<FONT SIZE="12"><u><FONT COLOR="orange">15 CC bitches</FONT></u></FONT>

i was contracted to help make a custom d16 rod for vitara setups in d16
its common knowledge that they sit in the hole on d16 setups a ways down.
so hopefully we will have some new rods out soon that bring it up for a bump in compression...
however part of this project was to be sure we were spreading good info about the expected compression ratio so we had to do a dish volume measurement.
there are many posted specs around the net over a wide range.
from 8cc on up to tuner.toys misrepresented spec up over 17cc.
the problem with tuner toys spec is they did the measurement in the block.
and since they sit in the hole...
they were adding in all the volume from the deck down to the piston top before you even start adding in the dish
also they weren't sure if block had ever been resurfaced.
regardless...this needed to be cleared up.

so i got the set of standard bore ycp vitara pistons in the mail and went to work
picked up a ring compressor and some clear small cutting boards and a big C.clamp.
i decided to use some brake fluid to avoid the meniscus of water...



first problem was leakage...and lots of it...
it was leaking through a small gap where the metal overlaps on the ring compressor


so i got some gasket sealer and gooped up the ring land
re tightened and let sit for a day
when i came back to retry i started pusihg oil out the edge where it mates with the clear plastic
my hole wasn't big enough and it was pressurizing the dish
i melted open the hole some more and cleaned up the bottom surface to keep it flat.
it was still leaking around the edge of the ring compressor
this was proving to be a pesky project
i decided to use water because it was a thinner fluid
i also upgraded to a 10cc syringe because the 3cc had to be used multiple times which increased error probability in the measurement.
the water proved well....it reduced the overall pressure and i started to narrow in on the spec....
and it was becoming very apparent that it was much deeper than most of the online calculators were saying.
consistently i was getting over 14cc...and as high as 16cc
but i still had some leakage and air bubbles.
i tightened down the clamp and it was starting to crack the plastic



i made the hole bigger and the air was able to come out of the dish much easier.
didn't have much of a pressure problem anymore
it would still leak a little...and a tiny air bubble or two would get caught in the valve relief areas...
it became very apparent the dish is over 15cc
i did about 10 measurements all pretty effective
the best one was at roughly 15.3cc
the system held enough pressure using water that i do not believe the meniscus affected the measurement at all

i am still going to do more to lock in the number
you can expect it over 15cc for sure and less than 16.

what does this mean...?
well for one...on stock 137mm rods the basic vitara build w/ a z6 head sits at 7.5:1 compression
and only a little better using a y8 head
very surprising indeed...but also interesting that noone seemed to even think it might have been this low.
why...?
many people say they run fairly quick n/a...nothing that much slower than stock.
i'll leave that to the most knowledgeable to explain.
but its of my opinion that dish pistons make power
more of an expanding flame front reaches more of the piston at the same time.
and if we bring in all the 400+ hp successful vitara builds out on the streets today.
the extremely low compression allows for gobs of timing on the boost.

so it shouldn't be frowned upon with this much success already as a proven setup.
the rod build should still go through...
and we can expect to have available a bump up to 8.0:1 cr from the current.
these are just estimates of course...but you get the idea.

also worthy to note for anyone doing calculations
strait off the ycp vitara spec sheet the compression height is measured at 28.3 mm (± 0.1)
and i believe oem vitara pistons were measured at 28.2 comp height.

and lastly i will leave a piston picture comparison
if you look at these long enough you see its pretty apparent of the relative size of the vitara dish

pistons from top:
stock z6 p28 : 10.1cc
ycp vitara : 15.0cc
stock vx p07 : 16.1cc

(credit to heeltoeauto for the stock piston pics)

 

well i just did 10 measurements with 70% rubbing alcohol
alcohol had some kind of miniscus...so i measured from the bottom of that each time.
15cc every measurement on the nose
the syringe is in 0.2cc measurements...so its pretty accurate

i used a new part of the plastic with no cracks and made a new hole
i was already using the angle idea to keep air by the fill hole and continued to do so

it looks like a solid measurement at 15cc
and that is what i'm going to hold out on

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input / feedback makes the world go round
if anyone has any problems with my methods please speak up

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<FONT SIZE="12"><u><FONT COLOR="orange">15 CC bitches</FONT></u></FONT>

 

tough crowd

 

maybe post in FI as well? sohc thread?

 

This is good trivia knowledge, but at the end of the day the guys who usually run vitara pistons don't really care about stuff like this.

Thank you though, this makes calc'ing different head/block combos a lot more accurate.

 

new rods are out...
they look beautiful
contact FJT

shorter for d15 builds
longer for d16 builds
usdm d15 rods hopefully by summer
for now d15 rods only fit the 45mm jdm crank