Thread: Diesel Exhaust Silencing.

Originally Posted by Dougal

Thanks guys.

So just to be clear, perforated straight through resonator in the middle and a baffled muffler out the back?
As I understand it, you need to break the resonant frequencies in the middle of the pipe and then the muffler/silencer at the end is for taking out the residual pulsing?

I want this to be no noisier than any other standard diesel ute/4wd. It's a fully sick work car.

There, I fixed it for you...

I would go baffled high flow main, and res at rear. OR no main and a high quality Res at rear only.

JC

My only frames of reference at the moment are:

My 4BD1T has a large centrally mounted muffler (I have no idea of the internals, it's oval and offset in/out) and the only time it has ever droned was when I popped the wastegate to drop all boost while I was tuning the boost compensator.
The drone was quite impressive. 2.25" pipe (the next project).

This car has a small oval centred in/out centrally mounted and a big oval offset rear. It's very quiet, but at that restrictive, it has to be.

So, baffles centre and perforated rear? I am tight for room in the middle, it's a car so the driveshaft and muffler share the same tunnel.
In the rear off-set fits best, but centre-centre will also work.

Offset res at rear will be fine, as big as will fit and then will still 'look' factory. Try no middle first then, it may be just fine


JC

Originally Posted by justinc

Offset res at rear will be fine, as big as will fit and then will still 'look' factory. Try no middle first then, it may be just fine


JC

Thanks, that is plan A.
So what do you personally look for in a resonator?

I used a 3" Fibreglass packed straight through barrel res on the rear of my RRC, it was very quiet with the 4.7 V8 and I left it on there with the 4BD1t.

It performed fine, I was worried about sooting it up being glass packed, but it was still OK after 120K and then all got ditched for a complete Td5 Defender system when I fitted it all up to the 110.

I am not by any means a gasflow expert as much as some others here, but my idea centres around a large pulse absorbing cavern that offers little or no restriction to main flow. Whether it is material packed (F'glass etc), baffled/ chambered or louvred is the question for experts in the field.

Just in adition, the centre muffler in the 200Tdi disco is actually straight through, as in you can see daylight through it, I would say there would be very little advantage removing one of those except to generate more noise. Same with there rear resonator, it is pretty unrestrictive too. The 300 Tdi Disco has an offset rear resonator, but similar main muffler.

JC

Standard 300Tdi Deefer has a straight through, centre/centre glass pack main muffler (very large oval) and a straight through centre/centre glass pack resonator at the back.

The resonator that was recommended by a very experienced muffler/exhaust shop for the 3" system is a 5" round glass pack straight through centre/centre item and that took most of the sting and most resonance/drone out of the system.

I still have drone at cruising speed, but the 'main' muffler is a heavy wall 4" home made straight through glass pack and is inadequate.
Just no where near enough depth in the glass, but I had a 4" diameter oil separator and just put a hole saw through the ends, drilled a 3" pipe and wrapped/packed it.
I knew it wouldn't be enough, I've made mufflers before, but I had the material and I'm cheap

The big problem is the 3" pipe.
It acts as an amplifier.

At a guess a standard 60mm 300Tdi system would be quieter sans muffler/resonator.

Forgot to add, most systems I've played with have the resonator at the rear, but not all, eg dear old Dads ED falcon has a sort of small resonator/sonic box (which I removed as he'd bashed it so much) prior to the main muffler as well as a larger resonator at the rear of the system.

Originally Posted by rick130

Standard 300Tdi Deefer has a straight through, centre/centre glass pack main muffler (very large oval) and a straight through centre/centre glass pack resonator at the back.

The resonator that was recommended by a very experienced muffler/exhaust shop for the 3" system is a 5" round glass pack straight through centre/centre item and that took most of the sting and most resonance/drone out of the system.

I still have drone at cruising speed, but the 'main' muffler is a heavy wall 4" home made straight through glass pack and is inadequate.
Just no where near enough depth in the glass, but I had a 4" diameter oil separator and just put a hole saw through the ends, drilled a 3" pipe and wrapped/packed it.
I knew it wouldn't be enough, I've made mufflers before, but I had the material and I'm cheap

The big problem is the 3" pipe.
It acts as an amplifier.

At a guess a standard 60mm 300Tdi system would be quieter sans muffler/resonator.

Forgot to add, most systems I've played with have the resonator at the rear, but not all, eg dear old Dads ED falcon has a sort of small resonator/sonic box (which I removed as he'd bashed it so much) prior to the main muffler as well as a larger resonator at the rear of the system.

i have a customer with a tdi 110 with no mufflers whatsoever, and a standard pipe diameter system. it sounds horrible and really intrudes. it would be fine with just a factory resonator at the rear imo.

the 6 cyl falcon from xd onward had the resonant chamber at the front, was quite effective but due to being hammered by rocks etc they generally get trashed.

dougal, are we allowed to ask for more info on the vehicle, or is it an embarrassment?

jc

Originally Posted by justinc

dougal, are we allowed to ask for more info on the vehicle, or is it an embarrassment?

jc

Yeah sure.
It's one of the japanese import freaks, that don't fit with any car actually sold new in NZ or Aus.
It's essentially a Nissan Wingroad (small pulsar based station wagon), but 4wd, manual and with a 2.2 diesel 16v twin cam engine in it (Nissan YD22)
Transverse fwd setup with a viscous 4wd to the rear axle. A bit like the Honda CRV in that front wheels always drive, back wheels push if the fronts slip.

Stock for this turbo is ~13psi boost which is ~250Nm and 81kw. I have a custom built GT1856V turbo for it which if I can get enough fuel can provide 26psi of intercooled goodness. I have an injection pump from the Navara YD25 engine which can provide enough fuel for ~450Nm and a good honest 200hp. But it's an EFI diesel, I'm the only one in the world tuning them and it's putting up the occasional fight.

It's the work hack that does pickups, deliveries and gets used for sampling work offroad around mine sites.