I got between 25-29 US miles to the gallon with my 3.0L. That was calculating every fill up for almost 20000km. Running the Mafterburner and 72lb injectors.
Economy dropped slightly when I switch to 80lb injectors and LR Rogue Tune and Rogue ECU.....did not drive many km with the Rogue system.

 

no, high vacuum is going to be better. if you ever get a Uhaul they have a "mpg-ometer" thats just a re-faced vacuum gauge.
rpm does hurt mpg because of ring friction but all things considered its not a huge deal.


more throttle opening to minimize pumping loss (and increase efficiency) does work, it's in cases where you know you need X horsepower to cruise at Y speed. this is how automakers can get away with smaller displacement engines these days - engines are designed with higher HP/Litre, so for X HP you now need less litres...

 

3200 rpm at 70 mph sounds a little high. Are you sure you have a Turbo trans? Sounds like you might have the NA final drive.

 

Exactly. Not sure how any 944/51 is topping out at 110mph too? You sure you're changing into 5th gear.

 

Oops I meant high vacuum: I was visualizing the gauge reading lower and mistakenly wrote "less" lol

However, an auto journalist up here once described achieving better mileage during a rally race by intentionally loading the engine more (lugging), which of course meant low vacuum and more throttle. He figured the rings sealed better under load. Whenever I'm in Central America, I'm amazed how early everyone shifts, severely lugging their little Toyotas. Since economy is crucial down there, they must know something. But.. how those motors survive is beyond me!

 

I'm not aware of a 0.73 fifth gear set for these gearboxes. I do have a 0.78 gear set on the shelf, good used from a 944S2. PM me if of interest.

 

nope. Stock 968 gearbox is such that it has a higher rpm in 6th than the 951 box in 5th at the same speed. Crazy, no?

The argument is the 16v NA likes to rev, so they need a close ratio box, whereas the 951 makes all it's power mid range, so it likes relatively longer gears. I dont know enough to have an opinion on this, but it sounds plausible.

The proposed solution is to swap a gearset from a euro FWD 6 speed diesel audi into the 968 box. You will end up with a 1-5 that are similar to the stock 5 speed, and a 6th that is super tall (compared to stock). Google "200mph 951"

i have a non LSD 6 speed sitting in the basement. Will swap the gearset, one day.

 

 

True, the 968 gearbox has shorter gearing, mostly due to the shorter final drive. You can find the info here; https://www.porsche968uk.co.uk/Porsc...-Technical.htm

 

 

Find a 5th gear set from an audi 100 c3 diesel , 0.64