Command V-twin Turbo

[karl]

I planned on doing a big bore single , but I found a much better donor.

The bottom end is a CH640 Kohler Command

38ci (624cc)

3.03 bore x 2.64 stroke

8.5 :1 compression ratio

Rated 20hp @ 3600 rpm , 32.6 ft/lbs @ 2600

Pressure lube (very handy for a turbo), electric start and charge.

It is in very nice condition, crank, rods, bore all looks good. Unknown hours. It is worthy of a set of billet rods.

Lots of parts available for pulling tractors.

https://mwsc.co/collections/kohler-command-engine-parts

Should have no issues spooling a rhb31

I only have the bottom end, so I will be using 24hp Courage heads
Because they were free, And I think the valves and combustion chamber are slightly bigger. Custom pushrods are in order.

Anyway It will be a slow build, as parts are not cheap. And I want to make it legit as possible.

 

[karl]

The first of many baths

Got rid of that pesky governor rod, we wont be needing that.

Good to know the rods are on REV C lol at least I wont be using them.

And the flywheel part number has been superseded 5 times, something to think about.

Crank looks good.

If anyone wants to know what these engines can do check this out

https://www.youtube.com/watch?v=TC8yYTXoZm4

 

[karl]

I got the heads de-sludged

Still needs lots of scrubbing.

Here is what it looks like with the heads.

One good thing about using courage heads , lash adjusters. The command uses hydraulic automotive style lifters vs the courage solid. Command heads have no adjustment. So I can compensate for different headgaskets or any other variables.

 

[65ShelbyClone]

Less scrubbing, more boosting.

 

[anickode]

Less scrubbing, more boosting.

If you're gonna go big, take the time to do it right.

 

[karl]

Soon. I am getting the flanges for the manifolds plasma cut this weekend.

The copper head gaskets are in the works, I need to wait a week or two for the rods.

But I can fabricate the manifolds and check pushrod length when I get the gaskets.

 

[65ShelbyClone]

If you're gonna go big more than once, take the time to do it right.

FTFY.

I was only kidding. I clean everything as soon as I get it too.

 

[karl]

I decided to make my own gaskets out of .030 copper sheet

I also will lap the heads and block flat on my stone slab.

No gasket is needed (but high compression is not the goal) , or any silicone or sprays.

 

[65ShelbyClone]

I don't know what you're going to do for tuning, but I'd suggest using the stock composition gaskets at least initially. Head gaskets are IMO the best weak link to have because they're inexpensive and easily replaced. The copper won't give if the engine leans out and/or detonates. Billet rods means that the cast pistons will be the new weak link.

 

[Kartorbust]

Hopefully this goes well. Running carb(s) or fuel injection?

 

[karl]

I will be using a Walbro EEM fuel injection system.

It is a self contained unit with the injector, fuel rail, throttle body, TPS, and ECU all in one.

Oxygen sensor and temperature sensor are the only external components.

I am aware of the risks of turbocharging an engine, and even with EFI its not immune to knocking.

 

[karl]

I decided against the EEM unit, its an easy solution, but very limited tuning and bore size.

That is where a much more substantial 48mm throttle body setup intended for a 700cc single UTV engine comes in.

The throttle body is cable operated, with TPS and IACV

The Fuel injector and MAP sensors will need to be built into a custom manifold, still unsure if I should try and run one injector, or two at the ports (probably a better idea)

 

[65ShelbyClone]

Either injector layout will work, although having port injectors will likely offer better response. A single upstream injector will need more acceleration enrichment due to wall wetting.

 

[karl]

I want to hear this thing spool!

 

[65ShelbyClone]

So do I.

The upward-angled turbo reminds me of hot Subaru setups.

 

[Mower Maniac]

Billet rods are a good idea, as well as forged pistons, stiff springs, stainless valves, bronze guides, better retainers, chromoly pushrods, stud mount rockers, bigger cam and port out those stock ch642 heads. Higher compression will help spool, and the porting will allow you to make more power without having to boost the crap out of it. Also, billet flywheel... You can get everything on Midwest super cub

 

[karl]

I have had a lot of other stuff going on, I finally got some time to mess with the kohler. I know I said custom efi, but got my hands on an EEM unit , so I think Ill start with that

I could not run it very long as neighbors trying to sleep and such

 

[Kartorbust]

At least it runs . How much of a pain is it going to be to tune it properly? I know Carsandcameras had a tough time tuning the turbo drift trike all those years ago with the EFI kit.

 

[karl]

At least it runs . How much of a pain is it going to be to tune it properly? I know Carsandcameras had a tough time tuning the turbo drift trike all those years ago with the EFI kit.

Should not be too bad, I can use the dealership link cable and software to adjust some, and sensor manipulation

Properly is a subjective term

Ecotrons is a completly diffrent system, and they seem to struggle with alot of stuff , even with ridiculous budgets and time