Peugeot 306 Dturbo

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First launched in 1995 the Peugeot 306 Dturbo was designed as a sporty diesel hatchback with similar equipment levels to the popular 306 XSi model. The Dturbo came with power steering, electric windows and slightly lowered suspension, along with a sports body kit. Due to the classification of the Dturbo as a sports variant of the 306 they were originally only available in a 3 door model however there are a small number of 5 door Dturbo cars in the UK.

306 Dturbo Mechanical Turbo Diesel Engine

 The 306 Dturbo was originally powered by the Peugeot XUD9TE diesel engine which was a 1.9 litre turbocharged unit developing 92bhp of power and 145 lb/ft of torque. To aid air cooling a top mounted intercooler was fitted with air ducts running from the front of the engine bay under the bonnet skin. The XUD9TE is a mechanically controlled indirect injection engine which can be easily tuned with no specialist tools required. A turbo diesel tuning guide is available in the Peugeot 306 guides section.

306 Dturbo HDi Turbo Diesel Engine

In 1999 the mechanical XUD9TE engine was replaced with a new common rail diesel engine. This engine was a 2 litre 8 valve Peugeot DW10TD and was a High pressure Direct Injection (HDi) unit. Despite producing slightly less power than the engine it replaced at 90bhp the HDi engine offers increased fuel efficiency and a healthy 167 lb/ft of torque. The Peugeot HDi90 engine fitted in the 306 did not include an intercooler and as a result the late model 306 Dturbos suffer less from turbo lag.

Popular Diesel Tuning Modifications

Increased Fuel and Boost

As standard the Peugeot turbo-diesel engines run on a very lean fuel to air ratio. It is assumed that this is to limit the amount of smoke produced by the engine however by tweaking the fuel pump and turbo boost settings of models fitted with the XUD9 mechanical engine you can increase power and fuel economy while still remaining well within UK emissions and smoke test levels. Tuning a 306 Dturbo can be done with simple tools and a DIY 306 tuning guide is available on this website.
For 306 HDi models the fuel pump settings are controlled by the on-board ECU and can not be modified by hand. There are however two common ways of increasing the fuel on an HDi equipped 306.

The first method involves having the car re-mapped, which simply means replacing the software on the ECU with a version which has increased fuel settings and different injection timings. An ECU remap can deliver as much as 40% more power and 60% more torque, however do make sure that if you take this route you get your car mapped by a reputable diesel tuning company as you could render your ECU dead and useless if you try a cheap fix. Club-306 have teamed up with Performance Chipping who are capable of remapping 306 HDi models and offer a 15% discount to Club-306 members.

The second option to increase performance on HDi engines is to use a tuning box. These boxes plug in to the engine wiring loom under the bonnet and adjust the pressure of the fuel rail to inject more fuel into the cylinders. Power gains are not as much as an engine remap however the cost of a tuning box is much cheaper and they have been reported to give up to 30% more power and 40% more torque.

Induction Kits

Replacing the factory air inlet with an induction kit allows your engine to breathe more easily, increasing the amount of air available to the engine. An induction kit will replace the original air filter and sometimes a lot of the original pipework to reduce the distance between the engine inlet manifold and the air coming in to the engine. Induction kits are available for both mechanical XUD9 engines and HDi DW10 engines and a good quality kit from a manufacturer such as PiperCross, Green Cotton or K&N will set you back about £100.

Most induction kits can be fitted easily in under an hour using basic tools. Power gains from installing an induction kit are commonly around 3-4 bhp and a slight increase in torque however it can be more. Installing an induction kit can improve fuel economy, as the increase in torque will enable you to remain in higher gears for longer. One thing to note is that installing an induction kit will most likely make your engine sound noisier and this is one reason why they are probably not fitted as standard at the factory.

Front Mounted Intercoolers (FMICs)

When the air passes through the turbo on the way to the inlet manifold, the increase in pressure causes the air to heat up. The temperature of the compressed air is known as the charge temperature. Hot air does not combust well and can lead to increased engine temperatures and poor running when the charge temperature is high. The mechanical XUD9TE engine comes with a top mounted intercooler which provides an air-to-air heat transfer method of cooling the pressurised air in inlet pipework and lower the charge temperature to improve combustion.

With the intercooler mounted at the top of the engine heat from the engine will rise and in slow moving traffic this rising heat will reverse the effect of the intercooler and in some cases can increase charge temperatures which is known as heat soak. In a standard engine this will not be a problem but if the engine has been tuned by increasing the turbo boost pressure the charge temperatures can reach dangerous levels.

One way to reduce this effect is to replace the top mounted intercooler with an intercooler that is mounted in front of the radiator in the front bumper. This will involve having new pipework feed from the turbo to the front of the engine bay and then back to the inlet manifold at the rear right hand side of the engine. Because a front mounted intercooler will be cooled much more efficiently at higher speeds by passing air through the bumper grille and will not be sitting on top of a hot engine while in traffic front mounted intercoolers are often smaller than the top mounted units they replace. A popular replacement part is the front mounted intercooler that is used on the Ford Focus TDCi.

As the 306 HDi was not fitted with an intercooler as standard it does not suffer from the problem of heat soak, however fitting a front mounted intercooler is a popular way to increase performance as it lowers the charge temperature of the air entering the engine. It is worth noting that the Peugeot HDi110 engine fitted to the Peugeot 406 HDi and the Peugeot 307 HDi is very similar in design to the HDi90 used in the 306 with the exception that the HDi110 has an intercooler. Fitting a front mounted intercooler to a 306 HDi is about as difficult as fitting one to a mechanical turbo-diesel, although parts can be easier to find as you can sometimes use the parts commonly fitted to the 110bhp HDi engine.

An alternative to intercoolers that can be used on both types of engine is a charge-cooler. This works on the same principle as an intercooler but instead of an air-to-air transfer the heat is removed from the air by an air-to-water exchange. Think of a chargecooler as an intercooler dipped in a bucket of water. Because water can conduct huge amounts of heat without heating up itself a chargecooler can work better than an intercooler in most situations. If you want to fit a charge-cooler to a 306 you will need a reservoir to hold the water in, a chargecooler unit and a pump to circulate the water along with any piping. Chargecooling a 306 is an advanced turbo-diesel tuning technique but there are members of Club-306 who have successfully done this and you can ask them questions in the Club-306 members forum.

Performance Enhancing Exhaust Systems

As with petrol cars changing the exhaust on a turbo-diesel 306 can increase the speed that the exhausts gases can leave the engine. The standard exhaust system on a 306 consists of exhaust boxes that contain baffles, which restrict the free flow of exhaust gases. Replacing these exhaust sections with free-flowing sections can dramatically reduce the restrictions in the exhaust system.

A typical turbo-diesel exhaust system has a bore of between 2 and 2.5 inches. It is not recommended to increase the bore diameter of your exhaust system as increasing the bore of the system will actually slow down the speed of the gasses flowing through it. This will require the engine to work harder to expell the waste exhaust gasses which will mean less power to push the car forward!

When replacing your exhaust system it is important to get expert advice from someone who knows how exhaust systems work. Club-306 have joined up with Longlife Exhausts who offer club members a 15% discount on full stainless steel exhausts. Longlife have many years of experience and if you are planning exhaust modifications you are strongly recommended to give Longlife a ring to discuss your plans.

It can be noted that as part of the Peugeot 306 exhaust system there is a diesel particulate filter located under the front seat section of the car, which is commonly mistaken for a catalytic convertor. This partical filter is not a catalyst and it can be removed, as it can be a very restrictive section of the 306 exhaust system. It should however be noted that if removed your car might exhaust more smoke than usual however if your engine is well maintained and you have not increased the fueling too far the extra smoke will still be within the legal levels required by emmissions element of a UK MOT test.

Advance Diesel Tuning Modifications

In addition to the modifications described above it is possible to tune your Peugeot turbo-diesel car even further. It is possible to fit nitrous oxide injection kits to a 306 Dturbo, and hybrid turbos are also available. We even have members at Club-306 who have experimented with methonal injection, carbon dioxide charge cooling and intercooler water sprays. For more information on these topics you are encouraged to ask questions in the members forum. Access to the forum area requires a Club-306 membership but if you are looking for this kind of information then there is so much to know it would not be easily summarised in an article such as this.

By taking part in Peugeot 306 extreme tuning you can get your mechanical turbo diesel engine up to around 170bhp. If you have the HDi engine you can reach power figures in the reagion of 160bhp.

If you have any questions about this article please feel free to contact the author John Blackmore. Although I do not know a huge amount everything I have discussed I will do my best to answer any questions or put you in touch with someone who can help.

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