Forged Pistons

[Aydon182]

Have come into a bit of money recently and decided to forge the internals on the clio, I've been looking at alot recently and just wondered if any of the guru's could answer these two questions,

What pistons are recommended by you and why?
I've been looking at wossners , prima racing or k-tec's?
Obviously I'm looking for a low compression piston capable of *hopefully* seeing the magic 300bhp by summer time.

Secondly, what bore size is recommended ?
Obviously you need some play as the pistons expand but what do you guys think?
82.7/83/84?

Oh also what forged conrods do you guys recommend ?
Cheers,
Aydon

 

[Chip-mk1]

Bare in mind you need to be basing the compression on the fact you have a 197 head.
Engine dynamics are a good place to get a wossner piston and rods combination.

Having already done some mapping on your car for the previous owner, I would say that you want to go higher with the compression not lower if anything as the amount of ignition yours is already taking leads me to believe that a lower comp isnt going to gain you anything, especially given how little extra air you actually need to flow in order to see that figure (you're already flowing 280bhp worth of air basically but I have mapped it very rich at the top end to keep EGTs down which is why its only making 260bhp from that 280bhp worth of air)

I would aim at around 9:1 compression, but like I said make sure they are 197 9:1 pistons not 172 9:1 pistons.


If you up the compression, the map MUST be adjusted before you bring it up on boost on the new setup, as otherwise you risk detonation which could quickly destroy your new pistons.

As for bore size, 84mm will still be strong enough at such modest power outputs so you may as well take the free capacity increase from going to that.

 

[Aydon182]

Bare in mind you need to be basing the compression on the fact you have a 197 head.
Engine dynamics are a good place to get a wossner piston and rods combination.

Having already done some mapping on your car for the previous owner, I would say that you want to go higher with the compression not lower if anything as the amount of ignition yours is already taking leads me to believe that a lower comp isnt going to gain you anything, especially given how little extra air you actually need to flow in order to see that figure (you're already flowing 280bhp worth of air basically but I have mapped it very rich at the top end to keep EGTs down which is why its only making 260bhp from that 280bhp worth of air)

I would aim at around 9:1 compression, but like I said make sure they are 197 9:1 pistons not 172 9:1 pistons.


If you up the compression, the map MUST be adjusted before you bring it up on boost on the new setup, as otherwise you risk detonation which could quickly destroy your new pistons.

As for bore size, 84mm will still be strong enough at such modest power outputs so you may as well take the free capacity increase from going to that.

Perhaps for the sake of ease and finance it may be easier to go back to the 172 head so I haven't got to find some custom piston set up. Just how much has the 197 head dropped the CR by? Ideally I want to forge the internals for peace of mind when I start using the car for heavy track use plus a trip to the nurburgring was on the cards. I'll give engine dynamics a call Monday I'm quite friendly with them anyway to see what they recommend.

Also do you know anyone else who can map the m-tech management for clio's? It's not compforting knowing there's only one man in the world who can do it and he's always busy as hell, lol.

 

[Chip-mk1]

Up to you head wise mate, but it shouldnt be anymore hassle to buy 197 pistons than 172 really, its still not exactly "custom" its just pistons for a different standard engine.

Any competent tuner should be able to map your car, but you need to accept that to do so for things like coldstart they are going to need your car for a few days, if you are happy to drop it off at MWM or Stone (ie near me during the week) then I will happily do it for you free of charge but you'll obviously be without the car for a few days while that happens.

I see no real point in you doing pistons etc now though, why not just enjoy the car as it is first, if you are looking at rebuilding the engine later on then why not buy a secondhand 172 engine and build that up while you are still using the car with the current engine in the mean time, it may surprise you with how long it lasts, and that will give you time to sort the suspension and brakes etc and to practice driving the thing etc.

 

[scotty2hotty81]

Up to you head wise mate, but it shouldnt be anymore hassle to buy 197 pistons than 172 really, its still not exactly "custom" its just pistons for a different standard engine.

Any competent tuner should be able to map your car, but you need to accept that to do so for things like coldstart they are going to need your car for a few days, if you are happy to drop it off at MWM or Stone (ie near me during the week) then I will happily do it for you free of charge but you'll obviously be without the car for a few days while that happens.

I see no real point in you doing pistons etc now though, why not just enjoy the car as it is first, if you are looking at rebuilding the engine later on then why not buy a secondhand 172 engine and build that up while you are still using the car with the current engine in the mean time, it may surprise you with how long it lasts, and that will give you time to sort the suspension and brakes etc and to practice driving the thing etc.

This is exactly what I'm doing with mine, build up a forged engine ready to fit instead of Doing your own, Unless of course you have lots of spare time on your hands.

 

[Aydon182]

Some very wise words there chip, which I will take into deep concideration. Infact it actually sounds like a really good idea and a brilliant project for me. I really appreciate that you are going to map it for me mate I will give you a ring soon I may have to book a few days off work but otherwise everything is still good for not this Tuesday but next for a bit of mapping.

 

[Tutuur]

are forged pistons really neccesary for 300bhp?
i see many cosworth's, scooby's etc with way more then 300bhp without forged pistons....

i'm curious on how much the 197 head dropped the compression too!

 

[Andyman]

are forged pistons really neccesary for 300bhp?
i see many cosworth's, scooby's etc with way more then 300bhp without forged pistons....

i'm curious on how much the 197 head dropped the compression too!

Cosworths and Scooby's have stronger pistons to start with being already turbo.


Try TSR for the pistons

 

[Tutuur]

How do you know that? As found before meg. F4r pistons are exactly the same as clio f4r only different CR...

 

[Chip-mk1]

Cosworths and Scooby's have stronger pistons to start with being already turbo.


Try TSR for the pistons

Sierra/Escort Cosworths used pressure cast mahle pistons, awesome quality, good for 500bhp+ , same as a calibra turbo uses.

Not even vaguely comparable to the poorly cast rubbish in an F4R engine.


F4R pistons are actually a bit of a lottery, the casting process is poor so the quality is very variable, all it takes is a casting imperfection in the wrong place and you can find a failure.

Fatigue over time is definately an issue with poor quality pistons as well.

 

[Tutuur]

well i'll see how my machined F7R pistons are going to hold then....

although i would't be suprised that it's the quality off the materials nowadays due to manufacturing everything cheaper and cheaper in stead of more reliable....