F4R pistons in F7R

[none]

Hi everyone. I'm wondering to put f4r (clio 172) pistons to f7r block to get higher CR. Is it just a straight swap or i need to do any modifications to the piston? Also what CR will i get with this mod? Maybe someone had done this "budget" mod?
I have found some older topics, but dind't find there any proper info.
Thank you.

[tutuur]

there's been debated alot in the other topics but somewhere next week i'll have a set of f7r pistons and already have f4r ones.
i'll measure the whole thing cause i'm curious too!

[none]

It would be great to find out exactly how changes compression ratio with F4R pistons, think this information will be useful for most.
Was suggested to install 197 pistons, but in my country is really impossible to find them ... will wait for yours measure results and sorry for my english.

[tutuur]

well i'm not from England too so my english isn't as perfect too..

[Mikeb185]

Well there both 82.7 mm so should be a straight swap. They won't give you the exact same compression ratio but shouldn't be too different. I have a set of megane 225 pistons that I will be dropping in my F7R engine so fingers crossed!

[sideways danny]

IMO the CR difference wouldn't be worth the work, and the difference in valve pocket sizes may cause issues

[tutuur]

received the pistons from Jaff today and took some photo's:




as Danny says there is almost no difference in CR with these in a F7R. i think the main difference comes from the head of a F4R.
imo the F4R pistons would only be worth it if you have a big cam and need bigger valve cutouts.

the F7R pistons are 338grams/piece, the F4R jobbies 342grams/piece.
the wrist pins differ too, 92grams for F7R and 110grams for F4R.
i don't know how much this influences performance but there is a difference of 22grams/piston..


next week i'll receive a set 225 pistons and than going to measure everything up for let's call it science :P