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Old 05-08-2008, 09:01 AM   #6 (permalink)
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Location: South Louisiana
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FarFarfrumpumpen - '03 Volkswagen Jetta Wagon GLS Premium

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My thoughts are in BOLD take them as you may


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.Good Idea maybe a standard supercharger would work better, but would require a smaller engine

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.Use a liquid to air charge cooler, keep the plumbing as short as posable, investigate the idea of warmer air for efficiency

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.Gapless Lower tension rings, no need for oil squirters (if equipped) either which 2 to pick would be determined by which 2 running would still run best

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.probably a need for complete fuel/ spark control on a project like this, i'd look in to standalone ECU's Mega squirt is cheap, works well. Otherwise I'd throw the factroy maf on the intake of the 2 compressor cylinders, emove 2 injectors, and give it a go

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. if the throttle body is before the air compressor there is no need for a BOV, a system like this should work correctly with out a wast gate (essentially a positive displacement supercharger)

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.I take it crossflow indicates that intake and exaust are on opposite sides of the head?

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).Umm, I believe you

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. could add an old mr2 clutch type supercharger to gain back your needed hp, if you need them

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?It would be driveable, I don't know if it would be acceptable to you, or not. take a look at the power/ performance of the forkenswift, it is driveable

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?)I don't know about where you live, but here the price "premium" for premium isn't that large % wise

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
Why not swap in a 1.0 metro motor? put an MR2 Clutch super charger on it, spray some water/ methanol in it when boosting so you can run 87 octane?

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? all depends on your expectations

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.
I drove my TDI boost free for a few days, I know the feeling

Thank you for throwing this idea out there, I'd like to see it tried, but I would do it low budget as a test.
2012 Tesla Model S P85
2013 Nissan LEAF SV totaled by now deceased intoxacated driver.
2012 Nissan LEAF SV
6 speed ALH TDI Swapped in to a 2003 Jetta Wagon
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