PD Engines - The Problem of Setting Torsion Value

greengeeker said:

Negative. It still uses the crank to determine when to inject the fuel.

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See, that really bums me out because if it were Cam position, my thoughts would make sense for once.

Oh well. I guess I'll just have to accept this one. Sometimes it's better to hold my thoughts inside.

Don't hold back on your thoughts. I've learned by picking up gems from all of you as I go along. The guys on the ECU forums learn all of the time by picking up puzzle pieces from each other.

greengeeker said:

Negative. It still uses the crank to determine when to inject the fuel.

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Can you explain that statement? When I replaced my timing belt, I had the option to move my IP wherever I wanted it. Now it may not run if I moved it, but the only correlation between it and my crank, was the belt. Now the computer may base it's operation of the IP on where the crank is, but that is it. So my IP can be off a few degrees, as well as basically everything else in this operation, hence this whole conversation.

rpturbo said:

Can you explain that statement? When I replaced my timing belt, I had the option to move my IP wherever I wanted it. Now it may not run if I moved it, but the only correlation between it and my crank, was the belt. Now the computer may base it's operation of the IP on where the crank is, but that is it. So my IP can be off a few degrees, as well as basically everything else in this operation, hence this whole conversation.

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Different engine.This thread is about the PD fuel system engine, not your VE fuel system engine.

^^ what he said. Completely different fuel systems.

I did a speed-read through the posts. One request was to summarize. I'd like to do that, but I feel there are several conflicting statements, coming from who I consider reliable sources.

I do understand that the torsion value changes when the engine warms up. But the cam timing is directly affected mechanically and mechanically moving the cam sprocket does make remarkable differences in fuel economy. Changes as small as .5 can make 4mpg difference in fuel economy .

Normally, the torsion value seems to be 0.0 to -1.5 in most cars, but there are exceptions. We have seen fuel economy's in the 50's with cars set anywhere from +4.5 to -5.7. Something must account for the variation.

There are a large number of variables that can affect the timing. For example, one recently removed BRM crankshaft sprocket could be moved about 1 degree in either direction. Certainly, if all variables fell one direction or the other, torsion value will be skewed in that direction. I.E., if you moved the crank sprocket in a positive direction, it would require a negative torsion value to compensate and still get the same results.

I don't think using an idle-speed run to determine liter per hour (Block 15) is a useful number. If anything, running at a designated rpm at temperature through a flat course would be a better measure. I do think that measurement could be useful.

Although checking the setting before tear down MIGHT be useless, it would be somewhat valuable if the engine were performing reasonably well. Particularly if the measurement received is considerably out-of-line with what would be considered 'normal'. If the usual 0.0 or -1.5 variables don't work and the engine is running poorly, don't forget where the starting point was. My feeling would be that if an engine is running good at -5.7, you change cams or timing belt, etc., reset the torsion value to 0.0 and lose performance, start gravitating your torsion negative toward -5.7 until you find the 'sweet spot'.

The good thing... it's not that hard to fiddle with. Also, if you set the belt on the cam sprocket correctly and the 0.0 is somewhere in the middle of the adjustment, you can't reach a point that you would get interference contact with valve and pistons. It is somewhat 'idiot proof' to that point.

Well, when these car are assembled what are they set at, or how does the manufacture set each engine or not for best economy/ performance ?
What has been the happy average people are setting them too ?

Robby,

I have noticed several of the engines marked with the two numerals. I have no idea what the 3 digit numeral represents. The other, which is usually a decimal integer does appear to indicate something to do with the torsion value.

However, if any component has been changed; timing belt, crankshaft sprocket, front flange... I think any alteration to the timing belt circuit could alter the torsion value number.

I also, would like to know how the number is originally produced. Good luck with that one...

Hi everyone
After watching this thread for a few days I decided to register so that I could reply and post my findings
Firstly the torsion setting I have noticed on several sites, some people are regarding a negative value as a retarded setting and a positive value as a advanced setting, this is the opposite to what I am seeing, as I adjust the camshaft with the 18mm centre bolt in the direction of rotation (advancing the camshaft) this adjustment shows on vcds as a negative value and a positive value if I adjust in the opposite direction.
I assume vcds is taking a positive value ( +) as more than zero ( retarded ) and a negative value (-) as advanced timing .
I hope someone could clarify this ?
Secondly I have tried a few different torsion setting the first was -0.6 which I achieved 33.3mpg, I have now adjusted it to a +2.0 and I noticed that the injector smoothing values and the idle comsumption got better.
However like frank06 has said I don't think a setting based on idle values will result in a increase in mpg.
I will update my mpg with the + 2.0 setting shortly.
Seems like the torsion setting for max mpg is a little hit and miss. I wonder what volkswagen take is on all of this ????

I really think you have it backward, Manicmick. Nonetheless, whatever torsion number you get, it will be interesting to see a fuel economy improvement.

As for what VW, I think they would stonewall.

I must admit I was surprised by what I found on vcds but I adjusted again to double check and it was the same. I also spoke to a friend of mine who specialises in vw and Audi the way he decribed it was that if 0 was the setting a negative figure is before 0 so advanced timing and a positive figure after 0 so retarded timing.
With my setting at + 2.0 I did notice alittle smoke at startup which could also prove the assumption of retarded timing, as on the older vw diesel engine you had a cold start lever which advanced the timing for better start up and reduced smoke levels.
Like you said + or - values is irrelivent so long as you get what you want mpg/power.
On a side note vw went to the trouble of machining the camshaft hub with the ability to finely adjust the camtiming/ torsion setting so they must have seen better mpg/power/emissions for them to do so.
True tdc could be a found using a dti gauge but how would I find the true camshaft set point for this figure.

Franko6 said:

The good thing... it's not that hard to fiddle with. Also, if you set the belt on the cam sprocket correctly and the 0.0 is somewhere in the middle of the adjustment, you can't reach a point that you would get interference contact with valve and pistons. It is somewhat 'idiot proof' to that point.

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Good to know. LOL My engine, set up by Frank, is currently reading -1.5 at speed and temperature. I'm gonna leave it there and see what my mileage does. I'm waiting on a Malone tune presently. The car is not yet road ready but...It's really close.

... I'm not sure how the car sees the torsion value but if you rotate the camshaft in the direction of the rotation, you are advancing the timing. You are going "forward". If you go the other direction, you are "backing the cam up". the valves will open Later.

This torsion stuff is different for me. I'm used to setting cam timing with a degree wheel and a specific lift. Even though I"m setting 2 or 4 cams, it sure is nice being able to put a rod through the spark plug hole and place a dial indicator on top. LOL I make cool little tools for that.

Brother is still playing with his and I will report back when he finds his sweet spot. As an FYI-the torsion aslo matters on the new common rail engines as well.

It matters on a LOT of engines. I think we (TDI club in general) tend to overthing some really simple things.... this is one of them.

GM 4.3L, 5.0L, and 5.7L truck engines have the same thing, they call it "knock retard". Same deal: supposed to be at '0', and it can be WAY off and the engine will start and run, but it won't do either perfectly, and you'll never see a DTC or an MIL because of it. We get those in here constantly after some hack resealed the intake and had the distributor out and thought his mark & pray method was adequate, only to find out afterwards it wasn't... and you need a GM-specific scan tool/software to check and adjust it. Then afterwards, the engine starts easier, runs better, idles smoother. Sound familiar?

VAG gassers have this, too, but most of those nowadays have a variable intake cam(s) phaser, so they'll set a DTC very quickly if it is out... and often times it is out because of a chain issue, not any adjustment (as they do not have an adjustment like the PDs do).

According to VCDS, my torsion value reads 0.5 @ 903 RPM, and my belt cover has no hand written numbers. I've been averaging just over 40 mpg's with an 09A trans.

So just to summarize everything I've read in this thread: If I check my torsion value with VCDS and it is something other than +0.5, then I should mess with the cam pully to get it to about +0.5?

Is that about right?

(I love fiddling with stuff like this, so I sure hope I need to )

Mike,
Not quite.

It appears setting torsion (or manipulating it) could improve MPG. COULD...does not mean will.

It will take a bit of experimenting on your part, mostly because each engine is a little different due to manufacturing tolerances.

Let me make up some scenarios, similar to what I've read:
1) Some engines have a rough idle at +.5, but good mpg.
2) Some engines have a smooth idle at +.5, and terrible MPG.
3) Some engines have a smooth idle at any setting, and their best mpg at -1.5
4) Some engines idle rough at any setting, and get good mpg at 0.0

The point is that every engine is a little different.

Tony

I'm at -1.5 Stage II BEW and my mileage isn't very good, even when driving it normally Going to try it at 0 for a few tanks and see what happens.. Also notice it gets a real kick in the pants at 3k and pulls like crazy until 4500rpm or so.. I'd like a little more bottom end to be honest.

Well, I'm glad that the best torsion value seems to vary from car to car, because I just changed my torsion value to -3.4 while trying to hit -1.5, and the car ran incredibly smooth, on both -3.4 and -1.5 actually.

I need to run -1.5 for a few tanks and then try out -3 for a while.

If you run -3 you are getting very close to the point where pressure is still rising and the fuel solenoid opens. With no timing map changes you may be ok but with any additional advance over stock you will loose out. Having said that the NA maps seem to be more retarded than others so you may well be OK at -3. Theoretically going - robs the bottom and helps the top but it's not that noticeable on turbo motors.

It doesn't take a few tankfuls to figure out the best setting, if your driving pattern is consistent.
Mine seems to be at -.75, as the readout fluctuates between -1 and -0.5.

Mine is 2.5 avf engine.is good?

After my camed up install of my replacement engine (Franko6) I haven't touched my torsion value yet but it is reading -1.5 with an ocassional -2 before it warms up. I'm not very exact on my mileage but my first tank looks like 40.5 to 41.5mpg. I've done some breakin, higher RPM driving and such so more lead-footed than normal, plus my I had some old (11 month old fuel) in the tank at fill up.

I filled up last night so this next tank will be more accurate. Good or bad, it only takes me a week to go through a tank of fuel. I can usually tell where I am with mileage pretty quick. I monitor it closely, just because it is a good measure of performance and engine condition.

I am going to go to -.5 or the torsion after I get a few tanks through this thing. I have a flashzilla ordered from Malone tuning,perhaps he can give me a recommendation so...I will wait for him to give me suggestions. Maybe one day I'll become better at using the VAGCOM. Who knows ??

When Mark tuned my car I had the cam set at 0.0. Come to think of it, last time I had my cam retarded was before I got tuned, and I know it used to hate running retarded, which is why I was surprised it ran happily at -3.4 this morning.

Anyway, I am doing multiple tanks because while I am a consistent driver, there is enough variables that I can't control that I want to increase the signal to noise ratio.

torsion value is different with engine hot and cold?

@Tdi VW said:

torsion value is different with engine hot and cold?

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I drove around with my VAGCOM connected to the computer and it registered -2.0 then -1.5. After it warmed up a steady -1.5. My thinking is that I am in between actually 1.75ish so the VAG reads a small variance at it's limits and that's what I see.

Based on current performance, I need to advance the timing a bit. I have to admit that I am excited and am looking forward to the tweaking process.

Hot / cold.....the torsion value is mechanical and fixed. The only variance may be due to drag at the cam, cold / warm belt length and the difference in time it takes for the voltage to reach the trigger value at different temperature and speeds. For all intents and purposes it is fixed. I believe too much is being made of small timing changes. IMO the fact that the MFD reacts noticeably to small changes is a red herring.

One anecdotal observation I have made is that at WOT in 4th and 5th gear, when my clutch slips the engine revs up to about 3000 RPM now, when before with the timing at 0.0 it would rev to 2700 RPM then the clutch slipped.

The power band does seem to be a little more distributed throughout the RPM range.

Mako said:

Hot / cold.....the torsion value is mechanical and fixed. The only variance may be due to drag at the cam, cold / warm belt length and the difference in time it takes for the voltage to reach the trigger value at different temperature and speeds.

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I'm not sure the temperature would have much effect on the electrical side, but that is a good point on the belt stretching as it gets warm, causing a slight change.