Tuning turbo diesel Peugeot 306 for better fuel economy and increased performance

Peugeot XUD9TE Turbo Diesel Engine Tuning

Peugeot's 1.9L mechanical turbo-diesel engine

I have finished adding all the pictures now, so happy tuning! I will be trying to keep this page up to date, so if you want to add your comments please use the contact John Blackmore form on my blog.

This document is a re-write of a turbo tuning guide that has been doing the rounds for a number of years. As such I must stress that a lot of the information contained within the following article has not been completely verified. The most accurate parts of this guide are the sections based on the Lucas fuel pump and the KKK turbocharger. Please note this guide is NOT suitable for HDi engines.

Information contained within the Club-306 website is provided "as is". The author and owner of club-306.com disclaim any loss or liability, either directly or indirectly as a consequence of applying the information presented herein, or in regard to the use and application of said information. No guarantee is given, either expressed or implied, in regard to the merchantability, accuracy or acceptability of the information.

 

Over time this guide will be expanded to cover more accurate explanations of each stage of the tuning process. If you would like to submit your own comments to be added to this guide please send them to the Club-306 helpdesk.

Engine

The modifications described in this article are aimed towards the Peugeot XUD9TE turbo-diesel engine. This very popular 1.9 litre turbocharged engine was used in a number of Peugeot and Citroen models throughout the nineties including the Peugeot 306, Peugeot 405, Citroen BX and Citroen ZX. It has also been reorted that this tuning guide is also suitable for some Rover turbo diesel models. The XUD9TE was eventually replaced by the more efficient Peugeot DW10TD common rail HDi engine.

The XUD9TE is a mechanical turbo-diesel engine that produces around 92bhp of power and 145lb/ft of torque in standard form. The XUD9TE is usually accompanied with an air-to-air heat exchanging intercooler. By using the methods decribed here and replacing the standard intercooler with a more efficient unit or a chargecooler it is relatively easy (and cheap) to acheive up to 130bhp from the XUD9TE. 

Club-306 would like to remind all visitors that making modifications to your car may affect affect the performance or driving characteristics of your vehicle or in the eyes of your insurance company may class it as being a higher risk. You should therefore fully consult your insurance company before and after you undertake any modifications to your vehicle so that you can be sure that you will be covered by your insurance policy. If you fail to notify your insurance company of a modification, you may be breaking your terms of insurance and therefore will not be legally covered to drive on the public highways.

 

Fuelling: The pump and compensator

The majority of the improvements to the power band are achieved by increasing the maximum fuel setting and the boost compensator fuelling. The standard car like all diesels is set-up very lean. The procedure to adjust the fuelling is not difficult, but requires many careful and small incremental changes, and many test drives until the optimum settings are found.

The limit of the performance is related to either the amount a smoke produced or/and the reduced fuel economy that can be tolerated. The smoking is un-burnt diesel, which is mainly seen when the engine is laboured off-boost i.e. under 2000 rpm.

The tuning technique described below is derived from many sources, you will not find any information on this in the Haynes manual. Although it may seem daunting at first if you work in a sensible and methodical way this procedure is safe. If you have any doubts about your ability you must seek professional help as getting this wrong could leave you car un-driveable!

Boost compensator Fuelling

  The fuel compensator is responsible for making sure that extra fuel is delivered to the engine once the turbo has come "on-boost". On the Peugeot 306 the compensator is connected to the top-mounted intercooler via a short flexible pipe. As the boost pressure increases in the intercooler the compensator acts on a diaphragm which allows more fuel to enter the fuel pump.

This increase in fuel is delivered to the engine and combined with the increase in air results in a more powerful explosion in the combustion chamber. Without extra fuel there is a limit to how much pressure the turbo can produce. In contrast without the extra air from the increased boost pressure the extra fuel will not burn, resulting in black smoke.

  The procedure to increase the boost compensator fuelling is similar on both the Lucas and Bosch pumps. The boost compensator unit can be recognised by a brass coloured diaphragm assembly connected to the intercooler by a vacuum hose.

Unscrew the external 14mm lock nut and turn the adjuster anti-clockwise. The adjustment range is about 1.5 to 2.5 turns (adjustment can be made in half turns). The setting is not so critical; running the car rich from the compensator does not make a great performance difference.

Maximum Fuel Settings

The maximum fuel setting has the greatest effect on performance controlling about 80% of fuel delivery. The maximum fuel setting is located in different positions for the Lucas and Bosch pumps.

Lucas Pump 

On the Lucas pump a large plastic plug is found on the front of the pump. This must be unscrewed and the pump will empty its contents of diesel. The plastic plug is desined so that can not be removed easily, so the easiest way to get it undone is to use a screwdriver and a hammer to tap it out. It is important not to damage the plastic plug so be careful. Put a plastic bag over the alternator to protect it.

Using a small mirror look inside the pump and you may see a hole with a recessed socket head bolt. I think it's about a 5mm size Allen key. If this can not be seen put the engine in gear and rock the car. You will see a cylinder assembly rotate in the pump. It will need to rotate about 180 degrees to reveal the maximum fuel screw.

The screw will need to be turned clockwise. To access the screw you will need to insert the long part of the Allen key. Don't use a ball type driver, as the ball may break-off in the pump. The screw to quite tight and so a spanner will need to be used on the end of the key.

The range of adjustment is a relative 20 to 40 degrees (40 degrees is rich, make adjustments in about 10 degree increments). Replace the plug; prime the pump and test drive. Look for evidence of smoke off-boost. Repeat the procedure until the desired performance, smoke level and economy compromise is reached.

Bosch Pump

With the Bosch pump the procedure is much easier. The maximum fuel screw is located on the top right side of the pump. It will have a tamper proof fitting on it, which will need to be removed. This screw is adjusted clockwise up to about 90 degrees (again use about 10 to 20 degree increments).

Maximum Engine Speed

Another simple modification that can be made is to raise the maximum engine speed to about 5,200rpm (See the Haynes manual). It is important not to actually rev the engine this high but by raising the maximum engine speed you can reduce the effect of the rev limiter which effects the engine at about 4,600 rpm onwards. The improvement is seen when accelerating through the gears.

Turbocharger and Boost

The XUD9TE engine was fitted with a number of different tubocharger units at different times during it's production. The most common at the Garret T2 and the KKK. Later models (1998 on) may have the smaller but more efficient Garret T15 turbocharger. All units should produce about 12-13psi of boost on full load from a standard engine. Full boost is usually acheived at around 2500-3000rpm in third gear, but using a boost guage makes it very easy to see when full boost is acheived. It is highly recommended that you have a boost guage installed as tuning the engine is extremely difficult without one.

Please Note - More boost does NOT mean more power. You must have a balanced amount of boost and fuel to see any performance gain. By increasing boost pressure you will increase the charge temperature, which is the temperature of the air in the intercooler. Many other guides and forums will tell you to boost to 18psi+ which is completely wrong unless you have additional cooling such as a bigger intertercooler or a water-filled charge-cooler. By using lower boost pressures you will get higher torque, which means quicker acceleration and better fuel economy.

Garret T2 turbocharger 

On the Garret-type turbo the boost pressure is increased by shortening the waste-gate adjustment arm. You will need to disconnect the wastegate arm at one end and then loosen the threads to shorten the arm. Reconnect the adjustment arm and take the car for a test drive. Unfortunately the tuning process is not an exact science and there is no fixed amount by which the adjustment arm needs to be shortened by. You are aiming to produce a maximum boost of around 15-16psi if you have a standard intercooler however with additional cooling it is possible to go as far as 19-20psi.

 

KKK turbocharger

The KKK type turbo has a locking nut and adjuster on the end of it. The locking nut is either a 8mm or 9mm nut and the adjuster. The adjuster is turned using a 2.5mm allen key. As with the Garret there is no hard and fast rule to tuning the KKK however 2 complete turns clockwise is a very good place to start.

Once you have test-driven the car adjust the turbo accordingly a half turn at a time. Tightening the wastegate (clockwise) increases boost and loosening the wastegate (anti-clockwise) will reduce the boost. As with the Garret the magic number is around 15-16psi. Boosting any higher than this without proper cooling is not recommended as the charge temperature increases significant above 15psi.

Remember, the boost pressures and fuelling are not independent on a diesel engine. The waste gate is a final mechanical pressure blow-off and if the fuelling is the limiting factor additional boost will not be gained. Hence, when tuning the car check the boost as the fuel increments are made. This is where the aforementioned boost guage comes in handy.

You are reminded that the effects of tuning vary from one engine to another. From personal experience my own 306 turbo-diesel had a KKK turbo running at 15psi and a Lucas pump and was rolling roaded at 108bhp. In addition to the tuning I also had a K&N induction kit, de-cat exhaust and a Magnex backbox.

Summary of the Tuning procedure

1. Check the boost, it must be at least 12PSI @ 3000 rpm under full load.
2. Adjust boost compensation fuelling on the pump - set when a small increase in the amount of smoke is seen when the engine is laboured under 2000 rpm.
3. Adjust maximum fuelling on pump - set when a small amount of smoke is seen when the engine is laboured under 2000 rpm.
4. Check the boost, and adjust the wastegate if necessary.
5. Repeat step 3 - clockwise to increase fuel or anti-clockwise to decrease fuel - until the optimum compromise is found for smoke emission, performance and fuel economy. This process of careful adjustment should be carried out over a period weeks.

Conclusion

The tuning procedere described here should only be attempted if you are completely sure of what you are doing. If you have any questions at all make sure you ask in the engine tuning section of the Club-306 forum. There are a number of members who have had a lot of experience in tuning turbo-diesel engines so you might even be able to talk one of them into helping you. If you are completely unsure I am sure you can find someone on the forum who would be willing to do the tuning for you for a fee.

A lot of this guide has been re-written from my own experience and for that reason it might be different from other guides on the Internet. We are aware that a version of this guide that originally appeared on johns306.com is being sold on eBay. Not only is this copyright theft but the information in that guide is also incorrect in light of more findings on how best to tune the XUD9TE engine. If you have bought the aforementioned guide on eBay please get in touch via the helpdesk so that we take apropriate action.