Hi! I have a question; I am building a small 200cc 4stroke DOHC engine with draw through turbo (carb direct on intake Turbo). Now I want to use a vacuum fuel pump, which should normally be mounted to the intake manifold.

My question is now; does this work in combination with a turbo? Because there is no specific vacuum, but a compressed mixture with steeples build up pressure? Am i correct? Or can I mount a vacuum port between the carb and the turbo for example instead of between the turbo and the engine head?

Cant figure out by search, maybe i missed something because english is not my native language, please keep in mind when answering

Looking forward to good information on this matter

Kind regards, Gilles
Amsterdam, Holland

 

i wouldn't think a vacuum fuel pump would work one you go into boost you have pressure in the manifold not vacuum

 

Hoi Gilles. In a draw-through application, you will still have vacuum between the inlet of the turbo and the carburator. In a boost situation you will, however, be drawing through more air (and fuel) than you normally would if the motor was naturally aspirated. The only questions really are:
1. Can the fuel pump supply the extra needed fuel? As you will be pumping more air, thus needing more fuel too.
2. Suddenly closing the throttle blade while under boost will create more vacuum than you normally would have. Can the fuel pump handle this?

Groeten.

 

Hi Alain,

Thx for your answer!Thats interesting! A vacuum pump works on vacuum pulses, will the turbo flatten these pulses into a constant vacuum level? Because in that case it will still not work.

I could build an air pressure regulator between the pump and the manifold of the carb, would that be an option?

I am quite new on this engine matters.

Thx in advance and groeten terug

 

I run the pump on my minibike off of the crankcase pulses. Not connected to the intake at all. I just had to tune the crankcase vent size to make it work right. No idea if it will work with boost.