poor MPG

[rabbit82]

I have an 82 diesel rabbit that runs excellent with plenty of power. It is a 4 spd. I had a new timing belt put on after I bought it. I didn't drive it much for several months, actually about a year. Just drove it around town. Well, I finally dedicated myself to driving it everyday for a week to work. I checked the mpg on it and it is getting around 32mpg. The return line to the tank is open/clear. It has plenty of power. There is no leaking anywhere of fuel. I cleaned the injectors, but didn't test them for leaking. New fuel filter. It has sat in my shop for 3 days now and there is no smell of diesel at all. When the engine is running there is no leaking around the injectors. The car doesn't smoke while driving. If I let it sit for a day or so it will smoke on start up, white smoke, but clears up pretty fast. If I get on the pedal it doesn't blow any smoke.
 I have a friend that messes with these and he said he had a timing gauge for the pump but he has never used it. He kinda goes by the seat of his pants, nothing really technical. He doesn't know what could cause this to get such bad mileage. He has several trucks and rabbits and they all get 45 or better.
So, what should I be looking at?
I am going to recheck the mpg just to make sure I didn't get confused on the miles, but I am 95% sure I had the correct miles.

[Baron VonZeppelin]

What is your average MPH , and city/hwy percentage ?
Under 60mph on the Hwy nets best MPG.

Your biggest probo is likely the tranny.
Most of the 4 speeds were geared for pizza delivery.
Rare few got the 3+E (4spd) - those are good.

On the bottom of your tranny bellhousing up near engine oil pan - there is a flat machined pad with stampings. Look for something like GC GL GN GP or 4A or whatever.

Then go to  http://www.xjamiex.com/mk2resource/eandt/ratios.html
and see what box you have.

I'd want the timing verified by dial gauge.
Want to be under 1.0 mm
0.85 - 0.95mm is spec

[rabbit82]

I'll take a look at it tomorrow. My shifter knob has 123 E on it (of course it could have come off a car from another from another). If I understand correctly, the 3+E is good vs. 1234?
I'll let you know soon.
Oh yea, I drive about 25 miles one way on the interstate and keep it between 60 and 65. It seems to like that spot best. I tried 70 but just doesn't cruise as good. I am now one of the slow ones. I'm used to driving my truck at 75 so................ All is good as long as I'm saving the all mighty dollar, plus I am really beginning to like this little ride a lot.

[ORCoaster]

I too would be looking at the tranny code first.  The letters on the first part of the series is what you want but as long as you have your head down there write down the date code as well.  Sometimes they switched ratios in mid year.  I believe the code goes day month and year (final digit).  Someone correct my pea brain memory if I am wrong.

The timing should be known as well.  It may start well enough but already be sort of advanced.  So then when pressure builds in the IP and starts advancing the timing more it is hurting you not helping get mileage.  You might want to gauge the idle IP pressure as well.  Lots of us run a gauge on it to determine if we need to tap in that pressure regulator valve a bit or maybe back it off.  

What I found is that there seems to be a sweet cruising speed for my car at 67 mph.  I have a 5spd FF transmission.  By going to sites that convert the speed, tranny and wheel size I can get RPM.  I know what I turn at various gears at 65 mph.  When I hit the hills I have to downshift if I have backed off the power/smoke screw to the point where it lags power.  For me, running it a bit rich helps me keep it in the high gears rather than downshift and rap the crap out of it going the same speed.  I have tried all sorts of settings, you have to write that stuff down and only change one thing at a time.  The different settings for initial timing, IP pressure and smoke screw have kept me in the 46-49 mpg zone for over a year.  

Because all of my miles are highway I only have those numbers.  I have no idea what city mileage is, I usually am walking or riding the bus or train to get around in the city.

Poke around with this site for awhile and you can see why some transmissions hooked to the same 1.6 engine scream and others lug along. 
http://scirocco.org/gears/

Any help?  DAS

[rabbit82]

Trans code is GL23091
I copied this from the site mentioned above. 
GL 3.46 1.75 1.07 0.71 - 3.89 1051.18 White (16 tooth) 90mm Yes A1 22mm 020 3+E from '81

So what are the rest of the numbers after the GL?
I am assuming this tranny is a good one to have? As good as a 5spd? Still better than the regular 4spd?

[rabbit82]

ORcoaster, thanks for the site http://scirocco.org/gears/. I checked it out and pluged in some numbers.
What is the optimal shifting point on these diesels? 2000rpm?
It is showing that when I am traveling at 65mph I am turning 2650rpms, does this sound right/good?

Going by the calculator they have, with larger tires I will be turning less rpms at 65mph than with the little 13's on it now. That's gotta be good for mpg.

[bajacalal]

ORcoaster, thanks for the site http://scirocco.org/gears/. I checked it out and pluged in some numbers.
What is the optimal shifting point on these diesels? 2000rpm?
It is showing that when I am traveling at 65mph I am turning 2650rpms, does this sound right/good?

Going by the calculator they have, with larger tires I will be turning less rpms at 65mph than with the little 13's on it now. That's gotta be good for mpg.

That sounds low. I would think something closer to 3000. These are high RPM machines with a powerband higher up on the RPM scale than what is typical for diesel engines.

Remember, a diesel engine doesn't have to maintain a stoichiometric ratio like a gasser. It only needs enough fuel to keep it spinning.

So try to keep that in mind and adjust your driving style accordingly, try not to feed it too much fuel, and when you're cruising, try to see how much you can take your foot further off the accelerator without loosing speed. I honestly believe higher RPMs with less throttle is better. If you shift it too early, you lug the engine, i.e. you fall out of the optimal powerband and since the engine isn't making a lot of torque/HP at lower RPM, you have to give it more fuel to compensate or else you don't accelerate. Wherever the engine feels like it's making most of the power, that is where it is operating most efficiently and making the most power for the fuel you are giving it.

Also, if you run larger tires, they will drop your RPM at any given speed, so while it will run at a lower RPM on the highway, you might end up using more fuel because the larger and heavier tires require more energy to turn. The difference will probably be minimal though.
 

[Baron VonZeppelin]

ORcoaster, thanks for the site http://scirocco.org/gears/. I checked it out and pluged in some numbers.
What is the optimal shifting point on these diesels? 2000rpm?
It is showing that when I am traveling at 65mph I am turning 2650rpms, does this sound right/good?

Going by the calculator they have, with larger tires I will be turning less rpms at 65mph than with the little 13's on it now. That's gotta be good for mpg.

GL 23091
2 = 1982 model year production application
3091 = 309th day of 1981 (final assy date of tranny)

That is a great 4spd - the best one.
And pretty equal to most all good 5spds - even better than a lot of them.
3.89 x 0.71 = 2.76 final drive ratio

2200 - 2500 is optimal range for the engine (shifting and cruise)
anything below 3000 is pretty good.
I short shift versus running completely up to top - or past - the sweet spot.
Probably about 2200-2400 range unless i'm getting on the highway into traffic.

So tranny ratio is not a problem for you.
Check to see if any of your wheels feel hot after a drive. (brakes/bearings)
Fronts will be warm to luke hot, rears should be cool to luke warm.

I "suppose" you're testing mileage by filling up tank - driving certain distance - then refilling - and doing the math.
Verify odometer reading as being in spec.
Maybe thats a weak link.
Mk1 is notorious for fouled odometers.

Taller tire can/will help in most all cases.
Within reason.

Old mufflers packed full with soot can be a cause.
Tired gear oil in tranny hurts.
Old air and fuel filters past their prime rob you.

Under 65 on hwy you should get at least 40mpg - minimum.
 

[libbydiesel]

A significant number of things that affect fuel economy have nothing to do with the engine or gearing/rpms.

[rabbit82]

I am checking the gpm by gallons and mileage. Odometer, not sure if it is in spec and wouldn't know how to check it. I did use the trip meter but this time I wrote down the miles on the odometer to make sure they are in sync.
As far as bearing, I put all new ones on front and back. Also all new filters, fuel and air. Checked the air filter today just to make sure it wasn't oil soaked.
Muffler, well I don't have an answer there. Could be.
I did some trading with an older retired friend, he's been working on these things for a long time. Anyway, he put a new timing belt on for me. He was over here today and I quizzed him on how he did it. He said he put everything dead on, no advancing. He doesn't use a gauge to set the pump timing, he just does it by the sound of the engine. He did bring me a gauge to use, now if I can figure out how to use it. I have to take it all apart anyway, it started leaking oil really bad once I started driving it on a regular basis. Not sure which seal is leaking yet. I pulled the top cover and nothing up there is leaking. It is dumping oil though. The bottom of the car is oil soaked. I did replace the oil pan gasket so that should slow it down a good bit since it was leaking like a banshee. Alot of oil coming from the plastic cover so I know its under there somewhere.
Man, this thing runs so good and I am so ready to have all the bugs worked out so I can just drive it for a while and save some $$$$$$$$$$$$.

What is a good brand tbelt tensioner? Autozone has a Duralast and I looked at some places online that have the OEM germany ones. also, have any of you used partsplace for buying parts?

[Baron VonZeppelin]

The Duralast is a repackaged GMB Tensioner.
Cloyes, Dayco, Gates, Goodyear, and many others are all a repackaged GMB.
I've got about 4 of them in current service - no probs.
They are fine.

Maybe not the full bestest in the world - but they are fine - and when you change your belt next time - or just want a new one - Advance and AutoZone will fork another one right across the counter. Lifetime of free tensioners after you buy one.

PartsPlace is good supplier.
Also check out AutohausAZ.com and RockAuto.com
AhAz give free ship on $50+ order.
Most times Rock still beats them even with shipping tho.
AhAz takes about 7 business days to get to NC.
Rock is about 3-4 days usually.

I think we already gave you fair warning about Prothe/Hansdiesel/Westport in Charlotte NC.

If your T-Belt is oil soaked ..... get another one. sorry

[R.O.R-2.0]

The Duralast is a repackaged GMB Tensioner.
Cloyes, Dayco, Gates, Goodyear, and many others are all a repackaged GMB.
I've got about 4 of them in current service - no probs.
They are fine.

Maybe not the full bestest in the world - but they are fine - and when you change your belt next time - or just want a new one - Advance and AutoZone will fork another one right across the counter. Lifetime of free tensioners after you buy one.

PartsPlace is good supplier.
Also check out AutohausAZ.com and RockAuto.com
AhAz give free ship on $50+ order.
Most times Rock still beats them even with shipping tho.
AhAz takes about 7 business days to get to NC.
Rock is about 3-4 days usually.

I think we already gave you fair warning about Prothe/Hansdiesel/Westport in Charlotte NC.

If your T-Belt is oil soaked ..... get another one. sorry

my last Gates kit that i bought (86 GTI) had an actual german timing tensioner, and it was NOT GMB, surprisingly..

the belt is still gates, right?

[rabbit82]

The belt is not oil soaked, clean as a  whistle. Don't know which seal is the culprit yet, but while I have it apart would you replace all seals while you're in there or go with "if it aint broke" rule?
No one touched on my question about the timing belt setting my friend did. What do you think? I thought I had read somewhere to advance it a little?

[Baron VonZeppelin]

RoR, i don't have a clue if gasser and dzl are same tensioner.
But the Tbelt should say Gates or Made In USA.

Rabbit82, if it aint broke, don't break it.
Unless you just want the experience.

Your friend is puffing smoke a lil bit.
Without the dial gauge - that he never uses - no way he can know where he has it set - in regards to 0.01mm frog hairs. Maybe he just means he hits all the index marks as best as he can see them.

0.85mm - 0.95mm is spec on NA
I usually go 0.98 - 1.00mm and see how it rolls.
A really old worn pump might like 1.05 or +

a lil extra advanced is usually a good thing

And i don't mean anything negative towards your friend.
Just being honest.

[8v-of-fury]

As long as you got all the marks lined up you can adjust by ear and feel from there. The actual number where it is set doesn't really mean anything except to tell you where it is set :p. lol

Seeing as how every pump needs a different setting due to wear and what-not the settings are just a guideline. You know your in this guideline based on how the car is running.