Track / Motorsport Prep' This forum is for technical discussions about track / motorsport preparation. Posting rights have restricted to select usergroups. If you wish to contribute to discussions within this forum, request acceptance from the usergroup leader from your User CP. |
|
|
14th November 2010, 22:59
|
#21
|
Saxperience Post Whore
Join Date: Jun 2006
Location: Ramsey st marys, peterborough
Posts: 8,288
Car(s): Saxo's, Corsa (Daily)
|
Also it not always about bigger valves too.
Pm sandy for prices
|
|
|
14th November 2010, 23:14
|
#22
|
Established Member
Join Date: Sep 2009
Location: rotherham
Posts: 1,832
Car(s): Be scirocco, full on 03plate track spec Saxo
|
i no alot of u hate hi flow head but there sites quite good for rough idea on prices ect
|
|
|
5th December 2010, 21:47
|
#23
|
Saxperience Post Whore
Join Date: Feb 2008
Location: Liverpool
Posts: 7,393
Car(s): Black Corsa C SRi
|
youll need hi comp pocketed pistons, pockets to deal with increased lift and hi comp to compensate for the increased overlap
|
|
|
5th December 2010, 21:49
|
#24
|
Saxperience Post Whore
Join Date: Jun 2006
Location: Ramsey st marys, peterborough
Posts: 8,288
Car(s): Saxo's, Corsa (Daily)
|
Quote:
Originally Posted by LeeM
youll need hi comp pocketed pistons, pockets to deal with increased lift and hi comp to compensate for the increased overlap
|
no you dnt you will to get the full benifits but can be ran on standard pistons but again to get the full benifit out of ph4 you will need pocket pistons
|
|
|
5th December 2010, 22:01
|
#25
|
Saxperience Post Whore
Join Date: Feb 2008
Location: Liverpool
Posts: 7,393
Car(s): Black Corsa C SRi
|
i see, i was under the impression the increased overlap gives less time for the fuel and air to be compressed, so the high comps will make up for that. still learning though
|
|
|
5th December 2010, 22:15
|
#26
|
Saxperience Forum Bum
Join Date: Jan 2006
Location: Banbury
Posts: 4,623
Car(s): Saxo Rally Car
Evo 6
|
Overlap means inlet and exhaust valves are open at the same time. This creates the scavenging effect and gets the next cycle of gases out quicker (exhaust) or brings them in faster (induction)
So using high compression pistons do help this effect.
P.s I dont mean to sound like a cock!
__________________
Quote:
Originally Posted by Olly
Colin and his legendary special bits
|
Smoking Bozos Since 1988
|
|
|
6th December 2010, 09:08
|
#27
|
Saxperience Post Whore
Join Date: Jun 2006
Location: Ramsey st marys, peterborough
Posts: 8,288
Car(s): Saxo's, Corsa (Daily)
|
Yer the hi comps will help yes, but to the answer I gave it was just that you can use them on standard pistons but by no means say it the best way to go, they will have to be timing to match ph3 cams in term of lift.
|
|
|
6th December 2010, 09:30
|
#28
|
Saxperience Forum Bum
Join Date: Jan 2006
Location: Banbury
Posts: 4,623
Car(s): Saxo Rally Car
Evo 6
|
Agreed Andy, yeah coz you can only run a certain amount of lift and duration on standard pistons without ptv. Ph4 on stds would be backed right off and run bad
|
|
|
6th December 2010, 17:39
|
#29
|
Saxperience Forum Bum
Join Date: Dec 2008
Location: Meerkat Harborough
Posts: 2,638
Car(s): Saxo vtr mk 2
|
My simple way of explaining it is,
high comps dont increase the compression they maintain the same dynamic compression but with a higher overlap. This is obviously not the law.
|
|
|
2nd January 2011, 17:42
|
#30
|
Saxperience Forum Bum
Join Date: Dec 2008
Location: Pontefract
Posts: 4,007
Car(s): 2010 E92 320i MSport
|
So if I were to purchase Hi-Comp pistons to put in my J4 bottom end, I should get ones designed to fit the JP4 bottom end so the inlet valve cut-out matches?
|
|
|
2nd January 2011, 18:00
|
#31
|
Saxperience Addict
Join Date: Jul 2005
Location: Solihull / Bournemouth
Posts: 14,233
Car(s): 2015 Lapiz Blue Golf R
|
jp4 rods use a 18mm pins from memory,
so you couldn't use jp4 pistons with j4 rods.
|
|
|
The Following User Says Thank You to raunchz For This Useful Post:
|
|
2nd January 2011, 18:04
|
#32
|
Saxperience Forum Bum
Join Date: Dec 2008
Location: Pontefract
Posts: 4,007
Car(s): 2010 E92 320i MSport
|
So how could you get round the issue?
|
|
|
2nd January 2011, 18:06
|
#33
|
Established Member
Join Date: Sep 2009
Location: rotherham
Posts: 1,832
Car(s): Be scirocco, full on 03plate track spec Saxo
|
why are you wonting to mix and match the engines? i would stick with he engine you have tbh mate as its a reali good engine with low milage ect, for all hassle of mixing matching heads and bottom end i would just stick with your orginal engine and rebuild tht mate,...
|
|
|
2nd January 2011, 18:15
|
#34
|
Saxperience Addict
Join Date: Jul 2005
Location: Solihull / Bournemouth
Posts: 14,233
Car(s): 2015 Lapiz Blue Golf R
|
Quote:
Originally Posted by JoshB
So how could you get round the issue?
|
I presume you want to fit a jp4 head to the j4 bottom end?
In that case I'd do one of 2 things, stick with a j4 head, and get some headwork done on it byt keep standard valve sizes.
OR
Go all out and get some jp4 forged rods etc.
|
|
|
2nd January 2011, 21:31
|
#35
|
Saxperience Forum Bum
Join Date: Dec 2008
Location: Pontefract
Posts: 4,007
Car(s): 2010 E92 320i MSport
|
Quote:
Originally Posted by mark1311
why are you wonting to mix and match the engines? i would stick with he engine you have tbh mate as its a reali good engine with low milage ect, for all hassle of mixing matching heads and bottom end i would just stick with your orginal engine and rebuild tht mate,...
|
After I'd bought the car I found out the cambelt had snapped. The engine did run rough and stalled everytime it idled. I'm guessing that theres a few bent valves in there. I did get a set of new valves but read about JP4 heads and got one cheap off ebay, thats the only reason.
Quote:
Originally Posted by raunchz
I presume you want to fit a jp4 head to the j4 bottom end?
In that case I'd do one of 2 things, stick with a j4 head, and get some headwork done on it byt keep standard valve sizes.
OR
Go all out and get some jp4 forged rods etc.
|
So I could still put JP4 rods and pistons in a J4 bottom end?
|
|
|
Posting Rules
|
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts
HTML code is Off
|
|
|
All times are GMT. The time now is 13:08.
|