An idea for better mileage

[fspGTD]

fspGTD

I already have the hardest tires I could get for a reasonable price. They are 185/65R14 Michelin Destiny's. They have a wear rating of 680 and I have pumped to 42psi in the front and 40psi in the rear. I figured that a 185mm width tire would reduce the frontal area of the tire a little, which would reduce drag. I also chose a little taller aspect ratio than stock which would lower rpm's on the highway.

I'm beginning to think that there's very little I can do now to improve my mileage :x .

Peter

Uh... 185/65/14's are a wide tire for a Rabbit.  The original Rabbits came equipped with 155 width tires, and had as an option later on 5.5" wide rims with 175-width tires.  The only Rabbits sold with 185-width tires were in '83 and '84 on the '83-'84 Rabbit GTI (in 185/60/14 size).

I would see if a 155 width is available in an application popular with electric vehicles (lowest possible rolling resistance, not just highest treadwear).  I'd run them with lightweight aluminum wheels in a cookie-cutter like 5" width, if that is an option.

How about wheel fairings - IE: spun aluminum discs that cover the wheel openings making the smooth.  Are you running the euro A-piller fairings?  Lowering the car would help cut down on aero drag as well, as would installing an aim dam that extends down low, and putting covers over any unnecessary openings in the radiator support (forcing more air go around the more streamlined top and sides of the car.)

I think you could get well over 50's US mpg in an IDI diesel rabbit...

And oh by the way, saving weight wherever you can will also help with overall mpg.  There are many things you can do to take weight off these cars - let me know if you are short on any idea in that department!  I have no doubt an 1800lb rabbit diesel will get significantly better mileage than a 2200lb'er.  Fuel economy in cross-country trips on my Rabbit racecar has gone up noticeably since I've taken off a lot of weight, and I think it's because less weight saves fuel.  Every mountain pass you have to climb up for example, will take less fuel to do so, any little acceleration changes will take less fuel, etc.  This is also the reason why we don't see the later-model TDI's with more efficient motors getting fuel economy any better than a Rabbit with an older IDI: the car bodies are so much heavier.  Got as tall as possible ratio of ring and pinion and 5th gear also.

[fspGTD]

Oops, just re-read your post and see you have a '94 Golf.  I thought you were talking about a Rabbit, so anyway feel free to disregard a lot of the specific recommendations, but you can still probably apply the same concepts to getting better mpg.

[farkman]

fspGTD

I apologize for not mentioning my car beforehand. Thanks for your tips, I will definitely do something about the openings in the front end and lowering the car, only a bit though. It's a good thing you mentioned that, I need new suspension anyways. Perhaps some Bilstein shocks and Eibach springs are in order. Tips on weight reduction would be appreciated.

Thanks

Peter

[VWRacer]

As for short shifting 1st, 2nd, 3rd and shifting directly to fifth, I pretty much do the exact opposite. I accelerate quite spiritedly so I can get into fifth as fast as I can. I can only shift into fifth at around 60km/h (1600rpm)though. Below that the engine is lugging.

That makes it easy to do a test, Peter. Do a careful refill and use my technique for a tank of fuel. See what it gets you.

Stan

[farkman]

Stan

I should try that but I can't stand accelerating slowly. There's something addictive about the torque, it's like a drug :lol:. And if I do any more than a few dozen kilometers in the city, I will kiss the 50 mpg target goodbye anyways. I only expect to get 50 mpg, if I drive all highway at a constant 95km/h.  

Peter

[VWRacer]

Oh, I understand. I only do it when I'm not going to impede traffic. But you might be surprised at how much it helps in city traffic. Here in the San Francisco area it doesn't normally move all that fast anyway.

If you don't like doing it in normal driving, you may have problems going slow on a long trip, too. I did a long run here in California's central valley at 55 mph (90 kph) and thought I'd die of boredom. But I did get 63 MPG! :shock:

[farkman]

Stan

I don't accelerate fast if I see that I'll have to slow down again (such as a red light ahead), but other than that I try to get into fifth gear as fast as possible, as long as the speed limit is 60km/h or higher. Up here traffic is pretty good unless you get stuck in rush hour, but I try not to drive during those times.

As for driving at 95km/h being boring, all I need is some tunes on the radio and I'm set. I'm very used to driving slowly on the highway and I would hate to be one of those people that switch lanes every ten seconds just to gain a few minutes.

Peter

[Wingaman]

If you want to lower your suspension, take a look on the FK suspension kit.

http://www.concept1.ca/FK%20SUSP.htm
Hi-Tec Suspension Kits:  $628 CDN  /  $465 US

I install on kit like that on a A2 Jetta and she got a really nice ride with this
The rear is ajustable.

[Rat407]

TDIMeister

My best tank so far was 45 miles per US gallon, so about 54 miles per imperial gallon. And that was 80% highway, 20% city. But I want to get 50 miles per US gallon so I can go to Florida (Pompano beach area, about 2500km away from what I've been told) with only one fillup along the way, somewhere in North Carolina probably.  

Although I would love to get a TDI, I don't have the money to buy one :lol: .  

Peter

From my home here in NC, which I get onto I-95 at mile marker 88 and I'm 30 miles from 95 it was 778 miles to Pompano Fl.  Made it in 10 and half hours. Would have done better but hit rush hour traffic just as I got to the North side of the city.  I took my father-in-law down to his friends birthday party and a WWII reunion.  We took his 98 Eldorado (sweet ride) and got 30 mpg out of that NorthStar 32valve V8.  That really impressed me for such a large vehicle, engine and cruising speed.

[Rat407]

I have an idea, if it would work.  What do you think of running space saver spare tires on all four wheels?  I know they are not as tall but they are thinner.  :wink:

[BlackTieTD]

weight savings...

do you have AC? ditch it... the whole system has to be 50Ibs+

take out your back seats for long trips

get rid of a fullsize spare in favour of a space saver, or ditch it altogether along with the OEM jack and buy a can of that flat tire inflator from canadian tire.

also..

run ridiculously-skinny tires on the back for long trips (or all 4 corners..up to you)

drop the nose of the car and get a lower spoiler

replace wheel bearings if you havent before

are your tires/rims all perfectly straight/true? i gained 70km/h per tank consistantly when i changed out a rear tire, got rid of a little bit of shimmy too. had an alignment recently?

do you run a fuel system additive like stanadyne? that could help


i still think the best single way to improve economy is a super-tall 5th gear. you could also consider getting a long 5th and changing to a longer final drive when you are in there.


i made a point of seeing how the car performs at 50km/h in 5th gear last night after reading this thread.. even with the long gearbox 50km/h isn't a problem in 5th.. a little sluggish but i could probably cruise at the low 40s (~43km/h and above) no problems in 5th  

the first time i took my friend out in my rabbit (he has a mkIII 8v gasser) i put it in 5th going up a steep hill at 60km/h just to show him the torque of the diesel... he didn't think it would pull up the hill, but the car actually accelerated (mind you, slowly). diesel power!

[farkman]

Wingman

Those look pretty good but I have heard such good things about the Bilstein's. And I'm not looking to spend that much money ($628 + shipping) either :lol: .

Rat 407

What large city are you located near? I would like to get an idea of how far away you are from the South Carolina border. Wouldn't those space saver spare tires reduce my mileage. The engine would probably be turning at close 3000 rpm compared to 2400 revs with the tires I have on now. Plus I don't want to spend a few hundred dollars on something that might not even work. I can use that money towards new suspension .

BlackTieTD

No I don't have AC. I specifically bought this car because it didn't have AC (and it was in good condition). I don't even need it because I don't get very hot. Do back seats even weigh that much? It looks like it only weighs about 25 pounds. I haven't replaced the rear wheel bearings but I have regreased them with Amsoil S2000 grease. The rear bearings are still in good condition but I have no idea about the front ones. Can those even be greased? or are they sealed. Changing gears or final drives is not really in my plans right now due to cost and difficulty (and I don't have the right tools either :lol: ).

What rpm were you at doing 50km/h in 5th gear. Wouldn't the engine be lugging like crazy, mine would be.

Peter

[RAMMSTEIN]

You really think I would not answer to this thread....mmmm

Ok, tires:

Inflation at the max stated on the side of the tire (44 or 35, lucky if you have a 51 psi tire).

Treadwear: 680 is not optimum.

The best treadwear in the industry is a Michelin: the HydroEdge, 760 of treadwear.

Tranny fluid: change for Redline MTL: I gained 2.8% fuel economy with it.

How tall is this "E" fifth gear?

Drive slower than 95 kph.

Windows up, no AC is better.

Coasting in gear (I don't know if true with IDI, but the TDI cuts fueling while coasting in gear).

Travelling on flat lands vs hills helps a lot.

[BlackTieTD]

Do back seats even weigh that much? It looks like it only weighs about 25 pounds.

not sure how much they weigh, 25-35Ibs seems about right. its not a huge weight savings but every little bit helps... in a sub-1900Ib car (my rabbit) i'll notice a 30Ib difference... ie: i'll notice the difference when i have my toolbox in the hatch, to acceleration anyway. its probably not really worth the trouble to take the rear seats out on a mkIII though unless you leave them out.

What rpm were you at doing 50km/h in 5th gear. Wouldn't the engine be lugging like crazy, mine would be.

How tall is this "E" fifth gear?

its lugging along, but not chugging badly or anything... its pretty low but not too bad. i usually have a rule of thumb, if i'm at 60km/h or above, i go to 5th gear. 50km/h is a little low for 5th, but i never find myself in a real-life situation where i would drive 50km/h in 5th. if the speed limit is 50km/h, i'll do 55 or 60km/h and be in 5th... if the speed limit is lower, or i'm in a residential area, i'll stay in 4th or even 3rd for better response, better accelation and feel around corners, etc..

i found this chart with 020 ratios: http://www.4crawler.com/Diesel/VW_020_transmission.shtml

the gearbox in my car is an FF, made from 6/79 to 7/83 for US market cars. final drive of 3.89 and a 5th gear of 0.76. 3500rpm in 5th will get you 83mph or about 133km/h. if my math is right, thats about 1315rpm at 50km/h in 5th, pretty low! (i don't have a tach installed yet)

i've had the car up to 160km/h (calculations say 4210rpm) and it feels like it still has some more legs...

[Rat407]

Farkman,

I live 120 miles from the NC, SC boarder.  I'm 30 miles to I-95 and at that point it is 90 miles to the border. You can stop off and say hi to Pedro at South Of The Boarder.    

Didn't think of the RPM you would be turning with the space saver spares on. I bet it would be a little higher. But inflated at 60psi like they say on the side it would be a rough ride.