Just had a quick question for any of the other high powered miata turbo car owners. I am building a head and was wondering about materials for valves.
Someone I know/trust said that he has seen the nitrided black supertech exhaust valves fail in turbo motors presumably from overheating and bending and that he would only use Iconel or a different alloy like the manley race valves for exhaust valves in a turbo application
I know a lot of miata folks run supertech valves-Do you use the iconel valves for exhaust or the black nitrided valves?

 

Not a Miata, but my OTM has inconel exhaust valves and I haven't heard of anyone having problems with them.

 

Most of the folks I know who are running high-HP turbo motors (including me) are doing so on stock valves.

 

if you're overheating exhaust valves then a little water injection is the cost-effective answer.

 

Bringing this back to life.

Is this still the consensus, not to worry about Iconel exhaust valves if your have sufficient cooling and are not constantly in boost on a track with constant loads? I'll be aiming for 300whp but mainly street driven.

 

I was doing it for peace of mind. Probably not necessary, but feel better about it. Figured running anti lag would be hard on normal ones.

 

If you have the option of inconel and the pocket, go for it. Stands up to exhaust abuse much better whether it be a result of ign retard or antilag etc. With heat so close to the exhaust valves, for sustained track sessions I would want the inconel

 

Just some FUD regarding exotic materials in valves;
Some valves are fused from two materials with the transition halfway up the stem. Several of them have snapped at this precise position (most examples I've heard of is from Evos).
Maybe the reason is to have normal stainless in the grove for the retainer locks, but you don't know until you use a magnet on them (no way to know when ordering).

 

Bring this back from the grave to see if opinions have changed on the subject.

I will be building a head for boost and am sourcing parts now. It will be port and polished with +1mm intake valves. Goal is about 250-275 whp or so.

The car will be mostly track driven. Does innconel give more peace of mind than the nitrided ones? Also should I be going with +1mm or +2mm?

 

I have been avidly reading and learning MT for a few years and this is the first I have heard of anyone doing it....

I stand to be corrected but believe almost everyone is using stock valves or stock type material valves...

 

Multiple examples exist on this board of burned SS exhaust valves on FI motors. I would (and did) Inconel exhaust valves for FI. Especially for any significant track use.

 

Add Beryllium seats and you should be really safe.
Used on Ford Focus engines it plays a really big role, but you have to find the material and someone willing to use it... Grinding dust is toxic IIRC.

 

Double

Edit: But there are other (non-toxic) extra cool seat materials out there than the old Cu-Be alloys.