2kdrift

Okay so I have had these pistons for a year or so, I was always under the impression that they were about 9.5:1. I pulled my head yesterday, swapping to a type R head. This block has never seen boost and it has about 1k-2k Miles on it.

The reason for this post is to see what you guys think as far as compression Ratio. I have googled the part number problem is I get varying results as far as the specs of the piston I also noticed today that some of the pictures don't match so what I did was take the specs from the listing that actually had a picture that matches exactly what my piston looks like.

I also have attached a picture of my Zeals calculation which puts me at about 10.8:1 (pretty excited about this number) I used a .009 mill in the calc due to my head being resurfaced 2x and block being decked. My machine shop typically cuts about .003 and it all starts to make sense especially because the car has never felt sluggish at all running strictly NA so 10.8 sounds legit.

Do these pistons look to be the correct Design for this compression?
Wiseco pistons
part #: 6542M815

TheShodan

iTrader: (14)

Yep.. Looks about right. Just make sure you change those wrist pins to the S733 if you plan to do some. They cost about $100 or so

2kdrift

Damn I have no plans to pull the block apart not even sure what wrist pins were installed pretty sure they came with the pistons when I purchased them second hand if memory servers correct

*thanks for the info ....Super stoked I was kinda regretting have Low comp(as i thought) this is Great news for me!

TheShodan

iTrader: (14)

You have the S656 pins that are made for NA engines. If you're planning on putting more than 500whp to this build, my suggestion is that you break it down and get those correct wrist pins installed. They use a different pin for the higher compression pistons with the presumption that you're going to run this NA and not turbocharged.

S561, 5115 steel ---- S733, 9310 tool steel.

S733 (Left) vs. S561 (Right).



What happens with higher compression Wisecos when you don't follow my suggestion... If you can see the light, that mean the pin is BENT.



High compression.. has a price.. I already picked up my S733 pins separately, now I'll be able to have my custom Wiseco work with the new build.

*EDIT*.. Found I was wrong, they are 9.3:1 - 10.0:1 compression for these.. But that's for a B16, which is what they were for originally. When you changed the stroke it gets to about 11.0:1.

http://coximport.com/wiseco/wiseco-p.../i-586909.aspx

Here's the wrist pin chart for each piston. Unfortunately, the pistons you got are not on the list.

http://www.wiseco.com/Catalogs/Sport...ccessories.pdf


Good luck with the rest. I hope that you'll get more information as you continue.

2kdrift

Gotcha ....and as always you are 100% right I do vaguely remember the pins at the time of build and they are the thinner wall one that you posted. Definetly not the thicker wall. However it should work for my build Im shooting for about 400 WHP. You probably know which turbo Im running which is rated at 550 HP so I think I should be safe. Again great info If I ever decide to upgrade my turbo ill have to get one of those fancy STC turbos and perhaps and engine Rebuild to some extent.

JRCivic1

I am confused... how does a FLAT TOP piston have a net dome volume of +4.00cc ??? The valve reliefs have a NEGATIVE volume !!! I realize that you are merely posting the data that Wiseco and it's re-sellers are providing, but I suspect that this information is in fact incorrect. If you plug in a USDM ITR piston into your Zeal calculator, it actually has a SMALLER dome volume and a TALLER compression height and it makes just barely over 11:1 compression... and it has a noticeable dome in the middle of the piston. This doesn't add up gang...

Regardless of the compression numbers... I would run it. A 10:1 engine will feel far more lively under part throttle than a 9:1 engine will, and tuning now can provide an exceptional level of safety when combining moderate to high compression and boost together. Enjoy.

TheShodan

iTrader: (14)

For such slight differences, in the end, its rather moot and not worth kicking up a ton of dirt over. I doubt if the reliefs are inaccurate. You have to remember, that Wiseco configures differing compression ranges based upon the engine its exactly using. Not to mention they won't take into account head mill, block, etc. No different than the OEM.

In addition, the question revolved around the compression RANGE that the piston was made for, so that the correct piston wrist pin will be used. For the power level he's looking for, he'll be fine

I appreciate the attention to detail, but its much-ado-about-nothing with these subtle changes in the overall grand scheme. .2CR or .3CR won't make a significant difference applied

2kdrift

Thanks for the assistance. I was really just curious this morning so I called wiseco directly the women I spoke to on the phone was not helpful at all basically told me I had the incorrect part number and made no attempt to help me further. I was quoted 4cc from both Jeggs and from *** import so basically that's the only info I will be able to obtain on this I do agree its a bit of a brain teaser.