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  #1  
Old 13-08-2014, 01:49 PM
E46ACS E46ACS is offline
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Default Why is the S54 only 325bhp in the ZM?

Hi all,

First post and its a question!

I've owned many M3's (5x E46, 1x E36 & 1 E30) but now have a family friendly estate and now have the need for a toy, and having been a long term lover of the Z3MC, the time is right. I've read this forum (a lot) and is a credit to you all.

But there is one question I haven't been able to answer, I've done a search on here and elsewhere, but cannot find the answer:

Why is the S54 'only' 325bhp in the Z3M when it is 343bhp in the M3 & Z4M?

Is it something to do with the exhaust?

I would be interested to know form any owners who have experience of the S54 in both the Z3M & M3 to know what the difference is. Also, what is the 'real difference between the S50 & S54? I don't mean the DSC/grils etc, I mean out on the road, what is the difference?

I wasn't that impressed by the E36 M3, but loved the S54 (hence owning 5!), so I am keen to know to assist in my search. There aren't exactly loads around for sale to go and test drive!

Thanks in advance
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Old 13-08-2014, 03:01 PM
Fat Tony Fat Tony is offline
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I think I've read that they reduced the rev limit for the S54 M Coupe (Z3M)
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  #3  
Old 13-08-2014, 05:18 PM
E46ACS E46ACS is offline
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Quote:
Originally Posted by Fat Tony View Post
I think I've read that they reduced the rev limit for the S54 M Coupe (Z3M)
In the M3 its 8250 (iirc), is the Z3M 7400? Would that account for the 28bhp difference? Surely raising the rev limiter would restore the difference then?

Although this leads me along another thought process; if the S54 engine is the same, is it the limitations of the gearbox that meant the engine had to be de-tuned (by the ECU mapping) so as not to put too much through the gearbox? Is the gearbox from the 3.0 E36 M3? (I could be talking total bollocks at this point)
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Old 13-08-2014, 03:02 PM
paulwirral paulwirral is offline
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I read in a magazine it was something to do with the exhaust manifold and space issues , could be bollocks mind , I also read that Adolf hiltler flew to the moon in a b52 bomber in the Sunday sport
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Old 13-08-2014, 05:10 PM
E46ACS E46ACS is offline
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I read in a magazine it was something to do with the exhaust manifold and space issues , could be bollocks mind ,
I thought it might be this, but according to another source today, the manifolds are the same.

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Originally Posted by paulwirral View Post
I also read that Adolf hiltler flew to the moon in a b52 bomber in the Sunday sport
This is true
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Old 13-08-2014, 05:15 PM
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Dave P Dave P is offline
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Lower rev limit on the M Coupe compared to the E46M3/Z4M etc
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Old 13-08-2014, 05:30 PM
paulwirral paulwirral is offline
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Quote:
Originally Posted by E46ACS View Post
I thought it might be this, but according to another source today, the manifolds are the same.



This is true
I see your from Durham , I'm from Gilesgate originally , and I knew there was reason to doubt that headline all those years ago it must be true if another daft Geordie says it is
I can remember reading z coupes were held back a little so as not to embarrass the m3 flagship , could make sense I suppose ?
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Old 13-08-2014, 05:41 PM
E46ACS E46ACS is offline
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Quote:
Originally Posted by paulwirral View Post
I see your from Durham , I'm from Gilesgate originally , and I knew there was reason to doubt that headline all those years ago it must be true if another daft Geordie says it is
I'm no Geordie (not a Mackem either! )

It looks like the lower rev limiter is definitely the cause of the lower power, but no closer as to why?
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Old 13-08-2014, 06:52 PM
paulwirral paulwirral is offline
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Quote:
Originally Posted by E46ACS View Post
I thought it might be this, but according to another source today, the manifolds are the same.



This is true
Quote:
Originally Posted by E46ACS View Post
I'm no Geordie (not a Mackem either! )

It looks like the lower rev limiter is definitely the cause of the lower power, but no closer as to why?
I just get called a Geordie because I stick out like a sore thumb down here when I speak among the scousers !
Good luck with your car search , I had one for a couple of years and enjoyed the experience , don't discount a modded one , they are a lot better than standard ones if your precious about originality .
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  #10  
Old 13-08-2014, 05:46 PM
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rsk289 rsk289 is offline
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One consideration is the rod bearings (see other threads).
The story I've heard is that the early (pre-December '02) S54 engines had issues with spinning or running rod bearings at sustained high revs. This would apply to all S54-engined Z3Ms as they were built before that date.
As a result, BMW recalled all E46 M3s and did a bearing-change on them FoC. For some reason, they didn't offer a recall for the Z3MCs with the same motor, so these didn't get done. Instead, a lower rev limit was imposed (change to ECU?). Later S54 engines had a different rod design with different rod bolts which presumably eliminated the problem.
I'm old skool, with a garage full of cast iron pushrod V8s, so am not used to revving anything over 5K. However for peace of mind I'm thinking of changing the rod bearings in my S54, but haven't taken the plunge just yet.

Roger
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