Stevie1982

I know the specs are 15mpg city/26 highway. Just wondering what everybody else is getting. I checked mine the other day and I got almost 18 mpg highway.

74 LS4-454

When I used my 82 as a "dd", I could get between 19 & 21 mpg for a daily 94 mile commute. Combination 90% highway, 10% local. On very long trips did better.

Stevie1982

Thanks! Just trying to get an idea of what to really expect!

74 LS4-454

No problem, if your looking for mpg, it really depends on your right foot and how good the engine is tunned.

Easy Mike

At first glance, I thought you were posting 82 miles per gallon. No one could argue with that figure.

Buccaneer

OK, this may sound kind of messed up and don't read into this, but its a corvette...not a Prius. I personally don't care what the mpg is with my 82, only that I can beat up on C5s successfully when the situation presents itself. They really don't like getting beat by a CF.

billschroeder5842

However I get a combo of about 17 mpg with local, highway and LOTS of Dallas area stopNgo

NewbVetteGuy

I couldn't disagree more. Many of the things that will improve the fuel economy of our C3s will also improve performance or drivability (although there's definitely some cases where you have to choose between performance and economy).

Examples of things that can improve economy AND performance or driveability:

• Light weight wheels and drivetrain components (aluminum drive shaft, clutch/flexplate, half shafts) -unsprung weight reduction helps handling / ride, too
• High compression, fast-burning heads
• New Camshaft-you can get higher lift cams that have small LSAs which will increase compression and torque, but they also happen to improve fuel economy
• Trans Swap to OD trans w lockup torque converter- swapping trans can get you a lower more torquey first gear AND a higher end OD gear and a lockup TQ that improves fuel economy
• Weight Reduction- the gift that keeps on giving, increased acceleration, improved handling AND improved fuel economy (10% weight reduction = 7% fuel economy reduction; fueleconomy.gov says 2% increase per 100lbs shed)
• Reduced Drag / Improved Aerodynamics: Helps with top speed and fuel economy on the highway
• Alignment- handles and drives better AND gets better fuel economy
• Ignition system- more complete combustion again helps both
• Switching to an Electric Fan -waste less HP AND improve fuel economy
• Underdrive pulley(s) (if you have a good alternator): Reduced HP lost to accessories AND improve fuel economy
• Cam timing / Ignition timing- improved efficiency here can benefit both HP and fuel economy
• Lowering the car- makes it look cooler, decreases drag, helps handling, help top-end speed through drag reduction, improves fuel economy
• EFI- better idle, new high CFM models allow improved perf vs. a non-tuned carb and non-tuned ignition timing; allows for setting multiple configurations- higher perf mode with a reduced AFR, fuel economy mode with an increased AFR -on the high-end sequential multi-port fuel injection can get you significant performance increases AND fuel economy increases as you're adding fuel at the exact right time into each cylinder right when it's most needed rather than as a general spray into a throttle body and through the intake where it may or may not get equally distributed into each cylinder (won't).
• Not something that WE can do, but engineers can and are doing: reducing "parasitic" losses -typical RWD differentials create a 6-10% parasitic loss that eats power and fuel economy; 30-40% of the parasite losses from transmissions come from the hydraulic trans fluid pump -improvements there result in longer lasting transmissions that steal less HP and result in improved fuel economy.

Efficiency is a "no brainer" that helps performance and fuel economy. Weight reduction done safely is the same.



Many of the things that you'd do when stopping to think about and focus on improving fuel economy can improve performance, handling and drivability, too.

Every investment in our cars has a opportunity cost for something else that we can't do, I'm trying to consciously focus on the big "bang for the buck" changes that can provide multiple benefits. Technology can improve both performance and fuel economy simultaneously.


I think the changes from the 79 model year that I have, to the 80 model year and then again to the 82 model year clearly show that some changes benefit both performance AND fuel economy. -Reduced weight going into 80 also saw improved fuel economy, then 82 with Spitfire fuel injection (reliability aside) we saw a jump in HP AND fuel economy.

Buccaneer, your car is actually a prime example of good modern technology changes resulting in improved fuel economy and performance. Crossfire fuel injection w an updated ECM, modern DART heads, a roller cam and roller rockers that reduce friction, improve reliability and make more power for longer, a dyno tune that likely was focused on power but the timing component likely improved fuel economy, too.


Adam

Having said all that, I still want 18", wide, sticky tires that look good and handle well although I KNOW I could be seeing up to a 10% fuel economy drop because of them... (That problem can be partially solved by money if I were to buy more expensive, but lighter wheels.)

Stevie1982

I really like!!! And that is my plan also! Just trying to understand what it should do before I start making it do what I want it to do.

mikem350

To add to the above, make sure your trans is shifting properly thu all 4 gears, and that you can feel the torque converter lock up in top gear.

If your state allows, a true dual exhaust system (possibly omitting cat converter) is a big help to both power and economy.

Stevie1982

The car runs good. Shifts good. lock-up seems to be good. has new free flowing cat. It dose seem to run a little rich.

hugie82

My last tank I threw down 20mpg with the AC on max and stuck in traffic for an hour. On top of that I was racing a Bentley at speeds I'm pretty sure would of required bail money. You can't beat an 82 vette for fun comfort and mpg.

SH-60B

Didn't read all of this, and have done a lot of mods to my car, but think about how much gas you could buy instead of all those mods. You couldn't possibly drive the car enough to make them pay for themselves. I also have to especially disagree with fuel injection making more power, that just isn't true. It has advantages over carbs in some ways, but increased HP isn't one. Flame on Johnny!😃

74 LS4-454

Ok, I'll "Flame on".....
That is a very blanket statement you are making....."I also have to especially disagree with fuel injection making more power, that just isn't true." Don't you think? Just using some logic, I would say it really doesn't matter what induction system you use, it would more depend on what is used and how the engine is assembled rather than using a carb or FI. Two of mine are FI, and one is a carb.
And all of the vehicles produced use ??? today???
And maybe people like doing mods to their cars, and not worry about how much gas they could have purchased or driving the car long enough to make the mods pay for themselves......
So what!!! let the owners do what makes them happy, not for what you believe in.... "Flame on Johnny"......

NewbVetteGuy

I may have been a bit long and rambly because I think my point got misunderstood; what I was trying to say was that you shouldn't just not think about fuel economy as many of the things that you can do for your car can improve performance, handling and fuel economy; the point was that you consider this as yet another attribute when creating a prioritized list of projects and you'll end up with an all around "better" car faster.

Example: stopping to think about fuel savings caused me to really understand the total benefit of weight savings a bit more, when I combined this with the longevity assessment and my question about which accessories steal the most power, it became clear that replacing the radiator with an aluminum one should move up my list becaues it provides so many benefits.

Light weight, lower temps (reduced predetonation risk, which could allow me to design for higher dynamic compression with my cam and ultimately get better perf and fuel economy just form that one option); lower temps also make the trans last longer, combining aluminum radiator with an electric fan gets rid of the most HP parasitic accessory in the car (hp and fuel economy boost).

All I'm saying is that it pays to stop and think about fuel economy, too when you go to create your prioritized project list. Obviously the return on something for just fuel economy probably wouldn't be great but when you can get your cake and eat it to, that's win/ win.


Adam

NewbVetteGuy

Partially true; I worded my statement very carefully. Many of these cars do not have constantly tuned carburetors and constantly tuned ignition timing; both of these will help produce more power- an EFI that controls your air to fuel ratio AND ignition timing CAN improve power (it's like carrying Lars around under your hood and having him constantly tune your carb and having someone else constantly around fine-tuning you ignition timing / curve.). -It also lets you set the AFR -at the push of a touch-screen to run more rich for more power when you want it to; usually with a carb you're setting a middle-ground AFR that's a compromise - compromise lost, performance gained.


Much of the tribal knowledge regarding the first few generations of EFI seeing a loss in performance come from poor designs that limited airflow AND of course the slightly decreased atomization of the fuel vs. a good carb. The newest generations have better injectors that supposedly atomize the fuels well and they can support HUGE amounts of airflow.

Almost all modern high performance engines use fuel injection- you can get equal amounts of fuel and air in each cylinder and create that perfect AFR in each cylinder rather than again a compromise average between all the cylinders like you get with a carburator or TBI EFI. -Going to multiport or direct (still a version of multiport in my view of the world) fuel injection also allows for better intake designs taht can be designed just to maximize airflow and don't have to deal with fuel-laden airflows, so you can get more airflow and more power.


If you have a really well-tuned car and you just pull a carb and replace it with a TBI EFI system are you going to see more power, well, no; probably not, but that's not what I actually said, either. (Maybe read it next time; reading's an important skill- reading comprehension even more so.)


Adam

SH-60B

Sorry Adam, not reading that long winded post, lol! You don't seem to realize carbs deliver fuel differently than EFI in more than the ways you described. Carbs vaporize the fuel, injectors spray it in droplets. The vaporization by carb has the advantage of the intake cooling effect of latent heat of evaporation that injection doesn't. The motor doesn't care if the center cylinders are a little rich, as long as the outer ones aren't lean, it'll generate the same power from each cylinder regardless, and multi carbs will negate that advantage by injection. Direct injection shouldn't even be in the discussion as it's a completely different animal and you cant retrofit it into a first gen smallblock anyway.

Like I said, plenty of good reasons to use fuel injection, but more power isn't one of them.

COOLTED

If I stay below 65 mph, I can squeeze about 22 mpg with a 79 L48, 3.55 rear. above that it drops drastically. 15-17 mpg at 75.

7T1vette

I had a new '84 car (C4) with the same Cross-Fire engine and I could get 20 mpg at 100 miles per hour (on open road). Overall mileage would be different, I'm sure. If everything is in order, I would think that you could get 16+ mpg in town and 20+ mpg on the highway. The engine has O2 sensor and ECU controls, EFI and the transmission is an overdrive unit with lockup. Highway driving on level ground should get you 22-24 mpg, I think.

NewbVetteGuy

You're right; I didn't and still don't understand that; can you explain?

Why doesn't the motor care if the center cylinders are rich as long as the outer ones aren't lean? -Why does it vary from cylinder to cylinder? (heat related?)

How can it generate the same power from a cylinder that's running rich vs. a cylinder that's running lean?

Totally agree for a discussion limited to just 1st gen SBCs that direct injection is not a fair conversation; the issue of higher temps due to no evaporation of fuel when doing port or direct injection is an interesting one as the greater air flow seems to more than makeup for the slight difference in temps; it's also why many of these modern EFI intakes are using plastics or even aluminum, right? (no/ less heat soak) EFI (port) gives them a lot more options that more than makeup for any loss of heat due to evaporation.


Again, I totally agree that swapping a carb for a throttle body EFI system in a well and constantly tuned car would not see a perf increase, but what percent of these cars are in that state? I still think a slight majority would see a perf increase with a current gen TBI+Ignition Control EFI swap vs. a carb.


Adam