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TDI Fuel Economy Discussions about increasing the fuel economy of your TDI engine. Non TDI related postings will be moved or removed.

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Old August 31st, 2017, 06:58   #1
James & Son
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Default Argument for tight BEW or BRM Injector setting

I posted this in the A5 thread and thought you guys may have may have not considered this. I was responding to a cam replacement( BRM or BEW) reduced mileage question.

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Worth checking injector clearance setting. If you use Franko6 method there are no special tools needed.
Way back now in 2009 I had my cam replaced under warranty. For some reason i checked them in 2012 and instead of the 1/4 turn I only had 1/8 turn. I am sure now that the mechanic didn't bother checking the injector clearance to the new cam.

I have always wondered if I didn't get better fuel mileage at 1/8 turn though? I wonder if on the fuel mileage thread if they have not tried it? The concern I would have is what grows faster the injector or the cam tower? From my experience it would seem you can run it slightly tighter than 1/4 and possibly as tight as 1/8. What would happen if the clearance closed up??????
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Old August 31st, 2017, 08:59   #2
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by increasing the clearance between the injector and cam you are effectively retarding the SOI timing. And the opposite is also true.

Which subsequently influences the accuracy of the fuel duration maps which are based on SOI timing to calibrate the rate of fuel delivery based the slope of the cam at the start of injection.

Which is also how torsion setting comes into play, regardless of what was speculated (or not) in that other mega-thread.
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Old August 31st, 2017, 20:25   #3
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Thanks for making the point on how it affects the fuel rate of delivery and therefore the accuracy of the fuel rate and duration ralative to rpm or distance over time( fuel map).

Now that you forced me to see the complete picture, it would seem more clearance would be more beneficial than less clearance if one wants maximum fuel rate( injection on steeper part of cam ramp).

Ok, wastn't sure, but I think now from what you said tightening the clearance would have little benefit for me at average rpms.

Has anybody tried retarded torsion and a 3/8 clearance for low rpm efficiency.

Would you like to comment on this possibility, KERMA
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Old September 6th, 2017, 18:13   #4
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So what's better, more or less clearance?
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Old September 8th, 2017, 10:34   #5
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Yes, I would like some opinions on that as well.

I think it is necessary for this thought experiment( unless someone has already tested the variables) to include the modification of adding or subtracting to the cam position sensor activation point without physically advancing or retarding the cam.

In other words does the ECM look at the crank and cam position sensor and adjust the injection point as well? In other words do not rotate the sprocket( which would affect cam lobe opening and closing as well as the injection lobe injection rate) but retain the physical cam timing and advance and retard the sensor or activation plate instead.

The ECM would be fooled into thinking you have changed torsion.

Now you would have the opportunity to advance the cam while fooling the ecm into thinking the torsion is the same, the advanced cam will allow better fuel atomization(increased injection rate caused by steeper position of injection ramp)

Ok, I just wrote this out and it looks like adding additional clearance to the injection rocker would do the same thing.
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Old September 8th, 2017, 10:44   #6
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also keep in mind
more clearance will reduce how far the plunger travels with each stroke, so fuel delivery is reduced by some amount

the cam sensor calibration can be adjusted in the tune if you really wanted to. In fact there are different calibrations for the different engines. BRM, BEW, BHW, etc. But it's not something that tuners typically know about or look at when doing their thing. It's just "not messed with" (or even known about necessarily).
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Old September 16th, 2017, 16:38   #7
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I am getting that our thread, "The Problem of Setting Torsion Value" is not received well by all. That is okay. In general, it benefits all.

Start of Injection (SOI) in the PD's is controlled by the solenoid, not the rocker or it's adjustment. Even if you loosen or tighten the injector rocker's adjustment, it's not going to change the timing of the injector lobe. The pilot pop is of some small consequence that is mechanically produced, but the main fueling is electronically controlled by a solenoid on the injector; the SOI and volume is controlled and optimized by the ECU firing the solenoid. Fueling is limited to the pressure and volume inside the injector, which would have some very minor gain if you screwed with the ball pin by 1/4 turn (roughly 7.2mm diameter x .010 distance, is an amount of .000356 gr.), and that is certainly worth risking a broken injector or rocker.

Since there is an interest for almost every PD owner to optimize fuel economy, using the VCDS /Engine module/block 15 liter per hour as a guide, certainly doesn't hurt. And regardless of any mapping or other program changes, the cam position is still going to have a strong affect on the final outcome of fuel efficiency and power. Adjust to your heart's content if you think moving the ball screws will make a difference. Give the ballscrews a 1/4 turn and see it it makes a difference in block 15. However, any improvement in economy is more likely found by setting cam position very carefully.

I wish you would use a more appropriate term than 'clearance'. Maybe 'reset' from bottomed out. Clearance infers a gap when instead, what you are doing is adjusting the maximum depth of stroke of the injector plunger while still allowing for heat expansion.

I can't calculate the expansion rate of the rocker, cam, ball pin, and ball screw, injector, cylinder head, and all the other variables to figure if you have left yourself enough free play from over-compressing the injector and straining the rocker. If insufficient clearances are allowed that makes a huge compressive hit on the cam bearings, and for what? Some assumed gain of 1/4 turn or .012"? Let's be sensible.

By the book, we have applied the 180 degree reverse turn from a bottomed out injector. The thread pitch of the ball screw is 1.25mm or one complete turn is about .049". So, 1/2 turn is roughly .025". That is a safety factor.

As for increasing fuel with the ball screw? Why risk damage for an infinitesimal amount of fuel?
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Last edited by Franko6; September 16th, 2017 at 17:13.
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Old September 16th, 2017, 17:51   #8
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Quote:
Originally Posted by Franko6 View Post
I am getting that our thread, "The Problem of Setting Torsion Value" is not received well by all. That is okay. In general, it benefits all.
I don't get that at all!

I just see another conversation on PD injectors.
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Old September 20th, 2017, 09:13   #9
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I think what the problem is, that some people want to marginalize the injector and quite honestly, under normal everyday driving, adjusting the injector until you are standing at the cliff's edge is not safe nor wise. All you are going to get is close to disaster without any perceptible advantage.

That is quite simply, my opinion on the matter.
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Old September 21st, 2017, 08:53   #10
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One thing we are forgetting is time. The average rate of injection is the time required for the plunger to travel a certain distance. Ramp angle ralative to rocker determines this. Is zero torsion the best rate of injection?

The question is does the ecm programing compensate for errors between cam and crank timing. From Franks torsion thread it seems not. The ecm assumes a fixed relationship between injector ramp angle, valve timing and crank top dead center. Is this correct or not? What about the cam position sensor? Am I right in saying it is only a rough backup if the crank sensor fails. I am assuming so and ignore it.

Using torsion to get more pop and increased atomizing one advances the cam. This increases the ramp angle but also advances the exhaust valve opening increasing exhaust valve temperature and follower temperature... not good.
So if you stay around zero torsion or slightly retarded this is good for valve and follower temperature but it also reduces the ramp angle and therefore the pop and atomizing.

How am I going to say this. Am I wrong that injector adjustment can not make up for this reduced ramp angle. Yes, i think i am wrong.

I got on this issue and Frank has proved I have a bad memory.

From my first post you can see I mistakenly after finding all my settings at 1/8 turn set the clearance at 1/4 turn and now i find out from Frank's post that it should be 180 degree turn. I did not realize this! Bad for relying on memory when i did that.

It looks like through no fault of mine that I ran the car with preload on the cam for at least 2-1/2 years before resetting to 1/4 turn and now I have run that incorrect setting for 4-1/2 years. Surprising I do not have wear on the ball? So that means also I am lucky I did not bottom out at maximum lift( thanks Frank for making that clear, my bad memory).

Anyways I am doing my timing belt this October and will be resetting my injection clearance to 1/2 rotation and setting timing to zero torsion.

Injection clearance has no effect on ramp angle and thus atomizing pressure( best rate of injection) is idealized around zero torsion.

Retarding torsion is probably good for breakin of a new set of cam and followers though in keeping the exhaust follower temperature lower.
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Old September 23rd, 2017, 10:55   #11
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Tell you what, James and Son... If you actually follow the logic of my method of setting, it works and works very regularly. There is no "one setting" for torsion value. It is characteristic of the engine. Remember, the torsion value is the degree of advance or retard of the CAM. So, mechanically, you are changing the opening and closing point of the cam, which will make significant fuel and power changes.

The injection will fire no matter if the plunger is bottomed out, or as one engine we saw, the customer had set the injectors so there was actual space between the ball pin and screw! It ran, but of course, with no power, but it would go down the road..

So, maximizing the last 180 degrees of rotation is very incremental and as I previously said, DANGEROUS! As we have seen the rockers broken in two and the valve covers smashed from the loose parts flying into the cover.

If you think it's a matter of some scientific experimentation, J & S, you go ahead, but for the average builder, DON'T DO IT.
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Old September 26th, 2017, 08:09   #12
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Ok, I checked and when i found my injectors set tight in 2012 I corrected them by using Franko6 method and did back it off 1/2 turn.

My fuel mileage is about 41.56 per us gal. or 17.5 kilometers per litre.

I will be doing my timing belt in the next few weeks

My timing will be set to zero as it is rate now and I will not change the injection ball adjustment.

I needed to do this post because i had considered the ball adjustment a possible variable back in 2012 when I had made a number of other changes, such as new tires, etc that had affected my fuel mileage. I have checked all the causes of poor mileage, maf , vac, boost leaks, etc. etc. and varied torsion and my tires are now well worn in but the mileage did not come back completely.

I have already stated( after considering others information) in my above post that changing the ball setting will have no affect on the atomizing pressure. This is because the ball setting does not affect ramp angle or the location of the roller on the ramp when the ECM initiates inject fuel and only changing the torsion will affect this. It only makes sense at low rpm(1700 to 2200) in high gear for max. fuel mileage you want maximum atomizing or fuel pressure. A (slight plus or minus) zero torsion is the ideal ramp angle and valve timing and resulting turboboost for the stock ECM injection map. I appreciate Franks thread in this regard but advancing torsion and thus atominzing pressure also increases valve temperature and you then need a thicker oil for the brm exhaust follower. I was hoping the ball adjust would avoid this.

So this post (edit:change post to thread) is now officially redundant as having a tight ball setting did not and will not affect fuel injection presure.

Last edited by James & Son; September 26th, 2017 at 14:32.
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Old August 28th, 2018, 14:16   #13
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I came across this thread while looking for information about what effect PD injector clearance adjustment has.

In my case, I wanted to mechanically de-tune the engine a bit.

Call it paranoia, but after stripping my timing belt during a full throttle merge onto the highway, I've been worrying about what effect a stage 4 tune has on timing belt strain. I'm sure injecting more fuel must put more strain on the timing belt, since that's what ultimately provides the force to operate the injectors.

I'm not saying there's anything wrong with the tune. I know others run much more power and I haven't seen reports of stripping timing belts, so this may not be as much of an issue in the real world as it is in my head. Also it was a 7 year old timing belt. So to be clear, I'm not blaming the tuner at all.

That being said, if I was doing my full throttle merge onto the highway with stock power levels, would there have been sufficient stress on the timing belt to strip teeth? Hmmmm... Maybe not. It takes less force to inject less fuel in a given amount of time.

So anyway, to avoid such disasters, I figured I would back my injector rocker adjusters off by 270 degrees instead of 180 degrees. This means the plunger is being pressed down by 0.3125mm or 0.012" less. I don't know what the diameter of the plunger is, so I don't know what this translates to in fuel volume. I think I've reduced the amount of fuel that the system can potentially inject.

My seat-of-the-pants dyno suggests a little less power at the top end, if I really wind it out. Low and mid range power remains about the same as it was with the injectors backed off 180 degrees, so not much effect there. Just a slight loss of top end.

I've also noticed I can't make any visible smoke. Before I could definitely leave a haze behind me at full throttle. I mean, it was VERY obvious. Now, I can't really tell if there's any smoke. If there is, it's A LOT less.

I've got my torsion value adjusted to -0.5.

It would seem like I have successfully de-tuned the engine a bit, which I hope will improve long term reliability, especially when it comes to the timing belt. (I'll be changing that every 5 years or 120,000km at most).
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Old August 28th, 2018, 19:15   #14
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Quote:
Originally Posted by Mike_04GolfTDI View Post
I came across this thread while looking for information about what effect PD injector clearance adjustment has.

In my case, I wanted to mechanically de-tune the engine a bit.

Call it paranoia, but after stripping my timing belt during a full throttle merge onto the highway, I've been worrying about what effect a stage 4 tune has on timing belt strain. I'm sure injecting more fuel must put more strain on the timing belt, since that's what ultimately provides the force to operate the injectors...
Sure, the modifications are likely adding extra stress, but PDs in general seem to be hard on belts. I've seen more than a couple go right at the 80k interval. The Dayco timing belt is sturdier and I would trust it to go longer than, say, a Gates timing belt, but seeing the history I have with PD belt longevity, I'd still stick to 80k intervals just to be safe.

It would be interesting to mess around with injector lash and torsion values, also making note of any differences it makes in the beginning of injection period viewed in measured value block 23 (it's a measurement in MICROseconds of when the solenoid is detected as being fully closed as noted by a change in the current draw of the solenoid vs. when the computer expects it to close). I've been wondering if torsion value in particular would have an effect on that number.

I've been able to spot patterns of bad fuel pumps and clogged filters with those readings. Less pressure means it takes less time for the solenoids to close as they're not fighting as much pressure to fully close. Bad injector seals could also play a role in affecting those numbers.

Just another thing to play with and see if a pattern could be discerned to further dial in a PD engine I suppose. But it's tricky when so many other things can affect that reading. Would be more about getting a baseline of what your car normally does and what is the trend when you make a cam timing or injector lash adjustment rather than aiming for a specific range of values.
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Old August 29th, 2018, 08:07   #15
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I had a look at my values in block 23 and three of the injectors are hovering around 20 microseconds, but one is around 40 microseconds. (values fluctuate up and down by perhaps 5 microseconds)

I have noticed that one injector sounds a bit different than the others at idle. Above idle speed you can't tell, and the engine runs very well. (I rebuilt it a month ago so it should!) I guess I shouldn't worry about it. Maybe if I feel like blowing money some day I'll get the injectors professionally rebuilt.
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