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AndyFielder
06-06-2007, 10:09
Haveing a look on BB at parts for a future engine rebuild...

It says i would have to have fueling and induction changes, if i fit the Group A pistons, becasue of the increased compression ratio.

Can people in the know full me in. Why do i need these changes, and why increasing the compression ratio is quicker in a N/A car.

Andy
stan
06-06-2007, 10:34
In short, increasing the compression ratio increases combustion efficiency and so you extract more energy from the fuel/air mix...leading to more torque/power.

The reason you need to alter ignition is so that you dont increase peak temps and pressures to a npoint which will induce detonation. Reducing ignition advance will bring you away fromt he danger zone that increasing the Cr may bring you into.

"Group A" is a sales pitch...theres nothing associated to a heritage with these pistons...they are boggo Wossner pistons....something I steer clear of.
stan
06-06-2007, 10:39
Also, as far as fuelling goes, increasing the ammount of actual fuel burnt whilst still only offering a fixed ammount into the intake will alter the AFR and so need correction.
schakal
06-06-2007, 10:41
would removing material of standard
pistons not increase the c/r ??
stan
06-06-2007, 10:52
No it would reduce Cr.
MAXIBOY
06-06-2007, 10:52
no adding material would
dhay14
06-06-2007, 10:58
they are boggo Wossner pistons....something I steer clear of.

what do you mean by Boggo ? and does that count for thr Low compresion too?
MAXIBOY
06-06-2007, 11:02
means he,s not impressed by them. bit they are the only ones readily available with a 36 hour turn around to the best of my knowledge and a step up from standard.
schakal
06-06-2007, 11:17
no adding material would

so how do you add material to a piston ?? :roll:
or can you buy high comp pistons ?
stan
06-06-2007, 11:20
yes...forged pistons can be machined to have an intruder on the top which reduces chamber volume, and so increses Cr.
dimkais
06-06-2007, 21:39
I use wossner high comp pistons and 14,1 to 1 c.r for 6 years without problems at all..
MAXIBOY
06-06-2007, 21:40
and 9000rpm
dimkais
06-06-2007, 21:46
and 9000rpm

9300 :lol: :lol: :lol:
9k only for dyno and goes arround :twisted: :twisted:

Maxiboy,I think that you have the same internal with me (wossners and arrows :wink: )...
schakal
06-06-2007, 21:54
I use wossner high comp pistons and 14,1 to 1 c.r for 6 years without problems at all..

checked on wossner website now ,
the only high comps i can find are 12,3 to 1 :roll:
where did you get them from mate ?
dimkais
06-06-2007, 22:04
Lower the head and thinner gasket i think
stan
06-06-2007, 22:07
No ones disputing there would be problem...its more a case of searching for the Nth degree, there are better alternatives.

i.e....if you had a better piston, you may see better results.
AndyFielder
06-06-2007, 22:09
;) .. stan check for my pm please.. you mite have an i want to spend all my cash and have the fastest N/A clio in the country customer!
stan
06-06-2007, 22:16
lol

replied mate :D
MAXIBOY
06-06-2007, 23:22
and 9000rpm

9300 :lol: :lol: :lol:
9k only for dyno and goes arround :twisted: :twisted:

Maxiboy,I think that you have the same internal with me (wossners and arrows :wink: )...

yes mate wossner and arrows but low comp and turbo t28 hybrid. :twisted:
dhay14
07-06-2007, 00:14
wosnner 8.0:1 ?
MAXIBOY
07-06-2007, 00:20
wossner 8.5 to 1.
dhay14
07-06-2007, 00:23
can't get them

i can only get 8.0:1

where did you buy them?
AndyFielder
07-06-2007, 00:24
spam fest?????
dhay14
07-06-2007, 00:26
no mate

sharing info
AndyFielder
07-06-2007, 00:27
in my lovely thread!
MAXIBOY
07-06-2007, 00:31
sorry. had them made by http://www.bbperformancetuning.co.uk/

:D