Exhaust Delete Pipe...

Hi all..
I am looking at getting rid of my exhaust and fitting an exhaust delete pipe, (keeping DPF)

Thing is... I wanted opinions from those who have done this mod on a D40 2007.Auto VSK...
Is it a lot louder than normal ?
Performance wise any better ?
IS IT LEGAL ?
Anything I should be aware.of?

cheers in advanced !

Not sure of the legal aspect but it does sound like an old tractor, a few members here have reported boost spikes and erratic running with the muffler removed. There are a few Youtube clips if you would like to listen to the sound.

Technically it's not legal. Any change to the emission control system warrants a defect and a fine (somewhere in the region of $13,000). "Emission" includes sound.

However, unless the vehicle is ridiculously loud, people generally don't get picked up for it.

The turbocharger will drastically reduce the volume of the exhaust note - there's a lot of energy absorbed by the turbine. If memory serves, BossHog had a 3" exhaust with no muffler and while you could hear his car coming, it wasn't excessively loud and wasn't a bad sound. Nowhere near as loud as the gorgeous roar coming from ScottyBobcat's ute though, that thing sounded sweet as!

People have stated that performance does increase with a larger exhaust and it's true that evacuating spent exhaust gas from beyond the turbocharger's outlet would allow the turbine to respond marginally better. This is probably measurable on a dyno but may be imperceptible when driving (although improvements in spool speed may be noticed). With the DPF still present though, I doubt there's going to be any gain because the DPF does provide a restriction to exhaust flow.

run a straight through muffler and you will have a nice sound plus power will be there.

the biggest restriction in the yd25 exhaust is the inlet to the catalyst. have seen plenty of people doing cat back exhaust on these engines but they are just throwing their money away. i am certain you cant remove the cat if you want to keep the DPF. and its 100% illegal if you remove it in the first place.and inveromentally irresponsible. i would say keep it as it is. even if you wanted to do a famous DPF "delete" i would advice you against that since 90% of the so called tuners are butchers with high school education

just noticed on your signature you have like 352k. i mean just keep driving like that and if you want to spend money you can make sure the cat or dpf arent blocked to begin with.

You can purchase high-flow CATs which many who upgrade to larger systems do for simplicity's sake (including a change of dump pipe).

Ok... so im a bit confused or disappointed. ..
I thought it would make a nice difference by-passing the muffler but the Cat and the DPF I guess are the main restrictors.
So, I guess the Muffler Delete Pipe would hardly make any difference other than making it illegal..? Unless the DPF is removed as well as the Cat??
and Stelianos its about 362K now.. no issues so far apart from basic tear and wear.

Strictly speaking ANY modification away from the standard inclusions are illegal. The factory devices were the ones on the test vehicle when it passed the emission controls at the time of release. Modifying those in any way changes the vehicle's emissions rendering it non-compliant. That's the sticky bit.

As said though, you're unlikely to get pinged unless it's really loud or smokes for more than 10 seconds (that's the guide the NSW police use). A "muffler delete" pipe will change the note of the engine, to hear what it's like just take your muffler off and let the car run for a bit. Connect a straight bit of pipe in the muffler's place if you're happy. It won't get so loud that the cops will be chasing you everywhere.

Thanks Old Tony.
I will try taking the muffler off for a test.
I guess im wondering now... is it going to enhance percormance in any way or Just a different tune ?

jonney said:

run a straight through muffler and you will have a nice sound plus power will be there.

Click to expand...

Hey jonney, is this the technical name? Is there a specific one for D40's or are they generic one size fits all?
and have you got a link for Ebay by any chance?
Cheers

The technical term for a straight through muffler is "pipe".

There should NOT be a huge difference in performance. The muffler does present a flow restriction to the exhaust gas - a muffler makes the flow change direction through various sized holes, which disrupts the sound also carried in the exhaust. Any change in direction must necessarily change the velocity of the gas, particularly through the smaller orifices inside the exhaust. When you change the orifice size, you increase the velocity through the orifice and increase the pressure behind it - that's the flow restriction in operation.

However the flow's already restricted enough by the CAT/DPF, but moreso by the turbine. The opening into the turbine chamber is quite small (relatively speaking) so that the gas velocity rises. At this point you WANT a higher velocity, to spin that turbine. As the exhaust leaves the turbine blades (expending its energy on the blade rotation) it loses quite a bit of energy. Because the turbine outlet is larger, the flow rate can slow down, but the exhaust gas temperature (EGT) at that point also drops anywhere between 150C and 300C depending on throttle, RPM, load, turbo vane setting etc.

After the turbocharger just off the dump pipe is the CAT. This is also a flow restrictor but it has minimal impact on engine performance. Further back (and having even less impact) is the DPF. Lastly the muffler - which will have a very little impact on performance.

That's the "why".

As for the noise, it WILL be different (explained above). Whether it's to your liking is hard to say. Getting a nice note out of a turbocharged engine is difficult because the exhaust gas is all compressed and passed through a single, small orifice which munges the sound. The lovely sound you get from a V8 comes partly because two banks of cylinders are run through separate exhausts.

Some of that sound is induction noise too. I took the air intake pipes off my XJS Jaguar (5.3L V12) and it made a gorgeous sound. I've removed the baffles from my Navara's intake and all it does is rattle lots, although my turbocharger is very clearly audible now. I will be putting the baffles back - I don't like the rattling sound.

There is such thing as a "straight through" muffler Tony. Its just a perforated tube wrapped in packing material and is what virtually every performance exhaust on the market uses these days, also resonators "hotdog mufflers, most motorcycle mufflers.


I agree with everything else you are saying though.

And you have to throw up some pics of the Big Cat in the "Whats your Other Car" thread or whatever its called, wherever that went... Hubba Hubba!

a good example of a Straight Through Muffler is the good old [ Hotdog Muffler ]
it does have internal glass packing but you can look straight through it like a telescope for example. this is why these types of mufflers are classed as Straight Throughs. normal mufflers have whats called Baffles and you can,t look through them due to the baffle plates, so the better powered mufflers are definetly the Straight Through Types.

Rabbid, I did add a BIG smiley afterwards! I used to love the sound of a hot dog on the 186 Holden engine. Made it sound wicked.

I replaced the standard mufflers on my FJ1200 with straight-through pipes, at low revs (which was easy around town) it was quiet, until you hit the throttle, then you were constantly checking the mirrors to see if there were any cops behind you.

I found a couple of pics of the old girl.

A view from the front ...


Then a view inside the engine bay where you can see the air filter that I cable-tied in place so I could get that lovely sound!

That is beautiful. I bet it did put a smile on your dial. I always wanted one of them with some nice breathing mods just to cruise around in and give it a squirt here and there. Must have been a bugger to work on though! FJ1200 too! You are a man of taste Old Tony.

Thank you all for all replies...
I might wait till this muffler kicks the bucket and when it needs replacing I think ill try a Hot dog. ..
just a quick question though...
if I was to drill a single hole through the centre of the DPF honey comb... would this inflict any negatives such as codes or faults ?? And would it help with the flow restrictions??

Sorry guys... if was to replace orig muffler with a Hotdog... would this be legal to do?

cheers

i have no idea what can happen if you drill the DPF but just to be the voice of reason here, DPF's cost around 1.000 us dollars, they have sensors on them, being monitored by the ecu constantly and they they regen, ecu spills diesel in them aircon kicks on (on some models) and its a serious equipment that i wouldnt mess with. if you want to get rid of it find a GOOD remappper so he can delete it from your system. expect to be big money and instantly makes your car illegal (altering emissions etc)

about the muffler, i dont know australian laws but around here you can only replace the muffler with something that doesnt raise manufacturers dB emmision. for example stock d40 has 72 dB at 2,000k rpms. you will need something that doesnt go beyond that. but its just the law around here not sure about Australia.

Stelianos is right on the money, even in Australia. Any change to any emission control (particulate, gas or audible emissions) is illegal. However, the chance of getting pinged for it - if it's not unreasonably loud - is almost zero. If it's puffing clouds of smoke then expect someone to say something, but you don't want it doing that anyway!

I've heard of a few people performing modifications to their DPF using some delicate tools (star picket and a 2Kg sledge) but I can't remember how they faired afterwards.

The DPF is a funny bugger - the sensors before and after are reading the pressure in the exhaust. When the sensor in the front (closer to the engine) shows a higher pressure, it means the DPF is restricting flow more, meaning the DPF requires cleaning. There have been a few occasions where people have used DPF delete pipes and the original sensors only to find that they start reading massive differential pressures and the car starts blowing clouds of white. This has almost always required a reinstallation of the DPF and a regen - and is the reason why auggie provides replacement sensors which don't have this problem.

As Stelianos also says, you CAN get someone to remove the DPF section of the ECU function but there are possible issues with that too (not legal-wise - most of what we're discussing here isn't technically legal anyway). If Nissan - for whatever reason - get the car back in their workshop, there's every chance that they'll "software update" the ECU and you'll lose the ECU mod. If you DO go through a DPF delete + ECU modification, don't take the car back to Nissan!

Thanks heaps guys....
ill leave it the way its meant to be.