ive been pondering piston selection for my 1595 build and was dead set on PCT which would give me 11.5:1 with plenty of valve clearance. however i just read that higher domes have adverse effects in the combustion chamber especially during overlap. i cant remember the exact way it was worded. it said the optimal dome is no dome at all however sometimes you cant quite get high enough compression with no dome. obviously. so, having read that...

would it not be better to use a p30 piston with its smaller dome, mill the head .035, and have the piston modified for valve clearance to get to 11.5:1

rather than

use a PCT, with its super high done, and leave the head alone to get o 11.5:1

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by CRXofPain &raquo;</TD></TR><TR><TD CLASS="quote">ive been pondering piston selection for my 1595 build and was dead set on PCT which would give me 11.5:1 with plenty of valve clearance. however i just read that higher domes have adverse effects in the combustion chamber especially during overlap. i cant remember the exact way it was worded. it said the optimal dome is no dome at all however sometimes you cant quite get high enough compression with no dome. obviously. so, having read that...

would it not be better to use a p30 piston with its smaller dome, mill the head .035, and have the piston modified for valve clearance to get to 11.5:1

rather than

use a PCT, with its super high done, and leave the head alone to get o 11.5:1

</TD></TR></TABLE>
good question..I want to know too

Your talking about flame travel..For example:

Lets say you have two B16A's with identical parts exept for the pistons. One has a bigger dome/CTR piston and the other a smaller dome/P30 piston.... They have equal compression (the P30 piston engine was compromised with milling and headgasket thickness) for the added compression.. With that being said, Fully tuned, will The P30 piston engine have a better flame travel cause of the smaller dome equaling more power? ?

I have seen plenty B16A's with CTR pistons make decent power...But i have also seen stock Pr3/p30 B16A's making nice power...what gives..


we need some solid proven input here

 

jdm ITR has a more efficient dome design than both of those pistons

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 1.6i &raquo;</TD></TR><TR><TD CLASS="quote">
Your talking about flame travel...
</TD></TR></TABLE>
que mamon...your a flamer and you travel everywhere

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by civdx94 &raquo;</TD></TR><TR><TD CLASS="quote">jdm ITR has a more efficient dome design than both of those pistons</TD></TR></TABLE>

Explain

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by GUILOTINE &raquo;</TD></TR><TR><TD CLASS="quote">
que mamon...your a flamer and you travel everywhere </TD></TR></TABLE>

LOL

 

the bigger the bore, the flatter the piston can be. example stock gsr bore w/ -.6 dome will have a cr of ~10.1, but if you overbore to something like 86 w/ the same dome volume, you get something closer to 11.1

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by HondaIntegraR &raquo;</TD></TR><TR><TD CLASS="quote">the bigger the bore, the flatter the piston can be. example stock gsr bore w/ -.6 dome will have a cr of ~10.1, but if you overbore to something like 86 w/ the same dome volume, you get something closer to 11.1</TD></TR></TABLE>
Yeah for sure..


But we're talking about a B16A with stock sleeves, and trying to compare PCT slugs VS P30 slugs power output on an identical engine with identical compression...

 

hondas dont care... stuff the biggest dome you can fit in there

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JDogg &raquo;</TD></TR><TR><TD CLASS="quote">hondas dont care... stuff the biggest dome you can fit in there</TD></TR></TABLE>

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JDogg &raquo;</TD></TR><TR><TD CLASS="quote">hondas dont care... stuff the biggest dome you can fit in there</TD></TR></TABLE>

wrong.

i went and found the litertature. it reads:
" a good idea is to keep the dome as flat as possible as too high a dome can hamper flame travel, chamber scavenging on overlap and cuase unstable combustion, which can cause detonation and a loss of power. the ideal piston configuration in a perfect world is flat top. this gives the best combustion and minimal surface to volume for good thermal efficiency"

SOOO.....

i take from this that the best piston to use would be a modified P30 for valve clearnce since its more flat on top, and milling the head to get the CR you want rather than using a larger dome. so the "ahh **** it just throw a type r in there" mentality is actually costing you power. what i want to know is how much its costing. probably substantial on a head that has a portflow headjob and 5 angle valve job and huge cams.

an insider told me tht the omni 200hp build used this method. i dont know the guy but im sure he could have used any piston he wanted in that build. i wish he would chime in and give a little insight because hes onto something.

 

Also something people always forget is the CTR piston's unusual compression height which causes more clearance issues.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by rjay8604 &raquo;</TD></TR><TR><TD CLASS="quote">Also something people always forget is the CTR piston's unusual compression height which causes more clearance issues. </TD></TR></TABLE>

someone mentioned the tightness on the quench area.

 

keep in mind that this therory held true more so when spark plugs were located off center to the pistons ie v8's from back in the day . The problem was the spark had to travel from the far side of piston (in there cases a big piston ) to the other side , with a dome in the way you could understand the issue here .

Im kinda with jdogg in a way that its no where near as important with newr motors as the spark is coming from right on top of the dome there for gettign to ethier side isnt as difficult as the older engines ...not to mention our bore sizes are alot smaller too begin with

 

its not always about the spark... flatter pistons flow better..

 

so you post asking about it... i KNOW about it and you tell me im wrong. wow

 

need to factor in r-s ratio, cause piston speed (or lack of with low r/s ration) will play a role on how obstrutive the dome is to flametravel.

 

i like flat tops.

that way i can run nitrous later.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by johnzm &raquo;</TD></TR><TR><TD CLASS="quote">i like flat tops.

that way i can run nitrous later.

</TD></TR></TABLE>

why won't you be able to run nos with domes ?

 

becasue they are stock pistons, and i wanna spary 100+

i dont think a ctr piston in a GSR engine would be able to handle 150 shot, altho if someone proved me wrong, maybe id change

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by johnzm &raquo;</TD></TR><TR><TD CLASS="quote">becasue they are stock pistons, and i wanna spary 100+

i dont think a ctr piston in a GSR engine would be able to handle 150 shot, altho if someone proved me wrong, maybe id change</TD></TR></TABLE>

its all about the gas and the timing retard..

oh.. really really cold plugs as well.

 

were you by any chance reading that from some sort of two stroke information? if not machine4321 was probably right, becuase yes, that is the case with a 2 valve head when it has to rush across a 4.250 inch cylinder (108mm) from the far side, although with newer GM heads the plug is much closer to the middle. thats why indexing the plug was so damn important(or so people thought) with these engines. this isn't the case at all with a four valve engine where the plug is right in the middle and there is a hemispherical head

 

hemi?? wtf has a hemispherical head?

 

no i read it in a honda engine building guide by mike kojima. and id be willing to bet he took a lot of his knowledge from paulus lee and darren san angelo.

ALSO, i just found that omnis 200hp b16 uses the smallest dome of all, the PR3 piston
InterTuneTv: no he used pr3s
InterTuneTv: if you look on the video
GTIVr6ofPain: flatter dome for better flame travel?
InterTuneTv: he likes a flatter dome and a small chamber
GTIVr6ofPain: he'd rather mill the head to get the CR than raise the dome huh
InterTuneTv: yes
GTIVr6ofPain: better flame travel
InterTuneTv: it also increases the velocity a bit

there it is.
not tryin to tell anyone they are right or wrong. just want whats gonna make more power.

 

i also prefer the pr3 piston, but not because of the small dome

but the fact that it weighs a significant ammount less than the pct pistons.

the relitivly small bore of hondas and a decent chamber design means it dosnt matter. you dont think any prostock guys are running flat top pistons do you.. they stuff the chamber full of dome

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by CHEETAH &raquo;</TD></TR><TR><TD CLASS="quote">need to factor in r-s ratio, cause piston speed (or lack of with low r/s ration) will play a role on how obstrutive the dome is to flametravel.</TD></TR></TABLE>

ditto.


I went with JDM ITR pistons on my B16 build. I milled the block .010" and the head .038". The ITR pistons with less dome than PR3 or P30 pistons, ended up have a higher comperssion height. The quenches ended up being out of the hole by about .010-.015". I had to run a thick Cometic headgasket to ensure proper clearances.

The engine ran damn good, and compression ratio was around 11.7-8:1.

Also, I believe that the angle to which the valve sets has an affect on the ole piston dome theory.