[Putter]

To those of you running fuel cut rev limiters instead of spark cut, is there any problems when the injectors are shut off and the alcohol still running?

I would think it would be so little alcohol that it would just be so lean that it wouldn't even fire, which would be fine for a cooling effect in the chamber, but I'm somewhat worried about there being enough fuel to start around 50 lean combustion cycles in a row, a few in a row doesn't hurt anything, but I don't know where the threashold of damage is. I'm in the rev limiter in the first three gears of my car, so I spend quite a bit of time with the injectors cut.

I would assume most of the GTP people use fuel cut and I havn't heard of any problems, but I want to make sure.

I'm running the M15 nozzle on a 4cyl thats around 230-250whp as a best guess.. and am at 20psi with the alcohol not turned on yet.

[dvldoc]

That nozzle is way, way to big for a 4cyl making that power level. You car will bog like crazy with that nozzle on there. You need a M5 or M3 nozzle. A stage 1 SRT runs a M3 a STI a M7 cars like GTO's and vetts and large v6 turbo apps like grand nationals run M15 nozzles.

[Putter]

When I ordered the kit and I said I had plans to go for 300whp you said the 15 would be great, so I got a 5 and a 15. When funds come around I'm a turbo swap from 300-350whp, and I will be doing this.

The 15nozzle is supposed to be 15 pounds/hour correct? What pressure is that flow rated at?

I'm going to 25+psi when my controller comes back and am going to run it on 92 gas... Plus I'm running a standalone so I can tune around it if need be.

Just curious about the rev limiter, as an 15 nozzle is quite a bit of fuel.

"If your wanting that much HP you definatley need a M15. The pump will go to almost 200psi in case you didn't know. The single M15 at 200psi will take car of 400+ hp."

Thats from you in my saved messages on 6-10-05. Its not a big deal if I have to change nozzles, I'm not worried about that, just more concerned with the fuel cut rev limtier. This may be one of those things where its just try it and see more or less.

[dvldoc]

Don't know if you gave me all the specifics of your engine size at the time, But at 350hp and 25psi with a 4cyl that much flow is not needed. In a V6 running that much yes but not a 4cyl. I M10 would probably be your max. The numbers are GPH. The M5 nozzle on our kit flows at about 140psi the M10 around 125 to 130psi. Nozzle size is the only really big factor that give you a certian output psi.

Nozzle size is not just about hp and boost engine size plans a role in it also.

[datsun280zxt]

not to get in the middle of things here, but it takes "X" amount of fuel to make "X" amount of HP. My buddy has your kit on his turbo spirit with a m14 and a m5. It works great. Infact it could probably use even more methanol! Just cut the fuel back on the standalone to keep your air fuel ratio correct. This is all assuming your running straight methanol. If you're running a mix, then you may want to back it off a little, but just turn the pump pressure down on that m15 and you'll be fine.

[dvldoc]

We don't recommend you ever pull more than 25% of your fuel to replace it with methanol If you have a system failure then pop goes the piston, You should only run methanol injection to the point that your vehicle can survive with what ever knock it is getting with out the system.

[datsun280zxt]

Originally Posted by dvldoc @ Sat Jul 08, 2006 1:03 am

We don't recommend you ever pull more than 25% of your fuel to replace it with methanol If you have a system failure then pop goes the piston, You should only run methanol injection to the point that your vehicle can survive with what ever knock it is getting with out the system.

Not trying to argue with you, and I understand your position as a company...you have to take a "safe" position to avoid lawsuits from idiots that don't know what they're doing and want to blame it on you. The thing is...if you're spraying 25% of your fuel using methanol, thats way more than enough to make the car go lean, and instantly detonate if the system doesn't work. Heck 10% on most cars would blow a head gasket if nothing else. Theres a good chance of other serious failure as well. Thats why a car is tuned to a specific a/f ratio. Anyways...just my 2 cents.

[Putter]

Thats why I'm using alcohol, to go past where my engine can safely take some detonation. It knocks around 22psi with 18* of ignition timing as the humitiy goes up, and pulling more timing doesn't fix it so its a fuel concern, so in order to go past that I'll be using the alcohol. I think if you pulled as much as 25% of your fuel mass you would be nuts... I am going to run as must boost as my current turbo will alow even even on 92 gas.....could be as high as 27psi with the turbo way off the map (not efficient, but still makes power). Go big or don't go at all...

But as the ad says, more boost more timing.....


Anyhow, I'm excited to get the controller back and get a clutch in the car and go play... (Clutch failed at the drag strip going into 3rd gear)

I still haven't recieved an answer on methonal/water fueling while the injectors are disabled durning a rev limiter event and whether it may cause damage or not.

[datsun280zxt]

no...you don't want it spraying. If it sprays and your cutting all your other fuel, the car will go severely lean and disaster will occur. Hook it up to a clutch switch or something so it doesn't spray while your bouncing against the 2-step. As far as hitting the rev limiter during a race, you should be okay, but it's not a good thing. The methanol will ignite and cause a lean condition as well. I suggest you work on keeping it out of the rev limiter, or find a way to raise the limiter to a point you're not bouncing off of it all the time. When you light up the tires, I know its real easy to hit the limiter, but fuel cut limiters are bad news anyways. There is usually a little fuel that gets sprayed and can causee lean conditions as well. A spark cut rev limiter is a much better system on turbo car. Hopw I helped...

[Putter]

I'm running a distributerless ignition so a spark cut rev limiter is kind of out of the question(both cost and simplicity, I've already wired the car from scratch I'm not doing it again). My fuel cut is setup to drop at least 250rpms before turning the fuel back on, so there's a lot of nice cold air pumped through the engine, so the partial blast of gas shouldn't be an issue, they do this on supercharged mustangs from the factory.... But... They don't keep spraying alcohol on supercharged Mustang's...

Using straight water or a little heavier towards the water side should negate any fueling that may come from the injection and shouldn't really affect the rev limiter or the base fueling tables. Maybe this would be the best way to try.?