[Nacs Fab]

I have narrowed down my timing and before I make my first pull, I thought we could discuss it here to make sure I don't mess up!

Specs: 455" at 9.5:1 static, with 84mm Torqstorm Centrifugal Supercharger and 3.1 pulley. CSU 750 e85 Carb for blow through. Aeromotive 13202 bypass regulator - boost referenced. MSD Boost Timing Master to pull timing (can pull 15° at max boost), MSD 7AL-3 Box has other timing functions if needed.

The Blower is capable of 20+ psi but I figure a solid 16psi may be about it. I am starting at 34° Total Locked. I figure the BTM ill start at 1 Psi, pulling timing - let me know if I should change this. My curve should look like this (target is 19° under full boost):



I'm always going to use the recommended 1° per PSI setting on the BTM because turning the dial up 2 and 3 degrees flattens out the timing curve too early in my opinion and creates more heat in the exhaust. Im looking at these AFR's: Idle 14.0 - 14.7, Boost Transition 12.5, Moderate boost 11.5 - 11.8 and Peak Boost at 10.8 - 11.2 keeping it below danger zone of 12.0. Please recommend AFRs here on gasoline scale if you have them.

I am asking for your input, so please let me know what you all think.

[JLMounce]

Starting at 1* per PSI is a good place to start. Though your blow through carb with e85 may not necessitate early timing drops below a certain threshold. You've got a lot of IAT cooling in that type of setup.

Unless you're trying to maximize fuel economy, I'd like to see your idle AFR's a little richer to help with cooling and idle stability. I also might lean a little richer in your mid-boost range, probably 11.2-to11.5 range. Not a ton, but enough to add some extra cooling capacity from the fuel.

[charlie66]

With a E85 blow through, usually is not going to be happy at idle with a AFR any leaner then 13.5 without cruising on and off throttle issues. I'm not saying not to shoot for it. Just if that is the case don't fight it buy having it set in your mind that it has to be 14 or above to be right. Mine is at 13.2 at idle because that's what it wants. Any more it just won't run right off idle and cruise.

Good luck I hope you don't run into the same thing I did.

[GOAT8U2]

I was curious how your build was coming along, you're on the right track. 16psi at 9.5 compression isn't anything crazy with 19 degrees timing but this on 93 octane, then intake temps (intercooler)?

Fuel and intake temps can be variables on a heavy car in the Summer with FI. If you can run even E30 blend you'll gain more headroom for safe power yet only need to richen it up a little.

[Nacs Fab]

Originally Posted by GOAT8U2

I was curious how your build was coming along, you're on the right track. 16psi at 9.5 compression isn't anything crazy with 19 degrees timing but this on 93 octane, then intake temps (intercooler)?

Fuel and intake temps can be variables on a heavy car in the Summer with FI. If you can run even E30 blend you'll gain more headroom for safe power yet only need to richen it up a little.

Im not intercooled but running E85 Carb so should be okay.