SAAB 9-3 - Diesel exhaust back box on a petrol car

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Mon 25 Nov 2013 09:04
SAAB 9-3 - Diesel exhaust back box on a petrol car - rubble2

Hi,

I have the above car with a 2.0 petrol engine, I have been looking round for a replacement back box which has twin tailpipes which exit the box through a cutout in the bumper ( the existing backbox has twin exit pipes which bend down to the road).

I have come across one which is a Saab original part but it is designed for the diesel engine, the physical size and fixings are identical so it will be a direct fit but I wonder what (if anything) would be the problems encountered in using a diesel backbox on a petrol engine? I wasn't aware that there was likely to be any difference between the two.

Thanks

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Mon 25 Nov 2013 14:06
SAAB 9-3 - Diesel exhaust back box on a petrol car - jc2

Should be none! Minor internals possibly but you don't need to pass noise tests.

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Mon 25 Nov 2013 15:21
SAAB 9-3 - Diesel exhaust back box on a petrol car - rubble2

Thanks,

I couldn't really see any problem but appreciate you confirming it

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Mon 25 Nov 2013 17:56
SAAB 9-3 - Diesel exhaust back box on a petrol car - Cyd

whilst the mounting points will probably be the same (common body), the pipe diameters might be different.

Try Neo Brothers, they'll know what'll fit and what won't.

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Tue 26 Nov 2013 12:39
SAAB 9-3 - Diesel exhaust back box on a petrol car - Peter.N.

It needs to have the same internal diameter as mentioned although if its bigger it shouldn't hurt.

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Tue 26 Nov 2013 14:38
SAAB 9-3 - Diesel exhaust back box on a petrol car - rubble2

It needs to have the same internal diameter as mentioned although if its bigger it shouldn't hurt.

From what I have managed to understand from other sources, diesel exhausts are more 'Free flowing' than petrol so I am guessing that this will not cause any problems.

I have now found people who are using/have used the petrol version back box on diesel cars without any issue so I think I will give it a go. Not too worried about small differences in tube diameters as these can be overcome with sleeving or an adaptor

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Tue 26 Nov 2013 14:52
SAAB 9-3 - Diesel exhaust back box on a petrol car - bathtub tom

>> diesel exhausts are more 'Free flowing' than petrol

Really? You may have stumbled upon something that could start a trend. I wonder if they'd be less 'noise suppressing' as a result?

Just looked up applications for my car and found diesel exhausts cost nearly twice as much as petrol for the same vehicle. I guess there must be a reason why............................

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Tue 26 Nov 2013 15:52
SAAB 9-3 - Diesel exhaust back box on a petrol car - gordonbennet

Just looked up applications for my car and found diesel exhausts cost nearly twice as much as petrol for the same vehicle. I guess there must be a reason why............................

I wonder if they're made of thicker steel and with stronger fittings to cope with the increased vibration, certainly Diesel exhausts last longer in normal use in my experience.

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Tue 26 Nov 2013 17:09
SAAB 9-3 - Diesel exhaust back box on a petrol car - Andrew-T

< Diesel exhausts last longer in normal use in my experience. >

I thought this was mainly because they get waterproofed by a thick layer of soot inside?

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Tue 26 Nov 2013 17:16
SAAB 9-3 - Diesel exhaust back box on a petrol car - gordonbennet

I thought this was mainly because they get waterproofed by a thick layer of soot inside?

no no no, didn't you know Diesels are all fluffy wuffy now, apparently the air coming out is cleaner than that which went in..:-))

Think you're probably on the button though, but most exhaust failures i now see come from outside corrosion, mostly salt damage.

The tail section of my MB is getting thin again just before the rear silencer where it takes the road and salt debris, i'm definately going to get a stainless rear section this time...will be my first stainless exhaust experiment.

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Tue 26 Nov 2013 23:12
SAAB 9-3 - Diesel exhaust back box on a petrol car - Andrew-T

< Diesel exhausts last longer in normal use in my experience. >

I thought this was mainly because they get waterproofed by a thick layer of soot inside?

My personal experience with diesel exhausts is that I have never had to renew one. 1991H Pug 205 still going at 10 years and 80K miles; 1999T Pug 306 likewise; and current Pug 207 well into its sixth year. None of them of course had/has a DPF ....

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Tue 26 Nov 2013 17:12
SAAB 9-3 - Diesel exhaust back box on a petrol car - Andrew-T

.... diesel exhausts cost nearly twice as much as petrol for the same vehicle. I guess there must be a reason why....

I don't see why diesel cars would command a status premium, so I guess the exhaust may need more baffling to suppress the louder bangs a diesel makes ?

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Wed 27 Nov 2013 09:02
SAAB 9-3 - Diesel exhaust back box on a petrol car - RT

Do exhausts need replacing these days? The last car I had which needed an exhaust was a '95 Cavalier - all my subsequent cars had exhausts made so well they'd easily outlast the cars.

I know it depends on usage - short journeys where the engine/exhaust doesn't heat up fully, allowing moisture to remain inside the exhaust is a killer - diesels are worse than petrols because of their longer warm-up phase particular under light throttle conditions.

Edited by RT on 27/11/2013 at 09:02

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Wed 27 Nov 2013 10:09
SAAB 9-3 - Diesel exhaust back box on a petrol car - Andrew-T

- all my subsequent cars had exhausts made so well they'd easily outlast the cars.

That's partly because the cars have little value after 10 years and are mistakenly thrown away in the prime of life.

Edited by Andrew-T on 27/11/2013 at 10:10

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