Mk1 TD high speed fuel economy - General - VWDiesel.net The IDI, TDI, and mTDI source.

• Mk1 TD high speed fuel economy by wolfsburged on 13 Oct, 2009 19:34
• 1984 Jetta 1.6TD (factory). Just got my gas gauge and odometer working and calculated my first 'official' tank. Drove 304 miles on 8.17 gallons of D2 diesel. 90% of that was highway at 70-80mph (mostly around 75mph), with some city driving in mixed conditions and generally pushing it pretty hard around town. Works out to about 37 MPG. Good/bad?? I figure I'll be in the 40s easily if I slow down and go easy on the pedal. Seen a lot of numbers thrown around in the 40s and 50s but little mention of conditions to attain. Running stock 7A trans and GTI "snowflake" wheels with 185/50/14 Michelins.
• #1 by Baron VonZeppelin on 14 Oct, 2009 12:46
• 50 series tires ? you musta bought used ones like i've been doing. Cuts down on selections - but saves lotsa bucks.
  
  otherwise ...
  
  The car is a damn lemon !!
  
  
  
  
  
  Sell it to Me
  
  
  
  
  With the fat tires and the fat foot, thats probably about all the mpg you'll get. And its not that bad considering the speeds. I know you did a lot of long term maintenance on it, but can't recall if you did anything with the injectors (lapping - pop testing - or replacements).
  
  IF you dropped back to 60-62 at 90% hwy - you should get as much as 45+mpg with those existing parameters. Maybe even the magic 50 mark.
  Try it for a week.
  
  I'm running 175/65/14 on Sflakes and 2.95 final drive:
  (i think 185/70/14 is best balance - but i buy anything in range when like new (used) and price is right)
  
  When i run 60-62mph cruising speed i get 50'ish + (as much as 52.1) - (tested when ulsd was $4-$5 gallon last year)
  
  When i run 70-72mph cruising speed i get 43-45'ish
  
  75-80mph would probably be 40'ish or less.
  But i wouldn't know.
  When i saw the cut on mpg's at 70mph - i drew the line.
  Was like throwing money out on the street.
  
  With the right tires, right tune, right driving habit - it should do 50+ mpg overall. But its not as automatic of a function as legend has it.
  
  probably just easier to sell me the car and go buy a TDi ..... 
• #2 by Baron VonZeppelin on 14 Oct, 2009 13:00
• And too -
  
  i run the PowerService additive with Cetane Boost (grey jug) in every tankful. Only ULSD fuel.
  
  And i don't push it around town. Or anywhere else. lol
  Sometimes i'll nail it a bit in 4th going down entry ramp onto highway if oncoming traffic looks a bit thick.
  
  Of course Gboro and Aboro aren't exactly Raleigh-type traffic either. But i've been there and through there many times without shots fired or fancy finger pointings.
• #3 by wolfsburged on 14 Oct, 2009 13:19
• Nothing done to the IP or injectors. I do have some PowerService which I need to start using.
  
  And actually now that I go and look they are 185/60/R14s. That's what I get for typing off the top of my head...
  
  This new tank I'm trying for mileage... Last tank I was late for work both days, and well... There goes the mileage.
  
  This time I'm keeping it at around 65mph. Dealing with everybody on US-64E in the 70mph zone where everybody goes 80+ I think I'll stick at the 65mph floor for now. Driving it real easy around town this tank too. We'll see... Finally got my fuel tank leaks and all those issues sorted.
  
  Starting to see some wetness around the IP where that block that has the injector lines meets the rest of the housing. Hoping that doesn't turn into anything. Now that I have an actual clear feed line to the pump I do see some small bubbles running out when I shut off, but nothing major and it always starts right back up fine.
  
  Luckily (or not, depending on how you look at it), I have a long commute which means 300 miles is only about two days worth of driving, so I should get another reading by the end of the week.
• #4 by Baron VonZeppelin on 14 Oct, 2009 14:15
• Quote from: wolfsburged on 14 Oct, 2009 13:19

  ...
  Luckily (or not, depending on how you look at it), I have a long commute which means 300 miles is only about two days worth of driving, so I should get another reading by the end of the week.
  

  
  Wow man, you'd go broke just buying fuel if you sold me the car.
  But its a cool one that i'd like to have, for sure.
  
  Been doing some maint. and tuning on the 81 Truck with big campershell this past week - finally. Running REAL good now.
  
  Was going to do its maiden voyage today, but its turned cold again and raining to get out and move stuff around.
  Plus the wiper blades are shot.    oops
  And i'm sorta lazy today.
  
  High hopes for tomorrow
• #5 by wolfsburged on 15 Oct, 2009 05:28
• Working out in Rocky Mount right now means an easy ~70 mile one way drive. Add a few errands in there and I'm doing 300 miles every two days... That was expensive even in the Honda with 30 MPG. Just waiting now for the new building to be finished in Raleigh so I can quit this drive. The builders are saying early next month, but they also said it'd be done in July...
  
  I hate this rain and cold this week... Luckily with some use my wiper motor has ungummed itself so I now have two legitimate speeds and decent blades.
  
  Hard keeping the windshield from fogging up though if I want heat. I did finally get a new control panel for the HVAC but the heater box is so shot it still doesn't really matter what vent position I have it in. My HVAC blower is siezed or shorted too, so its just natural blow through ventilation. If I dare turn that fan switch I blow my 30A AC fuse. Still, even without the blower that heater works pretty darn good!
  
  Did you end up pulling that truck back from FL?
  
  Jess & I are heading out to Winston/Clemmons area this weekend, I still have that tow bar and a Rabbit/Caddy cluster w/ tach if you want them..
• #6 by Baron VonZeppelin on 15 Oct, 2009 16:10
• Yez, still want those items !
  
  Might be too much hassle for you and Jess to try and orchestrate an enroute meeting off 40 in Gboro. But let me know if you wanna try it in either direction.
  
  I still owe you and her a good dinner and drinks for Bird-Dogging me towards the 81 TD Truck and 85 TD GL !
  Could meet up at OutBack off 40 at 4 seasons mall Gboro ?
  Or whatever you wanna pick out.
  
  The 82 NA Truck in Florida, yep went and hauled it back here a couple months ago.
  Guy gave me a real good deal that included a set of late Sflakes, the all-silver kind. The brakes work and electricals work, so should be a good candidate. Next year ...or the year after ... . But going to get it to run before swapping engines, just to see how it does in case i need it someday for something else. He stopped halfway through a belt/waterpump job - 4 or 5 years ago.
  
  -----------------
  
  Bum weather again today here.
  No maiden voyage in 81 TboTrk yet.
  
  It started easy enough but ran like crap, smoked and leaked fuel in several places when i bought it.
  My 89 NA had more power.
  Brought it home and been glad it cranked when i needed to move it from time to time. Its been here about 3 months.
  
  But knew it had good potentials for tuning (after some needed maintenance) because it ran a lot better with cold start left out and had very minimal blow-by. Finally got around to working with it for a few days and its really jumped up into damn good running shape. It appears the engine was rebuilt before swap/installation.
  
  Turns out it is 1 tooth retarded on Inj Pump.
  PO did the belt and rarely drove it afterwards.
  He was scared to play with pump timing, and had multiples of other things to drive.
    
  I have it advanced to the limit of travel and it will probably take some more advance too. Smoke went away and power came back - revs Great in the driveway. Just going to maiden-drive it a little like this, then go back in and finish it up right. And put the dial on it and all that etc... and fresh brakes.
  
  Dying to see how it drives now.
  Its already improved more than i really expected.
  
  
   
• #7 by wolfsburged on 15 Oct, 2009 17:06
• Filled up tonight. This time around keeping it down to 65mph on the freeway and taking it easy around town and on the ramps. Well, except for showing off to a coworker as to what the mighty beast could do... Drove 291 miles on 7.1 gallons which means 41 MPG! That's more like it. And hopefully this is just the start.
  
  When we did the t-belt job I reset the timing at exactly 1mm on the dial gauge. Still need to go through and do some more adjusting on the fueling, idle, etc. Power is good in general. Warm/hot starts are ridiculously easy. If the engine is hot, I can get it to crank over in less than a single crank with the cold start in!
  
  I had jumped the idle up considerably when we first got it running because it didn't want to stay running - that was when the fuel tank was gunked up and we had about a quarter sized clear spot in the in-tank filter to let fuel through. Turned it up to about 1000 or 1100 RPM idle (who knows - by ear!). Now that the tank is clear I've dropped it back down in the 700ish RPM range. Idles fine enough when warm, but really cold starts are a bit rough. Really rattles the heck out of everything, and I usually give it a little peddle to keep it managable in the morning. Clears up in a block or two though. Had moved the idle up a bit more before but then I ran into a strange problem where my throttle would "stick" - revs would hang if I got above 2000 RPM or so. Wouldn't go up or down unless I gave it more gas or dragged the clutch a bit. Thought I either had a bum pump or massive blow by! Adjusted the idle screw a bit and it went away (along with some WD-40 to the throttle arm). Throttle arm would return just fine, but the revs stayed high -who knows!
  
  Still need to tweak a bit more though. Clearing up the cold idle will be nice, and then just keeping going through the thing. Have to replace the undersized melting glowplug fuse with a new fusible link, and a lot of chasing small problems around (HVAC -everything!, defroster, misc interior lights, rattles, etc). But overall its running nice. Coolant is still dirty after flushing quite a bit, not quite sure what's going on. Wondering if my oil cooler or something is weeping oil into it, or if its still just residual crap floating around.
  
  I'll see what the travel plans are exactly and get back to you about the weekend.
• #8 by Baron VonZeppelin on 15 Oct, 2009 20:38
• That is an inspiring improvement.
  Keep at it bud.
  
  I think a 24 hour ATF pump treatment and ritual PwrServ doseage would be good for yours. imho
  
  Maxfax has a good DIY method on cleaning out oil residues.
  
  Automatic Dishwasher detergent - powder or gel.
  Not to be confused with Dishwashing Soap Liquid.
  
  Strait water and a good dose of that stuff.
  Works like a charm for him even after some heavy nasty oil leaks.
  
  The 81 has some thin residue pond scum layer on top in the exp tank. Pull off a hose anywhere and its nice clean bright green coming out. So gonna drain the exp tank first by itself to get that out. Then drain and capture the good stuff - then water/DW deterg the thing for a good cleaning out all through on the inside.
  
  But want to drive this crazy wild Tank some first !
  Dang this london type weather lately !
  
  It cranks cold or hot practically the same instant i turn the key now. Its impressing the heck out of me so far.
  PO would flip out on how it runs now.
  And only halfway done.
  
  Your 84 has been nothing but impressive.
  That thing must have sat for about 15 years, and comes roaring back like it has. These are the neatest machines i've ever played with.
  
  Just let me know if you two wanna catch up in Gboro.
  Or i'll catch you guys in Raleigh eventually.
  
  
  
  
• #9 by wolfsburged on 16 Oct, 2009 11:36
• We may be able to hook up with you on our way back on Sunday. I'll give you a call later and we can figure something out.