Interesting 2.7 "shaved" piston turbo applications

[rvaughnp]

Being i am on a budget "shaved" adventure. I was wondering what other pistons might fit in the b27 crank (81mm stroke) and the b25 rod (135mm) combination. Others would work measurement wise, but would not have the domed profile. But, I did come across some interesting applications for this 81/135 and even 84/135 combination. I thought that a quick revving Turbo would be cool. I personally won't be building it; just thought the numbers looked cool. I believe some of these have been mentioned in previous threads. I thought I would make a quick spread sheet showing their relationships.
All of these applications but one require shaving of the piston.

And for all you "custom" piston guys... i know... i know... If you're going to the expense of a turbo and everything else why not just indulge a little more for customs? This is a budget alternative.:giggle: The numbers might help someone going this route, turbo or N/A.

Not sure what the CR would be on the 28.32mm (below deck).
Unsure of any of the CR ratios. Haven't recieved credit for that class yet.

Probably shouldn't have put in the M50B28 reference, but thought it was cool.

[Aptyp]

that 206.7mm you got is going to mess you up, because m20 deck height is 206.1mm and m50 is 210mm.

So you are measuring for pin height, but you also need to be measuring for pistons design. The taller piston you shave, the weaker it will be. The shorter piston you use, the more material you'll have to fly-cut out.

Stock E piston design is also best for turbo design because of the dish design. The only con of this setup is rod-angle, but it's still well within reason around 17 degrees. Also 130mm rods from E are lighter as well.



If you have access to Mahle paper catalog, you can see all other pistons. They have got 10 designs that aren't stock, but are designed for application. I'm very interested in what you'll do, so I'm subscribed. Good luck, bud.

[rvaughnp]

I appreciate the subscribe but i am not really keeping a log of my build. I wil be doing a thread of different piston manufactures that make custom pistons for a m20 block, 2.7 crank, 135mm rod. As well as the actual amount shaved from stock 2.5 pistons to fit this application. And yes, that is if once bcrperformance recieve the piston and measure it to see how much it will allow to be shaved, and if it's safe.
Here is the thread i started with this idea. I will add a hyper link at the end of it leading to the "write up" thread.

http://www.bimmerwerkz.com/forum/3-series-e21-e30/2-7-stroker-using-2-5-a-67052.html

As this is a true budget build; I have to wait until funds accumulate to purchase items. I have already recieved my extra piston/rod set. I now have to wait until i can collect enough for my motor. Then i want to place the 2.5 rod/piston atop the 2.7 crank and measure differences between the two, before i send the pistons off to bcrperformance to get measured/shaved.

that 206.7mm you got is going to mess you up, because m20 deck height is 206.1mm and m50 is 210mm.

I was going to post a qoute i posted from Jim Rowe (MM) about the deck height issue, but as i reflected back on what he told me, i did not ask if the 206.7 was actual "deck height" vs "pin height". I am not opening this again, just again feeding my curiosity on this issue. Something doesn't line up when both the block and the pin height are 206.7, yet the piston ends up out of the block. So, i am not discounting it, just this is first time someone has made this claim that i have found. Maybe in the future if i find myself with nothing else to do and i feel like breaking down my block i will physically measure the block. Maybe.;)

Thanks for the reply