Fuel Milage ?

Trexx · 08-27-2005, 07:49 AM

Ive got a 73' 914 with a 1.7. Im getting right at 20 mpg. Thats mostly country road milage, about 60 mph tops, and not much stop and go. Seems to run fine. Someone told me that he used to have a 914 and got like 32 mpg. Is he pulling my leg? I do have what I think is called a Monza exhaust which one mechanic one time told me was very restrictive. Im wondering if that has something to do with what kind of milage Im getting.

Trexx · 08-27-2005, 01:17 PM

Wow I cant even spell MILEAGE DOH. I wanted to add that this is a stock motor with fuel inj.

hardflex · 08-28-2005, 05:55 AM

if it's fuel injection, you should be getting much better, around 30mpg i think. Some things I would check and correct....

Firing on all four cyls?
Spark plugs black and sooty? All of em, or just 1 or 2?
MPS Vacuum test passes?
Cold start enrichment valve leaking?

goose2 · 08-29-2005, 10:42 AM

I got as good as 32 with my old 1.7 w/ D-jet FI. The problem with D-jet is that just about anything that's not quite right with it will make it run richer.....vacuum leaks anywhere, intake runner boots, MPS, TPS, CHT. My mileage sucked until I tested and brought everything up to specs. It can get tedious but worth it.

Bleyseng · Bleyseng's Garage

I get about 26-28 mph on my 2.1L with Djet. So there is something wrong with your fuel system. Check to see if the MPS holds a vacuum.

Geoff

Special K · 08-31-2005, 02:03 PM

No BS. When I drove my new acquired '74 2.0L (D-Jet) from Chicago, to St. Louis, I averaged between 48 - 50 mpg!! Think it was running a little lean?

I think 30mpg is not an unreasonable mpg for a 2.0L in good shape.....something definitely amiss with yours.

Barber Dave · Barber Dave's Garage

Hi. I converted to 2 webers ( 34) single barrels. The last two tanks were 37 & 39 Mpg. Thats at 75 to 80 miles per hour.
Also it still has the F.I. cam . Dave

Trexx · 09-11-2005, 05:02 AM

Thanks for all the suggestions guys. How do I go about checking the MPS?

Dave at Pelican Parts · Dave at Pelican Parts's Garage

Use a vacuum pump with a gauge (e.g., the MityVac hand pump) to pump it up to about 15" of vacuum. If it leaks down in less than 5 minutes, you have a problem. If it doesn't leak at all in 15 minutes, it's just fine.

For your D-jet information needs, see http://members.rennlist.com/pbanders .

--DD

Trexx · 09-11-2005, 06:38 PM

Thanks Dave, I appreciate the advice.

Will98D · 09-13-2005, 07:42 PM

I get about 120mpg, and I park it next to my '70 Caprice 350 with the only surviving 80mpg carburetor that the Feds, Oil Companies and Big 3 didn't destroy... but don't tell anyone.

Oh we've opened a can of worms now. I seem to remember a lot of pissing matches a couple of years ago about who got how much mileage, and other people calling them out as full of shazit. If a Toyota Echo (2035 lbs, 1.5 liter, 108hp) with a modern engine and far superior engine management system can be rated at 35 city / 42 hwy then something in the low 30s seems reasonable for our 914s.

bottomend · 09-14-2005, 10:20 AM

Please tell us more about your carb. I've always heard of this 80 MPG piece but I dont know much about it.

ken_xman · 09-14-2005, 11:37 AM

Will is kidding.
I did have a 84 Sentra Diesel that got 56MPG, on its best tank.

bottomend · 09-14-2005, 02:08 PM

Will Will keep kidding? Or will Will give up kidding, God willing?

goose2 · 09-14-2005, 02:55 PM

All this talk of fuel economy make me wonder what would be possible if one wanted to maximize a 1.7 for best gas mileage. Different cam, induction, tall tires, aero improvements?

Dave at Pelican Parts · Dave at Pelican Parts's Garage

Yes.

You'd do all of those, plus go with aftermarket EFI, plus put lots of very trick coatings on the engine internals, plus you'd go through the oil system and everywhere in the engine that air has to move and help optimize that flow...

A good high-quality exhaust would be mandatory.

If you didn't want the engine to last very long, you could monkey with the cooling system so it didn't pump as much air. (It takes power to pump air; that's power that doesn't go for moving the car.)

Notice that most of those are the same things you do when trying to make the most powerful engine possible? Because they are increasing efficiency. The thing is, for max MPG you have to increase the engine's efficiency while it is at cruise RPMs and throttle openings. Which are "kinda midrange" and "very small", respectively. Most "power" setups are optimized for WOT and high RPM.

Note that you can gain significant fuel economy by keeping your tires inflated to spec (or over!), keeping the engine in good working order, and by using a very light foot when driving. Not that the latter is any fun in a 914....

--DD

goose2 · 09-14-2005, 05:57 PM

Interesting ideas Dave. I have a six powered 914 for thrill rides and now I'm thinking of building a small engined mileage champ for commutes and such. Do you think that the 1.7 would be the best motor to start with....or maybe something smaller from an earlier VW...or maybe a reconfigured 1.7 with smaller displacement? Any idea what would pretty much "bolt in" and return the best economy? I know someone is doing diesel conversions but I don't need another extensive project.

Dave at Pelican Parts · Dave at Pelican Parts's Garage

Bolt in? Uhh... There's bolting, and then there's bolting.

I think the 2.0 was supposed to return the best fuel economy of the stock engines--slightly more in the EPA tests than the 1.7, even! Not sure exactly why, though.

If you're serious about building for fuel efficiency, you're going to spend quite a bit of money and time and effort building up the engine. You can have a short-short stroke crank made (there's a discussion about this on the Shoptalk Forums Type 4um right now; someone needs to stay in a displacement-limited racing class) but it will cost big $$. Ditto having smaller cylinders made that still fit the case spigots and head registers. Smaller pistons are no big deal, up to a point.

I'd say just bolt in any of the stock motors and be done with it, myself. Or decide that you want the challenge of "max MPG" and get ready to spend a lot more money than you'll ever save on fuel.

--DD

Tidybuoy · 08:11 PM

20mpg is terrible for a 2,000 lb car. Besides doing the engine checks above, jack the car up and make sure all the wheels spin freely. Dragging brakes can make that 2,000lbs feel like 4k. You might also check for fuel leaks - which all 914's get. Be sure to check the fuel lines under the tank (you can usually smell a leak).

I get around 30mpg when I drive normally and a little better when I drive like I'm supposed to.

Vern

Bleyseng · Bleyseng's Garage

Quote:

Originally posted by Dave at Pelican Parts
I think the 2.0 was supposed to return the best fuel economy of the stock engines--slightly more in the EPA tests than the 1.7, even! Not sure exactly why, though.
--DD

The original ads said the "29MPG Porsche" for the 1.7L cars while the 2.0L ads said the car got 25mpg. IIRC Dave

I think the early 1.7's had that overrun feature that turns off the fuel when coasting as did the 75-76 cars. I had a 69 VW type 3 that if you lifted you foot off the gas to coast alot you could get 40mpg easy. The fuel turns back on around 1500 rpm, so you just cruised up to your speed then lifted your foot, coasted, then add more gas then coasted, etc. I drove that car alot during the 73-74 gas crisis.....

Geoff