What's the problem with a cracked exhuast manifold?

[eclipse13]

I have heard of alot of people having a cracked exhaust manifold when they go to change install there header. My question is, why is a cracked exhaust mani bad? It seems like the fact that air is escaping would be good because there should be less back pressure. I know that it isnt good to have an cracked exhuast mani, but why.

 

[TheTSiGuy]

I have heard of alot of people having a cracked exhaust manifold when they go to change install there header. My question is, why is a cracked exhaust mani bad? It seems like the fact that air is escaping would be good because there should be less back pressure. I know that it isnt good to have an cracked exhuast mani, but why.

The exhaust manifold is BEFORE the turbo, therefore inducing boost leaks. all the air/gasses coming from the exhaust manifold aretrying to create more pressure to spin the turbine wheel. Think about it, would you want a less powerful push of air or more powerful push of air to spin a wheel?

 

[TheTSiGuy]

oh wait. you're n/a.

in which case, it seems an exhaust leak shouldnt matter too much?

 

[onepimpclipse]

Aside from the fact that it is loud and annoying, all of the heat is concentrated on that one spot. Which would rather quickly deteriorate other components as well as the rest of the manifold.

 

[sonicnofadz]

Beside from the extra heat,noise, and pollution, running a non turbocharged car with a cracked manifold isn't really all that bad. It will actually increase power by a very small amount. If you take off your exhaust completely from the engine (unbolting the manifold from the head) and run it like that you would gain quite a bit of power from free up the restriction of all the exhaust pipes (although your engine would be sooooo loud that getting pulled over by a pig would be inevitable). This is a whole different story on a turbo car, since a leak before the turbo would induce turbo lag.

 

[me612]

hop on evolutionm forums and read why one of their top members Al Freidman had a serious health issue which later was found to be caused by his cracked HKS manifold. Ever heard of carbon monoxide?

 

[tom1995tsi]

The back pressure on each cylinder has to be close to the same for the engine to run right. If you have a cracked manifold on one side it could make you actually lose horsepower.

 

[sonicnofadz]

hop on evolutionm forums and read why one of their top members Al Freidman had a serious health issue which later was found to be caused by his cracked HKS manifold. Ever heard of carbon monoxide?

Wow thats really strange. I wonder if this is a common thing or not among tuner/car people?
How would a crack in the exhaust manifold cause him health problems? Did he work on the car alot while having the engine on?

 

[leet]

Because the exhaust gasses might be able to concentrate in the cab of the car.

Everywhere you drive, it's like a gas chamber.

I just found a crack in my 2G manifold. Time to get an EVO mani

 

[me612]

Exactly. Just think about it. You gotta crack in your manifold, so your exhaust is leaking in you engine bay. Say you have your vents on and some of that air is coming into the cab while you stopped for 3 minutes at a stop light, and you're in heavy traffic. I don't know his exact case, I just know he was having severe headaches that he couldn't expalin, and eventually found this crack. Got a new manifold, headaches went away. Prolly had a little bit of carbon monoxide poisoning which could lead to some bad sh!t. So I'd keep that in mind if you're driving around with a crack in the manifold.

 

[talon615]

Obviously replace manifold but check you manifold studs and make sure the head isn't warped where the manifold bolts to.. Very common in DSMs. Also buying an EVO mani is only gonna cost you more money that could be used on something more interesting. Ported 2g manis are the best you can buy in fact, any turbo upgrade on a 1g or 2g recommends you buy a ported 2g exhuast manifold.. Don't believe me? Look it up anywhere...

 

[leakyfaucet]

It will actually increase power by a very small amount.

Nope. Quite the opposite. N/A or not.

 

[aleccolin]

Beside from the extra heat,noise, and pollution, running a non turbocharged car with a cracked manifold isn't really all that bad. It will actually increase power by a very small amount. If you take off your exhaust completely from the engine (unbolting the manifold from the head) and run it like that you would gain quite a bit of power from free up the restriction of all the exhaust pipes...

Seems reasonable, relating to the idea of a decrease in pumping losses associated with "restrictive" stock exhausts and intakes, but isn't correct. Most N/A cars will see a significant decrease in power, especially in the low end (what most people would refer to a "torque"). Headers with larger than stock primaries will, on most N/A cars, increase higher rpm horsepower to the detriment of some low rpm grunt. After a certain distance the exhaust gases cool and slow down enough to benefit from a larger exhaust pipe, but this is generally after the header(s) and collector

 

[leakyfaucet]

Seems reasonable, relating to the idea of a decrease in pumping losses associated with "restrictive" stock exhausts and intakes, but isn't correct. Most N/A cars will see a significant decrease in power, especially in the low end (what most people would refer to a "torque"). Headers with larger than stock primaries will, on most N/A cars, increase higher rpm horsepower to the detriment of some low rpm grunt. After a certain distance the exhaust gases cool and slow down enough to benefit from a larger exhaust pipe, but this is generally after the header(s) and collector

That all sounds like it makes sense, but according to the countless car gurus and dyno after dyno I've seen of a car that swapped in longtubes, the low end torque does not decrease. You would think that it would, but actually it has something to do with sound and pressure waves. These were all mustangs, if that matters.

 

[aleccolin]

according to the countless car gurus and dyno after dyno I've seen of a car that swapped in longtubes, the low end torque does not decrease.

Long tube headers, while they may and often have larger than stock primaries, use the extra length of the tubes before the collector or dump to create more backpressure than a header of the same primary size, but shorter length. This is how they manage to maintain some low end, and is also why they are most common on street vehicles.