Thread: Is the problem that I'm not a believer?

Originally Posted by DeanoH

I keep reading about the poor power characteristics of the 300 Tdi. Either I'm easily pleased, have an exceptionally powerfull example or there's nothing wrong with the 300 Tdi as is.

Admittedly my 300 Tdi powered 130 single cab ute is just one example and possibly a fair bit lighter than other LR's using this engine. As far as I know my engine hasn't been 'tweaked' to increase performance but it clips along quite nicely unloaded (I haven't tried it loaded so can't compare). SWMBO's TD5 powered D2a is an auto and whilst more powerful I reckon the manual 300 Tdi powered Defender is a lot nicer to drive through the gears than the D2a with its 'sludge box', but that's me.

My 'test hill' for those that know it is Tynong Hill on the Princess Highway eastbound near Gumbyah Park about 60 Km east of Melbourne. In the Defender with a run up of a kilometre or so I can hit the hill at 100 kph in 5th and still be doing 90+ going over the top. In 4th I can hit it at 100 kph and accelerate over the top. This is real kph not speedo kph. For those that know the hill this is not too shabby.

But the search for more hp/torque still exists for the OKA (4.5 tonne, 4 litre 110 HP Perkins with possibly the worst vehicle turbo ever invented). The Perkins uses the same Bosch VE injector pump as the 300 Tdi.

On a recent run to Mildura the OKA's injector pump decided to dump more fuel on the road than it fed to the engine. This was the result of a loose screw resulting in a 'blown' O ring on the high pressure (~100psi) side of the injector pump. Fortunately there is a very good Bosch specialist within 2 km of the BP in Mildura.

At my request the injector pump was tweaked when rebuilt, basically the pump was built to standard spec and the 'fuel screw' was advanced approx. 1/8th turn which results in about 10 % extra fuelling.

This makes a huge difference in the driveability of the OKA. Where before it was very hard work holding 100 kph on the flat but OK holding 95 or 105 kph (in 5th) it now holds 100 kph very easily and wants to keep going at 105 kph. Also where previously the cruising temp in 5th at 95 and 105 kph was 90 degrees C and at 100 was 95 degrees C it is now an even 90 degrees C across the range. It hangs onto gears longer and is a better drive, there is no smoking under load or acceleration.

The point I'm getting at here is that a simple 'tweak' of the injector pump made the OKA a much better vehicle to drive. The 300 Tdi is the same 'old style' diesel as the Perkins, perhaps the same 'tweak' will work on the Defender. A lot more driveable for no cost (assuming the injector pump is OK to start with).

Deano

The "Tweak" for the 300TDi is well documented and you find a few tutorials on this forum, but tweaking can have unforseen problems.
It is recommended that an EGT gauge be used when tweaking as extra fuel can cause higher exhaust gas temps.
Higher EGT's can cause premature wear of pistons, rings, Head gaskets, exhaust valves and Turbos, in a well worn example it will speed up wear in deteriorating parts.
So Deanoh it might pay to install an EGT gauge to ensure your tweak isn't causing damage, as a side note a 300TDi certainly is one engine that needs a tweak from conservative factory settings to realise it's potential, inside EGT safe levels, that is, Regards Frank.

summating that comment

when the engine is at rest the fuel control is under full influence of the "more fuel" spring as there is no input from the flyweights that push the fuel control to "less fuel"

so when you start cranking its injecting a full shot of fuel every time it tries to fire a pot. While its running slow the auto advance is also fully retarded, that contributes to incomplete combustion at lower speeds and ignition pressure/temperatures all of which translate to "black smoke" (pyrolytic burning) on startup. Essentially this is too much fuel not enough air running, same as when the engine is overfuelling without enough boost.

If its really cold or the engine is tired/out of tune you may get some whitening or greying of the startup smoke which is typical of low compression ignition and incomplete combustion