Bumping the IP timing one tooth

[TylerDurden]

[libbydiesel]

^^ Hence the value of hillbilly timing... you hear the light-off.

The pulse can tell you... when the pump strokes?... or when the injector opens? Neither of which represent start of combustion.

Pulse adapter tells you the start of injection.  With any reasonable injector quality the start of injection is directly related to the start of combustion.  I have tested a variety of diesels using my pulse adapter and strobe and it is repeatably accurate with an array of pop pressures and various aged pumps.  While it is true that an injector that is worn-out might skew the reading slightly, that's kind of like saying that the best way to do a front-end alignment is to eyeball it because when yer ball joints and tie-rod ends are worn out and sloppy no measurement is gonna make the darn thing drive right.

[TylerDurden]

Pulse adapter tells you the start of injection.  With any reasonable injector quality the start of injection is directly related to the start of combustion.

Obviously ZV (ignition lag) increases to the tune of ~5^o when an engine is cold, so it isn't a hard and fast rule at all.

I'm confident that lower compression has similar effects, since advancing static timing helps an engine with worn rings start more easily and smoke less.

[theman53]

so far with my lowered compression I do not see advancing the timing as a starting helper. It seems to make the engine turn over slower and what is needed is cranking speed. I have seen that once started it likes the cold start advance to keep going, but not while cranking.

[Gizmoman]

I'll use the dial when I bump it one tooth this weekend. First I'll take off the valve cover and set the cam slot. Then mark TDC on my flywheel. then insert the dial indicator into the pump and see where I am.
Once I bump the sprocket one tooth I'll rotate it pump to some number on the dial slightly lower than the number I found previously and see how it runs. (after turning it over by hand twice).
My goal is to be running solid by Thanksgiving so we can take the van to our kids party about an hour away. I can take backroads there so I can do a good brake-in run without constant freeway driving. Then if we eat too much turkey, we can sleep in the van

I'll be looking for a pulse light as I think it's the best way to get solid numbers, but right now nothing I find catches my attention.

[CRSMP5]

i can say low comp and advanced make it hard to start cold... when old idi wears out.. they hit and fire off quicker if you pull the advance as it lights off.. pre pulled they do not hit to fire.. they will flood out..

seen it few times... cold helps as oil thickness slowed cranking speed too..

so yes too advanced not good.. if your testing for that.. pulling the adv should help.. when doing timming make sure its pushed in too..

in theory you could even fine tune it via adv the pump.. then using the adv cable to give more to see if you went too far..

[libbydiesel]

Pulse adapter tells you the start of injection.  With any reasonable injector quality the start of injection is directly related to the start of combustion.

Obviously ZV (ignition lag) increases to the tune of ~5^o when an engine is cold, so it isn't a hard and fast rule at all.

I'm confident that lower compression has similar effects, since advancing static timing helps an engine with worn rings start more easily and smoke less.

I am very familiar with what a well-timed vw diesel sounds like and I have very discerning hearing.  With my setup I have tested several different engines with rebuilt or new pumps and rebuilt injectors set to spec (or closer together than spec) and timed to spec in order to get a good baseline reading.  On my particular setup, 12°BTDC is the best timing spec.  This has held true for setting the timing on many injection pumps and engines both old and new.  I have done so on engines with varying compression even as low as 250 psi or so on each cylinder and it still results in the best timing setting.  This has also held true for experimentation with different pop-pressures, different sized distributor heads/plungers, and different camplate profiles.  It has always resulted in the best possible hillbilly setting available.  

While the injection lag varies with engine temp, the start of injection does not, that's true, but obviously you want to time the engine for normal operating temperature.  That is specifically why diesels often do not run as well when cold.  Fuel type also changes the timing slightly.  That is not to say that you need to wait for the engine to warm up before timing with the pulse adapter (you probably do with the optical one, tho) precisely because the start of injection does not vary with engine temp.  I believe that bio-diesel has an increased injection lag.  But again, after finding a good baseline, according to my extensive experience using the pulse adapter, it does a better job at fine tuning the timing than any hillbilly can by ear and quicker and easier to boot.    

[Gizmoman]

I finally found a site that offered a unit with a 6mm clamp - standard. All the other sites made you get it with a 1/4" clamp, then purchase and additional cable and clamp for another 125 bucks.

It cost around 200 plus 8 bucks shipping. Can't wait to play with it. Considering what I've spent so far, its a drop in the bucket

Ferret Instruments V765-03 - Diesel Injection Detector with 6.0mm Clamp
http://www.tooldiscounter.com/ItemDisplay.cfm?lookup=FERV765-03

[Gizmoman]

Very informative graph Tyler - thanks for posting it.
I see that 12* BTDC at the cam is where things begin to happen in the pump. Maybe a dumb question but am I supposed to be looking at the cam or the flywheel when using a light? I would assume its the flywheel unless they are both the same - just can't get my head around it and as usual, probably over-thinking it.

[libbydiesel]

As I mentioned before, the approach I took when I got a pulse adapter was to take a reading from an engine that was tuned with fresh pump and injectors all set to spec in order to get a baseline reading.  For my setup 12° BTDC on the flywheel is the optimum timing setting.  Your pulse adapter is a different model than mine and so may read slightly differently, but that would be an excellent starting point. 

[TylerDurden]

Giz,

Something to explore: using the pickup for comparing the timing of all cylinders.

[Gizmoman]

Giz,
Something to explore: using the pickup for comparing the timing of all cylinders.

It would be interesting Tyler, although I'm not sure what I would do with the results - do a mean average? Wish I had the pulse adapter now but it won't be here till mid next week
No matter, I need to remove the valve cover anyway because it's leaking a bit - so I can look into that while I set my TDC mark on the new flywheel. Not sure how to find 12* BTDC. I figure I'll use a digital protractor level on the front belt pulley and go from there. The licence plate folding open sure is handy
Very curious to see what the dial indicator says. As this was the first time I ever rebuilt a diesel, I'm pretty stoked that it runs so well right off.

However, I must have done something way wrong as CRMP5 and theman have pointed out. All I know right now is I just need more poop when I'm off boost. Last weekend when I turned the IP clockwise, it got even quieter. That's why I think it needs to be turned CCW but as I mentioned, it must be at the bottom of the adjusting slots as a 2' bar wont move it (and it's not hitting the head), so I think the belt needs to jump a tooth.

[TylerDurden]

It would be interesting Tyler, although I'm not sure what I would do with the results - do a mean average? Wish I had the pulse adapter now but it won't be here till mid next week
No matter, I need to remove the valve cover anyway because it's leaking a bit - so I can look into that while I set my TDC mark on the new flywheel. Not sure how to find 12* BTDC. I figure I'll use a digital protractor level on the front belt pulley and go from there. The licence plate folding open sure is handy

If marking TDC using a hose and fluid, BDC (TDC for 2 & 3 ) is simply marked when the fluid is at opposite range of travel.

If all is well, there should not be any difference between lines. But if significant difference is noted, it would be worth a pop test on the outlier, or swapping delivery valves to see if the difference also swaps.

[Gizmoman]

I used the clear tube stuck in a glow plug hole a couple weekends ago on a friend's engine.  It worked PERFECTLY for an EXACT TDC mark.  I could easily tell the exact point where the liquid stopped moving the one way and started moving the other way. 

Can't argue with that.
I'll do the fluid in hose test and also the cam position check at the same time. They both should be close though, or this thread would have been titiled "I think I bent a valve"

[libbydiesel]

Not sure how to find 12* BTDC. I figure I'll use a digital protractor level on the front belt pulley and go from there. The licence plate folding open sure is handy

My timing light has the 'advance' and 'tach' functions.  With the advance function, you can advance or retard the timing of the strobe relative the actual signal.  In order to take a reading I use set the advance function on the light so that it is showing the flywheel timing mark lined up with the pointer on the bell housing.  In setting the timing, I set the advance function to 12° BTDC and then rotate the injection pump (or adjust the sprocket on 2-piece sprockets) until the flywheel mark lines up with the pointer. 

If I was using a timing light that was not equipped with the 'advance' feature, I would divide 360° by the number of flywheel teeth in order to know the number of degrees per tooth and then divide 12° by the (degrees per tooth) to find out how many teeth away from the TDC mark I needed to place my timing mark.  I would then adjust the pump until the strobe showed the new timing mark lined up with the pointer.