blown 87

I never would have guess this, but after 3 tanks of fuel with the 2:73 5 speed I have picked up on average 2.5 MPG

I was really worried about it just killing the gas mileage around town, so I am a bit shocked that going from the 2:20 auto to the 2:73 5 speed got better mileage.

I was getting around 15 with the auto, now I am about 17.5.

pleasant news.

The real test will be my first highway drive of a full tank at speed.
The auto would get 20, we will see what the 5 speed does.

dprantl

On the highway you will get 22.5 - 23mpg with the 2.73 5-speed, so you will have similar gains there too. Going from a 2.73 5-speed to a 2.2 5-speed should gain ~2mpg both city/highway. Sterling, how do you plan to put a 2.2 into a 5-speed with PSD? Or did you do a PSD delete?

Dan
'91 928GT S/C 475hp/460lb.ft

blown 87

I could handle a increase in mileage on the big road.

GregBBRD

I'm pretending that all three of you guys are driving a 928, in the first place, for the fuel ecconomy....this is kind of like Eric Clapton being excited about discount guitar strings....

blown 87

I was expecting really low numbers, so yea, pretty happy with it.

I keep track of the mileage because it can show trends, let me know if something is not quite right, or has changed.

But you are right Greg, we do not drive these cars for saving money.

blown 87

Did you not get something like single digit numbers going to SITM 2 years ago?

Rob Edwards

When Jim and Sue Corenman drove down to SF10, they were making a 'road trip' Sharktuning map in the block of cells where they cruise at 65-80 mph. I forget what AFR they were shooting for, but IIRC they could lean it out to 15.5 or 16 and get upwards of 24-25 mpg, on a GT where you're turning 3K at 80 mph.

James Bailey

Why do automatic transmissions need coolers ? Where does that heat come from ? It eats horspower from the engine and turns it into unwanted HEAT. Now changing from a final drive of 2.7 to a 2.20 is NOT going to change the city driving MPG by much at all because you are never going to be in 5th gear putting around town, with a manual trans YOU select the engine RPM ALL the time in the lower gears reguardless of the final drive ratio. On the highway the "overdrive effect" of the taller final drive will reduce RPM and should yield better MPG but driving style has far more to do with MPG than anything else. And using the cruise control is less efficient than careful use of the loud pedal because the cruise brain pushes too hard in an effort to hold a very constant speed. And the quickest way to greatly increase MPG is simply slow down..... never mind wrong forum

GregBBRD

Now we are talking....more people worried about gas mileage, in their 928!

$4,000.00 worth of computers, Sharktuners, and instuments hooked up to an almost perfect 928, looking for another couple of mile per gallons....that makes sense!

Jim could save more money picking out a cheaper wine to have with dinner....

Heh, I get this...and you all know I do the same thing...I'm just teasing you guys.

You have to admit, it is a funny picture!

JWise

If you had the engine monitoring capability (EGT for example), along with the Sharktuner, could you run one of these engines lean of peak (LOP) like the piston powered aircraft guys do? That seems to be the method for best range in the air. Just wondering...

James Bailey

And 928s with big wide great looking tires ......too funny

RKD in OKC

I thought transmission coolers on any auto transmission was because of the heat generated by the torque converter.

GregBBRD

The torque converter is slipping all time our 928s are moving, reducing efficiency. Our converters do no lock up.

dprantl

It is pretty hilarious that the two out of the first three posts on this thread are by 928 owners with greatly increased power I love my 928, and I try to drive it as much as I can. In that light, I want it to do everything, but of course there are always trade-offs. Ideally when I'm not punching it, I would like to get ok gas mileage. This is especially true of anyone who daily drives a 928. And yes, I think I could get close to 30mpg on the highway if I set my cruise map lean with the ST2. I can go to ~18:1 and it will still be smooth.

Oh and Jim, in "economy mode" with my '86 with the 5-speed 2.2, I would be in 5th gear at 25mph already.

Dan
'91 928GT S/C 475hp/460lb.ft

dprantl

Right. Hence the reason why modern cars now have torque converter lockup in any gear almost immediately off idle. The result is that the auto versions of the same car can even beat the gas mileage of the manual versions.

Dan
'91 928GT S/C 475hp/460lb.ft