14.4 mpg

Scott77 · 07-29-2013, 07:21 AM

Took the car up north this past weekend. I measured 14.4 MPG overall, which included about 150 miles of freeway driving and 90 miles of side roads. Does this sound typical? 240 miles on one tank of gas seems light to me.
Scott
'78 930

Miguel Antonett · 07-29-2013, 07:40 AM

MPG depends entirely on how you drive the car... however, I'd say that "cruising" 300 miles per tank is adequate.

Shadetree930 · 07-29-2013, 09:11 AM

Yep, just about the norm for an unmodified example.

JFairman · 07-29-2013, 12:23 PM

Sounds about right to me.
I got around 9mpg on my last tank but thats from mostly around town stop and go driving and occasional boosted accelerations on the interstate. Havn't done any long trips in years.

Gas mileage sucks in the cars unless you're just cruising at steady speed on the interstate and only stopping to get gas and take a leak.
Thats mostly because of the low 7:1 compression ratio and turbocharger backpressure.

gsxrken · gsxrken's Garage

When I do strictly highway driving, I use 300 on the trip odometer in conjunction with the gauge to get gasoline again. My fuel gauge doesnt seem to act linearly as it nears empty so I'm a bit conservative with running to close to empty. (car is bone stock except headers and k27.)
Usually with all the goofing around its more like low 200s.

Noah930 · Noah930's Garage

I get about 14 mpg in my all-around driving. My car is stock. Even on events like the Targa California, where there's a lot of spirited driving, I'd average about that much. On the highway, I get about 20 mpg.

WPOZZZ · 07-29-2013, 07:31 PM

Quote:

Originally Posted by gsxrken

When I do strictly highway driving, I use 300 on the trip odometer in conjunction with the gauge to get gasoline again. My fuel gauge doesnt seem to act linearly as it nears empty so I'm a bit conservative with running to close to empty. (car is bone stock except headers and k27.)
Usually with all the goofing around its more like low 200s.

I use 125 miles as my gauge.

mark houghton · 07:38 PM

Advanced ignition timing and adjustable WUR works wonders on mileage....and performance when you need it. Highway cruising, I get around 20, but then who cruises just mundane highway miles exclusively? Beyond that, who cares :-)

fredmeister · fredmeister's Garage

Quote:

Originally Posted by mark houghton

Advanced ignition timing and adjustable WUR works wonders on mileage....and performance when you need it. Highway cruising, I get around 20, but then who cruises just mundane highway miles exclusively? Beyond that, who cares :-)

20mpg highway is damn good!

I just got about 90% done with tuning the adjustable WUR on my 3.4 liter with all the engine mods and did a long run up to Watkins glen last weekend for a DE event.
I saw 16.5 mpg all highway on the way up there with very little boost driving.

Dont know if I will ever get it back up to 20 mpg unless maybe running AF ratio on cruise up in the low 15's and running an open zork again.

Fred

turbo ride · 07-30-2013, 10:31 AM

Well I just did a 1500 mile road trip over the week of 4th of July - and although MPG is not at the top of my priority list I did track it. I did a combo of Interstate and US Highways. Typical Interstate speeds of 85-100 (sometimes higher, sometimes lower for constructions zones) and US highway speeds around 80. Some slower back roads, too. I got 24 MPG overall. Car is a 964 Turbo and I do have a BL WUR - cruise was set around 14.5 however my car's O2 sensor is hooked up and at RPM under 3000 I believe the O2 corrects it to stoich regardless. But not 100% sure how it works (yet - still learning).

I get about 17.5 around town with mixed driving. I was hoping to get 20 MPG on the trip - so I was pleasantly surprised. Tires are also 285/35 in back - effectively gearing the car even taller which may have helped???

JFairman · 07-30-2013, 10:42 AM

How big is the gas tank in a 964 turbo? You have different gearing than most 930's with the 5 speed too.
24mpg from one of these cars is unbelievable unless you're going down hill.

ficke · ficke's Garage

I get single digits around town and on the high way 12-15 MPG.

Tires on the rear last maybe for 7,000 miles and I change the 15 quarts of synthetic oil every 6,000 miles. The cost per mile in consumables is high.
My engine has 78,000 miles on it since being rebuilt into a twin plug 3.4L . The car also has a not very deadly dial a death knob.

quattrorunner · quattrorunner's Garage

With a 915 I got about 22 mpg one full tank trip but I was really trying hard on that trip to save(drafting semis, coasting long downhills, driving off boost as much as possible etc).

turbo ride · 07-30-2013, 01:27 PM

Quote:

Originally Posted by JFairman

How big is the gas tank in a 964 turbo? You have different gearing than most 930's with the 5 speed too.
24mpg from one of these cars is unbelievable unless you're going down hill.

Yeah I was very surprised. I started my trip with 1 mile on a fresh tank - saved every gas receipt - and got home and immediately topped up the tank to get back to my "zero point" so to speak. 1496 miles, 62.19 gallons. I'm pretty sure the 964 T has a 20 gallon tank (off memory) and yeah revs were right around 2900 - 3200 a lot IIRC. In 5th that is around 90 ish.

Must be the aero mirrors :-)

Tom F2 · 07-30-2013, 01:32 PM

Do the SC cams lead to worse fuel mileage than the stock 930s, all else being equal?

JFairman · 07-30-2013, 02:41 PM

revs were right around 2900 - 3200 a lot IIRC. In 5th that is around 90 ish.

At 3000 rpms in 4th gear my '87 930 speedometer says 80 mph. That tells me the stock 930 4 speed and final drive gearing is not going to give as good gas mileage as your 964 turbo's gearing.

I have 315/30 x 18" rear tires and that diameter tire has some effect on final drive gearing.