Jag lämnar inga som helst garantier på att detta funkar men jag har gjort nått liknande det på min 300tdi.



Here is How to Increase Your TDi Performance - almost for free ! 





So, you want to know how to get more power out of your 300Tdi (or 200 Tdi for that matter)? These engines are both fitted with the Bosch VE type fuel pumps, and although they work at different out-put pressures, and some are fitted with immobiliser valves and throttle position sensors, essentially they work in exactly the same way.

This is not the case with the electronically controlled versions, where an engine management system is employed and there is no direct accelerator peddle to throttle link – the following methods of adjustment should not be used on these types of fuel injection distributor pumps. These engines can be ‘chipped’ to get the same sort of power increase.


Below is what I have done.




Remember - this will void any remaining warranty.



I first of all went to a Japanese Car Breakers yard and bought a rather nice big intercooler from a 1990 Toyota Supra. It was in excellent condition, is about twice the size of the original Disco item, and cost £35.


I then bought some reinforced 50mm rubber hose and some pre-formed 50mm reinforced rubber hose ’90 degree Bends’. I then fitted the new intercooler in-front of the Air-Con Radiator assembly and plumbed in the pipe-work to the original intercooler inlet. I now have three times the cooling capacity of the original intercooler. This means more cold air = more power !!!


However, all this extra plumbing has added a little more resistance to the air flow, which means that you get your 1 bar at the turbo outlet, but you don’t get 1 bar at the inlet valves. To get over this, drill and tap a hole in the inlet manifold (plenum chamber) and screw in barbed hose fitting (available from your local plumbing merchant for about £1). Get a bit of tube and push it over this fitting and lead it down to your waste-gate actuator – plug it into that and blank off the hose you had to pull off, that leads back to the turbo outlet. Thus the waste-gate will now only get 1 bar when you get 1 bar at the inlet valves, and then it will start opening.


I plumbed a ‘T’ into the above fitting and led a hose to an accurate pressure gauge mounted on the dash, so I can monitor the turbo boost. This can help you to drive economically too, but it allows you to see how well you turbo is working.


If needs be, you can shorten the waste-gate actuator rod and increase the boost. You may need to remove the actuator and cut a bit off the end of the rod to allow sufficient adjustment in the sleeve portion (don’t take too much off at once – better do it in 3mm increments !). What you will find is the rod is too long to get more boost, as too much of it screws into the sleeve and bottoms out. You will have to shorten it quite a way to get more than 1 bar boost – but this is often all you need. 200 Tdis run at 0.7 – 0.8 bar – you can safely increase this to 1 bar – 300Tdi’s run at 1 bar already – best left alone!


In doing this you will find that you are actually having to pull the rod against the actuator spring to get it back onto the waste-gate – this is quite fiddly – use locking pliers and mind your fingers! Ensure you put the circlip back on. This means that the actuator spring is now holding the waste-gate shut, and means that more boost is required to overcome the spring before the waste-gate is opened. It won’t fully open now either, so boost pressure is held at a constantly higher pressure for longer.


Now you have got all that extra nice cool air at 1 bar, you need the fuel to go with it to get the extra performance. Here’s how to do that:



Diagram 1 Diagram 2 Diagram 3


All Adjustments can be made without removing the pump from the engine.

Low manifold pressure (boost) fuel delivery adjustment.

See: ‘Smoke Adjustment Screw’ in either diagram 1 or 2

This adjustment is fairly simple and will help considerably around town at low engine speeds and low boost conditions.

There is a small cap in the centre of the ‘ automatic fuel-control device’ (AFC) on top of the pump (the ‘appendage’ that is plumbed to the intake manifold and restricts the amount of fuel injected until the manifold pressure is above atmospheric). This cap can be readily removed with two small screwdrivers and a gentle rocking motion.

Beneath the cap is a torx T-25 screw and a lock nut that holds it. The locknut is 13 mm and has a ‘break-away torque’ of around 100 in-lbs. Turn the T-25 screw 2 turns clockwise and tighten the locknut to 125 in-lbs. For additional fuel (and smoke) the screw may be turned farther (CW). Back it off (CCW) to reduce smoke.

NOTE: this will increase the exhaust gas temperature (EGT) by about 75 degrees F on long hills. Clean the plug with Brake Cleaner and then seal it with LocTite pipe thread sealant with teflon. Externally, it will appear original.



Full load fuel delivery rate adjustment.

See: Diagram 3

This adjustment will TURN UP THE POWER and smoke.

NOTE: this will raise the EGT very quickly at full throttle.

The main adjustment is found under the Diaphragm within the fuel control device described above. This is held in place with the 4-screw cover.

MARK THE POSITION OF THE DIAPHRAGM, then remove the diaphragm - there is a stamped tick mark on it, so use a magic marker or scribe to note the position of the diaphragm ‘v’ housing.

Remove the diaphragm and pin, and note the pin is both tapered and on an eccentric. Usually, rotating the pin 120 degrees clockwise will cause the machined cone to go to the ‘richest’ setting (smallest diameter, effectively) part of the pin.

You may want to start at 90 degrees, and then go further if that does not produce the power you want. The further you turn it, the higher and faster EGT will climb. The fuel stop lever runs up and down the conical section of this pin.

NOTE: the way to install the pin is such that allows maximum travel of the fuel stop lever that hits this pin and is perpendicular to it.

CAUTION: mark stuff so you can put it back the way it was !

After adjusting the diaphragm eccentric pin, the low boost fuel rate may need to be adjusted slightly to reduce low speed smoke.

How it works:

The eccentric tapered pin that’s attached to the diaphragm is the FUEL DELIVERY RATE pin.

From above, looking down at the pump, almost to the bottom of the bore that the delivery rate pin came out of, is the bore that the fuel stop lever rides in. The linear axis or centre-line of the fuel stop lever is parallel to the axis of the pump drive shaft, or the engine crank shaft. The movement of the delivery rate pin (down with increasing boost levels) allows the fuel stop lever (which by internal spring pressure is contacting it) to contact the increasingly smaller diameter. This allows the fuel stop lever to move rearward (on the fuel delivery pin), which increases the fuel delivery rate. As a note: according to the Bosch injection manual, the “stock” or base line for the diaphragm position is 12:00 as you look at the pump from the side of the engine. In other words, the tick mark is toward the valve cover, for the normal setting. If you look at the underside of the diaphragm, you can see where the eccentric aspect of the Fuel Delivery Rate Pin would push the fuel stop lever deepest toward the front of the pump, that is the LEAST delivery rate setting. Consider that 12:00. Rotating the diaphragm clockwise from that point to 3:00 is a good place to go. Depending on the injectors that are in, and your turbo boost, you may want to turn a little more.


Automatic Fuel Control Star Wheel Adjustment

See: ‘Starwheel’, diagram 1

Remove the cap fitted with the 4 straight head screws. Under the AFC diaphragm and spring is a star wheel adjustment which sets the spring tension on the FUEL DELIVERY RATE PIN diaphragm. If your star wheel (under the AFC spring) is set too high, the delivery rate pin won’t move downward as it should with increasing boost levels. Turning the star wheel up (counter-clockwise) increases the spring pressure, and slows the delivery rate. Turning the star wheel down (clockwise) in ¼ turn increments until you smoke, then back off (counter-clockwise) until the smoke has gone to your satisfaction, or until just smokes under power (a black haze, not a black soot cloud) is ok. The retaining lock spring doesn’t have to be removed, the star wheel will rotate with a small screwdriver gently placed and pried between the wheel and it.

CAUTION: Note the original location of the wheel, mark it, and count any turns for reference.

Remember: Star wheel down = less spring resistance = increased fuel delivery rate


Full Power Adjustment


See ‘Power Adjustment Screw’, diagram 2

On the rear of the pump, partially concealed by the fuel lines, and under a plastic ‘anti-tamper’ cap is an other adjustment screw. Remove the plastic cap and the metal collar tack-welded to the screw, loosen the jam-nut, and turn the power adjustment screw clockwise about 11/2 to 2 turns. After turning the Full Power Adjustment, you may need to re-adjust the Smoke Adjustment Screw to reduce low speed smoke, and the idle screw or throttle linkage to correct the idle speed.

To remove the metal collar it is best to use a ‘Dremmel’ type grinder, or very carefully using an electric drill and 2mm or smaller drill bit, drill a series of holes along the collar and then gently chisel it off with a very sharp cold chisel. The collar appears to be made out of a hardened steel, so a very sharp drill bit is required.


Idle Adjustment:

See ‘Idle Speed Screw’ Diagram 3

Once you have done the above, you will probably need to reset the idle speed adjustment. Loosen the lock nut and then unscrew (reduce revs) or screw in (increases revs) the idle stop until you get 750 – 800 RPM, then tighten the lock nut and recheck you haven’t moved the setting. Most, but not all, disco’s have a rev counter, but you can set those that don’t have one by putting a dab of white paint (Tippex correcting fluid is good) on the crank pulley (with the engine stationary!). Connect a standard timing light (according to manufacturers instructions) to a petrol engine car fitted with a rev counter and parked close enough for the timing light to reach into the engine bay of your Disco. Start both engines and if the petrol engine is held at the revs you want the Diesel engine set to, the correct revs on the diesel engine are reached when your painted mark is stationary.


Additional Notes:

If your smoke is only at full throttle load - back off the full load screw.

If your smoke is at low end through pull-up to full power - back down the delivery rate.

If smoke is heavy at immediate start-up - fine adjust the smoke set screw.


In order to increase the horsepower one must carefully make two adjustments: one is in the smoke-limiter and will be adjusted to allow greater fuel with low manifold pressure (initially, this is adjusted to minimise black smoke at low rpm/low manifold pressure conditions... but, we cannot build exhaust manifold pressure without fuel !). You must remove the circular seal-plug from the centre of the AFC device. This reveals the first adjustment. This adjustment will markedly affect the feel of the cars pull-a-way power, making it pull from a stop more strongly. Adjust this in ¼-turn increments until you ‘like’ the feel and record the adjustment so you can return it to ‘normal’ in preparation for a smoke opacity test for the MOT.

The second adjustment is where the real gain comes from... There is a concealed adjustment on the ‘back side’ of the pump... essentially behind the fuel lines. [See the power adjustment screw on diagram 2 above] You must uncover the adjustment screw and turn it 135-degrees clockwise.