Last year I built a diesel motorcycle using a Yanmar L100 single cylinder 418cc diesel engine out off a 7k watt generator. I have included a picture of it to prove that it is not a rat bike used for riding around the church parking lot until the cops are called. It will generally do 55mph as long as there's no head wind or hills. The bike would be perfect if it could pull 70-75mph. ..so I decided to try and turbocharge it using a IHI RHB31 turbo. I spent a couple of day hooking up all of the plumbing and I took it out for a test ride. I was greatly disappointed. Instead of the addition of 25% more power it was as if there was 20% less power.

In building it, I used larger exhaust pipe between the exhaust manifold and the turbo intake made a plenum chamber for the intake of about 1200cc's. The exhaust port on the side of the engine is about 1 1/4" and the input to the turbo is about the same size, maybe 26mm. The exhaust pipe between the two was about 1 5/8" I.D. and about 15" long. This was all done to smooth out the pulses. This does not seem to work. The engine revs nicely now but in 5th gear will barely get out of it's own way. I hooked a pressure gauge to the wastegate port and at medium throttle settings it is getting about 2-3psi of boost and at full throttle, high revs it is putting out 7-9psi of boost so basically everything mechanically is working.

The question I am asking:

Where can I go to get information about accurately tuning this thing? It actually runs as if the exhaust is too restricted. I am considering making the length and size of the exhaust between engine and turbo significantly smaller but it already appears to be suffering from weird pressure wave problems. Basically I need help determining the volume of the plumbing, any ideas?

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Are you adding more fuel? Did it produce any fuel smoke before the turbo install? If it had all the air it needed before, adding heated more dense air probably isnt going to add power, without adding fuel.

Pre turbine exhaust volume changes spool characteristics more than anything. General rule of thumb is to use the same tubing dia. you would use if it were n/a.

 

It would need an injection pump that is referenced to boost, so that it can add fuel as the airflow increases.

 

Many of the older diesels did not boost reference (or did, but the rack limiters were disabled), they just smoked a bit more until boost came in. You should be able to make it work either way.

 

I would put some gauges on it and see what the pressure differences are between the boost and back pressure for a start. Like others have said more air needs more fuel to make more power.

Gary