Thread: Comparison between 2.5" and 3" exhaust

Originally Posted by Benny_IIA

nice to see some real world results.

lets hope some td5 'experts' read this thread.

You mean like the one who has laid down thousands testing them!?

Different engines... Different characteristics...

And the days temps not the same, so not a accurate representation but still not bad.

Stick your money where your mouth is, buy the dyno time, develop the products not just see what everyone else does and do the common theme.

At one stage I had 4 systems made.

I've also made over 40 sets of custom, different length and rate coils whilst developing suspension.

At least the OP is giving it a bloody good go... And then passing the info on.
Imagine how many people appreciate his efforts.
Now who is going to stuff a 4" system on and see how that goes.....

Thanks Steve,

How did you route the exhaust dump pipe?

Originally Posted by flagg

Thanks Steve,

How did you route the exhaust dump pipe?

Inside the chassis rail. So down behind the alternator, in front of the starter, then back under starter and over the gearbox crossmember.
My sump doesn't have a wing.

Originally Posted by steveG

The muffler is an oval offset-offset configuration. Both tubes run straight into an open central chamber which is approximately the middle third of the muffler. The tubes overlap in that chamber.
I bought it from a local "old school" muffler shop (they do more bending and fabrication than bling) and explained to the guy that I was after something free flowing and it didn't have to do much silencing.

My wife couldn't detect any increase in noise level over the 2.5" system with similar muffler in the same location. Running just the dump pipe the exhaust noise was obvious (as was the increased turbo whine), but with the full pipe and muffler you're not really aware of any exhaust noise from inside the vehicle.

Chief - I thought about just running a straight pipe, but the County is set up mainly for touring and I was concerned about getting a couple of hours down the road and finding that the drone was getting to me. There's already enough sources of noise/vibration without adding the exhaust to the mix

Auh sorry Steve I forgot to mention I was referring to Dougals situation oops...

Originally Posted by Tombie

You mean like the one who has laid down thousands testing them!?

Different engines... Different characteristics...

And the days temps not the same, so not a accurate representation but still not bad.

Stick your money where your mouth is, buy the dyno time, develop the products not just see what everyone else does and do the common theme.

At one stage I had 4 systems made.


At least the OP is giving it a bloody good go... And then passing the info on.
Imagine how many people appreciate his efforts.
Now who is going to stuff a 4" system on and see how that goes.....

well the op has posted more info then I have ever seen posted by td5 alive who claim there is no power gain just that your turbo is going to over speed and destroy it self.

I would be very interested to see your dyno graphs showing the results for different systems.

No worth much. But I picked my 90 up from the exhuast shop today where I had it fitted with a 3' straight through system and it had no increase in boost pressure over the standard system which had cat fitted. Turbo is a stage 3 TT vnt though.

That coupled with the dual airbox's and uprated intake hoses made a massive difference.

Originally Posted by c.h.i.e.f

Auh sorry Steve I forgot to mention I was referring to Dougals situation oops...

Yeah I'm legally required to run a muffler. 6 monthly safety inspections here.

I have no where near the knowledge that Ben (isuzurover) has on this sort of topic but my opinion on a turbo diesel the larger diameter exhaust the better,the best would be a short cone dump pipe and simply stop "over speeding" by monitoring boost and controlling via some type of waste gate...however practicality issues are a concern so there is always going to be some sort of compromise...

Originally Posted by Dougal

Yeah I'm legally required to run a muffler. 6 monthly safety inspections here.

Auh fun nazi's...In that case a small straight through perforated resonator style muffler would be good and hopefully would pass inspection...