craigdiver
|
| posted on 30/4/17 at 08:17 PM |
|
|
6-cylinder exhaust design
I have just read the contents of the internet on exhaust systems but still don't have a clue!
Engine is the BMW dual-vanos 2.5 6-cylinder.
My initial thoughts are that I want to bring the 6 pipes (1 1/2" ) straight out the side of the car below the top rail, then each one 90 degree
bend down then joining into a main horizontal 2" pipe using 45 degree bends. This would be TIG welded and then chromed. Then into a cat, a
silencer and finally tail pipe.
The other issue is that the engine currently has four oxygen sensors, two before cat and two after (original exhaust was 6-2-1). The two after will be
deleted when ECU reprogrammed but what can I do with 6 individual collectors and two oxygen sensors? (Can I just put them in two of the 6 pipes or
both in the single 2" pipe next to each other before the cat?
I would really like to have the 6 pipes on show and realise I might loose a little power but anybody understand exhaust systems and can comment?
Cheers
Craig
[Edited on 30/4/17 by craigdiver]
[Edited on 30/4/17 by craigdiver]
If it ain't broken, fix it anyway (just because).
Building - BMW powered Haynes Roadster/442E hybrid.
Volvo C30 T5 Polestar
|
|
|
|
|
rodgling
|
| posted on 30/4/17 at 08:33 PM |
|
|
I'd think you need a 6-2-1 system to get the lambdas to work properly? This is what I have, which does the job. I do have a second silencer
under the fuel tank, as I can't get it quiet enough for track otherwise.
|
|
|
craigdiver
|
| posted on 30/4/17 at 08:41 PM |
|
|
quote:
Originally posted by rodgling
I'd think you need a 6-2-1 system to get the lambdas to work properly? This is what I have, which does the job. I do have a second silencer
under the fuel tank, as I can't get it quiet enough for track otherwise.
I could still bring the 6 pipes out and into two horizontal (where lambdas would be mounted) then into a 'Y' to a single pipe, or keep it
as two horizontals but would mean having to buy 2 x cats and 2 x silencers but would look good!
If it ain't broken, fix it anyway (just because).
Building - BMW powered Haynes Roadster/442E hybrid.
Volvo C30 T5 Polestar
|
|
|
ettore bugatti
|
| posted on 30/4/17 at 09:39 PM |
|
|
Could you not place the 2x pre sensors opposite each other and the 2x post as well, but still relative correct position to the cat?
You might need a big cat to cope with the 6x exhausts.
|
|
|
craigdiver
|
| posted on 1/5/17 at 08:13 AM |
|
|
quote:
Originally posted by ettore bugatti
Could you not place the 2x pre sensors opposite each other and the 2x post as well, but still relative correct position to the cat?
You might need a big cat to cope with the 6x exhausts.
The original cats were not too big, looking at the original exhaust again might need to make exhaust 6-2
If it ain't broken, fix it anyway (just because).
Building - BMW powered Haynes Roadster/442E hybrid.
Volvo C30 T5 Polestar
|
|
|
SteveWallace
|
| posted on 1/5/17 at 08:25 AM |
|
|
However you make your exhaust look, if you keep the BMW ECU then you will need to preserve the 6:2:1 configuration and the two pre-cat lambda sensors.
The ECU interprets each sensor as being from a specific set of three cylinders and the engine will run rough if you mix them up. If your lambda
sensors are outside of the engine bay though, make sure that they are positioned so as not to fail the IVA radius test.
A single Magnaflow 200 cell sports cat should be sufficient for your engine, there are a couple of cars on here including mine that have 2.8 straight
6 BMW engines that have passed IVA with these.
"I know every nut and bolt and cog in that car, I built it myself" - The Prisoner, 1967
|
|
|
craigdiver
|
| posted on 1/5/17 at 08:36 AM |
|
|
quote:
Originally posted by SteveWallace
However you make your exhaust look, if you keep the BMW ECU then you will need to preserve the 6:2:1 configuration and the two pre-cat lambda sensors.
The ECU interprets each sensor as being from a specific set of three cylinders and the engine will run rough if you mix them up. If your lambda
sensors are outside of the engine bay though, make sure that they are positioned so as not to fail the IVA radius test.
A single Magnaflow 200 cell sports cat should be sufficient for your engine, there are a couple of cars on here including mine that have 2.8 straight
6 BMW engines that have passed IVA with these.
Thanks Steve, going to have the EWS delete, along with removal of the post-cat lambdas and the air pump. is there a photo of your exhaust system on
the forum? And, does it sound good? :-)
If it ain't broken, fix it anyway (just because).
Building - BMW powered Haynes Roadster/442E hybrid.
Volvo C30 T5 Polestar
|
|
|
SteveWallace
|
| posted on 1/5/17 at 08:48 AM |
|
|
This is probably the best photo that I have, but have a look in my photo archive as well. I went for the understated approach of only having two
pipes coming out of the engine bay. Yes, it sounds great, but it is loud and I was right on the edge of the IVA noise test, so be careful with choice
of silencer or use a DB killer for the test.
I also have a de-cat pipe, but I prefer the sound with the cat in place.
If your going to have the ECU remapped then have the limp home mode engine map replaced with the same map that you use for normal running as your
final build will have so many sensors missing (e.g. ABS) that the ECU is almost bound to go into limp home. By changing the map it will make no
difference.
 
Description
"I know every nut and bolt and cog in that car, I built it myself" - The Prisoner, 1967
|
|
|
Nickp
|
| posted on 1/5/17 at 09:47 AM |
|
|
I used a pair of manifolds similar to these-
DIRENZA STAINLESS STEEL EXHAUST MANIFOLDS FOR BMW 3 SERIES E36 320 323 325 328
I turned the rear one upside down and brought it over the top rail then joined them at the side of the car before the cat.
|
|
|
craigdiver
|
| posted on 1/5/17 at 11:25 AM |
|
|
quote:
Originally posted by SteveWallace
This is probably the best photo that I have, but have a look in my photo archive as well. I went for the understated approach of only having two
pipes coming out of the engine bay. Yes, it sounds great, but it is loud and I was right on the edge of the IVA noise test, so be careful with choice
of silencer or use a DB killer for the test.
I also have a de-cat pipe, but I prefer the sound with the cat in place.
If your going to have the ECU remapped then have the limp home mode engine map replaced with the same map that you use for normal running as your
final build will have so many sensors missing (e.g. ABS) that the ECU is almost bound to go into limp home. By changing the map it will make no
difference.
Description
Limp mode will be gone, great advice, cheers
If it ain't broken, fix it anyway (just because).
Building - BMW powered Haynes Roadster/442E hybrid.
Volvo C30 T5 Polestar
|
|
|
Nickp
|
| posted on 1/5/17 at 12:10 PM |
|
|
quote:
Originally posted by SteveWallace
This is probably the best photo that I have, but have a look in my photo archive as well. I went for the understated approach of only having two
pipes coming out of the engine bay. Yes, it sounds great, but it is loud and I was right on the edge of the IVA noise test, so be careful with choice
of silencer or use a DB killer for the test.
Description
Mine sneaked through the noise test at 97dB IIRC, using this silencer-
https://profusionexhausts.com/silencers/round/6-inch-152-mm/2-50-inch-6-x-6-round-27-inch-polished-stainless-steel-profusion-universal-exhaust-812640.
html
|
|
|
Volvorsport
|
| posted on 1/5/17 at 02:23 PM |
|
|
I don't see why you couldn't do a 6-1 manifold
www.dbsmotorsport.co.uk
getting dirty under a bus
|
|
|
Nickp
|
| posted on 1/5/17 at 02:33 PM |
|
|
quote:
Originally posted by Volvorsport
I don't see why you couldn't do a 6-1 manifold
And where would the lambda sensors go?
|
|
|
Volvorsport
|
| posted on 1/5/17 at 02:37 PM |
|
|
In the collector
www.dbsmotorsport.co.uk
getting dirty under a bus
|
|
|
Nickp
|
| posted on 1/5/17 at 02:56 PM |
|
|
quote:
Originally posted by Volvorsport
In the collector
But they work in 2 banks of 3. One lambda sensor is used for a bank of 3 injectors.
|
|
|
Volvorsport
|
| posted on 1/5/17 at 03:20 PM |
|
|
Can the sensors and collector not remain paired ?
www.dbsmotorsport.co.uk
getting dirty under a bus
|
|
|
Nickp
|
| posted on 1/5/17 at 03:30 PM |
|
|
quote:
Originally posted by Volvorsport
Can the sensors and collector not remain paired ?
Not sure what you mean by that. The lambda sensor needs to sense the mixture in the manifold that the 3 injectors it is paired to. It won't run
right if it sees the mixture of all 6 or just 1.
|
|
|
Volvorsport
|
| posted on 1/5/17 at 03:46 PM |
|
|
Lambda only measures a portion of exhaust gas. I can see a fault occurring if the gas changed and it couldn't see any mixture change. All they
would be is further down the pipe.
www.dbsmotorsport.co.uk
getting dirty under a bus
|
|
|
Nickp
|
| posted on 1/5/17 at 03:55 PM |
|
|
It's effectively set up to run as two seperate 3cyl engines on the fuelling side. How can it accurately adjust the fueling for each of these
3cyl engines if its reading the mixture of all 6cyls?
|
|
|
Volvorsport
|
| posted on 1/5/17 at 04:10 PM |
|
|
If the lambda range was in value . Why would it be wrong ?
www.dbsmotorsport.co.uk
getting dirty under a bus
|
|
|
Nickp
|
| posted on 1/5/17 at 04:41 PM |
|
|
quote:
Originally posted by Volvorsport
If the lambda range was in value . Why would it be wrong ?
Ok, so why do they run rough if you connect them the wrong way around?
|
|
|
Volvorsport
|
| posted on 1/5/17 at 06:42 PM |
|
|
Do you swap the tail lambda at the same time?
www.dbsmotorsport.co.uk
getting dirty under a bus
|
|
|
Nickp
|
| posted on 1/5/17 at 06:48 PM |
|
|
quote:
Originally posted by Volvorsport
Do you swap the tail lambda at the same time?
Tail lambda? After the cat? Mine doesn't have those. Sounds like the later twin vanos (TU) one does but he's having that deleted along
with his remap.
|
|
|
craigdiver
|
| posted on 2/5/17 at 05:33 AM |
|
|
I think, being sensible, and wanting the lambdas under the bonnet, I will stick with the 6-2-1 configuration - probably :-o
However, the original exhaust system has two cats, might still consider bringing two exhausts horizontally along the car with 2x cats and 2x silencers
giving a 6-2 configuration. Would need to downsize pipes slightly to keep exhaust gas velocity up.
If it ain't broken, fix it anyway (just because).
Building - BMW powered Haynes Roadster/442E hybrid.
Volvo C30 T5 Polestar
|
|
|
