is there any difference between a diesel and petrol exhaust system

[hough]

Hey can any help as the thread states is there a difference between a diesel and petrol exhaust system also are the cat the same?

IV tried finding this out on the internet but can't seem to find an answer

 

[pgarner]

diesels are generally a slightly larger bore than their petrol counterparts. and modern ones will have a particle filter fitted but thats the only difference normally.

there isnt really many off the shelf exhausts for my car but i could fit the one for the earlier turbo petrol.

 

[bigbadjoe]

Yes. Diesel's dont have a cat fitted in them. A lot of diesels these days have turbo's, so the link pipe and exhaust manifold will probably be different as well.

 

[hough]

what about cats are they universal?

 

[bigbadjoe]

No, you don't have Cats on a diesel. :blink1:

 

[hough]

<p>ok im not disagreeing but if no cats on a diesel why is it when looking for a new stainless exhaust I was quoted from the cats back???</p>

 

[HDi fun]

Diesels DO have cats. Universally. They are two way unregulated ones as opposed to closed loop lambda controlled three way ones fitted to petrol cars.

 

[hough]

thanks hdi so can you get performance cats for a diesel?

 

[HDi fun]

I would imagine so, but in truth I've never really researched it. Most diesels are pretty free flowing anyway and you haven't got the issue of dealing with high revs. There are very few diesels which go beyond 5000-5500rpm and to be honest the party's generally over much lower than that, even if the engine will rev that far.

However, that party starts at a bout 1200rpm

 

[bigbadjoe]

Diesels DO have cats. Universally. They are two way unregulated ones as opposed to closed loop lambda controlled three way ones fitted to petrol cars.

Errr, they are not technically catalistic converters though are they. They are free through with an expantion to collect unburned oil and the likes.

Try telling the scrappy your diesel has a cat on the back for the extra £50 scrap value and they will laugh you off the yard!! :toung:

 

[pgarner]

Diesels do have cataltic converter but they are technically not needed as there is no emission testing on diesels.
as for performance cats for diesels again theres not really any point. you could just whip it out but the issue comes from the new MOT means it would fail if it wasnt visably there

 

[pgarner]

BBJ are you not thinking about the DPF rather than a cat. its there to collect the soot and smoke.


as for asking a scrappy most would laugh you off even if it was a petrol you asked for

 

[hough]

ok this is why im getting confussed look at this website

https://www.blueflameperformance.co...3mm-downpipe-and-100-cell-motorsport-cat.html

Its one of the exhaust systems I was looking at for my vw bora

 

[pgarner]

yeah you will get performance cats.
your bora is also per DPF so your clear on that.
TBH if you can get your downpipe off and the guts taken out your cat youd save a fortune as its a 2.5" anyway. a 3" would be an advantage if your going to hybrid of big turbo but for stage 1 remaps then youll be fine with the standard one.

cat back again it flows well enough and youll not get any real noticible gain from changing it

 

[hough]

thanks I was looking at a hybrid turbo but for now I was just gona make my own stainless exhaust using 2.5" tube maybe upgrade the air intake then a remap and see how the car feels and if still not happy then maybe look at the bigger turbo lol

 

[T9 man]

Sounds like a plan buddy

 

[hough]

just got to make up my mind on if im gona use a resonator and what size centre and rear box im gona go for

 

[HDi fun]

Errr, they are not technically catalistic converters though are they. They are free through with an expantion to collect unburned oil and the likes.

Try telling the scrappy your diesel has a cat on the back for the extra £50 scrap value and they will laugh you off the yard!! :toung:

Wrong - they are two way oxidation catalytic converters operating in unregulated mode. They still employ precious metals such as Rhodium and platinum. The operation is much the same as lambda regulated three way converters in petrol cars other than oxides of nitrogen are not considered nor controlled.

Think about the valency of nitrogen as an element. Big atoms with no 'free' electrons in the outermost shell. How would you bond it to anything else??? Now consider that air is 80% nitrogen anyway. Further, derv engines are without a throttle so there's always free flow of air (remember it's 80% nitrogen) regardless of the driving situation.

Bolting an extra O2 atom to a CO molecule is what CATS do. Completion of combustion basically and it works equally well for derv and gas

Regardless of this the biggest task all cats perform is forcing hydrocarbons to complete their burning - simply by increasing the temperature of the exhaust gases

 

[HDi fun]

just got to make up my mind on if im gona use a resonator and what size centre and rear box im gona go for

Resonators are used to reduce exhaust noise

 

[hough]

will definitely use a resonator on my new system just trying to work out what size and length centre and back box to use and whether or not to go for a single ir dual pipe exit???

 

[HDi fun]

What car are you fitting to mate?

 

[hough]

you will most prob laugh but its for my vw bora 1.9 tdi (150bhp)

 

[HDi fun]

Not at all. The PD 150 engine is a good one and responds superbly to an ECU remap alone. Over 200bhp and over 300lbft is easy.

PGarner is the resident VW Audi specialist. Well worth grabbing his attention on this one. You'll get the definitive answer on whether an exhaust upgrade is worthwhile.