CP Forged Pistons

Discussion and technical advice the SW20 MR2. 3S-GTE, 3S-GE, 3S-FE etc
Anything and everything to do with maintenance, modifications and electrical is in here for the Mk2.

Moderators: IMOC Moderators, IMOC Committee Members

ashley
Posts: 7628
Joined: Tue May 13, 2008 8:08 pm

Re: CP Forged Pistons

Post by ashley »

kev8611 wrote:
ashley wrote:
kev8611 wrote:ok i get the point. il keep my opinion to myself.

mr2rich. sorry to have caused any confusion to you. after all. peter and co are the specialists on here so anyone elses points are invalid :thumleft:


opinions are fine, but you have to be open to challenge when throwing around statistics like that mate...all meant in good humour, apologies if I offended :thumleft:


ok so in other words. whats the chances of going and buying a set of 86mm CP's and a standard blocks measurments being bang on for required clearances on the spec sheet down to the last ten thou?


Based on your data: 0%
Based on my data: 75%

Real answer....???? No way of knowing without more data!

Only real way to know is to strip the block in front of you and inspect and measure it :thumleft:
Peter Gidden
IMOC Affiliated Trackday Organiser
Posts: 10506
Joined: Tue Jan 25, 2005 9:49 am
Location: South Yorkshire

Re: CP Forged Pistons

Post by Peter Gidden »

kev8611 wrote:
ashley wrote:
kev8611 wrote:ok i get the point. il keep my opinion to myself.

mr2rich. sorry to have caused any confusion to you. after all. peter and co are the specialists on here so anyone elses points are invalid :thumleft:


opinions are fine, but you have to be open to challenge when throwing around statistics like that mate...all meant in good humour, apologies if I offended :thumleft:


ok so in other words. whats the chances of going and buying a set of 86mm CP's and a standard blocks measurments being bang on for required clearances on the spec sheet down to the last ten thou?


You're thinking is ar$e about face.

Have bores checked first, then buy pistons to match.
ashley
Posts: 7628
Joined: Tue May 13, 2008 8:08 pm

Re: CP Forged Pistons

Post by ashley »

Peter Gidden - SBITS wrote:

Have bores checked first, then buy pistons to match.


Exactly!
Gullzter
Posts: 2844
Joined: Wed Feb 27, 2013 1:04 am
Location: Glasgow

Re: CP Forged Pistons

Post by Gullzter »

ashley wrote:
Peter Gidden - SBITS wrote:

Have bores checked first, then buy pistons to match.


Exactly!


+2
kev8611
Posts: 503
Joined: Fri Nov 15, 2013 12:08 am
Location: Scotland

Re: CP Forged Pistons

Post by kev8611 »

Gullzter wrote:
ashley wrote:
Peter Gidden - SBITS wrote:

Have bores checked first, then buy pistons to match.


Exactly!


+2


im aware of this lol. but in my case mines were outside tolerances so i had to go 86.25 then get block bored to spec
ashley
Posts: 7628
Joined: Tue May 13, 2008 8:08 pm

Re: CP Forged Pistons

Post by ashley »

ashley wrote:
Only real way to know is to strip the block in front of you and inspect and measure it :thumleft:


Peter Gidden - SBITS wrote:
Have bores checked first, then buy pistons to match.


kev8611 wrote: in my case mines were outside tolerances so i had to go 86.25 then get block bored to spec


Sounds like we're all saying the same thing then

Image
MR2 Rich
Posts: 1582
Joined: Sat Apr 07, 2012 1:18 pm
Location: Harrogate North Yorkshire

Re: CP Forged Pistons

Post by MR2 Rich »

So what everyone is saying is buy 85mm pistons, then measure the bores and rebore it to 87mm?!
No 2 :(
Peter Gidden
IMOC Affiliated Trackday Organiser
Posts: 10506
Joined: Tue Jan 25, 2005 9:49 am
Location: South Yorkshire

Re: CP Forged Pistons

Post by Peter Gidden »

MR2 Rich wrote:So what everyone is saying is buy 85mm pistons, then measure the bores and rebore it to 87mm?!


Who said that?
Gullzter
Posts: 2844
Joined: Wed Feb 27, 2013 1:04 am
Location: Glasgow

Re: CP Forged Pistons

Post by Gullzter »

MR2 Rich wrote:So what everyone is saying is buy 85mm pistons, then measure the bores and rebore it to 87mm?!



:-k

I think they mean check bore clearance then buy piston to suit said clearance?
craig
Posts: 43936
Joined: Sat Dec 18, 2004 3:44 am

Re: CP Forged Pistons

Post by craig »

MR2 Rich wrote:So what everyone is saying is buy 85mm pistons, then measure the bores and rebore it to 87mm?!


Image
ashley
Posts: 7628
Joined: Tue May 13, 2008 8:08 pm

Re: CP Forged Pistons

Post by ashley »

MR2 Rich wrote:So what everyone is saying is buy 85mm pistons, then measure the bores and rebore it to 87mm?!


Image
MR2 Rich
Posts: 1582
Joined: Sat Apr 07, 2012 1:18 pm
Location: Harrogate North Yorkshire

Re: CP Forged Pistons

Post by MR2 Rich »

Thanks Ash... :mrgreen:

Measure bores.
Buy pistons.
If rebore needed give the reborer the pistons.
Happy days.
No 2 :(
Gullzter
Posts: 2844
Joined: Wed Feb 27, 2013 1:04 am
Location: Glasgow

Re: CP Forged Pistons

Post by Gullzter »

ashley wrote:
MR2 Rich wrote:So what everyone is saying is buy 85mm pistons, then measure the bores and rebore it to 87mm?!


Image



:rambo:
MartinF
Posts: 494
Joined: Thu Sep 01, 2011 8:27 pm
Location: Essex
Contact:

Re: CP Forged Pistons

Post by MartinF »

Marf wrote:

The plural of anecdote is not data.


PMSL.....that is a great line!

Filed for future use :D
Blue Lexus RCF
Black MKIV UK Manual Supra
Green MK2 MR2 Tin Top
kev8611
Posts: 503
Joined: Fri Nov 15, 2013 12:08 am
Location: Scotland

Re: CP Forged Pistons

Post by kev8611 »

im sure i have a copy of a spec sheet for 86mm CP's and i deffo have my spec sheet for 86.25's

i can give you the specs for 86mm's and what your bore size needs to be. if every set is the same. not sure if each spec sheet is different or theyre all "off the shelf"
bobhatton
Posts: 3351
Joined: Fri Aug 25, 2006 9:34 pm
Location: Bodmin Cornwall

Re: CP Forged Pistons

Post by bobhatton »

kev8611 wrote:im sure i have a copy of a spec sheet for 86mm CP's and i deffo have my spec sheet for 86.25's

i can give you the specs for 86mm's and what your bore size needs to be. if every set is the same. not sure if each spec sheet is different or theyre all "off the shelf"


If the pistons are made to fit a 86mm bore then that is the size the bore needs to be. The piston clearance is built into the pistons
Designer for turbo set ups on F1 cars, and Nitrous Oxide Systems of the USA in the 80s
ashley
Posts: 7628
Joined: Tue May 13, 2008 8:08 pm

Re: CP Forged Pistons

Post by ashley »

bobhatton wrote:
kev8611 wrote:im sure i have a copy of a spec sheet for 86mm CP's and i deffo have my spec sheet for 86.25's

i can give you the specs for 86mm's and what your bore size needs to be. if every set is the same. not sure if each spec sheet is different or theyre all "off the shelf"


If the pistons are made to fit a 86mm bore then that is the size the bore needs to be. The piston clearance is built into the pistons


But you would of course still measure the pistons and check you actually do have the desired clearance wouldn't you Bob :whistle:
bobhatton
Posts: 3351
Joined: Fri Aug 25, 2006 9:34 pm
Location: Bodmin Cornwall

Re: CP Forged Pistons

Post by bobhatton »

ashley wrote:
bobhatton wrote:
kev8611 wrote:im sure i have a copy of a spec sheet for 86mm CP's and i deffo have my spec sheet for 86.25's

i can give you the specs for 86mm's and what your bore size needs to be. if every set is the same. not sure if each spec sheet is different or theyre all "off the shelf"


If the pistons are made to fit a 86mm bore then that is the size the bore needs to be. The piston clearance is built into the pistons


But you would of course still measure the pistons and check you actually do have the desired clearance wouldn't you Bob :whistle:


Oh yes.

Just had an engine in where the pistons were made to fit a 89mm bore, 9.5:1 comp ratio with 2 bar + boost, not a Toyota.

It melted the 4 plugs within 5 miles of leaving the mappers.

We stripped it down and I could see lots of piston rings down the side of the pistons.

We measured the bore and yes it was 89mm but the pistons were under size.
The machine shop had had the pistons when they bored the block but had not measured them, just bored to 89mm. They paid for a new set of pistons at 7.5:1.

On the first dyno run it now has 300 hp at 10 psi and will get over 500hp with under 2 bar boost
Designer for turbo set ups on F1 cars, and Nitrous Oxide Systems of the USA in the 80s
JD
Posts: 2888
Joined: Mon Apr 16, 2012 6:23 pm
Location: The Far East

Re: CP Forged Pistons

Post by JD »

bobhatton wrote:The machine shop had had the pistons when they bored the block but had not measured them, just bored to 89mm. They paid for a new set of pistons at 7.5:1.


:shock:
Odin_S
Posts: 1210
Joined: Wed Jul 19, 2006 3:35 am
Location: London

Re: CP Forged Pistons

Post by Odin_S »

I'm doing an engine rebuild this year on my car the pistons I bought are 86.50 from ats They said that's the standard rebuild size...

Don't really want to bore out more out of the cylinder block than I need to. So I'm assuming I would probably need to buy new ones?

PW is doing my build in summer
Post Reply

Return to “MR2 MK2 1990 - 1999 NA & Turbo”