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Welcome back Darren , always nice to hear from you .

Interestingly enough , there is appx 300 grammes difference between the 3.8 vibration damper and the 3.6 variant . The pulleys weigh the same on both the S38B36 and S38B38 .

As my engineers have said , if anyone has reservations about this modification , do not fit their flywheel ....... it's not a problem !

As mentioned , Time will tell !

My 3.8 with the 4.5 kg flywheel drives superbly , with no issues at idle . I'll be asking my engine builder to stick it on his rollers shortly and will update with results .

Meanwhile , the S38B38 that will be shod with the 2.8kg variant will be getting the complete treatment , with all components individually balanced , before being assembled and balanced as a whole ......... we'll see what the results are in due course !

Those who do nothing will achieve nothing ............. fear is a lousy companion and many people trade on it !

I look forward to hearing more on the progress of your 400 BHP normally aspirated S38B38 and am truly respectful of your discussions with Paul Rosche ........ a true genius and an engineer worthy of the title !

D
 

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Meanwhile , the S38B38 that will be shod with the 2.8kg variant will be getting the complete treatment , with all components individually balanced , before being assembled and balanced as a whole ......... we'll see what the results are in due course !

D
Now this is a completly different story! With all engine components balanced, it just might be OK.
 

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Welcome back Darren , always nice to hear from you .

Interestingly enough , there is appx 300 grammes difference between the 3.8 vibration damper and the 3.6 variant . The pulleys weigh the same on both the S38B36 and S38B38 .

As my engineers have said , if anyone has reservations about this modification , do not fit their flywheel ....... it's not a problem !

As mentioned , Time will tell !

My 3.8 with the 4.5 kg flywheel drives superbly , with no issues at idle . I'll be asking my engine builder to stick it on his rollers shortly and will update with results .

Meanwhile , the S38B38 that will be shod with the 2.8kg variant will be getting the complete treatment , with all components individually balanced , before being assembled and balanced as a whole ......... we'll see what the results are in due course !


Those who do nothing will achieve nothing ............. fear is a lousy companion and many people trade on it !

I look forward to hearing more on the progress of your 400 BHP normally aspirated S38B38 and am truly respectful of your discussions with Paul Rosche ........ a true genius and an engineer worthy of the title !

D

Hi D, Well said.

I think I'm going to go for the 4.5 kg one to start with then when I have my engine rebuilt around this time next year the 2.8 kg item. At the same time I will fit my 280/6.
I was in Somerset yesterday checking up on progress with Fritz & took the beast out for a drive! Loved every min of it but felt that my 280 was becoming noisy so it's coming out next week to be rebuilt.

Will give you a call when it's done so that I can get a 4.5. Was the £345 including the dreaded?

Did you get a price on the flywheel bolts from BMW?
 

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Thanks Shaun .

The bolts are only £1.95 + vat from BMW ....... I had to check with my dealer who I thought had told me in excess of 4 pound a bolt .... must get the cotton buds out !

Call me to discuss your options m8 .

D
 

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Consider the above.
Some factors may leap out if you read through & with B38, much is relevant. Long axis crank, increased throw & high rpm for the era.
S54B32 had to radically redesign the reciprocating parts & reduce valve train mass for the engine to survive increased long term rpm usage.
Almost a clean sheet of paper design was required to achieve a durable 1000 rpm increase over the B38.
Some very gifted Engineers strove to bring you a durable package & tested it, made significant changes from losing cranks on M1 through
M88, B36 & finally B38, the largest capacity straight 6 ever made by BMW & likely never to be eclipsed in that respect.
Lots of changes occurred through the 25 yr evolution period. Not all of it was without problem.

Many of these engines are old & worn now. Addition of parts that can significantly change the characteristics of a new engine, never mind
an old one with worn bearings, valve guides, fatigued springs etc should be considered.
Can changing one component make a radical difference ? Yes, I think it will in extremes.

Anri mentioned Camber. He did some good development work. He also balanced the engines individual parts & as a reciprocating mass.
Thats not so much the issue, indeed one of my own cars has a 4.5kg flywheel & twin plate clutch. The engine was rebuilt & balanced together
inc flywheel.
It produces 35% more power than stock & 8,200 rpm limt. I expect the engine to have a 60% shorter life span at best.

Trading in fear versus trading in ignorance ?
If trading in fear is pre-empting or noting the possibility of expensive failures then count me in. Trading in ignorance is asking your customer
base the questions you should already know the answers to !

Best regards
Darren
 

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Darren,
Thanks for your time with this absolute technical details !
 

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Will try again as my last post got lost! :grrrrr:

Very interesting read & I fully understand what has been stated. Your missing some VERY IMPORTANT points though!

1) The RPM limit is not being raised.

2) The S38 crank is safe to 9000 RPM!

3) At 7300 RPM (50 RPM above the OEM limiter) the crank is only using 81.25% of its maximum. At 7250 is 20% inside its maximum range.

4) The vibration damper is NOT being changed. (Read your explanation again to see why this is important!)

5) By decreasing the parasitic affect on the front pulley (E.g...in my case...No air-con pump & no emissions pump) the sideways forces on the hubs is reduced which intern decrease the heat build up which intern increases the safety margin over OEM!

6) As you stated the radius of the flywheel is very important. The radius of the flywheel D has fitted (And soon to be me) is the same radius as the OEM item. The only difference is weight.

7) The frequencies that you mentioned are exactly the same as OEM because we are not asking them to work outside the OEM RPM range.

8) The only two differences over OEM are the speed that the frequencies accrue & the pendulum affect. The speed is not important because the vibration damper is still the OEM item
With the lighter flywheel it takes less time for the mass to accelerate. It also places less stress on the end journal during acceleration which intern creates less twisting force in the crank which intern increases the safety margins again over OEM!
 

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Thanks for that.
Tried to load PDFearlier but would not load.
Post revised.

Cheers.
Darren
Ooooops , the dangers of the cut and paste genius !

Trading in both fear and ignorance must be an awful place to stand .

Thanks again for your comments , Darren .
 

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Very good thread, very nice points from both sodes of the coin.... I am ansiouxly waiting for the results in real life.... if I didnt just install a brand new OEM B38 FW in my car with the rebuilt, I would definetly try my chances with the 2.8kg one
 

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Real life are the key words here Paulo .........

Once upon a time all flywheels were single mass , before refinement and smoothness became requirements for manufacturers .

If you seek performance gains , you may be willing to compromise in other areas .

These are great cars in standard guise when running well and that is more than enough for many owners .

I am more than happy with the lighter flywheel on my own car and am keen to share the experience with other members and owners .

If other members have hard facts and real life experience of major failures as a result of similar modifications , I am keen to hear of them , as I am keen to hear of any works that owners carry out on their M5s with positive or negative results .

We can only all benefit as a result of these experiences being documented !

One Big Happy E34 M5 Loving Family !
 

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There is a very easy way to understand why the lighter flywheel is not a problem.

Take two identical BMW cars...For example two e34 535i's. Could be any other as long as they are identical. One with a manual gearbox & the other with an auto.

Put both cars on a ramp along side each other & remove the gearboxes.

Do the flywheels look the same? NO!

What is the difference?

The manual has a heavy flywheel but the auto has a very thin plate!!

Why does the auto only have a very thin plate?

It is only there so that the starter motor has a ring gear to start the car!

THE VIBRATION DAMPER IS AT THE FRONT OF THE ENGINE DIRECTLY BEHIND THE FRONT PULLY. IT IS NOT THE FLYWHEEL. LEARN TO READ!!
 

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Ooooops , the dangers of the cut and paste genius !

Trading in both fear and ignorance must be an awful place to stand .

Thanks again for your comments , Darren .
I really believe that comments like this do not serve this community well.

The fact that Darren Farrell is a dear friend does not cloud my objectivity when it comes to car matters...specifically as they relate to the E34 M5. But, the issue is that the man may well be the number 1 E34 M5 specialist in the world.......I used to think that I was well grounded in matters as they relate to these fine cars..but....then I met Faz and fully realized that I know absolutely nothing in comparison. It's one thing to read books and gain hands on experience and its another to study engineering in a university and work with major auto manufacturers.....not on an assembly line assisting robots but as a key member of powertrain design teams. The credentials, in my opinion and I'm sure several others, are impeccable and beyond reproach.

If a lightened flywheel feels better and seems to provide better performance then by all means go for it....the only issue is that when changing parts make sure you ( the individual ) have all the facts as they relate to function and durablity.....i.e. go in with your eyes wide open. Most of us here cannot make judgments based on in depth knowledge of automobile mechanics and should consequently leverage the knowledge base of those that can. If a Fazlike person has a contrary opinion to a modification you would like to carry out you would be very well served listening to his advice first.

I'm not saying that every word he speaks must be taken as gospel ( though I take it as such this is an individual choice ) but comments that call in to question his competencies do not serve us all well.

Cheers
 

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I'm not saying that every word he speaks must be taken as gospel ( though I take it as such this is an individual choice ) but comments that call in to question his competencies do not serve us all well.

Cheers

Eric,

I didn't find Dave's comments unhelpful to the board. We all have different views and opinions. Dave contributes heavily to the board, much at the expense of his own time and never in pursuit of boosting his bank balance. I have spent countless times in the company of Dave where fellow members have called, requesting help, parts or advice and he always obliges. My own BMW e34 M5 is much better looked after now, than it EVER has been before, despite being worked on by ALL other highly regarded specialists on this board or otherwise.

I look at it this way. Dave looks after my car, because Dave knows what he is doing, and works on these cars day in and day out, and has probably driven more e34 M5's than anyone else I know and works on BMW M5's everyday. He has owned countless examples, and therefore when he tells me something, I listen. I don't need to see a certificate that tells me he has sat some exam about something unrelated, or want him to speak with an air of sophistication that is intended to impress me..

Dave's approach is like mine. Cut the B/S and just tell it how it is, based on what you know. Look at our trackcar project, we listened to countless information from fellow members who had built similar cars and had REAL experience on the subject matter. The fact that our track car has never failed ONCE despite countless UK trackdays and ring trips (all of which were at the limit of car and driver) is a total tribute to the work and attention of Dave and his real world knowledge of these cars..


Steve
 

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I really believe that comments like this do not serve this community well.

The fact that Darren Farrell is a dear friend does not cloud my objectivity when it comes to car matters...specifically as they relate to the E34 M5. But, the issue is that the man may well be the number 1 E34 M5 specialist in the world.......I used to think that I was well grounded in matters as they relate to these fine cars..but....then I met Faz and fully realized that I know absolutely nothing in comparison. It's one thing to read books and gain hands on experience and its another to study engineering in a university and work with major auto manufacturers.....not on an assembly line assisting robots but as a key member of powertrain design teams. The credentials, in my opinion and I'm sure several others, are impeccable and beyond reproach.
Eric, would you have been so ready to endorse Faz's services if the first posts you had read about him had been negative? The fact that bad comments are kept to themselves is testimony to the higher ground that these people stand on.
 

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Eric, would you have been so ready to endorse Faz's services if the first posts you had read about him had been negative? The fact that bad comments are kept to themselves is testimony to the higher ground that these people stand on.
Agree Jnr.

Life is about learning from your mistakes.

I have spent thousands paying those who "talked a good game" but when it came down to actually doing the work, were ffffing useless!


Steve
 

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Very valid comments guys.....but we all have our opinions right or wrong as they may be.

David is a huge contributor to the board and a lot of people have benefited from his advice and service.

We'll forever differ but as Dave says we're..All one big happy E34 M5 loving family !
 
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