I was wondering if you can run LS pistons in a B16 engine with B16 rods and crank? Buddy of mine has an extra set, Ive got fresh rings laying around. Also being that they would lower the compression, which is good for my turbo setup. high compression is what killed my other pistons


Modified by all_motorsi at 7:19 PM 6/9/2008

 

People do it all the time. I've got a motor on a stand in my shop that I built like that, just haven't gotten around to dropping it in a car yet. I've heard that the valve reliefs in the PR4 pistons are a bit small, so don't run big cams on it, I was just going to run GSR cams.

 

thats my exact setup 333whp on 91 octane no problem, just enlarge the valve reliefs if you plan to run anything bigger than b16a cams.

here is a pic of mine:





im using type R cams with a .050 head gasket, valves were hitting the intake side of the piston so we enlarged the valve reliefs on the intake side, for stock CTR cams you dont need to enlarge the exhaust side only the intake.

keep in mind i had stock cam gears, i dunno if adjustable cam gears play a roll or not.


Modified by blinx9900 at 4:55 AM 6/10/2008

 

Good info, I have JDM GSR cams running 2deg of advance on the exhaust, so the exhaust closes earlier for less overlap. When machining the valve reliefs, do you need to weigh the pistons afterwards to ensure that they all balance out or just play it by ear? thx guys

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by all_motorsi &raquo;</TD></TR><TR><TD CLASS="quote"> When machining the valve reliefs, do you need to weigh the pistons afterwards to ensure that they all balance out or just play it by ear? thx guys</TD></TR></TABLE>

who said anything about machining? i guess yeah, we used a dremel tool lol, as far as balancing, nope. but my guy has been dong this sort of ish for years so i trust him, if your doing it yourself thats another story.

 

could you just run gsr slugs and not worry about the valve reliefs? its gotta cost the same, and the compression couldnt be that different.

 

There's over 2.5cc's of difference; that's why people want to run the PR4's in the first place.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by rmcdaniels &raquo;</TD></TR><TR><TD CLASS="quote">There's over 2.5cc's of difference; that's why people want to run the PR4's in the first place.</TD></TR></TABLE>

im stupid when it comes to piston measurements, i went with pr4's due to the low compression, is that what your referring too when you refer to cc?

 

Yeah, I cheat and use the c-speed calculator, it's mostly correct as far as I've checked the math on it:

http://www.c-speedracing.com/h...c.php

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by rmcdaniels &raquo;</TD></TR><TR><TD CLASS="quote">Yeah, I cheat and use the c-speed calculator, it's mostly correct as far as I've checked the math on it:

http://www.c-speedracing.com/h...c.php</TD></TR></TABLE>

lol, me too, i prefer the zealautowerks one, its finally back up

 

LS pistons= 8.38:1 compression with my .04 headgasket... too low? ugh i want to keep my MPG! anyone got USDM P72 slugs for sale cheap?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by all_motorsi &raquo;</TD></TR><TR><TD CLASS="quote">LS pistons= 8.38:1 compression with my .04 headgasket... too low? ugh i want to keep my MPG! anyone got USDM P72 slugs for sale cheap?</TD></TR></TABLE>

you'll be fine, i have them with a .050 headgasket which puts me right at 8.3 no problems here

 

super low comp b16's are trash.
i would run the p72's before the pr4's

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by .CUBISH. &raquo;</TD></TR><TR><TD CLASS="quote">super low comp b16's are trash.
i would run the p72's before the pr4's</TD></TR></TABLE>

X2. Really low comp and small displacement is going to suck. Stock b16 comp ration is around 10:1 right? Why not just boost on that?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by .CUBISH. &raquo;</TD></TR><TR><TD CLASS="quote">super low comp b16's are trash.
i would run the p72's before the pr4's</TD></TR></TABLE>

please explain, this is a tech forum, your emotions and feelings that they suck mean nothing, i happen to have a low compression b16 and i love it! if you cant back up your opinion with tech info please dont post it.

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

X2. Really low comp and small displacement is going to suck. Stock b16 comp ration is around 10:1 right? Why not just boost on that?</TD></TR></TABLE>

its actually 10.4, and to answer your question its cause you cant make 350-400 with 91 octane and 10.4:1 compression. see above, that goes for you too.

 

My 8.4:1 B16 making 408 WHP didn't suck, it was a whole lot of fun.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by rmcdaniels &raquo;</TD></TR><TR><TD CLASS="quote">My 8.4:1 B16 making 408 WHP didn't suck, it was a whole lot of fun.</TD></TR></TABLE>

amen, my 8.3:1 b16 is making 333whp on 91octane at 12psi gt3076 with room for more. compression is only part of the puzzle, and people who think there is a world of difference with the extra 200cc a gsr gives you, well its not that major, its just another piece of the puzzle as well.

 

i had an 8:1 b16..
60-1 etc made 360hp on 18 psi

same setup with 10 to 1 made the same power on 12.5 psi

put the same exact turbo setup on my current motor. 81.5mm lsvtec 10 to 1 made 375hp on 9.5 psi and 520hp on 20 psi

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by blinx9900 &raquo;</TD></TR><TR><TD CLASS="quote">
its actually 10.4, and to answer your question its cause you cant make 350-400 with 91 octane and 10.4:1 compression. see above, that goes for you too.</TD></TR></TABLE>

Who told you you cant make that power on 91? I am making 425whp on 91 and i'm around 10:1. A good tuner should be able to break 350whp on 91 with stock b16 comp ratio very easily. Oh, and according to the zealautoworks calculator a b16 is 10.28:1

The point I am trying to make here is why go that low of comp ratio if your only trying to make &lt;400whp.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by .CUBISH. &raquo;</TD></TR><TR><TD CLASS="quote">i had an 8:1 b16..
60-1 etc made 360hp on 18 psi

same setup with 10 to 1 made the same power on 12.5 psi

put the same exact turbo setup on my current motor. 81.5mm lsvtec 10 to 1 made 375hp on 9.5 psi and 520hp on 20 psi </TD></TR></TABLE>

was your tuner familiar with tuning engines with compression that low? cause its totally different, we had a lot of problems at first and then we realized we could through A LOT more timing at it and lean it out to 12.5 and it made all the difference in the world, its a shame it didnt work out for you, unfortunately high compression turbo didnt work out for me

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

Who told you you cant make that power on 91? I am making 425whp on 91 and i'm around 10:1. A good tuner should be able to break 350whp on 91 with stock b16 comp ratio very easily. Oh, and according to the zealautoworks calculator a b16 is 10.28:1

The point I am trying to make here is why go that low of comp ratio if your only trying to make &lt;400whp. </TD></TR></TABLE>
are you making that much power with cast pistons? i have cast pistons, thats why i went so low, i wanted that safety, that margin of error.

 

I agree with both schools of thought here... high compression motor is going to be more responsive out of boost but requires very careful tuning in boost and consistent fuel quality. as far as 20PSI at 10:1 compression... you are insane, props, I'm assuming that was made with C16 or some very high octane fuel. what kind of AFR's and total advance numbers (@boost in VTEC) are you tuned/running with?

Low compression motor is generally safer and less prone to DAMAGE, allows you to use more ignition advance and lean out the fuel more while staying more resistant to detonation regardless of subtle tuning errors or the occasional low fuel light racing. In a perfect world high compression turbo motors would pwn all but with the price of race gas and lack of good tuners its just not thesiable for everyone.

I ran my stock internals 10.4:1 B16a @ 8PSI tuned by myself without a hiccup for a month running away from 13.5sec cars like nothin having traction problems through 2nd and 3rd gear. 11.8AFR's and 17-22deg total advance.
One lazy sunday morning race, I was allmost out of gas (stupid) and i blew all 4 ring lands on the PR3 pistons. luckly i turned it off when i noticed the valve cover pouring white smoke and didn't damage my sleeves at all, but the pistons are a complete loss. All my money is going towards my other LS/VTEC-TURBO build so im just looking for a cheap immediate and local-sourced-parts solution to get my b16 running before monday so i can drive it to work, lol. Picked up the LS slugs and JE-proseal rings LOCAL for $100 so i am going to throw them into the B16a and hope for success. If i remove the middle layer from the .040 headgasket I will bump it up from 8.38 to 8.77 compression which is a lil better... IMO a stock rod-piston B16 is more reliable with the factory cast pistons at a lower compression (like the PR-4 or usdmP-72), and will make more power with more boost more safely. downfall is the f(&$% fuel economy of low compression motors. fack, i will miss my 34mpg

 

need a link to aftermarket pr4 pistons for my b16. had one and lost it.

 

hey i know these post are a few years back but i was wondering what kind of numbers you were getting out of it after you put the motor back togather

any info on this woud be great thanks.

 

2 year old bump....lol