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formerly Kit88
ek hatch
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Discussion Starter #1
Pros an cons of using rev limiter w/fuel cut, ignition cut, or both.

Please comment your experience.
 

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I've never done anything but fuel cut. I don't see the point in doing ignition cut. I do know that when we cranked an engine with the spark plug wires out and the MPI fuse still in there was spontaneous ignition from the compressed fuel. From that experience I wouldn't do ignition cut only.
 

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1993 Cobra
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I think they cut ignition rather than fuel...dont want to lean out with all that air and fire ya know.
 

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formerly Kit88
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Discussion Starter #7
its obviously reliable if it comes like that from the factory.

i figure it came like that for a reason
I understand that, but on a turbo setup, it it´s not safer to use fuel+ignition cut??

On a boosted car using FTL with just fuel cut, it will create a lean conidtion, this is not good rigth??
 

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formerly Kit88
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Discussion Starter #9
no fuel is a lean condition , isn´t it ???
 

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formerly Kit88
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Discussion Starter #11
good point
 

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Free air sparks are no big deal. Fuel cut is the safest way to limit revs. That is basically what happens on decel and at redline.

Personally I don't like using ignition cut for anti-lag studders. I like being in control of combustion timing. Those pops you hear when someone is on the 2-step with ALS? Spontaneous combustion. Can't be good for your bearings if they occur BTDC.
 

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fuel cut doesnt cause a lean condition.. well i mean on the wideband itl say lean, but if theres no fuel there, it wont be lean...
 

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formerly Kit88
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Discussion Starter #16
there will still be enough fuel in the combustion chamber to create a lean condition. bouncing a boosted car off the rev limiter with just fuel cut is a bad idea

just use both
Yeah, and I can build more boost with fuel and ignition cut it at FTL.
 

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Kinda glad this topic has popped up.. I recently purchased (havent got it yet) a Bee*R rev limiter because Im running a carb setup, no ECU etc. So ignition cut was my only option.

Was this a bad choice? Its not like I plan to be on the limiter all the time, but I dont want to do any damage on the odd occasion when I am.
 

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Free air sparks are no big deal. Fuel cut is the safest way to limit revs. That is basically what happens on decel and at redline.

Personally I don't like using ignition cut for anti-lag studders. I like being in control of combustion timing. Those pops you hear when someone is on the 2-step with ALS? Spontaneous combustion. Can't be good for your bearings if they occur BTDC.
When you hear those "pops", it's unburned fuel/air mixture lighting in the exhaust, not in the chamber itself. The rapid expansion of combustion in the exhaust helps to spool the turbo rapidly. There is no danger to the engine doing this for short amounts of time. Extended amounts of time could result in lubrication oil being washed off the cylinder walls from fuel, and eventual exhaust valve over heating.

It is harmless after burn, and the only thing at risk is damage to the turbo from the rapid pulses passing through the turbine.

-Luke
 

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Brokedick Millionaire
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Good to see you Luke!!!!

Hugo, I used a MSD 6AL set at 7800 rpm spark cut, ECU was set at 8500 rpm fuel cut when spraying nitrous.

You never wanna cut fuel when on the hose, you may pop a muffler or exhaust pipe, but those are cheap!

No idea while on boost, I would refer this to Blundar and Joseph Davis.
 
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