Head porting and polishing on a K04???

[Poverty]

Also...

The very thin air attached to the ports themselves is boundary layer, flow sits on top of the boundary layer and on occasion can be turbulent. Not always a bad thing.

Some race engines (NA) used to use a sliding plate throttle which had no butterfly and therefore no restriction.

Wasn't always best.

Shiny and smooth isn't always best there more too it than that

Yep exactly what RD said too.

Robh if you are going to get your cylinder head done, get it done by pro's. Either APR's or race developments. So much more to cylinder head design than just making everything smooth!

[sub39h]

every day's a school day 

[Poverty]

every day's a school day 

Trust me, ive only just learned all this myself as its being done to my car.

I used to think it was just all about making things smooth and shiney. Never knew a existing cylinder head can be extensively re-profiled for racespec applications! 

[RobH]

Also...

The very thin air attached to the ports themselves is boundary layer, flow sits on top of the boundary layer and on occasion can be turbulent. Not always a bad thing.

Some race engines (NA) used to use a sliding plate throttle which had no butterfly and therefore no restriction.

Wasn't always best.

Shiny and smooth isn't always best there more too it than that

Yep exactly what RD said too.

Robh if you are going to get your cylinder head done, get it done by pro's. Either APR's or race developments. So much more to cylinder head design than just making everything smooth!

Im going to wait the outcome of Steves headwork and then maybe APR can comment on potential gains on a K04 and if its worth it, taking price into consideration. Im mainly comparing this to wmi and thinking this route is better

[Poverty]

Also...

The very thin air attached to the ports themselves is boundary layer, flow sits on top of the boundary layer and on occasion can be turbulent. Not always a bad thing.

Some race engines (NA) used to use a sliding plate throttle which had no butterfly and therefore no restriction.

Wasn't always best.

Shiny and smooth isn't always best there more too it than that

Yep exactly what RD said too.

Robh if you are going to get your cylinder head done, get it done by pro's. Either APR's or race developments. So much more to cylinder head design than just making everything smooth!

Im going to wait the outcome of Steves headwork and then maybe APR can comment on potential gains on a K04 and if its worth it, taking price into consideration. Im mainly comparing this to wmi and thinking this route is better

Id do both! Well I am anyway lol. Biggest downside to the WMI kit I will be running is the tanks gonna take up space.

[RobH]

Also...

The very thin air attached to the ports themselves is boundary layer, flow sits on top of the boundary layer and on occasion can be turbulent. Not always a bad thing.

Some race engines (NA) used to use a sliding plate throttle which had no butterfly and therefore no restriction.

Wasn't always best.

Shiny and smooth isn't always best there more too it than that

Yep exactly what RD said too.

Robh if you are going to get your cylinder head done, get it done by pro's. Either APR's or race developments. So much more to cylinder head design than just making everything smooth!

Im going to wait the outcome of Steves headwork and then maybe APR can comment on potential gains on a K04 and if its worth it, taking price into consideration. Im mainly comparing this to wmi and thinking this route is better

Id do both! Well I am anyway lol. Biggest downside to the WMI kit I will be running is the tanks gonna take up space.

Tbh i am ultimately heading that way anyway

[Poverty]

With the right WMI kit, I wouldnt be too frightned to tune for it, just make it aquamist.

[RobH]

Was thinking Devils Own, well thats what statllers use.

[DaveB@Vagbremtechnic]

It's the same principal as used on an aircraft wing, fast flow is great for high speed but you want a lot of density ie a weight of air acting on the control surfaces so that they don't need to be very big and save weight or you don't need to deflect them very far.

So vortex generators are used, these increase drag and promote turbulent flow which powers certain bits of the wing stab or rudder on your aircraft

Back to an engine if you had smooth flow travelling fast into your engine cylinder you'd have fast flow but low density, by slowing flow you increase density and therefore ore O2 and more power. So Manaufacturers focus on smooth flow and lots of breathing to reduce power and improve emissions. So plastic inlets and 4 valve heads for your 1.0 ecotec three cylinder corsa are the order of the day.

For you rip snorting mk5 you need lots of flow of air that becomes turbulent just prior to the inlet valve so generally a wider smoother inlet with the exit of the inlet matching the head perfectly which invariably will need opening out.

There's a trade off for the OEMs in producing more power against more emissions there'll be a sweet spot between poke and smoke that they'll juggle to sell more cars to enthusiasts like us or emission conscious company car users who are sensitive to CO2 figures

For those interested the same principals are used to keep your easyjet in the air and more power in your VAG are the same, google Boyles law for more info

[vRSAlex]

Don't forget that a good ported head also flows faster as well as flowing more air.  The faster the flow the faster the turbo will spool.  With a ported head the aim is to get 100% air in and 100% air out.  If you can't get all the air out fast enough then efficiently drops.

I use JNL for all of my ported heads.  Costs are around 850 with new stem seals etc.

AEM wmi kits for me.  Got one waiting to be fitted to the vRS.

[vRSAlex]

It's the same principal as used on an aircraft wing, fast flow is great for high speed but you want a lot of density ie a weight of air acting on the control surfaces so that they don't need to be very big and save weight or you don't need to deflect them very far.

So vortex generators are used, these increase drag and promote turbulent flow which powers certain bits of the wing stab or rudder on your aircraft

Back to an engine if you had smooth flow travelling fast into your engine cylinder you'd have fast flow but low density, by slowing flow you increase density and therefore ore O2 and more power. So Manaufacturers focus on smooth flow and lots of breathing to reduce power and improve emissions. So plastic inlets and 4 valve heads for your 1.0 ecotec three cylinder corsa are the order of the day.

For you rip snorting mk5 you need lots of flow of air that becomes turbulent just prior to the inlet valve so generally a wider smoother inlet with the exit of the inlet matching the head perfectly which invariably will need opening out.

There's a trade off for the OEMs in producing more power against more emissions there'll be a sweet spot between poke and smoke that they'll juggle to sell more cars to enthusiasts like us or emission conscious company car users who are sensitive to CO2 figures

For those interested the same principals are used to keep your easyjet in the air and more power in your VAG are the same, google Boyles law for more info

Which is why the inlets are rough and the exhaust ports smoother.  Knife edging is also bad for inlet ports.  Might look good, but look at the front of a plane wing.  They are not knife edged.

[DaveB@Vagbremtechnic]

Yep adds drag until you're doing 800mph+

Leading edge radius is mucho important for attaching the flow over the wing, aero designers will promote flow to the max and then make it turbulent and dense at exactly the point they want off their choosing, the more flow they can create (turbo) or smoothing gives them more options.

Think of porting as increasing the ring main voltage of your house to 300V you're increasing the amount of energy available to you to use as you wish. If you don't have that energy (240v) then your options are reduced with what you can do with it

I know LOBA do CFD for head work and turbo design it's a given that APR will be doing so too.

Air acts in the same way as water for design work

[RedRobin]

There's a trade off for the OEMs in producing more power against more emissions there'll be a sweet spot between poke and smoke that they'll juggle to sell more cars to enthusiasts like us or emission conscious company car users who are sensitive to CO2 figures

....This is the bottom line (plus cost factors of course) - Designing cars fit for purpose. Some folks want to redesign the purpose of the OEM car.

As aftermarket expert specialists develop one or several parts, then there must be a knock-on effect - Where does it stop? Even if you start off by swopping the whole engine and transmission to one which delivers much more performance out of the box, you then have to consider how that added power is transmitted and handled by the chassis and suspension etc. It's a very slippery slope even without any polishing.

Also, reliability surely also has to be considered - Cars modified way beyond OEM tend to break more easily. There are plenty of examples on this and other forums.

I've always wondered what percentage of GTI (for example as it's a variation from the standard Golf)) sales are modded by purchasers and whether Volkswagen actually care and cater for this.

[Poverty]

Was thinking Devils Own, well thats what statllers use.

Well it obviously depends on budget, but if money's not an issue it has to be aqua mist every single time. Aqua mist is a proper "3d" type kit whilst all the other are just basic boost controlled 1d systems.

Aqua mist was run by every single WRC team except citroen till it was banned in 2006.

It's about double the price of the AEM kit but IMO well worth every penny and it gives piece of mind that you can rely on the system.

[SteveP]

If you think that you can port a head and instantly gain 50bhp, i think you might be wrong. 

I think steves 50bhp increase will be made up of cumulative mods and the fact it probably wasnt running full beans before hand.

Mine was running full beans before the head work according to the APR calibration engineers.