right now I'm building my B18c1 for my integra, and I have lower compression pistons and the guy from Wiseco told me that if I'm running high boost and I "tap" the rev limiter it will cut fuel, leaning out my engine, causing a catastrophy.. Is this true, because I was planning to keep the rev limiter in case I miss a shift or something I wont screw my valves/head..

Any opinions are appreciated because I can't figure out which way to go in this situation to hopefully protect my motor...

Thanks.
Dominic.

 

theres a redline and a fuel cutoff

Honda engines actually cut the ignition...(as far as i understand from my manual)
while running on 120+ they havef the fuel cutoff, wich cuts the amount of fuel....

i would just get a MSD ignition since u building the motor and place a pill for the rpm u want to redline.. that way it will cut ignition and not fuel, that way it will not caused a lean=detonation condition

 

I hit boost cut on my hondata last night , scarred the **** outta me..but no damage done, it just cuts fuel if you overboost. I think its WAY more dangerous to hit fuel cut on nitrous rather then boost because nitrous burns REALLY hot.. and if you go lean its gonna get even hotter causing **** to happen.. i wouldnt worry about it if i were you

 

slow down, see the little trial user next to my name? I'm still learning.. heh.. I have MSD, but how will this allow the ignition to be cut before the fuel? "Place a pill" what does this mean? This is confusing right now, and Hondata isn't an option for a couple months.

Thanks.

 

I wouldn't sweat it. Reputable engine management companies cut the fuel off when using a boost cut. They no doubt have done their research, and know what they're doing. I too would think it would cause a lean condition and be bad, but if they're doing it, it must not be too bad.

 

The wiseco guy was right, Honda engines cut the fuel off at redline. To set the rev limiter on your msd you use a "pill". Its just a small plug in chip about the size of a fuse that tells the msd where you want to set the spark redline at. Since you cant change the ecu cutoff, just set the msd at a few hundred rpm lower than the ecu's redline. That will allow the spark to shutdown before the fuel does and everything will be safe.

 

excelent information! Thanks..

However, my ECU's getting reprogrammed, so the next question is.. can I leave rev-limit open (ECU), and ONLY use the pill on my MSD? Will this sufice to save my valves in the event of a stupid mistake (mis-shift, etc)???

ALSO, it just dawned on me that the MSD I have is not an ignition, it's a Boost Timing Master... I bought it with the engine, what's it's purpose and will it do the ignition cut also? Thanks.

Dominic

 

in my case my rev limiter is at 9K rpm.. and my shifts don't reach about 8700Krpm.. but even if i'm to hit rev limiter, it doesn't cut fuel completely, just 1 out of 4 cycles.. that and when you're not running any fuel, you won't have combustion so how can you detonate...

either way, stay away from rev limiter/fuel cuttof.. and if you happne to hit it react quicly enough to release throttle

 

there always talk about stay away from it..
but does anyone know someone whose blown there motor from hitting the limiter in a boosted application?????? I dont think ive read about anyone doing that.

 

well logically, it would be more likely to happen in my opinion. am I right? When the turbo spools, ALOT of air, and ALOT of fuel is going into the motor, when your fuel gets cut instantly under heavy load/ heavy boost, you are instantly running REALLY lean.. That's why I;m concerned.. does anyone know what a boost timing master does?

 

Modified by ShowTymers619 at 12:55 AM 5/8/2004

 

Theres no problem w/ fuel cut off for boosted applications. Like vtec.dc2 said, w/o fuel you cant denotate. Its just sucking in air and then pushing it out.

 

exactally, and honda cut fuel not ignition at the rev limiter. if they cut the ingnition then you'd be shooting like 10ft flames due to fuel still pouring into the cyl.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Silverdub &raquo;</TD></TR><TR><TD CLASS="quote">Theres no problem w/ fuel cut off for boosted applications. Like vtec.dc2 said, w/o fuel you cant denotate. Its just sucking in air and then pushing it out. </TD></TR></TABLE>

With a big direct port nitrous setup you might be able to do some damage because the ECU's fuel cut will not cut the fuel coming out of your nitrous nozzles.

 

I have run my Civic at 10psi and have hit the rev limiter for extended periods of time with no problems. It's an autocross only car, and sometimes it just isn't worth shifting close to a turn, so I keep my foot to the floor and let the factory fuel cut rev limiter do it's thing. Over the last 4+ years of boosing this same stock 18 year old motor 10psi, I've hit the rev limiter MANY times, often for 2-3 seconds at a time. Fuel cut is no fuel - it's not lean. I've switched to a standalone this year, and I'm now using an MSD BTM6 with it's ignition cut. The ignition cut sounds a little smoother when you ride it, but either one is ok.

One thing to keep in mind, no rev limiter is going to help if you miss a shift. Fuel cuts or ignition cuts can only limit the motor from continuing to rev under it's own power past a set rpm. If you miss shift into a lower than wanted gear, the transmission will cause the motor to overrev. If you miss shift into neutral and stand on the gas, the inertia of the motor accelerating will carry it far beyond the set point for the fuel or ignition cut. Thats why a lot of rental cars I've driven lately now have a 3-4k rev limit when in neutral, so there's no chance of over reving the motor.

-Chris

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mos &raquo;</TD></TR><TR><TD CLASS="quote">

With a big direct port nitrous setup you might be able to do some damage because the ECU's fuel cut will not cut the fuel coming out of your nitrous nozzles. </TD></TR></TABLE>


I agree with you on that. If you are running a wet nitrous kit then fuel cut will kill your motor quickly. You want ignition cut when running nitrous.