3 litre Diesel Exhaust Size

[jjgsxr1000 Junior Member Find all posts View Profile Close jjgsxr1000]

Hi Guys.
Here we go, i'm probably going to open a can of worms here.
I'm a mechanic & own a 2002 Diesel Prado.
I have my own opinions on exhausts of course, but being new to this engine/car, i thought i would ask the people who have tried & tested things on these cars already.

I was wanting to upgrade the Exhaust system & have been surfing the topics here quite a bit.
Have noticed the long term cracks people have had with dump pipes etc.
I have a friend that does exhausts & we are keen to attack it, just sizing it right is the worry.

Question1: what size have people found to be best...... 2.5 inch, 2.75 inch or 3 inch?
I dont want to go too small & choke it, or too big & overkill either.
-I have already flicked the stock muffler & replaced it with a 2.5 inch straight through (for now), after giving the standard muffler a good whack.

Question2: Has anyone found a good dump pipe for these?
-Looking at pics of the dump pipes available, there appears to be no room to add a divider plate in there between the exhaust wheel & the wastegate valve to assist with the losses caused by turbulence once the wastegate opens.
(i'll upload some pics of these types of dump pipes when it stops telling me the file is invalid...aaaagggghhh)

http://s1129.photobucket.com/albums/m52 ... =Dump2.jpg

http://s1129.photobucket.com/albums/m52 ... =Dump1.jpg

-Does anyone do a dump pipe with a separate wastegate pipe, that plumbs back in further down, or is room just too tight?
-I will do a dump pipe also, but have yet to be convinced off an off the shelf unit that lasts without adding further bracing.

Thanks in advance. Regards, Jay

[HeathNZ Junior Member Find all posts View Profile Close HeathNZ]

Re: 3 litre Diesel Exhaust Size

I've got a 3 inch system in my shorty. Flows nice but to be honest I think its too big. It makes a droning noise at lower speeds now which can get annoying. Have a freeflow muffler and will swap it oneday as its the wrong shape and looks to be a source of future hangups.

I have the parts to make a dump pipe, but just need the flange for the turbo (basically get f##ked around as I wont pay the stupid prices I am being quoted). I have got 2.5 inch heavy wall steam pipe (internal diameter) which fits perfectly into a 3 inch flange for connecting further down the line and a tight radius 90 degree bend. The idea was to flatten the pipe so it fits the shape of the flange and then cut it and insert a piece of the bend to get it to line up where I want it to point. Then a 3 inch flange joins it to the rest of the system.

The idea of the staem pipe is that it should handle the heat of the gasses and wont crack with vibrations.

If I was to do it all again I would probably go for 2.5 inch (or 2.75 inch absolute max)

The folowing link is to an NZ site for a older prado (beam axle front) but the concept is the same. The dump pipes are quite different from this to our ones.

http://www.offroadexpress.co.nz/Forums/ ... =dump+pipe

[samo Addicted PP Member Find all posts View Profile Close samo]

Re: 3 litre Diesel Exhaust Size

ive got an 03 120 with the 1kz (same as you) i changed out the std dump pipe for an aftermarket pipe, its 65mm diamater and actually does away with 1 of the factory joints, i also have a 3inch straight through muffler and the std over axle pipe which is 2.5inch. it has made a big diffference in performance, less turbo lag and earlier spool up, has a nice note but it is a little louder then std, a mate of mine has the same dump pipe but went with the 2.5 inch muffler and it is not much lounder than std but a fair bit quieter then mine.. cheers samo

[coatesy Junior Member Find all posts View Profile Close coatesy]

I have a 2.75 inch beaudesert system including dump pipe and high flow mufler. Couldnt be happier with the results, earlier spool up and less lag more tourque and better on fuel. Just my 2 cents worth