Hi. My question is geared more toward the stock manifold of the twin turbos vs. a single turbo manifold.

Lets consider that one of the biggest weak points of the stock twins is the cast iron manifold. Two particular weak points are

1. the cast iron manifold absorbs a massive amount of heat and
2. the cast irong manifold is prone to cracking due to this heat

It can also be said that this retention of heat by the manifold and subsequent radiation back into the block will cause coolant seals to die an early death.

What do you think would help minimize the effect of these issues more - Cryogenically freezing the manifold or applying some kind of performance coating such as Jet Hot?

Why?

Thanks.

Cryogenic links:
http://www.diversifiedcryogenics.com/whatiscryo.htm
http://www.300below.com/site/home.html

Performance Coating links:
http://www.hpcoatings.com/
http://www.jet-hot.com/

 

I don't see how cryo treating will change the amount of heat the exhaust manifold will see.

I can't imagine the jet-hot would do much good in that area either.

 

/\ agreed.

 

I don't think anything will really help as the cracks are caused by the stress of heating and cooling cycles and no coating will help that.

Coating the manifold with some sort of thermal barrier would help keep heat in the manifold and out of the engine compartment but it won't prolong the life of the manifold itself.

 

FC3S.org claims that cryo treatment assists to limit warping, cracking, and wear.

 

I agree that the performance coatings will probably only keep heat in the manifold.

That is exactly why I started thinking of the Cryo treatment.

The cryo treatment appears to make the molecules more dense and is supposed to increase the thermal efficiency of metals which is why some engine builders including Pineapple use that on parts that are exposed to high heat.

I'm thinking that the cryo treatment might help decrease the stress of the cooling cycle by decreasing the temperature changes to which the manifold is subjected.

 

I would think the coating would be better since it wouldnt allow it to rust for starters that is part of the weakening of the metal that allows for cracks to happen. Has there been enough evidence yet to support cryo-treating?

 

Incorrect. Rust isn't what weakens the metal in this case. Its the extremely high temps the manifold is exposed to.

 

I agree but in the case of the exhaust manifold iteself I don't think it will cure the cracking problem. The manifold has great changes in wall thickness throughout the casting and this is what causes the cracks to form in the places they do. When it gets down to it the exhaust manifold is fundamentally flawed when strictly viewed as a study in casting and though cryo treatments may help I don't feel this would solve the problem as it doesn't fix what's really wrong. I've got no proof but that's my opinion.

 

Cryotreatment sounds like a very good candidate for reducing the cracking problem. A very good paper on cryotreatment can be found here:

http://www.bso.uiuc.edu/~chillar/Cry...ntofMetals.pdf

In one case, controlled cryotreament was found to roughly double the torsional strength of cast iron.

 

Yeah, its hard to say one way or the other. I put an email out to the cryo people inquiring. Maybe I'll forward them this link as well.

Even if it did not help the cracking problem, I wonder if cryo treatment would decrease the heat retention of the manifold that is believed to weaken the coolant seals...

 

Interesting study. But would it be worth it to spend the time and money to get the exhaust manifold cryo-treated (and even that may be no guarantee it won't crack), when there are a lot of other problems associated with both its overall design and the design of the stock turbo assembly?

 

Why not do both

 

Are you talking about coating the inside or the outside of the manifold?

I would think you would be worse off coating the outside (since then you're not letting it cool itself by radiating heat, thereby causing it to get even more hot) and better off if you coated the inside (since then you're not letting the heat into the manifold in the first place, more of it should go through the turbos and out the exhaust)

Am I missing something? Is it really hard to coat the inside of the manifold?

 

Considering the size of the manifold, not really. I have a guy that does coatings locally (owns an industrial coating shop) that could probably do a ceramic for about $120.

 

From what I've read, cryo treating greatly aids in dissapation of heat as well as strengthening the metal itself. If you read under cryo treating brake rotors (which is one of the most common applications of cryo treating) it says it makes them 300% stronger (so less prone to cracking), and doubles their thermal efficiency I believe (since they are now much better at disappating heat. But then again, physics is NOT my strong point so...

 

I know some time back Carlos Iglesias experimented with all different types of ceramic coatings - from what I recall, he never found a coating that could, over time, take the intense heat in the manifold and turbine housing. They ALL flake off over time.

Not sure how much cryo treating would help.

Big thing with cracking is as long as it doesn't compromise the gasket sealing surface, it's really no big deal. Exhaust gasses could care less how the manifold looks.

Dale