Cole

I was talking to a friend this morning about 951 fuel mileage. There are at least three of us locally that commute in them, most of that at highway speeds 65-75mph.

We were strategizing what could be done to a 951 to make it a higher fuel mileage commuter. Let's be honest, it would be cooler than driving a cheap old Honda just because it got a few mpg better


What are your thoughts?

JohnKoaWood

Lean it out at lower throttle positions / when off boost.. fuel mileage will go up.. properly instrument the car to make safe changes, and you can see huge gains in fuel economy durring normal highway cruising!

Custom tuning is the best option to maximize power / torque and fuel economy.. but this takes some $$, time, and effort...

Keep boost at a reasonable level (more boost equals higher fuel consumption to maintian good AFR).

When I was daily driving my 951 as a commuter car I was seeing mid to high 20s at 15PSI boost.. with a little tuning I probably could have seen north of 30 MPG but I liked having the power on tap.. putting my foot in it would easily make the economy drop into the low teens!

My 944 DD CAN manage 30+MPG on the highway if I keep the speed down and my foot out of it on accell. I will soon be trying to find the limits with the 944 as it is eventual project to tune it for max economy.. but as of right now it is just running the factory chip.

Paulyy

My thought would be higher compression. i think stock is 8:1 increase it to 8.5:1 or 9:1 so you don't have to mash your foot to the floor to pick up speed on low rpm?

Then you would need to run higher octane, which costs more.

Cole

The basic ideas we had so far....

-NA 5th gear for a lower rpm highway gear.
- "lower rolling resistance" tires like they put on some of he new cars and hybrids.
-GTS style lights for night/early morning commutes.
-Lighter parts. (hood, sunroof, seat delete, rear bumper, hatch, wiper rear delete)
-Aero thingy that covers the front wiper blades
-flush mount things like door handles, more aero mirrors.

CDH-CTT

I used to drive 60 miles a day with my 951.... it is possible to drive the car and build little to no boost and it still been able to move through traffic. I was getting 28 mpgs and 26 with a/c on (its hot here in Az).... I agree with the RIGHT driving habits and tuning a 951 can be a very good DD...

Cole

How high do you guys think we could go?

Tedro951

Google "hypermiling" The sky is the limit...

86 951 Driver

I got 27-28 MPG all highway. The car did great. I also used cruise which is a big help on the highway. But having a little high compression would help. Just need to adjust boost accordingly.

JDS968

As far as maximizing mileage while cruising on the highway...it all comes down to what RPM range you're cruising in, and how much boost you're making.

Normally you try to set up a turbocharged car to build boost as low in the rev range as possible. However, when you're NOT developing any boost, you're essentially driving a small, low-compression 4-cylinder, which means little power but excellent mileage. Of course, you don't NEED power if you're cruising at a steady speed.

I think it might be useful to have an adjustable boost control system, whether it's electronic or mechanical, so that you can completely open the wastegate and eliminate all boost for cruising on the highway. Then when you want power again, simply switch to your normal boost strategy, and you go from driving an economy car to a sport car.

V2Rocket

taller tires go a long way

biggest factor is your foot

Cole

Gearing(tall tires, etc) only help to a point. Run too low of an rpm and you are lugging the engine and out of it's efficency range and using more fuel, not less.

All of this is also assuming that the drivers foot is a constant factor. We are talking about what to do to the car, not the driver.

JDS968

Don't get me wrong, I'm not suggesting that you set your car up to be running at idle at cruising speed (not that it would even be able to hold speed, most likely). My point was mostly that if you develop boost starting at, say, 2500 RPM, and you're cruising at 3000 RPM, you could likely gain significant mileage by adjusting your gearing to drop your revs below 2500 or by changing your boost control so that, when you want to, you can drive at 3000 RPM without boost.

docwyte

Thought you were DD the Cayenne?

blown 944

I'd say an early Na 5th gear would be a big help for highway driving. I have been able to achieve 28mpg on E85 by using aggressive timing and very lean fueling. I can feel it surge at times bit not too bad. You could play with the timing and lean it down as fat as possible for very low load conditions.

When I was driving my early Na without the blower I saw over 30 mpg often on highway trips. I don't see why you could not achieve similar results with a turbo if using the right combo.

Cole

I do. I have 2 friends with 951s that commute from Colorado Springs to Denver everyday.

I have been driving my 951 more just because it is nice out. But I also have 4 motorcycles to choose from in the nice weather.

Just a fun topic on how to make the 951 a great MPG hauler.