BMW Rods specifications table

[nuvolarossa]

Here there are some specifications about BMW rods. I hope that this thread will stop newbies to ask questions about this.
 

 
EDIT: the yellow zones are not certified, so I need your help to compile them;) All the white zone is proven and documented.
 
NOTE: when helping me you need to write a reference, that can be a link to a page where it confirm what you're saying or if you've measured them with your hands write please.
Here phrases like "I think that they're forged" are not welcome. We need the truth, not hypothesis.
If I'll have more freetime I'll make something about pistons to definitely write a manual about frankenstein engines because all those identical threads are boring the forum:D
 
so let's help to full this chart

UPDATED.

[nTranced]

thanks man

[nTranced]

what would a 5mm reduction in rod length yeild as far as compression goes on stock 10:5CR compression pistons, Looks like an 135mm early m50 non vanos motor would do it.

[nuvolarossa]

what would a 5mm reduction in rod length yeild as far as compression goes on stock 10:5CR compression pistons, Looks like an 135mm early m50 non vanos motor would do it.

what engine are you speaking for? M42 has 10:1 CR stock with 140mm rods, if you put 5mm shorter rod in there you'll have a huge static compression drop, to reach something between 6,x:1 to 7,x:1, too low:eek: is not so simple as changing only the rods as you see , but there are a lot of factors that change the compression ratio, to have an idea of which they are read the input fields in this compression ratio calculator http://www.not2fast.com/turbo/compression/compression.shtml
 
My mind speaks always for the best ipotetical engine build (and this is $$$), but if you want to lower the CR from 10:1 to 9 you can always put a thicker MLS headgasket and you're there until the engine will survive or until the thicker HG will survive:)... if you have some kind of respect for it will last long enough at low boost and with a right setup for human DD power gains it's proven to be a good solution, but if you want to go over 300bhp with only that and with poor fuel/spark tuning you're in the wrong road, you'll melt all :p. keep in mind that if you open the engine it's not worth to rebuild it to factory specs, just as you're there you can change something even on a budget
Saying that the M42 internals in stock form can't be turboed is false too. Sure there is a limit, for sure it's a risk, but at low boost and with care it would ran just fine if the engine has not bad wear...
I'll do it for steps... starting with low boost until 10-12psi with MLS headgasket, with the money saved for internals spend more on ECU/standalone/fuel tuning thinking as a reusable thing for bigger boost. Then optimise the car (fine tuning) at that boost level with expandibility in mind so to have a great DD. Maybe you don't need more than that power and you'll stop at that stage big power is not always faster
 
and think that the more you raise power the more you'll need to upgrade other parts in the car too... differential, gearbox, halfshafts, brakes, suspensions... all should handle the new power... if you want big power and poor handling go and buy a big displacement Mercedes Benz boat;)
 
I'm hijacking my own thread:confused:

[crazzy_hippo]

Whooo..... nice!!

Thanks for the table! Now I know I can use M50 135mm rods together with the M47 crank! Now, all thats left is the piston. I just need some strong forged pistons to go with the rods!

Btw, how strong are the M50 rods? Are they forged and able to hit high boost (over 20psi like M42 rods?).

Thanks!

[ludiagsm]

Whooo..... nice!!

Thanks for the table! Now I know I can use M50 135mm rods together with the M47 crank! Now, all thats left is the piston. I just need some strong forged pistons to go with the rods!

Btw, how strong are the M50 rods? Are they forged and able to hit high boost (over 20psi like M42 rods?).

Thanks!

 My friend has 318is turbo boosted on 1,7 bar with stock m42 pistons and 135mm M50 rods  and cometic head gasket it work fine witout problems.

[nuvolarossa]

sure he has 25psi of boost so under that boost the compression ratio raise by at least 1 number:D (but how is the car off of boost?)
power shouldn't be so linear
 
 

for a given octane rating, fuel detonates in certain temperature/pressure combinations. The higher and higher the pressure in your engine, the higher the octane rating must be (you can cool the air before it gets into the chambers, i.e. intercooling to reduce the detonation point but at some point, the cooling is overcome by the CR) in order to run as it should. By raising the CR, it forces the same fuel to ignite at a lower temperature; i.e. the higher the ratio the sooner the fuel ignites.
 
When the fuel, b/c of high pressure environment, detonates before it should (predetonation), the timing of the engine is off basically screwing up the internals. The pistons aren't at the top of their stroke when they should be, the valves are open when they s/b closed, etc. To offset the predetonation, a higher octane fuel has to be used as the CR increases.
 
When you throw in being able to up the boost in s/c or t/c, the lower of a starting CR you have the better; it means you can run say an 20 PSI boost vs a 14 PSI boost w/out getting detonation if the CR was low enough to begin.

if only Maximum Boost wasn't copyrighted, I would have posted some pages to let you understand better

[futron.sim]

My friend has 318is turbo boosted on 1,7 bar with stock m42 pistons and 135mm M50 rods  and cometic head gasket it work fine witout problems.

Thanks for the reply. OK, I am one step closer to building my dream M42 motor. How about the pistons? Any idea what piston I am able to use for the motor? Cause I am going to bore it up to 86mm and hopefully there will be some forged pistons I can use.

There is MM pistons but its out of my budget. Hoping for something lower in cost.

My aim is around 9-9.5 compression and run 1 bar of boost on an Eaton M90 supercharger. Aiming for 300HP with a 2L motor.

Thanks!

Btw, I found some Wossner pistons from their website. Only problem is I have no idea what the specification means and which are the ones I need to get my desired compression.

[nuvolarossa]

If you're in America quit from internet, take the phone and call them.
Tell them what setup you want and they will make everything you need.
Prices for 4 custom pistons are around 650 USD... so call to all BIG names that produce pistons and let us know. There are eagle rods 140mm and 135mm on ebay for 300usd, tell them that you need some pistons for that CR with rod length you choose and they will do it. It's good 300$ for forged H-beams rods to you?
 
EDIT: I read after my post that you'll use the M47 crank so 140mm rods are out of discussion

[crazzy_hippo]

If you're in America quit from internet, take the phone and call them.
Tell them what setup you want and they will make everything you need.
Prices for 4 custom pistons are around 650 USD... so call to all BIG names that produce pistons and let us know. There are eagle rods 140mm and 135mm on ebay for 300usd, tell them that you need some pistons for that CR with rod length you choose and they will do it. It's good 300$ for forged H-beams rods to you?
 
EDIT: I read after my post that you'll use the M47 crank so 140mm rods are out of discussion

Thanks for pointing me to the Eagle conrods. I did see them on ebay and they are much cheaper compared to MM rods. Well, they seems just as good as well.

I am not from US so it would be difficult to call them. I will try to email them to see if they could custom make pistons for me. This is my parts list.

88mm diesel crankshaft
135mm M52 Eagle Conrods
*suitable pistons*

Now all thats left are suitable pistons for 9-9.5:1 compression. Hopefully I will be able to run at least 15-16PSI and gun for about 330WHP.

[rob_e30]

Good info... this should be sticky

[nuvolarossa]

now I need to search for good references that say which are forged and which are cast then it will be a good sticky

[ose30]

Great info, that's what i have been looking for ! Thanks

I hope that this thread will stop newbies to ask questions about this

Yes i am a newbie, have been involved to E30's just a little bit over 21 years

[nuvolarossa]

you were clearly not involved in that comment
but it was to those that enter in the swap/build/turbo forum and start everyday the same thread instead to search, so I though that it would be great to try to write clearly some infos. The day I started this I had rods in my head so I started with this thread, but I hope to write something about pistons and maybe resuming  cranks info too
Now I know more than that table and I have informations about rods and internals from people that I would easily trust, but I want to see them wrote on paper by big names to avoid future misunderstoods.
If someone can help writing something clear about pistons that can be used on m42-m44, their specs  and so on it would be apprecied, as I don't know how many time can dedicate to this
 
The final goal would be a sticky thread that shows ALL specs of combinations crank-rods-pistons-headgaskets that could be made on M42-M44, even if NA, turbo or S/C... I know this is a dream

[crazzy_hippo]

I was looking thru some pistons on wiseco site and found their 3SGTE pistons. It has 22mm pin ports. The part no. is K615M86

Unfortunately, I have no idea if its suitable as I do not know what's M42's block height.

Anyone who knows how to calculate the compression etc pls help to take a look at this piston and see if its suitable for M42.

Thanks!