(Maybe dumb) question on headers?

[Yater]

Hi guys,

Not planning to put onese in my car,

But just wondering out of curiosity:

I see there are a lot of aftermarket headers leading to 4-in-1 exhaust manifold configuration on each side. I think many brands claim gains on horsepower.

However, since these are aftermarket (hence I assume "generic"), how do we know, apart from testing on the dyno, that the design (lenghts, etc) does not harm rather than benefit the performance?
I may be totally wrong, but in order to bring extra performance, it should be very well tuned with the valve timing of the engine, otherwise the pressure waves reflected at the junction could reach the cilinder exhaust ports at the wrong timing and penalize performance rather than help, isn't it?
The solutions being "standard" for different engines, heads, cams... i wonder about it.


Again, not willing at all to discredit the benefits claimed by manufacturers who probably know very well what they do, it's just out of curiosity.

[Yelcamino]

Here is a link to more header info than you probably want to know!

Unfortunately, generic headers are just that, generic. Unless the header is built specifically for the application, they can actually hurt performance more than help.

[ArisESQ]

Originally Posted by Yater

Hi guys,

Not planning to put onese in my car,

But just wondering out of curiosity:

I see there are a lot of aftermarket headers leading to 4-in-1 exhaust manifold configuration on each side. I think many brands claim gains on horsepower.

However, since these are aftermarket (hence I assume "generic"), how do we know, apart from testing on the dyno, that the design (lenghts, etc) does not harm rather than benefit the performance?
I may be totally wrong, but in order to bring extra performance, it should be very well tuned with the valve timing of the engine, otherwise the pressure waves reflected at the junction could reach the cilinder exhaust ports at the wrong timing and penalize performance rather than help, isn't it?
The solutions being "standard" for different engines, heads, cams... i wonder about it.


Again, not willing at all to discredit the benefits claimed by manufacturers who probably know very well what they do, it's just out of curiosity.

While some headers may perform better or worse than other headers, from what I've seen, all headers seem to make more power than stock cast manifolds.

So while there is likely a little tuning and research that needs to be done to optimize the performance of a header on a particular engine, I think you'd be seeing an improvement over the stock manifolds no matter what header you end up choosing.

[Twoblackmarks...]

If you made the optimal headers for your engine, they would probably not fit very well in you car.

So they become a compromise.

In a regular 90 degree V8, with the "uneven" firing order they are not so sensitive to primary equal lengths actually. It is more important to just have them long enough. And the right size.

Atleast that is what I have read in most tests.

It is of course an myriad of possibilites whit sizes and stepped primarys and 4-2-1 vs 4-1, collectors and such.. And a price difference too..

If you would make tuned length headers for a 90 degree V8 it would be like 180 degree headers that "simulate" an 180 degree even fire V8, that makes the primary pipes very long and hard to fit, and that length would maybe(?) not be optimal.

I am no expert, but it seems like you could maybe compare it to an dual vs single-plane intake manifold difference. Where "untuned" headers make better overall power in a 90 degree V8 and tuned is more for a typical high RPM window.

Maybe...

[tungstenkiller]

Headers are tricky. Ive worked with many engine builders building headers for show cars and all out race cars for a while now.

The manufactures are building exhaust system with many limitations that dont apply to "us" (performance oriented enthusiasts) that is why many aftermarket companies can claim better performance but you must also ask yourself where in the rpm band are they better?

To answer your 2nd question yes the must be built to take in consideration all the things that you mentioned. BUT there are some generic changes that can be made to make the stock herder design "generically" better.

To get the best performance a custom set should be built. But it in not typically in the budget of the build unless it is a race car or no one makes headers for the application that someone has put together, at least this is what i have found in approx a decade of building headers