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Old December 17th, 2010, 17:42   #46
Veteran Member
Join Date: Apr 2010
Location: Houston, TX

Originally Posted by frugality View Post
There is less air going through a TDI intake (intercooler included) than a gasser intake. Our cars get better mileage because they get more 'bang' for the amount of fuel and air. At highway speed, our TDI's will be turning 2000rpm. A similar 2.0T gasser will be higher, say 3000rpm. With the same displacement (and boost), the gasser will be flowing 50% more air.

How it's throttled is a separate matter.
No, our engines get more bang because they recycle some of the heat generated from combustion for ignition and because diesel fuel is a longer chain molecule and stores more energy so it takes less volume. A 2L displacement engine pumps the same amount of air at a specific RPM (assuming same flow resistance on intake and exhaust) regardless of weather it's burning diesel, gasoline, or is being turned by an electric motor or your wheels.

Of more interest to me is the fact that heat is recycled. This implies (and indeed it does hold true) that a certain amount of heat is needed for efficient operation. Restricting cooling to help maintain that heat level makes sense in that case.

2010 VW JSW TDI "Barley", 6-speed manual, Blue Graphite - 255/40's on 18x8's, Sigma6, B&M Shifter, Malone Stage 2, Koni coilovers w/H&R springs, 28mm front/27mm rear swaybars, GTD Grill, 900W stereo, PDE downpipe, Banks exhaust, APR intake, Votex kit.
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