If I remember correctly the viper 6 has fifth and sixth as overdrives - that's a HUGE help and the computer control is better. But don't hold your breath hoping for 17 with your foot down in the under gears. I don't think I was being BS'ed when an owner with the gear vendor od mated to a NV4500 5 speed (2.26 final in double over with 3.90 rear) said he gets 15 at best avg - all around (just cruising at 70 in 2 x od, his readout on the dash says 19 but it drops to 14 just to go decently up 5 mph - and each 5 mph lowers instant eco by about half an mpg). 5000 lb weight (49 chev sedan).
When he plants his foot in it from a stop - the "instant eco" display from his onboard drops to 6 and slowly comes up to 10.
But the questions begs - if you can afford the efi rj502 and viper 6 - what concern is fuel economy? lol
Yeah, the Viper 6-speed has a 0.5 overdrive 6th gear (0.75 in 5th) so a 4.10 rear gear would be like a 4-speed with a 2.05 rear gear.
That's a heavy 49 Chevy! I expect my Nomad to be under 3600 pounds.....hopefully
. That will help.
I'm not "concerned" about fuel economy, it's just kind of a challenge to see what I can get with it. I'm using a Holley Commander 950 ECU so I can program it to do what I want within the constraints of the software. I'm not sure what all is possible, but I have added a knock sensor, and a wideband O2 sensor upgrade for tuning.
I know my right foot will largely control MPG
, and I tend to play around some around town. But if I want to travel longer distances, it's nice to know my mileage is going to be reasonable, not 8-10 mpg. I built a 23+ gallon fuel tank that I now think may be slightly overkill.....:sign0020:
I had a 55 Chevy with a carbed Corvette 427 and Muncie with a 4:11 rear and I actually measured around 17 mpg on a long trip to Kansas in the early 70's. I don't remember my speed, but that was before the mandatory 55 MPH federal speed limit. I think it was 70 MPH. However, I don't believe I ever corrected for the speedo error with the 4:10 gears. I think I was still getting at least 14.