I’m currently in the process of building a JDM B18C. Going all motor with the following setup:

Pulling off the B18C head, and installing a built B16a w/
Crower stage 3 cams
Crower Spring and retainer kit 10,000 rpm
Ferrea Intake, and Exhaust valves (standard)
Skunk2 manifold
JG throttle body
Port, and Polish

All the headwork is being done by Port flow.

My question is what type of pistons should I run. I was told to run JDM ITR pistons. The JDM B18C runs 10.6 compression and so does the USDM Type R so USDM type R pistons would not change the compression…

I would like to run 11.1 compression, but not much higher then that so I’m thinking I have to go with the JDM type R pistons which are 11.1 Anybody have any insight on this? Also what does it mean when there .25 oversize. Does that change the compression as well? InLine4.com told me that I should go with the .25 oversize if the motor has a lot of miles on it or if the cylinder walls are scared.

Any insight would be greatly appreciated.

Also what ¼ mile time can I expect to hit with this type of a setup in a 2000 Si coupe, and what kind of horsepower? I would like to hit mid 13 teens all motor. Low 13 teens would be nice too…

 

First off slapping the PR3 (B16) head on there you will have the same setup as an ITR motor... The PR3 cylinder head has a combustion chamber volume of 42.70cc's where as the P72 (B18C1) has a CCV of 41.60cc's... This is why the GSR head creates a higher C/R with the same pistons... Running JDM GSR (P72-00) pistons will set your C/R ~10.4:1... (At the std. 81.00mm bore there is roughly a 0.2:1 drop in the C/R when going from the P72 to PR3 cylinder head).. That's why the JDM GSR pistons go from a 10.6:1 to ~10.4:1... USDM ITR (P73-A0) will yield the exact same as a USDM ITR... 10.6:1... To achieve your 11.1:1 all you need is JDM ITR (P73-00) slugs... If you wanna go even higher which will not be a problem you still have the USDM B16 (PR3) and JDM B16 (P30) pistons... The highest compression OE piston will still be CTR (PCT)... All of which are possible, just depends on the amount of money you wanna spend... Higher compression ='s more money only because of TUNING which is everything.... 11.5:1+ I would recommend at mininum an aftermarket FPR, injectors, and a fuel controller... (VAFC)... As for the 0.25mm overbore... That is just saying that the overall diameter of the pistons are 81.25mm where the original pistons were an even 81.00mm's... This requires you to bore out the cylinder walls 0.25mm to 81.25mm to accomodate the new oversized pistons... Any good machine shop can do this... Whenever I rebuild a motor I have this done... A block can be honed out which only removes a "tad" bit of material at which time you could get away with standard bore pistons... It's just nice to have brand new clean cylinder walls for your new rings to seat on... Hope this helps and if you need anything else let me know... Peace

 

- for an 11.1 CR JDM itr pistons will give you that, if your going for a built motor i would go with a bit higher CR. 11.1 is good but i would go a couple points higher. the jdm itr pistons have a 5.96 positive piston displacment, mabye you could try a PR3 with a 6.01 positive dome. or even better a p30 with a 6.93 dome displacment. those should all keep you under 12:1 but a little higher than 11.1. just my two cents
- .25 over is like inline four said for when your cylender walls are scored from wear. you get your walls bored out .25 over and use the honda .25 over piston of your choice.
- as far as 1/4 mile, mid 13s is possible with a good driver or mabye even better!

-sander

 

This is some really good information. So it sounds like to get the 11.1 compression ratio that I'm looking for I should go with JDM Itr pistons. It sounds like it would be a good idea to get the block bored .25 over to clean up the walls, and go with the oversize pistons. As for raising the compression just a few more points I could go with the High compression .50 mm intake & exhaust valves. This would raise the compression a few more points.

I'm really hoping this setup will get me into the low to mid 13 teens. Other mods included in this setup are a B16a2 tranny with quaife, 310 RC injectors, Hondata S200 for the tuning, JDM 4to1 header w/2.5 in collector, and 2.5 inch test pipe connected to Greddy EVO exhaust system. I would like to do this on BFG drag radials, but I also have a pair of 13x8 Bogarts with Mickey Thompson 24.5x8x13 slicks

 

For some reason I dont see that hitting mid or low 13's. What kind of cams do you plan on using?

*edit* never mind lol.


[Modified by lazy bum shaughn, 4:05 PM 4/1/2003]

 

I'd run higher compression. The Crower stage 3s will cost you a bit of compression like any of the larger cams. I'd go with CTR pistons if you want to stay with OEM slugs. I'm at 12.6:1 w/ my Crower 63403 cams and detonation free thus far. If you run the numbers on that setup through a dynamic compression calculator you'll find a drop of compression with the cams. Run higher static compression to compensate.