Viken

I was just wondering how significant the effects of an EFI upgrade on MPG are? Just thinking about an upgrade, and I'd appreciate it if anyone who has done an upgrade from carb to EFI could post some numbers. Thanks.

:)

zwede

My city mileage went from 10-10.5 to 12-12.5. About a 20% improvement.

Racer16k

Well I don't have any comparison numbers, but I get 18mpg on the highway with 4.56 gears and a 700r4.

nitrocharger

Went from 14mpg to 17 mpg, 3.08 rear, your results may vary :lol:

LAvetteman

That sounds right to me. Add another 3-5 mpg with an overdrive tranny and cruising gears. (3:08-3:36)

SuprJames

20+ mpg on the highway with 3.55's and a 700R4.

mrvette

I had a previous owner rebuilt mild cammed L48 engne and muncie 4 speed in my'72 with a 336 rear.....got 12-13 on highway and not so good around town either....

when doing nothing more than adding serp drive, and electric fan, aluminum radiator....and the L98 stock injection with closed loop and stock type programme chip without EGR and AIR and a few other things...the car jumped to 24 mpg in highway, and about19-22 around town....
these were real world figgers....

Down here in Florida some years ago I went to upgrade to a more powerful engine, and so adding ~150 some odd hp and the overdrive tranny....I now get about 20-22 on highway and 18 or so around town....still much better than any carb'd C3 I know of personally....

GENE

PatsLs1vette

i also get 20+ mpg ,700r4 ,3.70 gears .510 roller cam,sportsman 2 heads,2100 stall.

markdtn

I get about 18 city and 23 highway, 350 TPI, 700R4, 3.70 gears

Zack Wenning

I would like to hear from more guys with the edelbrock/holley/accell units because I dont think TPI has the potential to make enough power for me. Thanks

zwede

Well, mine is a Holley commander 950. See above for my mileage figures.

Viken

Thanks for all the posts guys. Really appreciate it. That's probably enough of a difference to make EFI just about a requirement for me I suppose, with the Vette being driven daily anyways.

mrvette

Zwede, are you closed loop??? sounds like something is wrong there, only 20%??? and the lo figger amount says somehow you either got one HELL of a large engine there, or running way rich....

GENE

zwede

I'm closed loop. Keep in mind I have a 454. Compared to a Viper I'm doing OK. They're 488 cui, about the same power and get 10-11 mpg city. My city mileage is true city mileage... No highway at all and plenty of stop & go with AC on. My 96 Z28 got 16 mpg for the same driving.

LAvetteman

If you are getting 10-12 mpg in solid city driving with A/C in a 454 that I am sure runs very nice 1/4 mile times, I say that is a MAJOR improvement!!!

LAvetteman

How well does it do in OD???

zwede

Mine? Dunno, haven't driven a whole tank on the freeway yet. Before the OD, but with EFI, I got 15 mpg on a tank with 50% freeway, 50% city. I figure I ought to be awful close to 20 mpg now...

mrvette

No question higher powered cams really do cost fuel, even with DPFI, which for any given displacement is a bit surprising to me,.....

but if you get 15 mixed, and 20 on the freeway, with a BB...man that's pretty good really, hell I only gat 22 or so now on the freeway, and mine is 355 ci...

Thing is, I was getting 24+ on the freeway with my original rebuilt engine and the muncie....and now with lockup cnverter and same rear gears...but hotrod engine it's about 22, and that huge difference is the engine in spite of the o/drive....
with that experience it seems the only reason for o/drive is engine wear and tear, can't justify changing over for fuel reasons....even at 2 bux/gallon...

Well life is a bit quieter too.....

but if you can get 20 with a BB and NO o/drive....hummmmmm.....

well maybe someday....

GENE