14.7 on WOT or something lower like 12.5?

[Finaltheorem47]

Engines run best at 14.7:1 - whether it is under boost or not.

In the past, lower AF ratios under boost used excessive fuel as a detonation control - the additional fuel acts in the same way that water spray does - it cools the incoming charge.

It's a band-aid fix, in my opinion, to run excessively rich. Detonation control starts with the engines cooling system - to the way it was built - cam specs - etc etc etc.

Gonna have to get back to a meth/water spray here again (me = broken record). It will work for you.

Guy is on my Jeep forum. He makes a lot of sense and has been very successful with his turbo projects. I know hes injecting a 7:1 ratio of meth/water to his fuel at WOT under boost also.

So I was wondering, do you guys agree with him? I see most guys get tunes for around 12.5:1 at wot.

 

[tommygun]

NEVER 14.7:1 under boost unless you want to destroy your engine

cruising down the hwy is fine but once you tip in it needs to lower into the 12.5 range, even with meth injection.

 

[Finaltheorem47]

NEVER 14.7:1 under boost unless you want to destroy your engine

cruising down the hwy is fine but once you tip in it needs to lower into the 12.5 range, even with meth injection.

Why?

 

[unit213]

The guy is a moron, plain and simple.

 

[Ls1z28-00]

Why?

12.5 is lean even, i would want below 12....... N/A cars can get away with 13 and up, but boosted cars have to be lower or else the lack of fuel will cause your cylinders to overheat and cause damage.

 

[Mystic03]

the guy is a moron, plain and simple.

+1 lol

 

[Finaltheorem47]

The guy is a moron, plain and simple.

This comment is pointless.

12.5 is lean even, i would want below 12....... N/A cars can get away with 13 and up, but boosted cars have to be lower or else the lack of fuel will cause your cylinders to overheat and cause damage.

He says that with his water/meth injection though, he doesn't have to run it rich and worry about over heating because the water/meth does the job of the extra fuel for him. So still he makes sense, give me a more detailed reason! lol, sorry just want to know the theory.

+1 lol

Also pointless, instead of just "knowing" that he is wrong and that it must be richer, I'd like to know why, because he makes a point and I'd like to know what makes him wrong.

 

[unit213]

This comment is pointless.




He says that with his water/meth injection though, he doesn't have to run it rich and worry about over heating because the water/meth does the job of the extra fuel for him. So still he makes sense, give me a more detailed reason! lol, sorry just want to know the theory.




Also pointless, instead of just "knowing" that he is wrong and that it must be richer, I'd like to know why, because he makes a point and I'd like to know what makes him wrong.

I think you should tune your car to 14:7:1 A/F and boost the shit out of it...then report back to us with your results...even on meth. You'll then understand that we "know" what we're talking about based upon real
world experience.

Here's an idea, maybe do a little of your own research (google perhaps?)
as opposed to waiting for someone to spoon feed you the answer...instead of getting pissy when you get replies that you don't like.

 

[Finaltheorem47]

I think you should tune your car to 14:7:1 A/F and boost the shit out of it...then report back to us with your results...even on meth. You'll then understand that we "know" what we're talking about based upon real
world experience.

Smart...

To quote Socrates, "Question Everything." You appear to of just accepted that one must tune the engine with a richer A/F ratio on WOT, without caring about why. Unlike you, I would like to understand why, the physics behind it. It's cool though, there's no law or anything where you must know this stuff, but your attacking me for wanting to know why, when I wont accept a simple "because I said so" answer.

Knowledge is power.

Right now, I believe the reason to increase the A/F is to cool the EGTs (EGTs defined in this instance as a way to meter the cylinder temps) . One of the operations injecting water/methanol into the engine does, is to reduce the EGTs.

Here's an idea, maybe do a little of your own research (google perhaps?)

I have and I people say (besides the meth thing) the only other reason is because the A/F is average, meaning one cylinder is at 14:1 while another might be at 10:1. But with our MPI system, that seems unlikely to occur. (http://www.honda-tech.com/showpost.php?p=38248778&postcount=2)

The EGT's can be used to determine the correct A/F/S. The richer A/F ratio helps cool the cylinder reducing the EGTs. If you run a leaner temperature, the EGT's will climb and you can have problems. (well, that still doesn't answer my question, won't the meth serve the same purpose that the extra fuel does?) (http://forums.vwvortex.com/zerothread?id=3468129&uid=304020&dir=1&postid=42145294#42145294)


From my understanding, the Water/Meth works two ways. First the water and meth help cool the air by absorbing the heat. The other benefit is the methanol is a fuel and will combust, so basically your adding another fuel injector to intake manifold in a sense, which in effect, richens the a/f ratio.

 

[TRBO VNM]

Just above you contradicted yourself. First you say raising a/f to cool egt and then the opposite after that later in your post. Fuel cools it down. Yes water/meth will help cooling and allow you to run a little leaner so for the most he is right. However IMO I would rather run a richer a/f and not risk adding something else to the setup that can fail and cause major damage. Now with that said I don't disagree with using water/meth with a race tune and using a quality kit. I probably will myself but not on a full time basis

 

[milenko1247]

I have a s/c setup with meth and i was runnin around 11.5.... Just look at my avatar pic... Thats what happened after about 14 hard pulls.. tic tic ... booom

 

[tommygun]

only if its direct injection will this work

its nearly impossible to control detonation at 14.7 AFR so the general rule of thumb for most tuners is to get near 13.1 NA and 12.1 boosted for the simple fact that running more will cause more heat inturn causing detonation to become more prevalent. You can tune a car to 14.7 in a perfect condition atmosphere but it will melt parts in the process, even with meth/water injection. A direct injection car runs leaner since its fuel control is more stable then a basic rail/injector set up, but they still rarely run 14.7 under full throttle since gasoline is unstable at the temperature it reaches in this process

 

[Finaltheorem47]

Thanks, makes more sense now.