Hi,
I have been reading the discussions regarding the tuning of turbo diesel engines. My xantia have the bosch pump which is semiECU managed and I believe it is a garrett T2 turbo.
There are three steps you have to follow to make a successful tuning and that is
1. Shorten the rod to the wastegate for increasing the turbo pressure. Should be easy
2. Turn the boost compensator 1.5 to 2.5 turns to get better performance when the turbo is not yet working properly. On my car this is situated under a round brass plate which is on the top of the pump. should be very easy
3. Increasing the max fuel adjustment screw. This seems to be very difficult.
No one has been able to say where it is exactly located or how to do it. Some say that you have to open up the diaphragm lid and turn the diaphragm 90 degrees and some says also that you have to do also 5 extra notches clockwise on the notched wheel below the diaphragm.
And last but not least they say that it is covered by a tampering shield which is really hard to get at, and some even say that you have to take the pump of the engine. Where the tampering shield is and where the screw is underneath that beats me.
<b>Can anyone please tell me how to adjust the max fuel screw and where it is located?</b>
dagkl[:(]
97 Xantia TD tuning and max fuel screw
Moderator: RichardW
There is masses of information on tuning turbo diesel engines on the LandRover and other 4X4 sites like the John Craddock one. I thought I'd print out a thread on the subject for my brother who suffers from RangeRovers but realised in time it ran to 75 pages!
The max fuel screw on the RotoDiesel pump is simply the throttle stop screw which is initially sealed with plastic.
jeremy
The max fuel screw on the RotoDiesel pump is simply the throttle stop screw which is initially sealed with plastic.
jeremy
-
Dave Burns
- Posts: 1915
- Joined: 14 May 2001, 05:30
- Location: United Kingdom
- My Cars:
- x 2
Maximum fuel delivery screw is indeed out of sight under the security cover, and yes the pump does have to come off to remove it.
Boost fuel delivery is increased by rotating the control cone (fixed to the rubber diaphragm) you will see a wear mark on it where the guide pin has rubbed against it, the control cone is machined excentricaly, turning it to allow the guide pin to protrude further into the control cones bore will increase the fuel during boost conditions.
There is a lip on the bottom of the control cone at one side, you may have to completely rotate the diaphragm to push the guide pin back (to clear the lip) before it can be lifted out.
Make accurate notes of where everything is set to before doing any adjustments, then when you've got it smoking like a b@stard you can go back to square one and start chapter two[:D]
Jeremy, that would be the maximum engine speed adjustment, getting more (or less) fuel in on the Lucas is done with the transfer pressure screw.
Dave
Boost fuel delivery is increased by rotating the control cone (fixed to the rubber diaphragm) you will see a wear mark on it where the guide pin has rubbed against it, the control cone is machined excentricaly, turning it to allow the guide pin to protrude further into the control cones bore will increase the fuel during boost conditions.
There is a lip on the bottom of the control cone at one side, you may have to completely rotate the diaphragm to push the guide pin back (to clear the lip) before it can be lifted out.
Make accurate notes of where everything is set to before doing any adjustments, then when you've got it smoking like a b@stard you can go back to square one and start chapter two[:D]
Jeremy, that would be the maximum engine speed adjustment, getting more (or less) fuel in on the Lucas is done with the transfer pressure screw.
Dave
On the latter pumps you cannot get to the max fuel screw. You'll find that the other adjustments should be sufficient. There are three basic pump adjustments and the turbo adjustment:
1. The 'smoke' screw on top of the pump diaphragm assembly (under the 'brass' anti-tamper cap; this will eventually need to be backed-off (i.e. unscrewed). Mine is now backed-off 2½ turns.
2. The diaphragm and pin that graduated the boost fuel as per Dave Burns' post. Reading around suggests a 90-degree clockwise turn.
3. The diaphragm tension - a serrated wheel under the diaphragm rubber that increases or decreases the ease of movement of the diaphragm and pin. Reading suggests a 5 notch anti-clockwise adjustment.
4. Screw in the turbo wastegate actuator rod to reduce its length.
I began the easy way by upping the ‘smoke’ screw and screwing it in one turn and shortening the turbo rod by 5 turns. The ‘smoke’ screw adjustment alone makes the car much more driveable giving more fuel at low revs.
Some months later (I’m not a fast worker!) I adjusted the diaphragm and tensioner and the pickup increased dramatically. Due to excess smoke (read wasted diesel) I have now backed off the ‘smoke’ screw to cancel the initial screw in and then a further 2½ turns out.
As I understand it, the ‘smoke’ screw on top of the assembly presses on the diaphragm pin and gives the initial (off-boost) fuelling. As you rotate the pin to give increased flow you then have to reduce the initial fuelling to bring the off-boost fuelling back to near the original level. The freeness of the diaphragm assembly to push in the pin to give boost fuelling is adjusted by the tensioner wheel. Some sites say the range of travel of the pin can be increased by shaving the bottom washer (under the wheel) to make it thinner.
Overall, I’d say that I have a much more flexible car to drive; it has good mid-range acceleration and I've saved between 3-5 mpg despite the poor car getting driven much harder. Time will tell if I blow the engine.
Dave, I’d like more info on the diaphragm and pin assembly. I simply turned the whole lot - diaphragm, pin and all. Should the pin be unscrewed at the top so that it can be rotated and the diaphragm remain still? How can you tell exactly where the pin should be positioned to give the most fuel?
1. The 'smoke' screw on top of the pump diaphragm assembly (under the 'brass' anti-tamper cap; this will eventually need to be backed-off (i.e. unscrewed). Mine is now backed-off 2½ turns.
2. The diaphragm and pin that graduated the boost fuel as per Dave Burns' post. Reading around suggests a 90-degree clockwise turn.
3. The diaphragm tension - a serrated wheel under the diaphragm rubber that increases or decreases the ease of movement of the diaphragm and pin. Reading suggests a 5 notch anti-clockwise adjustment.
4. Screw in the turbo wastegate actuator rod to reduce its length.
I began the easy way by upping the ‘smoke’ screw and screwing it in one turn and shortening the turbo rod by 5 turns. The ‘smoke’ screw adjustment alone makes the car much more driveable giving more fuel at low revs.
Some months later (I’m not a fast worker!) I adjusted the diaphragm and tensioner and the pickup increased dramatically. Due to excess smoke (read wasted diesel) I have now backed off the ‘smoke’ screw to cancel the initial screw in and then a further 2½ turns out.
As I understand it, the ‘smoke’ screw on top of the assembly presses on the diaphragm pin and gives the initial (off-boost) fuelling. As you rotate the pin to give increased flow you then have to reduce the initial fuelling to bring the off-boost fuelling back to near the original level. The freeness of the diaphragm assembly to push in the pin to give boost fuelling is adjusted by the tensioner wheel. Some sites say the range of travel of the pin can be increased by shaving the bottom washer (under the wheel) to make it thinner.
Overall, I’d say that I have a much more flexible car to drive; it has good mid-range acceleration and I've saved between 3-5 mpg despite the poor car getting driven much harder. Time will tell if I blow the engine.
Dave, I’d like more info on the diaphragm and pin assembly. I simply turned the whole lot - diaphragm, pin and all. Should the pin be unscrewed at the top so that it can be rotated and the diaphragm remain still? How can you tell exactly where the pin should be positioned to give the most fuel?
Thank you very much all of you.
I have done the wastegate now, but didnt notice any difference. Turned it 7 complete turns inwards, and it was a littlebit more difficult to reconnect afterwards.
I have not done anything else yet, awaiting your answers, but I will have a go at the diaphragm and diaphragm tension very soon.
Best regards dagkl[8D]
I have done the wastegate now, but didnt notice any difference. Turned it 7 complete turns inwards, and it was a littlebit more difficult to reconnect afterwards.
I have not done anything else yet, awaiting your answers, but I will have a go at the diaphragm and diaphragm tension very soon.
Best regards dagkl[8D]