Dyno questions

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Rohan, Methanol has only 80% 0f the calorific value of petrol however when both are near their best jetting, you use nearly twice as much methanol. I believe the best fuel option would be the BP JA and JB that I mentioned, where there is a substantial amount of hydrocarbon (benzene) to provide energy, yet still enough methanol to freeze the charge and make it denser. Methanol is poisonous, however it doesn't do to your blood anything like benzene does. I would never try blending my own fuel at home, it is almost impossible to do it safely and accurately.

T Bolt, a standard commando engine converted to methanol using 34 degrees advance and separate pipes will go faster and pull harder than the same motor on petrol. The numbers mean nothing to me. My bike has the cam advanced and a two into one pipe with a large dia. tail pipe and muffler. The ports are tapered and I use 34mm carbs, and previously a 4 speed a CR box. It was fast enough to win, but slow off the start because of the extremely high first gear and the need to slip the clutch. I'm not making claims about my own bike, however from 12 years of difficult road race experience in open capacity class racing back in the 70s, I just know that the way that it performs is enough, - the rest is in the riding and the gears, and avoiding over-revving.

Advancing the standard 850 cam was a crude dodge and I believe it was barely OK, but the error in the exhaust closing point seems to have been compensated for, by the pipe. I've got a combat cam, and when I eventually fit it, the advance I use will be 6 degrees ahead of standard. It is what I intended to use when I first built the bike, however my cam grinder man was hard of hearing. I don't know how the PW3 cam performs, however I don't like increasing the lift over that used in road bikes. I believe that timings which suit the pipe and inlet tract length are far more important. The combat cam looks good to me, and I'm wondering what it will be like when used sensibly.

The commando engine is very impressive, - I like it a lot, however I'm still expecting the big bang. I still find it difficult to believe that anything so agricultural can be raced. It keeps me amused.
 
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acotrel said:
Methanol has only 80% 0f the calorific value of petrol however when both are near their best jetting, you use nearly twice as much methanol.
.
Check your facts, that doesn't make sense.
 

texasSlick

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Acotrel is right.....methanol has less heat content than pump petrol....actually about 50% rather than 80% as he states. Acotrel also states he burns twice the quantity of methanol, which makes sense if the energy content is half that of petrol.

Rohan is right in that it makes no sense that methanol gives a racer an edge having less energy content....the laws of physics must be obeyed....can't get more from less!

At first, I agreed with Rohan....methanol must have a higher energy or heat content. I researched it and found:

methanol has an energy content of about 57000 btu per gal (petrol about 135000)
methanol has a higher heat of vaporization than petrol
methanol has a higher octane value...about 112-114
methanol has a burn rate of about 60% that of petrol

so how is it that racers favor methanol?

From a safety concern...methanol fires can be extinguished with water, although the flame is invisible.

At this point, I am stretching my knowledge, and welcome Acotrel's input, as he seems to have more practical experience with the fuel than any. Applying my engineering knowledge to the problem I theorize the following:

a) the higher heat of vaporization takes heat off the engine, tending it to run cooler
b) the higher octane rating allows higher compression ratios, which tend to make the engine run hotter.
a) and b) offset each other with respect to engine temperature, but the higher compression ratio is a racing advantage.
and now c) :

the slower burn rate yields more torque....Acotrel wrote way above, "torque wins races", and I agree. Again I want to stress this is my theory...I do not wish to post anything as fact unless it is scientific fact. Now for data to support the theory:

At the university where I once thought, we had several test bed engines fully instrumented. These had pressure transducers in the heads so we could get a pressure signature. Right after ignition, pressure spikes rapidly, then after the piston starts down the power stroke, the pressure falls nearly as rapidly due to the increasing cylinder volume as the piston moves down the cylinder. Now consider a Diesel engine...we all know they are torque'ers. They get the torque by the injectors continually pushing fuel into the cylinder, even as the piston is moving down the power stroke. This addition of fuel, when burned, keeps the pressure from falling off as rapidly as that of the gas engine...hence more torque.

Now the slow burn rate of methanol, mimics the Diesel effect....the fuel burns slowly, producing less of a peak pressure, but sustains the pressure longer than petrol, producing more torque.

Finally, it seems to me that peak horsepower on methanol is less than petrol, because of the lower energy content, and also because at top RPM, the slower burn rate means fuel is blown out the exhaust before optimally completing the burn.
 
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Please, quote me correctly ?
I earlier said that methanol has approx half the energy content of petrol, and (in common 4 stroke engines) you'd burn about twice as much methanol.
So the power output is about the same.
As I said...

However, WITH HIGHER COMPRESSION RATIOS, much higher in fact, you can get a LOT more power.
Speedway engines running methanol typically have ~ 14:1 compression.
Thats why they have so much power, and the meth keeps them cool while they churn out all the hp.

No reason why a Commando engine couldn't be set up similarly.
In fact, thats how many of these Triumphs and Atlas's you see in Classic racing are so fast.
If the rules allow...

Course, you need all the 4C's to chime together.
Cams Carbs Cubes Compression.
 

texasSlick

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To Rohan:

Sorry, I mis-interpreted what you were referencing with "that makes no sense".

For me, it made no sense that a lower heat content fuel would give a racer an advantage. I was concerned others might be similarly confused. After researching the properties of methanol, I formulated a theory as to why this occurs....which you verified quite well. Your experience supports my theory as to engine temps and compression ratios. I would still like to have input on the effect of burn rate.

I did not read the posts thoroughly to find where you stated that methanol's heat content was half of petrol, and that twice the fuel consumption was to be expected.....In that, my post supports you.
 

johnm

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I think Im beginning to waste my time here so this will be my last post.

If you do the chemistry carefully you will find there is in fact a small but not insignificant increase in available energy using methanol. (Lower CV per unit volume but proportionaly more unit volumes)

In practice it equates, for a give CR, at around a 5 % bhp increase.

On the track this translate to being able to pull a higher rpm on a given straight for the same gearing, or the ability to pull higher gearing, lower lap times and better ridabilty especially at low mid range.

All I can offer is the personnal experience of having done it.
 
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Tex, Years ago a few guys used to run a 4 inch diameter cool air duct from the front of their bike to the carbs on their manxes. It wasn't a silly idea.
The higher latent heat of vaporization means that to vaporize methanol it takes more heat. If you physically vaporise it in a carburettor it takes heat from the carb, the inlet tract, and the incoming charge making it more dense, so the mixture must be richened (compared with petrol) give the correct combustion to give max power without burning pistons. Because you've then richened the mixture more heat is dragged out of the incoming air, and the whole process repeats until an equilibrium point is reached where the cooling effect, and the required combustion mixture are in balance. The reason you use twice as much methanol as petrol hasn't got much to do with calorific value, it is more because you use twice as much of it to get the balance between air and fuel correct when the air is at very low temperature and much more dense, so that the oxygen content is higher. The big cheat is in using nitromethane in the mix so that chemically bonded oxygen is available, but then you have to use lots of it to get the material to provide sufficient energy with the mixture in balance. You cannot safely use nitro in contact with hydrocarbon compounds such as petrol or benzene to provide an energy base. What I've said about BP JA and JB, is that there is sufficient cooling effect from the methanol to increase the charge density, however the charge carries benzene to provide energy. I suggest that JA and JB are used at a slightly slower rate than pure methanol however the energy release is greater per volume used. High comp ratios with methanol give a much bigger bang because the temperatures are higher, and more fuel is thus used to get the mixture correct , but can make top end motor much nastier. A lot of guys go straight there without trying methanol with the standard comp. My feeling is that the combustion chamber shape on the commando is excellent, fitting a high domed piston to get higher comp. could be a backwards step. In Triumph engines it is a dog of an idea , half the charge is left unburned due to the plug being masked by the piston crown. I used 12 to one 650 pistons in my 500cc short stroke Triumph which gave effective 10 to one comp. ratio, still with that masking effect. I think the only way it could have gone faster would have been by welding up and reshaping the combustion chambers using flat topped pistons. The Paton 500 doesn't have that problem, and it has twice as many valves.
 
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Johnm, Thanks very much for posting on this thread, you've confirmed much of what I've come to believe through hard graft, and I now think there is value in dyno testing.
 
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johnm said:
If you do the chemistry carefully you will find there is in fact a small but not insignificant increase in available energy using methanol. (Lower CV per unit volume but proportionaly more unit volumes)
In practice it equates, for a give CR, at around a 5 % bhp increase.
When you run methanol a shade rich, for better engine cooling, you then lose 5% to 10% of the possible power, so you are back about square.
Unless you compress it a lot harder, and up the ole thermal efficiency.

acotrel said:
The reason you use twice as much methanol as petrol hasn't got much to do with calorific value, it is more because you use twice as much of it to get the balance between air and fuel correct
Yes and No, although some of this is true. The reason/short answer is that methanol only contains approx half as many carbons and hydrogens, and extra oxygens, so you need to use about twice as much of it to burn up all the oxygen. THUS, it has does have about half the calorific value. These are hydrocarbon fuels and variations of, after all, and cause and effect is all interlinked.

Lets not confuse the science here, this is all very well known and understood - and documented.
 
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acotrel said:
Tex, Years ago a few guys used to run a 4 inch diameter cool air duct from the front of their bike to the carbs on their manxes. It wasn't a silly idea.
The higher latent heat of vaporization etc .
In some respects, this seems counter-intuitive ?
If it draws warm air from behind the cylinder head, the warmth will assist in the vapourization ?

Along the same lines, piston engined aircraft have a lever to pull, that provides warm air into the carbies - stops them icing up.
And thats running on avgas.

I've seen a 650 Triumph running methanol, where we actually put cardboard shielding in front of the engine, to keep the engine temperature up.
Cold day, it almost needed the choke kept full on otherwise...

Pulling COLD air into the cylinder, provided its jetted to suit, will increase the charge density and thus power.
This is why you see air ducting on GP (and some roadbikes) to keep heat away from the air going into airboxes.
This is something like 5% to 10% more power, for free.... ?
 

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Rohan said:
johnm said:
If you do the chemistry carefully you will find there is in fact a small but not insignificant increase in available energy using methanol. (Lower CV per unit volume but proportionaly more unit volumes)
In practice it equates, for a give CR, at around a 5 % bhp increase.
When you run methanol a shade rich, for better engine cooling, you then lose 5% to 10% of the possible power, so you are back about square.
Unless you compress it a lot harder, and up the ole thermal efficiency.


Lets not confuse the science here, this is all very well known and understood - and documented.
I will regret this and Im breaking my last post promise but :

I do not have a degree in chemistry but I do have a BSc Hons and a MSc degree so I am familiar with scientific methodology. Before I went to methanol I did my research and did check my assumptions with a good friend who does have a BSc in organic chemistry.

Please read the following. It is published by the Engineering school of Colorado State which is very good US Engineering school.

http://www.ext.colostate.edu/pubs/farmmgt/05010.html

There are several other places on the web where you can find actual worked examples of the calculation.
 
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Johnm, I'm glad you broke your 'last post promise ' and I hope Rohan reads the article that you've linked to. I don't think running methanol/petrol mix in cars using public roads would be a good idea. If methanol runs rich, the products of combustion include formaldehyde and formic acid. The first is a listed carcinogen, the second is the acid ants inject into you when they bite. Even ethanol in fuel can produce acetic acid which can be quite nasty. As a racing fuel in any four stroke motor methanol is great, in a two stroke it is a pain in the butt. It is expensive however it gives a substantial power boost. I have always used it when racing even in my T250 Suzuki road racer, with which I once blew off a good TZ350 Yamaha. I sold that bike to a guy who won 5 historic championships and 28 races with it. I didn't like the bike even though it was extremely fast, it was not what I wanted to race . My Seeley 850 is a real hoot, you can feel the hair growing on your chest when you ride it.
I still intend to make a video of a start-up , when the weather dries out here . I think it will give you all a laugh.

I think Rohan is trying to say that methanol does not give an appreciable power boost. - He should try it some time.

 
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Rohan, I don't believe you can predict calorific value of a fuel by adding up the effect of the constituent elements in its molecules from the stochiometry. Your theory is great, however the only way to find out what it is, is to use a calorimeter and do the test.
(A lot of our Australian civil laws and our national standards used to be empirical and prescriptive, however these days we are moving more towards performance (risk) based legislation. The theory behind those old laws was great however the outcomes were often indeterminate .)
 
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acotrel said:
I think Rohan is trying to say that methanol does not give an appreciable power boost. - He should try it some time.
I am not 'trying' to say it, I am saying it.
People like Phil irving also say the same thing, so some of us are in the same tune.

I was involved, slightly, with an iron engined 650 Triumph running methanol for speedway use.
This had no mods other than running methanol as a fuel, and suitable jets and taps.
Other than running quite cool, it showed no sign of being more powerful.
Although it wasn't put it on a dyno...
 
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johnm said:
Please read the following. It is published by the Engineering school of Colorado State which is very good US Engineering school.
http://www.ext.colostate.edu/pubs/farmmgt/05010.html
.
No offence John, but that link is useless to any argument.
It doesn't show a graph of methanol fuel use ? - just a hearsay throw-away-line.

It DOES mention that compression ratios can be increased to give more power though.
That IS the real magic of methanol as a fuel....
 
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acotrel said:
Rohan, I don't believe you can predict calorific value of a fuel by adding up the effect of the constituent elements in its molecules from the stochiometry.
YOU may not believe it, but as a general rule it works pretty well.
Allowing for that each compound will have its own properties - and peculiararities.

We may not be able to entirely accurately 'predict' it, but a look at any table of fuels, inc the one in the link johnm showed, showed that as the fuels get longer chained molecules, (and heavier) the kilocals or btu's/lb generally increase. Thus methane and methanol and butane, which are the lowest order shortest molecules of fuels around, are also the least energetic - in terms of energy available when burned . When you get up to octanes and decanes and higher etc, you are getting up towards and into the diesels and heavier oils, which contain more energy again...
 

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Hi Rohan

Again with respect from my side you have a remarkable abilty to pick and chose the parts of any document which suits you and ignore the rest.

First off.

I agree and have always have agreed that being able to increase the CR without detonation is a major advantage of methanol and the way to get a significant hp increase. I have never ever questioned that.

But there is a also a small but useful improvement even if the CR is not increased.

Ex Professors from Engineering Schools like Colorado State do not make " hearsay throw-away-lines " when they are writing in a peer reviewed publication for their university.

And Phil Irving does NOT say there is no other advantage to methanol other than increasing CR. He in fact says that there is an improvement in hp without increasing CR because of the cooling effect in the inlet tract. Go read your edition again or get a latter edition if you cannot find it.

Plus are you telling me the stop watches we used in back to back races with and without methanol for a NZ title are wrong. Maybe we should send the cups back!
 
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johnm said:
Again with respect from my side you have a remarkable abilty to pick and chose the parts of any document which suits you and ignore the rest.
If part of the 'information' quoted in a discussion anywhere is wrong, then the whole discussion AND conclusions are potentially flawed.
That is the 1st law of scientific discussions.
I expected more of a university discussion if they were being quoted as an 'authority'.

Lets find a dynochart of a bike somewhere run on petrol and on methanol on a dyno, for comparison then.
There is no denying that engine cooling is a VERY big part of methanols advantage for racing.
But nothing I've ever seen or read says you should expect great gobs of extra power just by changing to plain methanol from petrol.

However, with miniature aero engines, adding some nitro (nitromethane) into the methanol sure added some power. !!
This is SO popular, you can buy it premixed in cans to different %'s, ready to fly...
Little aero engines have the supreme advantage that they have infinitely adjustable mainjets,
and you can rev them on the ground to get the tune spot on before destroying anything...

The real advantage to methanol fuels is of course its ability to operate in ultra-high compression ratio engines.
Thats where the real power comes from...
 
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