Concerned about RPM's - page 1 - IDI Engine - VWDiesel.net The IDI, TDI, and mTDI source.

• Concerned about RPM's by The Mad Hatter on 06 May, 2008 16:42
• I may have put this in the wrong section.  Sorry!  But, i wanted to ask the experts!   I'm hoping to use my diesel Golf for commuter duty, but the hwy is 75mph, and thats 3600-3700 according to my tach.  Is that too much for sustained trips?  I don't know much about these little diesels, and i don't want to burn her up!   What kinda RPM's do you guys get on your commutes?  Thanks!
• #1 by jtanguay on 06 May, 2008 16:57
• i wouldn't be worried... as long as the cooling system is working good all you'll be doing is burning some extra fuel.  at or around 2800 rpm seems to be a sweet spot on these motors.  50mpg range.. at 3600 rpm lookout for crap fuel economy...
• #2 by The Mad Hatter on 06 May, 2008 17:07
• Well there isnt much i can do about that, speed limit is the speed limit.  Anything under 70 and i'm a small tasty meal for a tractor trailer!  Anyway to bring down the ratio so its not running so high at high speed?
• #3 by Vincent Waldon on 06 May, 2008 18:06
• Diesel gensets run at 3600 RPM for days and days and days and days...
  
  In terms of lowering your highway rpms... best bet is to figure out what tranny you have (the model is listed on a flat spot at the bottom of the bell housing) and then see what you can find at the local wreckers:
  
  http://www.scirocco.org/gears/
• #4 by The Mad Hatter on 06 May, 2008 18:17
• I haven't crawled under it to look, but i'm pretty sure its a ACH.
• #5 by burn_your_money on 06 May, 2008 18:19
• larger tires will also help lower the RPMs. If I drive highway speeds at 3300 RPM I get 40 MPG with my NA
• #6 by The Mad Hatter on 06 May, 2008 18:26
• I'm running 195 50 R15's.  HOPEFULLY she gets 40mpg.  I'm driving an 130 miles a day!
• #7 by theman53 on 06 May, 2008 18:56
• I don't know if I should admit this...
  I had an 81 rabbit stock na. I got it stuck in the driveway( it is 3/4 of a mile dirt) about 2:30 am comming home from a late late night. I was so not in the mood to try to get it out in the morning and thought it would be better to blow it up than to try to do that in the morn. I held it to the floor for about 4.5 minutes and just rocked it from 1st to reverse NEVER letting up on the fuel until it finally came out. During this time the engine made noises that the only thing that I could say it sounded like was when valves float on a small block chevy and it wouldn't rev past a certain point, but it screamed right along the whole time. I drove it for 30,000 more miles with no problems and sold it. It is still going...I think.
   I don't do that anymore as I am older and don't have a roomate that parks in the way so I don't have to go around and get stuck, but I know that RPM's and these motors get along well. From my experience and IMHO.
  P.S. I always got 45MPG with that one as well.
• #8 by jtanguay on 06 May, 2008 19:04
• forgot to mention as well... the higher the rpm's, the more oil these motors consume.  that might be different if the engine is good and tight though.  hard acceleration seems to burn oil too.  i've been able to not burn a drop by smooth acceleration and keeping rpm's low.  having fun is where the oil level starts dropping  :oops:  :lol:
• #9 by shegel on 06 May, 2008 22:10
• i drive my 86 na 100 miles a day at 70+ speeds and i average 46 mpg's
• #10 by The Mad Hatter on 14 May, 2008 17:27
• Well 3 days trips into the week, and here's what i've got:
  
  -I'll calculate the mileage when i fill it up, but its sitting around a half a tank with about 340 miles on the trip od.   That's a least 40mpg, if not better.  That's running between 70 and 75 and around 3800rpm according to the tach.
  -The new problem, she's using oil rather quickly   .  I know jtanguay said it would at higher rpms.  I checked it tonite after i got home, and its down halfway of the marked area on the dipstick (i'm assuming that's a half a quart low), over a 3 day period.   Engine has 139K miles on it, and just had a new timing belt, if any of that matters.  
  
  The long term solution is for me to move closer to my job, BUT, that could take months.  Anything i can do to try and stop the oil burnage?  Probably nothing besides drive at a lower rpm right?
• #11 by burn_your_money on 14 May, 2008 17:53
• I have never had a diesel that would hold oil above half on the dipstick. It always disappears within a few hundred kms. The bottom half last a lot longer though, just keep an eye on it.
• #12 by gigaz2 on 15 May, 2008 05:03
• new valve oil seals and guides help, but they won't last long till they start leaking again.
  
  I once drove a Fiat Panda 1.3D on a 200Km trip it used 4L of diesel, and 3L of oil...
• #13 by Dr. Diesel on 17 May, 2008 16:07
• if it's normally aspirated, you're probably better off with those rpm's. It might have trouble holding that speed in a headwind with a taller gear ratio.
• #14 by theman53 on 17 May, 2008 17:23
• I fitted a baffle from a later hydraulic head on my mechanical head 84 rabbit and that cut the oil consumption in half. I have heard that you can lose a quart in 300 miles without that baffle on the hydro models. It might be a stretch but maybe that is your problem. It is really easy to forget to put that back on if your messing around under the valve cover :oops: like when you do head gasket or timing belt.