Adjust Fuel Injection Pump Advance

If you remove the TDI engine cover and look at the fuel injection pump, there is a cap near the bottom, looks like a power transistor, held on by two screws, one at each end. I understand that there is a timing advance/adjustment capability under this cap. Anybody know more about this?

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Boundless
1997 Jetta TDi

That's part of the automatic advance mechanism (it's where the actuator lives) but that's not where you adjust the timing.

Before even THINKING about fiddling with this, get your hands on a VAG-COM and find out where the timing is now. (More later.) It may not be necessary to do anything.

To adjust the timing on an A3/B4, you loosen the 3 bolts which hold the front flange of the injector pump to the mounting bracket and 1 more bolt which supports the rear of the pump, in order to gain access to two of the 3 bolts you'll have to remove the upper timing belt cover and rotate the engine until you can get them through the holes in the sprocket. Also crack loose the fuel line fittings. Then rotate the pump a little bit (just like adjusting distributor timing in the old days). Snug everything up, DO NOT OVERTIGHTEN the injector lines, then start the engine and re-check the timing. It is a trial and error process.

On the A4 cars, you take off the upper timing belt cover, loosen the 3 bolts which hold the outer part of the pump sprocket to the hub, shift the sprocket relative to the hub, and re-tighten. Once you get it set up, replace the 3 bolts with new ones (do them one at a time so you don't lose your setting).

Now for the fun stuff: explaining how it works. The injection timing is under automatic control, regardless of your manual setting UNLESS the automatic control reaches the limit of its travel (in which case it obviously cannot adjust it any further). Also the manual setting affects injection timing during starting, because the automatic systems aren't operating at that time.

If the computer wants 2 degrees BTDC, it will get 2 degrees BTDC, unless your manual setting doesn't allow that setting to be achieved.

Stock timing at warm idle is 0.4 degrees BTDC. Mine is set to 2 degrees BTDC - it's advanced far enough that the computer cannot retard the timing below 2 degrees BTDC at idle.


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Brian P.
'96 Passat TDI mit UPsolute und 1k resistor
(no responsibility accepted if you try this and blow up your car...)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by GoFaster:
That's part of the automatic advance mechanism (it's where the actuator lives) but that's not where you adjust the timing.

Before even THINKING about fiddling with this, get your hands on a VAG-COM and find out where the timing is now. (More later.) It may not be necessary to do anything.

To adjust the timing on an A3/B4, you loosen the 3 bolts which hold the front flange of the injector pump to the mounting bracket and 1 more bolt which supports the rear of the pump, in order to gain access to two of the 3 bolts you'll have to remove the upper timing belt cover and rotate the engine until you can get them through the holes in the sprocket. Also crack loose the fuel line fittings. Then rotate the pump a little bit (just like adjusting distributor timing in the old days). Snug everything up, DO NOT OVERTIGHTEN the injector lines, then start the engine and re-check the timing. It is a trial and error process.

On the A4 cars, you take off the upper timing belt cover, loosen the 3 bolts which hold the outer part of the pump sprocket to the hub, shift the sprocket relative to the hub, and re-tighten. Once you get it set up, replace the 3 bolts with new ones (do them one at a time so you don't lose your setting).

Now for the fun stuff: explaining how it works. The injection timing is under automatic control, regardless of your manual setting UNLESS the automatic control reaches the limit of its travel (in which case it obviously cannot adjust it any further). Also the manual setting affects injection timing during starting, because the automatic systems aren't operating at that time.

If the computer wants 2 degrees BTDC, it will get 2 degrees BTDC, unless your manual setting doesn't allow that setting to be achieved.

Stock timing at warm idle is 0.4 degrees BTDC. Mine is set to 2 degrees BTDC - it's advanced far enough that the computer cannot retard the timing below 2 degrees BTDC at idle.

<HR></BLOCKQUOTE>

Brian P.,

Yeah, I knew all that stuff already. What about the ability to adjust/meddle with the advance charateristics with whatever is under that cap? The manual (or static) timing is okay as long as the car starts, within reason of course. My '97 Jetta TDI starts and runs fine, actually, great. I'm trying to get more mileage/range per tank of fuel. I'm trying to maximize fuel economy for highway runs. Maybe, if I canget a little more efficiency, I can get more range. So, what gives with that Timing Control Cover, as it is called in the Bentley Manual. (Bentley Manual for VW Jetta/Golf/VR6 &TDI, 1993 to early 1999. See page 23b-10, Figure 9, Item Number 21.)

Is there some sort of adjustability under the Timing Control Cover? I tend to think not since the performance "maps" would set the dynamic timing per the maps. This is after all, a closed-loop system that uses look-up tables, or maps to determine the injection timing.

Thanks,

Al K.


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Boundless
1997 Jetta TDi

The static timing adjustment adjusts the ECU baseline number as it relates to the injection timing. By rotating the pump around its axis you affect the starting timing and the corrected timing.

What you are looking to do is what I have done to both of my TDI's. I advanced both of my cars to the full advanced setting (rotate pump top towards engine) to get the best economy. The ECU reads the "Basic setting" and adjusts off of that.

DO NOT OPEN THE PUMP, get a vag com and VW Tool software and adjust the timing in the basic setting mode.

A3/B4 (Passat procedure)
1. loosen the 3 bolts on the front of your pump.
2. loosen the support bolt on injector line side of pump.
3. hook up vag com cable to diagnostics port.
4. start car and run the software.
5. select data block 0
6. select basic settings (removes ECU corrections)
7. rotate pump until block #2&9 are where you want them, NOTE: Do not adjust outside of the shaded graph in the Bentley Manual.
8. once the blocks #2 & 9 are wher you want them tighten the front bolt on the injection pump.
9. shut the car off and tighten the other 3 bolts.
10. loosen all 8 injector line fittings and retighten.

You will notice that this moves the powerband higher in the rev range of the motor. This adjustment makes a noticable difference and if you are chipped you will really notice the improvement!

DB

GoFaster and Drivbiwire, you don't seem to agree, do you?
According to GoFaster, advancing the timing only helps when starting the car, it has no effect when the engine is running (except if you put a chip, as far as I understand)
According to Drivbiwire, it does help when you search for lower fuel consumption, as an advanced timing enables better combustion.

So guys, who's right? Should I make this mod or not? (Presently I'm a bit under the mid-line of the grey area)
TIA!

[This message has been edited by Eric Maurier (edited March 07, 2001).]

I am 110% positive that advancing the timing will in fact modify the "corected" timing. Ask anyone that has had their timing adjusted and they will tell you that there is a change. Bkmetz had his adjusted and he noticed the change immediatly.

Like I said the "Basic settings" adjust the reference timing setting that the ECU bases it's corrections off of. When the engine is running it always assumes the "basic settings" timing to be correct and adjusts the injection parameters according to the fuel mapping software.

Keep in mind Retarding the timing will give you better low rpm power but lower mpgs and higher soot at highway rpms. Advanced timing will increase actual Horsepower but will also remove some of the low end "grunt" but you get an extra 3-5mpg by doing this.

The reason VW does not advance the engine from the factory is that it yields an increase in Nox due to the slightly higher cylinder pressures and temperatures. This is due to the longer burn times that are a result of advanced timing.

Keep in mind that the ECU has timing autority of 5 degrees retarded and 19 degrees advanced. Adjusting the basic settings will yield +/- 4 degrees on that scale approximately. Also you will not be able to read and change in TDC/BTDC on the diagnostic software since the ECU cannot determine the basic settings when in the normal operation mode.

DB

Sounds like GoFaster and Drivbiwire both agree! GoFaster said that, "it's advanced far enough that the computer cannot retard the timing below 2 degrees BTDC at idle." That's at idle. What happens beyond, I don't know.

I will add one thing though: Advancing the timing is not some magic potion for increased power and better fuel economy. I would assume that, at least for a chipped engine, the timing maps are already optimized near MBT (minimum for best torque) or MBE (minimum for best economy) depending on where on the load map the engine is operating. Countless studies have been done over the years on countless engines and the results have been the same: BSFC and BMEP plateau near the MBE and MBT points respectively, and going +/- a few degrees in either direction gives perhaps a 2-5% variance in BSFC and BMEP (not any significant difference you can feel by seat of the pants or by the MPG because that amount is practically statistically insignificant with the multitudes of variables (including cycle-to-cycle variations within the engine).

In fact, if you advance the timing beyond the MBE and MBT points, fuel consumption and power will suffer. It should be pointed out that OEMs will usually tune the timing maps somewhere between MBE and MBT (they're not necessarily the same), while tuners will aim to tune to MBE at light loads and MBT at higher loads. That's why chip tuners can justifiably claim to offer better mileage than the stock mapping, while increasing power. This claim is borne by real driving.

Also, although changing the timing from MBE and MBT will have small difference on power and economy (we're talking about a difference of 2-5% for +/- 2 degree adjustment here), timing has a HUGE effect on emissions, particularly NOx, but hey, nobody around here cares about that do they, since lightning produces them, too!

P.S.: DB,

Advancing timing will not result in longer burn times. In fact, it's the reverse; ignition delay will be shorter, and rate of heat release faster, and that's what causes the rapid pressure and temperature rise, hence louder combustion and more NOx.

I am of the opinion that if commencement of injection is set within the gray area, emissions are within epa specs.

I have to believe that the static timing is, within limits, exclusive of the dynamic timing, and vise-versa. The reason is, the lift sensor for the No. 3 cylinder and the crank position sensor. These sensors have to be used for dynamic timing measurement and adjustment. They detect the crank angle position and the actual injection timing (of the No. 3 injector.) and the ECU sends out command(s) to change or hold as necessary, per the look-up tables. If the dynamic timing were based off the static timing, then the system would essentially be an open-loop system with no need for the lift sensor and crank angle sensor.

Anybody have or know where to get detailed documentation on the fuel injection system?

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Boundless
1997 Jetta TDi

[This message has been edited by Boundless (edited March 07, 2001).]

When I said longer burn times I meant the available window for injection to occur as it relates to quantity (I should have been more clear). I whole heartedly agree that with higher pressures and compression temperatures that ignition delay will be reduced. I think this is where the higher pressure PD system will show it's true value. Higher injection pressures should yield smaller atomization and require lower temps/pressures for ignition to occur resulting in reduced ignition delay times of the fuel. Lower Nox and particlulates should fall into line as a result even with our higher sulphur fuels in NA.

DB

Skypup, what's your opinion about it? I know that there's a dynamic variation of the timing depending on load and rpm and other factors, but does the ECU do what's needed to get the timing it wants or do we really modify the injection timing when moving that injection sprocket?
Thanks!
(sorry, I am used to good old diesels like the Peugeot XUD9, where there is NO electronics at all when the engine is running)

Eric,
With a Spark ignition engine (SI), there are two ignition timings to be concerned with. The static and dynamic. The static is what we set, usually at idle, a few degrees BTDC. Then there is the dynamic, we'll use the old fashioned distributor w/flyweights. The weights fling out as the RPMs go up and advance the spark timing. The static timing can be set anywhere and the dynamic timing will still do what ever it is designed to do with respect to RPM of the distributor, regardless of the static timing, but the total advance is affected. I maintain the static & dynamic are not related the same with the TDI. The static timing, that is controlled by rotating the pump, or the pump sprocket, doesn't effect the dynamic timing. Once the engine is running, the ECU gets its info from the No. 3 cylinder lift sensor that tells when injection starts and the crank position sensor. Of course there is probably a limit of the range of dynamic control available to the ECU/pump, but as long as the static timing is set within these limits, the static & dynamic are probably independent. Even if the static isn't set within the limits, all that is probably happening then is constraining the intended range of injection timing control band.

What we really need is the control algorithm for the ECU & pump to understand our TDIs.

Anybody know how/where to get this info, probably from Bosch?

This gets me back to my original question: what is under the TIMING CONTROL COVER and is it adjustable? If so, how?

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Boundless
1997 Jetta TDi

[This message has been edited by Boundless (edited March 08, 2001).]

Adjusting the static timing DOES affect the "range" of the dynamic timing. The static range is measured in the Basic settings mode and has a defined range based on fuel temperature and engine coolant temperature. Basic settings controls two things, starting injection timing and Dynamic timing (range).

DB

What is under that cover is a small electric solenoid valve and a servo plunger which engages the timing cam plate inside the pump.

It's not adjustable. Don't even think about it!

Brian

Oooooohhhhh......

Well that takes care of that. Thanks for the reply. I guess there really ain't a lot a person can do to meddle with the economy of these TDIs without getting into chips & such. I really want to get my TDI to be as efficient as I can get it. Yeah I know getting twice the MPG as an equivalent gasser should be enough, but when I get 600+ miles per tank and average 45 MPG (several 50+ MPG, 55.4 MPG Max., roof rack w/four bikes bites.) overall, I just want to put a little effort into seeing how far it can go. I think driving from CT to southern FL on two tanks of fuel is great, even hammering so the MPGs were far from typical high highway values.

So, what do all these chip thingies like Upsolute do? They must do things like allow more fuel at lower RPM, earlier turbo, more & earlier injection advance, yada, yada, yada...

Diesels are inherently efficient. Other than scrupulous acceleration control,what can be done to get more MPGs & ultimately, range? Other than keeping the air filter clean, tire pressure up, maybe a fuel additive, what else is there to do to get more MPGs?

Thanks,

Al

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Boundless
1997 Jetta TDi

Time advancing on a TDI

Drivbiwire said:

I am 110% positive that advancing the timing will in fact modify the "corected" timing. Ask anyone that has had their timing adjusted and they will tell you that there is a change. Bkmetz had his adjusted and he noticed the change immediatly.

DB

Click to expand...

Doubtfull: slope, speed , wind, pedal will affect a lot more than a 2 to 3% timing advance.

Optimal basic setting is determined at factory after thousands of tests in lab conditions, where all other interferences remain steady (slope, speed, wind, tires, pedal, etc).

Moving from factory basic setting does not make sense to me. It probably will affect fuel yield negatively.

Oldbeaver.

Oldbeaver said:

Doubtfull: slope, speed , wind, pedal will affect a lot more than a 2 to 3% timing advance.

Optimal basic setting is determined at factory after thousands of tests in lab conditions, where all other interferences remain steady (slope, speed, wind, tires, pedal, etc).

Moving from factory basic setting does not make sense to me. It probably will affect fuel yield negatively.

Oldbeaver.

Click to expand...

Wow!! That's old stuff you dug up there.
And, actually, my MPGs are a bit better (yes, I have proof) with the timing advanced.

Holy10yearoldthread, Batman!

85_305 said:

Holy10yearoldthread, Batman!

Click to expand...

I love this one!

Oldbeaver said:

Doubtfull: slope, speed , wind, pedal will affect a lot more than a 2 to 3% timing advance.

Optimal basic setting is determined at factory after thousands of tests in lab conditions, where all other interferences remain steady (slope, speed, wind, tires, pedal, etc).

Moving from factory basic setting does not make sense to me. It probably will affect fuel yield negatively.

Oldbeaver.

Click to expand...

Factory timing is concerned with emissions over performance.

lol@ robin