How to add spark advance to 20hp Kohler twin?

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  #1  
Old 02-14-08, 04:10 PM
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How to add spark advance to 20hp Kohler twin?

I'm not satisfied with the performance & economy of my TORO 520xi engine. I think part of the problem is, there is absolutely no active spark advance mechanism. The fuel injected version of the engine does much better, but a complete conversion may be impractical. I'd like to try an ignition upgrade on this one, if there is a way to do it?

thanks,
Bruce
 
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  #2  
Old 02-14-08, 05:07 PM
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To put Kohler's S.A.M. module on your engine, would require the module, new coils, and a new flywheel, so it
would be cost prohibitive.
Most people want it taken off instead.

Fish
 
  #3  
Old 02-14-08, 06:26 PM
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I think you will agree with Fish, With the needed wire harness kit you are looking at $402.00 without tax and shipping. Most shops won't stock the flywheel or harness kit so will need to order it.
 
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Old 02-20-08, 04:08 PM
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Kohler S. A. M.

Originally Posted by Fisher40037 View Post
To put Kohler's S.A.M. module on your engine, would require the module, new coils, and a new flywheel, so it
would be cost prohibitive.
Most people want it taken off instead.

Fish
Please enlighten me on what a KOHLER S.A.M. module is?
I can easily enough set up a coil and module (for each cylinder) from a GM HEI (for free), if I can get the correctly timed spark time signal. What are the benefits?

Bruce
 
  #5  
Old 02-20-08, 05:41 PM
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Spark Advance Module or SAM for short.
 
  #6  
Old 02-20-08, 09:08 PM
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GM high energy ignition on a lawnmower engine? That's like trying to put airplane parts on your washing machine. The system isn't compatable, doesn't work on the same principles, and would be an engineering feat to accomplish for no benefit at all. GM HEI systems have the spark advance in the distributor, not the coil or module unless it's the later version module, which is not reliable and usually hinders performace rather than helping it when used in it's proper application. The advance system works on engine rpm, and your lawnmower engine won't be operating at the same rpms as a chevy engine anyway.

Why are you thinking you need timing advance? This shouldn't affect the way your engine runs expect possibly a little during acceleration from idle. That's it. If you have problems during normal running, then it's something else.
 
  #7  
Old 02-21-08, 12:38 PM
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Kohler Spark Advance

cheese, I will attempt to answer all questions. Please enlighten me on the KOHLER S.A.M. module. I don't know much about small engines, and would rather not waste time re inventing the wheel. However, I did convert my 6.6L V8 to sequential port fuel injection; it runs the way my KOHLER should.

When I hit a big load, the engine slows way down. I believe if the spark was optimum for 3600 rpm, it is way off for 1800, so I am losing torque and fuel economy. Also if the governor closes the throttle, the spark needs to be advanced for best fuel economy. KOHLER agrees, they developed a fuel injected version and manage to sell it for $600 extra.

Fish said I would need new coils & flywheel, costly. I aready have plenty of HEI distributors around, I can use a coil + module (free) for each cylinder. I won't be using any of the rotating parts of the HEI. Then I need 2 signals
for the CORRECT time to fire each plug, S.A.M. might do that. Waste fire as before. I should be able to use the orig coils to get base timing, build simple electronics to tie it all together.

You can see what I have to mow/rake/snowblow below, and some project resources:

http://s93.photobucket.com/albums/l71/bcroe/
click an abum upper left corner
that's small "L" 71, not capitol "i" 71

thanks for your input, Bruce
 
  #8  
Old 02-21-08, 04:33 PM
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Bruce,

If you click this link; http://www.kohlerengines.com/service...ls_results.jsp then download the CV730 Service Manual and go to section 8 page 6 it will fully explain the operation of the SAM module.

This way nothing gets left out in translation....
 
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Old 02-21-08, 09:17 PM
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If you were to make the hei coil and module work for each cylinder, it would be no different than the original kohler coil that was intended for use. There is no advance involved in the GM modules. It's basically switching transistors to ground the coil as it picks up readings from the distributor pickup (in lieu of contact points).

I think you're putting too much stock in the theory of spark advance in the first place, and maybe blaming other problems on the engine's lack of advance. Any benefit of spark advance is almost negligible on a small engine, and if you could notice it, it would only be during the transition from a low speed to a high speed, and then probably only under a load. On a GM hei system, the timing will actually retard instead of advance, when the throttle is dumped. The vacuum advance motor in the distributor does this. The flywheights under the rotor further manipulate the timing from there. It's a good mechanical system, but the application and principles of operation are way off for a small engine. The SAM module on a kohler does not provide advance either. It retards the timing at certain times. Most of the time, it provides the same base timing that an engine without it has. I will say I can see little to no performance difference between the engines equipped with it versus the ones without.

Note: The GM hei coils are standard coils that develop a magnetic field that collapses through secondary windings around a core when the 12 volt current to it is applied to ground. This is totally dependent on the 12 volts and a switched ground. The coils on the kohler don't rely on any outside voltage. They will work with no battery. They are charged by induction/the passing of a magnetic field across the armature legs. This passing magnet is in the flywheel, and is what times the ignition as well. The switching electronics are in the coils on non-SAM kohlers. The switching occurrs in the SAM on SAM equipped engines, but it still relies on the signal from the flywheel activated coil to provide the signal to switch, and the current needed for the spark. A GM coil would have to be fed a power source, have some sort of way to attatch a plug wire (since the HEI coils are mounted inside the cap with no coil wire), a way for it to be grounded at the appropriate time (timing)...which would involve a bit of semi-conductor circuitry engineering (a GM module isn't going to work in this case...it is intended to react to the signal from the distributor pickup, not the strong AC signal created by a kohler coil), and then some fashioned way to mount it all. If you managed to accomplish all that, you'd still not have advance and you'd have a seriously over-complicated ignition system that performs no better than the original.

Ah...I got more into that than I intended to. Just trying to help you see the hows and whys about why this is not practical. I think you have a problem that needs repair, not inventing. These engines were made to perform in the applications where they are installed. Kohler especially.
 
  #10  
Old 02-22-08, 12:29 PM
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Add Spark Advance to 20 hp Kohler

Thanks 31YTech for the direction. The SAM description is a little sketchy, but it seems to add a linear advance per rpm, without regard to MAP or throttle position. I could build the same thing myself with a better interface to my other parts.

Is advance worth anything? Your questions are encouraging me to make a real plan. I would like to use an advance curve that maximizes torque at any MAP and rpm. Without a dyno, the abiity of the engine to accelerate can still be used (engage the mower for more inertia?).

If a signal is picked off a plug, I can measure the time for one revolution. From that I can get rpm. If the engine is accelerated from idle to 3800 rpm, a computer can record the time for each consecutive revolution. Since the engine is speeding up, each time will be shorter than the previous, or at least each pair. Subtracting the latest time from the previous (derivative) gives the acceleration for that rpm. I could record a run for 15 degrees advance, then another for 20 degrees, etc. etc. I might find that the highest acceleration at 1800 rpm was with with 15 deg advance, but the highest at 2400 was 20 deg, and 3600 was 30 deg. From this I can find the best curve at every rpm, for one throttle or MAP setting. Here we can see if there is little gain as cheese said, end of project. Or see significant improvement. This has been done before on another project.

There is still the MAP variable, so more curves need to be run. Then build a circuit to generate the proper advance vs rpm and MAP.

The Kohler modules can't give me any any advance, but they CAN give a base reference timing. From there I add my curve, and feed it into the HEI circuits. The HEI has no advance either, but it converts my logic signal to plug power, and it does manage the coil dwell.

There ought to be a lull after snow ends, to start this. I don't intend to mess with the internals of a good near new engine, but a timing scale and external ign can be done.

The Kohler may running exactly as they intended, but that's not good enough for me. Kohler thought the SAM and EFI
were worth doing, so I expect to see improvement. The EFI was able to raise compression from 8.5 to 9 due to better management. I won't do that, but might put on headers to get nearly the same result. Mowing 4 acres with lots of hills and obstacles, I am constantly changing speed & load, and the performance is a fustration to me. I always raceto improve my time, but its very annoying to run out of gas before the race is over. The twin uses gas on a par with my 2 ton 403 Olds at high speed. I have built wide band air/fuel ratio meters for my cars, both carb and EFI (see PHOTOBUCKET). Later I might use this to check the carb, not sure what happens after that. I'll post some pictures if I get this off the ground. Numbers at the end.

Practical, well I'll be the judge. Nothing aound here escapes some modifications, as seen in the pictures. I already had to build a weight box to snap into the rear of the Toro, for snow blowing. This in addition to chains and wheel weights. Bruce
 
  #11  
Old 02-22-08, 12:52 PM
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Go for it. Maybe you know something all the small engine engineers of the past didn't know. That's how inventions are made. Personally, I think it will end up being a colossal waste of time, but don't take that personally. I'm just answering the original question with a logical answer. There is no ready-made or simple to adapt spark advance system like you're looking for; for this engine.
 
  #12  
Old 02-22-08, 03:31 PM
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Hmmm,

All I can say is..... Good Luck
 
  #13  
Old 07-24-08, 11:10 PM
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ADD Spark Advance & auto choke to 20 hp Kohler

Spring was hectic, but I got started. Manifold vacuum & rpm are needed to compute advance, so I decided to put gauges on them. No taps on the intake manifold, would have to pull the engine to get the shroud off and the manifold. Instead I drilled a hole through the very thick carb gasket, and glued in a fine tube. I noted bosses for fuel injectors, later. I have some from the motorcycle EBAY.

An ignition signal is needed from the flywheel driven modules. I could use an inductive plug pickup (stolen from a timing light), found a nice 200V pulse there. However I also checked the KILL wire connected to both modules, and found a nice 30V pulse for each of the (odd fire) cylinders. With a little bit of electronic conditioning, I had a 4000 rpm tach.

The gauges got me started on what the engine was doing. The odd fire wouldn't do much more than 15 inches of vacuum at idle, 5 inches at moderate load, and zero for heavy load. The tach idled at 1500 rpm, and hit max at 3800 rpm, losing a little with load. I found a very heavy load was best delt with by slowing the tractor motion enough to maintain 3000 rpm. Lower rpm risked stalling and didn't get much done.

There is enough info here to drive a spark advance system. I could time a revolution to get rpm, then modify output drive timing on the next revolution. The original modules would supply a fixed reference, which I would retime before sending to the new ignition. Waste fire every revolution as before, so no cam sensor needed. Or I could put a magnetic pickup on the ring gear teeth for better accuracy, may not be needed.

The MANUAL choke on this engine has annoyed both drivers, I'd like to get rid of it. With an oil temperature sensor already in place, it just boils down to a way to physically drive the choke plate. later, Bruce Roe
 
  #14  
Old 04-23-10, 09:51 PM
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Adding programmed spark advance to 20 hp kohler

OK, it took a while. Research showed I could use a cheap Fo*rd V8 EDIS system to convert my 20 hp Kohler odd fire to electronic ignition. Adding a module from AUTOSPO*T LAB*S gave me a user friendly PC access to program any vacuum/rpm/temperature ignition advance curve; parts only around $200. The original fixed advance flywheel ignition is still there for backup.

Starting with idle at 1500 rpm, increasing no load advance increased speed to 2000 rpm. Backing the idle screw to 1500 rpm is sure to save gas. Now the engine could idle at 1000 rpm instead of stalling below 1500. Improving advance at no load/full throttle raised rpm from 3600 to 4000 despite correction from the governor. Full load was also calibrated.

Now the engine starts so much better (extra retard for cranking). It accelerates better. When a heavy load (tall grass) slows it down, it keeps on pulling instead of stalling. For the first time, I felt like I had to hold the tractor back, instead of always pushing harder.

But the final improvement: I didn't run out of gas mowing the 4 acres. Instead, there was some 1/4 tank left. I'll have to measure the gas to get better #s, gas gauge is inaccurate.

Pictures, go to ALBUM "Crank Trigger Ignition" at my PHOTOBUCKET site
Pictures by bcroe - Photobucket

(that is a lower case "L"71, not an upper case "i"71)

click on an ALBUM
click on a picture to enlarge + description

Bruce Roe
 
  #15  
Old 04-24-10, 01:36 AM
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Looks like you did it. Much better/practical than the GM HEI distributor idea.

You might consider the tendencies that particular engine has so that it doesn't get damaged by timing issues such as pre-detonation or excessive heat buildup. These engines drop valve seats and/or blow head gaskets when the head temps rise far enough.

Nice work.
 
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Old 04-24-10, 07:43 AM
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Wow! Sounds impressive, although it's too far over my pathetic level of skill to really appreciate.

Most DIYers have very marginal levels of skill and experience. But every once in a while you find one with the drive to really do a blow out job on some project, and this sounds like one of 'em.

Bruce, may I ask about your technical background and experience?
 
  #17  
Old 04-24-10, 10:40 AM
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Add programmed spark advance to 20hp Kohler twin

The Kohler has a temperature gauge; with 8.5:1 compression, hope that is enough. I would hope it actually runs a bit cooler, since the fuel used is reduced; higher efficiency.

The most difficult part of this project, was fitting the provided trigger wheel onto the crankshaft. Other than removing the PTO clutch, the engine was left alone. All the design was done by For*d & AutoSpor*t, I just bolted & wired pieces together. There is a lot of info on line, ask questions on the forum. Yes the software supplied to me did have some bugs. You can read about my work arounds on the AS forum.

Background, like to make things. Spent 41 year as an EE at Bell Telephone Labs. Bruce Roe
 
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Old 04-24-10, 11:47 AM
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Originally Posted by bcroe View Post
Spent 41 year as an EE at Bell Telephone Labs. Bruce Roe


That'll do it.


I have a cousin who got an engineering job straight out of college with IBM with an EE degree --- later got a Masters.

He worked mostly as an engineer for IBM from '62 to 2002, at which point IBM fired him and offered him a job as a contract employee doing his same job for lower pay.
 
  #19  
Old 12-14-10, 09:42 PM
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One Year of Enhanced Tractor

After a whole season of mowing, a couple days raking leaves, and some snow blowing, here is an 80 hour operating update. Joan took a shift mowing, she says "Its a lot faster!". The ability to idle so much more slowly, then accelerate with no hesitation is a joy. The gas I'm saving is going to pay for the ignition changes in a couple years. Raking leaves at minimum speed, the Toro was able to do real work at 1200 rpm; previously it would stall below 1500. I change speed largely with the throttle instead of the hydrostatic, no more screaming engine. A minimum time is spent snow blowing 1/10 mile of driveway. Not much different, maybe a bit more low end torque. Finally, there is no longer a big BANG on shutdown. Bruce Roe
 
  #20  
Old 12-15-10, 04:41 PM
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So now all you have to do is build and market your kit!

Steve
 
  #21  
Old 04-26-12, 03:58 PM
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Starting an engine with crank trigger ignition and full advanced ignition timing

With crank trigger ignition, and without a way for the engine to retard and advance the ignition timing automatically, the timing will need to be set advanced permanently, and install two separate electric switches - one being a push button to crank the engine with a gear starter, and the other being an ordinary OFF/ON toggle switch to power the ignition. To make this work, first crank the engine to get it spinning over, choke it and then flip the ignition switch to "put the spark to it." Doing this will allow it to start every time. Because the spinning weight of the heavy flywheel makes it impossible for it to momentarily kick back against the full compression with advanced spark.
 
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