Adding Turbo

[alexanderfoti]

Hi all

Thinking about adding a turbo (for efficiency) to the D722.

Only issue is packaging.

Here are my downpipes:



The only place I can see it going is where the X is:



click images for larger versions.

The specified location poses a few issues.

1. Ground clearance, its the lowest point of the bike.
2. Space for air piping etc is limited.
3. Being below the sump will mean a scavenge pump is needed which seems like its too complicated.

I would be going with an IHI RB31 Clone, which should build lots of boost very low down on this engine. It is also very compact.

Thoughts?

[mark_in_manchester]

I'm using a Daihatsu Charade 993 turbo-diesel. It's built into the exhaust manifold and it's really close to the head - I guess where the exhaust is most energetic. I think that's where you need to be, which means making a new manifold / downpipe and arranging clearance for your front mudguard and radiator.

Before you do, why not rig an inlet plenum, pump up a gas bottle of some kind as hard as you can with air, and fit a regulator which will discharge it into the plenum to keep it at about 10psi over atmospheric at max engine revs. Tie it on the bike and see what happens when you turn it on while riding. You'll know if it's worth all that bother. Mine makes a fair difference - but there's a diaphragm on the injector pump connected to the inlet plenum on mine, so fueling is changing with increased air.

[Tetronator]

Why not stick it to the left or right side of the bike? Like where the waterpump used to be.

[alexanderfoti]

Thanks both.

Yes ideally it would be as close to the head as possible, but it will work further down the exhaust, it will just introduce delay on boost.
There is not enough space to keep clearance underneath the front wheel, its tight there as it is! Its possible that with some very clever exhaust work it could be made to fit right up against the head, but plumbing for intake would be difficult.

It would probably fit up near where the water pump used to be, should be easy for the exhaust work as a log header would keep it in line with the ports on the head. May make the bike too wide though... Would solve the issue of clearange and pump scavenge though.

[alexanderfoti]

Looks like it will go where the old water pump will be.

any thoughts on which turbo is best? Ill probably look at a VZ21 which is a clone of the IHI RB31.



It has a good flow rating for this engine (D722 approx 40CFM) and the ratio is good. It is teeny tiny though! It is also watercooled and oil cooled, which should increase efficiency. I plan to run it at 6psi without an intercooler (there just is no space!), unless I am clever with a water/air intercooler, but then need another pump and res etc .

The fuel screw on the pump should be fine for extra fuel, no boost dependent fuel control unfortunately, so it will smoke off boost.

[mark_in_manchester]

I wonder if you could add a mixture lever, and nudge it back when you're not doing high speed. Mine just slows down when I get to the end of a tank and the fuel line fills up with bubbles, so cutting fuel might be hoped to do the same - rather than run lean and melt your pistons...