Just wondering if anybody is running CTR pistons in their LS/VTEC and having problems tuning?

I noticed the CTR's will put you at or near 13:1, pushing the limits of even 94 octane. Is it possible to simply run a thicker HG to drop the CR to something more tuneable?

tia

 

i use to drive on cali pump gas for daily driving with a little retarded timing .....on race day i would ad maybe 2 gallons or so of 100 octane ....it ran great other than that

 

Why do it in the first place. Just use P30 pistons instead, not only are they lighter but the compression would be in the 11+'s area and right around perfect pump gas zone.

 

well this was almost 2 years ago........it was harder to make nearly 220 hp on a 1.8
the technology now makes is a lot easily to make good hp on pump gas

 

Car ran great back home in AZ with 91 pump, now I'm running 93 pump here in NC... Timing is at stock too.

No way it puts you near 13:1, no way in hell..

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by LSVTEC 91 Civic &raquo;</TD></TR><TR><TD CLASS="quote">No way it puts you near 13:1, no way in hell.. </TD></TR></TABLE>
yes way in hell.....https://honda-tech.com/zerothread?id=717928
89mm stroke 81 or 81.25mm bore and a b16 or gsr head and the CR falls between 12.6 and 13.3

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by thevanitygroup &raquo;</TD></TR><TR><TD CLASS="quote">Why do it in the first place. Just use P30 pistons instead, not only are they lighter but the compression would be in the 11+'s area and right around perfect pump gas zone.</TD></TR></TABLE>
what he said.

 

12.8:1 here

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by thevanitygroup &raquo;</TD></TR><TR><TD CLASS="quote">Why do it in the first place. Just use P30 pistons instead, not only are they lighter but the compression would be in the 11+'s area and right around perfect pump gas zone.</TD></TR></TABLE>

This is exactly what I was debating.... CTR's vs. P30's. Would bumping the CR with a slightly thinner HG be a good idea if using P30s?

 

P30's are always better That being said if you want more compression than they provide, milling, flat valves and thin gaskets are always options. I dont think you will find a scenario where with the same setup with the same compression (P30's with head milled OR CTR just installed) where the motor with the CTR's will make more power. P30's are lighter, flatter (better vapor flow and chamber combustion) and fit to rods without shaving. I think the choice is clear.

 

double posts are gay.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by thevanitygroup &raquo;</TD></TR><TR><TD CLASS="quote">P30's are always better That being said if you want more compression than they provide, milling, flat valves and thin gaskets are always options. I dont think you will find a scenario where with the same setup with the same compression (P30's with head milled OR CTR just installed) where the motor with the CTR's will make more power. P30's are lighter, flatter (better vapor flow and chamber combustion) and fit to rods without shaving. I think the choice is clear.</TD></TR></TABLE>


well not bs but....i say

get the CTR's because you can always run more aggressive cams down the line, or even mill your head more, and get flat valves to run race gas only. ctr pistons bring you the border line compression between street and full race. i say pct's because you can still be street able with some lopey cams on 93 octane. 93 is fine as long as you're tuned. if you're not tuned, you shouldnt be beating on the motor anyway.

 

i run cali 91 on 12.7:1 with ctr's....those who say it cant be done just dont know
there is also certain version's of the corvette that come stock with 12.5:1 and use 91....its all in the tuning
for another crazy reference my scion xb has 10.5:1 and runs on 87....

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 97L-esVeeTeg &raquo;</TD></TR><TR><TD CLASS="quote">yes way in hell.....https://honda-tech.com/zerothread?id=717928
89mm stroke 81 or 81.25mm bore and a b16 or gsr head and the CR falls between 12.6 and 13.3</TD></TR></TABLE>

Okay, if I was TRULY running that kind of compression, I wouldn't have ran well on 91 octane... Right now I'm running 93 octane @ 16 Deg BTDC... Wouldn't happen with that high of compression.

 

hell what dont u get !?? yes you are running that high compression, everyone used to think it was 11.8 compression or something when no one knew jack! but the truth is out CTRs in a gsr longblock is a whopping 13:1+

 

run a thicker head gasket..

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by chameleon &raquo;</TD></TR><TR><TD CLASS="quote">hell what dont u get !?? yes you are running that high compression, everyone used to think it was 11.8 compression or something when no one knew jack! but the truth is out CTRs in a gsr longblock is a whopping 13:1+</TD></TR></TABLE>

read rookie https://honda-tech.com/zerothread?id=717928 only way your getting up to 13:1 is in a ls/vtec setup due to the longer stroke...

stock b16a with ctr pistons
cyl vol. 398.6cc
head Gasket 2.8cc
piston dome vol. 6.3cc big vol= 436.8
camber vol. 44cc small vol= 38.2 stock b16a=11.43
deck height .5mm+ 2.3cc

stock type-r motor with ctr pistons
head Gasket 2.8cc big vol= 488.3cc
piston dome vol. 6.3cc small vol= 39.2cc stock type-r=12.45
camber vol. 44cc
deck height .25mm 1.3cc
cyl vol. 449.1cc

lsvtec with b16 head and ctr pistons
head Gasket 2.8cc big vol= 497.6cc
piston dome vol. 6.3cc small vol= 39.2cc stock lsvtec=12.7
camber vol. 44cc
deck height .25mm 1.3cc
cyl vol. 458.4cc

lsvtec with gsr head and ctr pistons
head Gasket 2.8cc big vol= 495.6cc
piston dome vol. 6.3cc small vol= 37.2cc stock gsr/lsvtec=13.3
camber vol. 42cc
deck height .25mm 1.3cc
cyl vol. 458.4cc

 

Damn he was off by like .18 or .12...lol

P72 head/B18C Block

STD = 12.924594026551906
.25 OS = 12.989047869209281

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by drchulo &raquo;</TD></TR><TR><TD CLASS="quote">Damn he was off by like .18 or .12...lol

P72 head/B18C Block

STD = 12.924594026551906
.25 OS = 12.989047869209281
</TD></TR></TABLE>

the numbers posted by Altered are not correct...ask omniman what it is
b18c with std pct pistons = 12.524303313624498
b18c with .25 over = 12.584491627641405
b18c with .50 over = 12.64475019280651

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 2k.civic.si &raquo;</TD></TR><TR><TD CLASS="quote">

the numbers posted by Altered are not correct...ask omniman what it is</TD></TR></TABLE>
"All calculated using OEM 3 layer gasket @ .026 and the compression height provided by Omniman"...

 

lol then believe some rookie with a couple hundred posts....i myself can do the math

stock type-r motor with ctr pistons
head Gasket 2.8cc big vol= 488.3cc
piston dome vol. 6.3cc small vol= 39.2cc stock type-r=12.45
camber vol. 44cc
deck height .25mm 1.3cc
cyl vol. 449.1cc
now take that and use the correct cc value for a p73 head since the rest is the same.....nuff said

 

Why does no one get that with P30's he could mill his head into 16.1.1 compression if he wanted to and that what he should really be looking for is a piston with a low dome cc and low physical weight because it WILL make more power than the CTR's at the same compression!

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by thevanitygroup &raquo;</TD></TR><TR><TD CLASS="quote">Why does no one get that with P30's he could mill his head into 16.1.1 compression if he wanted to and that what he should really be looking for is a piston with a low dome cc and low physical weight because it WILL make more power than the CTR's at the same compression!</TD></TR></TABLE> werd...i say go with the P30 as well...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by thevanitygroup &raquo;</TD></TR><TR><TD CLASS="quote">Why does no one get that with P30's he could mill his head into 16.1.1 compression if he wanted to and that what he should really be looking for is a piston with a low dome cc and low physical weight because it WILL make more power than the CTR's at the same compression!</TD></TR></TABLE>

piston to valve clearance is one reason....plus p30's arent coated....so p30's + coating = to much $
one other thing...you can grind a lot of material off the inside of the piston...my ctr's pistons are far from stock weight...and they are all matched to the same weight

for the money pct's cant be beat

also read this https://honda-tech.com/zerothread?id=1088178 it talks about piston dome height and rocket clears it up very nicely....

here is one of rockets many make you think questions
If you had a high dome, would you want to run a
A. High R/S or
B. Lower R/S

Given that you can optimize your engine for either setup.

Hint which set up moves the dome away from the valves quicker to allow for better breathing besides the fact of providing the port a stronger singal?

That was my point. Answer should be clear now. At least in my mind.

 

So lets go through this again then. Why does Omni and many other people that build high HP oem's opt for P30's almost everytime? Why are most of his motors that are bragged about running P30's as well? Why did Omni suggest I replace my PCT pistons in my CTR with P30's? You can change the structure of your pistons all you want, fact of the matter is, at that point your changing the way the piston will respond and react to heat, wear, rpm etc without first working through the change in weight and mass mathmatically. Rocket, who was from what I understand into VW's long ago, im sure he also remembers that all the fast VW guys ran flat and dished pistons just like I did in my 1835 that ran 12's. Point being, I will always opt for the piston that is an unmodified cast or forge from the factory where it was mathmatically tested, r&d'ed and in many cases proven. I will also always opt for the flatest piston possible and the lowest piston weight available, yielding all my compression through getting the head closer to the pistons. That is what I prefer and for good reason.