AMOUNT OF MILEAGE REDUCTION WITH SUPERCHARGER

[Mitch]

Before the procharger install I used to average about 18 to 19 MPG. Now I am averaging about 14 to 15 MPG http://forums.freshalloy.com/images/graemlins/shocked.gif. I knew I would have a reduction in MPG but did not quite expect it to be this much. What kind of MPG is everyone else who has had superchargers installed getting?????????

[SukairainKupe]

You lost 4mpg but gained 120bhp, that's actually quite impressive. If superchargers are as reliable as some claim they are, then how come not more companies use them? Instead of VQ35DE, Nissan could have used VQ30DE-Supercharged and provide 300+hp and better gas milage. Mass produced I am sure supercharger don't cost that much either.

[96_ss]

I get <17 without an SC.

[esemes]

just got 18.3 ........

highest mileage yet


go figure

-eS

[AVS007]

You lost 4mpg but gained 120bhp, that's actually quite impressive. If superchargers are as reliable as some claim they are, then how come not more companies use them? Instead of VQ35DE, Nissan could have used VQ30DE-Supercharged and provide 300+hp and better gas milage. Mass produced I am sure supercharger don't cost that much either.



It depends. I have a factory supercharger on my GTP. I also religeously change the supercharger oil every 30k miles, as recommended. However, I know many people who don't know they are supposed to do this. I also know people and a dealer, that think the supercharger doesn't need to have its oil changed because it shares its lubrication system with the engine. I know of others that think you need to refill it with engine oil. Yet it actually needs two bottles of special Supercharger Oil, specifically made for the Eaton Supercharger. Improper maintentence of the supercharger will cause it to prematurely fail.

Many companies do or did use superchargers from the factory, such as Mercedes, GM, Ford, and Mazda to name a few. I think another reason a company may choose to not use a supercharger is perhaps image. For example, many people call GM anitquated for supercharging the 3800 V6, instead of developing a multivalve, variable valve timing V6. Of all these companies listed, I think only Mercedes was able to get away with bolting on a supercharger without negative press.

All this aside, a factory supercharger may not be all that cheap. My GTP's supercharger costs like 2k if I needed it replaced. Also, the supercharger was not just bolted to the L36 engine. The L67 supercharged version has a lower compression ratio, different connecting rods, pistons, heads, tranny, etc. In some cases it may make more sense to simply bore the engine out. I think GM took the 3800 about as far as it can go, so supercharging it was logical. I also don't know of any supercharged engines that don't require premium, but I know of many multivalve, relatively high output engines like GM's new 3.6 DOHC VVT engine that only need regular. To some people that is important.

Torque is another reason. GM hasn't offered a manual transmission in the W body cars, because they claim that they don't have a manual transaxle that can handle the 280+ pound feet of torque from the engine. The preproduction GTP (called the 300GPX) was 300 HP, but was detuned because the 4T65E-HD transmission is only rated at 280 pound feet of torque. (and the 4T80E trannny from the caddy won't fit.. oh the joys of FWD) This is the same reason the turbo charged volvo T6 engine is also tuned for "only" 280 pound feet of torque, as it uses the same GM tranny. I also remember reading a Motor Trend article, that featured an HKS supercharged Honda Accord V6. With the bolt on supercharger, even though the numbers looked good, performance wan't impressive becuase the torque converter in the tranny kept overheating (even with a big arse tranny cooler). That tranny was pretty much tuned for the J30 engine which makes < 230 pound feet of torque. The J32 engine in the Acura TL only makes like 232 pound feet of torque, so the tranny isn't quite as stressed by the 270 horses. (The main reaon I bought the G35 over the TL, because I love torque http://forums.freshalloy.com/images/graemlins/grin.gif)

anyways, I'm rambling now...

[Eagle1]

I lost between one and two mpg. The loss on the cruise is about one mpg. In town is a bit more. Probably half of the loss or more is simply due to using the hp in acceleration, which though highly satisfying, is very consumptive of fuel. Right footitis is as big a culprit as the belt drag, if not more.

[ebdbdave]

No matter if i drive city or highway, my MPG range from 19.5 (mostly city) to 21 (all highway). That really sucks!! I'm going to ask the dealership to reboot the ECU; maybe I had a bad tank of gas once...
dave

[Q45tech]

It takes roughly 0.5 pounds of gasoline per hour to make 1HP.
Assumming that a supercharger requires 4-5 HP at cruise and 20-30 HP at WOT just to turn the compressor.

2 extra pounds per hour [4HP]~~= 1/3 of a gallon so a normal 2.5 gallons per hour becomes 2.83 or 13% worse highway cruise mpg at 65 mph......24 vs 20.9.

Rough and dirty caculations but probably pretty close but I'm guessing at the parasitic drag of the compressor [belts, pulleys, bearings,]........the above assumes vacuum controled bypass valves around the supercharger.

Radial superchargers will probably have less parasitic drag the Eaton type.

Notice MB uses a BIG Strong electric clutch on its supercharged engines.