Clio 3 Rs 197/200 OEM pistons

[MiniCooper1380]

Good evening,

does someone know the piston F4R830 (Clio 3 RS 197/200) dome volume ? If I use F4R830 pistons in a standard F4R730 engine what will be the compression ratio (I know it should be higher but I would know a value)?

I calculated the approximate compression ratio using excel but I don't know if it is correct:

Thanks for your help!
Marco

 

[NorthloopCup]

Your calculations are pretty much bang on mate as from memory they take a 172 up to around 12.2:1

 

[bozothenutter]

So no machining required?

 

[NorthloopCup]

So no machining required?

Depends on if your happy to run that compression ratio on a non forged piston I suppose. It all comes down to the mapping.

 

[MiniCooper1380]

You can use different head gasket thickness for a different compression ratio! For example with a Cometic 1.02mm gasket you can obatin 11.8:1 (it is very similar to 11.7:1 Gr.N compression ratio and they use 172 standard pistons).

 

[bozothenutter]

Subscribing to this....good info here!
If i ever get around to building my own engine.....[emoji57]

 

[bozothenutter]

What would a safe limit be pn cast pistons?
In another thread I read that VAG use forged pistons in the faster models and that they are ok for a daily dependant on the material used?

 

[Ph1 Tom]

I've ran 12.5:1 on cast with 99octane fuel.

You could always use a megane head gasket

 

[NorthloopCup]

What would a safe limit be pn cast pistons?
In another thread I read that VAG use forged pistons in the faster models and that they are ok for a daily dependant on the material used?

If you get the mapping right and there's no det you'll be fine at anywhere up to 12:1-12.5:1 I'd imagine. It's all about keeping the cylinders cool and having no det though. You'll be running a fine line on a Renault cast piston imo, and that's based on how many f4r's you see that have suffered from broken ring lands. That's caused by detonation and duff casting. The 197 pistons may well be stronger than the normal 1*2 pistons though.

Yeah forged pistons can be used in a daily driver but it's all about getting the correct grade. Most performance stuff isn't and you usually get a reasonable amount of slap on the pistons from cold. The noise is gone within a matter of minutes though.

 

[Dan@SJM]

I had one in today with an R3 manifold, pistons are dead in it. Has done a week of driving unmapped for the manifold and today it was down to 165-170psi compression. Bore scoped it and saw a knackered piston 😧

Excuse the crap picture.

 

[NorthloopCup]

I had one in today with an R3 manifold, pistons are dead in it. Has done a week of driving unmapped for the manifold and today it was down to 165-170psi compression. Bore scoped it and saw a knackered piston 😧

Excuse the crap picture.

Ouch!!

 

[Dan@SJM]

Indeed, just goes to show you can never underestimate the amount of importance having a map check after any changes.

 

[Adey.]

wow, must of been miles out! anyone tried 197 pistons and cams in a 172/182?

 

[MiniCooper1380]

Yeah forged pistons can be used in a daily driver but it's all about getting the correct grade. Most performance stuff isn't and you usually get a reasonable amount of slap on the pistons from cold. The noise is gone within a matter of minutes though.

Theorically 4032 material helps to remove slapping with smaller piston to bore clearance than 2618!
For example these are some Clio 172 piston to bore clearances:
OE 0.025/0.035mm
Wossner 4032 T6 0.07mm
JE 2618 T6 0.076/0.089mm
PistalRacing 2618 A 0.105/0.115mm
But I think it also depends from piston design.

 

[bozothenutter]

Going from that list the ubiquitous wossners are the best choice for a dailey then?
Why use the other grade of metal then?
Is it lighter/stronger?

 

[Dan@SJM]

I use supertech (PEC) Pistons in the builds I do.

 

[bozothenutter]

I use supertech (PEC) Pistons in the builds I do.

interesting I see they do a long rod kit, does this lessen the sideforce on the bore? (wont just having two rings be a (longevity)problem?)

what material are they (the blurb on teh page is VERY generic)
http://www.steelconrods.co.uk/index.php?cPath=77_81_144

 

[rich83]

Ouch!!

Yes mate ouch indeed, ouch to my bloody wallet!!!!

 

[rich83]

I had one in today with an R3 manifold, pistons are dead in it. Has done a week of driving unmapped for the manifold and today it was down to 165-170psi compression. Bore scoped it and saw a knackered piston 😧

Excuse the crap picture.

Hi @Dan@SJM,

Got the head off and looking at the pistons, seems they have repaired themselves? I'm pretty sure I watched you with the borescope but could that have been a saved picture on the scope? Unitl the pistons are out wont know if the rings or ring lands are fadged, because compression was clearly down (my tester was 160psi) - but it's very strange that the pistons are looking to have cleaned up somehow?

full size:
http://www.cliorsr.uk/wp-content/uploads/2015/01/IMG_3773.jpg
http://www.cliorsr.uk/wp-content/uploads/2015/01/IMG_3774.jpg
http://www.cliorsr.uk/wp-content/uploads/2015/01/IMG_3775.jpg
http://www.cliorsr.uk/wp-content/uploads/2015/01/IMG_3776.jpg

Cheers.

 

[Dan@SJM]

Very odd! I do indeed have a picture saved on the bore scope. But I'll have to take it home to plug it in and pull the pic off. As you said you saw for yourself what looked to be a knackered piston. Very low compression on that motor thiugh.

 

[Dan@SJM]

Just re-read what you wrote, i wouldn't have made up that it had a knackered piston, which is why I showed you in person. (Let's face it, why would I reject doing work that'll earn me money!) you also backed up my compression test results with your own tester which came out at the same readings as my own.

 

[rich83]

Oh no sorry Dan I wasn't implying you did, didn't mean it to read that way. Like you said I saw the bore scope. I'm just confused so was wondering if you had a suggestion as to if/how it was possible?
Reason I was asking if you had a saved picture was maybe it wasn't as bad as the picture - and the picture wasn't my engine perhaps? No question that both the comp tests were both low and the engine was not performing, the top end of the rev range grew increasingly flat over the last 2 months.

 

[Dan@SJM]

Oh no sorry Dan I wasn't implying you did, didn't mean it to read that way. Like you said I saw the bore scope. I'm just confused so was wondering if you had a suggestion as to if/how it was possible?
Reason I was asking if you had a saved picture was maybe it wasn't as bad as the picture - and the picture wasn't my engine perhaps? No question that both the comp tests were both low and the engine was not performing, the top end of the rev range grew increasingly flat over the last 2 months.

Ah I see, apologies for reading it that way. The picture was of yours (I'd only bought the scope a few days before) I think what we saw on the scope is a close up of what looks like minor melting on cyl 1 in your pics above?

 

[rich83]

Cheers, that rules that out. Must be must be the magnification factor and relative lack of resolution of the scope then. Yeah I think it must be the bits on the edge of cyl1 too then, the pistons had a wipe down to clear down some of the carbon to look at the edges. I think therefore perhaps it probably looked more like the bore image before.
Must be rings or ring land then, still at least cleaned up they'll make a nice paper weight or something!
Cheers

 

[NorthloopCup]

If they aren't fucked I'd be tempted to re-ring them tbh mate.
You'll know if it's damaged the ring lands/skirts when you pop them out. The ring lands normally fall off where they've cracked.

 

[rich83]

Yeah but I want some 83mm 12.5:1 action now don't I!

 

[NorthloopCup]

Yeah but I want some 83mm 12.5:1 action now don't I! :wink:

Lol!