largest available valves for rs2

[A80Avant]

i have been talking to my mechanics and it seems that the 0.5mm oversize valves are somewhat too small of an upgrade if you are to do an upgrade to the valves anyway. SO what other options are there?

[Rusty]

Speak to RWD19T, he knows plenty about the I5 head

[Billman]

i think there is not much space to go bigger than 1mm anyway because the spark plug hole is near.

[Audi Parts Guru]

There is absolutely no point in trying to fit larger valves in the 20v head. You would be much better off in getting the ports modified to increase the airflow. Just a few small modifications in the right areas of the port could make a big difference in air flow

[a4kquattro]

you can get 2mm oversize. I also agree with the consensus that you need port work before the valve upgrade will do much. I do think the 2mm valves would gain on a ported head vs the "standard" .5mm oversize. you will need new valve seats too if you go up to 2mm.

[A80Avant]

the idea is to port and fit larger valves at the same time, BUT only if the gains to be made are good enough. The plan is to have the head ported anyway, and initially was to fit the original valves.

[JP]

You can get 2mm oversized for the intake but this is no good for turbo use only for n/a use as the flow balance between 2mm oversize intake (needs oversized seats fitting) with a 0.5mm exh valve (recut original seat) is just not suited to forced induction use.

You can get custom valves made in min quantities but by fitting a larger exhaust seat you are going to hit the combustion chamber wall and shroud them too much seeing no extra gains. Plus you would need to weld up the spark plug hole and rethread so you can fit the smaller motorbike plugs.

Stock valve size reworked will see around 10-15% gains on the intake and anywhere between 20-40% on the exhaust depending how drastic the port workup is. Fitting an oversized valve will push the intake to around 20-22% and the exhaust as much as 50% providing the port design is changed to accomodate it. Again the benefits will not be seen unless you have a correctly flowing intake manifold which does not restrict your new intake ports and a good flowing exhaust mani that does not choke the exhaust ports.

As a reference point attached is my I5 head that made 528hp with now new seat cuts for oversized valves but no new port work up yet so you can see the difference in port size.

hth JP

[Jamo]

Christ i'm getting more confused the more I read, porting and valve work is more black magic than cams

[|CL|NIKI]

What kind seats we can use? Stock from other model engine, or made them? If need to made them- from what material - beryllium bronze (CoBe2) is ok but expensive... What other?

[JP]

beryllium bronze is too soft you want sintered seats like the high revving jap engines. You get them custom made if you go oversize.

[Avantus]

A correct flowing intake and exhaust manifold... does that mean that a stock RS2 (or ABY) manifold with a wagner K26 exhaust manifold will be insufficient to get any decent gains from such headwork, and so a reversed intake is a must?

[|CL|NIKI]

beryllium bronze is too soft you want sintered seats like the high revving jap engines. You get them custom made if you go oversize.

From what material?

[JP]

Avantus.

A stock intake will kill the intake flow figures by 10% on stock.ported and 15% on 0.5 ported intake. Port match the intake and you can get 5-7% back. Going aftermarket reverse wagner and port matching will not kill any flow of from ported gains on either configuration.

Niki

Here's an example of seats from us supplier

http://valvetrain.kpmivalvetrain.com/viewitems/precision-components-and-valve-blanks/precision-seats-powdered-metal?

[Avantus]

Ok thanks JP. So stock but port matched IM with headwork/stock valves will do around 10% on intakeflow, but still a big 20-40% on for example a Wagner EM... that are some worthwile gains to be had imo.

[|CL|NIKI]

IMO too.