Methanol Fuel for Racing (4 stroke engine), AFR? rust inhibotrs?

[ordengineering]

How is the correct air fuel ratio for methanol in 4 stroke engine.

many people said "between 4.5:1 - 6.5:1"
i've run 5.5:1 and my piston melted....
what is the correct number?

and there was also a tips that recomended us for blending some castor oil to prevent rust for methanol fuel.

please let me know any information about this anti rust blend for methanol and the correct AFR

thank u

 

[ordengineering]

how many ammount for castor oil should i blend with methanol?
and if you have any other tips for blending methanol (such as adding ethanol by %, etc) please let me know.


forgive my english if it not well


thank you very much

happy new year

 

[evelrod]

It's been over 40 years, so I do not remember the jetting. However, I did use methanol in my hillclimb bikes, one was a four cycle and the other a two stroke. On the four stroke I went as rich as I could, until it "blubbered" and backed down until it cleared. The two cycle (a Bultaco) I went from something like a 100 jet to a 400/420 (an Amal carb) and mixed in de gummed castor oil at a 50:1 ratio. After a few events, I started using the same fuel mix in both bikes simply for convenience. No apparent effect on the four stroke, not even a lot of smoke.
Post race, I would re jet and run a few minutes on gasoline. If I did not do this, the tank and carb would get all fouled up.
One thing I do remember, if it will run on methanol, it's pretty difficult to get it too rich, but damned easy to go to lean!

Rod

 

[patprimmer]

Like Rod said.

Further, 6.5 is about the stoichiometric ratio for air:methanol.

Methanol will burn without fouling or miss-fire to a very rich mixture. This ability is used to run rich or cooling when the boost or compression is very high.

About 5 to 5.5 is typical for supercharged very high power engines.

With methanol it is more normal to tune by plug reading and exhaust gas than by oxygen sensor.A fuel system reacting to O2 sensing to control methanol typically responds to slow and between the sensor seeing the exhaust sample and the cylinder seeing the correction, often a hole is already in the piston.

Start rich, do a very sort run and look for heat discolouration of the threads NOT PORCELEIN COLOUR.

gradually increase the run time and remove fuel until you get discolouration to at least one thread and no more than 3 threads at any point.

Thi tells you the hottest te plug got, bt does not tell you if it is rich sometimes and right at other points in the rev range used.

Castor oil can be added at something like 1:4000 pats. there are several other proprietory additives that are more expensive and likely no better. They help but do not eliminate corrosion if adequate care is not taken.

There are many reasons other than nominal a:f ratio that might damage pitons.

We really need to know a lot more about your application and equipment.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers for professional engineers

 

[ordengineering]

thats what my experience last night..
i try to use an LM1 AFR sensor, and its goes error... "too rich" and babling from 9:1 to 21:1 afr....


my application was for 300cc 4 stroke motor cycle that use for drag racing. its running 15.5:1 CR, 340 degree camshaft, with Keihin PWK Air Striker Carb.

the usefull power range was from 6500-10.500 rpm.

sir what do you mean by "discolouration to at least one thread and no more than 3 threads at any point."

do you have a picture of this plug reading colour..??

a pict of correct AFR plug..??

thanks a lot sir...
-------------------------


and how about other blend to reduce corrotion sir? is there any other tips beside castor oil?

 

[patprimmer]

You need to use cadmium coated plugs. Normally a satin silver or gold colour on the metal. NKG plugs are normally cadmium coated. I mean where the cadmium coating burns off. It is very obvious once you have seen it. You can experiment with an old plug and an oxy torch to burn the coating from a clean area, like the hexagonal area for spanner grip.

You might gain by joining HRE.com

HRE is a site with good conduct like here dedicated to drag racing and has mostly info on running alcohol, nitro methane fuels and forced induction and fuel injection. It is a pay site at $40.00 per year, but I found it great value when I first started running alcohol in a blown MFI SBC door car.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers for professional engineers

 

[evelrod]

That is really close to what my 4 stroke hillclimb bike was. Mine was a 250cc (plus with a 1mm overbore) with 14.5:1 CR. I don't remember what the camshaft was and my ignition timing was as advanced as the plate would allow. Spark plug was NGK B9N . Reading alcohol plugs is difficult because the insulator always stays bright white. I try for no hotter than the first thread, maybe a bit more. I like it rich as I melted a piston in learning. The carb was a DelOrto 34mm with an "adjustable" main jet. I cannot help you with the size as I just "adjusted" it until it "felt" right.

One other thing that I forgot...When I started using the two stroke mix in the four stroke, I added 5% nitromethane to offset the castor oil. I'm not sure what that did to performance, it seemed about the same as straight methanol. That was the fuel mix that the gokart racers were using to good effect.

Keep it rich. Let us know how it turns out.

Rod

 

[patprimmer]

Heat to one thread is a good safe place to be specially when learning.

Normally aspirated engines often need a LOT of advance as either the compression is to low or the piston domes to get really high compression interferes with flame travel. With wedge heads some tuners use a slot cut through the dome between the spark plug electrode and the far side of the chamber. Methanol really only starts working OK at over 12:1 and gains all the way to 16:1 or higher, depending on chamber shape and plug location. When effectiv compression rato gets up around 18 or 2:1 is when you need the 4.5 or 5:1 A:F ratio.

A lot to rich (not just a bit rich for safety) creates problems with bore wear due to wash down and oil dilution resulting in the oil turning into a custard like consistency. Heavily diluted oil if left in the engine can corrode things, especially in the ring lands and the bearing shells.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers for professional engineers

 

[ordengineering]

thanks guys, i got the point now.. especially about the plug reading.

but, beside the plug reading method :


1. if there any good if i use wideband lambda just like my innovate LM1? i would buy it new, because i think mine was reading wrong because it has too many working hours of tuning.

2. im using this methanol on carbs, if the wideband lambda couldnt worked, can i tuned it like this way (some methanol freak drag racer guy out there suggest me this way ) :
- first i set the pilot jet and mainjet to get AFR with normal race gas on 12.5:1 accross the rpm range.. lets say i got 38 pilot jet and 110 main jet.
- then by multiplying from 12.7:1 (gas AFR) to 4.5:1 (methanol AFR). its mean it need the jetting area 2.88x times from the race gas to methanol.
so, by using a cross sectional area calculation, i have to timed the cross sectional area of jetting size 2.88 times.
and it means it was increasing its diameter arround 1.7times.

any suggestion??




oh ya, if i blend castor oil for anti rust inhibtors, you've said that it still corrosive to the fuel system.
actually how many long (hours) i should flush the fuel system before it goes wrong. because tomorow race schedule was very tight, from minutes to minutes (practice, QTT, race, final race)! it was a 10 6-8 hours of hectic, and actually the methanol things im not sure if it was allowed by the regulation or not
(but i dont care, because the race stewards wouldnt be able to find it, if i dont do a suspicious thing like "flushing the fuel system" every times i finished the drag line)

 

[patprimmer]

You can leave the fuel in the system a few days if required. It depends a lot on conditions and if you can seal the system. With injection, we can seal OK, but with carbies air will get in via the bowel vent.

You need to do a lot more than just increase jets to to run carbies on methanol. You may need to increase needle and seat, idle circuits, intermediate circuits and emulsion tubes. By pilot jets I think maybe you mean what I call air bleeds.

Bottom line is you need to ensure every part of the carby will flow the required increase in fuel.

Specialist methanol carbies can be obtained or if you can double up on the number of carbies it is easier to get the required flow as each only needs to flow half the fuel.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers for professional engineers

 

[PowerTripp]

How are you reading AFR at 5.5:1?
Lambda sensors read very inaccurately at Lambda 6.86 and many controllers are off at AFR 10.0:1. Some do not accurately display even at much leaner mixtures. Any richer than this is questionable at best.

With many sensor heaters overworked at richer mixtures, alcohols (and especially methanol) have cooler EGTs making the sensor even less reliable.

This and the variance between controllers and sensors (and their age) could easily have caused your piston problem.



Castor bean oil leaves a gummy residue that can build up under the top ring land and eventually screw up ring seal. Try using Redline "2 Cycle Alcohol Premix Racing Oil".

I hope this helps.

 

[patprimmer]

PowerTripp

Have you seen this gumming or are you taking the word of someone selling you something.

I have used castor oil for years with no problem when used at the levels listed above.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers for professional engineers

 

[evelrod]

I agree with Pat. I used degummed castor oil at 50:1 mix for years on my two methanol fueled bikes. I even rebuilt the two stroke 250cc Bultaco after several seasons of hill climbing and the ring was worn, but NO gummy deposits of any kind...NONE! I also used Castrol-R (bean oil) in my four stroke---EVERYONE (you know, the 'experts'?) told me it would gum up my engine...Of course it never did...In fact, if I could get it easily today, I would use it in my current race engines!

Ya gotta watch out for that "everybody" and "everyone" 'cause they most often are either misinformed or selling something!

Rod

 

[PowerTripp]

I did not mean to urinate in someone's breakfast cereal. But there is a big difference in normal use and racing use when it comes to castor oil.

Yes. I have seen this gumming from castor oil first hand in engines running gasoline fuels, alcohols, and nitromethane mixes. I have also seen the poor bore protection it offers in steel, chrome, and Nikasil bores, and especially in rotary engines.

NO. I am not selling anything. Just giving advice on something to test yourself.

I have spent many years building and racing two-strokes and building four-strokes. I regularly perform testing of oils and fuels for performance and protection in racing and street environments.

As you increase combustion pressures and temperatures, and especially as piston temps increase, castor provides less and less protection as it breaks down. The residue builds up, and can prevent the movement of the ring in and out of (or around) the ring land causing sealing issues. The problem is more prevalent near the exhaust port in two-stroke engines. In four-stroke engines on alcohols, where lower oil/fuel ratios are used, the castor residue can build up between the top and second ring causing sealing issues that can be measured by simple leak-down and blow-by tests, or seen on the piston skirt.

I started using the Redline oil in methanol/nitromethane mixtures in two-stroke marine outboard engines, and still use it in small amounts in ethanol blends in street and racing four-stroke motorcycles today. I use it because it protects better than anything else I have found without building up under the top ring on on the piston crown. In high rpm four-stroke multi-cylinder engines running at up to 14,000-16,000 rpm, bore seal and engine life are very important.

Not all engines and applications will see the same results. I am just sharing mine.



As for alcohol fuels requiring more compression, this is not entirely true. Like any fuel, alcohols should be run with as much compression or boost as possible for best results, but the gains from alcohol fuels are hard to beat - even at 9.0:1 compression in a NA engine. Name another commonly available fuel that gives the same torque or horsepower improvement - other than nitromethane. The cooling benefit of alcohols cannot be understated. I have yet to test an oxygenated race gasoline blend that equals methanol, and a good E90 custom blend is even better. At least on my dyno and in my track testing. And alcohols are CHEAP compared to race gas... and burn much cleaner.

 

[evelrod]

Methanol fuel is good stuff to a point...In my case it's not legal to use in our race cars...Would that I could.

I use Redline products in both the Mini and the Lotus...good stuff. That does not change the fact that I ran my bikes at least two weekends a month for several years...Never gummed anything, even when I used the pre mix in the four stroke.

I'm also from an era where everybody used castor oil in their cars and bikes. I do recall some problems, but usually attributed to the Neanderthal racers!

Rod

 

[patprimmer]

Red Line is good stuff no dispute, but it is VERY expensive and often not necessary.

I repeat, I have never had a gumming problem with castor oil at 1 of oil to 4000 of methanol. I can't speak for others or why they have problems.

Sure you can run methanol at lower compression and it runs well down to about 10:1. The lower the compression, the less the advantage over petrol but you retain or even increase the disadvantages and end up with higher indirect costs for reduced advantage. It just stops making sense.

At very low compression it will still run, but gets hard to start.

It runs so cool that at low compression this normal advantage can become a disadvantage as it can have trouble getting up to operating temperature.

It tends to contaminate oil more than petrol and it tends to wash down bores and increase cylinder, ring and ring grove wear.

Methanol is normally cheaper than petrol, but you use about twice as much and need tocarry about twice as much to retain range. This may or may not be an issue depending on distance to be travelled and time to refil. Range or fuel fuel load is not an issue for drag racing but can b in other types of racing.

The price difference varies with time and grade of petrol and mile for mile it is often more expensive than standard grade pump petrol at 90 octane or less is required for low compression engines. Once you compare it to 100 octane or over, the price advantage of methanol really starts to take effect.

Methanol is so popular for forced induction and high compression drag race engines because the extremely high output required and the short distances raced and the very high maintenance schedules to prevent or minimise parts breakage offsets the disadvantages and exploits the advantages of methanol.

Wear rarely becomes an issue for high output drag race engines as they generally break parts or time expire due to fatigue well before they wear out or gum up.




Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers for professional engineers