Piston size - Group N

[Alastair]

I was looking at my R5 GTT Group N works manual the other day and remember that the piston size was listed as 76.6 mm.

What are the advantages of fitting a 0.6mm larger piston, i assume they go into the standard size liners but ill have to check the manual for part numbers.

I can only guess that it gives a deeper ringland for added stregnth? Any other reasons for this? What about piston to wall clearance - what happens there :scratch:

Any decent books out there that i should read to get up to speed?:coffee:

[Sparkie]

i thought they were allowed 1 overbore before they broke the rules, so they took it up to 1427cc, to get more power???

[Tony Walker]

I doubt they even dreampt of the pressures we squeeze into the c1j today.

[Alastair]

i thought they were allowed 1 overbore before they broke the rules, so they took it up to 1427cc, to get more power???

Ahhh, I see. Mecca do forged pistons at a really good price but the over bore are twice the price...

I read that they retained the stock T2 turbo though but they were very accurately balanced, that would have massively limited their power, not sure how much boost they added but i bet they had a wedge of torque low down.

[Sparkie]

if you look at the shalco website for racing r11T's they say they were putting out 180bhp.

[Lewis]

76.6mm bore with the standard 77mm stroke gives you 1419cc.
Remember that these cars had to meet the regulations for racing and turbo charged vehicles had a multiplication factor applied to the engine cc. Something like 1.7 if my memory was right.
I think if they went to 77mm bore which was also available then they would have to move up to the next class for racing.

76.6mm won't run in a standard liner, not sure about the headgasket standard may be ok, but 76.6mm bore gaskets are available. Speak to Andy Cooke for more info I think he still runs 76.6mm bore. If your not confined by racing regulations though and you want more cc's on your C1J then you may as well go for 77mm

[Alastair]

Sparkie, ill have a look at the Shalko site - many thanks.

Lewis, i am sure it said somthing about machining / replacing the liners too. The conversion factor is still 1.7 which makes it really hard to compete with the big cc and big wallet boys, as we go over the 2 ltr threshold into the next class.

If they said upto 1400cc turbo were a 1.4 factor (like in some other series) then the R5 would be 1956cc and much nearer the mark for power to weight against 2ltr novas with 10k under the bonnet. I still have to run a 34mm restrictor!

This is why i have been toying with dropping in a well built 182 with bodies etc as i could get approx 225 hp for a similar weight, and drop a class.

[Sparkie]

http://homepage.virgin.net/shalco.com/renault11.htm

[Alastair]

Great read thanks for the link! Now where can i get a works gearbox from then!

[Tony Walker]

http://homepage.virgin.net/shalco.com/renault11.htm



"We have less than 180bhp, for sure. It�s not a joke � it�s impossible to have more from such an engine": Froncois Bernard, Renault Sport




^^^ love that quote.

[Tony Walker]

"We have less than 180bhp, for sure. It�s not a joke � it�s impossible to have more from such an engine": Froncois Bernard, Renault Sport




^^^ love that quote.



180bhp with a t2 at 1bar? :D thats good going.

[Sparkie]

1 bar? - is that to be taken with a big pinch of french salt?