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Old 05-07-2008, 03:36 PM   #1 (permalink)
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Conversion idea, 2L inline 4 -> piston boosted 1.0L 2 banger? Warning....Long thread

I had an idea pop into my head a while back and I need someone to help me disprove it, or maybe make it happen, too early to tell yet. Got a few minutes?

What if I took my inline 4 banger (VW 2.0L ABA), modified the cam (double lobes 180 degreees out from one another for 2 of the 4 cylinders, intake and exhaust) so that 2 of the 4 cylinders acted like 2 stroke air pumps (basically just intake and exhaust strokes over and over again), I then pipe the "exhaust" (air only in this case) from these 2 cylinders into the 2 normal cylinders as it's intake air, then just run the 2 normal cylinders with fuel and spark, the other 2 would have no spark and no fuel.

The theory in my head would be that you could "convert" 2 of your "air pumps" into a source of forced induction for the other 2, not crazy boost, but something mild as 2 strokes would be completed for every one intake stroke of the normal cylinders. My idea is to turn my 2.0L 4 banger into a mildly boosted 1.0L 2 cylinder that, you guessed it, would get much better miles per gallon, granted slower than stock, but my goal here is mpg not high hp. Any thoughts on my latest brainstorm? Shoot away.

Some details that I have thought over so far: (in no particular order, sorry)
1: I would take the output of the 2 "air pump" cylinders and pump it through the MAF and into the 2 banger intake, that way the computer would know how much air is being fed into the real cylinders.

2: Depending on how you pipe the output to the input, you could even utilyze a front mount air to air intercooler. Granted you lose some of your boost, but at least it would be cooler air.

3: Another thought would be to run gapless rings in the air pump cylinders (the other ones wouldn't hurt either), so that they are more efficient at pumping air (less loss by the rings) and seeing these 2 cylinders would run much cooler as they are not actually "running" it may help as the parts would not expand much. Could also choose which cylinders to do based on heat too, say the middle 2 that way the outer 2 provide heat to the middle 2, but that would depend on which ones are "stroke pairs" for lack of a better term.

4: C2 motorsports has chips for forced inducted 2.0L engines, they run bigger injectors, and use MAF for air used by the motor. Obviously it would take a "special" program to be able to make decisions based on 2 cylinders only, or maybe it wouldn't I am not sure really.

5: I was reading about the old Geo Metro 1.0L 3 cylinder and it was rated at almost 60mpg. Made me think, do I really need 2 liters or just 1 powerful liter, which led to what do I do with the other liter, make it pump air twice as fast as I need it. Other than any pumping losses, it should increase flow with RPMs much like a supercharger does, so it wouldn't need any BOV or wastegate, well in theory at least.

6: The 2.0L crossflow would be a good platform for it due to the intake manifold being 2 parts and a crossflow head would just make the piping that much easier in my mind and less likely to suffer from heat soak.

7: Keep in mind, the air pump pistons will have the exhaust valves open from BDC all the way to TDC (give or take) to avoid having to compress the air much in the cylinder, so it's not like your opening the exhaust valve up while it's under a lot of pressure, just fill it up with air, then push it out. My theory here is if your running these air pumps at twice the speed (2 stroke sort of) of the regular cylinders, then you would produce less than double your air requirement for the other 2 due to inefficiencies, but more than what those 2 would have pulled in on their own (NA).

8: I highly doubt that it would produce more power, not really the goal of this idea. If everything was 100% efficient, in theory your stuffing twice as much air into half the cylinders, so it would be about the same power output, of course nothing is 100% efficient.

9: My thought is, would 2 mildly boosted cylinders produce enough hp & tq to drive the car (everyday use, not a go fast goal)? What kind of economy would it result in? Boosting will increase the efficiency of the boosted cylinders, but will it be a bigger gain than the drag from the 2 air pump pistons?

10: Everyone ranks on the poor 2.slow, don't get me wrong it is in no means a "fast" car, but it goes ok to me. In every day use, I never use more than 50% throttle, am almost always barely on the gas pedal at all, and I have no issues at all getting up to left lane highway speeds in a timely fashion. My thought here is I can live with less HP & TQ in a commuter car as long as I can see the return at the pumps.

11: Say my "system" was 50% efficient, that would mean I have 75% of my HP & TQ (which I could deal with as I've driven much slower cars before), but would that also equate to 45mpg +/-? I'd take that, TDI fuel milage at the cost of regular (hopefully boost stays low enough to avoid running higher octane, but hey, that's what knock sensors are for right?)

12: Think MPG, not 1/4 mile ETs or top speed.
Think, will it be more powerful than the geo metro 1.0L 3 cylinder with all of 53hp and 58 ft/lbs (but rated at almost 60mpg!). The car stock has 115hp and 120ft/lbs, so cut it in half and you've got 57.5hp & 60ft/lbs, there's the geo metro numbers already, now use the 2 dummy jugs to mildly boost the other 2, figure a few simple gains in theory.
10% gain = 63.25hp & 66ft/lbs
25% gain = 71.87hp & 75ft/lbs
50% gain = 86.25hp & 90ft/lbs

13: Realistic turbo setups take these motors (on stock internals as they are forged lower ends) from 100whp +/- in stock form to the 200whp +/- range. So, half the output of a mildly boosted setup, would be right around stock output, based on the fact that your now (under mild boost) making almost 50HP per cylinder, do you really need all 4? Even pulling off 35 to 40 HP per cylinder would give the car plently of power to everyday drive on just 2 cylinders, no?

14: I drove my old rabbit diesel (1.5L NON turbo) for years, it taught you how to maintain momentum as there was no acceleration and it had 49hp and 74 ft/lbs new, and mine had over 250K miles on it. I got 45-50mpg, granted the car was a touch lighter than mine, but you get the idea.

Thank you very much for your time, and your opinions and/or thoughts on my "out of the box" idea are greatly appreciated. Don't feel bad if you can poke holes in my theory, that is why I am asking. If it sounds promising, I have all the spare parts already and may actually try to start tinkering with them.

Just to let you know, I am no "kid" with goofy ideas and no money, I am in my 30s, have a degree in auto tech, work in the software industry, and obviously have way too many thoughts bouncing around in my head. Let me know what you think of my "totally new idea", well as far as I know at least. Maybe I should call it the JoJo cycle engine?

I am no VW expert, more of an all around mechanical guy, 2 strokes, 4 strokes, whatever. Working on a 2 stage air compressor made me think about this (one piston is twice the size of the other running at the same rpms), plus knowing motors and 2 strokes gave me this brainstorm.

I was thinking of a hacked lower intake manifold, a modified tri-y header, and other "swap" type parts to keep the cost down, obviously the cam will cost some dough to design and/or get made, but all other components could be fairly affordable. I am open to any and all ideas. Thanks again for your time. JoJoTheTireMan

Added Thoughts before posting:
I realize the air pump cylinders' valve train would be running at 2x's the engine's RPM, so ti valve springs would be a must. I never rev over 5K anyways, and barely ever over 4K, so getting valve springs that could handle 8-10K RPMS is not out of the question.

Ok, I think this post is long enough at this point, sorry but I had to get this idea out of my head in all it's disorganized glory or else I would have exploded and/or imploded, still not sure on that theory yet either :-( Thanks for your time. JoJo

Last edited by JoJotheTireMan; 05-07-2008 at 03:39 PM.. Reason: List was not suppossed to have smileys, just colons
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