advanced timing pros and cons

[wadem]

Hey guys, have been messing around with my timing over the last few weeks and have a question for the group. What are the cons, if any of having you timing too advanced? I have a 96 Jetta with the AAZ engine and the adjustable IP sprocket, so adjusting the timing and playing with it is very easy and maybe a 5 minute procedure everytime. What I have found with my engine is that it seems to run very well with what I determined to be a very advanced setting. Keep in mind that I have not used the timing tool on this procedure. The adjustable sprocket on the IP is very easily set by just lining up the adjustment holes and then locking the pump at that point while you secure the 3 bolts on the sprocket. I have done this for 2 years and have always been happy with the results. 2 weeks ago i decided to start advancing the timing in very small increments, like a 1/2mm at a time. What I have ended up with is a very happy engine, it starts better, no smoke (never was at old setting either), more power,etc. But again I think that it is too advanced, I assume this because at a slow acceleration until about 2200 rpm i am getting a slight pinging or Dieseling, that wasn't there before, but the car runs better in every other way.
  So again just wondering what the cons of having a higher then normal advanced setting would be? Other then been a little louder,  i can't think of any. So why would you ever want to run with a more retarded setting? Are there any pros to doing this? Why doesn't everyone run with a more advanced setting then published or listed in the book? I can't seem to find a reason, as my car is running the best its ever ran, OK a little louder but still great!

Cheers

Wade

[8v-of-fury]

Pros to retarded are emissions, and sound as you have noticed. Diesels in the 80-90's were loud and smokey.. and not many liked them in North America because of what GM screwed up with the Detroits (yeah yeah, keep it in your pants GM guys, they were not a good engine design lol!)

I and many others run at the same spot you are right now, to where it starts to clack-clack as if you poured marbles down the intake. You are right on the brink of too much timing, but that is ok because it can't really hurt anything unless you go way overboard!

Try this, on a cold start pull out your COLD START handle prior to cranking. Do you notice the engine turns slower then with it in? If so, you are right on the brink of injecting fuel too soon. If it does slow it down you are injecting fuel so early it is fighting the piston on its way up in the bore! Which is no good for starting, perfect for warming up as it will be part of the compression as well, and not so good for high rpm use as it will be again fighting the piston.

[ORCoaster]

Listen to 8V on this.  You are right on the edge of too much timing and an engine that it fighting itself to get started may not start of you are real cold.  Pistons that are supposed to be going up and are compressing fuel that is burning at the high RPMs isn't doing you any good mileage wise. 

Why don't we all run them higher than spec?  Some should as the pump and such do wear over time, the new diesel is thinner than expected and some like that diesel clack.  But others not so much, in fact they really don't like it at all so they would chose less advance. 

You have the newer style injection system on it compared to us Old School guys and gals that are reliving our 80's.  Injectors break under different pressures, and some like the retarded timing or advanced timing to compensate.  Type of fuel makes a difference, WMO, WVO, or diesel be it bio or regular or stolen from the locomotive all can change the timing. 

You have found the place to be for your Jetta.  I would be very interested to know what your timing actually is compared to where you were before starting this process.  And what the IP pressure is at both settings.  Again timing changes with pressure or at start with the cold start lever.

So you have figured out the PRO side of the equation with advancing it.  Advance it a bit more and listen to all that pinging for miles on end and you will figure out the CON side.    By luck you stopped one setting short of demonstration I think. 

[tyb525]

I set my pump by the book with the correct dial gauge setup and got lots of white smoke at startup. That was at 1.00. I bumped it up just a little more without using the gauge and it runs better and doesn't smoke hardly at all at startup.

I was thinking advanced timing would actually be better at high rpms, because since everything is sped up, wouldn't you want it injected a little sooner than at idle, or does the pump already take care of that? I know gas engines are more advanced at higher rpms, but that's a gas engine.

I like the diesel clatter, part of the reason I drive it. They kind of sound like a 2 stroke detroit to me, which I like. The 2-stroke detroits were great engines, but the 6.2 and 6.5 4-stroke were terrible.

[ORCoaster]

Smoke at idle means it was timed with retard.  Now that you have that corrected you have to be careful of the advance that happens automatically as the RPM's increase.  That is where the IP will produce more pressure and move the internals of the pump to get to the higher advanced timing.  If you are already there with a manual move at idle then you will be too much advance at those higher RPM's and the piston will not like the earlier than should be entry of the fuel.  Compression stroke will still be trying to finish and the power stroke will be on.  Not efficient.

[tyb525]

Well I know I didn't move the pump much, just a hair, not so much the CS slows cranking speed, but I can still hear an increase in clatter when I pull it. I didn't want to advance too much, just enough to get rid of the embarrassing amounts of white smoke at startup, now it is down to a normal amount based on numerous videos I've watched...I don't care too much about performance, I'm going for mpg's although they have been down since it got real cold.

I don't think I can control how the pump advances as rpm's increase, can I?

[8v-of-fury]

Just a hair or two is enough to jump 0.005"or more, and that is enough to make a substantial difference. Smoke is down and cold starts are good, then you are at the perfect spot .

You can kind of control your pumps advance.. Depending, do you want it to advance quicker or slower and why do you want this?

[TylerDurden]

I have found that advanced timing reduces smoke at high rpm and increases fuel economy at highway speeds. I'm assuming the smoke is due to injector lag, which is why dynamic advance is implemented; but over time, it seems that the dynamic advance is not as limber, due to wear, weaker delivery valves, low internal IP pressure and out-of spec injectors. Advanced timing does make a bit more clatter in the lower rpm on my engines.

I have also noticed more clatter of a different tone when timing is overly retarded... pulling the CS lever seemed to reduce that clatter, so I advanced my IP and that made the situation better.

[tyb525]

I dont think I need to change how the pump advances at higher rpms. But I have noticed I get worse mpgs at 70mph vs 55 or lower (around 4-5 mpg difference), but I think that is fairly normal.

[TylerDurden]

Aero drag is the big hit. Drag increases to the cube of velocity.

[wadem]

OK heres the scoop on my 96,
  There was no distinguishable cranking speed change with the CS lever pulled VS not pulled. I as well can detect a slight clatter tone change when going from CS lever not pulled, to pulled. Also, the cold start does seem to make a difference on the quality of the start  when it is cold(go figure). After it started today I immediately pushed the lever back in and although it continued to run smooth, there was a miss or misfire on a couple cylinders for about 30-45 seconds or so. This cleared right up upon activation of the CS lever again.
  This leads me to believe that my setting is not too far advanced. If it was i dont think there would be any change when you pulled the CS lever, am I correct in thinking this?

Wade

[TylerDurden]

I tend to agree.

I'd say you're right on the button. All those details are what I consider optimal when assessing timing my tweeks.

[bbob203]

I tend to agree.

I'd say you're right on the button. All those details are what I consider optimal when assessing timing my tweeks.

I concur.

[wadem]

OK! good news. The next test will be to see if MPG is the same as before, better, or worse.

Cheers

Wade

[8v-of-fury]

The fact that the CS lever stops the missing and only advances enough to smooth out without being overly advanced, then I too agree you are timed perfectly for your exact setup.

Congratulations, you have just tackled and damn near mastered the most difficult thing this car/engine can and will throw at you

Being that you are doing this with some attack plan in mind.. would you mind referencing your new mileage and then maybe advancing a hair more again and seeing what happens? If it still stumbles cold without it pulled then maybe it could even use a bump more, not necessary.. but experimenting is always fun eh? lol