Gas mileage on supercharged stangs???

greatwaster · Jan 13, 2010

I have 400hp by way of Vortech charger, 42lb injectors, exhaust, custom tune, blah blah.

I am getting 10mpg. As petty as this sounds...I should be getting better then that! What do you get?

Kilgore Trout · Jan 13, 2010

I get 8, who cares! It is what it is, not an economy car.

trombonedemon · Jan 13, 2010

Stop w/the lead foot! These cars are'nt that bad w/ light accelaration! Your computer will adjust to the light driving!

32ValveRom · Jan 13, 2010

400 to the wheels? Do you romp on it alot? Just wondering what to look forward to

SVT32VDOHC · Jan 13, 2010

Mine got better when I added my Vortech on the 96 Cobra. And my 04 is not any worse with the Whipple.

BlackArtemis · Jan 13, 2010

Wait, you get 8MPG on a stock Cobra? Jesus...

Ateup · Jan 13, 2010

Holy crap...are you all serious with the 8-10mpg?

trinity_gt · Jan 13, 2010

A lot of what determines the fuel economy with a blower is in the fine points of the tune. Highway mileage typically drops a little because timing is removed and in-town mileage drops because things like acceleration fuel enrichment are fattened to stave off detonation. If you're running the stock MAF it's likely the thing is pegging before you get to 400rwHP and the tune is conservatively pouring fuel in to prevent detonation. With matching hardware and a careful tune you can recover at least some of that fuel economy.

If you regularly beat on it and actually access some of those ponies you're going to see ****ty gas mileage. If you baby it, you'll do better. I think mine does something like 24MPG on the highway (110KPH, A/C off, cruise set...) and 12-14 in the city. The problem for me is that while I always have good intentions of "taking it easy" to improve economy, I always end up blowing it and having fun with it whereupon is proceeds to guzzle gas. And to be honest, that's why I have the blower in the first place...it's fun

My 1.8T VW GTI is my DD/fuel mileage car...

greatwaster · Jan 13, 2010

24mpg? How in the world?!?!? I do have a Lighting MAF and 3.73 gears. 406hp to the pavement. Seems slow now...

But I get 10 - 12

trinity_gt · Jan 14, 2010

greatwaster said:
24mpg? How in the world?!?!? I do have a Lighting MAF and 3.73 gears. 406hp to the pavement. Seems slow now...

But I get 10 - 12

Couple of things:

Remember, you're only making 400HP to the wheels with the throttle wide-open and at high RPM. On the highway, the throttle is barely cracked and the engine is loafing at 2000RPM. My best mileage of 24 was on the highway. It takes only nominally more power to push your car along at 65MPH (or whatever) now than it did before the blower. The extra power is now going into driving the supercharger though because it's essentially freewheeling (manifold is in vacuum) and takes only a few HP, if that, to drive in that condition. So adding a blower doesn't -- or shouldn't -- automatically decimate highway economy. Of course if you keep your foot in it on the highway YMMV.

If you're getting 10-12 on the highway I'd suggest you start looking for fuel leaks or something. I don't really see how a computer-controlled fuel system could be dumping that much unnecessary fuel into the engine (to give such crappy highway economy) without all sorts of error codes being set unless the tune is set for open-loop or something...

Around town is different. I never got great mileage in-town before the blower and now it's worse, mainly because it's a hoot to get on it ... not to extremes but every 1/2- or 3/4-throttle burst dumps a bunch of gas in, especially on a PD blower like mine. In addition, I'm using Kenne Bell's "chip tune" and the stock MAF which is a very safe combo but probably not optimized. One day I'll go Lightning MAF and get a proper dyno tune and that might help.

usaf_branham · Jan 14, 2010

im getting around 14 with 4.10's

SaleenGT2001 · Jan 14, 2010

i can pull in the 20's with my car on the mid 600 tune. the 0.50 OD helps a lot with mine

patman0911 · Jan 14, 2010

I wonder about you supercharged guys - some of you suffer only a minor drop in mileage while others get hosed on it. I wonder if different tuners are doing different things with part-throttle tunings? Are some tunes running open-loop all the time and running rich in all conditions in the name of a "safe tune"?

What Trinity is saying makes sense, there should be some drop-off because of the added load on the motor and the ability to ingest considerably more gas at full throttle, but if you stay out of boost, mileage shouldn't drop that much, certainly not down near single digits.

joshjwc9 · Jan 14, 2010

Absolutely right, but that is the difference in a PD blower and a centri. The Vortech/Paxton/Procharger guys can stay under 2.5k RPM's for the most part and actually either gain or break even MPG wise. I think the guys with the KB's/Whipple's/Tork Tech are the ones that have been having issues, in addition to the major variable, the tune that is on the car.

The answers that everyone gave are right, but there are so many variable to go in between to be right about everyone!

Midnight2V · Jan 14, 2010

If it's all highway miles, I can get better than 30, in town around 23. Thats assuming I don't get on it at all. On a track, I'll burn a tank in one night of test and tune.

If all you do is red light stomp, rinse and repeat, you are going to get horrible results. Your engine needs X amount of fuel to make Y horsepower. Your average car built after 1990 takes less than 20hp to overcome rolling resistance and aerodynamic drag to move at 70mph down the highway. When you use all 400 thirsty ponies to smoke your tires for 400 feet from light to light to light. Your fuel economy will be slightly reduced.

Your engine is a glorified air pump, if you want more fuel economy you can do two things:
Run it at something less than maximum power, reduce your pumping losses or both. That means get your foot out of it and your head into it.

Practice responsible driving habits, limit yourself to one blast per car ride for example.

It's kinda cool that reducing air restrictions will nearly always result in increased maximum performance. Port your heads, get well designed cams, use an exhaust that provides scavenging, and get a secondary economy tune programmed for normal commuting.

Yes, positive displacement blowers use more fuel - Specifically twinscrews because they are always doing work...even off throttle. One of the hallmark designs of a twinscrew is the male and female rotors that when rotated together create internal compression (compression within the housing of the blower). This means that even when not generating boost, twinscrews are doing work. Few roots, and no centrifugals have internal compression, and when not in boost, are simply windmilling.

That being said, superchargers will be a load on the engine at all times if for nothing else than the friction from spinning them. People who see an increase after installation probably have their tuner to thank for optimizing their air/fuel ratios - which from the factory are pretty conservative.

spederman · Jan 14, 2010

I recently made a road trip. I drove consistently between 80-85mph and i got 20MPG. If i'm doing a combo of city/hwy and driving it HARD but not WOT all the time, i get avg of 17MPG.

32ValveRom · Jan 14, 2010

spederman said:
I recently made a road trip. I drove consistently between 80-85mph and i got 20MPG. If i'm doing a combo of city/hwy and driving it HARD but not WOT all the time, i get avg of 17MPG.

Centrifugal?

spederman · Jan 15, 2010

32ValveRom said:
Centrifugal?

yes, Vortech S trim

bhuff30 · Jan 15, 2010

It's all about the tune and your driving habits. My 2.3 has a ****ty tune that rarely goes to closed loop, and my driving is basically to the track and back. I get 9-10mpg on E85. Given a manual tranny and a good tune, I could probably get that back up to 25 though.

greatwaster · Jan 16, 2010

I am going to check for fuel leaks tomorrow. Something isn't right. I noticed today that I can smell fuel when making a hard turn to the left.

Gas mileage on supercharged stangs???

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