Rev Limiter FAST or MSD

[dhegge]

Guys,

Question which rev limiter should be used the FAST rev cutoff or a chip in an MSD 6AL? I have been told that the MSD has a soft rev limiter that is better for the engine. What do you guys think? Currently I have the MSD chipped at 7000RPM and the FAST @ 6800 RPM. So the FAST is rev limiting before the MSD.

Thanks,
Doug
375CI SBC TT (1008HP/850TQ)

 

[bobc455]

Doug,

I prefer the rev limiter of the MSD.

The FAST limits revs by cutting off fuel, and I'm worried that could lead to a few lean comubstion cycles when it cuts out and cuts back in again (and I don't like going lean at WOT). On an SFI unit I could see it working well, but on a B-B unit I would be worried about the lean thing.

On the MSD, the worst that can happen is a few combustion cycles with no spark (and no combustion) which still isn't theoretically ideal, but practically it is much better to dump some raw/unburnt fuel out the exhaust than to risk the severe detonation (and associated engine damage) from running lean.

Just my opinion.

-Bob Cunningham
bobc@gnttype.org

 

[Craig Smith]

I also prefer to use an ignition-based rev limiter than a fuel-based one, so I would recommend using the MSD limiter.

All you can do with a fuel-based rev limiter is turn the injectors on and off at certain RPM. An ignition-based system can actually hold an engine at a certain RPM, which is a better method in my opinion.