Thread: Highway cruising 300tdi

1.2 Box
ZF Auto
32" Tyres
Standard 300tdi motor (IP tamper caps all in place)
Carrying the usual kit, bull bar, tow bar, tools etc = 2280kg

Can sit on 110kph (GPS) easily!

It might knock off a bit up steep inclines, but it can do 110kph regardless of wind and across most gradients. It can do 130kph on the flat no problem, and will push on to 140kph

My previous 300tdi auto was stock standard, same set up, smaller tyres and it struggled to go beyond 115kph. So it goes to show how the tune and health of the motor can make a big difference, especially when it is 20+ years on from factory fresh.

A 300tdi auto when new had no problem holding 120-130kph. I agree with Red90, the old motors that are struggling to do that now are either in a poor state of tune or have lost compression. With the high kms these motors have seen, its not surprising we get such varied reports on performance.

The speed limit in the UK is 120kph, if land rover had sold D1s that couldn't even hold the UK speed limit, it would have been killed in the reviews, and sales would have suffered big time.

Do all the easy stuff first, and start with a compression test. It would be a waste to load up on fuel/boost if you are already struggling due to poor compression.

Once satisfied that the motor is in good health and tuned to spec, look to up the main fuel delivery screw. Adjusting the boost compensator on an auto will not be as effective, the auto gets your revs up much faster than a manual. Increasing max fuel delivery will add power across the rev range. Just do it in small quarter turn increments till you are getting up to 690C on a hard push. A little tweak can make a BIG difference.

When you are hitting your EGT limit, look at a bigger intercooler, then turn up your fuel again. Hit the limit again and still want more, look at a bigger turbo for more PSI, turn up your fuel again.

Its easy to add fuel to these motors, you don't need a tune shop if you have EGT/Boost gauges and some tools.

My 200TDI defender is tuned up big time, 22psi VNT, performance head, double core intercooler, ceramic coated headers, 2.5" straight through exhaust, a good number of turns on the max fuel delivery screw. It has way more power than the 300tdi disco but it has a 1.2 ratio transfer case, 33" tyres, manual r380, its heavier and its an absolute brick. So it tops out at a similar speed to the 300tdi disco, and it might not beat the disco off the line if the gear changes are sloppy. So gear ratios, and weight are worth looking at too.

Did the exhaust on its own make much difference? Was thinking about changing mine.

Originally Posted by Rick1970

Did the exhaust on its own make much difference? Was thinking about changing mine.

My D1 had standard exhaust when i got it. Was one of first jobs i did. 2 3/4 inch straight through. I have a silencer box in the middle protected by chassis and then goes straight out the back.

Not sure how blocked original system was but you could certainly feel difference after i picked it up. Turbo spooled much earlier and freely. You could actually hear it, where as before you struggled to. As far as acceleration and speed not sure it made a difference. Maybe had to adjust IP to suit but I didn’t.

In terms of smoothness, it was a different vehicle. At idle (if you had very good earplugs) you almost wouldn’t know it was running. Take off was just beautifully smooth. I still get that when i have a clear air filter. Which is why I’m looking at improving my intake with a better filter housing and better geometry.

I did the exhaust at same time as turbo and snorkel delete. On its own I doubt the exhaust would have made much difference.

Unless the exhaust is rotting away, keep it, the 300tdi factory tubes are big enough for a fueled up tdi. If anything, free flow the center muffler. And then you might start looking at removing your snorkel. All for minimal gains.

Double core IC, and a twist on the max fuel screw will definitely make a noticable difference. If you can tweak the turbo wastegate for 16psi, even better. Some silicone boost hoses and good clamps for reliability. Job done. Try not to go overboard.... I know some of us cant resist!

2600kgs give or take a person or two... thats what i got when i added it all up anyway, I’ll have to get it weighed sometime and see what I’m really at. Over summer I will attempt a compression test (is this a diy..able thing? Ill have to do some more reading i think). I contacted allisport and I’m on the waiting list for a double core IC but I suspect it will be a few months.

Starting probably next weekend ill be having a look at the fueling and just turn it up a notch ( i have a egt gauge). The compression was fine a few years ago, it got checked when its head was taken out and xrayed after head gasket failure (which was rectified) but it might be worth checking again. TBH it did drive a lot better without the roof rack (which adds about 30cm in height to the vehicle) which is causing pretty significant wind resistance. Similarly without any of the other mods (the heavy ones) it held its own a bit better. I suppose its just one of those things really. (Weight + greater surface resistance = slower or same speed + more fuel). I also do get significantly better fuel economy at around 95 km/h rather than 110 (which I can do on the flat (maybe 125 at full throttle and no headwind), just not on the uphills). Happy tuning everyone. I’ll let you know what i find once ive made some changes (or possibly tested a few things)

I've got a '96 300 Tdi factory Auto ES everything as factory (including tyres), nothing rebuilt, and it will manage 140 on the flat and cruise all day on 110-120 on the Bruce between Noosa and Brisbane. Maintains 110 easily on all the hills from memory.

I've detuned the pump slightly (idle setting) to reduce smoke on startup but otherwise nothing has been touched performance wise.

330,000 kms. Everything is original including exhaust, engine, gearbox, and suspension. Some bushes, belts, radiator (x2), head gasket (preventative), bearings, fuel pump gaskets etc, but no major replacements.

Damien

Originally Posted by Fausto79

....

My manual D1 tdi has 245/75/16 and the speedo now reads about 94kmh when doing 100. Revs in 5th gear at that speed are about 2250. Before closer to 2500.

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Mine's auto, on 255/70s and I get 2250 at 100k/h indicated(which is 100k/h actual too)
It may be 2260RPM as it's the thickness of the speedo needle above the 2250 line.

Originally Posted by manic

......... Adjusting the boost compensator on an auto will not be as effective, the auto gets your revs up much faster than a manual...... .

Never heard that before....maybe that is why I have always thought that the benefit I got from that adjustment was not quite enough. Have never upped the fuel delivery so will try that this weekend.