V8 or TD5

What a great thread with balanced responses.

If I was doing it again I would consider a TD5 purely and only from the point of view of range. Having said that I would not give up my 4.6 D2 manual for anything - now that is torque with the Thor manifold, Bosch injection, high compression and exhaust work. Mine runs at 85 degrees C most of the time, so I avoid the risks with overhot running, and the 4.6 was typically the thickest casting. My 4.0 was excellent though and I would run it again. I think overall there is less to go wrong on a well maintained V8 (including WELL maintained cooling system) versus the TD5 but that would not stop me owning a TD5.

Personally I love how quiet and throaty the V8 is. For long range touring you cannot beat the TD5 in terms of range and ability to pick up diesel anywhere etc (although these days petrol is available even on outback properties). Personally I think overall the extra servicing costs of the TD5 compared to a V8 that has not been overheated (and has a well maintained cooling system) versus savings on fuel is just not worth it.

The off idle torque from the V8 is also a boon offroad.

If I didn't have a D2 and was going to set one up for a LOT of long distance remote touring I would go TD5. However given that my D2 is my daily driver and tows a 2 tonn boat and also does the odd long distance remote trip the V8 suits me better.

So it all comes down to what you value, what you like driving, and cost.

Cheers

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Originally Posted by Rok_Dr

Having traversed a similar path to PhilipA I have to agree with everything he says, the TD5 is far better for towing and you'll get further on a tank. Likewise I'm more than happy with the performance of the standard tune engine and pulling a 1.8 tonne van.

Steve

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Now, can I ask about the towing thing? On paper, the V8 has better power and torque than the TD5. So why is the TD5 better for towing? Is it just the fuel, or is there something else I'm missing?

I don't own a petrol V8.

Given you know the car, the low kms, it's set up, it's a no brainer. Stay with the v8. You will pay a lot of money for an equivalent Td5.

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Now, can I ask about the towing thing? On paper, the V8 has better power and torque than the TD5. So why is the TD5 better for towing? Is it just the fuel, or is there something else I'm missing?

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What is important to me anyway is holding speed on long hills on the highway.
The TD5 makes more torque than a v8 at about 2000-2200 RPM which is around the 100-110Kmh on the highway in locked top.

Now the result of this is that if you hit the enormous hill north of Buledelah going southbound you start at the bottom at 110Kmh and you are still doing 100 or so in locked top at the top of the hill towing 1000Kg.

My V8, even though tuned for torque was doing less than 100Kmh (maybe 90) and had changed back to third by the top and revving its head off.

To be fair if you get thwarted by some goose at the bottom of a hill in a TD5 you cannot regain speed up the hill as you don't have the revs to accelerate,vs the V8 where you can accelerate strongly by giving her the berries.
But it is far more prevalent that the TD5 will sail up the hills that the V8 will struggle on.
That is also a reason that I always discourage people putting hot cams in V8s.


Regards Philip A
I did all the mods on the V8 as I got sick of passing people on the flat only to be passed up the hills then having to pass again and so on. It helped a lot and a Thor D2 is maybe better than a RRC but still diesel is the Go and doing say 12L per 100Km vs the V8 doing about 16-17lper 100Km ( after mods and O2 sensors)..

I followed all the work you did on yours Phillip,,
but as you know, at 2200rpm the V8 would be making around 95% of its max torque,, which will still be more than the max put out by the TD5,, and torques are torques,, whether diesel, steam or LPG, if the weights, gear ratios, and speeds are the same, up that hill, the car with the most torques will win,,
my green cars 4L was a beauty,, but this silver one was useless. bought at roughly the came kays too,,

I remember testing a brand new TD5 when I had my 3door,, and remember keeping my 3 door,,;):D

In my case the comparison was between a bog standard 94 soft dash classic and a 03 td5 auto. The 3.9l V8's torque is 314nm at 3100rpm, while the td5 auto is 340nm at 1950 rpm. More torque lower down makes all the difference. Plus 15l/100km vs 25l/100km towing in the V8 was a no brainer. The d2 auto also has lock up on 3rd and 4th as well.

That said the std v8 d2 is 340nm at 2600rpm so the difference between it and the td5 would be a lot less.

Cheers
Steve

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That said the std v8 d2 is 340nm at 2600rpm so the difference between it and the td5 would be a lot less.

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Weeell, my 3.9 really mirrored a Thor and I believe I had MORE torque at 2600 than a Thor , and I have to say that the torque RISE to 2600 is an issue.

On the open road in top locked you are never doing 2600 unless you are going very fast. Remember V8s are artificially restricted at low revs because of the need to limit NOx, thus all the criticism of engines like Gen111 of poor low down torque.

The old TD5 has its shoulder well into the torque curve at 2000 and the turbo is pushing hard . You are over the curve so shouldering back into the Max torque at 1950RPM.

I have to say they are like chalk and cheese, and I was amazed the first time I sailed over that hill. At the time I thought why did I waste my time and effort of many years on the V8.

Always the caveat that if you are baulked at the bottom it is a sloow trip to the top . When I am going up the Hume ( from Sydney to Canberra) I am always planning for the next bigun by ensuring if possible that I am clear of trucks and caravans at the start of the climbs.
Regards Philip A

Of course you can always go the 4.6... Cheers

Thanks Gents,
And yes, a larger V8, say a Disco 3, is an option for the next rig. Although they seem pretty rare compared to the 4L 6 petrol model.

The 4.0 is getting 300nm by 2000 rpm (Max still to come) and the 4.6 has 407 nm at 2600. Can't readily see a torque curve for the Thor 4.6 high comp but it must be around 360 or so at 2000 rpm. At the same revs the TD5 has 300nm...At 100 kph the D2 would be sitting on about 2200 or so. So about 380 or so for the 4.6 Thor and building when the TD5 is falling off. The 4.0 is good for towing but the 4.6 Thor is awesome. In terms of getting caught on Hills or overtaking think too the TD5 has about 60kw at 2600 and falling torque curve and the 4.6 is maxing torque and power is at 166 kW at that point which really is an extraordinary difference. The Thor manifold and Bosch Motronic did wonders for tractable towing. My advice is go a 4.6 conversion and love the grunt and sound. Cheers