zelement

I recently installed the snow performance meth injection kit and is tuning with Accel's DFI gen VII. I don't have the wideband option so I don't know if spraying the meth. is causing a richer mixture, but it sure feels like it. everytime I spray meth compared without meth, it feels like the motor is loading up on fuel and the exhaust backfires and burps.
I am running an approx. 50/50 mix with water. I have the dual nozzle setup with the initial spray at 4.5psi and full at 7.5 psi.
Has anyone else experienced this?

TIA,

Paul

7LitreC5

Yes it will because methanol is a fuel.

QuickSilver2002

Yes, you are obviously going to run richer, but the fact that you are mixing in H2o complicates the equation.

The H20 will make the mixture less prone to ignition (which can be good for preventing detonation under high cylinder pressure) but it is easy to get too much and cause the ignition to not even take place. The H20 will also reduce the resultant BTUs of the combustion, so you have to run more boost and/or more aggressive timing or a leaner AF ratio to make up for the loss of heat/power in the chamber. I have found that a water/alky mix is fairly tricky to tune. I small spray is pretty simple, but you won't see big gains with it.

I would recommend running the car with pure meth. This will be much easier to tune and you will see much better results. I have found it to be very forgiving and easy to make decent power with.

Also, a big spray/dual nozzel alky system usually requires you to dial back your injectors quite a bit to maintain typical WOT AF ratios.

zelement

Very good advice!
I have not pure meth but I guess I will give it a shot.

What do you mean by dialing my injectors back? Do you mean dial the injectors back with the DFI? I will try to add a little more timing to see if this helps.

thanks, '

Paul

gtsbob

zelement
I have a Snow system on my GTS but the tuning procedure is the same. You really need a wide band to get the full benefit of the injection because the A/F needs to be tuned as close to 12.5 as possible, retarding the timing as needed. When the injection is operating the A/F will be richer by about a point or so. You can then start advancing the timing for more power. This is the prcedure I used and picked up about 60 rwhp and no ping. Before I was pulling out 11 deg and now my timing is close to stock.
I hope this helps

QuickSilver2002

Yea, you will most likely need to reduce the injector pulse widths with DFI.

And like the above post mentioned, you really need to get a WB on the car. THere are reasonably priced stand alone units that do logging available from several vendors these days.

It is best to get the AF in line before you start to play with the timing.

You could also put the car on a dyno and use their WB.

STAGED

Yup. Methanol is a hydrocarbon that does burn with the rest of the mixture.

gtsbob: The % quantity of extra HC via methanol may however be extremely small compared to the HC via gasoline injected. This can actually be verified with wideband O2s with and without spray. Does a "point" in your post indicate 0.1 or a full 1.0?

gtsbob

Staged
I got my A/F to about 12.3 without the injection and with the system on and advanced timing. I'm reading around 11.5 although some of the perceived richness is due to the way the methenol is read by the wideband sensor. By the way, I'm using a 50% water/meth mix and 91 octane. My injection mixture is about 18% of the total fuel. With 10 lb boost I start spraying at 3 psi and max at 8 psi.

QuickSilver2002

WB should be an accurate index with methenol being sprayed. The actual phisical ratio reading becomes inaccurate with meth, but the index should still be valid. In other words, 12.0 or a bit below is still a good target even though you are physically putting a richer mixture into the motor.

zelement

All good info. Thanks. i really need to get a WB.

what WB are you running?

zelement

the only problem with this is that i have my meth injection on a switch, i don't run it all the time. By reducing the pulse width on the injector without the meth would produce a leaner mixture right?

QuickSilver2002

Yep, you are usually dependant on it once you go to a big spray and you tune your rail based fuel against it. You will only be reducing pulse widths at points where the alky is supplementing enough to bring the AF down too much.

Most people run it all the time. Meaning that the system is always activated but only spraying under a decent amount of boost.

qwiketz

I've gotten tons of info in the last 3 weeks off turbobuick.com in the alky forum. Essentially, what i learned is that most of their guys run straight meth. They also said that a 50/50 mix richens up the mixture approx 1/2 a point on the wideband and a 100% mix richens it up approx 1 full point. Of course, the a/f ratio will vary with quantity injected.