any one know if there is a soft rev limiter out there (i.e. no fule cutoff but spark instead)?

i really don't feel comfortable having the fule cut off on a boosted application and the hard cutting on and off motion really hurts the belts on a blower.

 

could a harlan 2 step work for what your looking for?

I know it cuts off spark, but unsure if you can keep it on all the time?

Maybe in combination with a window switch set 100 rpm's lower, it could work for what your looking for.

Ryan.

 

.... interesting, never thought of that.
i was thinking more like a msd box or something like that.

 

i have not seen any msd stuff for the LS1 ignition yet

doesn't mean it does not exist,just nothing i have heard of.

Ryan

 

I probably won't make the rev limiter any 'softer' if it cuts the cylinders off via spark rather than fuel. The rev limiter has to stop the rpms from climbing by disabling cylinders. Disabling cylinders, no matter what method, results in the drivetrain pulses you feel.
Don't use your rev limiter like a shift light. It's there to stop engine damage when a mistake is made. You should not hit your rev limiter regularly.

 

i agree, but i need a spark cut off revlimiter instead of a fule cut off one because the motor is boosted, and the softer it is the less stress it puts on the belts.

i don't know if you ever tried reving up a deisel engine, but it's strange how it pulls up to a certain rpm (it's redline) then gently stops there ( with no pulses), just like hitting top speed where your rpms just hang there. any idea how it's done?

 

Well, I'm not sure how a spark cut-off rev limiter feels in comparison but I don't guess it would be smoother. Besides, cutting off the cylinder is going to cut off the cylinder...shouldn't matter how (as far as danger in your boosted environment is concerned). I say this because no fuel means no burn, you seem to think that it WILL burn but will burn lean. I don't think this will happen.

As for deisel engines, they have a wide-open air intake at all times and rpms are limited by power output which is modulated completely by the amount of fuel being added. They can limit revs simply by modulating the amount of fuel being injected. In a drive-by-wire setup it would be possible for this form of rev-limiter to be implemented (say in the Corvette). It would certainly be a good way to go.

 

good call , never thought about the drive by wire aspect of it.
you're argument makes sence, but i also have to worry about how the sudden fall then rise of the rpm "shocks" the blower and its drive system.

 

Really, the rise and fall of RPMs when bouncing on the rev limiter is only 1-200 rpm. Not much. There are pulsations, or shocks, but I can't imagine that it's going to hurt the drive belt. Those things are really strong. If this were true, then engines with drive belts (OEM) with rev limiters would damage the belts every time the factory rev limiter kicked in.
How often are you planning to bounce off your rev limiter? Surely you only hope to hit the limiter accidentally. It's there to be a final safety mechanism when we've screwed up. You aren't hoping to use it like a shift light are you?

 

I can tell you that the Harlan two step is a lot "softer" than the PCM rev limiter. 100 or 200 RPM is still a large difference at 120 in fourth. Seems like it slows down a second or two before it picks back up. The one problem with the Harlan is that cutting off the spark and leaving the fuel on kills the cats.

 

Not to mention that the cylinders load up on fuel and a large backfire can/will occur when spark kicks back in.

 

Really? I haven't seen that yet, but I have a NA car and only got in a half dozen passed after the Harlan and before the snow.

Would you care to elaborate?

 

trust me , the shock of the rev limiter kills belts. i have a dedicated 8 rib belt now and it is so tight that you hear it ring when you tap it. thats how tight i have to run it to avoid slippage ( and it still slips). the problem gets even worse with a gog setup , cause they are so unforgiving when it comes to slip. remeber , my blower takes about 60 hp to turn so the momentum or enertia of the blwer is huge, and any shock is bad.

i see the point regarding the cats but i don't have any. but i don't see how leaving the fule on can hurt otherwise ( maybe washes the cylinder walls). But i really don't think it will ignite cause the spark will only come on after the second air fule mixture charge is reintroduced into the cylinder, not to mention the excess unburnt fule from the first charge will be evacuated when the exhaust valve is opened.

 

I believe you!
I don't think it is a problem either. Like I said, I have one and have used it. I didn't have any backfire. In fact, on Harlan's site he has a clip of his turbo car hitting the two step. www.harlan-engineering.com, I think.

 

since we're on the subject of ignition; what ever happened to holley's ignition for the ls1 ( at least i think it's holley).
didn't they have something planned for release early this year?