Pistons for m20 Stroker

[bmwmaster81]

Hi,

until now I have built some m20 strokers with 81mm eta crank and 130mm rods with 2.7l or the other known way with 84mm m52 crank and 130mm and ended at 2.8 l.

But now i want to go further and invest in custom pistons. But which concept is the most sensfull?

Here what I already have in mind and my view.

1.

Ireland Engeneering Mahlesport Pistons:
They work with 84mm crank and have 85mm bore.
You get about 2860 ccm and they have a dome shape which fits to the original head. But the ccm gain is not so big.

2.
Ireland Engeneering custom forged pistons:
They have a flat top which doesn't fit to the 885 Head casting. I think this must be an disantvantage and tends to knock earlier? or maybe its necessary to cut hemispherical chambers?

3.
Metric Mechanic Sports Piston.
I think they have the same problem like NO. 2.
But you can build easily build an 3 or more liter engine.

Or are there more good pistons on the market?

I have all necessary cranks to combine to be able to build a good stroker.
(81mm / 84mm / 86 mm/ 89.6mm. But which would be the best piston.

Engine is for street use and will not be reved higher than 6500 rpm.

[Mediumrarechicken]

I say Arias they are what my buddy uses at his race shop. They have a civic that makes around 1800hp that is the world's fastest so I follow what he says and does.

[SkiFree]

Option #1

I was in the same boat a few years back. After speccing dozens of M20 stroker kits for clients, I just felt there was a gap in the market for a well-thought out stroker piston that emphasized a balance between power, engineering, and longevity (i.e. an ideal street stroker piston). At SEMA that year the connection was made with Mahle Motorsports and eight months of back and forth development later the initial 20 sets arrived on a pallet next to my desk at Ireland Engineering.

It is much easier to make a big-number race piston than a well-rounded efficient street-focused power piston. With larger strokes the wrist pin begins to encroach on the lower oil-control ring of a healthily-specced ring package, necessitating an support ring. In addition there is less material to spec a nice offset dish. Exacerbating this is often a 2618-alloy piston is used. This alloy works great for a strong race piston but it's expansion and contraction means that a wider piston/bore clearance is needed (which means more blow-by on start up [not helped by that wrist pin issue], which means faster wear. Not a problem if you're just after power).

Without continuing to blather on, I designed the IE/MahleMS piston to maximize good power-enabling design features while minimizing factors that limit longevity. Going any less (budget strokers) leaves significant power gains on the table, going any more extreme and the law of diminishing returns becomes a real concern for a street application. At last count there are at least 50-60 of these strokers out there now.


I do not make a cent from these (do not work at IE anymore), but just wanted to relay a little of the thought process behind their development. If you have any specific questions I've got tons of technical data and reference photos I'd be happy to email.

-Andrew Adams

[bmwmaster81]

Hi Andrew,
respect to your work. I have been really fascinated when i saw the Mahle Motorsports pistons the first time.
Just had been little disapointed because of usage of the 84mm crank. The difference to an 2.8l budget stroker in capacity is at the first look not big enough to invest the money for pistons and boring the block.

But at the second look I think its worth the money also to be able to use modern 135mm rods which are also lighter.

The rotating mass with the light pistons and rods should also be an big advantage. I think the best way would be also to lighten the 84mm crank mass to fit the weight of pistons and rods and balance the rotating assambly.

Do you maybe have some information about this how much weight should be took of the crank?

I think the mahle motorsports pistons are the best way for an allround engine.
As im really interrested in technical stuff it would be really nice if you could mail me some pics and data of the pistons.

I will pm you my address. Thanks

[digger]

JE will do a 4032 alloy piston for 885 for whatever crank you want. They have the oe dome profiles for the povo b25 and the euro higher comp if you go through the right dealer . also you can get bigger bore if you wish. Most piston companies can do the same cp is a good brand to. Wiseco do the MM stuff.
If you have CAD you design your own dome profile to.

[bmwmaster81]

Ok, sounds good.

So do I understand it right, I just have to contact JE and tell them that I want to build an m20 Stroker with:

885 Head
135mm Rods
89.6 Crank
85mm Bore
10:1 CR


and they do the rest and calculate the Dome Design. (Especially the right hollow depth) in the piston crown to reach the right CR?

By the way is it physically possible to build this kind of piston?
This would end up at 3050 ccm.........

[digger]

Topend are a dealer for JE if you go through them they can fix you.

Ask for 4032 alloy give them bore, stroke, rod length, gasket thickness, cam etc. I recommend total seal rings (either conventional or gapless top)

if they use the 8:8:1 dome style from an OEM piston that will get you the right number +/-

this is assuming you are using a 885 head

[SkiFree]

If you want the same features then make sure you ask for the slipper-skirt design, the coatings, and be sure the dish is the correct offset (the blank that JE and others sometime use is slightly off). Just be best to ask for a photo before committing.

[LateFan]

It is much easier to make a big-number race piston than a well-rounded efficient street-focused power piston. With larger strokes the wrist pin begins to encroach on the lower oil-control ring of a healthily-specced ring package, necessitating an support ring.

Interesting on a all-around use design.

And are you saying (#1) the rod could swing far enough that it might hit the skirt where the ring land is? I'm not understanding that - isn't the bottom land always above the wrist pin bore? Or are you saying (#2) the pin diameter is getting larger and encroaching on the bottom land?

...still trying to see this in my head...or is it (#3) the actual pin location is changing relative to the top of the piston depending on stroke and CR?

[zaq123]

Interesting on a all-around use design.

And are you saying (#1) the rod could swing far enough that it might hit the skirt where the ring land is? I'm not understanding that - isn't the bottom land always above the wrist pin bore? Or are you saying (#2) the pin diameter is getting larger and encroaching on the bottom land?

...still trying to see this in my head...or is it (#3) the actual pin location is changing relative to the top of the piston depending on stroke and CR?

oil ring falls into the wrist pin bore area hence the need for the support rail...results of piston's short comp. distance. Cons of this design is very debatable

[digger]

If you want the same features then make sure you ask for the slipper-skirt design, the coatings, and be sure the dish is the correct offset (the blank that JE and others sometime use is slightly off). Just be best to ask for a photo before committing.

Je don't do a slipper design in 4032 dont have forgings but it's not big deal. Off set pin is a good idea to help keep things a bit quieter (pretty sure the mm were offset) or conversely reduce friction on an all out motor done by reverse offset.

[digger]

If you're not using a huge cam there is no reason you can't avoid an oil rail with 135 rod and 89.6mm crank you use a 20mm pin ( rebush rods) the land and ring sizes add up last time I checked but you need to talk to the manufacturer

[cdeason7]

This is a piston that TopEnd designed for my engine build (E36 2.8L crankshaft and rods, 885 head,CR 10.7:1, Schrick 280/272 camshaft) using the 4032 forging

[digger]

How recent ? je or cp ?

[cdeason7]

A few months, JE, my engine builder prefers working with JE,
Design look ok ?