I have searched High and Low for ideas/options/solutions and found only hurdles.

I want to achieve 12-12:5.1 CR in the lighteset fashion possible, exp. lightest rods and pistons.

So far I've narrowed down my rod choice to carillo pro a rods (411-420 grams) and I was lookig into cp pistons as they were one of the lightest piston options I could find.

The problem lied in piston options. CP, as well as nearly every other performance aftermarket piston manufacture, only produces pistons in the 11.0 cr range for a b16A block in std bore sizes.

In order to step up to a limited assortment of 12-12:5.1 piston options, it would require a bore size of anywhere from 84-86mm. That seems a little too much bore for the b16A block. I fear at that bore size that head gaskets become unstable/unreliable.

My questions:

1.) Is it possible to achieve a 12:5.1 cr on a b16A block and head, the way others achieve it in their b18/20 blocks? If so how? Flat faced valves, double/ single layer head gasket, etc?

2.) Is a cr of 12:5.1 beyond the realms of the b16's design/engineering considering I dont want to stroke it, or bore it much over the std bore size.

3.) Can anyone suggest any piston, valve, and headgasket combinations that would put me as close as possible to 12:5.1 cr?

4.) I've heard many suggest that high compression piston options dont exist for the b16A block because of low demand/lack of interest in building these smaller vtec motors. Is this true? If so it may be possible to request a custom piston design that fits my needs. Or do you think that from an engineering standpoint, it would be impossible given the limitations of the b16a's design in standard bore x stroke?

Overall, I'm getting the impression that the reason the higher compression pistons for the b16A are available in bores of 84mm or greater is because the piston cannot be domed any higher to achieve greater compression ratios, due to possible interference with the cylinder head. Thats just an assumption, please feel free to correct me if I'm wrong

Any tips and suggestions would be greatly appreciated. Thanks in advance!!!

 

Most pistons can be custom ordered to any spec you want....for the right price$$$$$ Actually it's only about $100 more for them to machine less of the slug material...

Call the boys at Race Engineering, tell them what you have and what you are looking for. They should be able to set you up. I got a set of 89mm F22A/B Wiseco pistons from them custom cut with a custom compression height for approx $100-$125 above shelf price. Piston manufacturers start with a forged slug of aluminum and machine from there. From what I know about machining, to make some adjustments isn't all that hard. Probably not the first set of 12:1 pistons they have ordered.

 

you can get a set of cp 12.5:1 pistons from cp for the gsr. they should fit in..

 

ctr pistons and a two-layer, high compression head gasket.

 

He said LIGHT PISTONS CTR are not light pistons.

 

Must have skipped over that. why the obsession with the weight?

 

They will fit, but if they are 12.5:1 for a GSR block the CR will be lower on a B16.

 

I would aim for 12.0:1 compression....unless your going to cc the head and the pistons to know actual compression ratio. Your 12.5:1 may end up being much higher then you expected.

 

The highest we can do assuming a 81.5mm bore would be 9.7cc dome. Assuming zero deck that still won't get you anywhere near what you want.

The highest off the shelf piston are made by JE and Wiseco which are both 8.2cc dome.

You are not going to be able to get much more compression without getting bigger bore or more stroke.

 

Im doing a B16A block for my homie right now. He has the 12:1 comp. pistons Cp's but is going to use a B16 head. But if you use a Gsr head it will bump the compression up a tad. I would stay with Oem valves tho. But hey, thats me. I see your in jacksonville too. Have you heard of Don F? DFE? He is on this board also. He can help you with anything you need, and get parts too. Whats your goals for the motor?

 

Look into Mahle. They make 11.6:1 cr 9cc pistons in 81.5mm bore and are fairly light. Remember most manufactures measure the cr with 0.00 piston to deck height.

With those piston, flat valves and a 2 layer you'll be close to what you want

 

Any room to weld the combustion chambers?

 

I know this thread is old but...

Im building a b16 also and came across the same issue. mines been sleeved and bored to 84mm tho. after market beseries pistons are exactly that, they are made to go into any bseries block. if you look at the same bore on say a type-r and a gsr piston with the same c:r the part numbers (most companies) will be the same. when you look up that same part# on a b16 the c:r drops about 1.5pts (ie. 12.5:1 down to 11:1) it doesnt matter what bore. a good tool is a compression calculator www.zealautowerks.com is a good 1. ive heard that it has something to do with pin placement being slightly lower which puts the piston slightly higher into the chamber but that doesnt make any sense why honda would do that and ive never found any proof or measured a b16 piston vs a non bseries b16 piston.

also when we put together my bottom end (im using supertech pistons listed under b20) they sit flush w/the deck so unless when it got sleeved benson decked it and didnt say anything then the pin theory is shot.

 

it's called compression height. look it up.