TD in DC

If it cuts spark only, then it really should not hurt the car to hit the rev limiter. If it cuts fuel as well, then it could create a lean condition.

How does the stock rev limiter work, and am I thinking about this correctly?

For the record, I never intentionally hit the rev limiter, but it is easy to do during races (like during the start).

Perry 951

I believe it cuts spark only. Fuel cut, as you said, is not a good way to do it. The massive flames you can get from open exhaust while on the limiter should indicate spark cut.

Either way, it's not a great idea to bounce a large rotating mass at 6750 RPM!

TT

Fuel only.

TD in DC

This seems very hard to believe. Source?

special tool

HE is the source.

Most anything factual you will read about the 951 Motronic programs originates from him.

TD in DC

OK, I am not trying to be disrespectful, I just don't automatically assume that strangers on the Internet know what they are talking about.

Now, is it save to assume that the 944 and 951 Motronic programs operate the same way with respect to rev limiters?

Isn't it horrible to have only fuel cut? Would that be bad on the engine?

TT

Code in the DME.

Same exact fuel cutoff for redline as during deaccel. Don't believe me, rig up a timing light inside your car and go hit the limiter.

When you cut the fuel it goes extremely lean (no fuel, > 19:1 AFR). There is nothing to burn.

TD in DC

OK, so how hard on the engine is it to hit the rev limiter. I am not talking about intentionally leaving the car bouncing off of it, but rather hitting it during starts of races, at specific corners, etc . . .

TT

Now you're into the mechanicals and I would have to agree with Perry, it can't be good for the engine or drivetrain. I don't know if your class rules allow it, but if you can, get someone to raise your rev limit to at least 6800. I used to hit the stock 6500 limit occasionally and found the MY88 limit of 6700 was much better.

J Silverman

The 88s have a higher limit? I guess that explain why I can rev to past 6500. All this time I just assumed the PO installed some sort of chip in the car. I even pulled the DME to look at the chip, but it looked factory. Thanks for the info!

Perry 951

I stand... informed!

Thinking about it twice, cutting fuel would be a sure non-fire way to stop the motor from turning. Auto-ignition could happen if fuel continued to be dumped into hot chamber and keep the thing revving.

TT - why the flames if no fuel?

Wipeout

Interesting. Didn't know there was a limiter (clearly I'm not living on the edge.) :P

GodSpeed

Cutting only fuel is a very dangerous way to do this. Especally on a boosted engine. It creates a very lean condition and as you all know that makes heat, detonation, melts parts togeather, burns rings and removes chunks out of the piston crowns. I would avoid the limiter!

schnellfahrer

TT, what is the rev limit on the Vitesse Chip Board?
Fuel cut or spark cut?

TT

The board has two rev limits. Unless John changed them, I set them to 6700 without the coding plug (pump gas setting) and 6900 with the coding plug (race gas setting). Check with John to make sure.

Fuel cut is like stock.