PD Engines - The Problem of Setting Torsion Value

whitedog said:

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.

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Thanks ill see at warm engine

Suggestion;
If anyone has access to a rolling road, maybe they could do runs with various torsion values (e.g. 0,-1,-2,-3,+1,+2,+3) and post the resulting plots so we could see the effect on power/torque.
I realize this would be specific to that car, as noted throughout this thread, but I think it would be interesting to see the effects and it might provide pointers to help assess other vehicles' sweet spots.

I'm sure the driving pattern changes results as well being some will rev the engines high, some drive automatics, some drive around town and some are on the interstate for hours.

Has anyone figured out wich direction would be better for local, highway, low end or high end?

Before I change the timing belt I was running:
Injection Start Injection Duration Torsion Value Injection Quantity Injection Quantity Injection Quantity Injection Quantity
(specified) (specified) TIME Deviation Cyl. 1 Deviation Cyl. 2 Deviation Cyl. 3 Deviation Cyl. 4
°BTDC °KW °KW STAMP mg/str mg/str mg/str mg/str
4 6.6 0 0.47 -0.07 0.09 0.07 -0.09
4 6.6 0 0.94 -0.05 0.09 0.05 -0.09
4 6.1 0 1.42 -0.02 0.09 0.02 -0.12
4 6.1 0 1.94 -0.07 0.12 0.05 -0.09
4 6.6 0 2.44 -0.05 0.12 0.02 -0.09
4 6.1 0 2.94 -0.07 0.09 0.05 -0.09

Now I'm running 6 BTDC
Don't know if this will help or hurt me. I'm driving +400 miles to NY to two weeks and would like to get it to what we think could be better.

Normally it's best where the manufacturer decided. They spend a lot and use equipment and resources we don't have to find this point.
Advance cam for low end and retard for top end IRO valve timing. At the same time you will be moving the peak injection pressure window froward and backwards. Too much in either direction and you will loose pressure at the start of injection or the end of injection.
The window isn't very big.

Mako said:

Normally it's best where the manufacturer decided. They spend a lot and use equipment and resources we don't have to find this point.
Advance cam for low end and retard for top end IRO valve timing. At the same time you will be moving the peak injection pressure window froward and backwards. Too much in either direction and you will loose pressure at the start of injection or the end of injection.
The window isn't very big.

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It seems to me that the point would be slightly different depending on if you have a heavy foot or a light foot. If you have a light foot, you could adjust it to take advantage of one end of that window but if you have a heavy foot, you can take advantage of a different part of that window. I would like to understand which is which.

I am under the assumption that a torsion value above zero = more torque.. Below zero is less torque off the bottom end but more pull on the top end.

My car is currently at -1.5 (Haven't touched it) and it definitely doesn't make the torque my old ALH did, but pulls REALLY hard from 3-4k... mileage isn't the best either.. After I do my TB in a few thousand km's, I am going for a above 0 value and see how thinks turn out.

0.0 degrees

My car would not start when set at +0.5, intermittant problem but some times it would be 12-20 tries to start. Reset the torsion to 0.0 and it starts fist time right away. I have a malone tune 1.5 and get some smoke on hard take-offs but it runs great!

jmoore, on a standard tune that small change would not cause or solve a hard start problem. If the Malone Tune has some very non standard start of injection while cranking it may place the SOI in the wrong place but I doubt it. I'm guessing you have another problem like an intermittent cam sensor going out?

jmoore said:

My car would not start when set at +0.5, intermittant problem but some times it would be 12-20 tries to start. Reset the torsion to 0.0 and it starts fist time right away. I have a malone tune 1.5 and get some smoke on hard take-offs but it runs great!

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A small change like that should not change the way the engine starts. I went from +1.5 down to 0 - 0.5 and the only thing I noticed was an increase in fuel economy. I bet you have something else going on, like a failed in-tank lift pump.

--Nate

I think I know what's going on with the reported fuel consumption with negative torsion...it really is using less fuel but only at idle and just off idle......just need to do some checking!

Some have reported a 3 mpg or so increase. Idle and just off idle use very little fuel anyway and account for a small percentage of the usage of the vehicle. I wouldn't think the savings there alone would account for such an increase as 3 mpg.

Torsion, vibration and MPG display

So a few years ago I reset an adaptation in a guys BRM so that the MPG display would read more accurately. All has been good.

This weekend, I changed the TB on this car. Well, the driver has always noticed a shake at idle. Before the TB, I checked torsion and it was at -2.5. After I was done, I set it to 0.0 and the vibration is gone.

But the MPG display is apparently off. They haven't ran enough fuel to know, but on a drive that they do alot, the display was consistently at 45 MPG. Today it was at 41.

So, hopefully the display is just inaccurate now. They will run a few tanks and if the displayed and pen-and-paper numbers are off, we can change that adaption again.

I don't know if all of this has been mentioned here but it is now.

I've had a few experiences with the BHW engines that almost refuse to start when really cold (-5F) with negative torsion values.. I had one particular Passat come in on a really cold week and I had to advance the cam from -1.5 up to +1.5-+2.0 for it to start on the 1st or 2nd try, and his mileage went down significantly.. I think he dealt with it until it got warmer and put the torsion back to -1.5 to get his mpg's back..

I sent some logs to Malone a while back. I did not take them properly of course but he could tell a couple of things. My timing was running -4.4 or so at higher RPM. At start up and idle after the engine warmed up it ran between -1.5 and -2.0 depending. Usually on -1.5. He suggested I set to (0.0) and see what happens. My first try moving the time was (+0.5) I ain't playin around for .5 degrees. We'll see what the mileage and stuff looks like before I move it again. I did not drive it yet, I have some JB Weld on the vacuum fitting off the pump, it's loose like most are. I'm having some problems getting the car to accelerate off idle. This is just a precaution.

I am glad you are posting this! Please keep us informed. My belt is coming up soon.

The car started a little more energetically since I moved the timing to +.5. More Perky at start up too. Seems happy. I noticed it pulls a little harder off idle and low RPM. That might be me noticing improvment with the vaccum issues. It is definitely FUN to drive again so something has changed . My wife even noticed the difference in performance. I'm likin it !!

I'm gonna try to do a few logs tomorrow and send them off. I had some injection quantity deviation that I did not like. I don't know crap about what it should be but 2 cylinders deviated more than the other 2. The deviation was more than 1. I don't know if that is OK or not.

I have another set of injectors off my old engine. That might be of help if I need to get something looked at and ready to install.

SK, I'm out on a limb here but....a PD (or CR) can (never should) be fitted with odd nozzles for instance and it will idle smoothly. The ECU measures the acceleration after each injection stroke and trims the fuel quantity to that needed for a smooth idle on each injector. Your deviation may be the ECU compensating for cylinder,valve gear, nozzle, plunger, cam and temperature variations and is a normal condition.

The VE do the same. That's what the idle smoothing function is: less fuel to the stronger injector (determined by less time until the next injector event), more fuel to weaker (more time until the next injection),
Provided the difference is small (2.2 milligram?) they are considered to be balanced enough

I'll have to look at the measurement scale. Thanks for the good information. I won't get to look at this for a fewdays but I'll post back on my findings.

There are a lot of posts in this thread where folks were going to adjust their torsion values and post back changes in MPG ... But no one bothered to post those findings...
.
Care to post now ?
.

What I'm after is what torsion value should I shoot for on my '05 PD BEW Golf Automatic - only getting about 26 mpg after TB change. Current reading is 0.5 .. Before TB change was getting around 32 mpg around town A/C always on.

Spike Strip said:

There are a lot of posts in this thread where folks were going to adjust their torsion values and post back changes in MPG ... But no one bothered to post those findings......................

Click to expand...

typical forum behavior, unfortunately.
Try posts 1, 2 and 7.
Post #1 gives the actual how-to

I found the sweet spot on mine by using my daily commute and MFD mpg trip values. I could tell a difference. On my TB cover, the factory number is +0.5. I settled on +0.75 as giving the best combination of mpg and drive ability. I say 0.75 because I just happened on an adjustment where torsion will vacillate between 0.5 and 1.0. I picked up about 2.0mpg vs torsion at 0.0- IMO.

Thanks for the replies, guys ... Since I just installed and used the VCDS software today, for the first time, I'm still learning the lingo... MFD ?

And unfortunately, the sticker on my TB cover is bleached out so I can't really read the writing... Might be 0.5 ? But there's a 2.2 above it?

I'll re-read posts 1, 2, 7 ...

MFD Multi function display

Ah, thanks Light... I knew that VCDS manual I downloaded should be good for something

Just don't loose sight of the fact that retarding the value will show an instant MPG improvement on the MFD. None more so than at idle where a zero torsion value may show 700ml/hour at idle and 1 degree retard may show 500ml/hour at idle. Idle is where most will see the numbers 'jump out' at them.

I think that Frank06 hit the nail on the head with the 1st post in this thread. Not all PD's will have the same optimum setting. I checked my torsion value & found it at -1.5. I reset it to 0 but the car was very difficult to start (very, very difficult). I set it back to -.5 and the car started normal so that is where I left it.

I was 104* here yesterday, and since I don't have any shade in my driveway, I opted to stay in the AC'd house... Will try to brave the elements today.

Can anybody make out what is on the TB Cover sticker ?

Obviously a bit faded ...

I just set the torsion to -2.0 and it seems to be running well...

My lablel is more legible but just as cryptic...but my torsion is at -.5