CP-e Stage 2 pistons compared to stock for some discussion

[jmhinkle]

After Ant had problems with his motor I started to question my build. Luckily I haven't assembled the motor yet so it allowed for some measurements to be taken.

Anyone that has assembled these motors knows the skirts on Wiseco's causes interference with the oil squirters so they have to be bent ever so slightly for clearance. We have two local motors done this way and making big power without issues in Djuosnteisn and Papasmurf. The situation was brought up that the CP-E skirts were even longer on the stage 2 Genpu copy pistons even though they are made by Wiseco. I took some pics and what I see says otherwise.

First, the skirts are no longer than stock from a few different measurements. Overall they are shorter top to bottom seen here:
Gen Juan:


Genpu, which is the longest:


CP-E:


From the bottom of the wrist pin hole to the bottom of the skirt the CP-E pistons are slightly shorter as well. I had to use a flat piece of metal running across the piston to get this measurement then just held it up for pictures.

Gen Juan:


Genpu, longest again:


CP-E:


The stock piston skirts are also the same depth their whole width while the CP-E pistons come down with a wider skirt to start and then taper to the lowest part.

Gen Juan:


Widest part of CP-E:


Narrow part of CP-E:


Realizing I didn't take picture of the side with oil squirter notches, here is the info:

Compared Notches:


Width of Genpu skirt including oil squirter notch:


Width of CP-E including notch:


Width of Genpu notch:


Width of CP-E notch:


Depth of Genpu notch:


Depth of CP-E notch:


Now the big difference

Comparing Genpu bottom of notch to bottom of wrist pin you will see it is about as close to inline as possible:


While the CP-E wrist pin to bottom of notch shows the notch isn't quite as deep:


While that doesn't seem to be an issue it is different. The problem comes with the internal shape that Pablo posted and I still stand by bending the squirters to clear.

The next issue was with clearance for the valves. The CP-E pistons are the same compression ration as stock so they have to have higher areas somewhere to make up for the deep wide Genpu dish copy. This is where some things get questionable to me.

Gen Juan top has small intake valve reliefs and no exhaust reliefs:


Genpu:
Needs pic still

CP-E top. Notice they have much deeper intake valve reliefs, but still no exhaust reliefs:


Top of Gen Juan piston to top of wrist pin hole:


Top of Genpu piston to top of wrist pin hole, oddly enough is shorter than Gen Juan:


Top of CP-E to top of wrist pin hole and they are taller than both here:


Then I measured top of piston to bottom of the wrist pins.
Gen Juan:


Genpu:


CP-E:


I measured the CP-E wrist pin at 22.47 to the Gen Juan at 22.46 to the Genpu at 22.47 like the CP-E. The important thing is that the tops are higher on the CP-E and their are no exhaust valve reliefs. Web was contacted and said that the aggressiveness of the cams, even in the Tomas grind is enough to cause that tiny amount of interference on the exhasut side with these pistons. A larger grind will contact more. Wiseco is going to notch some exhaust valve reliefs for us.

[Payne Racing 67]

@jmhinkle; thanks for making this thread. Smart idea. This should be stickied. Keep us posted. Definitely good/interesting info

Sent from my GS3

[06Speed6]

Man I called it on the skirt being at least oem, I dont have squirter clearance probs on my motor.

I also dont remember my piston looking like yours, but maybe I am remembering wrong.

[SPEED6 KILLAH]

Let me start off saying you can't match up a gen1 piston to cp-e gen2 Style piston.
You will need to have a gen2 oem piston match it up with cp-e piston. As far the exhaust reliefs
you don't need them if you not going with bigger exhaust cams.
As for the oil Squirter you can either bend them back or have a Mech shop take some material off.
The squirter clearance between the piston and the squirter is .005 vs weisco shelf piston with have about .012 something that.

[06Speed6]

And somehow I managed to not get a pic of my pistons but I swear they had exhaust reliefs

[SPEED6 KILLAH]

Originally Posted by 06Speed6 And somehow I managed to not get a pic of my pistons but I swear they had exhaust reliefs

They don't come with exhaust reliefs unless you have there stage 3 piston lol

[jmhinkle]

If you have Stage 2 they should look like these. Only odd thing on mine is I got fucked out of the skirt coating. Everyone else should have the skirt coating on theirs. I was going to get them coated with cerakote locally, but our machinist liked my clearances a lot and said he doesn't think I need the coating at all so I left them alone. Right now, I'm mostly worried that the Stage 2 should have exhaust reliefs in them.

[SPEED6 KILLAH]

Originally Posted by jmhinkle If you have Stage 2 they should look like these. Only odd thing on mine is I got fucked out of the skirt coating. Everyone else should have the skirt coating on theirs. I was going to get them coated with cerakote locally, but our machinist liked my clearances a lot and said he doesn't think I need the coating at all so I left them alone. Right now, I'm mostly worried that the Stage 2 should have exhaust reliefs in them.

I seen couple of cp-e piston with out the coated. But you should get it coated dude trust me as for you machinist say something like that is crazy my op

[djuosnteisn]

The cpe's do have more squish area than oem, and that only increases the likelihood of clearance issues.

And Pablo, he's gonna run the same cams as ant, so that's why he's sweating and measuring everything, lol.

I'll drop a puston off tomorrow joel... (see what i did there...)

[jmhinkle]

Originally Posted by SPEED6 KILLAH Let me start off saying you can't match up a gen1 piston to cp-e gen2 Style piston. Yes you can and that is why I did. If you are raising the height of the outer part of the piston top in relation to the wrist pin, you will create valve clearance issues possibly even with a stock cam. You should know that. These aren't a Genpu copy. They just mimic the dish. You will have to match up a gen2 oem piston with cp-e piston. As far the exhaust reliefs you don't need them if you not going with bigger exhaust cams. I will be matching them to Genpu pistons, as I stated, when I pick it up tomorrow. I can tell you that Genpu has no exhaust reliefs, but again these aren't exact Genpu copies. Don't get confused on that part. Also, I have the same cams as Anthony which can be an even bigger problem. As for the oil Squirter you can either bend them back or have a Mech shop take some material off. They have to be bent no matter what. They aren't in the right place if not bent. Machining will not fix the issue. The squirter clearance between the piston and the squirter is .005 vs weisco shelf piston with have about .012 something that. The ones we had made contact on Wiseco's. Machining would be idiotic.

Answered per line.

[djuosnteisn]

Also pablo, did you post pics of the contact on anthony's pistons? I've been out of the loop lately and missed them if you did. What part of the piston did the valves contact?

[jmhinkle]

Originally Posted by SPEED6 KILLAH I seen couple of cp-e piston with out the coated. But you should get it coated dude trust me as for you machinist say something like that is crazy my op

Coated pistons are quite new and good machinists have been building without them for years. If done right, it's not needed. It's a nice feature and I am pissed that I got fucked out of it, but it isn't needed at all. It's is only a nice to have.

Replacing the diamond crusted washers on the crank and cam bolts is far more important than having skirt coating.

[jmhinkle]

Originally Posted by djuosnteisn Also pablo, did you post pics of the contact on anthony's pistons? I've been out of the loop lately and missed them if you did. What part of the piston did the valves contact?

Here

[djuosnteisn]

Pow.... right in the squisher baby...

If you do end up having reliefs machined in, that's a great pic to show them. It wouldn't take much at all honestly, just a very very subtle dish if anything.

[Tomas]

Stock cams: exhaust valve fully opens 20* before bottom dead center. Or 160* after top dead center. After that it starts closing and at 16* before top dead center it's closed all the way.

216/209 web cams: ex valve fully open 32.5* before bottom dead center or 147.5* after TDC. After that it starts closing and at 3.5* before TDC its fully closed.

Yes, there is a smaller non-interference window with the 209 EX cam but IMO it's still plenty. If the ex valves touch the piston crowns during operation it's probably a problem originating someplace else.
If you deck the block and/or shave the head far enough it could be the ex valves can touch the crowns even when fully closed.

[SPEED6 KILLAH]

Here are some picture of the gen1 piston and gen 2 piston
as you can see the gen 2 side skirt and width is alittle large then the gen1

Note: Look at the side skirt coated you can see some coated on them coating primary intent is to reduce friction and increase
usable power and reduces engine heat







Here is a picture of cp-e gen 2 piston vs oem gen 2
Now what weisco did is went aggressive on the intake side and on the pocket which they had to raise it couple thousand to make up for the CR.

[jmhinkle]

Originally Posted by Tomas Stock cams: exhaust valve fully opens 20* before bottom dead center. Or 160* after top dead center. After that it starts closing and at 16* before top dead center it's closed all the way. 216/209 web cams: ex valve fully open 32.5* before bottom dead center or 147.5* after TDC. After that it starts closing and at 3.5* before TDC its fully closed. Yes, there is a smaller non-interference window with the 209 EX cam but IMO it's still plenty. If the ex valves touch the piston crowns during operation it's probably a problem originating someplace else. If you deck the block and/or shave the head far enough it could be the ex valves can touch the crowns even when fully closed.

I think these pistons are only barely clearing the stock cams. The deeper intake reliefs tells me that the higher tops were an issue on the stock cam as is. With the aftermarket cam the higher tops contact the exhaust side now. Looking at Ant's picture, it looks like a minute amount of contact over a long period of time more than a huge contact in a short period. I think dishing these particular pistons for any aftermarket exhaust cam is entirely neccessary at this point.

[jmhinkle]

Originally Posted by SPEED6 KILLAH Here are some picture of the gen1 piston and gen 2 piston as you can see the gen 2 side skirt and width is alittle large then the gen1 Note: Look at the side skirt coated you can see some coated on them coating primary intent is to reduce friction and increase usable power and reduces engine heat

The coating on the skirts of pistons is strictly for friction. It will hold a thin film of oil that helps with cold start up. That's it. Once the engine is running it isn't doing anything extra at all. It's only starting to come into play on stock pistons and even less on aftermarket ones. Coated tops are where the heat reflection comes in to help with more complete burn from less hot spot issues. We don't have that stock so it's not part of the discussion.

[SPEED6 KILLAH]

Originally Posted by jmhinkle The coating on the skirts of pistons is strictly for friction. It will hold a thin film of oil that helps with cold start up. That's it. Once the engine is running it isn't doing anything extra at all. It's only starting to come into play on stock pistons and even less on aftermarket ones. Coated tops are where the heat reflection comes in to help with more complete burn from less hot spot issues. We don't have that stock so it's not part of the discussion.

Snice this thread is not discussion on piston side skirt coated.
Here something you will be interested cp-e installed check out the clearance bewteen the oil squirter and the piston

[jmhinkle]

Yup, it's the inner design where the problem still lies. That looks like contact in that picture as we saw with normal Wiseco's. The way you guys were talking in Ant's thread made it sound like you were saying the skirts were too long and cutting the tubes off. That is definitely not the case. This is the normal contact due to a different internal shape of the pistons that the tubes were designed for. That's an easy fix with a minor bend. Thanks for that picture. Helps with the skirt discussion greatly.

[SPEED6 KILLAH]

I forgot this picture you can see the marks that oil Squirt left on the piston but didn't break off




Also here is a picture of a off the shelf wiseco piston you can see the Clearance and thickness of the piston side.
[

[jmhinkle]

Original Post updated with interesting Genpu info and other info from Web cams.

[Boosted Beluga]

So say we have a built motor already and decide on bigger cams could we take the pistons out and get exhaust valve reliefs machined? And for good measure get the intake valve reliefs machined out some more?

[06Speed6]

If I send my pistons to Wiseco will they machine them or do I need to find a shop?

[jmhinkle]

Originally Posted by Boosten Ya(josh) So say we have a built motor already and decide on bigger cams could we take the pistons out and get exhaust valve reliefs machined? And for good measure get the intake valve reliefs machined out some more?

If you have the CP-E Stage 2 pistons and get cams you will need to have the exhaust valve reliefs machined in them. The intake side is good with the Tomas grind. I'm not sure how big of an intake cam change would take needing the intake valve reliefs changed as they are fairly large already compared to stock. The only known issue so far is with the exhaust side.

Originally Posted by 06Speed6 If I send my pistons to Wiseco will they machine them or do I need to find a shop?

Wiseco is supposed to take care of it. I don't have the complete details yet. I put in a call at noon my time, 2PM East coat and have not heard back from them. Since it is Friday and 5:20 on the East coast, I probably won't hear back today.

[rfinkle2]

Guys, besides the exhaust valve contact marks on Anthony's piston, is the cross hatching on the crown part of the original machining process?

[jmhinkle]

I don't remember cross hatching on his piston pictures. There was discussion about the cross hatch on his block. If you look at the top of mine in the pic about halfway through the 1st post you seem some machine marks. This is to be expected.

[silvapain]

Originally Posted by rfinkle2 Guys, besides the exhaust valve contact marks on Anthony's piston, is the cross hatching on the crown part of the original machining process?

No. That looks to me like somebody cleaned it up a bit with a pad or something.


Tapadatass

[jmhinkle]

Just looked at the picture again and agree with Silvapain

[Boosted Beluga]

I have cp pistons. Idk of any cuts would need to be made but measurement would need to be required.

I wonder if you could get every aftermarket piston and take measurements.

[jmhinkle]

Are CP pistons like the original Wiseco's and basically a copy of the original stock design? If that is the case then I suspect it buys you a lot of clearance. The CP-E Stage 2 issue comes from mimicking the dish of the Genpu design and having a significantly taller outer crown area than others to keep the correct compression ratio.

If I had each I could add it to the post. It would be nice for comparison. If someone wants to send me the pics of measurements of theirs I can add the data as well.

[Boosted Beluga]

Yes they are

[Payne Racing 67]

Ugh this sucks i have to build a motor in the next few months and now I dont know wtf to do -____- going with carrillo rods but idk what as far as pistons now

Sent from my GS3

[jmhinkle]

Actually you are in good shape now. If you wanted these and are going to run aftermarket cams, just tell them you want them with exhaust reliefs.

[Payne Racing 67]

Originally Posted by jmhinkle Actually you are in good shape now. If you wanted these and are going to run aftermarket cams, just tell them you want them with exhaust reliefs.

Nah im staying stock cams

Sent from my GS3

[jmhinkle]

Then you are fine with any pistons made.

[MarineMazda]

I know the 3 sets of Stage 2 piston that are going in the builds here in Canada did not come with the Skirt Coatings... Maybe CPe has stopped having them produced with this? 1 set was ordered roughly a year ago and the other 2 were this summer.

[BlueStreak]

Is Wiseco being proactive and giving us a little more on the valve reliefs in case more aggressive cams come out in the future? It will save people from having to swap pistons when swapping cams... again...

[jmhinkle]

Originally Posted by MarineMazda I know the 3 sets of Stage 2 piston that are going in the builds here in Canada did not come with the Skirt Coatings... Maybe CPe has stopped having them produced with this? 1 set was ordered roughly a year ago and the other 2 were this summer.

No, just normal false advertising on their part. Great concept of product, fuck the customer in the end is always my experience with them. I wanted mine swapped and they said no.

Originally Posted by BlueStreak Is Wiseco being proactive and giving us a little more on the valve reliefs in case more aggressive cams come out in the future? It will save people from having to swap pistons when swapping cams... again...

Good question. You can probably specify how much you want. I know I'm not going more aggressive than this and will only need minor reliefs. More relief will lower compression since they weren't designed this way. I would only go as much as you are sure you would need.

[ms3blackmica]

Excellent.

Thanks jmhinkle.

@SPEED6 KILLAH; the oil squirter clearance on the off-the-shelf piston you posted is far more suitable