Fuel Economy of the 928?

cNicely · 05-24-2007, 07:31 AM

What kind of gas milage do 928s get? Preferably the 4.7 L's

Danglerb · 05-24-2007, 11:14 AM

Maybe 16 mpg in town, maybe 22 mpg or so on the highway even at 80 mph. 23 gal tank so you still don't have to visit the pump too often.

928's aren't cheap to drive, the first time you have a major service done you generally stop even thinking about the cost of gas. Its smiles per gallon that counts.

cNicely · 11:48 AM

wow, didnt know it was that

Danglerb · 05-24-2007, 12:40 PM

No different really from any similar sized V8 of the time. Newer models about 1990+ squeeze a bit more mileage out of a gallon of gas. I've heard of one 928 converted to diesel in the UK, and somebody has converted one to electric with batteries.

I think Honda has a diesel coming out that is like 60 MPG.

Red Baron · 05-25-2007, 02:43 AM

I've gotten 20+mpg on the highway doing 80+ the entire time. Only mod to the car was headers and no cats. The 928 is pretty good on gas on the Hwy.

OldTee · 05-25-2007, 08:52 AM

Winter not much driving and w/o checking tire pressure. 13MPG. Spring chores accomplished and tire pressure set at book figures 16.8mpg around town.
Moral
At $3.50 per gallon (or so) pump up the darn tires.

Danglerb · 05-25-2007, 11:42 AM

Its not so much the pump up as light up the tires.

I have fond memories of one tank I got 6 MPG on (other car). I decided the old tires had to go, so might as well go up in smoke.

m21sniper · 05-25-2007, 02:48 PM

my 4.7(or stroked?) gets about 8mpg.

cNicely · 05-25-2007, 05:54 PM

8? wow, do you drive a little crazy or is that just average crusing

Danglerb · 05-25-2007, 06:08 PM

I don't think anybody would say I drive a "little" crazy. Most passengers just grab onto something and make funny noises until we stop. Why own a Porsche if you want to drive like grandma?

I try to be polite to other drivers and not present undue hazard to anyone else, but my right foot doesn't hear very well.

m21sniper · 05-25-2007, 10:58 PM

Quote:

Originally posted by cNicely
8? wow, do you drive a little crazy or is that just average crusing

I pretty much drive it like i stole it.

mtelliott · 05-29-2007, 08:06 AM

So, do you have to run premium grade?

I know that on a lot of the older high end cars, they required premium from a marketing perspective, not an engine perspective. The thought was that people who bought high end cars expected to put premium gas in and felt less of the car if it could run on regular gas (i.e. the engine wasn't built for performance). It's all about the marketing.

Michael

Danglerb · 05-29-2007, 12:06 PM

Stock US motor is 87, Euro and boosted cars want premium. Early cars don't have knock sensors, I don't know when they started US 85 or 87 I think, and I am not sure on this, but in American cars when the knock sensor was added the motor would either automatically or via a switch take advantage of the premium gas and increase timing advance.

With the funky way and mixes in modern gas I would say stick to what works and use the lowest octane you can.

m21sniper · 05-29-2007, 01:25 PM

Quote:

Originally posted by mtelliott
So, do you have to run premium grade?

I know that on a lot of the older high end cars, they required premium from a marketing perspective, not an engine perspective. The thought was that people who bought high end cars expected to put premium gas in and felt less of the car if it could run on regular gas (i.e. the engine wasn't built for performance). It's all about the marketing.

Michael

I run 50 degrees total advance. Premium is not really optional.

Danglerb · 05-29-2007, 03:19 PM

Knock when detected retards timing, but the inclusion of knock detection allows a more aggressive baseline and advance curve to start with.

rhjames · rhjames's Garage

octane requirements depend on several things, not the least of which is compression ratio (of which there were many depending upon which year, Euro or US, 16V versus 32V, etc)----my Euro is 10:1---- and how much timing advance you care to tune in.....or not.

turbo's, supercharging, and even the quality of fuel have an affect on engine octane requirements and performance results.

-----

rhjames · rhjames's Garage

as for fuel mileage numbers------

my 1980 Euro with CIS mechanical injectors gets about 16/17 mpg around town (if I behave with it), and 26 mpg on the highway running 65-70 mph.

it's a great thing.....

hacker-pschorr · 04:52 AM

Quote:

Originally posted by Danglerb
Maybe 16 mpg in town, maybe 22 mpg or so on the highway even at 80 mph. 23 gal tank so you still don't have to visit the pump too often.

Depends on what transmission. All things being equal a 2.75 or 2.73 OB 5-speed is going to get worse gas mileage than a 2.20 equipped auto. My 81 will max out around 17mpg on the highway. I'll be swapping in a 2:20 soon. Tim Murphy's supcharged shark will average 21mpg on the highway.

Quote:

Originally posted by Danglerb 928's aren't cheap to drive[/B]

Compared to what? I find my two very inexpensive to own compared to almost any other performance car on the road. It's not accurate to compare them to a civic.

hacker-pschorr · 06-01-2007, 04:51 AM

Quote:

Originally posted by Danglerb
Stock US motor is 87, Euro and boosted cars want premium. Early cars don't have knock sensors, I don't know when they started US 85 or 87 I think, and I am not sure on this, but in American cars when the knock sensor was added the motor would either automatically or via a switch take advantage of the premium gas and increase timing advance.

It's also generally believed the 87 octane rating and low factory advance on the US OB's was to please the fuel conscious. Has absolutely nothing to do with knock sensors. The 84-85 EuroS 310hp cars do not have knock sensors.

As for the S4's, knock sensors do not "advance" timing when better fuel is sensed. The car has no idea what fuel is in the car. You make it sound like the car keeps advancing until it senses knock. Not true at all. There is a baseline map the car will hold until knock is detected. If you are driving on a cool day the car may be able to run full advance on 87 octane. Then again a 110 degree high humidity day 93 octane may not be enough for very aggressive driving. Using the Shark Tuner we have seen many stock S4's on high octane gas knock. Not much, but it's there & the engine is reacting accordingly (sniper, just an FYI, the plugs on these cars are 100% clean, you cannot always detect knock on the plugs). If you pour in 105 octane race gas, an S4 isn't going to suddenly crank up the timing - it's going to be on the same map as 93 octane.

Quote:

Originally posted by Danglerb
I think Honda has a diesel coming out that is like 60 MPG.

VW already does - has been proven in a few independent tests, including a friend of mine (100+miles per day) who has been driving one for a few years now.

Danglerb · 06-01-2007, 01:05 PM

Isn't the baseline S4 timing map more aggressive than earlier models? As I read it the 85/86 US models left a LOT on the table for AA chips to improve, and almost nothing with the S4 and up.

RE "928's aren't cheap to drive"
Its a lot easier to name the handful of cars that are more expensive to drive, all similar high performance exotics.