Educate me on superchargers...
Here is my KB twin-screw
Tasca Super Boss 429 Member
Joined: November 14, 2007
Posts: 3,651
Likes: 8
From: Pacific NW USA
You make a good point, but your low-end air transfer function has to be totally out of whack to make that big of a MPG difference.
As for rear gears, they do have a huge impact on MPG. The 2000 Crown Vic in base form got 2.73s and could get 25 MPG on the highway, while those that got 3.55s were rated for 21 MPG on the highway. At 80 MPH, the 4.6 runs at 2100 RPM w/ 2.73s, 2700 RPM w/ 3.55s and 3300 RPM w/ 4.30s
In the 07 GT, at 80 MPH the engine runs at 2500 RPM w/ 3.55s and about 2900 RPM w/ 4.10s (using base 17" tires).
Our freeways are limited at 70 MPH so the average traffic speed is about 80 MPH. I can only get near 25 MPG by driving 55-60 MPH, well below the speed limit and I suspect many of the hypermiling Mustang owners drive at 55-65 MPH and not the 70+ so the engine RPMs stay low with 4.10s or 4.30s
As for rear gears, they do have a huge impact on MPG. The 2000 Crown Vic in base form got 2.73s and could get 25 MPG on the highway, while those that got 3.55s were rated for 21 MPG on the highway. At 80 MPH, the 4.6 runs at 2100 RPM w/ 2.73s, 2700 RPM w/ 3.55s and 3300 RPM w/ 4.30s
In the 07 GT, at 80 MPH the engine runs at 2500 RPM w/ 3.55s and about 2900 RPM w/ 4.10s (using base 17" tires).
Our freeways are limited at 70 MPH so the average traffic speed is about 80 MPH. I can only get near 25 MPG by driving 55-60 MPH, well below the speed limit and I suspect many of the hypermiling Mustang owners drive at 55-65 MPH and not the 70+ so the engine RPMs stay low with 4.10s or 4.30s
Our freeways here range in speed limits of 60 mph to 75 mph, depending on how close to major cities they are. I only offered up the 60 mph cruise control #'s as an example that I've tried for curiousity. My actual driving tends to be in the upper 5th percentile of speed (read: over the limit).
Around town, I get horrible mileage (about 12-13 mpg), but that was happening before the supercharger. My 4800 rpm stall converter always keeps the car revving a lot higher than stock anytime I'm driving around town (especially from a stop). On the highway, the big stall converter is not an issue, as it's a lock-up converter that's programmed to lock-up in 3rd, 4th, and 5th gears 1 second after getting into each gear (even at WOT, tuned that way for more acceleration at the end of the 1/4 mile dragstrip). Incedentally, a stock converter is only programmed to lock-up in 4th and 5th gear from the factory, so having 3rd do it, as well, helps a little in the power & economy realm.
Last edited by Five Oh Brian; Dec 1, 2008 at 05:19 PM.
Cobra Member
Joined: October 15, 2008
Posts: 1,373
Likes: 0
From: Brew City
Well that is refreshing to hear and re-enforces my decision to get "blown"!! Lots of power waiting to be unleashed under the hood, but still a car that is not going to kill you with gas consumption.
I think the reason some people aren't seeing a huge mileage difference is that before you had to push the pedal more to get the same driving result. aka, the car goes with less effort - therefore less leadfoot required for a good time.
How much did that set you back?
(I'm in Niagara, storing the beast for the winter)
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