s38 engine performance ? - BMW M5 Forum and M6 Forums
E34 M5 Discussion 1988-1995 Sedan and Touring

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post #1 of 4 Old 23rd May 2012, 08:27 PM Thread Starter
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s38 engine performance ?

Hello guys,

I am happy owner of one late model e34 m5 I don't have much technical knowledge(or only some basic) and I wanted to know more about s38b38 engine. I'm mainly interested, how the M guys achieved such a high performance from 3.8 litre engine ? It has about 90 hp per litre, which is not standard and much more compare to other atmospheric engines. I have tried to search some information everywhere, but didn't find anything that would explain me this. The only thing I know, that it's race engine, but that's not enough for me I'll be happy to hear some deeper information of how is s38 built to make such power output.

Thank you very much

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post #2 of 4 Old 23rd May 2012, 08:49 PM
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post #3 of 4 Old 25th May 2012, 10:08 AM
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Some 'details':

1. Mean piston speed = ~ 21,6 m/s - my Yamaha R1 bike from 2002 has ~ 20 m/s and a Ferrari F355 with 8500 rpms ! has ~ 21,8 m/s
A Formula 1 engine with 18.000 rpms has 25-26 m/s and a diesel engine has 8-10 m/s - to put things in perspective.

2. Has the 'resonance flap' (variable intake manifold) - optimises the air flow to give the best efficiency throughout the rpm range - so that's why it gives 80% of torque at just 1800 rpms !
I understant that this system was used also by Ferrari but in the F50 - the supercar ! - in 1995. BMW has it from 1988.

3. Basically it has all the 'ingredients' of making power.
-Displacement - is the biggest L6 ever made by BMW.I don't know they will make something else to top it.
-High rpm - 7250 rpm - very big for that period.
-High volumetric efficiency - how well the engine 'breathes' - that's why individual throttle bodies (racing detail), the exhaust manifold ( i understand that is a work of art! ) and a lot of other nice details that give it's unique response, sound, feel, power delivery etc.

4. Racing pedigree and heritage - the last direct descendent of the M49/2 engine from which BMW Motorsport created its legacy.
Upgraded and refiend on every generation and the S38b38 is the final 'incarnation'.

And to quote some that i found m5board:

"What you have to realise is that BMW Motorsport were the finest builders of engines as per a converation I had with other members off line.
As has been stated previously the 3.8 was the ultimate development using all the current proven technology to provide as much power as possible while being tuned for reliability and the ability to pass emmitions tests around the world.
There was no further development that could be done to the 3.8 while retaining the everyday drivability that these cars retain."

5. Not only is it a high performer, it is also built to last.
Cast iron block, duplex timing chain, individual coils, forged internal etc.

So, (for me) it is a special engine maybe the best engine of this type that a non millionaire could afford
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Last edited by Rorschach; 25th May 2012 at 10:30 AM.
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post #4 of 4 Old 25th May 2012, 11:18 AM
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The above has given me goosebumps ...........

Thanks for sharing !


Better a day as a tiger than a lifetime as a sheep !

91 Sebring 3.6 | E28 UK RHD M5 | E34 UK RHD 3.8 | E34 M5 Touring | E24 M635CSi UK RHD

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