EVO 9 Piston

[MaxAttack]

I have posted an image of the EVO 8 piston compared to the EVO 9.
There have been a few comments regarding the EVO 9 having only
2 piston rings. As you can see, it does have 3 rings as most production engines do.
However, the EVO 9 piston does incorporate a hydrostatic groove between
the first and second ring to aid in sealing and reduce friction.


Regards,
Ken

[Terry S]

I have posted an image of the EVO 8 piston compared to the EVO 9.
There have been a few comments regarding the EVO 9 having only
2 piston rings. As you can see, it does have 3 rings as most production engines do.
However, the EVO 9 piston does incorporate a hydrostatic groove between
the first and second ring to aid in sealing and reduce friction.


Regards,
Ken


Maybe this is why the Evo 9's seem to be more consistent (car to car and run to run) in their dyno numbers than the 8's?

Good find. O0

Terry S

[KawRider]

I have posted an image of the EVO 8 piston compared to the EVO 9.
There have been a few comments regarding the EVO 9 having only
2 piston rings. As you can see, it does have 3 rings as most production engines do.
However, the EVO 9 piston does incorporate a hydrostatic groove between
the first and second ring to aid in sealing and reduce friction.


Regards,
Ken


Maybe this is why the Evo 9's seem to be more consistent (car to car and run to run) in their dyno numbers than the 8's?

Good find.* O0

Terry S


Good point. Mine was super consistent ) within a few HP/TQE between dyno pulls.

[groundPork]

Is hydro-static the way Cosworth refers to that groove? In most piston applications it is intended to provide a low pressure reservoir to prevent gasses that bypass the top ring from creating enough pressure below the ring to lift it from its ring land and thus break the seal. This ring flutter simply put. I usually hear it refered to as a gas accumulator groove, judging by its actual function is what makes me question whether or not Cosworth in fact referred to it as a hydro-static groove... hydro would indicate fluid right?... hmmm just curious. :roll: :roll:

[Skiracer]

Here's a thread about this topic: http://www.socalevo.net/forum/index.php?topic=15857.0

[Myevo8]

Interesting thread. Coolguy's thought a maybe some larger turbo would be nice to have O0

[groundPork]

I had a chance to look at the pics you posted and I think I know what i might be missunderstanding about the label of "hydrostatic". I believe they are refereing not to the channel machined into the face of the second ring land, but the hollow channel cast immidiately behind the entire ring stack. This is from acutally first hand confirmation from various piston manufacturers... The channel is there to allow heat from the top outter most portions of the piston, and the top ring itself to dissapate. The heat accumulated during exposure to combustion process, heat from this process generally moves through the top ring to the cylinderwall and eventually the coolant. By adding this channel, the chances of protecting the top ring from annealing, or butting the ends are far better, as the channel can trap oil sling in it's interior and circulate it behind the ring grooves. This has been done for many years wit diesel pistons. If you flip it over you'll notice not only one or two holes which are the entry to the channel, but that the channel seems to run totally unobrtucted behind the ring stack.

There are so many different tricks used over the years by piston manufacturers, and it amazes me at how we as import guys are now just seeing this stuff. Hang around with old V8 guys, an you can learn a few things!.. And not all of them work. Nice thing is, we've got the advantage of open mindedness... right guys?... Right?.... Or not, what ever. hahaha!

[trinydex]

^ funny guy