ICRAZY6

iTrader: (68)

Ok, I've searched in the Forced Induction section along with the Gears and Axles section and found no help.

What rearend gears are you running? I have 3.70's in a MWC 9" I'm also an Auto (4L65E). Curiour what type of MPG you are getting? I drove the car for a week straight on vacation and got anywhere from 11.5mpg to a best of 15.4mpg. Mostly interstate driving 75-80mph, the 11.5mpg was from playing with a few cars.

Details: AES 390cu in @ 9.25:1 CR D1SC with 7.65"/3.55" pulley, SS3600 Yank Stall, FLT Stage IV trans, MWC 9" 3.70's Standard tire size.

Thanks,
Ken

NoGo

iTrader: (2)

I run 3.73's in a modified stock 10-bolt.

I get 14 mpg pretty consistently.

Low compression is the kiss of death for gas mileage.

GmanSS

iTrader: (3)

I average 19 give or take and 26+ average on the highway. Smallish cam and a 6-speed. It's a 99 SS 7.65/3.7 pulley combo P1SC FMIC

5.3blazer

running mine with 3:42 rear gear p1sc 5.3 with 3.2 pulley on e85 8mpg city 15 highway with 4l80e trans,cam

ICRAZY6

iTrader: (68)

I'm guessing that your still on the stock motor running stock compression?

ICRAZY6

iTrader: (68)

Doesn't make sence to maybe go with a larger rearend gear like a 3.25 or 3.00 to bring the rpms down? Or step up to a 28" tall tire? The car isn't a daily driver however I do like to drive it accross country. My last trip was about 3500 miles and cost me about a grand in fuel. Thanks for the help!

NoGo

iTrader: (2)

I'm not a mpg expert, so this opinion is probably worth as much as you paid for it.

I don't think you'll notice much of a difference, if any.

Even with my supercharger off I still get 14 mpg. The biggest drivers I have found that affect my gas mileage are the tune (I run SD open loop), my cam, and my compression (I run 8:1)

ICRAZY6

iTrader: (68)

I'm SD tuned as well, My cam is .595 int .608 exh and compression is 9.25. Maybe in a few years I'll bump the compression and see how it does. Just curious as to what everyone else was getting. Looks like I'm par for the course on this one.

NoGo

iTrader: (2)

If you are open loop then there may be some mileage to be gained by putting in a couple forward O2 sensors and getting the car back to closed loop.

If you are SD closed loop though, then there likely isn't much you can do to the tune to pick up any noticeable differences in gas mileage.

GmanSS

iTrader: (3)

I'm on the stock long block and 3.42 rear. I have an SD tune that I spent alot of time on as well. I was rich on decel with the 60lbers and tuned my DFCO to be more aggressive and that gained about a mile to gallon or so in town. Turned LTFT off still have STFT on. From what I understand you can get "Hotter O2's" which read more accurately in long tubes. Some people also take out too much timing down low with these setups. Low load and low compression can tolerate a lot of timing even with FI just make sure the spark transitions into boost are correct. Only way to tune for sure is a spark hook test or a great deal of trial and error.

The Alchemist

iTrader: (19)

I have 3.73 gears in my 10-bolt but I plan to go back to 3.42s I think.

conan

iTrader: (5)

Why ???

Just asking because I was thinking about 3.73 when I get a 12 bolt rear, but I do like the ratio of the stock 3.42 so I've been on the fence with that decision.

The Alchemist

iTrader: (19)

Mostly due to traction issues. As soon as I roll into the throttle enough in first and second to close the bypass valve, the torque just blows the tires off. Plus the gears feel so short with the extra power.

I'm going to try and run a slightly taller and wider rear tire and see if that helps for now. I'm going to go from a 275/30/19 to a 295/30/19 and see what happens.

Stangkilr

iTrader: (47)

I have a customer that has 180k miles on his pro-charger/engine. Never has replaced one part.

conan

iTrader: (5)

Thats what I was afraid of. Thanks for the info.

NoGo

iTrader: (2)

I don't know what kind of tire you are running, but I was going to do the same thing (swap back to 3.42's) until I switched to Toyo Proxes R888 tires.

They stick like paint and aren't suicide in the rain.

My car will firmly plant 3rd on a hot day.

I've been through a ton of different types of tires and I've had this tire on for 2 years now with great results. The only thing stickier that's been in the back are slicks and MT's - and both of those were suicide on wet roads.

BigRich954RR

iTrader: (1)

427 F1C heavy GTO i get 21-24 mpg highway though a 6 speed car puts down 950rwhp. If im flooring it or play around mpg arent with even looking at. SD tune

The Alchemist

iTrader: (19)

I'm happy to hear that the R888's are good tires. I'm currently rolling on Michellin Pilot sport tires that are a few years old, so they are probably getting a little hard at this point.

I think a new set of tires is in order for me.

As for mileage, I was seeing 17-19mpg city driving with the procharger on last year. Mostly shifting between 3000-4000 rpm since I had plenty of torque and didn't need to push the revs. I actually didn't notice any change in my mileage with the procharger, well, except when I was out having fun, then the mileage dropped considerably, but what do you expect when you're maxing out 60# injectors.

35thsscamaro02

Lol put a real tire on the car and you won't have traction problems!

ICRAZY6

iTrader: (68)

I'm sure my milage would be better if I was a 6 speed. I just put on the ET Streets so well see how those grip. I'm currently looking foor 18" rims foor the car.