question about procharger

[TrAnS Am 98]

im not really knowledgable on this subject so im just curious, what affect does the procharger have on your mpg does it stay the same lower or increase??

[Ken(Bone Breakin Chevy)]

im pretty sure more air=more feul. so im gonna say it lowers it.

[Performin Norman]

I had a 355 forged motor with a P600B running 15 psi pulleys but seeing 12 psi at the manifold. I had 3.73:1 gears with my automatic. I got 10 MPG on a good day.

[Joe 1320]

and as a comparison, my N/A with an auto and 3.73s gets me about 19 mpg combined.

[Jeff_in_Atl]

I have a sneaking suspicion that Norm's 355 motor probably had a pretty big cam in it too so it's not a fair comparison to a stock motor.

Here's the deal. X amount of fuel plus 14.7 times X amount of air is going to make Y horses no matter if it is supercharged or normally aspirated. Period. So to answer your question, in theory, a supercharger does not use more gas than a N/A motor if driven the same. As to same I mean same rate of acceleration not same amount of throttle.

In reality, it feels so good it's hard to keep your foot out of it. Most people typically use the same throttle pedal position whether it's a 3 cylinder Isuzu or a supercharged 383 550 lift F-Body. So most people will see a drop in fuel mileage with it under normal driving conditions. Floor it a few times and the gas mileage will be lower. It's the price to pay for performance.

[Joe 1320]

To a point, it might be a little unfair of a comparison but keep in mind a crank driven supercharger is going to put a load on the crank even at idle. A load is going to cost fuel consumption, whether it is an accessory like an alternator, water pump, power steering pump or an air intake pump (supercharger). A supercharger doesn't freewheel, it takes power to turn that increases with rpm and boost pressure. Meaning that the 100 HP at the wheels you just gained, was actually closer to 175 HP but the blower took 75 HP to turn at 4800 rpm so you only realized a net 100 HP. Even at idle, it takes power to turn the blower so providing you can keep your foot out of the throttle, the difference in fuel consuption is close to the difference that using the a/c and not using the a/c in a normal vehicle. 2-3 mpg decrease at cruise is not uncommon. When you put your foot in it, all bets are off and they get very thirsty.

[Jeff_in_Atl]

Originally posted by Joe 1320
To a point, it might be a little unfair of a comparison but keep in mind a crank driven supercharger is going to put a load on the crank even at idle. A load is going to cost fuel consumption, whether it is an accessory like an alternator, water pump, power steering pump or an air intake pump (supercharger). A supercharger doesn't freewheel, it takes power to turn that increases with rpm and boost pressure. Meaning that the 100 HP at the wheels you just gained, was actually closer to 175 HP but the blower took 75 HP to turn at 4800 rpm so you only realized a net 100 HP. Even at idle, it takes power to turn the blower so providing you can keep your foot out of the throttle, the difference in fuel consuption is close to the difference that using the a/c and not using the a/c in a normal vehicle. 2-3 mpg decrease at cruise is not uncommon. When you put your foot in it, all bets are off and they get very thirsty.

Good point. I would still do the supercharger. I wish My 95 had a turbo. I have to keep up with my wife's turbo beatle. LOL

[fastTa]

There are electronically controlled RPM sensitive air bleed valves that have become a standard for a street install of a centrifugal blower. Due to this there is hardly any parasitic load below 1,500 rpm on a centrifugal blower. Less than your alternator.

If you were to take a stock LS1 and record it's gas mileage while under normal daily driven conditions and then take that exact same motor with no other mods besides the addition of a street centrifugal blower, you would see very little difference in mpg if any at all.

Roots blowers on the other hand destroy mpg.