Why do you N/A guys get forged pistons over the factory psitons? Please someone explain to me what a forged piston offers that ctr or itr piston doesn't?

 

Larger bore size. Factory pistons are only available up to .25mm oversized.

 

ok good point, but let's assume 81mmCTR/ITR VS 81mm Forged

 

better heat tolerance, possibly allowing for maybe better rings or differently setup ring lands, another reason maybe to run higher compression

 

Stronger Piston .. can take more abuse ... ummm Raise compression ... can buy oversized ones .. if you bore your cylinders ... different dish/dome types ? like Flattop ect..

 

Those are the ones who have too much money to spend. I have to build my car on a budget.
But seriously, there are more different types (bore and compression wise) with forged pistons versus factory pistons. But they are more expensive than factory.

 

First off anyone over 81.5mm have to go with forged...

The reasons I am going with forged

- Lighter (rev easier, less wear on everything)
- Retain much less heat (less prone to detonation, can run slightly higher CRs)
- Stronger (always better)
- More specific choices of compression ratios
- Bigger valve reliefs

Here are some random tidbits of information...

 

You can achieve a wide range of compression ratios by mixing and matching OEM Honda pistons (and/or heads where cost effective and design allowed).

Altho, depending on the combination, you're pretty much limited to 12.0:1 using OEM Honda stuff. If you need to a lot higher than that (even further than milling & a thinner headgasket will get you), your only options are aftermarket forged pistons.

I don't know all that much about all the detailed rules racing sanctioning bodies and their classes, but I don't think there are any classes that restrict you to original bore and stroke while allowing you to change the internals for non-original pieces, without throwing you into the next class up. I could be wrong on this. So, if you are going to use forged pistons, you might as well be sleeving and overboring while you're at it.

If you're not racing, then you don't have to worry about this. Instead, you'll need to consider the cost-effectiveness of the advantages of using forged pistons in the std 81mm bore for a NA application. Since you can hit almost any "streetable" compression ratio using OEM Honda pistons (which are half the cost of forged ones) and the other benefits (ie: ring land strength and ring placement) are pretty much negligible for non-racing application, I think it's a no-brainer on which ones to use.

 

basically for 81mm or 81.25mm on a street car i would just use oem honda pistons. as mentioned before there half the cost and you can get anything 12:1 and under. and R piston comes with a molly coating too so there pretty good on a budget.. however for a serious build (by serious i mean 12:1 +, 81.5mm + or 9k+ ) i would say forged. CR and bore are obvious cause thats the max you can go with oem but when you start revvin high weight matters and forged = lighter. also forged will dissapate heat faster as well. i say for the average person that just wants a bump of power to match some R cams or maybe stage 1 skunks/ toda a's oem is fine but beyond that forged becomes important.

 

that pretty much sums it up...
and for those who think milling and decking are a way to up the compression i hope your not running a real set of cams:
jun 3, skunk stage 3, toda c+d's need stock height heads for you to sleep at night

 

i've always wondered... why does Honda sell overbored pistons? woudln't they want all replacement parts (as that is what they are) to be the same?

 

You can barely even call a .25mm overbore an overbore.

Honda made them available to account for situations where the engine would have to be rebuilt without having to replace the cylinder sleeves, which is a lot more expensive than just replacing a set of pistons.

 

 

Has anyone seen the forged ITR pistons, no their not made by honda.

 

I believe the pistons you are talking about are made by probe ind paste......Personaly I have yet to see a piston with as tight a clearance as factory..For 81 mm and N/A I can't imagine a better piston than ctr

 

Nice chart. I have always wondered about this.

 

deeper valve groves
better performance
variety of compression and bores

-Brian

 

i would say high heat handling, the pistons are a harder material, and they do allow for many more ranges of compression.