[Vwdiesel] Vwdiesel Digest, Vol 57, Issue 9

[Chuck Carnohan]

You might want to try adjusting the timing by ear and eye (hillbilly timing). There are many discussions on the methods here and on the vwdieselparts.com forum. Timing can be a very tricky thing with these old diesels. I know there are differing views but mine is that timing by the book will likely not be optimal for the car's performance and fuel consumption. Black oil very quickly is is simply carbon in the oil. This is typical of all diesels but can be reduced by optimal fuel/air ratio. Black smoke is unburned fuel which is contributing to the black oil!

Chuck
----  <vwdiesel-request at vwfans.com> wrote:
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> Today's Topics:
> 
>    1. Rabbit down on power/ mpg (Scott Alexander)
>    2. Re: Rabbit down on power/ mpg (lbaird119 at aol.com)
>    3. Re: Rabbit down on power/ mpg (Scott Alexander)
>    4. Re: something worth trading the A4 in for (Terry Briggs)
>    5. Re: something worth trading the A4 in for (David Schwarze)
>    6. Re: torque vs. horsepower (was: something worth trading the
>       A4 in for) (Roger Brown)
> 
> 
> ----------------------------------------------------------------------
> 
> Message: 1
> Date: Sun, 06 Jul 2008 15:31:53 -0400
> From: Scott Alexander <salex at dsl.cis.upenn.edu>
> Subject: [Vwdiesel] Rabbit down on power/ mpg
> To: vwdiesel at vwfans.com
> Message-ID: <0522F70C-6C9C-4A4C-9B0A-EE26A59C85B2 at dsl.cis.upenn.edu>
> Content-Type: text/plain; charset=US-ASCII; format=flowed; delsp=yes
> 
> I'm digging into my '82 Rabbit Diesel for a number of things.  See  
> below for a more complete description, but I have the components in  
> front of the injection pump pulled off and will pull the steering rack  
> shortly.
> 
> When I first got the car running after I bought it, the mpg started to  
> fall and it's now in the low 30s.  At the same time, a friend who  
> occasionally drove a friend's when it was new believes that this one  
> is down on power.  It is capable of producing a black cloud out the  
> back.  We checked the compression before getting it running and  
> compression was within spec.  We also set the timing on the fuel  
> pump.  The valve clearance has not been checked although we're not  
> hearing/ seeing any signs of valves incorrectly set.
> 
> Since everything is pretty much opened up, I'm trying to figure out if  
> there's some deeper work that I should do now.  My friend suggests  
> that the rings may be tired.  (He also points out that the oil turns  
> black very quickly.)  Since I fear the injection pump ;), I'm  
> wondering if it's worth having that rebuilt.  I also have a spare that  
> was supposed to be good when pulled that I could swap in as a  
> comparison point.  Of course, we're also at the point where it would  
> be easier than normal to do things like run another compression check.
> 
> Any suggestions on where to look and one to try next?
> 
> (One of my A/C mounting ears broke, so I've been pulling everything  
> off the front of the engine so as to replace the compressor.  As long  
> as I'm in there, I'm swapping out the power steering rack for a manual  
> rack.  The manual rack seems to work pretty well on these cars and I'm  
> looking forward to not having to work around power steering hoses and  
> pumps and stuff in the future.)
> 
> thanks,
> Scott Alexander
> Warren, NJ
> 
> 
> 
> ------------------------------
> 
> Message: 2
> Date: Sun, 06 Jul 2008 18:07:12 -0400
> From: lbaird119 at aol.com
> Subject: Re: [Vwdiesel] Rabbit down on power/ mpg
> To: salex at dsl.cis.upenn.edu, vwdiesel at vwfans.com
> Message-ID: <8CAADCBC6B634B8-1038-B734 at webmail-nb10.sysops.aol.com>
> Content-Type: text/plain; charset="us-ascii"
> 
> 
> 
> 
> -----Original Message-----
> From: Scott Alexander <salex at dsl.cis.upenn.edu>
> To: vwdiesel at vwfans.com
> Sent: Sun, 6 Jul 2008 12:31 pm
> Subject: [Vwdiesel] Rabbit down on power/ mpg
> 
> 
> 
> >  It is capable of producing a black cloud out the  
> >back.  We checked the compression before getting it running and  
> >compression was within spec.  We also set the timing on the fuel  
> >pump.  The valve clearance has not been checked although we're not  
> >hearing/ seeing any signs of valves incorrectly set.
> 
>     
>   There's really no "signs" that the valves are out of adjustment.
> It's worth checking.  Blowing black smoke is too much unburned fuel.
> If the pump hasn't been dinkeed with (most likely not) then the 
> injuecors are likely worn and need rebuilt/replaced.
> >
> >Since everything is pretty much opened up, I'm trying to figure out if  
> >there's some deeper work that I should do now.  My friend suggests  
> >that the rings may be tired.  (He also points out that the oil turns  
> >black very quickly.)  Since I fear the injection pump ;), I'm  
> >wondering if it's worth having that rebuilt.  I also have a spare that  
> >was supposed to be good when pulled that I could swap in as a  
> >comparison point.  Of course, we're also at the point where it would  
> >be easier than normal to do things like run another compression check.
> >
> >Any suggestions on where to look and one to try next?
> 
>     
>   Since your compression is good, the rings are likely good.  Oil 
> will turn black real fast if you're blowing black so that is likely 
> the cause of the lower mpg AND the black oil (but don't they all 
> turn the oil black quickly?)  ;-)  Low power could be from 
> incorrect timing specs, misadjusted valves, or bad injectors.
> Bad injectors would explain both.  Wrong timing specs would 
> only make other problems worse, except for the low power.  
> It could cause that.  It would be rare for it to be a pump 
> problem.  Of course check your air and fuel filter.  Both 
> of those could cause the exact same problems.  Air filter is 
> obvious.  A dirty fuel filter messes with pump pressures, timing 
> and whatnot due to lack of proper internal pressures.
> 
> 
>   You want to make sure your pump and timing specs match.  Pump 
> could be from another car so cross check your vw part number on 
> the pump.  I'm not home currently so I'm not sure where the 
> address of my pump list is...
>      Loren
> 
> 
> 
> 
> ------------------------------
> 
> Message: 3
> Date: Sun, 06 Jul 2008 19:17:08 -0400
> From: Scott Alexander <salex at dsl.cis.upenn.edu>
> Subject: Re: [Vwdiesel] Rabbit down on power/ mpg
> To: LBaird119 at aol.com
> Cc: vwdiesel at vwfans.com
> Message-ID: <48A923F3-87D8-49A4-AAB8-FA8E66355905 at dsl.cis.upenn.edu>
> Content-Type: text/plain; charset=US-ASCII; format=flowed; delsp=yes
> 
> Loren:
> 
> Thanks for the suggestions.  Let me clarify a few points.
> 
> When I say it is capable of producing black smoke, I'm referring to  
> what happens if I tromp on the peddle.  Normally, it doesn't produce  
> anything excessive.  I mentioned that only as evidence that there  
> wasn't a problem that would cause under-fueling.
> 
> I've replaced the injectors with rebuilt injectors, so I'm guessing  
> they are OK.  (That also didn't change the behavior.)
> 
> I was wondering how quickly the oil turns black if the car is working  
> properly.  My impression is that that normally happens pretty  
> quickly.  Since my friend is more of a gasser type of guy, he's pretty  
> surprised by how quickly it happens.
> 
> I'll double check the filters.  I've replaced both of them without  
> effect on the problem.
> 
> I will also check to see if the pump is original.  Clearly some of the  
> previous owners also did their own work, so a change of pump is  
> entirely possible.
> 
> Thanks,
> Scott
> 
> On Jul 6, 2008, at 6:07 PM, LBaird119 at aol.com wrote:
> 
> >
> >
> >
> > -----Original Message-----
> > From: Scott Alexander <salex at dsl.cis.upenn.edu>
> > To: vwdiesel at vwfans.com
> > Sent: Sun, 6 Jul 2008 12:31 pm
> > Subject: [Vwdiesel] Rabbit down on power/ mpg
> >
> > >  It is capable of producing a black cloud out the
> > >back.  We checked the compression before getting it running and
> > >compression was within spec.  We also set the timing on the fuel
> > >pump.  The valve clearance has not been checked although we're not
> > >hearing/ seeing any signs of valves incorrectly set.
> >
> >
> >
> >
> >
> >   There's really no "signs" that the valves are out of adjustment.
> >
> > It's worth checking.  Blowing black smoke is too much unburned fuel.
> >
> > If the pump hasn't been dinkeed with (most likely not) then the
> >
> > injuecors are likely worn and need rebuilt/replaced.
> > >
> > >Since everything is pretty much opened up, I'm trying to figure out  
> > if
> > >there's some deeper work that I should do now.  My friend suggests
> > >that the rings may be tired.  (He also points out that the oil turns
> > >black very quickly.)  Since I fear the injection pump ;), I'm
> > >wondering if it's worth having that rebuilt.  I also have a spare  
> > that
> > >was supposed to be good when pulled that I could swap in as a
> > >comparison point.  Of course, we're also at the point where it would
> > >be easier than normal to do things like run another compression  
> > check.
> > >
> > >Any suggestions on where to look and one to try next?
> >
> >
> >
> >
> >
> >   Since your compression is good, the rings are likely good.  Oil
> >
> > will turn black real fast if you're blowing black so that is likely
> >
> > the cause of the lower mpg AND the black oil (but don't they all
> >
> > turn the oil black quickly?)  ;-)  Low power could be from
> >
> > incorrect timing specs, misadjusted valves, or bad injectors.
> >
> > Bad injectors would explain both.  Wrong timing specs would
> >
> > only make other problems worse, except for the low power.
> >
> > It could cause that.  It would be rare for it to be a pump
> >
> > problem.  Of course check your air and fuel filter.  Both
> >
> > of those could cause the exact same problems.  Air filter is
> >
> > obvious.  A dirty fuel filter messes with pump pressures, timing
> >
> > and whatnot due to lack of proper internal pressures.
> >
> >
> >
> >
> >
> >   You want to make sure your pump and timing specs match.  Pump
> >
> > could be from another car so cross check your vw part number on
> >
> > the pump.  I'm not home currently so I'm not sure where the
> >
> > address of my pump list is...
> >      Loren
> >
> > The Famous, the infamous, the lame - in your browser. Get the TMZ  
> > Toolbar Now!
> 
> 
> 
> ------------------------------
> 
> Message: 4
> Date: Sun, 6 Jul 2008 20:07:09 -0400
> From: Terry Briggs <vbriggs at stny.rr.com>
> Subject: Re: [Vwdiesel] something worth trading the A4 in for
> To: vwdiesel at vwfans.com
> Message-ID: <c8caeaf5be7bce3986cce997c85ac45a at stny.rr.com>
> Content-Type: text/plain;	charset=US-ASCII;	format=flowed
> 
> You can have massive amounts of HP and little to no torque, and said 
> car, plane {insert fav mode of transport} and you won't go anywhere 
> fast but once you get it rolling, will be able to get some good speed.  
> HP doesn't move anything, torque is what gets the world moving. Torque 
> being a rotational force applied. if it doesn't have the grunt to twist 
> the axle, not going to move much. Granted there is a hand in hand 
> correlation between HP and torque, but it is possible to have hi torque 
> and low hp and beat anything that pulls up next to you, you just need 
> the right weight car, bike etc. Compared to a gasser, a diesel truck 
> has low hp and very hi torque, off the line the gasser doesn't stand a 
> chance, massive amounts of torque to get the load rolling, down the 
> line, due to several factors like rpm capability of a gasser compared 
> to a diesel things change but there are still more examples of diesels 
> smoking the tires off of a gasser due to torque.
> On Jul 6, 2008, at 3:07 AM, David Schwarze wrote:
> 
> > Sorry, but HP is what moves the car.  Period.  Torque does you no good
> > if you don't have some RPM to go with it, and at that point you are
> > talking about HP (because HP is basically torque X RPM).
> >
> > Torque is only useful as a measurement of the specific output of the
> > engine at a particular RPM.  Good for measuring efficiency, not
> > particularly useful in determining how fast a car will accelerate.
> >
> > The more HP you have, the faster the car will accelerate.  Rapid
> > acceleration is a simple matter of commanding the motor to the RPM 
> > which
> > provides maximum HP and keeping it as close to that RPM as possible.
> > Notice that I did not mention torque anywhere in that sentence.
> >
> > The advantage of a diesel is that it makes relatively high HP at low
> > RPMs... so at low RPM you have an advantage with the diesel.  Great for
> > towing.  At high RPM however the diesel loses it's advantage and high
> > RPM is where the most horsepower is made.
> >
> > Consider two cars - one making 60lb/ft peak torque and 100 peak hp and
> > the other making 100 lb/ft peak torque and 60 peak hp (with typical
> > torque curves).  Which do you think will win a drag race?  I will bet
> > every dime on the car making 100hp, and you should too, unless you want
> > to lose your money.
> >
> > -David
> >
> > lbaird119 at aol.com wrote:
> >> -----Original Message-----
> >> From: Terry Briggs <vbriggs at stny.rr.com>
> >> To: Vwdiesel at vwfans.com
> >> Sent: Sat, 5 Jul 2008 9:36 pm
> >> Subject: Re: [Vwdiesel] something worth trading the A4 in for
> >>
> >>
> >>
> >> to use an old racers saying, HP doesn't win races, torque wins races.
> >> Torque gets you moving, hp allows you to maintain speed once the 
> >> torque
> >> drops off. The curve of which determines how fast the end result is.
> >>
> >>
> >>
> >> GLAD to hear someone else say something like that!
> >>
> >> I've said for years that HP is what you brag about,
> >>
> >> torque is what turns the wheels.  :-)  It's SO hard
> >>
> >> to convince someone that a smaller hp diesel CAN
> >> outperform a larger HP gasser because it has MORE
> >>
> >> torque!
> >>      Loren
> >>
> >> _______________________________________________
> >> Vwdiesel mailing list
> >> Vwdiesel at vwfans.com
> >> http://www.audifans.com/mailman/listinfo/vwdiesel
> >>
> > _______________________________________________
> > Vwdiesel mailing list
> > Vwdiesel at vwfans.com
> > http://www.audifans.com/mailman/listinfo/vwdiesel
> >
> >
> M.I. 6
> Custom Design and Fabrication
> 2576 King Circle
> Corning, New York 14830
> Vbriggs at stny.rr.com
> 
> 
> ------------------------------
> 
> Message: 5
> Date: Sun, 06 Jul 2008 22:16:33 -0500
> From: David Schwarze <dschwarze at dfwair.net>
> Subject: Re: [Vwdiesel] something worth trading the A4 in for
> To: Vwdiesel at vwfans.com
> Message-ID: <48718A91.4010506 at dfwair.net>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
> 
> What you say below is simply not true.  Horsepower DOES move things. 
> More HP will get you down the road more quickly, regardless of torque.
> 
> The units of HP and Torque tell the story.  Power (hp) is a quantity 
> that you can use along with the weight of the vehicle, friction, 
> aerodynamic drag, etc. to predict how quickly a car will accelerate.  It 
> is a measure of how much work is being done.  Accelerating a car is work.
> 
> Torque is a measurement of rotational force which CANNOT be used to 
> predict how quickly a car will accelerate (why not, you say?  Because 
> "it depends" on the RPM).
> 
> For a real world example, take a sport bike.  That fits your definition 
> of "massive amounts of hp and little to no torque".  Ever race one of 
> those at a stoplight in your diesel VW?  I'm sure with the massive 
> torque of the diesel engine that poor sport bike didn't stand a chance, 
> right?
> 
> 
> Terry Briggs wrote:
> > You can have massive amounts of HP and little to no torque, and said 
> > car, plane {insert fav mode of transport} and you won't go anywhere 
> > fast but once you get it rolling, will be able to get some good speed.  
> > HP doesn't move anything, torque is what gets the world moving. Torque 
> > being a rotational force applied. if it doesn't have the grunt to twist 
> > the axle, not going to move much. Granted there is a hand in hand 
> > correlation between HP and torque, but it is possible to have hi torque 
> > and low hp and beat anything that pulls up next to you, you just need 
> > the right weight car, bike etc. Compared to a gasser, a diesel truck 
> > has low hp and very hi torque, off the line the gasser doesn't stand a 
> > chance, massive amounts of torque to get the load rolling, down the 
> > line, due to several factors like rpm capability of a gasser compared 
> > to a diesel things change but there are still more examples of diesels 
> > smoking the tires off of a gasser due to torque.
> > On Jul 6, 2008, at 3:07 AM, David Schwarze wrote:
> > 
> > 
> >>Sorry, but HP is what moves the car.  Period.  Torque does you no good
> >>if you don't have some RPM to go with it, and at that point you are
> >>talking about HP (because HP is basically torque X RPM).
> >>
> >>Torque is only useful as a measurement of the specific output of the
> >>engine at a particular RPM.  Good for measuring efficiency, not
> >>particularly useful in determining how fast a car will accelerate.
> >>
> >>The more HP you have, the faster the car will accelerate.  Rapid
> >>acceleration is a simple matter of commanding the motor to the RPM 
> >>which
> >>provides maximum HP and keeping it as close to that RPM as possible.
> >>Notice that I did not mention torque anywhere in that sentence.
> >>
> >>The advantage of a diesel is that it makes relatively high HP at low
> >>RPMs... so at low RPM you have an advantage with the diesel.  Great for
> >>towing.  At high RPM however the diesel loses it's advantage and high
> >>RPM is where the most horsepower is made.
> >>
> >>Consider two cars - one making 60lb/ft peak torque and 100 peak hp and
> >>the other making 100 lb/ft peak torque and 60 peak hp (with typical
> >>torque curves).  Which do you think will win a drag race?  I will bet
> >>every dime on the car making 100hp, and you should too, unless you want
> >>to lose your money.
> >>
> >>-David
> >>
> >>lbaird119 at aol.com wrote:
> >>
> >>>-----Original Message-----
> >>>From: Terry Briggs <vbriggs at stny.rr.com>
> >>>To: Vwdiesel at vwfans.com
> >>>Sent: Sat, 5 Jul 2008 9:36 pm
> >>>Subject: Re: [Vwdiesel] something worth trading the A4 in for
> >>>
> >>>
> >>>
> >>>to use an old racers saying, HP doesn't win races, torque wins races.
> >>>Torque gets you moving, hp allows you to maintain speed once the 
> >>>torque
> >>>drops off. The curve of which determines how fast the end result is.
> >>>
> >>>
> >>>
> >>>GLAD to hear someone else say something like that!
> >>>
> >>>I've said for years that HP is what you brag about,
> >>>
> >>>torque is what turns the wheels.  :-)  It's SO hard
> >>>
> >>>to convince someone that a smaller hp diesel CAN
> >>>outperform a larger HP gasser because it has MORE
> >>>
> >>>torque!
> >>>     Loren
> >>>
> >>>_______________________________________________
> >>>Vwdiesel mailing list
> >>>Vwdiesel at vwfans.com
> >>>http://www.audifans.com/mailman/listinfo/vwdiesel
> >>>
> >>
> >>_______________________________________________
> >>Vwdiesel mailing list
> >>Vwdiesel at vwfans.com
> >>http://www.audifans.com/mailman/listinfo/vwdiesel
> >>
> >>
> > 
> > M.I. 6
> > Custom Design and Fabrication
> > 2576 King Circle
> > Corning, New York 14830
> > Vbriggs at stny.rr.com
> > _______________________________________________
> > Vwdiesel mailing list
> > Vwdiesel at vwfans.com
> > http://www.audifans.com/mailman/listinfo/vwdiesel
> > 
> 
> 
> ------------------------------
> 
> Message: 6
> Date: Sun, 06 Jul 2008 21:13:30 -0700
> From: Roger Brown <r.c.brown at ieee.org>
> Subject: Re: [Vwdiesel] torque vs. horsepower (was: something worth
> 	trading the A4 in for)
> To: Vwdiesel at vwfans.com
> Message-ID: <487197EA.2090809 at ieee.org>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
> 
> David Schwarze wrote:
> > What you say below is simply not true.  Horsepower DOES move things. 
> > More HP will get you down the road more quickly, regardless of torque.
> > 
> > The units of HP and Torque tell the story.  Power (hp) is a quantity 
> > that you can use along with the weight of the vehicle, friction, 
> > aerodynamic drag, etc. to predict how quickly a car will accelerate.  It 
> > is a measure of how much work is being done.  Accelerating a car is work.
> > 
> > Torque is a measurement of rotational force which CANNOT be used to 
> > predict how quickly a car will accelerate (why not, you say?  Because 
> > "it depends" on the RPM).
> > 
> > For a real world example, take a sport bike.  That fits your definition 
> > of "massive amounts of hp and little to no torque".  Ever race one of 
> > those at a stoplight in your diesel VW?  I'm sure with the massive 
> > torque of the diesel engine that poor sport bike didn't stand a chance, 
> > right?
> 
> Torque, via the gearing in the transaxle, it what turns the wheels/tires to push the car 
> forward.  More torque, whether in raw form out of the engine or via reduction gearing in 
> the transmission equals more force transferred by the tires to the road and more force 
> acting on a given vehicle mass (or weight) results in an equal and opposite force (per 
> Isaac Newton) called acceleration.  The units of torque are the same as the units of work, 
> force over a distance.  And if you take things to finer and finer increments of time (in 
> mathematical terms), the RPM factor goes away, acceleration is defined as the derivative 
> of velocity with respect to time (dv/dt) and is simply reduces to the mass and the force 
> acting upon it.
> 
> Power (or horsepower) is in units of work per unit of time.  That will tell your how much 
> work an engine can produce over a given period time.  Since engine HP is a function of 
> torque and RPM, you can vary both of those factors via gearing, tire size, etc.  And since 
> HP is a combination of these two values (torque and RPM) and since in typical internal 
> combustion engines torque varies with RPM, it is hard to separate the two factors.
> 
> Imagine one engine with a very peaky torque curve with tuned intakes and exhaust made for 
> maximum power/torque output at some high RPM.  And then an engine with the same overall HP 
> but one with a fairly flat torque vs. RPM curve.  If you use both engines to accelerate a 
> vehicle, (assuming fixed gearing) you need to integrate the torque over the range of RPMs 
> from beginning to end to get the overall time to speed.  Think of taking the area under 
> the HP vs. RPM curve.  A broad flatter HP curve has more area under it than one that is 
> shaped like a triangle.  A flatter curve is the result of a torque that builds up at a low 
> RPM and holds fairly constant at the RPM rises.  A steeper curve is the result of an 
> engine where the torque keeps rising with RPM.
> 
> And yes, a 50 HP gas engine in a motorcycle will out accelerate a 50HP diesel engine in an 
> automobile.  Why?  Weight.  Put 50 HP behind a 300 lb. bike and put in gearing to drop the 
> high revving, low torque engine output down to a usable value for the load, that low 
> torque times the gear reduction results in a large torque at the wheel and that torque 
> times the lower mass equals higher acceleration.  Put 50 HP behind a 2000 lb. Rabbit and 
> guess what, it is slower to accelerate than a 6 times lighter motorcycle.
> 
> So it all really boils down to the fact that torque is the fundamental unit and is what an 
> engine produces.  RPMs are just the result of what the engine is connected to and what 
> that load does in response to the applied torque.  HP is just the derived product of the 
> supplied torque and the resultant RPM.
> 
> -- 
> 
>    Roger
> 
> 
> ------------------------------
> 
> _______________________________________________
> Vwdiesel mailing list
> Vwdiesel at vwfans.com
> http://www.audifans.com/mailman/listinfo/vwdiesel
> 
> 
> End of Vwdiesel Digest, Vol 57, Issue 9
> ***************************************
>