fuel economy tips, anyone?

jfw834 · jfw834's Garage

I was wondering with 87 oct. gas up to around $40,000/gal these days, does anyone with a CIS injected (or any 911) have tricks to up gas mileage?

i have heard that in modern cars, the engine actually uses no gas at all to keep running if you coast to a stop while IN GEAR, and it DOES use a bit if you take it out of gear and coast to a stop in neutral. (the engine needs a bit of fuel to keep it from stalling) I am thinking that this most likely does not apply to 911s of our vintage, but does anyone know which is more economical for us?

jeremy clarkson did an 800 mile trip on one tank of gas in an A8 and thats where i got the above info about modern cars....it seemed to make a huge difference for him as he was getting well about 40mpg in a V8!

anyone have any advice?

nostatic · nostatic's Garage

drive downhill everywhere

theFONZ · 08-22-2005, 02:17 PM

or drive in reverse

sammyg2 · 08-22-2005, 02:46 PM

Buy oil company stocks. That way when you pay more for gas, you will actually like it

Hay it works for me.

svandamme · svandamme's Garage

let it rust through the floorpan, and run it like Flintstone did

svandamme · svandamme's Garage

btw. Clarckson did it with a V8 Diesel, i doubt he would have made it with a V8 Petrol engine

LakeCleElum · 08-22-2005, 02:57 PM

If it's really that important to you, change to higher gearing with larger tires....

svandamme · svandamme's Garage

as for CIS using fuel if you coast in or out of gear
it think it won't matter one bit

CIS measures fuel based on one thing only : the metering plate
if the meatering plate isn't moving ( which would be the case with throttle valves shut), the idle delivery is on

doesn't matter if your engine is running idle revs, or is in gear coasting from 5000 to idle revs... more or less the same amount of fuel get's delivered , the engine might suck a little bit harder, but it's not going to suck the fuel out of the injector nozzles...

at least that's what i'm guessing

nhromyak · nhromyak's Garage

Indeed, chevy started to shut off the fuel when the vacuum and rpms were newer engine'd cars (from 91 with the Chevies) shut off the injectors when some things were in place, or were at a specific range (e.g. in gear, slowing down etc.)

I suspect you are already getting 24+ hwy mileage correct? If not, it's time to see why you're not.

Good luck.

FrayAdjacent911 · 08-22-2005, 03:29 PM

For some real tips... read on:

This is not Porsche specific. I drove a Honda Insight for a year or so, and that car REALLY lets you know what does and does not give you better gas mileage!

Maintain your engine! Change the oil and filter, and air filter regularly. Keep it clean, run some fuel injector cleaner once in a while.

Check the alignment! Also related, check your tire pressure every couple weeks. Run your tires at a little higher pressure to reduce rolling resistance. (careful if the vehicle is under load)

Get up to speed quickly (but not insanely!) and maintain a constant speed. Avoid speeding up and slowing down. Drive in the highest gear possible to keep the revs low and the throttle low.

Use the correct grade of fuel, but do not use higher grade. You get NOTHING out of using higher grade gasoline than your engine needs.

Border911Dude · 08-22-2005, 04:35 PM

Quote:

I suspect you are already getting 24+ hwy mileage correct? If not, it's time to see why you're not.

My '79 SC doesn't get anywhere near that... where do you start looking? (The neighbor kid who's stealing gas?

)

FrayAdjacent911 · 08-22-2005, 04:37 PM

one more thing... remember, the biggest thing that can affect your gas mileage is

YOU

hcoles · 08-22-2005, 04:44 PM

This is working very well for me. I stay home and work on house, garage and garden projects along with watching SpeedTV. I find that if I don't leave the house I don't spend much money. This lets me save up for AX tires and gas to get to the AX's and back. ;-)

Tooth911 · 08-22-2005, 04:59 PM

Ive gotten as high as19mpg in my 77 911 with a2.8L Ecam 9.5cr webbered motor. A good tune and carb adjust on the lean side.This is freeway 56mile trip to work roundtrip lot of stop and go.

anthony · 08-22-2005, 05:10 PM

I wonder if CIS can be tuned for good mileage? I get on average 18 or 19mpg, as low as 16mpg if I'm lead footing it, and probably as high as 22mpg on a pure freeway trip under 70mph.

I ask if it can be tuned for good mpg because I notice a lot of other SC owners reporter much better mileage.

KobaltBlau · 08-22-2005, 05:22 PM

Grady Clay has some tips on this, he told me he optimized his 911 for fuel economy during the "first fuel crisis"

FrayAdjacent911 · 08-22-2005, 05:35 PM

Kobalt, I had heard someone mention that, too. He tuned his carbs and got great gas mileage, but it didn't run very well!

And maybe some of us with older cars could remove the engines and swap in a VW 4 cylinder power plant... hehehe

Milu · 08-22-2005, 11:26 PM

Convert your car to run on lpg or methane as well as petrol.

A couple of 993s were converted to lpg in Rome but I am sure there are others. Biggest problem is location of the tanks - either in the boot or under the car.

chaf · 08-23-2005, 02:05 AM

I've been paying attention to MPG for a year or two now (stupid hippie conscience). Things that have made the biggest difference for me are:

1) Keep revs as low as reasonably possible (i.e. shift early) - the slower the engine is turning, the better the mileage it delivers. Obviously don't lug it, though.

2) Drive as slowly as reasonably possible on the freeway. I don't mean put on the granny wig and go 52, but I find that running 70-75 typically burns about 10-15% less fuel than running 90-95.

3) Use cruise control or, if you don't have it, try to drive the car as if it had cruise control.

4) Back down and look ahead. If you're not tailgating the guy in front of you, you can anticipate what traffic is going to do and make smaller speed corrections earlier while staying in the flow.

The two biggest things that hurt gas mileage are going fast and changing speeds - unfortunately two of the things that a 911 does best.

Everyone has to find their own balance. I made a deal with myself - I just burn as much gas as I want at the track, but then I do everything within reason to conserve the rest of the time. It only feels weird for the first month or two.

Oh, jfw834, on my '78SC, back when it had CIS, the best mileage I ever saw was a little over 19 on the highway, and the worst was a little under 16 - so you're not the only one...

livi · 08-23-2005, 03:52 AM

With the ridiculously cheap gas in US I wouldn´t think twice about gas mileage.

Chaf, you sure about the cruise control part ? Its set to a fixed speed meaning more gas uphill. Wouldn´t you get a bit better mileage keeping constant throttle going uphill ? Of course you will loose a bit speed but the consumption does not rise. No ?