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BOSCH VE GUIDES - LDA modifications - Printable Version

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BOSCH VE GUIDES - LDA modifications - Dan! - 06-12-2011

Before fiddling with your pump, its a good idea to have a read through my other guide - BOSCH VE GUIDES - Pump setup and fine tuning.


The LDA housing is the top part of the pump with 4 bolts holding down a dome shaped lid with a bolt in the top. The LDAâ??s job is to control and limit the fuelling per the boost pressure. See the below diagram to help understand how the system works:

[Image: bosch_ve_lda.jpg]

When the throttle shaft rotates the governor pushes on the leverset, which pushes a small dowel against the LDA â??pinâ??. The LDA pin is a shaft with an eccentric cone at the lower end. The cone is designed so it is very adjustable by just rotating it to more/less aggressive angle, and it is therefore rotated by the manufacturer to the desired angle to give a set level of fuel per boost pressure.

By rotating the pin to a steeper part of the cone, the dowel that is pushed by the leverset can travel further and will allow more fuel to be injected. As standard the XUDâ??s LDA pin is set on almost the shallowest setting and is also limited at the bottom, by the screw on the top of the LDA housing and at the top end by a small plastic washer.

When setting up your LDA for the best performance the first steps are usually to wind the screw on top out almost all the way OUT (which lets the pin sit higher up, and allows less fuel off boost) and then to remove the plastic washer (which will let the pin go down further under pressure, allowing more fuel on boost). The locknut on the top is a 13mm, which needs to be slackened and then the screw in the middle should have a torx head in it which you then use to wind the bolt out, before tightening the locknut back up. To remove the plastic washer you will have to undo the 4 bolts holding the lid down (Usually either flathead bolts or torx). Once that is removed you will be able to see a rubbery diaphragm with a metal disc in the middle. You need to hold the metal disc and rotate it 360 degrees and then gently pull it up. It should come out fairly easy with a little bit of wiggling, do not use any force or you will damage the dowel that rides on the pin! If it doesnâ??t come out easily try rotating the diaphragm again. Once that is removed you should be able to see a star wheel with a spring sitting on top of it and the small plastic washer inside the spring. Simply pick the washer up to remove it and put it somewhere safe, like in the bin or on the floor.

Once you have done the above you now have 2 choices. You can either rotate the LDA pin to a more aggressive slope or you can grind the pin to create an even more aggressive slope, giving further off/on boost fuel control. By looking at your LDA pin, you should be able to see which side is the more aggressive (Itâ??s the right hand side on the photo belowâ?¦)

[Image: LDApin.jpg]

Once you know which side of the pin you want to use, replace the pin in the hole with the chosen side facing to the left, the side which dowel comes in from.

If you want to grind the LDA pin you need to remember that the dowel pushed by the leverset can only move inwards about 60% of the thickness of the LDA pin (~6mm) See the below dimensions of a standard LDA pins eccentric cone:

[Image: LDAconedimensions.jpg]

When at the stock side of the cone there is a maximum of 2.01mm of â??rangeâ?? between min and max fuelling. When at the aggressive side there is a maximum of 2.25mm of â??rangeâ??, so although by rotating the pin you will get more fuel at full boost, you will also get more fuel off boost, and you will only gain 0.24mm of extra range (the difference between on and off boost fuelling). This is where grinding the pin becomes effective. By grinding in at â??aâ?? in the above photo, we can grind up to a maximum depth of 5.8mm and therefore end up with a range of 5.4mm!

Please note though, grinding the max end of the cone any further than 5.8mm will potentially cause problems with the seal inside the pump around the dowel. To grind the cone any further it is necessary to make â??otherâ?? modifications to the pump internally, which would allow the dowel to travel further and give more on/off boost range.

Also, when you have ground your pins slope to the desired angle, make sure the new surface is very smooth. If its rough it will wear down the end of the dowel and if it is uneven it would make on boost fuelling/power very stuttery and un-smooth.

Here is a photo of a ground LDA pin as an example of what to aim for:

[Image: GreatYarmouth-20111109-00952.jpg]

The last thing you can do to modify your LDA at this point is adjust the pre-load. If you remove the large spring, which sits under the diaphragm you will be able to get to the star wheel, which it seats on. If you look you will be able to see the star wheel is on a threaded section, meaning it can be adjusted to sit higher or lower and therefore make the spring higher/lower and apply more pressure to the underside of the diaphragm. This means that the diaphragm can be made easier or harder to push down with more/less boost. If you have hard fingers you may be able to turn the star wheel with your fingers and thumb, if not you may need to use a flat head screwdriver to rotate it. Adjusting this involves a large amount of trial an error, but what you are essentially trying to do is make the LDA pin harder to push down, so that extra fuel is not injected until full boost is achieved. If this spring is too soft the LDA pin will be pushed all the way down (and therefore full fuel injected) at far to lower boost pressure.

Generally you donâ??t want the LDA pin to be fully down until you are at ¾â??s of your full boost, but it is hard to work something like that out mathematically (I have triedâ?¦) so the best rule is to just wind the spring up a turn or so for every 5 psi over stock. Also note, if you wind the star wheel up to high the spring may become coil bound, meaning the LDA pin will not be able to travel all the way down.



Thanks, Dan.


Re: BOSCH VE GUIDES - LDA modifications - ginge191 - 09-03-2012

let me just get this straight for changing the LDA pin...

1 - remove 4 screws on pump head / cap..
2 - ....

this is as far as i know from my head, is it pretty straight forward, also when putting the new pin back in, i assuming the grounded side must be facing the 4. guide pin, in the diagram?


Re: BOSCH VE GUIDES - LDA modifications - Toby - 09-03-2012

ginge191 Wrote:let me just get this straight for changing the LDA pin...

1 - remove 4 screws on pump head / cap..
2 - ....

this is as far as i know from my head, is it pretty straight forward, also when putting the new pin back in, i assuming the grounded side must be facing the 4. guide pin, in the diagram?

Yep, remove 4 screws on the top of the compensator (you can leave the rubber tube attached).

The top (Looks like a UFO Smile ) will now twist off, and you can move it to the left of the pump.

You now twist the rubber diaphragm all the way round, and gently pull it upwards.

You can then remove the pin from the rubber diaphragm, you need a 13mm socket and a 10mm spanner iirc.

When putting it back in, make sure the ground side of the pin faces towards the left of the pump Smile (Looking from the top).

EDIT: As with all internal modifications, make sure to be gentle. Forcing things = breaking things.


Re: BOSCH VE GUIDES - LDA modifications - ginge191 - 10-03-2012

Awesome - cheers mate - ill have a crack at that tomorow!

I remember removing the cap off an old pump and dont remember anything being attached - im sure i can work it out Smile


BOSCH VE GUIDES - LDA modifications - TheGateKeeper - 10-03-2012

It's simples Smile


Re: BOSCH VE GUIDES - LDA modifications - Mattcheese31 - 10-03-2012

it's so easy even a ginner could do it . . . .Big Grin


Re: BOSCH VE GUIDES - LDA modifications - Toby - 10-03-2012

The only issue that you are likely to face is seized bolts holding the cap down, typically the flat heads because they provide less grip.

Handy tip: You can put a 1p/2p piece into the top of the bolt and use a pair of pliers to undo it. Makes it a lot easier if it is seized. I should be a Haynes manual ninja

Quote:I remember removing the cap off an old pump and dont remember anything being attached - im sure i can work it out

Nothing is attached to the cap itself, not internally at least Smile


Re: BOSCH VE GUIDES - LDA modifications - ginge191 - 10-03-2012

Adding pics with toby's explanation - complete in under 30minutes..

Toby Wrote:Yep, remove 4 screws on the top of the compensator (you can leave the rubber tube attached).

[Image: KaIuE.jpg]

The top (Looks like a UFO Smile ) will now twist off, and you can move it to the left of the pump.

[Image: YtYaa.jpg]

You now twist the rubber diaphragm all the way round, and gently pull it upwards.

[Image: hDWIo.jpg]

You can then remove the pin from the rubber diaphragm, you need a 10mm socket and a 11mm spanner. Smile

[Image: UDCgT.jpg]

Put back together in reverse order.

[Image: hY9C7.jpg]

When putting it back in, make sure the ground side of the pin faces towards the left of the pump Smile (Looking from the top).

EDIT: As with all internal modifications, make sure to be gentle. Forcing things = breaking things.


Credits to Dan!


Re: BOSCH VE GUIDES - LDA modifications - Daniel306 - 13-03-2012

Dose everyone else throw away the nylon washer/spacer?


Re: BOSCH VE GUIDES - LDA modifications - Dan! - 14-03-2012

Yep, just limits maximum pin travel downwards, which is silly! Tongue


Re: BOSCH VE GUIDES - LDA modifications - Bananalad - 13-06-2012

How do you know how far to screw the lda out? Any pictures of how much thread is showing? lol

Also when putting the pin back in do you have to rotate like when you took it out?


Re: BOSCH VE GUIDES - LDA modifications - Tom - 13-06-2012

If you take the lid off you can screw it out til the threaded part sits flush with the lid lol people that do it all the time just know how far to do it but when you take the lid off you can see what i mean Smile


RE: BOSCH VE GUIDES - LDA modifications - karl1989 - 23-06-2012

ive got my lda with the ground part on the right. facing the passenger side. is this the right way?.


RE: BOSCH VE GUIDES - LDA modifications - Toby - 23-06-2012

(23-06-2012, 07:16 PM)karl1989 Wrote: ive got my lda with the ground part on the right. facing the passenger side. is this the right way?.

The ground part should face towards the drivers side, pointing at the left side of the ufo.


RE: BOSCH VE GUIDES - LDA modifications - karl1989 - 23-06-2012

ah cheers for that mate Smile. should be better when i twist it round lol


RE: BOSCH VE GUIDES - LDA modifications - bayley - 16-11-2012

can you adjust the max fuel screw while the engine is running ?


RE: BOSCH VE GUIDES - LDA modifications - Kwik - 16-11-2012

(16-11-2012, 05:54 PM)bayley Wrote: can you adjust the max fuel screw while the engine is running ?
that's the best way to do it tbh


Re: BOSCH VE GUIDES - LDA modifications - Dan! - 16-11-2012

Yep it's fine to do while the engine is running, just be aware that if you turn it up too far the idle will jump up to like 3 000rpm, so if that happens just turn it back a bit quickly! :-)


RE: BOSCH VE GUIDES - LDA modifications - bayley - 16-11-2012

lol,ideal simpler way...just got to change my gov mod and lda pin over then all done.


RE: BOSCH VE GUIDES - LDA modifications - GP123 - 26-11-2012

Quote: The last thing you can do to modify your LDA at this point is adjust the pre-load. If you remove the large spring, which sits under the diaphragm you will be able to get to the star wheel, which it seats on. If you look you will be able to see the star wheel is on a threaded section, meaning it can be adjusted to sit higher or lower and therefore make the spring higher/lower and apply more pressure to the underside of the diaphragm. This means that the diaphragm can be made easier or harder to push down with more/less boost. If you have hard fingers you may be able to turn the star wheel with your fingers and thumb, if not you may need to use a flat head screwdriver to rotate it. Adjusting this involves a large amount of trial an error, but what you are essentially trying to do is make the LDA pin harder to push down, so that extra fuel is not injected until full boost is achieved. If this spring is too soft the LDA pin will be pushed all the way down (and therefore full fuel injected) at far to lower boost pressure.

Would you be turning this spring clockwise then mate to make it harder to push on? Thanks.


Re: BOSCH VE GUIDES - LDA modifications - Dan! - 26-11-2012

Its not the spring you turn, it's the starwheel underneath it. But you have to turn it anti clockwise to raise it up and make the spring stiffer or clockwise for softer, obviously. Hope that helps mate :-)


RE: BOSCH VE GUIDES - LDA modifications - GP123 - 28-11-2012

Mate can you make me one of those grounded pins? I will pay you for your work through paypal? get back to me. I cant seem to send private messages on this yet?! but email me on glennp123@hotmail.co.uk. Thanks.


RE: BOSCH VE GUIDES - LDA modifications - Ruan - 03-12-2012

Just remember with this one, don't move the throttle whilst the pin is out, otherwise the LDA following pin will jump and and you've got to get a screwdriver back down the hole and flick it back in... Wink


RE: BOSCH VE GUIDES - LDA modifications - CJ_Derv - 03-12-2012

(03-12-2012, 10:42 AM)Ruan Wrote: Just remember with this one, don't move the throttle whilst the pin is out, otherwise the LDA following pin will jump and and you've got to get a screwdriver back down the hole and flick it back in... Wink

Good shout, i did this to check travel on pin also, realised it needed pushing back when pin wouldnt drop in haha


RE: BOSCH VE GUIDES - LDA modifications - GP123 - 27-12-2012

Ive found that when i turn the screw OUT at the top of the lid, it sort of puts the car down in power when not on boost? BUT whenever this is turned in clockwise, it makes the car nippier low down. Should i keep putting it in clockwise till i see a little bit of smoke or what would yous do here?


RE: BOSCH VE GUIDES - LDA modifications - Harky - 27-12-2012

(27-12-2012, 07:14 PM)GP123 Wrote: Ive found that when i turn the screw OUT at the top of the lid, it sort of puts the car down in power when not on boost? BUT whenever this is turned in clockwise, it makes the car nippier low down. Should i keep putting it in clockwise till i see a little bit of smoke or what would yous do here?

Turning this OUT allows you to run less fuel off boost, so yes there would be a bit less power. BUT, you can counteract this with a bit more fuel on the main fuel adjusting screw. Read through all of dans! post again and you should get the hang of it.

PS. Where abouts in N.I are you from?


RE: BOSCH VE GUIDES - LDA modifications - johnnytsa - 06-01-2013

well lad hows it goin? cant pm you on this. lost your number! hows car going?


RE: BOSCH VE GUIDES - LDA modifications - Ollie - 14-01-2013

Are all LDA piins the same on bosch pumps? My da has an old broken van pump in the shed i might have a go at grinding.


RE: BOSCH VE GUIDES - LDA modifications - samass - 28-06-2013

Where have all the pictures gone?


RE: BOSCH VE GUIDES - LDA modifications - Mattcheese31 - 28-06-2013

(28-06-2013, 05:14 PM)samass Wrote: Where have all the pictures gone?

working for me . . .Smile