451 cdi exhaust system

[Duncan.e]

Having decided to replace my exhaust system with a free flowing lighter system that I'd like to make myself, Ian at Big Performance has very kindly lent me an exhaust manifold with turbo and a diesel silencer, both from a 450. These to give me an idea of what I need to make.

I have sat and pondered and drawn up a system that I think will work and then today I crawled under my car to look at the existing system, only to find my initial design won't work as I has based it on the 450 exhaust outlet from the turbo which is different to the 451 - that'll teach me to look first!! :redface:

I also noticed that there seems to be a sensor in the upstream side of the exhaust - I couldn't see one downstream, but that doesn't mean there isn't one - it's difficult to see it when crawled underneath! I didn't think that diesels used oxygen sensors. Can anyone confirm for me that's what it is and if it is the only one?

As I intend to make the system without a cat and without a particle filter, does anyone know how I fool the electronics into believing I have one fitted and that all is as it should be?

Any insights into making the exhaust also welcome!!

[bilgladstone]

Re: 451 cdi exhaust system

Subscribed.

I will be very interested to see what you come up with!

[10:45PM]

Re: 451 cdi exhaust system

there is only one O2 sensor on the diesel, why not just transfer it over to your new pipe :smile:

[Duncan.e]

Re: 451 cdi exhaust system

Subscribed.

I will be very interested to see what you come up with!

I would be very grateful to hear the story of the development of your system, to understand your 'failures' and especially the one labelled 3 in your photo of 'rejects'.

The standard system on the 451 is much heavier than the 450 due to having a particle filter and I'm aiming to have a lightweight, cat free and particle filter free system to give me a faster spool up and more power / better economy

The car has already been re-mapped, but Ian at Big Performance will check the map and optimise it once the exhaust is sorted.

:thanx:

[bilgladstone]

Re: 451 cdi exhaust system

Duncan, the exhaust labeled 3 in the photo is a silencer from a large-displacement touring bike - a never-used "take-off" from a customer who bought an exhaust upgrade on his new Yamaha. A friend at a Yamaha shop rescued it for me.

We had used the smart's OEM exhaust bracket - the one that bolts to the underside of the transmission housing - welded to a wide wrap-around strap - that's the shiny bit you see encircling the canister.

On the manifold end, a simple curved pipe; and we were lucky enough to find a universal bolt-on flange that fit the canister's inlet end.

Unlike the Blindschleiche cans shown, this did not have a cat'.

The little cdi's vibration was the death of all these kits. The bracket welds would fail repeatedly, and the rigid downpipe would break. All three were too heavy, and their weight increased the amplitude of the vibrations. Plus, this bike can was too loud!

So now I have gone in a completely different direction incorporating a mini-catalytic converter, a spiral baffle inside the straight pipe, then a resonator at the end. This is very light weight and emissions-compliant (in our jurisdiction at least)

Also, we have wrapped the whole assembly with heat-insulating tape in order to maintain temperature and density efficiency for the cat' and the scavenging spiral insert. The tape also mitigates some of the higher exhaust notes, tuning the sound down to (what I think of as) a nice strong, but "neighbourhood-friendly" tone.

Also note that the down-pipe is flexible, braided stainless steel, and the hanging bracket at the tail end is vibration-isolating, with a length of reinforced rubber near the end. This accommodates the engine vibration without tearing apart welds.

I am very happy with this version and don't foresee any mechanical problems with it. Super light, efficient, emissions compliant, sounds great, and once I get the valance back on, stealthy as well. Well, except for the blingy end bit Thinking I might raise it a little and poke it out a cut-out in the valance...

Regards,
Bil in British Columbia

thumbnails are clickable

[Duncan.e]

Re: 451 cdi exhaust system

Bil,

Thanks for the insight into the problems you've found - and overcome - with your exhaust system! I must admit that although I'm aware of the engine vibration, I hadn't thought about the implications to the design!

I like the idea of using a spiral baffle 'silencer', and am thinking of making one of these myself, but longer than yours as I'm not going to be using a cat. Can I ask what diameter the tubes are in your spiral design? I'm guessing that the outer pipe is around two inches and perhaps the inner pipe is 3/4 inch?

Not knowing a thing about these pipes, apart from the pictures I've seen of them, any suggestions as to how long I should make it? Yours appears to be about 12" long, so I'm guessing I should make it maybe 18"....

Once again, thanks for your input!

Best

Duncan

:thanx: :thanx: :thanx:

[Duncan.e]

Re: 451 cdi exhaust system

Bil,

Any idea when you'll get the second video up? It will be interesting to compare the sound of the 'raw' system to as it is now, all wrapped up.... :silvertri

[bilgladstone]

Re: 451 cdi exhaust system

I may be able to do the follow-up video later today (it's 3am Pacific here right now). My baffle is only 8 inches, inside a length of pipe that is 2-1/8" I.D. You'll have to try to scale the diameter of the inner pipe, as it was just a bit of end cut that was laying about.

The spiral elements, I made by cutting a few 2" heavy flat-washers in half then bending to fit and weld on. Notice in the Moroso picture that it is not a continuous spiral.

Absolutely no need to go longer than 12-14" in my opinion. I would simply run clear pipe first and then add the spiral at the very end.

Another choice (I would do this if I ever make another along this line) would be to buy a Moroso spiral muffler in 2" inlet size and just weld it on. Fabricating the spirals yourself is a real PITA. They need to fit fair tightly but not so tightly that they can rattle against the pipe.

Here's a look at a Moroso - you could add a 2" decibel cap if you like, to tune the noise down a bit. Also a peek up the workings of my spiral when I had it in a different configuration. The oily deposit is not from the pipe - I had a wee oily leak from above that dripped down on the end.

Good luck!
Bil

P.S. I don't know why, but all the manufactured spirals I've seen flow anti-clockwise. I just copied that, as I reckon somebody must think it makes a difference? Dunno.... would they go clockwise "down under?"

[Duncan.e]

Re: 451 cdi exhaust system

I may be able to do the follow-up video later today (it's 3am Pacific here right now). My baffle is only 8 inches, inside a length of pipe that is 2-1/8" I.D. You'll have to try to scale the diameter of the inner pipe, as it was just a bit of end cut that was laying about.

The spiral elements, I made by cutting a few 2" heavy flat-washers in half then bending to fit and weld on. Notice in the Moroso picture that it is not a continuous spiral.

Absolutely no need to go longer than 12-14" in my opinion. I would simply run clear pipe first and then add the spiral at the very end.

Another choice (I would do this if I ever make another along this line) would be to buy a Moroso spiral muffler in 2" inlet size and just weld it on. Fabricating the spirals yourself is a real PITA. They need to fit fair tightly but not so tightly that they can rattle against the pipe.

Here's a look at a Moroso - you could add a 2" decibel cap if you like, to tune the noise down a bit. Also a peek up the workings of my spiral when I had it in a different configuration. The oily deposit is not from the pipe - I had a wee oily leak from above that dripped down on the end.

Good luck!
Bil

P.S. I don't know why, but all the manufactured spirals I've seen flow anti-clockwise. I just copied that, as I reckon somebody must think it makes a difference? Dunno.... would they go clockwise "down under?"

Thanks for the info! What on earth are you doing up still at 3am!

I had planned on using washers to make the spirals, but had no idea what size pipes to use. 2" diameter washers sound good and it looks like you used half inch for the inner pipe. It all looks good - and doable! I think I have some polished stainless steel pipe about the right diameter for the outer piece! I can almost certainly get hold of ss washers and another piece of small bore pipe, so it's looking good!!

I'd prefer to make my own, rather than buying one - better sense of achievement!!

Interesting that they go anti-clockwise....

One more question, what bore pipe have you used between the turbo and the cat? The turbine outlet is 33mm diameter and I'm thinking of using 1.5" pipe as it's the nearest size to the turbo outlet without going smaller....

:thanx::thanx::thanx::thanx:

Duncan

[bilgladstone]

Re: 451 cdi exhaust system

One more question, what bore pipe have you used between the turbo and the cat?

The cat is 2" bore. I increased straight to 2" from the manifold with 2" s/s flex. In looking at the OEM (450) exhaust, there is a chamber ahead of the matrix itself - maybe 1 litre. Again, reasoning that perhaps a volume chamber was an engineered feature with some purpose I had not fathomed (perhaps to reduce velocity or buffer gas pressure waves?), the larger bore pipe ahead of the cat might serve a similar purpose, allowing a slightly greater volume of gas ahead of the cat.

I think though, that the outlet and cat configuration on your 451 might be quite different than my 450.

/B

[Duncan.e]

Re: 451 cdi exhaust system

The cat is 2" bore. I increased straight to 2" from the manifold with 2" s/s flex. In looking at the OEM (450) exhaust, there is a chamber ahead of the matrix itself - maybe 1 litre. Again, reasoning that perhaps a volume chamber was an engineered feature with some purpose I had not fathomed (perhaps to reduce velocity or buffer gas pressure waves?), the larger bore pipe ahead of the cat might serve a similar purpose, allowing a slightly greater volume of gas ahead of the cat.

I think though, that the outlet and cat configuration on your 451 might be quite different than my 450.

/B

It is! The exhaust system on my 451 bolts straight to the turbo flange, whereas yours has an outlet that tapers down to 33mm bore and with a radiused taper flange fit to the exhaust system.

Mine has a lambda sensor fitted as the pipe turns through 90° then through a short length of flexible pipe and into the main box which includes the cat and particle filter. The exhaust is not mounted to the engine, but has exhaust hangers on either side of the car, so is very different to the standard set up on yours.

I have just had a quick look for Moroso spiral mufflers and it seems they start at 2 1/2" bore...

As I'm not using a cat, I'm thinking of using 2" bore pipe throughout the system....

:thanx::thanx:

[PaulG]

Re: 451 cdi exhaust system

Duncan, i have an evil twin exhaust for sale if your interested c/w modified rear vallance. it was only on the car for a couple of months before i p/x car for the brabus. its the one with the single oval outlet and was fitted to my 2008 passion turbo 451. take £100 for it.

[Duncan.e]

Re: 451 cdi exhaust system

Duncan, i have an evil twin exhaust for sale if your interested c/w modified rear vallance. it was only on the car for a couple of months before i p/x car for the brabus. its the one with the single oval outlet and was fitted to my 2008 passion turbo 451. take £100 for it.

Thanks, but no thanks.

This is a project I want to do myself. I reckon I can build my system a lot cheaper than that too....

:thanx:

[bilgladstone]

Re: 451 cdi exhaust system

FYI, the materials cost on mine was about £180 including the cat', heat wrap, hangers, chrome tip etc..

[Duncan.e]

Re: 451 cdi exhaust system

FYI, the materials cost on mine was about £180 including the cat', heat wrap, hangers, chrome tip etc..

Without the cat it should be a little less than half that I reckon - or at least I'm hoping!

:thanx: