MPG
Thread Starter
Burning Brakes
Joined: Oct 2002
Posts: 1,003
Likes: 0
From: toledo oh
MPG
I was curiouos what kind of Milage you are getting with your car. I have a stock 81 that is getting 12.12 over the past 1,987 miles.
Any idea on what would happen if i went with the edelbrock performer rpm set up, including heads, cam, manifold, carb and a larger exaust system?
[Modified by 81Vette_by_eric, 9:01 PM 10/21/2002]
Any idea on what would happen if i went with the edelbrock performer rpm set up, including heads, cam, manifold, carb and a larger exaust system?
[Modified by 81Vette_by_eric, 9:01 PM 10/21/2002]
Team Owner
Joined: Jul 1999
Posts: 65,492
Likes: 230
From: Orange Park Florida
Re: MPG (81Vette_by_eric)
smallblock sharks get around 12 mpg, and BB around 8-10 mpg....in stock well tuned trim....maybe a few lucky types get a few more, but it's NOT the norm...and suspect the calculations, anyway....
now this is everyday mixed bag driving.....
now upon changing my fresh L48 engine over to DPFI..L98 style...closed loop, no other changes....MY car went from 12 mpg to over 24 mpg....
and it was in decent tune....
now the addition of overdrive was done in my car along with the hotrod engine....700r4 tranny....hotrod roller engine L98 hogged out type....
headers.....get ~20-22 mpg....
GENE
now this is everyday mixed bag driving.....
now upon changing my fresh L48 engine over to DPFI..L98 style...closed loop, no other changes....MY car went from 12 mpg to over 24 mpg....
and it was in decent tune....
now the addition of overdrive was done in my car along with the hotrod engine....700r4 tranny....hotrod roller engine L98 hogged out type....
headers.....get ~20-22 mpg....
GENE
Abby Normal
Joined: Dec 2001
Posts: 53,311
Likes: 92
From: Press "2" for English
Re: MPG (81Vette_by_eric)
eric, an L-81 in decent tune should get AT LEAST 15 mpg. a few years back, i did a cross country trip and got 20-21mpg at 75 on flat ground. city driving will obviously lower that number but if your talking highway mileage, i would be very skeptical of the numbers your getting. despite what others may say, the L-81 was a good compromise motor with 'decent' power and really good (for the era) fuel economy.
Thread Starter
Burning Brakes
Joined: Oct 2002
Posts: 1,003
Likes: 0
From: toledo oh
Re: MPG (clutchdust)
my number is total driving....i believe the highway number is somewhere between 15 and 18. I didn't have enough cash on me to fill up the tank to get an accruate reading for the trip.
i like the idea of fuel injection, just very cost prohibative. i saw an injector system from edelbrock for 2k. and one from someplace else for about 1k.
i like the idea of fuel injection, just very cost prohibative. i saw an injector system from edelbrock for 2k. and one from someplace else for about 1k.
Race Director
Joined: Apr 1999
Posts: 15,133
Likes: 477
From: NM
Re: MPG (81Vette_by_eric)
Only time I have ever checked my 73's is on long interstate trips (don't think my heart could take knowing the around town milage :D ).
The 73 L82 auto got 12.9
The 73 454 4-speed got 13.0
But my 90 coupe auto got 25 mpg :D
This was all on trips of over 1,000 miles.
tom...
The 73 L82 auto got 12.9
The 73 454 4-speed got 13.0
But my 90 coupe auto got 25 mpg :D
This was all on trips of over 1,000 miles.
tom...
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Le Mans Master
Joined: Mar 2002
Posts: 7,456
Likes: 2
From: Coming home from Luckenbach Texas
Re: MPG (81Vette_by_eric)
I've never done any actual measurement, but installing an overdrive transmission actually lets me drive past a few gas stations!
I'm not sure if it would help as much on the '81 however, I think they already have a lockup torque converter and a fairly tall rear gear...
I'm not sure if it would help as much on the '81 however, I think they already have a lockup torque converter and a fairly tall rear gear...
Le Mans Master
Joined: Nov 1999
Posts: 5,768
Likes: 3
From: San Diego CA
Re: MPG (Tom73)
On my recent trip to moterey and back for the historics, my 78 got as much as 20 (on one tank interval) which was freakish but I'm certain the numbers were accurate - I dont have the overall numbers (we kinda lost track once we got to monterey, what with all the gorgeous cars running around) - our freeway mileage was probably on the average between 16-18.
City mileage for me has always been around 10-12
City mileage for me has always been around 10-12
Burning Brakes
Joined: Nov 1999
Posts: 790
Likes: 0
From: Flanders NJ
Re: MPG (81Vette_by_eric)
With my '79 Auto with less agressive rear (3:08 vs stock 3:55) ratio
I average between 13-15MPG that's usually a combo. between local countryish roads (speed limit 40-45) and highway. Just wish I had one more gear, cause even with the reduced rear ratio I'm still screaming at 3000RPM at about 75MPH.
I average between 13-15MPG that's usually a combo. between local countryish roads (speed limit 40-45) and highway. Just wish I had one more gear, cause even with the reduced rear ratio I'm still screaming at 3000RPM at about 75MPH.
Thread Starter
Burning Brakes
Joined: Oct 2002
Posts: 1,003
Likes: 0
From: toledo oh
Re: MPG (page62)
I think the stock rear end is a 2.87. At least according to a few websites that i have seen. Based on the trans gears, and what i have seen with the rpm's, its seems about right. Being an Excel guru, i built a little table with all my gears to calculate the different speeds in different gears, and to compare a rear end or tranny swap.
Does anyone know if it is possible to drop in a 5 or 6 speed into an 81. A 4 speed would be an improvement, but 5 or 6 would be way cooler. I know it probally won't be cheap, but i hate the 3speed crap. I would rather have a nice tranny with less horses. My 5 speed berretta seemed like it was faster off the line.
[Modified by 81Vette_by_eric, 4:20 PM 10/21/2002]
Does anyone know if it is possible to drop in a 5 or 6 speed into an 81. A 4 speed would be an improvement, but 5 or 6 would be way cooler. I know it probally won't be cheap, but i hate the 3speed crap. I would rather have a nice tranny with less horses. My 5 speed berretta seemed like it was faster off the line.
[Modified by 81Vette_by_eric, 4:20 PM 10/21/2002]
Melting Slicks
Joined: Mar 2001
Posts: 3,365
Likes: 5
From: Lake Villa IL
Cruise-In IV Veteran
Cruise-In V Veteran
St. Jude Contributor
Re: MPG (81Vette_by_eric)
There were fill-ups, last year, when I was seeing over 20mpg. In fact, I once saw 24mpg. It seemed unrealistic enough, that I ended up posting the question here. I thought I was calculating my mileage wrong. I wasn't. It turns out that my feather light throttle foot, and lots of coasting, really did equate to the mileage I achieved. But the more aggressive I became, the faster my mileage dropped. I've seen 15 more than once.
I have yet to calculate the mileage, since my rebuild. But I expect it to be in the mid teens. I'm still in break in. Afterwards, who knows? :reddevil
I have yet to calculate the mileage, since my rebuild. But I expect it to be in the mid teens. I'm still in break in. Afterwards, who knows? :reddevil
Le Mans Master
Joined: Aug 2000
Posts: 6,362
Likes: 7
From: Brazos TX
Cruise-In IV Veteran
Cruise-In V Veteran
Re: MPG (81Vette_by_eric)
I consistantly get 14-15mpg and that is mostly highway driving (at 85 to 90 mph) and some city driving. It's tuned ok but not great and I have 3.73 gears. We'll see what I get with the EFI once it's on in a few months.
