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Author Topic: BOSCH VE LDA tuning  (Read 2140 times)

December 05, 2021, 09:36:10 pm

scrounger

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BOSCH VE LDA tuning
« on: December 05, 2021, 09:36:10 pm »
I have looked through some of the folders here and have not seen the LDA discussed in depth. With the VE pumps moving into the past on new engines. I thought it might make a worthy thread or at least one for discussion.

I found a Peugeot 306 forum had an interesting article.
Peugeot 306 thread

Like many articles that I have looked for, pictures and even the articles sometimes disappear and no longer exist.

I put a copy of it here on my server. Peugot 306 Bosch LDA adjustment and modification thread with repaired links.

Yeah, could just turn the fuel screw in but then you maybe using more fuel  than needed for just cruising around. The LDA's job is to put more fuel in under boost and still allow for more economical cruising.

Am interested in hearing your thoughts?
« Last Edit: December 06, 2021, 01:11:30 pm by scrounger »


M2 Jetta TD.  Northern Missouri

Reply #1December 06, 2021, 07:00:12 pm

libbydiesel

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Re: BOSCH VE LDA tuning
« Reply #1 on: December 06, 2021, 07:00:12 pm »
You ruin the boost pin when you grind it.  The premise of that initial post is flawed and demonstrates a misunderstanding of how to properly tune an injection pump.  IMO, following its advice is a mistake with the result being a less tunable pump. 

Reply #2December 07, 2021, 02:32:00 pm

scrounger

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Re: BOSCH VE LDA tuning
« Reply #2 on: December 07, 2021, 02:32:00 pm »
I have read a lot of posts on this forum and had not found much info on the function of the LDA. Libby please share what you understand, I am sure that you have more constructive information on the subject besides saying that grinding a pin may be bad. Throw me a bone, man.

Saw on a dodge cummings forum where they had a picture and labeled the stop in the top of the LDA  pressure chamber as a "smoke pin". Say what!!  I  can imagine that turning that screw in would enrichen the low speed. But why bypass this circuit to some extent

What I would like is to have the most economy as possible and more power than stock. Economy and performance are opposed from one another. But having a turbo means that we can control the footfeed and thus the boost. which in stock configuration is a 31% in power over the non turbo motor.  This car is my weekly or bi-monthly driver. I don't do any real test drives but rather make a small change and then wait till the next time that I drive it. Might take a month. By no means am looking for a super car, mine has a 9psi boost. Seems like most on this forum have moderate smoke and 30mpg all the time. I want good drivability and good economy

As far as grinding on a part, I can imagine having a case hardened part that once ground might have a soft center. I don't have plans to take my working pin and hogging it out.  Am going to play around with what I have.

When I first removed the LDA sliding pin after a few hundred thousand miles The wear from the contacting pin did not extend down nor up very much. The wear line was over the center half of the cone. Not the full range of motion of the sliding pin. I did rotate the pin around to other side which is much richer at all levels of boost. My mileage decreased as much as mid range power came up.  Nextly I rotated the diaphragm around back closer to where it was originally and found that the car was much doggier again.

Then started doing research on the purpose of the LDA and came across this peugeot article. My first step was to adjust the stop pin out 3 mm. I would be surprised if moving the cone 3mm up is going to move the contact pin out .75mm.giving a net position of in by .75mm or net richer. Then took out the 3mm thick nylon washer under the diaphragm and on top of the preload spring seat. allowing the pin to push down further with boost.  Am thinking that I should get some machinists dye to mark the sliding pin and better evaluate the full range. I want to adjust the preload to just barely get full travel at 8-9psi

Still saving my beans on an egt and sensor.

Although I have owned this car for about 11 years for the first 5 years I used it on the road about 500 miles a week and was I working full time so since it was running, I left it alone.  For the next few years I just didn't drive it much and only did the repairs that were keeping from being road worthy.  Brakes, parking brakes shift linkage. Was just this summer when I was doing a repair on the exhaust that I decided that if it was going to stay in my stable it needed to be better. The only gauges were a speedometer fuel gauge and oil light.

Hope that you guys can weigh in on with some constructive comments.
Thanks
 

M2 Jetta TD.  Northern Missouri

Reply #3December 07, 2021, 10:42:28 pm

ORCoaster

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Re: BOSCH VE LDA tuning
« Reply #3 on: December 07, 2021, 10:42:28 pm »
Well, Scrounger, I am with you on a balance of economy with a bit more than stock power.  But with the addition of a turbo to my 1.6 NA, I have really yet to find that sweet spot.  Mine makes too much black smoke and my MPG is only around 27.  Which is killing me!  I had a 2 door Rabbit that I ran for mileage to and from Portland every weekend and got right at 48.  Even on WVO.

So I read that link you posted and gleaned a few ideas on how the LDA works.  I am short on playtime with the VW right now but I may try a few things that are easy to do and undo and see where I go with power and mileage.  As you said, we don't drive it much so it takes a while to use enough fuel to get a good guess on MPG. 

I read somewhere that you can grease up the pin with Vasoline and the pin will travel on it and give you an idea of the travel you are getting.  I am not sure that the diesel will just wash it all off.  I am going to try it and see.  I have twisted the pin around all over the place trying to get it to smoke less and not die when I am first playing the clutch.  I have the main fuel screw adjusted as best I can, any less and it stalls and bogs down on me on the slightest hills at lower RPMs.  If I put more pressure on the diaphragm with the spring I think that will help, I am over-fuelling at a low boost. 

I can see where the Dodge guys may get the idea that the smoke screw is that one on the top of the LDA.  The forums are full of misinformation and well, they are Dodge guys in the first place.  Just saying. 

The quest continues.

Reply #4December 08, 2021, 05:12:51 pm

libbydiesel

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Re: BOSCH VE LDA tuning
« Reply #4 on: December 08, 2021, 05:12:51 pm »
Words are a PITA sometimes... and I have written all of this multiple times before on this forum.

The boost pin profile is matched to the boost spring rate.  As a bit of a thought exercise, think of the boost:fuel as three ranges that the engine will progress through: off boost, mid-boost, and max boost or for simplicity, low, mid, high.  Adjusting the rotation of the cone either brings the low or high boost fuel closer to the mid or farther away.  There is also the adjustment of the initial spring pressure which makes the fueling increase happen sooner/later and the cone stop at the top which limits the overall fueling increase.  On top of all of those is the max fuel setting which moves the entire max fuel map toward either more or less fuel. 

If you want that sweet balance between economy and power, then adjust that cone rotation, spring pressure, and upper stop so that you have a similar amount of smoke across the range of boost or maybe a bit more smoke at off/low boost (to help spool the turbo more quickly) and then adjust all of it up/down using the max fuel screw.

The settings that are built into the pump give the whole range of adjustments.  On the other hand, grinding the cone just ruins a key aspect of the overall adjustability.  The premise of that linked info IMO is just plain wrong.  It is the result of someone looking solely at the cone profile and ignoring all of the other adjustments and then trying to grind the cone to make adjustments that should be done elsewhere.       

Reply #5December 08, 2021, 08:04:25 pm

ORCoaster

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Re: BOSCH VE LDA tuning
« Reply #5 on: December 08, 2021, 08:04:25 pm »
I agree with Libby,  leave the Bosch-designed components alone and adjust within the parameters of the design.   In my experiences with these pumps, there are changes that happen very quickly.  Screws need only move 1/8 or so of a turn and performance is way different.  Or at least different enough that you can see and feel it happening.


Reply #6December 08, 2021, 08:23:43 pm

scrounger

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Re: BOSCH VE LDA tuning
« Reply #6 on: December 08, 2021, 08:23:43 pm »
I saw  this Gif video on a Polish ebay seller.

It showed a LDA in action. With much in Polish I  got some of it translated.


I added in some labels and took off the animation for clarity.
Here it is with partial foot feed and no boost.

Notice that the foot feed and fuel being delivered are in proportion although there are  no quantities are defined.

As the boost starts to come up. The pressure pushes the pin down against the spring and the Boost pin goes down the follower pin can slide in more. The follower pin is connected to the main fuel system with a lever.

There is an increase in fuel being delivered compared to the foot feed.

Here it is with the LDA fully engaged at the high boost level.

Definitely more fuel as the cone is now touching the follower pin at the narrowest part.

This is a hard part to analyze with springs pushing an unknown quantity Maybe smoke is the best that one can do for analysis.

I think pin travel might best be monitored with a pressure gauge and small pump. Put 5 psi or ten and then look at the travel of the boost pin against the follower pin.  That still doesn't say how much fuel is being delivered.

Want my motor to use  the least amount of fuel which should be good for it and only have higher fueling when it is needed.  If added fuel causes heat at least for a while then having it lean as much as possible sounds good.

I really like the quality of the stock components and have never had a vehicle last as long except perhaps our 85 Mercedes.
M2 Jetta TD.  Northern Missouri