swift22

I need confirmation what the exact piston sizes are in mm or IN for the j series...

I got 05 rl O.S. pistons and apparently that would only equate to 89.025??

i thought the stock size was 89.9XXX


Anyways I need a piston that will be as close to 90mm and a similiar stroke to the 3.5RL(05+)


Is the new 3.7MDX have 90mm pistons??


i am building a block right now C-Series and working in conjuction with Acura of Augusta and my block is at machinist right now. HOWEVER if i do not get an answer this weekend then i have to throw the stock pistons back in by may 31st



thanks guys!!

ben

mrsteve

iTrader: (1)

Stock piston size is 89.900

You purchased the oversize pistons which typically are only used if the cylinder walls were damaged and needed cleaned up a little bit, thus increasing the overall volume of the cylinder.

Yes the new MDX has 90.000mm pistons.

mrsteve

iTrader: (1)

I should say though that I'm not sure how large the valve pockets are on the new MDX pistons. That might be an issue unless your machine shop can deal with that.

swift22

thanks man!

SO the MDX is 89.9mm? awesome.

next question unless i can find it.... what it the compression ratio of that motor?

any pics of that particular piston?

swift22

alright it has a 11:1 compression ratio..

so it more than likely is not domed.

cool beans

CleanCL

iTrader: (4)

the new MDX piston will be SLIGHTLY larger bore than the CL-S piston, no more than 1mm. Make sure you hone the cylinders.

p.s. you could also use the regular RL pistons.

CleanCL

iTrader: (4)

stock piston on the CL-S is 89. actually it is 88.9.

stock piston the new MDX is 90, actually 89.9

05+ standard RL piston is 89... 88.9, you get the idea.

also the RL piston will have larger valve reliefs. not sure how big the reliefs will be on the MDX. both RL and MDX carry 11:1 compression. but the RL as i know it has the most aggressive cam than anything out there, the MDX could be a hotter cam, but i dont know any specs on it.

mrsteve

iTrader: (1)

I have no idea either. I found the info on Hondanews

swift22

well the problem is i have a 90mm bore right now..probably 90.01mm

the RL pistons are 89.2 mm.....i got them in O.S. which is only 89.45mm

By the way these are not going in a j-series engine

thanks for all your help. i am going to pull some favors and get a set of MDX to look at and i will take pics for you guys.

thanks.

mrsteve

iTrader: (1)

The MDX pistons are also probably available O.S.

swift22

sweet.

also do can you give me the stroke length of that(mdx) and 05 rl...


I am trying to figure out by boring it slightly how much they increased the stroke by to gain .2L and hoping they did not dish the pistons or move the pin location.

mrsteve

iTrader: (1)

96mm stroke on the MDX

93mm stroke on the RL

CleanCL

iTrader: (4)

i'm guessing you are putting it into the C block? yea, the j32 block should only have an 89mm bore, i guess that's why the RL pistons are too loose. even the OS won't be enough as you figured out. the 07+MDX are 90 and should be work nicely.

btw - the nsx C motor had a couple different bores, i'm guessing you did measure and came up with 90, because they also had 93mm.

swift22

yup. thanks guys. this should help alot.

when i installed the RL pistons i was going to shave the deck anyway...but by doing so made them sit flush which is good. so hopefully the mdx pistons would sit flush.

CleanCL

iTrader: (4)

why are you shaving the deck?

swift22

already have. .5mm It need to upon inspection and also to seat the 05 pistons flush(before i knew the O.S. one wouldn't work)


the main question i have is this...

old mdx had the J35....

07' they increased the bore 1mm and the stroke 3mm....and yet kept the same compression ratio. I am worried that they dished the pistons which would defeat the purpose of what i am trying to do...."boost compression"

CleanCL

iTrader: (4)

judging by all the pictures of pistons i have seen from acura/honda motors, i doubt it. but if thats the case just notch the pistons for larger valve reliefs.

swift22

alright Acura of Augusta is working with me and sent me the new specs on the 07' MDX piston...

pin size is the same. so all that comes next is getting one in hand and checking out the valve reliefs and the dome(or lack there of)