Tdi Injector Pump Tweaking - the short guide.
---------------------------------------------------------------------
THERE ARE NO GUARANTEES THAT THE ADJUSTMENTS ARE SAFE FOR YOUR ENGINE
IF YOU DO THESE ADJUSTMENTS THEY ARE DONE AT YOUR OWN RISK.
READ ALL OF THE INFORMATION BELOW BEFORE YOU START !
Remember - this will void any remaining warranty.
---------------------------------------------------------------------
Much more detailed information is already out there on the net in various forms, but since i am doing this for a friend, i've put it on the web too.
Look in the technical section of LRE for a huge thread on it. I really recommend that you read that thread as it discusses a lot of the side effects ( esp EGT ).[/b]
A short description of the pumpThe 3 simple bits of the fuel pump you can adjust are:
1) The smoke screw
2) The diaphram and cone
3) The star wheel.
A description of each in short:
The smoke screw pre-presses down the diaphram slightly which tells the pump to deliver a little bit of extra fuel even without boost.
The diaphram and cone controls the ratio between boost pressure and associated fuel delivered. A small pin ( which controls fuel ) slides against the side of the cone. As the diaphram is pushed down, the pin slides inwards against slope of the cone, and so more fuel gets delivered. As you look at the profile of the cone, it has different slopes depending on which angle faces the pin. So depending on its rotation, you can set which slope faces the pin, and so which ratio of fuel to boost pressure is delivered.
You can see the different slopes in this picture ( sorry its a little blurred )
The star wheel controls a spring which resists the diaphram being pushed down. So this preloads some resistance against the diaphram moving and so limits how much fuel is delivered until a certain boost pressure is reached.
What to look for when your adjusting the pumpBasically, you are increasing the fuel delivery across the range of the engine revs. Its best to do changes 1 at a time to see what difference they make. Once you have done a change, take the car out for a spin. You should be trying to see if there is black puffs of smoke. If there is, then its overfuelling. If you get a light black haze, then thats not too bad.
You should look for smoke appearing as you push the accelerator when:
a) you pull away from a stand still, or pull away in a gear when the turbo is not working ( i.e. low revs )
b) as the turbo kicks in and stards to add boost
c) full boost ( full accleration at about 40mph in 4th gear )
If you do see black smoke, then back off your adjustment. Overfuelling will drastically reduce your mpg. In relality, I found the best balance was a little bit of extra power from before, but no smoke appearing atall and there was no noticable difference in mpg.
How to adjust each and what that adjustment does:If you stand at the right hand wing of the car and look at the engine, the pump should be facing you with the pipes coming out to the left and the timing belt casing on the right.
On a 200tdi, there are 4 screws holding the top cap on. The pipe coming from this cap goes to the turbo. The pressured air pushes down the diaphram within the cap. On a 300Tdi, there may also be a small black resisitor and wires sitting on top of the throttle cable arm. This is used for the EGR system if you have it fitted.
The smoke screw is hidden under a small centre cap. You can prise off the cap with some small screwdrivers - its fiddly. Under that you should see an inner bolt / screw with a Torx head and and outer locking nut. Loosen the locking nut to allow you to turn the inner smoke screw.
Turning the smoke screw:
Clockwise: Will increase the amount of fuel delivered without boost.
Anti-clockwise: Will decrease the amount of fuel delivered without boost.
i'd try shorter turns first - say 180deg at a time, then once it starts smoking when you push the throttle at low revs and no smoke, then back it off again some to ensure now smoke.
When you remove the 4 screws and gently take off the cap, you are faced with the rubber diaphram and cone.
BEFORE DOING ANYTHING mark the top of the metal disc with something permanent at the 12oclock position - i.e. pointing at the engine block at the top. This is so you can return it to the way it was before if you make an arse of it.
If you gently remove the diaphram bit and look at the cone, you should see how it has different slopes on the cone at different sides you'll see how turning this can affect the slope that the pin runs against.
From the average stock setup:
Clockwise will increase the fuel given under boost
Anti-clockwise will decrease the fuel given.
The common adjustment is 90deg. Again check if its smokes as the turbo is working and it accelerates - if it does smoke, then back it off a little until it stop smoking. 90deg should see a noticable improvement. You can push it further, but thats upto you.
Lastly, the star wheel. If you take the diaphram out and look at the base of the area, you'll see a spring and a cogged wheel at the bottoms. The cogged wheel is the star wheel.
The spring is what the diaphram acts against. Adjusting the start wheel affects how much pressure the spring puts against the diaphram and so how much the diaphram is allowed to move down as the turbo supplies boost pressure to the top of the diaphram.
Again, before you make any adjustments, mark the star wheel at 12oclock pointing to the engine block so you know its original position.
To adjust:
clockwise will lower the preload of the spring and allow the pump to deliver more fuel.
anti-clockwise will increase the spring preload and reduce the fuel delivery rate.
A common adjustment is 90deg clockwise. As always check if its smoking under boost.
And thats it.
The one which will probably make the most noticable and best difference is adjusting the diaphram. I did a 90deg turn on a friends and he says he is highly delighted with the results. Nothing else was adjusted.
