Stopping a turbo motor w/ new rev limiter cut patterns

[Jon K]

Hey guys - flashed my personal unit to v.66 the other day and set up the cuts. Personally I can't see needing 5 different cut patterns but its cool none the less.

On my car I am running direct port methanol/water injection. I have the cut setup for spark only since I worry about there being residual methanol/water (its 50:50 ratio) phasing out as the rev limiter is hit - I don't want it to combust that mixture accidentally and detonate/etc. So, by not turning off fuel injection at least it will continue to fuel based on the map and the spark will just blow out - might result in some fire out the pipe but I can deal with that.

However, since I am running a turbo car I have noticed that when I set it for like 88 or 83% cut or whatever, she really starts to build boost - likely because the fuel is burning in the exhaust somewhat like an anti-lag setup. No violent bangs or flashes out the back that I can tell, but I can hear the turbo start to whine up and the RPMs seem to climb too. This is with the limiter set at about 5000 RPM just to test.

I think I might need to cut fuel and spark, just kind of concerned doing that.

Thoughts?

[stevieturbo]

I dont believe the water/meth thing is a real problem...but anyways.

Most people are afraid to cut fuel, but on most educated forums it is actually the preferred method. Because they dont like dumping raw fuel into hot exhausts. Especially when it's a rev limit during an anti-lag/launch scenario
Racelogics traction control works by cutting fuel too.
Motec prefer to cut fuel and spark.


The whole notion about leaning out and doing damage just doesnt seem to be a reality, and that comes from people far more educated than me.
I can understand it....but for the most part I'd still prefer a spark cut myself. But Ive no actual evidence one way or the other

[Jon K]

Stevie I would 100% agree with you and I cut fuel on every other application, but cutting fuel on my setup makes me worried with the methanol. Since I am running an Aquamist setup with direct port there is some tubing that has to siphon after a pull - if it cuts fuel I will siphon the methanol/water mixture... I hope it doesn't ignite in the cylinder.

[Frallan]

Am I stupid if I ask if water/methanol can ignite at all?
It emulsifies/mixes well and maybe the methanol is burning and adding power but my thought was that in fact not.
It just lowers detonation level and cools and by that adds value.
The engine can be setup for more boost and optimized ignition. Then build more power.

This is not a statement. it is a question or maybe a speculation.

[katana]

If the alcohol is worrying you reduce its percentage? It has very little effect as an anti detonant when used with water - 100% water is proven better for anti-det properties and cooling. Plus its corrosive effect on aluminium is a PITA - piece of that trying to squeeze through the nozzle will really cramp your day LOL
Fuel cut is the easier on an engine - lean out doesn't occur! If the tap is off, nothing flows out - no fuel = no burn = no lean condition!

[ibizacupra]

for sharing info...
water meth will burn (combust) thats one of the reasons we use it, chemical cooling, additional octane from the meths contribution.

up to 30% meth wont ignite from a flame, any higher and it does.. and burns with an almost colourless flame.

[stevieturbo]

If the alcohol is worrying you reduce its percentage? It has very little effect as an anti detonant when used with water - 100% water is proven better for anti-det properties and cooling. Plus its corrosive effect on aluminium is a PITA - piece of that trying to squeeze through the nozzle will really cramp your day LOL
Fuel cut is the easier on an engine - lean out doesn't occur! If the tap is off, nothing flows out - no fuel = no burn = no lean condition!

Ive been using water/meth on engines for about 20 years, never has corrosion of any kind been a problem.
Any corrosive effect of methanol on aluminium is very overstated.