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increasing hp on Kohler?

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jason2

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Discussion starter · #1 ·
I have a 18 hp Kohler Command. I noticed it has the same bore and stroke, and compression ratio as the Command 20 and 22 engines. This leads me to believe that they are the same engines. Where does Kohler get the extra ponies on the 20 and 22 models? Is it with the carb? I doubt it's in the cam.

Somebody mentioned something about moving the trottle plate on a small engine to get more hp. Is this all that is involved in bumping the output on my 18?

And when they say the throttle plate are they referring to the "butterfly valve"? If so, does the throttle plate have a limiting screw or something to limit it from opening all the way at full throttle?

I know it's gotta be something simple. But I don't know what the differences are between the three engines. And I'd like to make my Command 18 into a Command 22. All three engines make their peak power at the same RPM. So it can't be govenor related. Displacement is the same, plus they all have similar idle characteristics so it's gotta be in the carb. Please help. I'm tempted to buy the new Honda 24 hp, but first I want to try bumping the power up on the engine I already have.
 
#2 ·
To change hp without changing either the bore & stroke or the camshaft you can do these things. Change carb, change the intake gaskets, change intake manifold, make changes to the intake and exhaust passages in the cylinder head, change the valves, change the exhaust manifold and muffler and making changes to the ignition timing.

Take your pick!

BTW, the govenor on these engines does not limit rpm. The govenor senses when the engine is loosing rpm and opens the throttle in order to regain a set rpm. If you were to reach down and open the throttle plate (butterfly valve) by hand you would see that these engine will rpm well in excess of 3600.
 
Discussion starter · #4 ·
Thanks guys,

Richard, I could run thinner head gaskets, or mill the head for a bump in compression resulting in a increase in power. But then I have to run higher octane fuel. And I also could port match the intake and exhaust, clean up the head etc.. But I just am looking for the simple difference between the three motors. Maybe someday I'll build a killer Kohler. :) Hell maybe somebody builds a stroker crank for these babies. Add a stout cam, open up the exhaust and intakes and we'd have some fun.

I didn't realize the governor worked the way it did, thanks for the info.

Mike, thanks for bringing that thread up, that is the thread I was looking for. I'll be taking a look at my carb this weekend. I've never owned a vehicle that I haven't done a bit of tweaking to, and now this Kohler has bitten me and I need to make it give me more power. :)
 
#5 ·
ive got a 96 command . if yours is the same as mine
you really have a 20 with a stop or somthing built
in .your dealer can make the change at almost no cost if he will. this is what i did.kohler did this to supply both hp requirements but only wanted to produce the one motor.
as told me by my dealer.
 
#8 ·
Well this sorta thing seems common with Manufacturers in any speed enhanced industry. Intel used to do this with their pentium processors. They would make a base 200MHz chip and simply underclock it between 133 and 200. So hacker types simply changed a few settings and whalla they paid $200 less for the same chip. It is cheaper to make one product and disable a few things so it is easier to sell and they will have a higher stock of product.
 
#9 ·
I noticed Onan did the same thing with the performer 18HP,and 20HP.They have same displacement,compression,cam #,and exhaust-so the only thing that can make the 2hp is the timing curve or carb size or settings.I bet its in the carburetor,not the timing.Be careful about bumping up compression on a Command Kohler,my 25Hp has 189 PSI already-that is very high,so if yours is anywhere near that ,you best leave it alone or you'll be runnning racing gas to keep from aerating the piston tops.According to my owners manual-the CV18-20 is 624CC,CV22 is 674CC,CV 25 is 725.Good luck cranking it up.
 
Discussion starter · #10 ·
I stopped by my new dealer today to ask about the differences in the three engines. The mechanic said he didn't know, but would find out.

To his credit, he returned my phone call this afternoon. What he told me doesn't add up. He said the differences are in the flywheel and the ignition.

First of all the flywheel has absolutely nothing to do with the power output of these engines. Sure a lighter flywheel will allow an engine to spin faster, and have less parasitic drag on the engine, allowing higher rpm's. But in all practicality a flywheel is not a performance adding part. Valvetrain limits rpm. Plus if the valvetrain can handle the higher rpm's (roller rockers, roller cam, etc..) the engine still needs to breathe. (Larger valves, additional fuel flow needs, etc..) These engines all make their peak power at the same RPM. Sure the flywheel may be different between a Command 18 and a Comand 22 but it isn't power related.

Secondly, the ignition definitely has nothing to do with the increase in power between these three engines. The spark plug gap is the same on all three engines. For argument's sake let's say the 20 or the 22 had a hotter ignition than the 18. The plug gap would be wider, to take advantage of the higher voltage. Which would result in a fatter spark. But alas the gap is the same. Can you bump power with a jump in timing. You bet! But at what expense? Once again all three engines have the same compression ratio. You go and bump up the timing, you need to run a higher octane fuel. All three of these engines call for 87 octane fuel. And to make a horsepower jump from 18 to 22 with timing alone, you won't be doing it on 92 octane fuel. You'll have some severe detonation problems.

So again I'm sick of being fed nonsense by a so called "mechanic". I've probably built more motors than he has, even if they are not small engines. And I believe as you all have told me it is in the carb. Big thumbs up to the lawnsite members! :) I'll be taking a peek at my carb this weekend.
 
#11 ·
Secondly, the ignition definitely has nothing to do with the increase in power between these three engines
Click to expand...
First off you're comparing apples to oranges. As John DiMartino pointed out the CV22 is in fact a bigger engine.

Since we're only talking about a 2 hp difference it's easy to turn a 20 into a 18. Just set the ignition to run the 20 on 87 octane and then ****** it to 18 hp.
 
#12 ·
Jason,
My suggestion. #1 Contact Kohler tech center and ask for the engineering dept. for small engines division. Their 800 number should be on the tag on your engine. #2Contact Walbro Engine Mgt Systems in Cass City Michigan(they recently were bought out by a company out of England however you should get them by still asking for Walbro) ask for Al Sayers Senior Engineering Technician( tell him Eager Beaver Stump Removal Service sent you) or Don Warner Kohlers Carb Engineering Manager( you have got to catch him in a good mood).
I worked with these two people at Walbro Engine Mgt.for 9 years in the engineering division calibrating carbs for not only Kohler but also Mercury Marine and both are experts on these engines. I have been gone for 4 years now however these guys are the experts. In most cases it is the venturie size and the main jet along with all the other facters described in other posts that affect hp on these engines.By limiting venturi size regulates hp.in a lot of cases on these engines and thats it.Hope this helps.Good luck
 
#13 ·
Kohler has three differant bore sizes in the command series of engines. The 18,20, and old 22 did all have the same bore, stroke and compression. They also make a new large bore 22-23 horse version. The new large bore is 674c.c. the old 22, 20 and 18 had a 624 c.c. displacement, the 25 is a 725c.c. displacement. The old 22 had smart spark ignition, new large bore does not. The mechanic was correct stating a differance in flywheels. The old 22 flywheel has more advanced timing when the plug fires, magnet location controls timing. Smart spark ignition retards the timing at low speeds and during start up to allow easy starting. Timing can make a huge difference on power. Why do you think cars used to have a vacuum advance and mechanical advance mechanisms on the distributors? Air cooled engines don't use a distributor so it is harder to change timing at different engine speeds, they have fixed timing. You can only advance timing so far or you run into hard starting and the need for higher octane fuels. By the way Kohler does use a different carb on the 18 and 20's as well. Some engines are equipped with accelerator pumps on the carb as well to give quicker throttle response.
 
#14 ·
Jason...

Take you engine parts manual and compare the part numbers between the 18 & 20 HP motors. If the ignition system or carb have a different # from one motor to the next, that is probably where your difference lies. If all the part #'s are the same, then it has to be a setting somewhere.

Good Luck,
Mark
 
Discussion starter · #15 ·
Thanks for all the feedback guys. I really appreciate all the info and helpful ideas.

I know I need to pick up a service manual for these engines.
My 18 runs like a top, just want more power. :)

I'll keep everybody informed on what I do.

Thanks again.
 
#16 ·
jason2 said:
I stopped by my new dealer today to ask about the differences in the three engines. The mechanic said he didn't know, but would find out.

To his credit, he returned my phone call this afternoon. What he told me doesn't add up. He said the differences are in the flywheel and the ignition.

First of all the flywheel has absolutely nothing to do with the power output of these engines. Sure a lighter flywheel will allow an engine to spin faster, and have less parasitic drag on the engine, allowing higher rpm's. But in all practicality a flywheel is not a performance adding part. Valvetrain limits rpm. Plus if the valvetrain can handle the higher rpm's (roller rockers, roller cam, etc..) the engine still needs to breathe. (Larger valves, additional fuel flow needs, etc..) These engines all make their peak power at the same RPM. Sure the flywheel may be different between a Command 18 and a Comand 22 but it isn't power related.

Secondly, the ignition definitely has nothing to do with the increase in power between these three engines. The spark plug gap is the same on all three engines. For argument's sake let's say the 20 or the 22 had a hotter ignition than the 18. The plug gap would be wider, to take advantage of the higher voltage. Which would result in a fatter spark. But alas the gap is the same. Can you bump power with a jump in timing. You bet! But at what expense? Once again all three engines have the same compression ratio. You go and bump up the timing, you need to run a higher octane fuel. All three of these engines call for 87 octane fuel. And to make a horsepower jump from 18 to 22 with timing alone, you won't be doing it on 92 octane fuel. You'll have some severe detonation problems.

So again I'm sick of being fed nonsense by a so called "mechanic". I've probably built more motors than he has, even if they are not small engines. And I believe as you all have told me it is in the carb. Big thumbs up to the lawnsite members! :) I'll be taking a peek at my carb this weekend.
Click to expand...
The flywheel does in fact play a factor. The keyway is in a different location to advance the timing a lil bit. Also the 18 HP Commands have a throttle stop limiting the butterfly from opening to 100%.
 
#19 ·
jason2 said:
I have a 18 hp Kohler Command. I noticed it has the same bore and stroke, and compression ratio as the Command 20 and 22 engines. This leads me to believe that they are the same engines. Where does Kohler get the extra ponies on the 20 and 22 models? Is it with the carb? I doubt it's in the cam.

Somebody mentioned something about moving the trottle plate on a small engine to get more hp. Is this all that is involved in bumping the output on my 18?

And when they say the throttle plate are they referring to the "butterfly valve"? If so, does the throttle plate have a limiting screw or something to limit it from opening all the way at full throttle?

I know it's gotta be something simple. But I don't know what the differences are between the three engines. And I'd like to make my Command 18 into a Command 22. All three engines make their peak power at the same RPM. So it can't be govenor related. Displacement is the same, plus they all have similar idle characteristics so it's gotta be in the carb. Please help. I'm tempted to buy the new Honda 24 hp, but first I want to try bumping the power up on the engine I already
Click to expand...
 
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