Are open headers bad for a car? I want to put shorties on but my current exhaust is a Y pipe and a few feet of pipe...

>Open headers can be rough on your valves in cold weather
how?

I don't know if it's true or not but apparently your engine can suck cold air in when you shut it off and it fucks with your hot valves

opposed to the cold wet air it sucks in through the intake every other revolution?
sounds like total bullshit

Open headers will make the engine run lean which can melt some surface hardened valves. Cold air wont do shit.

There is a reason that rhe exhaust comes to a Y. You will probably be okay for a short period of time but eventually you will cause engine damage from running too lean. You will also loose horsepower due to the loss of exhaust scavenging from exhaust pulses. Exhaust scavenging is a very precise science and critical to proper performance.

hahaha ok

but he's right.
the length and diameter of the exhaust pipes are engineered to create a smooth flow with momentum. the momentum helps draw the exhaust out of the cylinders (partial vacuum), leading to a minor improvement in power when cruising. it's not a lot, maybe 1-2 hp, but it's there.

I Would think of is the super hot Gas blasting on parts under the car, a simple turn down would stop that, other then that as long as your not idling around for a long time and killing brain cells you should be fine

he's right, open headers will cause damage, It can burn exhaust valves

Your exhaust valve heads will slowly warp from the engine running too lean and eventually play pinball with your piston head or you will experience compression loss

It will not hurt valves. What will hurt them is running the engine with no manifolds or headers. Headers are more ran long enough to not pose a problem. You will just die from exhaust gas poisoning, long before you hurt the engine.

No.
He's not right. He's wrong.
The manifold and collectors have an influence on wave and harmonics. The rest of the exhaust is just there to get the gases out the back of the car and quiet down the exhaust to a tolerable level.

but you're wrong.
anybody who's fucked too much with his exhaust line will tell you the same: there is a point where removing things will hurt performance, and that is before it comes to the collectors

the exhaust valves genius

...

ugh
try it if you don't believe me

>anybody who's fucked too much with his exhaust line
I just can't believe this. No one will have done back to back engine testing with different sections of exhaust removed.
You might like to think you know what you're talking about but you don't.
The manifold is important, everything after that is just to guide the gases to the back of the car.

I have no idea what you mean by this.
explain yourself

>No one will have done back to back engine testing with different sections of exhaust removed
actually it is a certainty that at least someone has done it

will probaby rust up ur exhaust valves if they get wet

yes, engine masters did it.
they found open headers made most power:
youtube.com/watch?v=_PVXvHkr-Vs&t=742s

Not the otuer user, but my degree was in acoustics engeering; standing waves, resonance in tubes, that sort of thing.

The most important factor in determining resonance in a tube is its overall length. Changing the length of the complete exhaust system will absolutely have an effect on scavenging.

they get wet all the time.
combustion products are mostly h2o and co2, every time the engine heat cycles water will condensate in the exhaust.

True, but the reflection from the exhaust exit is not used to tune the scavenging of the combustion chamber. Its the first reflection from the change in area where the header primary mergers the collector that matters. The wave reflected from the exhaust tip would arrive too late to have a marked affect.

Doesn't that depend on backpressure/scavenging, and valve overlap/charge pulse?

youtube.com/watch?v=rTlHEOE2Zp4

two actually informative posts on Veeky Forums
many thanks kind sir

...vs mufflers. And the open headers with 18" extension shows more power on the dyno. (10:25 in the video)

Check the cast vs headers episode, it makes a difference from the valve all the way out. Every single item changes things in subtle ways.

>Every single item changes things in subtle ways.
I'm not denying that, I'm saying the manifold design, primary length, diameter and collector design has a much greater affect on engine performance than the length of the complete exhaust system.

i meant they might oxidize while sitting

but yeah nothing to be worried about

I'll refer back to the engine masters videos.

The full length exhaust robbed like 50 hp and the cast manifold vs headers was worth about 10hp.

Check the header bash video, it barely made a difference.

whats your point?

My first point was to contradict
>open headers made most power

Then I went on to do the same to
>manifold design... has a much greater affect...

Anyway, my 3D print is done, and it's 4am so I'm going to bed.

Cheers!

but you did neither of those things.

You stated the full exhaust system made a 50hp loss over open headers and changing the header design was worth and extra 10 hp with the better design.

not him, I've tried following the conversation from the beginning, tbqh I don't know who's trying to state what anymore
wasn't it another dude who said open headers was better than full exhaust?

>Will it damage my engine?
Only if it runs lean, so it depends on where your O2 sensor is. On carbeurated setups this is less of an issue

>Will it hurt my valves?
Only if it runs lean. Simply reducing exhaust length will not hurt anything directly.

>What's bad about it then?
Aside from noise and possible CO buildup in the cabin? Loss of low-end torque. "Backpressure" is a myth, but scavenging is not. Open headers will make more power at high rpm due to less resistance, but noticeably less power at low rpm (depends on the engine)

>What about the myth about condensation on valves?
Only really an issue if you don't let the engine hit full operating temperature. Same goes for oil. Air moisture will get in regardless. This can be a real problem if you run without an exhaust manifold/headers period, but otherwise it's no worse than letting the car sit for a while.

I've run open headers / straight exhausts on several high-hp cars. No issues, especially if the A/F Ratio is properly handled. You will wind up "driving by sound" to an extent. Most of the power loss is in people's heads.