I have a 94 z28 M6 with stock 3.23's. It has 80K miles on the clock. My MPG relevant mods are:

summit 1.5" lowering springs
Moroso CAI and smooth elbow
Flowmaster catback
235/55/16 front tires (which I hate!)

I drive this car 500 miles a week. I live in MS and I make a 210 mile drive to west florida and back every weekend. It's a mix of highway, interstate, and country driving. (55mph on 2 lane curvy roads)

I average 19-22mpg with very aggressive driving, going 10 over the speed limit. If I accelerate slowly, and only go 5 over the limit, I can get 26.8mpg. I figure If I accelerate really slowly, and drive exactly the speed limit, I might be able to touch 30mpg on this route.

I also might need to get a couple MPG supporting mods to help me out. I was thinking of the following:

Meziere electric water pump
ASP underdrive pulleys
Pacesetter headers with dual cats and new o2 sensors
GTS headlight covers for better aero ( maybe)

Will those parts help me at all? I know z28's are supposed to go fast, but I also think it would be cool if I could achieve 35mpg highway. That would really be an accomplishment considering how much the environmentalist crowd dislikes cars like ours.

 

Add these:
MSD 6A/6AL ignition
PCM tuning

 

+ custom fuel economy cam?

And a crapload of weight reduction

 

Really? I can see the ignition helping, but I always thought that a PCM tune would drastically decrease mileage?

I'm not THAT motivated to be a tree hugger. I can only imagine that any custom cam to increase mileage is gonna have a horrible effect on power. I'm not doing any mods to make me slower. No 2.73 gears or smaller cam.

I'm down with a little weight reduction, but I can't think of much to remove. I have removed my back seats, but they weigh like 10 lbs. This is my DD, so I don't want it to have an interior like a race car.

 

A very small turbocharger. Something that makes 1-2 psi at 1500rpm.

I have to say, that would be a really interesting project.

 

does your trip include any noticeable gradients to favor a direction? i wouldn't think so being you're just driving along the coast. ONE TIME with a favorable tailwind driving from dallas to houston (very slight downhill) i got up to 32MPG avg, that's with 3.73's too.

overinflate your tires some, will decrease rolling resistance. aerodynamic modifications that only reduce cd, not produce downforce, also help. if it's possible, improving under car aerodynamics has the greatest potential. also reducing frontal area, which you have already done by lowering, helps. one way to improve undercar aero would be convert to front breather cooling system, ditch the airdam, and build a front-half belly pan from the nose to the k-member and even a rear valance to keep air out from inside the rear bumper. the rear valance, or diffuser minus the fins, would bend up before the rear axle, cover the gas tank and muffler, and meet the bumper at the edge. there are plentiful mounting places all along the edges on the rear bumper (the body sheet metal extends all the way to the bottom of the bumper cover) and since camaro bumpers are flat along the bottom, unlike firebird/trans ams, it's VERY easy to shape the piece. other than the front breather conversion there should be very little fabrication other than cutting and bending sheet metal. these mods would be fairly discreet as well, maybe not quite so much the rear though.

 

That would be hard to do. It seems like it would surge if you ever went more than 20% throttle.

BTW, I forgot to mention in the first post...... I'm not made of money. I picked out a few cheap common bolt on mods that I might be able to find used.

 

Do you have any pictures or drawings of this?

 

Search the lounge, their is a guy do an experiment on MPG with his fbody, its pretty good reading.

 

that will make it worse, you would need more fuel.



just do the mod you were planning and see where your at, under drive pulley, header, 02s. i might skip the electric water pump since you drive it that much... hate for that to die mid trip.

 

Didn't all the M6 cars come with a 3.42 gear rather than 3.23?

 

You'd need more fuel at a given throttle position, but the increase in efficiency you get from the turbo means that you could give it less throttle when cruising in order to maintain the same speed.

The trick would be finding a way to set up the turbo so that it would stay spooled at such low RPMs, without causing surging issues.

 

I was concerned about that. I drive though some really desolate areas, and I drive ALOT. I was concerned about the reliablility of an electric water pump. Mine is leaking through the weephole though, so I thought "if I'm gonna replace it, I might as well upgrade."

I pulled my rear cover off and checked. My carrier has 3.23 stamped on the side. It was an old clutch style diff though. I thought all 4th gens had zexel torsens?

 

LS1 conversion with T56.

Or coil pack ignition and headers.

 

the backpressure from the turbo alone would probably hurt you more then it would help.
plus with 1-2 lbs of boost you would have to have the afr around 12 vs 14.7... to keep it from melting the pistons.
not to mention make the car useless at all other speeds.

the lt1s have enough power at 1500 you dont need to give it much to keep it at a steady speed.