Exhaust questions.

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Glen
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Exhaust questions.

Post by Glen »

I have searched a little through here, but have not found an answer, so I am posting a new thread.

I am hoping to gain very mild increases in performance and sound from my exhaust, but I am confused about which of the many choices will give me what I am looking for.
Choice #1...Have the stock manifold gasket matched to improve flow.
Choice #2...Swap stock American manifold for a European manifold.
Choice #3...swap to an aftermarket stainless header...and if so, which manufacturer?

I live in a state that requires no emissions testing, and removing the catalytic converters and using straight pipes would be legal on a car of this age.

I do NOT want an obnoxiously loud car, just some mild gains.

Thank you, each and all, for your input.
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Bhart
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Re: Exhaust questions.

Post by Bhart »

I bought the Ireland Engineering, cat back exhaust for my '87 M6. Brought it to my favourite exhaust shop and went underneath with the shop owner. He immediately saw troubles with the build quality of the intermediate muffler - no dip to clear the rear axle and pipe ends were bent askew. After a lot of measuring, cutting and a lot of trial & error fitting, he deemed it 'junk'. Seeing as I needed to get this car home with some semblance of an exhaust, he suggested we fit the rear section and he'd make up the flanged pipes between the cats and the rear muffler. A short time later I fired up the car and was pleased with the sound at idle. Driving home, I was also pleased with the sound around town and then at speed - not too loud and no droning.

My suggestion; rear IE muffler and custom pipe in between that and the cat. Simple, relatively cheap and a nice bit of straight six sound.
01/1987 M6

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Brucey
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Re: Exhaust questions.

Post by Brucey »

you need to say what car you have, and what engine is fitted.

cheers
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Glen
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Re: Exhaust questions.

Post by Glen »

I have a 1985 635csi with the 3.5Image
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86_6series
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Re: Exhaust questions.

Post by 86_6series »

4 or 5 years ago I installed the Ireland Cat back.
It's the best exhaust I've had on this car that I owned for 31yrs.
Great sound , all stainless, made in China but for $500 it's worth it'
very good quality. I didn't think it was junk at all.

Sorry to hear it didn't work for you.
I just rebuilt my 6 and went with Ireland headers ceramic coated
and they fit like a glove. Just my experience with Ireland products.

In the past I purchased Ireland performance stuff and was never disappointed.
86-635CSi
96-MB C220 SOLD
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Bhart
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Re: Exhaust questions.

Post by Bhart »

86_6series wrote: Sun Sep 22, 2019 11:25 pm 4 or 5 years ago I installed the Ireland Cat back.
It's the best exhaust I've had on this car that I owned for 31yrs.
Great sound , all stainless, made in China but for $500 it's worth it'
very good quality. I didn't think it was junk at all.

Sorry to hear it didn't work for you.
I just rebuilt my 6 and went with Ireland headers ceramic coated
and they fit like a glove. Just my experience with Ireland products.

In the past I purchased Ireland performance stuff and was never disappointed.
Yes, the low price attracted me too but there must be some serious build quality issues between what you purchased and what I received.

There were two specific issues to the center muffler; 1) the flanges that bolted to the cat were not in the same plane as each other meaning that doubling or tripling up of exhaust gaskets would be required to seal the joints properly. 2) the tail pipes that connect the center can to the rear muffler had approximately 1/4" clearance between the two pipes - not wide enough to mate up with the rear muffler inlet pipes. Cutting the mounting strap actually made the two pipes to sit closer together, any attempt to pull them apart for proper spacing was futile.

This was my experience with the IE exhaust system. I do want to repeat, I am happy using just the rear section alone.
01/1987 M6

past Bimmers;
1970 2800CS
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Brucey
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Re: Exhaust questions.

Post by Brucey »

Bhart wrote: Tue Sep 24, 2019 9:18 pm
There were two specific issues to the center muffler; 1) the flanges that bolted to the cat were not in the same plane as each other meaning that doubling or tripling up of exhaust gaskets would be required to seal the joints properly.....

IME in BMW exhaust pipes staggered flanges is quite normal. To give a fitting tolerance one or both joints is usually a sliding joint. Thus it isn't necessary to have both flanges in one plane or anything finicky like that. However it may not be obvious (esp if you are trying to use old parts) that the seal rings are a sliding fit on the pipes in some cases. If you don't realise this then the whole exhaust system can be bent like a dog's hind leg when it needn't be, and of course this will make it seem like the rear of the system doesn't fit at all well, if there is an assembly error near the front of the system.

The reason why there wasn't a dip to clear the rear axle may be because this isn't necessary; IIRC OEM pipes have no such dip; they are just set so that the lower edge of the pipes are flush with the bottom of the boxes; a 'dip' would just be part of the exhaust that hangs down further than the rest and would be the first bit to clout the road and get damaged. Again it is not always obvious (what with crud and rust under the car) but the hanger brackets for the centre box are height adjustable, so you can fine-tune the fit.

If there were problems fitting the rear box to the rest of the system then this would normally have been picked up when the system is trial assembled, on the floor, before you try and assemble the entire thing under the car. IME it is very unwise to just assume that exhaust parts fit one another perfectly without trying it first; as you have found it can make for a lot of (possibly quite needless) work.

If your favourite exhaust shop is not familiar with these cars and these exhaust systems, they could easily have screwed the installation up; they are not fitted in the same way as a lots of other exhaust systems are.

FWIW I've got a Fritz's exhaust (including manifold) on my 635CSi and it is a bit noisy (so not OEM sound or anything close) but it has been pretty good otherwise (on the car for about fifteen years now with no problems). It is about half the weight of a stock exhaust/manifold, too. However the one I have is designed for RHD, and it isn't the cheapest option; probably you could do better local to you.

cheers
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Bhart
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Re: Exhaust questions.

Post by Bhart »

Let me clarify on the flanges - The fixed flange was proud of the sliding, negating any tolerance adjustment in the sliding joint. The joints were not on the same plane horizontally and, within the horizontal plane, one flange (the fixed one) was not square to the plane meaning the flange would not bolt up to the existing cat flange without a 3/8" gap on one side. Having the fixed flange and slide-in rear did not allow for any adjustment of the angle between pipes

Yes, the system was laid out on the floor to check fitment and that's where the discrepancy between the spacing of the outlet pipes of the center muffler and inlet of the rear was discovered. If one pipe of the center muffler was lined up with the matching pipe of the rear can, the second pipe of the center section was more than 1 inch overlapped on the pipe it was expected to mate with.

These problems together made the center pipe useless in a practical sense and rebuilding the center section would be impractical. My favourite exhaust shop is quite familiar with custom and specialist work and has yet to 'screw up' any work I have ever brought them nor any other specialized work acquaintances have had done with them. I was merely commenting on my experience with the Ireland exhaust system I had purchased.
01/1987 M6

past Bimmers;
1970 2800CS
1988 325is
1985 325E
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86_6series
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Re: Exhaust questions.

Post by 86_6series »

Don't want to exhaust (pun intended) this subject but I just noticed
were talking about an 87 M. the cat back from Ireland is not for an M car
and especially after 6/87 for any 6

http://www.iemotorsport.com/bmw/item/e28catback.html
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Brucey
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Re: Exhaust questions.

Post by Brucey »

as pointed out above maybe you tried to fit the wrong thing anyway.

But the flanges between the down pipes and the front box and then onto the centre box are meant to be staggered; they don't 'bolt up' with conventional gaskets they use specific seal rings which allow a small amount of articulation of the exhaust parts, and make the exact flange angle almost irrelevant.

Image

if you don't have seal ring items #5 and #6 above, and know how to use them, then the correct parts apparently 'don't fit very well' and any exhaust install is bound to be a proper bodge job. Similar parts are not used on that many other cars.

cheers
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LarryM
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Re: Exhaust questions.

Post by LarryM »

Glen,

If cost isn't real critical take a look at Supersprint. A bit pricey but high quality and excellent fit.

From Supersprint's website:
https://www.supersprint.com/ww-en/super ... csi-3.aspx

The items you'd need are P/N 781523 (resonator section) which bolts up directly to the stock cat converter, and either 781506 or 781536 (muffler, with your choice of tip style). A cat-back system like this won't make much difference with a stock engine, but it will give you a nice refined sound that's not too loud.

If you want a true free-flow exhaust system, you can purchase a set of larger (50mm dia.) Euro downpipes and then replace the cat with P/N 781502 or 781512 (resonator or straight pipes). With this setup you WILL notice a difference in midrange and top end power. Combine it with a good performance chip and a lower diff (3.64 or 3.91) and you'll really wake up your car, making it much more fun to drive using only bolt-on parts.

Here's a good place to buy Supersprint products (watch for sales):
https://www.schmiedmann.com/
1985 635CSi
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