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 Post Posted: Tue Sep 13, 2011 9:46 pm 
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Car slowed 4 numbers throught the night. The humidity went from 45% to 77% to last pass. althought the DA dropped like 500 feet and the Bar rose 1. I really feel like the humididty caused the slow down. Generally on alky what is that telling me? Too fat? is 4 numbers acceptable?? I'm thinking not. Whatta ya think?


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 Post Posted: Tue Sep 13, 2011 10:00 pm 
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Answer is yes. How much depends on several factors but I've found that humitity does slow one down.

Now on the other side, if the air went down 500 ft DA and it slowed .04 then that might not be the case. Better air and slowing down that much could also mean it's lean. I'd put about .010 more jet in it if it's a carbureted setup and see what it does next time out. This time of the year you're gonna be seeing more and more of those kind of air changes.

Are you monitoring EGT?

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 Post Posted: Wed Sep 14, 2011 4:07 am 
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Humidity slows down Alky as it does any fuel, but its slows alky down even more and for a different reason. Humidity takes up space that would normally be Oxygen bearing air so thats an obvious one.
Whats not obvious is humidity changes the evaporation rate of the droplets. As alcohols absorb water from the air while traveling in the intake tract the droplet changes from what we assume is close to pure alcohol as kept in the tank to a droplet consisting of a mixture of water and alcohol. As the droplet gasses in the compression heat the water concentration of the remaining droplet increases. This is because the alcohol evaporates first, fair enough you say but what happens next is the interesting bit. The droplet self extinguishes. Once the water concentration becomes too much the droplet will no longer burn. There is a defined point of what size that droplet is, but its not in my memory at the moment. So the last remaining methanol molecules contained within the droplet dont get the chance to burn, they are trapped in the mainly water droplet. So less percentage of the fuel actually burns and you loose energy to the crankshaft.


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 Post Posted: Wed Sep 14, 2011 3:07 pm 
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Since methanol carries it's own oxygen molecule won't more fuel help this though? :-k

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 Post Posted: Wed Sep 14, 2011 5:23 pm 
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Ken0069 wrote:
Since methanol carries it's own oxygen molecule won't more fuel help this though? :-k
No cause thats just an AFR thing. You have to use a high quantity of liquid per cylinder with methanol because its got an Oxygen. Take that Oxygen out and you have Methane a straight HC fuel.
The Oxygen atom in methanol is holding onto the carbon atom and one of the hydrogen atoms. This leads to 2 principal methods of burn. Both methods occur in an engine but they occur in different relationships. One method is low energy the other is high. There is also a combination of the 2 methods but Im only talking about the extremes.
The most common way to see the low energy method is in normal aspirated race motors where the CO remains and the H's burn with the atmospheric Oxygen's. From what I've seen with Methanol gas readings the CO2 levels are only high when the mixture is leaner than maximum power. As soon as you richen it up the power comes up and the CO2 drops and the CO goes very high. Indicating a change in the percentage of each elements contribution to the energy output. The CO content goes out of proportion with the changes in crankshaft power rapidly, indicating residual CO rather than CO formed from combustion. Residual CO is when the CO part of the Methanol molecule remains as unburnt, basically its there but its cold so its not contributing to the energy level of the chamber. Said another way unburnt is when the atomic bonds are not broken, so energy is absorbed but not enough to break the bond. Thus the crank output is not in proportion to the gas percentages.

The second high energy release method of burn is to break the entire Methanol molecule apart and recombine each element. If the energy input to the Methanol is much greater than a NA engine can achieve, as in very high boost forced induction, the Methanol molecule can have the CO bond broken before combustion. That situation releases a lot more energy as the Carbon then forms as CO2. So you get a different gas percentage balance and more crank output. Thats how a Turbo indy engine does it. If they didnt have rules restricting boost levels they could be even more efficient.
In a NA motor there is no where near enough compression to crack all the CO's. You simply cant get enough because to do so would result in a chamber that small at TDC that it would be all boundary layer. So you have to supercharge to get maximum fuel efficiency from Methanol OR you have to use very sophisticated ignition control coupled with very accurate analysis of the start of the AFR per charge per cylinder and run the engine very lean and obtain enough heat that way to crack the CO just in time but not too early or you melt everything. Thats why methanol is so aggressive when you get the tune wrong in a power application. You can run Methanol very lean at light loads no problems and get good fuel economy from it etc. but then you have ignition reliability issues as its that lean, so you need multiple point plasma ignition. Opps a bit off track huh.

Well anyway humidity stops the droplets from finalizing there contribution to the burn, thus lowering the temperature and forcing more residual CO that is of no energy value. So basically your power goes down more with Methanol per given humidity change than it does with gasoline. Of course if you rejet then you reset the amount of fuel that can absorb energy from compression etc and you reset the atmospheric Oxygen contribution (to a higher percentage ) and you get a lower power loss compared to ideal air.
Now the reason why different people have different methanol experiences with tune up setting etc for different airs is their engines are supplying energy to the fuel in different manners. Gasification is what its all about and you can gas a liquid by adding energy (eg heat) or by removing energy(eg pressure). Its the balance of these 2 methods that determines how your engine responds and how it makes power. For instance you can run engines cold and make power or you can run them hot. You need different fuels and designs to do either correctly.


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 Post Posted: Wed Sep 14, 2011 8:11 pm 
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I've heard of many ppl running methanol on the phat side as it's said that humidity has less of an effect on it that way. I still say that if it were mine I'd phatten it up and try it as he's got nothing to loose to find out whether it's better or not. ;-)

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 Post Posted: Thu Sep 15, 2011 1:03 am 
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Yes thats correct, running it Phat will make less change with humidity. The reason is because when you run it phat you get high residual CO so your burn is more of a hydrogen only style burn and Hydrogen isnt affected by humidity. The way we burn methanol in our race engines is far from correct.


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 Post Posted: Thu Sep 15, 2011 5:01 am 
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Ok let me ask it this way....if a naturally asp engine is tuned properly for burning methanol and the afr is right, what way would you have to go to make it less suseptible to humidity..rich or lean? I'm sure the answer is in Shrinkers post I have to just read it 7 more times. Although the car has been most consistent ever I feel like it is on the rich side with .155 jets and here is why. I race from 18:00 to 23:00 on Tuesdays. The swing in weather conditions can be dramatic but also it can be consistant through out the night. So far if the Bar stays the same only increasing 1 or 2 numbers and the DA drops 1000 ft from the start of the night to the end with the humidity rising 25% starting from 35% It will pickup 1 or 2 numbers not slow down.. The next time out with lower Bar and same/higher Da with same start humidity it will be slower right out of the trailer. The other night the DA was very familiar, the bar was lower than the last time out by .20 and the humidity did what it did as described in my begining of this thread. Car slowed progressivly as the Humidity increased although the DA went down and the Bar raised by almost .02. Also I have 2 temp gauges installed, one in the back of the pass head and one right above the thermostat housing that showed 0 temp rise while making the passes. I know if you were to use temp increase/decrease as a tuning tool on my setup it would be valid as atleast the rear gauge in the head is slow to seeing cooled water from the rad and the front is more sensitive to changes. If you go by the logic that you should see atleast 5-15/20 degree rise in the quarter mile then the info I am getting is saying its rich also. Egt and o2 are monitored and showed it to have richened up. I am leaning on the side of taking 5 jet sizes out of this thing .


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 Post Posted: Thu Sep 15, 2011 5:44 am 
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That's why I went back to gas.
The car does what the weather station says it will do instead of a wild guess.

The richer the methanol mixture the slower it will get as the humidity rises. Trust me I have tried it all.
The only thing that helped was adding 5% Acetone.

Think about it. Methanol is a water based fuel. As the humidity rises so does the water content in the mixture. You can't burn water.


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 Post Posted: Thu Sep 15, 2011 7:25 am 
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What does the acetone do?

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 Post Posted: Thu Sep 15, 2011 7:51 am 
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SonnyJames wrote:
Ok let me ask it this way....if a naturally asp engine is tuned properly for burning methanol and the afr is right, what way would you have to go to make it less suseptible to humidity..rich or lean? I'm sure the answer is in Shrinkers post
The answer in my post is that NA engines are NEVER correctly tuned for running alcohol. AFR is not the issue, sufficient energy to crack the methanol molecule open is the issue.
Here's a little story. I was at a speedway meeting near a forest and the air went really cold all of a sudden and the track became enveloped in fog. Some racers asked me if your supposed to richen up or lean off. They had a different carburetion system to us, they had normal Emulsion carbys with boosters etc and the class was restricted to 10:1 compression with standard engine cams, no porting etc. I told them to richen up because the air had gone very cold and they would need to do that so that their burns didnt go to a lean hydrogen state and they also had large droplets so they wouldn't suffer extinguishing much of the mix. Large droplets work in humid air. Because the class was on the low side of optimum compression they needed to enrich-en in order to obtain enough gas is what I told them. I admitted to them that we on the other hand with far finer droplets with a laminar flow carby and a water heated plate that the fuel blasted onto had no vaporization issues so we were going to lean it off because our issue would be much more water absorption caused by greater inter-dispersion of water between fuel droplets and we had to lean it because there was less oxygen in the air. I told them we would have an issue with the engine burning way to cold so thats why we were leaning. I received some pretty bad glares because they thought I was deliberately trying to fool them. We broke the 8 lap record by 8 seconds and lapped the guys who leaned off instead of richening. The guys who went richer nearly kept up with us. The moral of this story is what you have to do in tuning is totally related to your vaporization level.

Scott Smith has said in another thread his engine goes slower on methanol and he's sure if he had less compression then it might go faster compared to its gas performance at that lower compression. Thats a valid assumption. What happens chemically is there is a zone of where the burn is a combination of low and high energy. In this zone you get CO2 formed but its not done by a complete recombination of 2 0's with a sole C. In other words all the bonds are not formed, your only forming half the bonds as the start of the process is from a residual CO. It only takes one O to add to that CO to make it a CO2 so the crank energy is low. Because CO2 uses twice the number of O's you finish up with half the number of molecules. So the pressure is less and because you have only bonded one O you dont release enough heat to raise the pressure much. So you end up with a cold chamber full of CO2. If you crack the methanol molecule open and then bond 2 Os with the C you get maximum heat release and the same number of CO2's but at a higher temp so the pressure is greater. See the limiting factor in all combustion is the number of Os available. Fuels with oxygen contained within them actually have LESS heating energy than straight fuels. The power of methanol comes not from its bearing of an oxygen but from its latent heat of vaporization cooling the charge.
This zone of combining the 2 styles of burn with methanol is a zone where you are swapping heat from correct CO2 formation for reactions that create high numbers of CO's and possibly CO2's that are formed from the original CO bond part of the original methanol molecule. Its how to make a jump over this zone and into the high energy mode thats the problem. Its like a quantum leap of faith, you have to go stupid with the boost pressures, and it goes pop into the high energy mode.
Thats as plain as I can make it. That description is in general speak and is not perfect science as that involves all sorts of things I dont understand but its the way the general proceedings go. If you can get the concept in your mind of combustion proceeding that way you can understand anything you need to know for a tuner.

Combustion is not a simple process of destroying a molecule, its actually either partially or fully destroying it (back into elements) and reforming it into other compounds and then destroying them until you loose enough energy (via imparting it to the crank etc) to stop destroying molecules and just finish up with what ever is in the exhaust. You have new compounds formed that are not in the fuel and you have those compounds reacting with one another and creating even newer compounds some that we cant even do outside an engine. I even created Diamonds in a combustion chamber once, its wrecked the piston and barrel but they were there, albeit very impure ones. I can tell you it takes power levels of over 10hp per cubic inch to do that.


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 Post Posted: Thu Sep 15, 2011 9:52 am 
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This concept of Density altitude is in my view useless for a racer. You can swap around barometric pressure and temperature and have a constant DA. What the use of looking at that figure then. As far as engine's go some need the temperature to increase to gain power some need the density to increase to gain power. Humidity is better measured and used as water grains. That makes more sense to me for tuning. You can at least think along the lines of " Oh; I've just pored this much water into my engine" oops.
As for Methanol NA engines Ive seen a trend where 65% humidity seems to be a cross over point of where engines start to loose power. Below that they can gain or be stable on methanol and the power can follow other factors like Baro. Above 65% the power seems to drop in relation to mainly the humidity. But others may have different ideas.

SonnyJames wrote:
Egt and o2 are monitored and showed it to have richened up.

That may well be the truth but you have to be careful as to how much value is placed in the accuracy of the O2's. Because the reactions can lead to major amounts of CO, (even more % than there is CO2) the Wideband will have a high demand for outside O2 to react those CO's The amount of CO wont be in balance with the HC's so the WB goes flat out sucking in outside O2 to react everything back to stoich. Thus it may be telling you that its got that rich you need to pull 5 jets. Just be careful doing that OK.


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 Post Posted: Thu Sep 15, 2011 10:35 am 
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All of this is why I ultimately use the time slip for most of my tuning and the other stuff (O2/EGT, etc) just verifies what the time slip says when I make changes, ie, if I make a jet change and it slows down then I should be able to confirm this with the engine data.

Never heard that 65% humidity thingie but will log that in my memory bank and check it out next time I have the opportunity. ;-) See, I may have learned something today. ;-)

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 Post Posted: Thu Sep 15, 2011 5:24 pm 
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Let us know if you find the same trend.


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 Post Posted: Thu Sep 15, 2011 6:32 pm 
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Ken0069 wrote:
All of this is why I ultimately use the time slip for most of my tuning and the other stuff (O2/EGT, etc) just verifies what the time slip says when I make changes, ie, if I make a jet change and it slows down then I should be able to confirm this with the engine data.

Thats whats important isnt it. Thats giving an engine what it wants. I do it that way as the first steps of tuning. But to get the last edge you need the right equipment and then you need the understanding to form an imaginative minds eye picture of whats going on in the chamber. Over time you can see things in different engines and eventually all your observations and thoughts connect and the AHH HAA moment happens.
Data loggers are good for checking on conditions of things, they can tell you if a cylinder has gone off or a carby has a problem a long time before it destroys something. Ive picked up worn lifter rollers and saved the engine by reading the EGT's.

Every engine has an optimum vaporization level for most efficiency. Every use of an engine has a different level and every fuel has a different level. The techniques needed to achieve whats necessary vary widely. Ive spent decades trying to understand these issues and the more I know the more I realize I don't know enough.
The air is the problem, its how it reacts to water saturation (called dew point) that is hard to understand in the final outcome of how the combustion proceeds. For instance do you know if you are reaching dew point inside your intake manifold? Is it condensing at the valve curtain? How do different factors like port volume and turbulence affect water interaction with the burn? Because Methanol is hygroscopic its always going to react in different ways in different engines under humidity test conditions. The main thing to have is the right ignition energy. Methanol is greatly affected by ignition energy, much more so than gasoline is. Its how you prepare the fuel prior to spark and how you deliver the spark energy and what time frame you deliver the energy over that affects the all important flame kernel. Ignition energy is capable of dissociating water. So now that dissolved water in your tiny methanol drop thats just been arc blasted is contributing to the flame kernel energy release rather than reducing it.
With anything, its how you build the foundation at the start that determines the success of the rest of it. So the best racer approach is to try different things and make notes and over time to figure out what matters. Gasoline is the best fuel combustion wise for normally aspirated racing.


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