According to Mahle (the manufacturer of the pistons), the compression height is 28.32mm. BMW uses rods at 5mm increment, so they can't very well be anything else than 135mm.
http://www.motorenteile.mahle.com:80...ngine/byParams
Last edited by granlund; 06-03-2012 at 12:51 PM.
The Calculations are in.... Anyone want to double check this:
Compression calculation M50B30 BMW Mix
Data:
Deck Height (measured) 210.00mm
Bore (measured) 84.00mm
Stroke (measured) 89.60mm
Rod Length (measured) 135.00mm
CylHeadVolume (measured) 36cc
Gasket Thickness Compressed (OEM Spec) 1.75mm
Gasket Bore (Measured) 85.00mm
Piston Position
Deckheight - 1/2Stroke - RodLength - Compression Height
210 - 44.80 - 135 - 28.32
Position is 1.88mm BELOW deck
Swept Volume:
Pi/4 * Bore2 * Stroke
.785 * 7,056 * 89.6
SV= 496.29 cc
Gasket Volume:
Pi/4 * Bore2 * GasketThickness
.785 * 7,225 * 1.75
GasketVolume= 9.92 cc
Clearance:
Pi/4 * Bore2 * Clearance
.785 * 7,056 * 1.88
Clearance= 10.41 cc
Compression Ratio:
Swept Volume + CylHeadVolume + GasketVolume + Clearance / CylHeadVolume +
GasketVolume + Clearance
496.29 + 36 + 10.41 + 9.92 / 36 + 10.41 + 9.92
552.62/ 56.33
9.81: 1 CR
In order to achieve a 10.7:1 CR à 496.29/9.7 = 51.16cc total
Current - Required
56.33 - 51.16 = 5.17 cc
Consequently:
5.17 / (Gasket Volume / (Gasket Thickness*10)) = Amount to be milled off the
block
5.17 / 5.54 = 0.93mm (Will give a 10.7:1CR)
You confirmed we take 1.00mm off the block and skim the head. This will
slightly increase the CR (ballpark number 10.75/10.8:1).
Please Let me know if this all sound good????
P.S These calculations do not account for valve relief cc's (I will try to calculate the volume later but will get a slightly skewed result as mine are coated)
Last edited by luminmiller; 06-05-2012 at 03:03 PM.
The biggest mistake can be on cylinder head volume mesurment. I googled it to be 33cc, but i see u measured it 36cc. If all input data are correct then you have correct calculation. With your input data my calculation CR is the same. 9.82:1
I had them measure the volume on each combustion dome as my research told me 33cc, but all six came back at 36cc on my m52b25 (e39 523 head).I googled it to be 33cc, but i see u measured it 36cc
I think i will measure my M50B25 to be sure. Now i am thinking what will happen with ignition timing when you will take 1mm of the block. Will engine work fine with factory camshaft alignment?
I was told on another forum that the tensioners should be able to take up the slack without any problems, but was never given proof or details. Anyone have experience shaving a block?Now i am thinking what will happen with ignition timing when you will take 1mm of the block. Will engine work fine with factory camshaft alignment?
Ok i found on wiseco piston catalog that head displacement for M50B25 is 34cc and M52B25 it is 36cc.
Sourced http://www.wiseco-europe.com/Catalogues/EA12.pdf
So the new calculation with the wiseco and luminmiller data:
Compression ratio for M54B30 stroker in M50B25 engine is 10.184
I hope we got all correct now.
In my stroker i think ill shave off 0.5mm of the block CR for that is 10.679 and i am in safe zone. If the head had been shaved i think i will get something about 11:1 and will be happy with it on daily driver.
Last edited by Wcoast; 06-06-2012 at 07:19 AM.
I agree, the tensioner should take up the slack from shaving. The distance to the drive side of the sprocket from the crank is less, so I think there will be some retard, has hakentt suggested. Proper timing using the cam blocks could probably absorb this:
A 1mm shave would mean the chain pulls 1mm less at the edge of the sprocket. Sprocket with diameter of ~80mm (??? can't measure right now) -> circumference = pi*80 = 251mm... (1mm/251mm) * 360 = 1.4 degrees of retard from head shaving. Can someone check this?
If deck height is 210.00mm then the M50B25tu stack height is 0.05mm above the deck? (75/2 + 140 + 32.55) = 210.05mm
By luminmiller's calculations it comes to 10.135:1 ... (552.62 - 2) / (56.33 - 2)
so yes I think the CR is known to be within some range of 10.2:1 using M50B25tu + M54B30
Last edited by carwiz008; 06-08-2012 at 06:27 PM.
M50 3.0L stroker project: https://imgur.com/a/l8owP?nc=1
Confucius say: Buy the best, cry only once.
Carwiz are you sure that M50B25TU came with 140mm rods and 32.55 piston height?
all of my research says yes but I have not measured my M50 VANOS yet so not 100%
[strike]edit: Do gaskets have larger bores than the cylinders? I'll have to measure the one in my kit but I think it might be slightly larger than the cylinder.[/strike]
Last edited by carwiz008; 06-06-2012 at 06:53 PM.
M50 3.0L stroker project: https://imgur.com/a/l8owP?nc=1
Confucius say: Buy the best, cry only once.
If you see luminmiller's post he states his bore is 84mm while the gasket bore is 85mm.
Whoops, thanks. I missed that.
I made a graph to show the relationship between head shaving and compression ratio. According to my measurements in previous post #243, it is probably safe to shave by enough to achieve 10.5:1 ... however I assume no liability
I used luminmiller's numbers minus the head volume difference that Wcoast found, and then subtracted the shave volume as a function of x.
Intersection is (0.377, 10.5)
(y axis label should read CR = Y:1)
According to equations, shaving by 0.4mm will yield a compression of 10.52:1 and 0.6 degrees of retard on timing sprocket.
Last edited by carwiz008; 06-08-2012 at 06:37 PM.
M50 3.0L stroker project: https://imgur.com/a/l8owP?nc=1
Confucius say: Buy the best, cry only once.
Today I realized I overlooked some crucial points and anyone considering milling a block/head should Assess the whole picture prior to machining.
My block has been milled 1mm but I didn't check if the arp head bolt will sit properly.
Additionally the timing cover needs to be milled now and re-tapped.
And we will see what the timing looks like after installation.
I only want to take off .5mm, at most. Will there still be trouble with the timing cover?
M50 3.0L stroker project: https://imgur.com/a/l8owP?nc=1
Confucius say: Buy the best, cry only once.
Yes when the block goes to the machine shop make sure to have the timing cover bolted to the block and it can all be milled at once.I only want to take off .5mm, at most. Will there still be trouble with the timing cover?
so did anyone go with s50 crank and rods with m52 pistons to make that higher compression motor? anyone know the compression ratio, i saw 11.5:1 but havent confirmed that. in the mean time still searching for the m54b30 rotating assembly but am interested in the alternatives
Someone tried using M50 pistons in M52 block because they are slightly taller and raise compression of the M52. http://forums.bimmerforums.com/forum...d.php?t=680024
He never finished so I don't know if that works.
piston compression heights (head to pin center)
M50tu: 32.55mm
M52: 31.82mm
Last edited by carwiz008; 06-22-2012 at 03:49 AM.
M50 3.0L stroker project: https://imgur.com/a/l8owP?nc=1
Confucius say: Buy the best, cry only once.
I don't have any measurements yet on m52b28 pistons, I'm still waiting on my m50 to arrive, I can easily get the s50 crank and rods with m52b28 pistons all day, m54b30 is another story, that's why I ask, I saw the OP say something about it being a high compression motor, something like 11.5:1 or so, anyone with m52b28 pistons could you supply us with pin height I need alternatives! Haha
man i've been on the lookout for a local m54b30 and it seems like houston doesn't have any for cheap :|
Ya I hear that, I found "5" pistons and connecting rods with crank 150 miles away. I called and asked if they had the 6th set and they sold it. Wtf I swear haha I can't catch a break, I want all 6 from the same motor so I know nothing is "different", alternatives would be great! Lets hear them haha
If you know anyone who owns a micrometer or digital calipers, make them your best friend. Mine tell me the size of something within 0.0005 of an inch.. that's a pretty good way of knowing what's "different", and how. Get factory specs, then measure all the used ones to make sure their still within it. Rest, assured. Fill empty 6th spot with a brand new one.Originally Posted by pussiwillow
Boom.
Alternative.
Protip:
Used cars are always lemons.
Especially if I've used them.
Five pistons and rods with the crank? You'd need the crank looked at anyways. That ish blew up for sure and if it's missing a piston, he probably leaned out or dropped a valve/over-revved. Deff a good thing you did not buy that assembly. At best you'd be hoping he didn't grind too much metal into the journals. There is no other reason for a piston to be missing. The chances of him selling one piston are next to none.Originally Posted by pussiwillow
Last edited by sjpgoalie; 06-23-2012 at 06:02 AM.
Bookmarks