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I think the exhaust gases in a diesel contain some unburnt fuel which is of course a type of oil.This coats the inside of the exhaust system and offers some protection from internal corrosion.
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I've looked at this option but two banks of exhaust manifold make it an expensive option. But then they will outlast the rest of the car.
They are usually tuned to avoid making excessive noise, in the case of the V8 which can sound a little tappety at best, it acquires a deeper burbley boom noise.
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Apparently exhausts last much longer on diesels
Isn\'t it something to do with the fact they produce less condensation in the system especially on short runs compared to petrols?
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"they produce less condensation in the system especially on short runs" - this may be true, but I am convinced that the main reason is an internal coating of soot, or perhaps 'oil' as mentioned above. I have owned several diesels, none of which has needed any exhaust attention whatever.
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Exhausts use to rot out from the inside - I've read many times that this was due to the acidic properties of exhaust gases from leaded petrol, hence diesel and unleaded car exhausts now last much, much longer...
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I will not bother with cheap exhausts from the fast fits if I intend to keep the vehicle. I paid exactly £100 more for a Honda exhaust, than I would have done at a fast fit this month and the quality is so much better. Well worth it. Mikey
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Diesel exhausts last longer than petrol ones becuase: 1. diesel engines are much more thermodynamically efficient (80 vs 45%) than petrol so exhaust gases are cooler, 2. there is less water vapour produced.
Most aftermarket exhausts produced by the majors are zinc coated and last years. The non major manufacturuers cut costs so the product lasts a shorter time.
A lot depends on usage: stop start driving in a petrol car willl ensure the exhaust interior is often wet leading to corrosion. Far less impact on a diesel.
SWMBO's exhaust rear box on a 1993 Peugoet 106 diesel is original and still going strong. The down pipe and middle section were replaced after 10 and 9 years respectively. On the other hand the back box on my 1996 Rover 800 lasted 2 years.. all long journeys. (Given the awful quality of the Rover perhaps I was lucky to get 2 years:-)
I had a BMW 320i which was on its original system after 8 years with little external rust.
madf
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I've retrieved this thread in case others may be interested in the decision process that has led me to stick with a genuine OEM replacement for the exhaust system on my MB E320 Coupé.
I did consider stainless steel and I had a competitive quote from Longlife, the people (very honest and helpful) who fitted SS to my Capri. I decided against it because:
* When first discussing the Capri with Longlife, they more or less conceded that SS is intrinsically noisier, notwithstanding the fact that they use a heavy gauge. I think it's simply because the metal is thinner than mild steel and therefore more resonant.
* What on their scale was labelled a "mild sport" level of noise was intolerable for me. I tried to live with it, but after two months took up their offer of tailpipe inserts to make it quieter. It is quieter now, but it remains noisier than the original system, although comfortably so in that the slight rasp gives a sporty note consistent with the nature of the Capri.
* I spoke to Longlife about the exact configuration of an SS system on the MB, particularly the tailpipes, and they responded "To obtain a quiet note, we would usually put a single tailpipe at the rear, as opposed to the standard twin tail. We can do twin, but it does give the system slightly more of a note." This introduced an unwelcome point of conflict between noise and conforming to original design. One thing I don't want the MB to be is noisy; another is being different from the original.
* With major components such as this, I find the "keep your MB as an MB" argument pretty compelling, and my mechanic is unequivocal about it. See HJ's report (in FAQ) from the chap who got 2 million miles out of his Volvo.
I suspect that the life of the original MB system was shortened through short-trip use by its previous owner. I'm quite careful about avoiding this and would therefore hope for ten years out of the new system, if not more. If I still own the car then (quite likely, such is my fondness for it), I shan't be disappointed if another replacement is needed. I should add that the choice as been eased by a 15% discount from the MB dealer.
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Roger,
You have made the right decision. The stainless steel system that I had fitted to my Escort Mark 2 caused extra noise and vibration; I was never happy with it.
Also, it started going rusty! They are only made from very low quality stainless steel which is full of impurities, well, my one was, anyway.
I used to have a Capri, a Laser 1.6. The original exhaust system lasted about 5 years, the next one, fitted by National, blew the rear box out in 12 months and was totally shot after 2 years, when the warranty expired.
After this experience I purchased genuine Ford systems from the main dealer and fitted them myself. The best way, in my opinion!
Galaxy
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I think you're right John M. All vehicles, petrol or diesel, produce significant quantities of water vapour when they run. It's a by-product of the combustion process; the hydrogen on the fuel combines with oxygen as it burns to produce water and diesel doesn't have significantly less hydrogen than petrol. When the exhaust is hot this water comes out as vapour, but it condenses in cold systems be they petrol or diesel. So, freedom from condensed water in the exhaust is a factor of how quickly the exhaust on a particular car heats up, and from that point of view the diesel may actually be at a disadvantage. It does seem that petrol car exhaust last much longer these days and it's probably the change to unleaded that's responsible.
JS
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Horses for courses. I agree with the sentiments above when applied to my smooth and quiet V70 2.4T SE. There is no way that I'd like to ruin the level of refinement.
Like with the Capri mentioned above however, there are times when this is of less interest, and in fact, may not be wanted.
Enter SS Exhausts in Cullompton.
They made a superb system for my tuned MG Metro some years back. The quality of stainless steel was of a high order, and eight years later - when I sold the car - it still shone like new if the dirt was wiped off. Had a neat flexible joint, too, that the stock system didn't, and the quality of bending, welding, brazing, or whatever was excellent.
The exhaust was raucous when hoofing it, in a way that tuned siamese ported A-series know best (a deep off beat bellow, with transfer gear whine overlayed!), but quieter than stock in the cruise.
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Reading back what I just posted, I should stress that 'raucous' equates to the type of sound, though the level was not that much higher than stock, and being 'quieter' in the cruise was admittedly marginal. Some passengers reckoned there was no difference, though what is without doubt is that noise levels under any type of driving fell after a few thousand miles from installation.
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