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turbo update no. 5.. :)... PISTONS

Mathew, Chun and anyone else interested.

Ok, I have been researching pistons and suitability for the turbo application (F4R 172 engine)

these are my conclusions at the moment.

Stock turbo pistons are 9.5:1 cr.

Stock turbo pistons are superbly built. They have integrated cast nickel foam inserts for excellent thermal transfer.. the 172 pistons, out of interest, dont have this.!

Head and piston form a squish area which is beautifully designed.

Squish area is the thing that reduces detonation and allows the std 172 to achieve a healthy 11:1 cr with no problems.

result.. !!

I am intending to use the std turbo pistons with about 3 cc per cylinder removed from the non squish area of the 172 head. this brings cr to about 9:1

the combination of squish helps prevent detonation.

using a forged piston, I believe, is totally unecessary due to the excellent design of the existing pistons as revealed by close inspection. Also, we are not increasing the rev limit of the engine at all.



ClioSport Club Member
  Clio v6

I was just wondering if there should be a New Captain Slarty type section for all of us techno wizards to visit when we need our fix.

lol Dash .. naw...

Btw, Mathew N Chun...

I must add, this hasnt ruled out the use of forged pistons..

the reason being - IF the 172 head cannot be enlarged - or - the piston bowl cannot be increased - safely.. (the piston could lose a mil, but not sure about the head yet)

looking at the head tomorrow..


this makes a change, one of your posts that could actualy save me money, Id still like to see the cost of the forged pistons though


yep, as said, it may well still be a requirement for pistons (and then might as well go forged) if the head is not easily modded.

will see, .. I will try to get some quotes after the Bank hols..