air fuel ratios and meth

deadbeatrec · Jan 3, 2008, 12:23 PM

what should the air fuels look like at WOT throughout the powerband. i think i was around 11.8:1 near redline with 100% meth,25psi, 93 octane using the .08mm nozzle aquamist system.

i was just wondering so i have a referance. thanks

KevinD · Jan 3, 2008, 12:26 PM

i target 12.5:1 to 12:1... although my car is running at like 11:1 right now... it just needs to be tuned again

oh and going from 11:1 to 12:1 afr makes a huge difference in power.

DeiPro · Jan 3, 2008, 12:28 PM

Quote:

Originally Posted by KevinD

oh and going from 11:1 to 12:1 afr makes a huge difference in power.

Only if your fuel is knock limited.

deadbeatrec · Jan 3, 2008, 01:06 PM

Quote:

Originally Posted by KevinD

i target 12.5:1 to 12:1... although my car is running at like 11:1 right now... it just needs to be tuned again

oh and going from 11:1 to 12:1 afr makes a huge difference in power.

ok good cuz i was scared when it was holding 12:1 but then realized that it was a higher octane and would most likely act like race fuel and a higher air fuel ratio would likely be needed. thanks

steadly2004 · Jan 3, 2008, 01:49 PM

So, if normally you tune for 11.5-12.0 for non-meth conditions.

Then with when meth sprays you should lean it up a bit, 12.0-12.5? Or just advance the timing and keep the same a/f?

Labonte MotorSports · Jan 4, 2008, 09:10 PM

50/50 mix in the right volume will lower A/F 1/2 point. 100% meth will lower a little over 1point. A 50/50 mix is about 113 effective octane when used with a 91 octane base fuel.

With a normal A/F of 11.5, you enable the meth and should see the A/F drop. Now you can do one of the following: remove fueling, add timing or increase boost. Any of the three will then lean out the A/F. A good target A/F with meth on an Evo is 12.2-12.4, if you are running a fail safe like our IFS-10, or other. If you don't have a fail safe, do not lean it out more then 12.0 with 50/50 or 11.5 with 100%.

Best regards,

Dan

Ph3n1x · Jan 4, 2008, 09:26 PM

Lean Spool Enabled Will effectively limit how well you can tune 4th Gear.
You'll push 3rd gear to 12.5AFR but only be able to get 11.7 in 4th.

Disabling Leanspool will allow for 12.0-12.2AFR in ALL gears.

steadly2004 · Jan 4, 2008, 09:39 PM

Quote:

Originally Posted by Labonte MotorSports

50/50 mix in the right volume will lower A/F 1/2 point. 100% meth will lower a little over 1point. A 50/50 mix is about 113 effective octane when used with a 91 octane base fuel.

With a normal A/F of 11.5, you enable the meth and should see the A/F drop. Now you can do one of the following: remove fueling, add timing or increase boost. Any of the three will then lean out the A/F. A good target A/F with meth on an Evo is 12.2-12.4, if you are running a fail safe like our IFS-10, or other. If you don't have a fail safe, do not lean it out more then 12.0 with 50/50 or 11.5 with 100%.

Best regards,

Dan

I actually bought your failsafe/wastegate solenoid this week. It should be here soon. SO, I will probably just tune up to 10-11psi without meth, which is wastegate pressure on my Tial. Then turn up the boost and tune with the meth past that. And I'll be safe as long as I have the meth while I'm in that condition.

Richard L · Jan 5, 2008, 04:20 AM

Quote:

Originally Posted by deadbeatrec

what should the air fuels look like at WOT throughout the powerband. i think i was around 11.8:1 near redline with 100% meth,25psi, 93 octane using the .08mm nozzle aquamist system.

i was just wondering so i have a referance. thanks

What is the size and DC of your injector at red line? Without these information, I hate to guess the M/F ratio. We know the meths flow but not fuel flow.

dan l · Jan 5, 2008, 05:54 AM

Methanol needs much less oxygen per volume than gasoline for stoichiometric burn.

SlowCar · Jan 5, 2008, 09:18 AM

Quote:

Originally Posted by Labonte MotorSports

50/50 mix in the right volume will lower A/F 1/2 point. 100% meth will lower a little over 1point. A 50/50 mix is about 113 effective octane when used with a 91 octane base fuel.

With a normal A/F of 11.5, you enable the meth and should see the A/F drop. Now you can do one of the following: remove fueling, add timing or increase boost. Any of the three will then lean out the A/F. A good target A/F with meth on an Evo is 12.2-12.4, if you are running a fail safe like our IFS-10, or other. If you don't have a fail safe, do not lean it out more then 12.0 with 50/50 or 11.5 with 100%.

Best regards,

Dan

Guz Man · Jan 9, 2008, 06:42 AM

good info..

dudical26 · Jan 9, 2008, 02:46 PM

Just to be clear on all these comparisons, are all these measurements taken with a wideband calibrated for normal gas - (IE 14.7 to 1)

Keep in mind spraying meth will not only change your AFR but it will actually effect the readings of the Wideband. The lambda will still be accurate but the AFR won't be.

However, as long as everyone is using a wideband calibrated for Meth we are still ok to make comparisons.

steadly2004 · Jan 9, 2008, 04:03 PM

Quote:

Originally Posted by dudical26

Just to be clear on all these comparisons, are all these measurements taken with a wideband calibrated for normal gas - (IE 14.7 to 1)

Keep in mind spraying meth will not only change your AFR but it will actually effect the readings of the Wideband. The lambda will still be accurate but the AFR won't be.

However, as long as everyone is using a wideband calibrated for Meth we are still ok to make comparisons.

I didn't even think to ask this question. I just assumed that everyone was talking about a wideband calibrated for normal gasoline operation, and not altered for other fuels.

crcain · Jan 10, 2008, 07:50 AM

My friend and I have been having this discussion lately as he has had his meth kit installed for a while but we have been lazy about running it and tuning it. Maybe some of you can help our understanding?

Stoich of gasoline is 14.7:1. Generally in my tuning I run 11.5 - 12.0 once making a decent amount of boost, I do this only because my tuner told me to

I suspect the reason you don't run stoich at full boost is because it would burn too hot and eventually cause knock. Running the richer mixture I assume keeps things calmed down and cooler thus allowing for the boost, reasonable ignition advance, etc.

Stoich of alcohol is 6.5:1. Now, let us say I was running alcohol/methanol only. I have no idea what my target AFR would be at full boost. 2.7 points lower like for gasoline? (14.7 - 12.00) I doubt it, but I have no idea really.

Now lambda, shows me how far from stoich I am regardless of fuel. So let's say my 12.0 AFR is .81 lambda. Now if I run .81 lambda just running methanol only, that gives me a 5.2:1 AFR running methanol. So if I assume for methanol the ideal AFR on boost is the same lambda as gasoline, then 5.2 AFR is what I want.

So on the face of it, it seems if I just switch to lamda, and keep lambda at .81 I will be fine. However, when you are view gasoline AFR, it is directly proportional to lambda. So it seems to me I don't even have to switch to lambda. I simply make sure to keep the AFR at that original 12:1 value I was with just straight gasoline.

My question then is, can anyone see anything wrong with the following steps?

1. Tune car for gasoline only. Target 12:1 AFR. (or whatever your target AFR is for gasoline)
2. Start to spray meth progressively as IDC rise. AFR should drop (go rich) as you are adding fuel. Let's say it is now 11:1 AFR.
3. Lean the gasoline micture out until you are back at 12:1.
4. Since 12:1 AFR always equals the same lambda when our wideband is set for gasoline, we have with the above steps achieved keeping the lambda the same.

More questions though....

a) Is the assumption that lambda at full boost for gasoline should be similar to lambda on methanol correct?

b) Without a dyno, doing road tuning, how do you know ultimately how much meth to spray? What jets to use and how much openings of the solenoid.