Dtronic chip or 3" exhaust or Both????

G'day Mick,

More so on the towing side up steep inclines, then i have had problems just taking off in 2nd gear after slowing down at a set of lights on hill, its just a bit sluggish before the turbo kicks in, whether just the exhaust would make the difference, i don't know.

cheers,

Lance

Yep see your point Lance. If you go the chip, you'll generate a whole stack more heat when towing, particularly in hill climbs. I know the Navara 3L is considered a fairly reliable donk compared to the earlier Patrol 3L but I'd go the full suite if you go down that path. The 16K I spent after towing with the Pootrol has made me a bit gun-shy.

Cheers Mick

Trevor,

I spoke to Ross about 12 months ago and he went a dpchip and 2.5" exhaust, has anything changed since then, i thought he was pretty happy with his mods. I will MM him for more info.

cheers,

Lance

Hi Lance,

I am sure he his still pretty happy with it (and he should be, it goes good I reckon) but he has seen what can be achieved and why not have it all hey. He has a dyno on his rig pics of his car and the one he would like to have too. Check them out to see the difference. Get the turbo done at the same time and have figures to make modified 4.2 owners jealous. Why not go the whole hog?
Thinking on it, I recall there being a little difference in price though. Didn't seem to be that much dearer though?????

Cheers, Trevor.

G'day Marco,

What size is the exhaust, as i have spoken 3 different 4x4 exhaust mobs and they have all told me that 2.5" inch is better because the 3lt turbos need a little back pressure. Also where and who did the job.

cheers,

Lance

Lance, Beaudesert Exhausts did mine and they recommended 2 3/4 for that reason. I took there advice and was happy with the result.

I think the mandrel bends are more important than the size.

Norm C

Lance,

He got a 2.5" exhaust. He got it done in Queensland somewhere while on the road.

Cheers

Marco

Hi Lance,

I'd like one of these exhaust places to come up with some proper technical evidence that "The 3L turbos need a little back pressure". What a load of cobblers.

Turbo diesels do not 'need' any back pressure. All back pressure does is reduce the potential energy that is available to drive the exhaust gas turbine. This energy is related to the difference in both pressure and temperature of the exhaust gas in and out of the turbine. The cooler and lower the pressure at the outlet the better.

Now about exhaust sizes, let's suppose a 3" system is the optimum size for a typical 4.2L TD that may well have been fuelled-up or chipped. This seems to be the general consensus.

If this is agreed, then if it follows that a 3" system on a 3L is probably a bit of overkill. The capacity ratio is 3.0/4.2 = 0.71.

The cross-sectional area of a pipe (let's assume all sizes are inside diameter) is proportional to the square of the pipe radius. So, a 3" pipe is about 7.07 sq in., a 2.75" pipe is about 5.94 sq in and a 2.5" pipe is about 4.91 sq in.

The pipe area ratios are: 2.5": 4.91/7.07 = 0.69; 2.75": 5.94/7.07 = 0.84. Therefore a 2.5" system on a 3L is a little less than equivalent to a 3" on a 4.2 and a 2.75" system is a bit more than equivalent. Given that a 3L will typically have a higher specific output (kW/L & Nm/L), the 2.75" would seem the best choice.

All that said, I doubt many would detect any difference between equally well-made 2.5, 2.75 or 3" systems in 'blind' testing, so whatever you can get for the best price would probably do quite well. The quality and restriction of the chosen muffler will probably have a lot more influence on the overall result than the actual pipe size!

Also, people seem to get so obsessed with "mandrel bent". Unless the system is really contorted, I doubt the small extra restriction of a few conventional exhaust bends would have a lot of overall effect. If I could get a conventionally bent 3" system for significantly less than a 2.75" mandrel bent system that's what I'd go for.

Of course, Land Rover owners don't need to worry about any of this. Their 2.5L TDs come standard with properly-sized (65mm = 2.56") systems... And should you have trouble eating any STANDARD Japanese 4WD up to and including 4.2Ls, just cut-out the main muffler and replace it with a bit of straight pipe - they're still quiet enough. (And, Yes Virginia, this last paragraph IS bait...)

Ian

Ian,

Thanks for your explanation of the exhaust systems. I will do a bit more shopping around before making a decision.

cheers,

Lance