20% + increase in fuel mileage!

[SquareRoot]

Ok so I never did an actual scientific study to get "exact" details but here's what I've discovered.

Six months ago my 85 K20 had a vortec 350, 1406 carb, turbo 400, 4:56 gears.

Now it has vortec 350, ram air, Edelbrock Pro-Flo 4, NV4500, 4:56 gears.

One round trip to work and back is 61.7 miles.

Before the change, I could drive four days on a full tank (20 Gallon) of gas.

Now I'm making it all week (5 days) and when I fill it up it takes 18-19 gallons.

I'm not good at math but that extra day equates to about 20% no?

YES-it's a lot of cash up front and YES it starts and drives like a new modern vehicle.

Carry on.

 

[DoubleDingo]

Yeah, lower rpm's equals better gas mileage, as long as the engine's torque band is correct for the cruise rpm's. Your final gear is now 3.33 in OD. So the 27% reduction in rpm's has netted roughly 20% increase in mpg's, not bad.

 

[80BrownK10]

Just give us the miles (which you did) and the amount of gallons you use to add for the tank after 4 days unless it was equivalent to what you said you out in after 5 days and I will easily do the math and give you the increase %

 

[Ricko1966]

Ok so I never did an actual scientific study to get "exact" details but here's what I've discovered.

Six months ago my 85 K20 had a vortec 350, 1406 carb, turbo 400, 4:56 gears.

Now it has vortec 350, ram air, Edelbrock Pro-Flo 4, NV4500, 4:56 gears.

One round trip to work and back is 61.7 miles.

Before the change, I could drive four days on a full tank (20 Gallon) of gas.

Now I'm making it all weak (5 days) and when I fill it up it takes 18-19 gallons.

I'm not good at math but that extra day equates to about 20% no?

YES-it's a lot of cash up front and YES it starts and drives like a new modern vehicle.

Carry on.

That is one weak week mine are 7 days. LOL.

 

[dvdswan]

OD certainly makes difference.

 

[Bextreme04]

It would have been interesting to see how much of the overall mileage was from the NV4500 and how much from the pro-flo individually. I'm assuming both changes were made at the same time?

 

[Frankenchevy]

Sweet! 16+ mpg

I can’t remember, what size tires do you have?

 

[SquareRoot]

Sweet! 16+ mpg

I can’t remember, what size tires do you have?

Stock K20. 31 inches.

 

[SquareRoot]

It would have been interesting to see how much of the overall mileage was from the NV4500 and how much from the pro-flo individually. I'm assuming both changes were made at the same time?

I would guess more of it was from the OD as 90% of the drive is highway miles.

 

[Frankenchevy]

Gotcha. So that combined with 4.56s versus my 33” tires with 3.73s. I’m curious what mine will get.

Somewhere in between my freeway rpm and yours is probably what’s optimal at our torque output.

 

[Bextreme04]

I'm sure the OD is a huge part of it.. but I would think the EFI could be good for at least 5% of that. If nothing else the cold start performance and lean cruise should be worth at least that. I know I see a few MPG difference depending on how cold it is outside and how long I need to let it run on the choke to warm up before driving.

 

[Bextreme04]

Honestly I'm impressed you were getting 12.5mpg on the carbureted 350/400 combo. I'm lucky to get 8-10 mpg with 350/TH400/NP205, 4.10's, and 35's. My engine is definitely tired and hurt though, which is probably a big part of it. I would be thrilled to get 12-16mpg from the new MPFI 454/4L80e/205 combo... but I'm not holding my breath.

 

[Ricko1966]

Gotcha. So that combined with 4.56s versus my 33” tires with 3.73s. I’m curious what mine will get.

Somewhere in between my freeway rpm and yours is probably what’s optimal at our torque output.

I forget, which one of you is the stalker?

 

[Frankenchevy]

I would be thrilled to get 12-16mpg from the new MPFI 454/4L80e/205 combo... but I'm not holding my breath.

I wouldn’t either. The 8.1 would be hard pressed to get that in a factory truck.

I forget, which one of you is the stalker?

the role has flipped a couple times along the way. It’s kind of ambiguous like that...

 

[Bextreme04]

I wouldn’t either. The 8.1 would be hard pressed to get that in a factory truck.

Well, the 8.1 is a notorious gas hog too.. it's hard to find the same aftermarket parts and they are way pricier than the older BBC stuff. Hopefully being able to tune everything myself and having improved parts helps out. There's a bunch of people that have done the 0411 conversion on factory GMT-400 454/4L80e combo's and had good results into the 14mpg range.