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Old 08-08-2020, 11:44 AM   #1
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BMW D190 Exhaust

Came by a mid 80's BMW marine diesel D190 turbocharged 165 HP but missing the exhaust/riser. Had one fabricated at a custom exhaust shop but....the pipe coming out of the turbo is is 3 1/2" ID. The welder has stepped it down to 2 1/2" ID about 3" later. When asked why he responded "that is what most of my customers want". I was worried about back pressure created by the step down but he told me it was not an issue. So I accepted the exhaust on condition. It is a dry riser. The raw water connects to the riser at the downhill end. Any feedback on the step down welcomed. Engine is still on the stand and has not run yet. Photo is the engine before "exhaust/riser". The turbo is visible on the side.
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Old 08-08-2020, 12:18 PM   #2
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I remember when BMW entered the marine engine market (at least in the US) in the
early 80's. They seemed well designed and built.

First I would measure the I.D. of the turbo outlet if that is different to your 3.5" pipe.
If it is actually 3.5" then the 2.5" pipe will be a significant restriction.
If you can get it redone to match the turbo outlet then that is what I'd do.

Turbo engines need a low restriction exhaust to make their rated power
and to keep the EGT in the desired range.
If you haven't done it, have a bung for a pyrometer put in,
the closer to the turbo the better.
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Old 08-08-2020, 12:38 PM   #3
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I'm curious why "most customers" would want that?

I'm far from an expert but it seems people usually want more "free" exhaust not more restricted. Or... what would be the reason?
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Old 08-08-2020, 01:11 PM   #4
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Post a photo of the fabricated part. Does not look installed in the photo.
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Old 08-09-2020, 09:13 PM   #5
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Quote:
Originally Posted by Frosty View Post
I'm curious why "most customers" would want that?

I'm far from an expert but it seems people usually want more "free" exhaust not more restricted. Or... what would be the reason?
Well Frosty, that is a good question. I tell you what. I can give you the phone number and you can call them. Ask for the TIG welder John. C'mon Frosty, do you think it was possibly BS? Or how about I am a liar?
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Old 08-09-2020, 09:26 PM   #6
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Quote:
Originally Posted by Ski in NC View Post
Post a photo of the fabricated part. Does not look installed in the photo.
You are correct. As I stated - "Photo is the engine before "exhaust/riser". Here is what it now looks like.

I don't know if it has bearing but the pipe coming down from the exhaust manifold to the turbo is the same OD as the 2.5" ID exhaust I had made.
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Old 08-09-2020, 10:14 PM   #7
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Well Frosty, that is a good question. I tell you what. I can give you the phone number and you can call them. Ask for the TIG welder John. C'mon Frosty, do you think it was possibly BS? Or how about I am a liar?
I seem to have struck a nerve and I'm not sure why. You said above that the welder said that "most customers" (paraphrasing your quote of his explanation) want the reduction in size and I was interested why.

I thought you were interested too, hence starting the thread asking about it (?)
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Old 08-10-2020, 10:19 PM   #8
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Quote:
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I seem to have struck a nerve and I'm not sure why. You said above that the welder said that "most customers" (paraphrasing your quote of his explanation) want the reduction in size and I was interested why.

I thought you were interested too, hence starting the thread asking about it (?)
Well please let me tell you why. It read sarcastic, as if I were blowing smoke. Thanks anyway.
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Old 08-10-2020, 10:34 PM   #9
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Not at all. If I were the customer (you), I would actually have preferred that the fabricator say something before making it. Maybe you do, and maybe you don't want what he makes for most people. So if I'm on anyone's "side" it's yours.

But I was mostly curious as to what the TF brain trust would say about whether the reduction in size was good, bad, or indifferent. Or what they might postulate makes the majority of the fabricator's customers specifically desire the reduction?

I've been running outboards for some years now and am considering moving to an inboard boat again, and exhaust system design seems like it can be important. I've never had a turbo engine before, but it seems likely that I will end up with one if I buy a boat now, just because that's what's in most of the boats I'm interested in. Whole new area for me to learn about, which is why I clicked on your thread when you posted it.
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Old 08-10-2020, 10:48 PM   #10
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For what it’s worth, I thought Frosty’s question met the typical standards of inquisitiveness that i have come to expect from this forum. I think that should be chalked up to a misunderstanding followed by a friendly handshake.
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Old 08-11-2020, 07:20 AM   #11
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For what it’s worth, I thought Frosty’s question met the typical standards of inquisitiveness that i have come to expect from this forum. I think that should be chalked up to a misunderstanding followed by a friendly handshake.
Sage advice but I feel your premise is wrong. It was not directed at you. Anyhow this has nothing to do with my question and has become a distraction. So. let's leave it alone, okay? Still interested in answers about the exhaust. So far, only one.
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Old 08-11-2020, 08:05 AM   #12
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Quote:
Originally Posted by KnotYet View Post
I remember when BMW entered the marine engine market (at least in the US) in the
early 80's. They seemed well designed and built.

First I would measure the I.D. of the turbo outlet if that is different to your 3.5" pipe.
If it is actually 3.5" then the 2.5" pipe will be a significant restriction.
If you can get it redone to match the turbo outlet then that is what I'd do.

Turbo engines need a low restriction exhaust to make their rated power
and to keep the EGT in the desired range.
If you haven't done it, have a bung for a pyrometer put in,
the closer to the turbo the better.
Understand that the motor was made in Italy by Vito Motori and marininized by BMW. Mercruiser bought BMW Marine and continued marketing the engines eventually merging them with their own line.

Do not know what the EGT range is on this engine. I have a good maybe 400 page service manual which could have the answer. The pyrometer idea has merit. Thanks.

If I install one, run the engine and it runs within EGT range I am good to go? If not in range (hot) I have a problem? I wish a diesel exhaust engineer/expert would come forward and answer the question beforehand but they also want ice water in hell. I appreciate your suggestion and will look into it.
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Old 08-11-2020, 08:41 AM   #13
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Quote:
Originally Posted by friz View Post
Understand that the motor was made in Italy by Vito Motori and marininized by BMW. Mercruiser bought BMW Marine and continued marketing the engines eventually merging them with their own line.

Do not know what the EGT range is on this engine. I have a good maybe 400 page service manual which could have the answer. The pyrometer idea has merit. Thanks.

If I install one, run the engine and it runs within EGT range I am good to go? If not in range (hot) I have a problem? I wish a diesel exhaust engineer/expert would come forward and answer the question beforehand but they also want ice water in hell. I appreciate your suggestion and will look into it.
Using a pyrometer to monitor the EGT is a good idea on any turbocharger. The actual
temperature matters but a sudden temperature change can act as an early warning.

The turbo manufacturer, usually different than the engine builder, will have the
operating range info. Under load you may normally see 1000 degrees or higher.

The best placement for the probe is within inches of the exhaust turbine, right on
center. The typical probe can be bent somewhat to achieve the best placement.
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Old 08-11-2020, 12:02 PM   #14
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Quote:
Originally Posted by KnotYet View Post
Using a pyrometer to monitor the EGT is a good idea on any turbocharger. The actual
temperature matters but a sudden temperature change can act as an early warning.

The turbo manufacturer, usually different than the engine builder, will have the
operating range info. Under load you may normally see 1000 degrees or higher.

The best placement for the probe is within inches of the exhaust turbine, right on
center. The typical probe can be bent somewhat to achieve the best placement.
Okay, on which side of the turbo? Have read that that the turbo absorbs an amount of heat being oil cooled, making the outflow side gas cooler than the inflow side gasses.
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