simple turbo?

[Anonymous]

I was just wondering about something. The goal of any head porting/induction system is to optimize volumetric efficiency, right? In a perfect system that would be 100% or possibly slightly higher with some benefits from scavenging. This is the benifit with supercharger and such, they force more than 100% into the comb. chamber. What if a small electric fan was placed somewhere in the intake system. Like in the duct of an early IFE system or of a cold intake. It wouldn't have much preassure but would it offer any benifit. It would have the same effect as a ram air but at any speed. Or could this be placed in the duct of a ram air and gain more boost? Is any of this making sense? Am I wrong in my theory? I just thought it was an interesting idea?
Paul

 

[xctasy]

The way to raise a 65 to 75 %volumetic efficiency engine is to do outside the engine what is noramlly done inside a 100 VE engine.

The way the Swiss did it was to add a positive displacement booster out side the engine. This boosts VE all the time.

If you go to a turbo, it isn't a VE boost at all periods, so it has a slingshot effect.

Both systems are externat ducting systems, which will produce the same boosts at full revs. They are more like external gasturbine engines than fans. It does this only by admistering a set augumeted amount of extra air. When fuel is added by a richer carb or EFI, then power is the result.

Now, the physics. The aim is to gain the effective power and torque of a 100 %VE engine that revs to 5000 rpm, but using the garden vairioety 200 I6. It's just a 70% VE engine at best.

CFM for a 70 % VE engine at 4000 rpm is 162 cfm total.

The 100% VE engine at 4000 rpm needs 231 cfm. You have to creat a sealed pump which flows 231 cfm of flow, at about 1.4 times the normal atmospheric presure. That would give another 30 hp or so straight up. Electirc fans a re only 50% efficient at best, while an engine is only 25% efficient. In order to get 30 hp of charge boost, you'll need to provide 60 hp worth of electicty.

A fan won't ever do that unless it consumes about 60 hp worth of battery power. The engine would then have to provide this.

A supercahrger uses about 20% of the engines flywheel power to give a 40% boost. A turbo uses about 10% of wasted exhast energy to produce about 40% of boost.

Turbos, superchargers are more efficient.

 

[Anonymous]

I think if you search E-bay, you will find the type of setup you describe. A cheap electric fan marketed as a supercharger. I had a mechanical engineering friend that rigged a vacuum cleaner blower to a Briggs & Stratton Engine. I tend to think a little fan would probably impede airflow on a car.