the stock fuel system and 50lb injectors. I upgraded to a walbro 255 fuel pump.

 

[Bob D]

Kevin,
I started with Sean's card and with help from him and what I've learned along the way, ended up with something quite different. Tell Sean what mods you have and he will send you a card that's close to start out with.
I tuned on the dyno before I got the wide band. You can at least get the AFR adjusted flat. You need to check your bank 1 and 2 long term fuel trims and adjust them so they are even. It wasn't until got the WB that I could see the difference between each bank. I welded a **** on each side, pre-cat. Checking the AFR while driving is the best way to go and also gives you another excuse to do WOT runs in 3rd or 4th gear. If you don't already have a wide band, make sure you get one that records and downloads to a computer.

If I were at a lower altitude I'm sure I would be pushing my luck with the stock fuel pump.

 

[proracer1]

93 octane Sorry