what makes manifolds crack?

[ryu]

what are the limits on the smaller stock exhaust manifold on the 13g? how are manifold limits figured out? what makes them crack? just heat? pressure?
does more hp=more heat? im not talkin more boost. (nitrous)

 

[boostedgst2984]

yes more hp = more heat to an extent. all the heat builds up behind the turbo while your trying to force air threw the turbine. The rest of the air is sitting in the manifold. What causes the manifold to crack. Is the constant expansion and contraction of the metal. It just hits its limits and crackes under stress. usually the cracks happen round the welds of the manifold or near where the turbo bolts to the manifold. like in the middle of the 4 bolts for the dsm stock mani's. And just with weaker metal being used cracking happens more frequient.

 

[skinnyt]

aslo one other thing to.the weight of the turbo.if you got down pipe with no clamp on it like the stock ones got the manifold will crack even sooner.im just waitin for mine to crack so i can do some welding...

 

[boostedgst2984]

yea hehe mine is almost about to crack in half time to go with a 2g hehe and port it with the good ol dremil

 

[skater182]

when metal heats up it expands (iam talking glowing hot)... manifolds crack when they cool off to fast at an uneven rate

 

[Defiant]

You'll find it's more a matter of the actual grain structure of the iron being changed by extreme heating over time rather than weight or heating/cooling issues. Keep in mind that while driving down the road, the front of the manifold is being blasted with relativly cool air from the radiator, while the rear is holding most of its heat in a very cheery shade of red. It doesn't much mind the unequal heat.

 

[FireyIce01]

so in theory if you had a good heat shield in place that kept the entire manifold covered, it would be less prone to cracking?

 

[Defiant]

so in theory if you had a good heat shield in place that kept the entire manifold covered, it would be less prone to cracking?

Heat shields are to keep radiated heat from melting other stuff, such as fan blades. It shouldn't have an effect on the manifold's life.

If you buy a new one, you'll never have to worry about it again.... or do you intend to keep the car another decade?

 

[FireyIce01]

Heat shields are to keep radiated heat from melting other stuff, such as fan blades. It shouldn't have an effect on the manifold's life.

If you buy a new one, you'll never have to worry about it again.... or do you intend to keep the car another decade?

Well, yes, I prolly will keep the car another decade,, but that's neither here nor there, I still have my first car... granted it's been on jackstands for the last... 4 1/2 years... But I still have it

The thinking I was having behind the heat shield was that it would hold the hot air surrounding the manifold in better, and keep the cold air blowing thru the radiator from getting to the manifold to make such a heat differential... *shrugs* the things aren't that expensive, and for my power wants a stock 2g unit should be fine, if not a SBR cast one will do fine... so it shouldn't be an issue