Track Tac

Starting point for Methanol jetting for high compression 450

ABR #69

ABR #69

Member
Going to post this in another location for more ideas.

First off at this very second I can't tell you what jets are in the carb.
I have a high compression 15:1-15.5:1 KTM 450sx-f. FCR flatslide keihin carb, with quickshot II.

Right now I'm mixing 110 race fuel and 93 at 50/50 as per my engine builder.
He has never tried any of this on methanol, so he doesn't know where to start.
Can anyone give me persay a possible amount increase in jet size from my current jetting as a good place to start, or must you know the current jetting to even begin? I will find out the jetting, just have to get to the shop and get it pulled apart to start investigating.

I'm just guessing, but I'll more than likely need to adjust both jets? Since the amount needed vs gas is higher regardless. Just wanting an idea where to start vs my current jetting. Any help would be much appreciated!
 
ABR #69 said:
Right now I'm mixing 110 race fuel and 93 at 50/50 as per my engine builder.
He has never tried any of this on methanol, so he doesn't know where to start.
Can anyone give me persay a possible amount increase in size from my current jetting as a good place to start, or must you know the current jetting to even begin? I will find out the jetting, just have to get to the shop and get it pulled apart to start investigating.
Click to expand...

a good place to start would be twice the area in the Jets. I could give you actual numbers if you could tell me what's in there now. And notice I said area, not size. pi r sq.

From the desk of Al Nunley
Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory. (Al Nunley)
 
Increase both jets the same amount?

Thanks Al, glad you're back, I knew this would be right up your alley.
 
ABR #69 said:
Increase both jets the same amount?

Thanks Al, glad you're back, I knew this would be right up your alley.
Click to expand...

you're welcome and thank you.

Both Jets by the same percentage? A good place to start. You might play with a little larger low-speed jet and see what happens. Going from a .022" to a .023" is a 9.2% increase. If you had an air density gauge, from the instructions, you would see that a 1% change in air density calls for a 1% change in jetting.

From the desk of Al Nunley
Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory. (Al Nunley)
 
I did a Duck on it and found this, hope it helps and I don't know if it's what you need but, down the bottom of the page is a FCR alcohol jet kit.

http://www.showandgo.com.au/jet/jet.htm?jet_bf.html~mainFrame


ps... you really need to know a lot more about it then just throw the alky kit in and go, or your likely to toast your engine.


It's all about how fast each type of fuel burns. Burn it too fast and you'll burn a hole in the piston. Burn it too slow and it will puke or explode out of either the top or bottom end. Burn it just right by supplying the right air/fuel mixture at all rpm's and it will have the available hp to go when you want it to go, assuming you have available grip.

Unless you know exactly how to tell if your burning your fuel just right; too fast; or too slow; expect it to cost you to learn about it. If you can choose, choose to fuel it on the rich side and lean from there. IMHO, never choose to start on the lean side OR A MIDDLE GROUND GUESS, on fuel mixture. If you must start off with a guess, make darn certain your guess is accurate towards the fat side.

Right now you have this supposedly hopped up 15:1 compression engine running on stuff "not" from the local gas station, which should be enough to spin your kart wheels anytime you want and on your own your going to try running it on alcohol? If it really is like I assume someone told you or your engine builder told you, it may not be possible to run it on alcohol. At the least the percentage of gain from alcohol over what your using, is decreases because of the increased compression. I think your dreaming about it and beyond reality, but it's a fun dream and the same dream all racers have. ... :)


At the LEAST, your running a finer line between extra power, blowing it up and burning a piston, with a 15:1 compression ratio engine. At the least it nets out to 15:1 being about the reliable limit, using alcohol and if your not at a reliable limit of experience, I recommend you stay away from, ON YOUR OWN, alcohol and 15:1 compression ratio. As compression ratio goes up, the line you have to walk gets thinner and your at the limit if you switch to alcohol.

and... this is all just IMHO and ain't necessarily right anyway. ... :)
 
Well, I've run methanol in karts for most of my karting career. So. I have plenty of experience with that. Just never on any engine this high compression, and with this type carb. Is the performance really that neglible in a high compression engine on methanol vs higher octane race fuel? I'm just in the beginning stages and trying to gather as much info as I can before I make any moves. We run methanol and it's readily available, so aside from jets and and a few other things. I'm not going to be out much baring engine failures obviously.

I understand most people caution against work outside of your knowledge, but we don't learn much that way. And, with the knowledge I do have, I'm hoping it's not a costly learning curve.
 
Al, is there a common sense compression ratio limit, for a kt100 on alcohol? I'm thinking you have experience or are knowing about it for the kt100.

And I'm guessing your going to say it's also around 15:1, but I don't know so I'm asking. I'm thinking if you agree, it's another reason he should stay away from trying it on his 15:1 engine.
 
Flat slide cards like the FCR are often converted to alcohol for the 600cc micros sprints. There is more to converting them than just jet changes. Passages require enlargement as well. Odum Specialties http://www.odumspecialties.com/ did mine and they are outstanding. You might want to check them out.

DK
 
That's interesting Don, I really appreciate that. I wasn't aware there would need to be major modifications done to a carb like that for a single cylinder, but it's definitely something I'll have to check into. Makes sense, but just figured they flowed well enough for methanol since they run the same carb on 610-690 sized engines on gas with only jet changes.
 
KTM 450sxf should be a wicked build on a kart. My buddies 450sxf trounces my crf450x in power. Another company that specializes in converting carbs for alcohol is FTZ out of Missouri.

DK
 
If i were going to consult someone about this it would br Jon Brogden here on bobs. He is a carb Guru and worked for E.C. Bert for many years.He would be able to give you some valuable input on what to do.
 
paulkish said:
Al, is there a common sense compression ratio limit, for a kt100 on alcohol? I'm thinking you have experience or are knowing about it for the kt100.
QUOTE]
no conversation in this area, (compression ratio and octane) can include both two cycle and four cycle engines. They're different animals. With two cycles, the effective compression ratio is used, that is, the area above the exhaust port is used to calculate the "effective compression ratio". The effective compression ratio of a stock KT 100 is about 8-1. The combustion chamber volume being 9 CC's to the bottom of the spark plug hole and the exhaust port opening at about 92 degrees ATDC. The other thing about the two cycle is the expansion chamber. Effectively, it's almost like putting a supercharger on the engine. The racing two cycle, as normally used in kart racing today, with an expansion chamber, produces in the neighborhood of twice the horsepower of one without an expansion chamber. No four cycle exhaust system comes even remotely close to doing that. The other thing that prevents a comparison between a four cycle and a two cycle is the oil in the fuel. The four cycle doesn't have it, and the two cycle does. Oil is much more susceptible to detonation than either alcohol or gas.

I have read that alcohol, at the proper mixture, produces about 10% more power than gas. Of course that's with all engine conditions being equal. Mostly compression ratio. Thing is, because alcohol has a much higher octane rating than even the best race gas, this means you can run more compression, thus making more horsepower. With a 15 to 1 compression ratio, you have to watch out for the detonation, which kills horsepower. One of the best ways I've found to detect detonation is with the exhaust gas temperature gauge, (EGT).

A book could be written on this subject, which I am not prepared to do, so I hope this little bit helps.

From the desk of Al Nunley
Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory. (Al Nunley)
Click to expand...
 
Don K said:
KTM 450sxf should be a wicked build on a kart. My buddies 450sxf trounces my crf450x in power. Another company that specializes in converting carbs for alcohol is FTZ out of Missouri.

DK
Click to expand...

FTZ is a very good one, they did my yz450 methanol carb
 
William,
I would call Jon Brogden. If you still have my # call or text me and I'll get you his number. He knows his business on carbs.
Wes
 
Thanks everyone for your input, I've gotten some very useful information.

I'll be making some calls and doing some more research myself on different aspects.
I actually spoke with Jon about a Tillitson and need to get it over to him. Might end up with both carbs going there!
 
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