Adjusted my injection timing

My car has really been stinking like a diesel lately and after I had checked it at the Salt Lake Get together I figured what the heck it's time to adjust the timing. After I test drove it after the adjustment the diesel smell was reduced drasticly. I think once I get it out on the highway this will help get rid of the soot in the tail pipe.

I have noticed that my power is a little sluggish from a start and the fuel economy has dropped a bit. When I checked the timing at the GTG it was retarded and close to the limit of the adjustment scale. I checked it this morning and it was exactly where it was 10,000 mile ago. I have 53,000 miles and the belt is going to be done soon. I figured I could adjust it to the other end of the spectrum to see how much better it performs. This way I am limiting the factors that are being changed and have hard numbers on how much of a difference the timing will make.

I have been getting around 42 mpg while driving at 75-80 mph with the cruise set and AC running.

at the start of the adjustment the timing was 33 and 109 on the temp. at the end of the adjustment I had 63 and 130 on the temp. If you look at the graph in the bentley manual as the temperature of the fuel rises the timing index number drops off. In the center of the chart is a "C" scale I believe that this is where VW wants the timing set for emissions purposes. Where I now have mine set it is above the "C" scale. This is still within prescribed limits per the manual this will just advance my timing a bit and hopefully improve my power and economy at higher speeds.

I will let you know how well it works I'm getting ready to drive back to Dayton from Chicago the total distance is 262 miles of straight flat highway. I will top-off and vent the tank and top it off again when I get to Dayton. This will be a good indicator of how much affect the timing has.

DB

This is something I have wanted to do. I will look for the data you collect!

Can you tell what the difference in degrees these two data points correspond to?

I saw where someone had posted his timing at idle in the common way. (ie 2 degrees BTDC). Does your OBD-II connection not do this? (I ask this because I am quite close to ordering one and thought I would be able to read it this way. I also want to advance my timing if it needs it. I will be changing my belt soon and wanted to read it before and after to make sure it is not retarded by the dealer. Also wanted to make this adjustment possible by myself and did not know another way to do it.)



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99.5 Jetta GLS Silver Arrow
Tuningbox installed! WOW!

Question.... With this scan tool, can you change the timing electronically? Say by inputting a new value at some part of the program?
Alan.....


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99 Jetta TDI (A4)

From all that I know about this tool, which is not much, no. I have been researching this for a while and if I had found out you could adjust the timing via the tool, I would have bought one before now.

I intend to get one this week.

Here is the scoop:

262.2 miles fuel stop to fuel stop all highway. I topped off the tank using the vent trick I could not have put in another drop. I even nudged the car to make sure there was no air stuck in the tank.

My top speed was 90 mph (I drove like a maniac) kept the speed at 80 for awhile and then set the cruise at 85 for awhile. I had a lot of construction along the way as well and the AC was on full blast the entire time.

Here are the numbers: 262.2 miles used 5.760 gallons = 45.52 MPG using the vent trick and filling the car back to overflowing!!!!!

I usually drive at 75 but to make sure I really had an improvement I wanted to do everything possible to use more fuel. The timing made a huge difference if you ask me. I will check it on the way home and drive normal and really try to save fuel.

I have to say if my car get's this kind of mileage driving this fast I can only imagine how well it will do when I slow it down. The last time I drove this fast I recorded 38 mpg.

DB

Jaydhall, this is my opinion but because of my driving habits (fast) the timing for my purposes is bset set to the advanced side of the curve. If you need power for pulling at low speed I believe you want to retard the timing.

The numbers I wrote about reflect two things. The first number is the timing index and the second is the fuel temperature.

The timing is set using two types of points Basic settings and the normal settings. Basic settings are what you use to adjust the injection pump. This removes the ECU corections and allows you to see where in the adjustable range of the pump the timing is set. The indext number for conversation sake is between the number of 0-100 I saw a number of 255? this meant I had adjusted the timing off scale.

The timing is set by looking at the fuel temperature indicated in block window 9 on the vag software and comparing it to the timing index number in block 2. You then compare the two numbers to see where they fall on the graph. The graph has a "C" line through the middle. This I suspect will give you the best all around drivability and economy. You can vary your adjustments on either side of the line and this will retard or advance your timing based on your performance needs.

If you think about it it kind of makes sense. As the fuel is warmed in the system the combustability of the fuel increases with temperature so as the temperature increases the ECU retards the timing slightly to keep the fuel burn rate the same as when it was set.

DB

I have ordered a vag-com from Uwe. I will be doing this measurement pretty soon. It will be interesting to see where mine is.

How did you know from the graph that the higher number was advancing the timing? I did not see anything in my bently that said so. Also, in mine, It says to advance the timing by moving the hub to the left (counter clockwise). To retard timing move hub to the right. (counter-clockwise!) Does your book give a bit of a better explaination?

Yes, I repeat, no.

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99.5 Jetta GLS Silver Arrow
Tuningbox installed! WOW!

The TDI I am adjusting is my A3. On the A3 you loosen the three bolts that secure the pump to the mounting bracket, start the engine and rotate the pump until the timing is where you want it. On the B4 or post 99.5 as yours is you have to adjust the pulley itself. I saw Mickey adjust his and it takes some patience and multiple tries. The graph is listed under the Diesel injection system section.

On your engine the range of adjustment is very very small. I have to look at my wifes 2K TDI and see if there is an easier way to adjust the timing. I have had no reason to really get into her engine since it has less than 5000 miles on it.

As far as the fuel temperature, if you look at the lower portion of the graph you see the temperature scale. If you follow the timing index up the left side you can see how fuel temperature affects the injection timing. Also when you watch the engine warm up with the computer hooked up you can see the timing index number drop off as the temperature rises.

The adapter that UWE sells has worked great. With two TDI's in my family it will, actually it has payed for itself. You will have to get the VW-Tool software I believe this will do everything you need until UWE get's his completed.

Send me an email.
DB

[This message has been edited by Drivbiwire (edited July 31, 2000).]

jdhall.
I adjusted the timing on my 2000 NB.
From what I recall, you're moving the pump shaft, which I guess is what you're calling the hub, COUNTER CLOCKWISE with respect to the pully. The pully normally rotates clockwise, so that makes sense. I got the directions mixed up when I read Bentley. Also it will spring if you don't watch it and could get your timing all messed like mine and I had to guess. Maybe you could make some marks. Very small movements do a lot, though.

BigAl: No, you can't. The ECU's "plus or minus" decisions are based on sensor imputs, and cannot be changed via software. You must mechanically change the pump timing (and therefore the position of the timing "range" accessible to the ECU) or alter the sensor signals in some way so as to provide the ECU with faulty data on which to base its decisions.

-mickey

I got my vag-com today. I checked my timing with it. 45 at 171 degrees fuel temp. I read what you said about the fuel temp going up and the timing being retarded to compensate. One thing that does not make sense to me is that when I revved my engine the number went to 23 at 171 degrees fuel temp. Is a diesel not going to be the same as a gasser in the sense that when the engine is revving faster, the timing must advance to allow more time for the fuel to burn due to the fact that there is less time to burn the fuel? I am confused here! Someone help me!

jaydhall:

My injection pump's timing did the same thing - going from 62 (2* BTDC) to zero and after TDC during moderate to heavy acceleration. After the car reached cruising speed, the timing went back up to where it began.

In other words, during acceleration, the timing is backed off until the TPS senses less pedal pressure.

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2000 Jetta GLS 5-speed: Silver & Gray / Luxury & CWP, Monsoon & CD

Turbo steve,

I really do not understand! Is there some reading material I might get to enlighten me? Whew, I am confused!

Thought I understood autos. Gassers sure advance when engine speeds up, right?

Hmmm.. that is mechanical advance right? Vaccum advance would only be advanced under light load... Hmmm... I MUST find out what is up!

Oh, and how did you know it was 2 deg BTDC?

[This message has been edited by jaydhall (edited August 03, 2000).]

Jay:

RB Publishers' Manual on the 2000 TDI Jetta shows a graph or chart with numerical values for injection timing. The "62" was in the middle or slightly higher in the main stream on a line that approximated 2* BTDC.

I too was surprised that injection timing decreases during acceleration. About 4 or 5 other witness confirmed this enigma on a couple of occasions.

I can envisage a good Tuning Box magnifying the output signal going to the injection pump in order to help compensate for this retrogression of timing.

Turbo Steve, I have the bentley. I see the graph on page 23-16. I do not see any mention of BTDC. Am I missing something? Or are you just assuming this? Thanks for the info!

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99.5 Jetta GLS Silver Arrow
Tuningbox installed! WOW!

All, this is a graph from the Bosch Overview of Diesel fuel injection that confirms Jay's idea that timing will advance as engine speed advances.

The timing will advance little or none with increasing engine speed alone. It's the combination of RPMs and LOAD that advances the timing. The same thing was true of old-fashioned gas engine cars with vacuum advanced distributors, and it's true today with electronically controlled spark timing.

I would estimate that the gray shaded range in the Bentley manual covers about 2 degrees from top to bottom. But any of these VAG-compatible diagnostic programs should also be capable of reporting the actual dynamic timing in degrees. You can see for yourself what's really going on.

-mickey