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Discussion Starter #1
I am not a mecanic and am learning about alot of things trying to keep my alfa on the road. Thus this may seen like a very stupid question but please feel free to set me straight

I have been reading alot about alfa engines and how engines work in general as part of my education about all things automotive. I have a 79 alfetta sedan with Spica and the air pump system. Stock except for Motronic pistons. I have read about the drain on the engine that the air pump uses and the pros and cons of removing/disabling the system. I have disabled mine and while I did not notice a great power improvement it did make the engine alot quieter.

In my reading I have discovered forced injection (turbos/supercharging) and learned that basically they are air pumps that force air into the intake side of the engine and with extra fuel devivery can greatly increase power. That got me thinking as to what type of flow the stock air pump puts out and what if instead of sending that air to the exhaust you instead were able to get that air into the intake side. With that a couple of questions:

1) what type of volume or air does the air pump put out?
2) how does this compare to superchargers/turbos (I would think alot less)?
3) to get any type of benefit I would assume that the intake system would have to be presserized or any forced air could be forced out of the air box. Correct?? if so is there any type of one way air flow valve that could be installed in the intake system to accomplish this?
4) given the presumably low air flow would there be any benefit of trying this or would the draw on the engine to run the air pump outweigh or equal any power increase?
5) would this need any modifications to the spica pump?
6) any other comments or sugestions I should consider?

Thanks in advance.

Leonard

79 Alfetta Sedan
 

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hmm, interesting but i think the problem would be that with a turbo/super charged engine, all of the air going into the engine must be under pressure. otherwise, it just won't flow correctly and will escape out the intake. therefore, you would need to run all the intake air through the air pump which just isn't possible. that's why super/turbos are much larger in size and with a much larger input/output. i think you were thinking of adding the air pump flow halfway through the intake track to add pressure & flow but it just won't work that way since the pressure would go anywhere that there is less pressure and that would mean backwards.

but it is interesting in considering the possibility of running a much smaller pump and plenum with much higher pressures. i guess it's just easier to do it the traditional way.
 

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Discussion Starter #3 (Edited)
hmm, interesting but i think the problem would be that with a turbo/super charged engine, all of the air going into the engine must be under pressure. otherwise, it just won't flow correctly and will escape out the intake. therefore, you would need to run all the intake air through the air pump which just isn't possible. that's why super/turbos are much larger in size and with a much larger input/output. i think you were thinking of adding the air pump flow halfway through the intake track to add pressure & flow but it just won't work that way since the pressure would go anywhere that there is less pressure and that would mean backwards.

but it is interesting in considering the possibility of running a much smaller pump and plenum with much higher pressures. i guess it's just easier to do it the traditional way.
Thanks for the input - that is what I was thinking in question #3 above. Do you know how this is done in a "normal" supercharger/turbo? I would assume there is a regular freshair intake that passes some type of one way valve to have the engine run before the turbo spools up and then after that one way valve the turbo adds its forced air. With a superchager this seems more straightforward in that the supercharger is inline with the fresh air intake and thus that "obstruction" would stop the pressurized air from flowing out the air intake plumbing.

I guess the question then beomes what amount of air does the engine use at any given RPM point (a) v. how much air does the air pump put out at those same points (b). If (a) is less than (b) then in theory the engine should make more power disregarding the power loss to run the pump. Since I believe the air pump uses 3-5hp (about 2-4% of engine hp) in reality the air pump would have to put out at least 2-4% more air than normal.

Thanks again - this is more of an academic exercise for me to see if I am understanding the workings of an engine

Leonard
 

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well, there is no one way type valve. the system is simply pressurized from the compressor onwards. and you can see from the size of the standard intake manifolds that an engine does consume a good amount of air. also, the pressures used in turbos are not very high at all but i think this does have much to do with the fact previously stated in that the intake is a fairly large channel. i'm not an engineer so i can't tell you the equation for increased flow from pressure in relationship to cross section but it's quite obvious it's important. pressures in turbo applications range from 5 to 20 psi generally but depend on whether the car is a sports car or just a small engine trying to make some extra power. my porsche 944 turbo uses 11 psi stock and i have gone to 14 for a very noticeable increase in power. i think for each extra pound of pressure you gain about 10-15 hp but that's all subject to other factors of course. the guys making the big power with 951's are usually only around 18-22 for hp's up to 500, but they've done other work also.
 

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also, have a look at wikipedia or something about turbos. you can learn a lot just by looking at how it's arranged and flows and all that which words are inefficient in conveying.

it's really a quite ingenious design. wish i'd thought of it!
 
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