Port & Polished Head

[llsaw]

Excellent quote from David Baker of Puma Race Engines UK

"The important things to get right are valve seat profiles and port shapes - polishing ports and chambers does nothing for power and single angle valve seats are a disaster in flow terms"

 

[rattan]

Intake ports so shiny how is the air and fuel going to mix properly?

Why intake port shiny means cannot mix fuel isit ? :shocked:

 

[CARENT]

Why intake port shiny means cannot mix fuel isit ? :shocked:

True.. This would result in incomplete combustion...

:confused_smile:

So, for the intake, usually, there is not smooth. Slightly rough... so that, when it goes into the cmbstion chamber, then it will be properly mixed.

:regular_smile:

Anyone with a 4G93P Dohc head for sale?

 

[Enslaved]

Those pics of the ports look soooo shiny...definitely good for use as mirrors...agree with CARENT, those ports are OVER polished...stock mivec heads flow very well...why mess around any more? at best, remove irregularities from the casting process and port the valve seat area. The ones above are overkill, fullstop.

 

[CARENT]

bumpssss........
Anyone with a 4G93P DOHC head

:confused_smile:

 

[CARENT]

anyone with information on the best mods that can be done for the 4G93P DOHC?

Looking at doing a PnP for a very long time nw...

still have mixed information on the results man... :confused_smile:

 

[shiroitenshi]

Just curious.. I thought porting was just done to improve flow?

I mean, if simply making it bigger equates big power, why don't we see huge intake/exhaust ports?

I'm no engineer, I admit. I'm thinking that what a good port does is simply improve the bends that lead the air into the combustion chamber for less resistance.

From what I know, simply making a port bigger will just make less power on the top-end, due to reduction of the ram-air effect at high RPM. In a way, air inertia actually helps engine breathing at high RPMs, hence there is an optimum port size depending on displacement, before reaching the point of diminishing returns.

Again.. I'm no engineer, so I'm waiting for someone to debunk my theory.

 

[CARENT]

Well, bro. It is true that if you over do it, then you may kill the respond from the engine. Basically, u will have to measure the cubic volume of the engine. No fixed or fast rule, maybe a lot of luck there in the mod process :regular_smile:

a fren of mine had some problem when he modded his car. Worse than before. :cry_smile:

 

[SkYwAlKeR]

yes, port and polish is a delicate process... must be done by expert or experience mech.... it's isnt alwiz "the bigger, the better"....

 

[CARENT]

bumps...

Anyone with a 4G93P head for sale???

 

[SkYwAlKeR]

bumps...

Anyone with a 4G93P head for sale???

http://z4.invisionfree.com/Saga_Iswara_Club/index.php?showtopic=6153

 

[D-IV]

Shiroitenshi,

Yes, your concept is correct. Port and polishing is an art but also requires flow bench results. Increasing the port size does not mean you are increasing air velocity with less resistance which is the main reason why we port it.

When i say increasing port size, meaning bigger and bigger and bigger..

 

[CARENT]

bumps.....

 

[Shinjite]

PNP needs to be bench flowed....

 

[D-IV]

How much is the price difference when doing PnP using CNC and by manual?

In you guys experiences, which place is best to send it. I might wanna try sending my spare head for PnP and valve job. PM me details if its too sensitive.

 

[zakie]

mahal nya...... port & polish jer bro.... agak2 laaaa sampai 1800.... bukannya kena angkat engine, bukak cover head pastu bukak head je..... 4g63t pon baru RM400-500 jer cost post & polish....

 

[D-IV]

Nak send for CnC PnP 1800 ke? If that includes valve seal and valve guide change and my shipping charges to and fro. I wouldn't mind hehe..

 

[SkYwAlKeR]

How much is the price difference when doing PnP using CNC and by manual?

In you guys experiences, which place is best to send it. I might wanna try sending my spare head for PnP and valve job. PM me details if its too sensitive.

powerzone.... matspeed....

 

[mikha]

Hi all,

Any good workmanship in Ipoh that is expert in Port and Polished? Thanks..

 

[xinghonh]

my fren did his pnp gsr head at nasty port flow in usj1
and im swapping my ori gti head wid his ported gsr head
mind to ask wats the cons in porting the head???