Diesel Pulse Adapter Info Thread

[libbydiesel]

Having more overall advance does not necessarily change the advance curve until you are above the rpm where the stock pump would stop advancing. 

If the dynamic advance doesn't match the engine rpm properly then timing the engine properly is not possible with any method.  If it advances too quickly, you will either have it very clattery at higher rpms (if you set the timing well for idle) or a dog off the line (if you set the timing for higher rpms).  If the advance is too slow then the reverse is true.  

If the advance curve is correct then a proper timing spec for the entire rpm range is possible.  In that case, any timing method can arrive at that 'sweet spot' and of the timing methods I have used (dial indicator, hillbilly and pulse adapter) the pulse adapter is the quickest, easiest and most accurate way to do so.  

[theman53]

Giles just says since he builds so much dynamic advance into the pump the static timing isn't as nessesary. He says to shoot for .90-.95mm on my pump is why I ask.

[745 turbogreasel]

One of the sweetest things about the pulse adapter is it lets you return to  a known spot in  seconds after havign something apart for service.  Also you can   use it to check you advance function and  curve, which you will never accomplish  by hilbilly.

[Toby]

But, how close is the book value to the typical sweet spot?

In testing a wide variety of engines/pumps/injectors with the diesel pulse adapter, provided the dynamic advance is working properly, the 'sweet spot' is within 1/2° of 12°BTDC with my setup.  That wide array of engines/pumps/injectors includes both fresh and well-worn VW IDI, VW TDI and Mercedes IDI engines with both fresh and well-worn pumps/injectors.  On the VWs, I have also checked the plunger lift on several setups in order to find what the plunger lift measurement coincides to with a particular pump or set of injectors.  The plunger lift setting can vary fairly significantly but the 'sweet spot' with the pulse adapter does not.

That is not something you could know unless you are doing some kind of performance testing at different timing specs. They may all run well at your 12* setting but you can only know if its the sweet spot by performance testing other settings as well. Are you saying that you did this on some large number of VW diesels.

FWIW It strains your credibility that every one you "tested" ran best in the same spot.

[theman53]

But, how close is the book value to the typical sweet spot?

In testing a wide variety of engines/pumps/injectors with the diesel pulse adapter, provided the dynamic advance is working properly, the 'sweet spot' is within 1/2° of 12°BTDC with my setup.  That wide array of engines/pumps/injectors includes both fresh and well-worn VW IDI, VW TDI and Mercedes IDI engines with both fresh and well-worn pumps/injectors.  On the VWs, I have also checked the plunger lift on several setups in order to find what the plunger lift measurement coincides to with a particular pump or set of injectors.  The plunger lift setting can vary fairly significantly but the 'sweet spot' with the pulse adapter does not.

That is not something you could know unless you are doing some kind of performance testing at different timing specs. They may all run well at your 12* setting but you can only know if its the sweet spot by performance testing other settings as well. Are you saying that you did this on some large number of VW diesels.

FWIW It strains your credibility that every one you "tested" ran best in the same spot.

I see your point toby. You are thinking that if he hasn't tested 6 degrees bTDC then how would he know that 12 bTDC is best? Maybe he can chime in on how he started this way? Maybe he timed by ear and then ran it at a known spot and recorded where he liked it best with the light? Maybe he used the dial indicator and timed it to each .01mm from .90 to 1.20?

    I think it is kind of like my old ford 400. I had 2 of them, my friends had them as well. With the 9 or 10 we had we played with timing settings from 0 TDC to 30 TDC until we found that all of them liked around 15-18 bTDC IIRC as the best for all our trucks and broncos. Now granted this wasn't 500,000 vehicles of testing, but it was enough that we all knew that they did the best performance wise to all of our "hill tests" and butt dynos that we went with it. Also, since I was the only one with the light they were not changing it in between, so we would do a day of running it and report back. Some of it was personal preference, as we all wanted the snap off idle, but with the short and long bed trucks and broncos we were all about the same on the timing we liked. Say all that to say this, Libbydiesel may have only tested a few and his results are best for what he likes. It sounds like he has timed at least 10 vw diesels in various different models and they all seem to run best for him from 11.5 to 12.5 bTDC. I think it is a little subjective to what you or I may like, as you could possibly want the power to come on differently than he does, but I don't think he is saying this is the "only" setting. I took it as this is the one that he found best and if you use a similar adapter it probably would be a great idea to start there. Also, with different pumps he was saying that the dial indicator plunger lift setting varied, but his timing light didn't, so I would think that would add to the credibility not take away.

[745 turbogreasel]

I think  it might be sort of an inescapable law of physics if you have a 3" bore, prechamber and dynamic advance that it should start from right around there.

[TylerDurden]

So, bore change can create compression change and static timing may need to be adjusted.

12^o BTDC may be a fine place to start, but performance tells all.

[745 turbogreasel]

no, I'm just thinking a, engine  with a 4,5.or10 inch  bore might need to start the fire a little  sooner.

[rbremiller]

I've come across that same 12º# in the GM 6.2, and VE pumped Cummins forums in similar conversations about pulse adapters.

[libbydiesel]

The only factor in that list that is engine specific is compression.  Lower compression has an effect on cold start and pre-warm up operation but, as I've said before, does not seem to have any significant effect on the optimal timing once the engine is fully warmed up.

I've come across that same 12º# in the GM 6.2, and VE pumped Cummins forums in similar conversations about pulse adapters.

That's interesting to note.  I haven't frequented any of the GM or Cummins forums and yet came to the same conclusion independently.  It's also interesting to note that the Cummins 12v engines had a 17:1 compression ratio instead of the VW IDI 23:1 ratio.   

[Toby]

So then your *12* is best* was from a "thought experiment" and not from actually data. Or perhaps you read it somewhere?

[libbydiesel]

How could you possibly come to that conclusion?  Bizarre.  You probably ought to read this thread.

[bbob203]

I think he didn't.

[Toby]

Oh, no I did read the thread. I asked him whether he had ever done any real world data gathering to substantiate his 12* +/- .5* for all kraut diesels and he went off waxing about theory. In almost every case where someone states categorically that such & such is the case and presents unreasonably exact data there is a reason. Whether it is wishful thinking, or self deception, or fabrication, one can never be sure. In the real world the best empirical data has an error/noise rate of more than the 1/730 that he is claiming. (.138%)

It is not believable that every diesel motor would run best when set at the same timing at idle. A motor with an IP with a faster advance curve will almost always run better if the timing at idle is retarded a bit from what most VW diesels come with. Conversely if the IP advance curve is slower, that motor will run way better with the timing at idle is more advanced, since that way the timing will be closer to optimum in the RPM range where most of the driving is done.

LD claims that is not the case.

[bbob203]

I'm certain though I am speaking for him... He has tested his theories on more than a few engines.. He alone has 3 home built vanagon tdis, a benz 300d and a vnt 1.6 rabbit.