Camaroz18

iTrader: (1)

I wanna know the possibility of making a 450+ horsepower trans am that also allows 40 miles per gallon. By my calculations, I can remove 800 pounds from the car itself by using lighter materials and other techniques as well as adding twin turbos with an active turbo/fuel management system. Is this possible or do I run the risk of hurting the motor by using lower compression ratios?

Wesmanw02

iTrader: (4)

It might be remotely possible but very difficult.

Removing weight is the first step in the right direction. 800lbs is a lot though, you'd basically have a gutted car unless you could replace all the body and chassis components with carbon fiber and aluminum, which is extremely expensive.

A lower compression ratio will not "hurt" the motor at all. What it will do though it make it much less efficient in terms of off-boost fuel economy, which is what you don't want. So what you want to aim for is a modest compression ratio, something like 10:1, which will still allow you to run boost but won't kill your cruising fuel economy.

You will also need to run a smaller engine, like a 4.8 or 5.3. A 6.0 or 6.2 isn't going to do 40MPG no matter how you look at it, you've gotta feed that extra displacement regardless.

I think the best thing to try might be something like a 4.8 with a very mild (LS6) cam, 243 heads, forged crank, rods, and pistons, an LS6 intake, 10:1 compression, and a twin turbo kit pushing a fair amount of boost.

You will also need 3.42 gears or taller, and a 6 speed manual trans to even think of getting close to your goal.

Best of luck.

babbage1109

iTrader: (11)

That is a ton of work just for 40 mpg. For what you'd spend to do that you could mod a trans am and still buy a fuel saver car.

Camaroz18

iTrader: (1)

Ok. Thanks. The car wont be completely gutted. Im trying to make it as light as possible while keeping most of the interior as nice as possible. I wanna run the 5.7 twin turbo set up on it. I've never dealt with power adders. I've only worked with naturally aspirated power. What turbos would be the most fuel economical?

True Babbage, but I wouldn't wanna pay that much insurance. Plus, id rather spend much less in gas and drive the car to shows and raceways

96Ztop

By owning multiple cars only lowers your insurance. In moderations though. And in theory you would still be saving on gas, so you could drive it to shows and such. justa thought for ya. either way good luck

Camarosteve44

iTrader: (8)

To be honest, I cant really see it happening. Considering I average around 19 mpg, even with all that weight out its still gonna be hard. I know guys who do long cruises (from NJ to TN) and the best results are like 29 mpg. It would be hard, but worth a shot.

sslateron

Yes you can or at least 35 without removing any weight. As long as its a 6 speed.
Simply ad a hydrogen hybrid hho unit to the car. You can get a good one from 300 to 900 bucks!

senicalj4579

iTrader: (41)

I really dont see it happening. Ever lol. Im averaging 19mpg with mods in sig and it does weigh a couple hundred lbs less than stock at 3200 with 1/8 tank gas. But hey maybe you could get 30-35 with a manual and all the mods you speak of? IDK

RPM WS6

iTrader: (3)

In general, zero.

You could remove every possibile pound, and use a 6-speed trans with the tallest possibile gear ratio, and 40mpg would still be a strech even on a stock car. Then you're talking about doing a turbo setup, which will add some weight back (turbos, intercooler).

Personally, I don't think it's a realistic goal, and I think you will be disappointed if you spend all this time and money chasing a 40mpg goal as your build priority. If your goal is to build a 450hp car that gets the best possibile gas mileage, that's fine, but picking a specific number (especially as high as 40) is just setting yourself up for defeat.

There are other factors to consider as well. If you go with the expense of a twin turbo setup and lightweight interior materials, plus the possibility of internal engine work (including a potential reduction in displacement), this will be the most expensive possibile way to reach your horsepower and acceleration goals. Having said that, will you drive this car enough to ever realize any net cost savings from the better gas mileage of the significantly more expensive build price? You could do an H/C setup, with all the bolt-ons and make 450hp for potentially several thousand less. That money could buy a lot of gas, for quite a long time.

71novaguy

iTrader: (2)

you could do it with a diesel

Latch

iTrader: (8)

I'm all for more MPG but at some point you're going to spend more money making it fuel efficient than you'll be able to save at the pump. Plus, 40 MPG is a tall order even for compact 4 cylinder cars. No way you're going to see 40 MPG out of an F-body, even a V6. They're just too big and heavy.

A realistic goal would be more like 35 MPG. I say ditch the turbo idea and go with higher compression. Full intake and exhaust. Possibly a mild cam with good low end torque to keep the revs down around town without losing any efficiency. Get some lightweight wheels with fairly narrow tires (like 245s) and ditch the spare and jack.

All that being said, I wouldn't spend much money in the pursuit of making my F-body more economical. The most fuel efficient F-body is still not going to get the mileage that your average Civic gets. If gas prices are hurting you that much then I would invest in a 4 banger to beat around in and save the F-body for the weekend.

DVS99TRANS

iTrader: (7)

Going to agree, 40mpg is not possible without some re-engineering and a ton of money dumped in complete tunes. Not to mention that want more power too which goes against fuel economy. Buy a 4 banger as a beater bro.

2000Z28AUG

Really guys? I think he has a good shot at hitting his mark. Im running the same setup as my sig and I'm averaging 24 mpg... highway that is but nonetheless. If you can find a way to make the rear end lighter and shave weight off of the drivetrain I think it is do-able. A friend of mine runs an M6, stock gear, lightweight clutch, lightened driveshaft, Fast 90/90 setup, LT headers and matching heads/cam and easily gets 34mpg without weight reduction and thats NA. Good luck on your attempt bud and keep me posted with your results.

Foo_909

Just buy a scooter...

UAE_Z28

iTrader: (14)

hehe that's impossible, not with 450hp. If you ever pull it off, u'll deserve a worldwide award lol.

http://www.youtube.com/watch?v=YKn6h2x5IcY

klutch-

my 2 cents, u want 40mpg to drive to car shows and what nots. then u want 450hp for race days... the gas u save driving to car shows ur gonna waste driving at race days...
not gonna say u CANT do it, but i will agree its borderline pointless... good luck

A.R. Shale Targa

iTrader: (2)

Car gutted..(no interior, possibly sitting on a milkcrate,no radio, heater, etc.)
M6 w/3.23 or 3.42. Light rims, tall and narrow tires (less rolling resistance)
DOD or active fuel management on a stock 4.8 with efficient exhaust
A 150 shot of juice to meet your power requirement without all the added
weight of 2 turbos. If you were 2800 lbs with you in it, maybe on a windless
day and smooth road you could achieve your 40 mpg. You definitely have
your work cut out for ya with those two goals in mind.

RPM WS6

iTrader: (3)

I absolutely do not agree, at least not with the build parameters that the OP has outlined.

Part of the problem is this:

There isn't going to be 800lbs of net weight savings once the entire turbo kit is added, especially if he wants to keep much of the interior intact.

Element

iTrader: (5)

My 2800lb 4-banger commuter doesn't get 40mpg on a flat interstate (34mpg regularly)...40mpg out of a 450rwhp+ car? If you can do it, GM, Ford, or Chrysler would probably love to hire you.

A cheap commuter (that doesn't necessarily have to be a piece of **** car) with basic liability is going to add very little to an insurance policy, will give you a second vehicle while the Trans Am is down for modification and maintenance, and will save racking up a bunch of miles on the fun car.

sslateron

Camaro Z did you hear what I said?