kojab
I would predict that a 1mm larger inlet valve would drop boost pressure slightly not increase it.

I think that's what he meant anyway

Well one thing sticks out a mile and that is Jason and Rob have proved you don’t need 1mm bigger valves to make impressive power.

That is a point but how about reducing the standard valve size by 1mm? Would you make the same power??
Don't think so.
The larger will produce more power. Bigger capacity engine will too, bigger turbo will too, bigger budget, etc etc.
If Ferrera cannot help you simply fit what a large percentage of the racing community use. Supertech.  Proven over the whole planet so I am sure it will work with your engine. In fact I have a set of Inconel 1mm oversize valves that I would be happy to pass on to you at a heavily discounted price.
 

Any engine performance is based on flow rate. If you can improve the flow, you can improve the performance.
With a turbo engine, you can indeed improve performance by increasing boost, which ultimately improves flow, though you get the side effect of additional heat. Wouldn't it be best to improve the natural flow of the engine thereby requiring less boost to get the same power and decreasing heat?
Oversized valves definitely improve performance on a NA engine so why not a turbo engine too?
I bet you have all upgraded the exhaust systems on your cars. Why? To increase flow. Why not improve it on the intake side as well.
Sure some of the guys have impressive power figures with their street cars. I'd like to see those engines perform reliably under race conditions. It is a totally different story - much harsher with a LOT more heat being generated. Decreasing heat is the most important thing to chase in a turbo race car, not power.

1mm of extra valve versus a different valve lift versus more duration etc etc etc 
 
Apples and oranges guys! there are more than one way to skin a cat. 1mm is stuff all, and is only the valve not the whole port.
 
Upping valve sizes is quite old school for heads with rubbish flow and not as important for a 3SGTE/5SGTE than a N/A engine. Our heads flow quite well and really a clean up of dags, port matching, different valve seat angle and "maybe" some bowl/throat work is all that is required to be considered full on in my eyes.
 
Also boost is a function of restriction not necessarily just "flow"
 
These are all the reasons why i did not do this to my own engine and only cleaned up dags, 3 angle valve seat cut and port matched the ports. Glad i did not just buy them because "everyone on MR2OC uses them" which was the way to go at the time.
 
 

I had a dodgy batch of valves and ferrea replaced them no problem. Im surprised that these valves were sold to you as late as 2013, Im thinking the vendor sold you those having known about the dodgy batch and should have checked. Do you have the part numbers so I can compare to mine?

track_mr2

Admin
I'm thinking of buying Supertech TIVN-1012 stainless steel with black nitride coating as per this page -
http://www.supertechperformance.com/cat-ivalves?mk=10&ca=398&en=60
Does anyone object?

I have a feeling these guys are using the same one's (autocraft-uk) but might be worth dropping them an email or giving them a call as they seem to turn out a lot of top end engines and they say the valves they run are up to the task, not mentioning the brand though.
 
http://www.autocraft-uk.com/page24.html
 
They list out there builds and they use a 1mm oversize on the intake.
 
http://www.autocraft-uk.com/page28.html

Thanks though the photos on their site shows Ferrea valves. I'm not going to use them again.
FYI I bought Ferrea because I had used them in my Escort race car without issues. I don't follow what others do (as in on the MR2OC forum). I like to come up with my own ideas. That's probably why my engine fails so often!