Boost source? Options

[bob91403]

Could someone tell me why this wouldn't work? This unit gives 7lbs of thrust. If you could flip a switch and go from NA to an extra 7lbs of air pressure, would a fuel injection system be able to adjust by itself?

[ArtechnikA]

'a' fuel injection system can. a few can. CIS mostly just cares about total airflow. a MAF system pretty much just cares about airflow and isn't as tuned to the engine's operating characteristics.

L-Jet might be, in theory, but it's calibrated (standard) to match full air flow metering with WOT full load. D-Jet won't have a clue about boost, it just measures manifold vacuum.

the MegaSquirt and other programmable EFI's can manage boost, go read airsix's recent account of his new 1,7 turbo with programmable EFI.

"7 lbs thrust" - that's the force of 7 lbs, yes? what's that in psi, at compressor stall ?

i'm staying out of the eRam discussions. all this stuff CAN work in theory.

show us the dyno numbers at the end of development and we'll be convinced. until then, not...

[lapuwali]

7lbs of thrust does not equal 7psi of additional air pressure.

The problem here is one of volume. What you're essentially trying to do to get 7psi of boost is push 50% more air into a space than would normally be there. A 1.7 consumes 1.7 liters of air per cycle. At 5000rpm, that's over 4000 liters per minute, or about 230 cfm. 50% more would be 350 cfm. To pump that much air that fast requires a significant amount of power, on the order of 3hp if you could do so with 100% efficiency. You can't, of course, so it will always take more power because of pumping losses. Figure 70-80% efficiency for the very best air pumps. Those model airplane engines driving those (not very efficient looking) fans probably generate, what, 0.25hp? 0.5hp? It's impressive for their small size, but it's still a fraction of what's required. If you drove a good fan with, say, a decent lawnmower engine, you could provide a reasonable amount of boost. Or you could just use a turbocharger and recover otherwise lost power from the exhaust stream.

[ArtechnikA]

... A 1.7 consumes 1.7 liters of air per cycle.

must have one o' them 2-stroke 1,7's...

the rest of the math looks okay :-)

[Sammy]

That thing will prolly produce about 1 psi max of actual intake manifold boost at full throttle. Axial fans are designed to produce a great deal of flow but stall easily when up against backpressure. that is why real compressors (for turbos and superchargers) are designed to be either very high speed centrifugal or positive displacement.
Yes, the stock D-jet fuel injection can handle that small amount assuming it is tuned correctly and functioning as designed. You may or may not be able to tell if there is any horsepower increase by seat of the pants. It will be a very, very small gain.
If you could get it to produce 4 psi of boost in the intake manifold you would be getting close the threshold of what the stock fuel injection can handle without modifications.

[Red-Beard]

Axial fans are designed to produce a great deal of flow but stall easily when up against backpressure.

Which is why axial flow compressors are staged. Even early jet engines used centrifigual comressors (well, the Brits & US did).

It is very possible to do an electric supercharger on these cars, but you have to have a motor capable of driving 3-5hp compressor and the current (30-50amps).

It's funny, I actually like the idea of the auxilury Briggs and stratton compressor combo....

Call me crazy...

[lapuwali]

must have one o' them 2-stroke 1,7's...

I said per cycle, not per revolution...two revolutions and all four cylinders will have done one intake stroke. At 5000 rpm, there are 2500 intake strokes per minute, or 4000 liters of air per minute for a 1.7.

While we're correcting each other, 3-5hp is 300-500 amps at 12 volts, not 30-50. You'd need to run 120v power to only use 30-50 amps. Running at 12v would be pretty impractical, so I'd use 24 or even 48v motors, and run 2-4 normal batteries, just to keep the cable size reasonable. Normal starter motor cabling should suffice then.

The best use I've seen of an onboard "extra" small engine is on an AX car that used it to drive a fan, not to boost power for the engine, but to draw the air out of a rubber, nylon, and steel skirt in the center of the car. Yes, a sucker car. Was only allowed for one season before someone updated the AX rules to outlaw "movable aerodynamic devices". It was scary fast that one season, though.

[ArtechnikA]

While we're correcting each other, 3-5hp is 300-500 amps at 12 volts, not 30-50.

you may be correcting someone, but i don't think the 30-50A number is from me. i recall posting an estimated HP number but not A...

your clarification on cycles vs revs is noted :-) ...

[bondo]

The best use I've seen of an onboard "extra" small engine is on an AX car that used it to drive a fan, not to boost power for the engine, but to draw the air out of a rubber, nylon, and steel skirt in the center of the car. Yes, a sucker car. Was only allowed for one season before someone updated the AX rules to outlaw "movable aerodynamic devices". It was scary fast that one season, though.

That is the coolest thing I've heard of in a loooong time. (IMG:style_emoticons/default/happy11.gif)