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Tuning your turbo diesel

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  • Tuning your turbo diesel

    As I keep being asked for advice on this by various people (dunno why as I'm not really an expert at this!) I've decided that until I get time to write a proper how to tune your turbo diesel article with pics etc I thought I'd start putting a few things down here to remind me what to include. So here it is a work in progress. As usual I'll add the disclaimer that all advice is given in good faith but without responsibility!

    Before you do any tuning on your TD make sure that the cam belt is good and that the fuel pump timing is correct, (you'll need a dial test indicator (DTI) gauge to do this).

    Then check that the EGR valve isn't leaking (my advice is to disconnect it and weld the bugger shut!)

    Then check the turbo boost pressure. Add a gauge if possible, this is easiest done where the boost pressure pipe comes to the fuel pump along a metal pipe around the side of the block. There is then a final length of flexible pipe that joins this to the top of the fuel pump. Put a T piece into this pipe and plumb in a boost gauge. At full boost you'll want a gnats under 1 bar/ or 13-14PSI. My turbo diesel was found to only be boosting at 0.5 bar when I got it so it is worth checking. To adjust you simply shorten or lengthen the actuator arm in the usual way. Its pretty easy on a TD compared to some cars.

    Now we can turn our eyes to the heart of the system the fuel injection pump. There are 4 basic things to adjust on the pump

    1. The smoke screw. This is the star shaped bolt thing on the top of the pump. This really is only designed to affect smoke at idle. If you screw it in you increase the fueling rate off boost however you will get a smaller increase in fueling when you go on boost. Simply screwing this screw in to get more torque is a bit of a bodge in my opinion.

    2. The starwheel. This adjusts the spring preload in the injection pump and controls the rate that fueling is increased compared to the increase in boost pressure.

    3. The diaphram position. This basically adjusts how lean or rich the fuel pump is running over the entire fueling/boost range

    4. The max fuel screw. This controls the maximum amount of fuel that the fuel pump can inject limiting the BHP of the engine to some degree.

    1 is only a fine adjustment so ignore it to start with
    2 is a coarse adjustment and the hardest to get right
    3 is the best to adjust at first as it'll give you gains throughout the rev range and it simple for the novice to set up.
    4 is best left alone for the moment.


    As a first guide undo the injection pump top and then look at the rubber diaphram. There is a metal plate on it which is marked with a dot at 3 o'clock. If the dot isn't at this position then note where it is (perhaps someone has been fiddling already!). Then twist the rubber diaphram rubber and metal plate to about half past 4. Then replace the pump top and take it for a drive. If it looks too smokey on full throttle then back it off a little. For further gains turn it further. If you need to return it back to standard simple line the markl back up with where it started off from.

    Once you are happy with the setting on full throttle then you can adjust the smoke screw on the top to reduce idle and off boost smoke. You may also need to reduce the idle speed too.

    If all that seems complicated then if you are in the sheffield area I can show you, or if you are at any of the maestro shows I'll be the one in the black and white campervan. Ask on the maestro and montego owners club stand for Dan. I'm pretty well known!

    I hope that is of some use to some people. Hopefully I'll get some pics up at some point too.

    I've not covered the potential performance increases from intercooling and supplementary fuel injection yet but I'll do this as I develop them on my van. Basically adding an intercooler allows you to run more boost without melting your pistons/valves and will also give more torque throughtout the rev range if you don't up the boost pressure anyway. Supplementary fuel injection is where things start getting fun!
    www.maestroturbo.org.uk - The Tickford Maestro Turbo Register
    www.rover200.org.uk - The Rover 200/400 (R8) Owners Club
    www.roverdiesel.co.uk - My Rover Diesel Site
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