A buddy was telling me about how some felt the ceramic exhaust ports to be a Porsche boo-boo. Any truth to it?

Apparently, one can get more life/performance out of the hybrid turbos with an NA head??? Anyone else heard of such a thing? I'm actually in the market for a new cylinder head at the moment. Going to do a new wide-fire because of this. Got one you'd like to part with?

I'm just getting into the turbo world, a bit of a newbie, feedback appreciated...

 

i have a 2.5 turbo head i might be selling due to the fact that it'd just be easier to use my 2.7 head in my 3.0 turbo project. you interested?

 

Jake -- tell me more.

 

i bought a 951 engine from a guy in california. right now it's sitting in a warehouse until i go pick it up sometime next week. i will be using many of the parts of that engine for my turbo project. currenty i have a 2.7L n/a engine so i will be using that 3.0 block and probably my 2.7 head. if that is the case, i will be selling both the block and the 2.5 head of the engine i just bought. if you are interested we can discuss a price....

 

I have an n/a head i was goin to rebuilt to turbo spec for the 951 block i had bought. How long would it last if i kept the n/a head as is and installed it onto the turbo. Not that i would, i still am going to rebuild to turbo specs. My request was to as if someone could stress the importance of turbo spec head vs a n/a spec head,if any? Experiences would also be appreciated

 

Sodium filled exhaust valves on the turbo head, I also think the exhaust valves are bigger.

 

Ok, what degrees does your friend have? How much time and analysis did he put into his statement? What was the reasoning or logic to his statement? What points did he bring up to support his assertion? There is a reason Porsche set the head up this way for turbocharging. It has sodium filled exhaust valves to handle the heat produced as well as the ceramic liners (they are basically ceramic tubes that the head is cast around to form a refractory - keep the heat in the exhaust, not in the head. Do you really think that Porsche would have changed so much in making the turbo (suspension, brakes, head, radiator, etc.) if it wasn't necessary? Remember Porsche was a company run by engineers, not by accountants in the days that the 944 was produced. There was always a reason for any changes made.

There are people taking the 89 944 heads and putting them on turbos (I plan on going that way on my next build), and it's worth it, but I'd also take that head out and at the least have the exhaust ports ceramic coated (better than nothing) and the exhaust valves changed to sodium filled ones.

Did you see the temperatures that the turbo sees? Under extended running the turbo housing will glow cherry red! Tell me that the exhaust ports don't need to be ceramic!

Before listening to people that have no clue, go to a PCA club race, talk to some racers that have been doing this for a long time and ask them what works. You'll cut through the usual BS quite quickly.

Dal.

 

Dal,
You need not have to go sodium filled for the
exhaust valve. There are now available valves
which are built for high temperatures.
Thermal barrier coating is a good idea.

 

This is the first I ever heard of it. So that makes this the first time I've ever heard of saying anyone that. Draw your own conclusions.

Also, this engine was designed to compete at Lemans. Which it did, taking 6th overall. So again, draw your own conclusions.

 

Dal,

My friend was EXTREMELY skeptical...he'd heard it and wanted me to confirm before I believed it. I agree, it seems intuitive that the ceramic ports would be the way to go with the temperatures seen in turbocharged engines. However, I've had enough of what I felt to be obvious debunked to ask the question anyway. Thanks for your feedback.

--Kurt

 

I have done this once before and I am doing the same thing to my conversion. I ported the head to match the turbo head. Then took the valves from a turbo head and coated the NA block.

Before anyone flames, I used the valves from the turbo head becasue the ceramic liners came apart when the 951 engine overheated and kaboom!!!!!!! Although the valves were fine the head is now a door stop. So far the NA head is holding up great but keep in mind that it is not on a racecar... Not sure how it would hold up under long term hard driving.

 

For large HP applications, most use the stock NA head as a base. The NA allows you to port the exhaust, not doable (well it costs $$$$) on the 951 ceramic ports. Sodium filled are great valves, but you can use different valves and be fine (inconel)... The 951 head in stock form with minor porting works fine. Next you get the big valves, big ports and at the top of the chain the big intake/exhaust valves. For 99% of the 951 owners, a good port job then a big valve head will be just fine!

At Lemans, the cyl. head used was different that today's 951 head.

 

Dal:

As Kurt was simply seeking infomation from this forum without having drawn a conclustion, I find your "attack" of his friend rather uncalled for...

FWIW, I am Kurt's friend. I have a BS in Mechanical Engineering and have done several quarters of post gruaduate work in both vehicular dynamics and engine development / non-destructive testing, i.e. dyno testing and tuning. I have been involved in motorsports engine development for over 20 years, raced production based cars in SCCA and have developed 2 different 944's in the last 15 years, one being a 951 for the Nevada Open Road Challenge series. I currently have a modified 993 twin turbo as well as a Spec Miata race car. If you would like additional references, I would be happy to provide them. My suggestion to Kurt was to avoid guessing as I have been out of the 951 scene for about 7 years...

With regards to Kurt's question, I have learned it best to ask questions about suspicious things when they arise. As I have witnessed many core turbo heads with damage to the ceramic port liners, I suggested that Kurt seek out advice from the 944 Turbo forum regarding the different heads before he purchases a core to rebuild. I wanted to do what I could to help Kurt avoid un-due costs associated with keeping an older 951 running. Given the nasty tone of your reply, I would guess you do not welcome such questions here...too bad. It would have been nice for Kurt to find a good, friendly resource in Rennlist. Nice going...

Regards

 

Everyone will have opinions on any question you post, As with my reply I stated that yes an NA head can be used, But then you assume everyone is going to give negative replies. When I post a question I don't reply to the negative posts and just learn from the others. For a street car yes you can use an NA head but I would change the valves and coat the ports.

 

Jim: Congrats! I guess that we all need to grow some thicker skin. No offense meant. I just wanted to point out that Porsche did all of this for a reason. If I came off a little aggressive then I apologize. My questions weren't meant as a personal attack on you, I was basically asking questions that he should have asked. I get a lot of "expert" advice that is basically BS. If I did type something inflammatory, then I apologize, sometime my fingers type faster than my superego can control them.

With your background you should have been able to answer his question about the ceramic liners (and their benefits/drawbacks) without having him come here and ask if it was a mistake made by Porsche.

Actually with your racing experience, you should be able to educate all of us on these issues? What do you think? Are the ceramic exhaust ports needed nowadays? I'm asking with genuine interest, no attack, not meaning to offend.

How about when we chip these cars? Are the sodium filled valves necessary anymore or would some other material suffice? How about dealing with higher than stock boost pressures? Any merit at ceramic coating the crossover pipe?

I'd love to pick your brain over a beer sometime - I'll buy.

One more thing.. Is that a crack on the exhaust port on that head? What happened? I've heard of them stripping, but a crack like that is impressive.

Dal.