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 LM-2 newbe Methanol ` 
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Joined: Sun Nov 16, 2014 10:57 am
Posts: 8
Hello, in an effort to learn a little and help or race car, we just bought a Lm-2 from Innovate Motorsports and am trying to learn how to use this to help tune our slower bracket drag car.
It's a very mild 350 Chevy w/ Alcohol carb - sensor is in the exhaust pipe about 8" behind the collector.

I just used the gauge for the first time this this weekend and we are having trouble getting the gauge to record. I have it reading RPM from my digital 6AL2 with a inline 100 potentiometer from R shack, but it seems we maybe missing something in the set up, in the recording, or the SD card, so I can't post a graph yet, but in a pinch we used a old cell phone to record the face of the gauge this week.

I have tuned this junk by ET slip and my old scholl abilities until now - now that I bought a AFR gauge I'm having a hard time understanding what I'm seeing. I believe we have our gauge reading the stoichrometric valves and this is what I'm seeing:

4.3 Idling at 1200 Rpm
4.8 to 4.9 staged up in Rpm at the line (footbraked @ 2000 Rpm)
Drop slightly after the launch for only one reading to 4.7 then recovers- (maybe a little too large of squirters)
5.1 to 5.3 most of the way through low gear (6500 Rpm shift)
drops slightly to 4.9 to 5.2 just after shift into high (2 speed Powerglide drops approx 5300 Rpm)
holds pretty steady at about 5.5 through most of the run in high gear
drops slightly near the finish line to 5.3 or 5.4 (about 6850 to 6900 Rpm)

From what I can understand it looks like we are a little rich the whole way through the run - do you agree?

This info was from a recent Track rental test we took part of where we made several passes where most of the passes we got info from were very similar. The next day we made 10 passes with a 1/4 mile ET between 12.025 and a 12.046 and one bad pass of 12.055 (<-with a slow 60' time) in race conditions, so I think we are not too far off - but typically the car varies a little more than that on a day. Which is why I bought the gauge, - to help make our packages a little tighter.

Can you novice Alcohol tuners offer and suggestions that may help a new-be Lm-2 user?

Thanks for any help you can give.

Sun Aug 21, 2016 1:00 pm
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Joined: Fri Feb 08, 2013 5:50 pm
Posts: 2363
It requires a specific SD car to work. It can't be an SDHC card, just a standard SD card, and I think limited to 2 gig. If you can't find one I have a few I found. And set the LM2 to read Lambda, then it won't matter what fuel you use.

Sun Aug 21, 2016 3:12 pm

Joined: Sun Nov 16, 2014 10:57 am
Posts: 8
Thanks for the responds
Yes I purchased 2 2G non HD Sd cards at my Walmart, and I tried reformatting them with the FAT32 but it keeps telling me they are locked, the little tab on the card is not locked. Maybe 2 bad cards?
Yes I'm finding out most use the Lambda, I don't have a clue how accurate it is but the Wallace calculator crosses over:
a 4.7S to a .73 Lambda
and a 5.5S is .86 Lambda

so does that sound to rich to you all?

Sun Aug 21, 2016 3:55 pm

Joined: Thu May 08, 2014 7:47 pm
Posts: 235
I use gasoline air fuel ratio on everything, or lambda.

air-fuel-ratios.jpg [ 124.71 KiB | Viewed 308 times ]
Sun Aug 21, 2016 10:13 pm
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Joined: Fri Feb 08, 2013 5:50 pm
Posts: 2363
I just reworked a methanol Dominator, and it was around .95 at idle. Yours needs a little help, you need to measure the idle feed restrictions and idle air bleeds, also see where they are located. Top, bottom, or divorced idle on the main jet side of the blocks.

Mon Aug 22, 2016 9:58 am
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Joined: Fri Feb 08, 2013 2:37 pm
Posts: 1744
The chart above with the A/F to Lambda conversion has the remark "Best Power" on the line with .85 Lambda = 12.5/1 A/F Gasoline = 5.46/1 Methanol. "Best Power" at those values only actually applies to gasoline. The other fuels have significantly different characteristics because they all have Oxygen in the fuel molecule.. Nitro-methane, for example, because it has two Oxygen atoms in the molecule, is a mono-propellant and does not require any air at all to burn, it makes more power when more is burned, and makes "Best Power" when most is burned, sort of like Nitrous, more in = more out, power, chunks of engine, mist of piston, slag, etc.

In other words, because the Alcohols contain Oxygen the A/F which gives best power is richer than gasoline.

Another factor is the combustion rate, burning speed, is not the same as gasoline so spark advance requirement is different. Check the chart in this link. viewtopic.php?f=23&t=1047 Extremely rich (compared to gas) Methanol mixtures require less advance.

Another very significant effect of Methanol is the compression stroke requires less work because the large heat absorption in Methanol's evaporation results in lower pressure, and less work inside the engine = more work (power) out.

Mon Aug 22, 2016 1:31 pm

Joined: Thu May 08, 2014 7:47 pm
Posts: 235
I agree they all have different burn characteristics that require different timing requirements. Octane, chamber design, quench area, spark plug, valve angle, timing, ignition system used, ect. all have effects on the flame front, not just the fuel and its level of oxidization characteristics.

In my experience with all of the fuels above, the motor doesn't know what fuel is in the hole, because motor's are stupid like that. And motor's only complain when something is wrong. Usually an issue with timing, fuel charge, oil in the hole, pre ignition, detonation, ect. Other then that....they do not complain much. The motor doesn't know the specific gravity of the fuel being burned, it just knows the air to fuel ratio it likes to burn, regardless of the fuel used.

The sensor is looking for residual oxygen content left over after the burn. it does not care if its nitrous or nitromethane, methanol, ethanol, it's just looking for an oxygen content. A ratio that is around 12 parts air to one part fuel, or 0.82 lambda is just that, regardless of the fuel used, stoich is 1.0

Much like air to fuel ratio's for various fuel's, lambda is just another number for reference. you are 12.0 or not. 0.82 or not. any thing below is going to be rich, anything above is going to be lean. The motor will tell you what it likes best, you have to figure it out, listen to it, and give it what it wants, and that is an air to fuel ratio it can handle and, burn efficiently.

Tue Aug 23, 2016 12:14 am
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