Perfect timing?

Drivbiwire

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The piston tops don't run hotter (maybe just a tad), the peak combustion pressure is simply higher. The higher pressure results in more complete combustion and this adds to the overall temperature in the combustion bowl (thus the increase in NOx).

Combustion occurs almost entirely in the bowl, if combustion is occurring so late as to expose the top of the piston to the actual flame front...you crack the piston or at the very least melt it.

This typically occurs with incorrectly mounted nozzles and incorrect sequencing of the injectors. Compound this with small nozzles (slower injection) and high performance tuning and the risk factors are pointing in the direction of a failure.

What I have found is that advancing timing insures that combustion occurs entirely in the combustion bowl. This insures that the ideal mixing of the fuel and air occur completely and in a controlled region designed for the stresses involved. Also the piston is cooled with oil so this further insures the margins required for safe operation of the motor at higher engine output or the slightly increased pressures more advanced injection timing settings result in.

Again I am purely of the opinion that combustion needs to be as complete as possible with the energy of the fuel being expended to drive the piston and insure the cleanest possible emissions. NOx may be higher with advanced timing but the reduction in PM goes a lot farther in terms of public perception of the diesel engine overall.

FWIW, we have tested TDI engines with all the NOx devices (EGR, Advanced timing) etc disconnected and found that the cars STILL meet all the emissions requirement...FWIW.

The funny part is that a gasoline engine put out more NOx than the TDI did, and this is with all NOx reduction devices inhibited on the TDI motor.

To sum it up, set the engine for best efficiency, lowest thermal stress on the downstream components (Turbo) and run with the least amount of soot particles generated that is possible for your specific configuration.

I only suggest:
-Advancing timing to the top of the range (mechanically) read by VCDS in basic settings mode
-IQ adjustement as needed to produce a light haze and no black smoke.

Do those two things and your engine regardless of tune, injector combination will be running at the top of it's game without impacting it's design life.
 
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Seatman

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That's something else I noticed is even less haze than before, I planted the foot today and there was just nothing in the mirror. Maybe I'll turn the fuel up a bit.
 

Satiro

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I had mine set to upper line, advanced...after reading an old link in this thread i tried to set static timing to a point where specified and actual matches, and resetting all timing adaptations... Before that, i had overboost issues, i couldn't floor it, after timing adjust overboost has dissapear!!! how is it possible? car feels stronger in low rpms and i can floor it in highway... why?
Thanks, regards
 
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FlyTDI Guy

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If nothing else, I've learned that just because YOUR (meaning mine) car acts a certain way after some modification, that does not mean that all other TDI of the same engine will act the same. For instance, I just read a thread on another gasser forum that says that advancing timing will increase low end torque while my experience over many cars and years says the opposite. Regardless...

What adaptation to your timing did you do? Advanced or retard it?
 

Satiro

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Hi, thanks for responding, i have all timing adaptations to 32768, and specified and actual are 3.0btdc! aren't those values too much dynamic timing advanced?
Thanks:)
 

Satiro

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Do you mean 3º BTDC at idle (903 rpm) when set to 32768?
Yep, 2.9ºbtdc at idle with 32768...if i change that value, i can see less than 1ºbtdc at idle... i have to 2.9btdc now and car feels fine, i have power in all range, and i can floor it again! i don't know why, but car runs a lot better in city and highway than before...:confused: before that, overboost appeared quickly and i had having one eye on the boost gauge permanently...

Before: static timing advanced
meas block 004 values: 1.3ºbtdc - 1.8ºbtdc 2.8%
Now: pump in the midline, where meas.block004 values matches
meas.block 004 values: 2.9ºbtdc - 2.9ºbtdc 73%

P.D: I drive car a lot this morning and i can confirm it feels a lot better than before... i can't understand it, but it is for sure
 
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FlyTDI Guy

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If the engine is completely warm, I would consider 3º BTDC fairly advanced. I've read up to 5º for some here but only by fully adapting. Stock for an ALH is more like 0-.5º BTDC @ 32768. Either the engine is not warm or your tune is possibly asking for more advance. I'm guessing you probably see around 21º-22º total advance @ WOT. Not really sure why your cold start value is so radically different between the two. I would not consider 3º harmful but on my ALH I run more like 2º. Any more and the pump is pretty loud until the warmup cycle is done. Timing is automatically advanced to compensate for coolant and fuel temps until things warm up a bit... usually a couple miles or more. Things are much quieter if I stay at 2º or less and I still get decent max advance. Bottom line, watch your mileage and EGT's for a while and if you're happy, leave things as they are. As to why you overboost when more retarded, dunno...
 
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Satiro

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If the engine is completely warm, I would consider 3º BTDC fairly advanced. I've read up to 5º for some here but only by fully adapting. Stock for an ALH is more like 0-.5º BTDC @ 32768. Either the engine is not warm or your tune is possibly asking for more advance. I'm guessing you probably see around 21º-22º total advance @ WOT. Not really sure why your cold start value is so radically different between the two. I would not consider 3º harmful but on my ALH I run more like 2º. Any more and the pump is pretty loud until the warmup cycle is done. Timing is automatically advanced to compensate for coolant and fuel temps until things warm up a bit... usually a couple miles or more. Things are much quieter if I stay at 2º or less and I still get decent max advance. Bottom line, watch your mileage and EGT's for a while and if you're happy, leave things as they are. As to why you overboost when more retarded, dunno...
Engine was completely warm, my ECU isn't stock but i don't know how much timing advance is asking the tune. I think its for injectors with stock POP.
It's true IP is louder at 3.0ºbtdc than at lower value. I will change adaptations for to see 2.0ºbtdc and will test it. I think my overboost issue fix is due to the static timing dead on instead of slighty advanced(65)? People here suggest to advance static timing to upper line on graph, but it does not work well for me, can it be the reason due i have stock POP injectors?

Thanks:)
 
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Seatman

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I wonder if it's to do with the older style engines, a fried of mine has the 1Z and if we set his timing advanced his car doesn't run as well but with mine set to the upper line (70) it runs superb.
 

Satiro

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It can be, but, what's the reason?
Seems like fully advanced static timing works well only with higher POP injectors...
Does the advanced static timing to compensate the longer opening time of higher POP pressures?
 
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Drivbiwire

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Yep, 2.9ºbtdc at idle with 32768...if i change that value, i can see less than 1ºbtdc at idle... i have to 2.9btdc now and car feels fine, i have power in all range, and i can floor it again! i don't know why, but car runs a lot better in city and highway than before...:confused: before that, overboost appeared quickly and i had having one eye on the boost gauge permanently...

Before: static timing advanced
meas block 004 values: 1.3ºbtdc - 1.8ºbtdc 2.8%
Now: pump in the midline, where meas.block004 values matches
meas.block 004 values: 2.9ºbtdc - 2.9ºbtdc 73%

P.D: I drive car a lot this morning and i can confirm it feels a lot better than before... i can't understand it, but it is for sure
Your injector sequencing is suspect here...

Pump timing is pushing one thing, the injectors are not breaking up the single pulse correctly into the the two distinct stages. Compound incorrect settings with incorrect sequencing and the car won't run right.
 

Satiro

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Your injector sequencing is suspect here...
Pump timing is pushing one thing, the injectors are not breaking up the single pulse correctly into the the two distinct stages. Compound incorrect settings with incorrect sequencing and the car won't run right.
Hi DBW, thanks for your help. What do you refer with injector sequencing? pressure of both injection stages?
i'm thinking in setting injectors to 270/390bar soon, and 11mm head...
Are my stock injector pressures the reason of my center line static timing power improvement? Car feels really nice now, runs great, starts fine...
THANKS:)
 
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soup nazi

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Hi chaps
I decided to test the methodology here and found that by running the I/T at the upper green line on the graph the actual timing is indeed advanced of that requested until the engine is put under load at speed. Pretty much says it all.

However I do have another reading that I would like some clarification on. In measuring blocks under block 008 there is three windows for I/Q. They read as follows

Window (1) 1.2mg/str
Window (2) 28.2mg/str
Window (3) 22.2mg/str

This says it's the actual I/Q so why the wild differences between channels???

SN
 

Seatman

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Well tonight I decided to give my car some beans and have to say there is deffinitely more power further up. Straight up to the 100mph was really easy but I didn't try further as my springs are shot so it gets a bit tricky. Even better was after driving like a complete nutter the car runs even better than it did after doing the timing, bonus.
I've decided I'm going to focus on tidying the car up this year and do the tune next year, maybe get a cam or followers or both, it needs something in there anyway as it's a bit tappy from one of the followers. I expect it copuld just be one sticking.
Back on topic though, the timing definitely worked for me, there's absolutely no doubt what so ever. Cheers drivbi.
 

FlyTDI Guy

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Well tonight I decided to give my car some beans and have to say there is deffinitely more power further up. Straight up to the 100mph was really easy but I didn't try further as my springs are shot so it gets a bit tricky. Even better was after driving like a complete nutter the car runs even better than it did after doing the timing, bonus.
I've decided I'm going to focus on tidying the car up this year and do the tune next year, maybe get a cam or followers or both, it needs something in there anyway as it's a bit tappy from one of the followers. I expect it copuld just be one sticking.
Back on topic though, the timing definitely worked for me, there's absolutely no doubt what so ever. Cheers drivbi.
Good to hear... So you just advanced your static timing to the green line (or so) and no adaptation (32768)? Really, DBW has it right in that there's no real magic in timing and all the fiddling in the world only results in trade-offs in some form or another. It's a matter of some experimenting 'till you find what your car likes. It's important to set or check everything from the ground up, including your crank/cam/pump timing and then set static as recommended for a start point. Checking your warm idle timing is next and, if they don't match, you can bring that in through adaptation. Another is maximum advance available so a few WOT runs, look at specified vs actual and make sure you're reaching and holding that number.

Glad your car is performing better and enjoy... hope your new springs work out well for you.
 

Seatman

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Good to hear... So you just advanced your static timing to the green line (or so) and no adaptation (32768)? Really, DBW has it right in that there's no real magic in timing and all the fiddling in the world only results in trade-offs in some form or another. It's a matter of some experimenting 'till you find what your car likes. It's important to set or check everything from the ground up, including your crank/cam/pump timing and then set static as recommended for a start point. Checking your warm idle timing is next and, if they don't match, you can bring that in through adaptation. Another is maximum advance available so a few WOT runs, look at specified vs actual and make sure you're reaching and holding that number.

Glad your car is performing better and enjoy... hope your new springs work out well for you.

Cam, crank and pump are spot on, no problems there. My static timing was at about 55 and the car was fine, I do have a slightly dicky egr that causes a slight hesitation at really low throttle but I tested the car with that disconnected and it was super smooth all the way so that's no problem either. Going on drivbi's advice with the bosio nozzles I have my IQ around 6.5 and the timing I've put to 70 in the graph. Even that small change from 55 to 70 has really made a difference to the overall running and power. I used to get a light haze at wot but that's now gone so will be increasing the fuel a bit at some point, doesn't add much but it's free so why not.

Warm idle timing?
 

Matt-98AHU

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That is the key to understanding timing.

The #3 injector ONLY monitors when injection starts. It cannot measure pressure and the Quantity adjuster controls injection duration (as well as delivered quantity).

Fuel is being compressed to 19,000 psi in some cases so SOI is just that the very start of injection...plenty more goes on during a full sequence!

Therefore:

What if the ECU commands injection to start at the bottom of the cam plate slope?

Then

What if the ECU commands injection to start at the mid range of the cam plate slope?

then

What if the ECU commands injection to start at the upper range of the cam plate slope?

Since Static timing removes all electronic corrections, you are setting the point on the slope that pressure rises. The ECU only looks at crank, fuel temperature and the #3 to monitor the cam plate position based on the pressure response at the #3 injector. This removes all wear factors and gives you a direct read on pressure response at the injector based on the actual cam plate position (slope).

How is pressure and pulse duration affected as well as peak pressure?

Keep in mind that in all cases mentioned above, the #3 injector opened exactly when the ECU expected it to...What happened afterward was determined by where the injection sequence began on the cam plate slope.
I'm not quite sure I follow on the cam plate position vs. the ECU's requested/specified start of injection. The position of the cam plate IS what is largely responsible for start of injection. Maybe tweaking the quantity can affect it somewhat, but the cam plate itself is what is responsible for start of injection.

When you mechanically advance the pump, you're basically advancing the cam plate's position relative to the engine to affect this. Then the computer has an additional say by moving the collar with the rollers on which the cam plate rotates (via hydraulic piston on the bottom of the pump, hydraulic pressure to said piston regulated by the timing advance solenoid), thereby directly affecting when the cam plate hits the rollers, thus affecting timing.

I'm not sure I see how many other factors determine timing here. The injectors are purely mechanical, the computer can't directly tell them when to fire (which is one of many reasons why it's so important to have injectors pop-tested and balanced).

If the ECU was commanding injection to commence on either side of the cam plate's slope, it would attempt to fix this by telling the N108 to either increase or decrease pressure to affect a change in the cam plate's position to obtain the correct timing. The injection event SHOULD start at the cam plate's peak or just prior to it, no?

Of course then there's the fact often times pumps get set mechanically advanced to the point where the computer cannot pull back timing any further, hence aNUT's observations in the thread linked on the first page.

It has been my observation that when a car is fully warmed up, what the computer wants to see (with stock programming) for timing at idle is further retarded than TDIClub's creed of setting mechanical timing as far advanced as possible while still remaining within range. As can be observed in measuring block 000, field 2 when switching between measuring blocks and basic settings. If the number doesn't drop any when you switch to basic settings, the pump is mechanically set too advanced compared to what the computer is requesting. Meaning the cam plate, even with the N108 duty cycle at 0, is further advanced than what the computer wants to see. The cam plate is what determines timing... How on earth would one be able to determine if SOI is occurring before or after the apex of the cam plate's lobes?
 

mazoul72

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lyon_france
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110cv_november 2001
problem with pre-advance timing N108

Hello,

on my 004 logs , my real advance can't reach set in advance .
It is too low or too high but i think i don't have enough internal pressure with valve .
I don't understand explanations on this post ,
Does anyone has photo of modification ?

Regards.
 

kiva822

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Chico, CA
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I'm not quite sure I follow on the cam plate position vs. the ECU's requested/specified start of injection. The position of the cam plate IS what is largely responsible for start of injection. Maybe tweaking the quantity can affect it somewhat, but the cam plate itself is what is responsible for start of injection.
When you mechanically advance the pump, you're basically advancing the cam plate's position relative to the engine to affect this. Then the computer has an additional say by moving the collar with the rollers on which the cam plate rotates (via hydraulic piston on the bottom of the pump, hydraulic pressure to said piston regulated by the timing advance solenoid), thereby directly affecting when the cam plate hits the rollers, thus affecting timing.
I'm not sure I see how many other factors determine timing here. The injectors are purely mechanical, the computer can't directly tell them when to fire (which is one of many reasons why it's so important to have injectors pop-tested and balanced).
If the ECU was commanding injection to commence on either side of the cam plate's slope, it would attempt to fix this by telling the N108 to either increase or decrease pressure to affect a change in the cam plate's position to obtain the correct timing. The injection event SHOULD start at the cam plate's peak or just prior to it, no?
Of course then there's the fact often times pumps get set mechanically advanced to the point where the computer cannot pull back timing any further, hence aNUT's observations in the thread linked on the first page.
It has been my observation that when a car is fully warmed up, what the computer wants to see (with stock programming) for timing at idle is further retarded than TDIClub's creed of setting mechanical timing as far advanced as possible while still remaining within range. As can be observed in measuring block 000, field 2 when switching between measuring blocks and basic settings. If the number doesn't drop any when you switch to basic settings, the pump is mechanically set too advanced compared to what the computer is requesting. Meaning the cam plate, even with the N108 duty cycle at 0, is further advanced than what the computer wants to see. The cam plate is what determines timing... How on earth would one be able to determine if SOI is occurring before or after the apex of the cam plate's lobes?
hey matt...how would amend this for non-stock tunes. I remember you and I talked about it, but I can't recall at all...
 

mazoul72

Member
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Jul 24, 2011
Location
lyon_france
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110cv_november 2001
Hello,

on my 004 logs , my real advance can't reach set in advance .
It is too low or too high but i think i don't have enough internal pressure with valve .
I don't understand explanations on this post ,
Does anyone has photo of modification ?

Regards.
Hi,
aNUT , can you help me about this problem ?
Thanks in advance .
 

tdileon

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Dec 14, 2015
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England
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Seat leon, vw golf
I notice my tdi alh idles slightly rough eg when started from cold revs at 1200rpm for 2mins before falling down to 903rpm . Checked group 4 it shows requested is 9btdc but mine is 1btdc at ignition on only.
When started requested is around 0 at my actual is about 1btdc .
should I adjust mine to atleast 4 or 5 btdc?
 
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