Ported/polished head questions

[dubburke 0]

Read a bit on the G60 head being probably one of the best mods with chip/pulley.

1. Why does the boost drop with a polished/ported head?

2. Will i need bigger injectors/FPR to maximise on the extra airflow?

3. With the ported head being fitted, will the standard gaskets still fit on assembly?

4. Any beneficial things to be done while the head is off, apart from T/belt?

5. Is it worth doing the throttle body/inlet manifold aswell?

[Toad 0]

1. Why does the boost drop with a polished/ported head?

 

Boost is a measure of pressure in the inlet manifold, this pressure is the result of the extra air provided by the super charger not being 'taken away' by the engine and so it builds up. With a ported head, the air flows better into the cylinders, so a greater volume is taken by each piston stroke, therefore not as much air builds up in the inlet manifold.

So although the 'Boost' is lower, more air is getting into the cylinder, which is what you want.

 

An analogy for this is a Dam in a river, where the dam is the cylinder head. There is a certain volume of water being supplied from upstream but only a small volume can pass the dam, therefore the river level rises, if the dam is opened up a little, like the porting and polishing on a cylinder head, more water can pass through, and so the river level drops.

[Kevin Bacon 5]

1) Boost 'pressure' is the result of the compressed air working against a restriction, throttle plate, cylinder volume, head ports, intercooler, valves etc etc

 

Take the outlet hose off a turbo or charger and all the compressed air reduces to atmospheric very quickly, but connect it to an engine and there's always a restriction there to keep boost pressure up. Heads that allow more air in pose less of a restriction and the engine absorbs more of the boost, hence the drop.

 

2) Depends on the pulley size etc.

 

3) If the ports have been gasket matched, yes.

 

4) Not sure on the G60

 

5) Ditto, but probably as it's not the biggest of throttles.

 

 

EDIT - beaten by Toad, LOL!

[Toad 0]

EDIT - beaten by Toad, LOL!

 

I only got 1 though.... :cry:

[dubburke 0]

That was quick :lol:

Reason i ask is i fancy more power, but with reliability and torque.

I fancy more power, but dont want to go OTT and spend thousands :oops:

The most i would want to go to is the head done, slightly bigger injectors and a 3.5 FPR.

I have at the moment a S/S cat free exhaust, RSR outlet on charger, boost return pipe deleted, K&N panel filter, stage 2 rebuilt charger (currently reading 2050 on the MFA check)68mm pulley and chip (jabba) but i am considering an SNS one, due to bad reports i have heard of the chip being crude, would an SNS chip be more driveable and noticeably faster?

[iow_corrado_g60 0]

defo worth getting port and polished inlet mani to match your head fella at same time!

 

if your going red tops then get a 65mm toothed kit as you only really need bigger injectors over 215bhp also when running more bhp you could get the bosch w5dpo spark plugs as these run cooler thuis being more effective!

 

on the g60 if you have a f.p.r as that is primarily doing what larger injectors will do! and just supplying more pressure to the fuel rail iirc!

 

sns chip have anti lag code

 

and go and get a fully ported charger from dazza!

[dubburke 0]

Good stuff, injectors are one less thing to get then!

[g60bv 0]

i've got a p&p head with 35mm exhaust valve for sale. bullt by keith at rpm. pm me..

[eatthis 0]

1) Boost 'pressure' is the result of the compressed air working against a restriction, throttle plate, cylinder volume, head ports, intercooler, valves etc etc

 

Take the outlet hose off a turbo or charger and all the compressed air reduces to atmospheric very quickly, but connect it to an engine and there's always a restriction there to keep boost pressure up. Heads that allow more air in pose less of a restriction and the engine absorbs more of the boost, hence the drop.

 

2) Depends on the pulley size etc.

 

3) If the ports have been gasket matched, yes.

 

4) Not sure on the G60

 

5) Ditto, but probably as it's not the biggest of throttles.

 

 

EDIT - beaten by Toad, LOL!

 

 

No 2 just answered my question about y u made 12.5 psi and i only scraped 11 with the same charger :)