I just want to be different or is that difficult. I want to mount my supercharger at the front of
the motor away from the hot exhaust and i also want to run an intercooler and use my dellorto
I'm not expecting to fit it all up and have it working in one day. Its more like an experiment
i want to test if it can be done

i wasnt knocking the idea, it looks a lot easier to set up and considering there is more room at the front of the engine, go figure,

the pic i was talking about was the one awdmoke posted, what does that intercooler do with that air, it looks like air flow through that thing

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Another advantege to hanging the S/C at the front of the motor is that it's physically easier - no manifolds to build or modify.

The intercooler is just an air to air radiator. . . .the S/C compresses and heats up the air, the intercooler cools it down a bit before it hits the carb.

i thought so, ive never seen a intercooler being used in this way though,

hee bee gee bees, ive got an intercooler that looks similar to that, mate wrote off a ......... what ever it was i got a use for that thing now,

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An intercooler will always go after the compressor (be it supercharger or turbo) and before the fuel source (carb or injection). You're only ever cooling air, not air and fuel. . .otherwise (as DOZ mentioned) fuel tends to pool in the intercooler core. . .one backfire and you get to test out your insurance company.

The intercooler off my Moke is off an S13 Silvia. . pretty weeny on a Silvia but plenty big enough on a Moke.

Why does a large plenum increase performance (I have Maximum Boost around the place somewhere, I guess I should get it out and read it. . .)?
I would have thought a large open space would just be inviting lag (more volume to fill to the required boost pressure) rather than being of any benefit. . .

i think the idea behind a large plenium is to slow gas speed to allow for even air distribution between ports, so on su i cant seeing it help that much but on dellorto may be of help

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Aaahhh. . .so, really it's of more use on a draw-through setup where the plenum is part of the inlet manifold. . .

Hey Pete,

Its still a blow through setup it goes supercharger -> intercooler -> plenum -> carby -> manifold -> engine.

This is another picture from Jukka Harkola's turbo mini see how the plenum works.
The boost from the turbo goes through the 2" inlet near the clutch master cylinder.
Then through the carby into the donk.



I think the idea behind the plenum is constant pressure. When you give the car a big boot there is a large volume
of compressed air in the plenum so the carb is under constant pressure.
If you didn't have the plenum the blower would probably have trouble supplying the volume of air so quickly.

I think what I'll have to do is read Corky Bell's book.
What you've said above sort of makes sense to me, and it might explain the slightly laggy nature of the S/C setup on my Moke. . .I still would have thought that the large volume of air in the plenum would have made lag worse though, as the motor would be constantly drawing on it while you're off the throttle and the compressor is not supplying boost. . .and then when you give it a bootful, the turbo/supercharger has to re-compress all that extra air before you see boost pressure. . . .but I'm probably wrong!

I think the plenum is like the tank on your air compressor, it's a ready volume of compressed air to go into cylinder. Too big and the blower/turbo don't compress it enough prior to the gulp, too small and hp is lost, hence the basic volume calc based on engine cap.

If you have a lag issue with a blower then your drive ratio maybe is incorrect as the blower volume flow rate is fixed for a given rpm (assuming a blow through roots style blower). It should always be compressing the air in the manifold, even at WOT you should still see boost. Overdrive is required when the flowrate of the blower is equal to/less than the WOT flowrate of the engine at the same rpm.

I have seen problems with plenum volumes that are too small on both NA and turbocharged EFI engines. You have cylinder robbing issues on a 5 port mini engine, you get the same effect on an 8-port (or 16V, whatever) when the plenum is too small.

You can get more power if tuned (plenum volume and runner length) correctly, this is hard to achieve on a mini due to the space.

Daniel

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