Engine tuning for effiency

[alexanderfoti]

Hi all

The bike has been dropped off at the exhaust place for them to make a custom manifold. Once done it will be ready to go back on the road.

Am hoping for 100+ MPG, as the dying D850 used to give an average of 88mpg (high of 93, worst of 67).

I already have an electric water pump, but the rest of the cooling system is standard. Are there any mods I can do to the IDI diesel to increase fuel economy on the engine side of things?

Thinking about possibly using an electric water pump controller and removing the thermostat but not sure the gains it gives outweighs the complexity.

[pietenpol2002]

Just a reminder that that "A" series (agricultural) D750 version of your engine was used in tractors as a purely thermosiphon cooling system sans water pump. The dynamo was fitted in lieu of the water pump as below. Given that history, could you go that route?

[alexanderfoti]

Hmm interesting, would be worth a little bit of electrical system load which would be worth a few %

Would a turbo installed without additional fuel give increased efficiency?

[John]

A turbo without increasing the fuelling accordingly would probably clean up exhaust emissions, but only if your current set up is over fuelling the engine already. If that is the case (any black or grey smoke coming out the back?) then you may also gain a marginal power increase too. But I wonder about your gearing and/or cvt set up if you are only getting 88 mpg maximum. Even the 350 & 500 Enfield petrol engines can exceed that with a gentle hand. I vaguely remember the Kubota diesel triples as being indirect injection engines, which decreases efficiency a little, but only 88 mpg isn't good. Is your engine rated at 26 hp? I used to drive large ride on Kubota triple powered rotary mowers for High Wycombe county council, with, I think, the same engine, & I remember them being extremely fuel efficient even when being run at full revs 8 hours a day. Do you think you may be under geared or over geared relative to your engine rating? Or are you perhaps a press on type & heavy handed? Or is it the CVT set up wasting power? I would've expected at least 120 mpg. 60 mph, or even 50 mph @ 3000 should give superb mpg from an engine of that type I would have thought.

[alexanderfoti]

Hi John, thanks for the input.

Its a D722 3 pot, rated at 17hp ish.

My fuel screw is tuned just right, with a light haze at full throttle.

Like you, I am surprised at the low ish numbers. I used to get 120mpg on my 400 yanclone at full throttle everywhere.

You are right on the gearing side, see my other thread, but that should be sorted now. I was at 2500 rpm at 65mph and was always in full throttle to do this, resulting in the governor always trying to catch up. My CVT was only halfway through shifting even at higher speeds.

I haven't done any appreciable miles since limiting the max ratio on the CVT but it will be interesting to see whether this bumps up the MPG. I have also added an oil to water cooler to try and bump the oil temperature up. In the winter it doesn't exceed 40 deg c which is low!

I am convinced that getting the engine coolant and oil warm will be a good way to increase efficiency. I have also advanced the injection timing slightly.