Alky and how it affects o2 numbers

[joed]

So if I'm shooting for ~760 O2's at the top, I crank up the methanol and keep lowering the FP to achieve desired top end O2 range...my 1st and 2nd gear O2's are ~840-860 range...how is that addressed? My 1/8th's are pretty slow. ~8.1-8.2@88-89mph. Is that where more timing in the lower gears comes in?

 

[Razor]

Dropping fuel pressure affects your drivability, spool up, etc..

The correct way is to lower the injector pulse width in the chip so it commands less fuel, not affect your drivability. Thus letting the alcohol do its job.. as well as the chip.

On a fixed point(SMC/DIY) style kit.. non-progressive.. a slick chip tuner can tailor the chips fueling against the expected turnon point. Take out a lot more down low and gradually increase it back in. to minimize the hit when the system fires.

On a progressive, take it out flat across the board.

If the chip is like a street 93 for 18-20 PSI and you run alcohol at 23 PSI.. that seems to work, as well as minor fuel pressure changes to lean it out.

Hope it makes a little sense.

 

[joed]

Razor, Yes the progressive system is the way to go Just not at this time as I've already got the SMC. When it's time to upgrade, progressive makes perfect sense. I'm so glad alky is catching on, I was considered "nuts" when I got my kit about 5 years ago!

Anyhow, I'm tuning now with my TT chip which I'm sure will offer advantages in the fueling, and hopefully my 1/8th times over my old JC93 chip. I can lower the FP slightly or get Eric to adjust when I get it tuned, if I'm still getting slow 1/8th and high O2's.

How do you feel about AC r44 (stock) heat range plugs to help spool? I've heard that with methanol, you may not need the detonation protection of the colder plug (42-43 range)
Thanks!

 

[TurboTR]

Hmm. To burn fuel in the exhaust would require either alot of fuel that burns really slowly, like nitromethane top fuel apps or there needs to still be enough oxygen hanging around in the charge to continue burning it. If one sprays too much fuel, by definition there is not nearly enough oxygen around to burn it all to begin with. Alcohol doesn't burn by itself, even if there is one O molecule in place of a C molecule on the hydrocarbon chain Kindof hard to imagine it burning comfy all the way through the power stroke and out into the exh pipes when there is not even enough air to burn everything in the chamber to begin with... The cars that I have seen with alcy inj have all layed down noticeably when too much alcy comes in too soon. Exactly like double pumper cars do when the 2nd pump comes on too soon and the a/f goes way rich of already rich. Often still not rich enough to misfire yet (darn close but rich enough to kill the power noticeably...

Stoich for methanol is like 9:1, ethanol is like 6:1 if I recall. On one hand that sounds great, since you can then burn alot more fuel for a given size gulp of air. Of course the downside is that alcohol releases about half the heat that gasoline does when it burns, so the end result is about equal after all is said and done. It does have some great advantages in knock suppression though vs pump gas as we all know, and of course the charge cooling effect. But otoh once it has vaporized, now it's taking up space that could have been occupied by air... Hmm...

It was my experience when I 1st started playing with N2O that I could hardly feel a 50 shot on about 650 rwhp... I'm wondering how much snap a 15 shot actually has If we want to pick up the power with nitrous, we have to burn more fuel somehow. If one is really rich to begin with, I guess we can imagine how adding "air" (nitrous) would allow more of that excess fuel to be burned, rather than just heated and passed out the exhaust as HC emissions (lol) and thus pick up the power some, even without spraying extra fuel.

Just thinking out loud Interesting topic!

TurboTR

 

[4sfed4]

Originally posted by TurboTR

It was my experience when I 1st started playing with N2O that I could hardly feel a 50 shot on about 650 rwhp... I'm wondering how much snap a 15 shot actually has If we want to pick up the power with nitrous, we have to burn more fuel somehow. If one is really rich to begin with, I guess we can imagine how adding "air" (nitrous) would allow more of that excess fuel to be burned, rather than just heated and passed out the exhaust as HC emissions (lol) and thus pick up the power some, even without spraying extra fuel.

15 hp at 2000 rpm = 40 ft lb and I can feel that seat of the pants. Its probably actually more than 40 ft lb as the boost picks up about 2 psi as well at a given rpm (down low below the full boost threshold).

But, you are right in that when you are at peak power, the 15 shot wouldnt even be noticable. I havent run the nitrous up top yet though as its on a boost switch.

But, I do have all the jets from 15 to 75 hp (as well as a fuel solenoid and wet Fogger nozzle), so I might be trying that soon Ooops...I mean my friend might be trying that soon.

 

[4sfed4]

Originally posted by TurboTR
Hmm. To burn fuel in the exhaust would require either alot of fuel that burns really slowly, like nitromethane top fuel apps or there needs to still be enough oxygen hanging around in the charge to continue burning it. If one sprays too much fuel, by definition there is not nearly enough oxygen around to burn it all to begin with. Alcohol doesn't burn by itself, even if there is one O molecule in place of a C molecule on the hydrocarbon chain Kindof hard to imagine it burning comfy all the way through the power stroke and out into the exh pipes when there is not even enough air to burn everything in the chamber to begin with... The cars that I have seen with alcy inj have all layed down noticeably when too much alcy comes in too soon. Exactly like double pumper cars do when the 2nd pump comes on too soon and the a/f goes way rich of already rich. Often still not rich enough to misfire yet (darn close but rich enough to kill the power noticeably...

Perplexes me too.....

Let me see if I can grab the datalog screen shot and post it here. On my car (without any methanol spraying), I dropped the base fuel pressure 12 psi to lean the car out. I figured thid would spool the turbo a little quicker. It actually spooled slower. Then, when I bumped base fuel pressure back up to where I started and then seemingly oversprayed the methanol, the turbo spooled much faster. I felt it seat of the pants (but I thought I was just getting tricked). So, I then datalogged it......and sure enough the boost comes on sooner when I sprayed the methanol. The methanol boost curve line and the 15 shot nitrous boost curve lines were laying on top of each other.

 

[TurboTR]

Hmm, maybe you're increasing the torque of the engine, which is what you feel, which would also make more exh energy, which would... etc

TurboTR

 

[4sfed4]

Originally posted by TurboTR
Hmm, maybe you're increasing the torque of the engine, which is what you feel, which would also make more exh energy, which would... etc

TurboTR

Yes...but why is the torque increasing with all the extra fuel....thats the question. I really dont know why as I am 1000% sure the car is running pig rich on spool up. It pegged the wideband on the dyno! But, taking fuel out doesnt seem to make the turbo spool faster.

 

[4sfed4]

Originally posted by d0n_3d
When you are spraying straight 100% denatured alcohol...how does it exactly affect the o2 numbers on the top end?

Ive been doing some serious digging on this issue as its bothered me for some time.

The bottom line is---

The lambda value will be the same for ANY given fuel at stoichiometric (i.e. lambda=1). The voltage out of a wideband sensor is also going to depend on lambda as well. Thus, lambda is independent of the fuel being used.

However, when there is a mix of fuels, although the lambda will stay the same, the actual A/F as reported on a typical wideband will be "off" as the wideband is merely reading a voltage (i.e. determining lambda) then assigning a given A/F number to it based on what the sensor "thinks" the engine is using for fuel.

So, if one takes a car that is running methanol to a dyno with a wideband sensor, makes a run, then checks to see what the A/F was, they might get incorrect information. Lets say the sensor read (just to make the numbers easy) 2.5V, you would have lambda = 1.0 (or perfectly stoichiometric). Now, the software is going to say that the A/F ratio was 14.7:1 right? But, in reality, the true A/F was not 14.7:1. The true A/F was something between the A/F for methanol at that sensor output voltage (about 6.4:1) and that of gasoline (the 14.7:1).

 

[joed]

so then if you know your proportion of meth to gasoline at WOT and their stoic air ratios, you SHOULD be able to calculate a theoretical target voltage for your wideband....right?

However as with all theory, we'd need to compare this with reality..these cars need somebody to love and caress them and feed them what they want via trail and error tuning. Is there any substitute?

 

[4sfed4]

Originally posted by joed
so then if you know your proportion of meth to gasoline at WOT and their stoic air ratios, you SHOULD be able to calculate a theoretical target voltage for your wideband....right?

However as with all theory, we'd need to compare this with reality..these cars need somebody to love and caress them and feed them what they want via trail and error tuning. Is there any substitute?

I believe the target sensor voltage would remain the same either way (assuming one was tuning for a given lambda).

If one wants to run lambda=0.85, for instance, the wideband sensor output would be about 2.1V regardless of fuel used. If pure gasoline was being burned, this would equate to about 12.6:1 A/F. If pure methanol was being burned, it would equate to about 5.5:1 A/F. Both of these values (I believe) are almost spot on the theoretically ideal A/Fs for power with both fuels (I think)?

The question is.......when one is mixing fuels such as with gasoline and methanol injection, how do you tune with a wideband on the dyno? The A/F the dyno will spit out seems almost useless? I wonder of the dyno software will allow A/F to be presented in lambda instead?

 

[4sfed4]

Originally posted by 4sfed4

The question is.......when one is mixing fuels such as with gasoline and methanol injection, how do you tune with a wideband on the dyno? The A/F the dyno will spit out seems almost useless? I wonder of the dyno software will allow A/F to be presented in lambda instead?

Been thinking about this some more.......Just thinking out loud here!

As a test case.....what will the wideband read and report as "A/F" when you spray 20% methanol and 80% gasoline in the engine?

I think it will report that you are running leaner than you really are.

I think it will do this because the dyno thinks 14.7:1 is stoich. But, for a methanol/gasoline mix it isnt. Stoich is something numerically lower (since stoich for methanol is 6.4:1 and gasoline is 14.7:1). So, for a given lambda reading, youll need to average out the percentage gasoline and methanol based on their A/F's at lambda.

So.....

If lamdba for methanol is 6.4 and gasoline is 14.7:1 and the mix ratio is 20/80----

Stoich for that mixture would be 13.04:1.....I think!??!?!?!

When both are at stoich, lambda would be 1 and the O2 sensor would read 2.5V.

But, I believe the wideband reads the O2 voltage and then looks up that voltage on a table and spits out an A/F based on gasoline. So, even though the ACTUAL A/F is 13.04:1 inthe above case, the dyno will spit out 14.7:1 based on the O2 voltage. So, you are reported as being LEANER than the mixture really is.

Think that makes sense????

Now...the next question is....how are narrow band O2 voltages affected? If the narrowband also looks for lambda (I think it does), then O2 volts should still be useful?

 

[joed]

4sfed4
yea, that's what I was tryin to say earlier...but you actually said it, and clearly I thought. So for a 80/20 gas/alky mix, the A/F should theoretically read ~13.04.....now....will it?

 

[SloGN]

Food for thought

hey guys



I have some interesting info about alky. I ran my GN with alky @ the race track with 93 pump gas.

On the first run @ 20 psi of boost my o2 #'s were in the low 740's range. with no knock.

On my second run i added some fuel to the car about 2 psi. and then i turned the alky off. on that run my o2 #'s dropped in the 690's range with some knock.

so if thats the case that alky makes the o2's leaner than what they should be why did i have a drop on o2 milivolts when i run just plain gas.

cause from what you saying is that with the alky on it reads leaner that what it really is. so if that being the case why did my o2's drop after turning the alky off they should have come up? right


there was 50 milivolts diffrent between the 2 run and i added fuel pressure on the second run and turning the alky off.

will post the direct scan files in a bit

 

[Razor]

SloGN , see your talking O2's, they are talking air fuel ratio.

You bet running alcohol raises the O2 dramatically.

Tune for no knock and what makes the car trap speed highest. Easy.

 

[4sfed4]

Originally posted by Razor
SloGN , see your talking O2's, they are talking air fuel ratio.

You bet running alcohol raises the O2 dramatically.

Yes...If while my car is at idle, if I hit the test button on the PAC and spray methanol in there, my O2 voltages go steady into the 0.9X's and stay there while the car just about dies. So, it definitetly raises O2s.

We shall see how the dyno wideband reacts to the methanol in reporting A/F this Saturday.

 

[ijames]

Larry, one of the nice things about the Innovate LM1 wbo2 is that you can set it to display lambda directly instead of afr, and if you choose afr you have to tell it what the stoichiometric ratio is for your fuel. Klaus gave a tuning example on this in their lm1 forum a couple of days ago, answering a question about tuning a nitrous motor.