Originally Posted by Sonny

Hi All:

So far, I have 6 different D series pistons to work with. I have almost every piston from 1.6 liter engines. I think I'm missing one from the 96+ Civic HX, but nobody has that car. :p

Here are the contenders so far:
https://www.superhonda.com/photopost/.../11214pg6b.jpg

https://www.superhonda.com/photopost/...1/11214p29.jpg

https://www.superhonda.com/photopost/...1/11214pm7.jpg

https://www.superhonda.com/photopost/...1/11214pm6.jpg

https://www.superhonda.com/photopost/...1/11214p28.jpg

https://www.superhonda.com/photopost/...1/11214p2p.jpg

I've measured the P29 and PM7 pistons in several ways and as far as I can tell, they are exactly the same. I wonder why Honda made 2 different part numbers and castings for the same piston? Hmmm...

Sonny

Originally Posted by Sonny

The main motivation behind this project is to determine what compression ratio is yielded using different combinations of D series pistons and D series heads. There is such a large variance in the way that Honda designed the pistons that just about any compression ratio is doable.

For example, the PG6B (86-87 Integra) and the P28 (92-95 Civic) both have the same compression height (1.181"). They will be flush with the top of hte block when installed. However, the Integra piston has a small dome, but the Civic piston has a HUGE dish. The difference between the 2 pistons afa compression ratio is very large.

Here are some pics comparing the P29 (88-89 Integra) to the PM7 (88-91 JDM ZC). This Integra piston was slightly modded on top, but I've seen a very clear picture of the top of this piston and can say that it is identical in shape to the PM7.

https://www.superhonda.com/photopost/...pm7vsp29-1.jpg

https://www.superhonda.com/photopost/...pm7vsp29-2.jpg

https://www.superhonda.com/photopost/...pm7vsp29-3.jpg

Sonny

Originally Posted by Sonny

Ok guys, last pic for now.

https://www.superhonda.com/photopost/...ionheights.jpg

Sonny