team2dcrx

Getting ready to rebuild my b16 and was curious on the p2w clearance and ring end gap you guys would recommend when using a cast piston, will be a 15+psi turbo motor~380-400whp/ish. I was thinking factory specs should be alright, but I would like some advice before I take it in. Thanks in advance!!!

KevinEF7

.0035

.018
.02

Hidenplanvew

npr pistons? are they T6 treated?

diatibe24

I am doing the same build and wondering the same thing. And was going to use the same logic as you. I think using factory spec P2W should be fine as long as your upgraded cast pistons are a direct R&R for your OEM pistons. The rings might be a tad different, I am using Hastings for example and they suggest honing with 240 grit as opposed to 400 like OEM says and the end gap for the rings I wanna say they recommend .012 and OEM is .008 (min end gap for top ring).

team2dcrx

yes and yes

blackeg

i would not gap my rings at .012 on a 300-400hp motor. i know they come factory around those gaps but i wouldnt feel comfortable.

my years of wisdom and arrogance combined would say somewhere around .002-.003 for ptw and maybe .020+/- a few thousands for ring gaps with the 2nd ring being about 3-4 thou larger.

anyway ring gap is based off bore size and uses a multiplier that you select based off the type of use, hp, fuel used (e85 runs much cooler etc) the motor will make. the multiplier commonly ranges from .005 to .007+ depending on top or second ring etc. so if you are at 81.5 aka 3.209"x.005=.016 for top ring. bottom ring multiply by like .001 more than the top, so for example 3.209"x.006=.019. now thats on the low side with multipliers imo and those are gaps i would run a nice all motor setup at. a boost setup can be a bit bigger with the multiplier so like maybe .006 and .007 etc. nothing wrong with your gaps being a few thousandtsh big, but there is everything wrong with your gaps being a few thousandths too small...


in a nutshell, i agree with kevinef7

team2dcrx

oh ok, so maybe a couple thousands looser huh, I was kind of thinking it probably wouldn't hurt much and could possibly save them in the long run. I'm gonna over bore mine just to be safe, I lost a ringland and I'm sure the wall is going to be a little scuffed(haven't torn into it yet).

team2dcrx

So is that from experience or just you opinion?

team2dcrx

That's the kind of Awnser I was looking for and I definitely agree!, would rather have them a little looser then tighter(for once in my life) thanks bro I appreciate your response!

boosted94gsr

I'm running Nippon pistons in my build and I went with .016 top ring and .020 on 2nd, don't recall my p2w but I know it's on the looser side of oem specs. I don't have dyno numbers but I'm running 17-18psi from a 5431e turbo with water meth injection. I trapped 119 a while back on 16psi with a less aggressive straight pump gas tune.

KevinEF7

General experience with Hondas building my own motors and for friends over the years. My current motor is set to .0035" , .018 1st .021 2nd Untouched oil control rings and takes 20+psi beating daily on cast pistons and stock sleeves

v8killaz

Do you guys have first hand experience on reliability of these cast pistons. I would think the ring lands cant take more than 400hp but I know my buddy ran them for a bit making way over that. Has since switch to forged though

team2dcrx

that sounds pretty good, do you get a little more blow by with the meth? Not sure if cylinder temps would change enough to notice a difference...

team2dcrx

I've had a couple friends use them, but both where all motor nitrous set-ups, but they have had them for well over a year, and they beat on them regularly. That's kinda one reason why I went this way, but of course price and not having to warm up my car all the time.(since it's a daily)

boosted94gsr

Nope. Just a nice increase in power from more boost and timing.

wantboost

iTrader: (2)

Real Nippon pistons are centrifugally spun hypereutectic castings made with 100% virgin aluminum with higher levels of copper and zinc. This method produces a much stronger, more uniform part. They then put the pistons through a 6 stage heat treatment process which further increases the strength, durability, and service life of the part. As I'm sure you probably already guessed the NPR pistons are much stronger than the OEM pistons.

Dallasb84

Hey want boost. Pm me where you got this info.

wantboost

iTrader: (2)

Found it with a quick google search

Nippon hypereutectic

Someone just did copy and paste from a Nippon document. Unfortunately I don't have time to dig further at the moment because I'm prepping for my deposition that's happening today in a few hours. Hopefully after lunch time I can find the actual document. However I know that's what NPR does because any other casting method would result in a lower strength piston.

Read the random chat thread, I made a huge reply.

Dallasb84

Just seent it!

team2dcrx

Ok so I just got my block back and machinist gave me reading out of the box for my rings. top ring-.019 bottom-.018 and he said my rings are not file to fit rings, anybody ever heard of this? He said it would weaken the structure of the ring... I'm thinking of just taking a little off the bottom ring and going for it. Or should I just order new rings?

ek9_beast

I always stick to the old method of .001 per 100hp. So that would put me at .0035 on this build as kevinef mentioned. Imo, he's correct

Runnerdown

There is no purpose to run such extreme p2w clearance on a piston that will never expand that much. I guess it's not a big deal since most will run only 5-10k before they kill it or sell it.

wantboost

iTrader: (2)

Those ring gaps don't sound even close to right. Most cast pistons don't have p2w built in like forged pistons nor do they expand as much, so going that big is just going to mean a noisy motor almost all the time and possibly power loss as well due to the piston not expanding enough.

Although I also wonder what an appropriate p2w is for the cast nippon pistons since I'm putting an 86mm set in my F22A1, no one really seems to know lol.

ek9_beast

I can tell you I run a p2w clearance of .003 on my 302whp ycp 76mm d16 vitara motor. They are known to sound like a diesel at startup but my bottom end is as quiet as can be. Yup and Nippon are very similar cast Pistons is why I say this.

wantboost

iTrader: (2)

the ones I will be running have coated domes and skirts, so the clearances could be much tighter. Granted at 12:1 static I might run it a little loose to be safe.

Anyone notice the forum skin looks different or am I just retarded? I think a ninja Vbulletin update was done last night or something