Backpressure.

[VTEC_YO]

These threads are all over the internet but I am trying to get a straightforward answer. Does an engine NEED backpressure? If so, how much? I was thinking about headers, and no cat, and no resonator to go with my 14 inch magnaflow muffler and I want my engine to stay healthy.

[garrisonboobs]

i don't know how much but yes it does. I took my cat off of my miata and left it to straight headers and i barely got any acceleration lol. but people go straight pipe so as long as its connected i think it'll work.

[VTEC_YO]

Well I will still have the exhaust and muffler I just don't know how much I can get rid of. I'm more worried about engine damage than anything. I've heard things about burning valves and stuff...

[Snowfork]

You need about 0.5 psi on an inline 4 or the EGR system will suck the Air/Fuel mixture out of the head.

[Snowfork]

It can recirc the mixture and cause your in cylinder mixture to jump from lean to rich and back at random.

[nycGT]

If u want to be safe get a high flow cat and skip the header. It's going to be a bit loud but still work out

[Jasonhughes2009]

1/2 lb of pressure at WOT. if not at least a half pound your post cat o2 sensor is going to throw codes at you. your going to get terrible fuel mileage and power due to the air fuel mixture flowing right throughand out the combustion chamber during valve overlap. what you could do is go get a pressure gauge that does low readings and an o2 adapter and thread it into one of the o2 sensor holes and crank the engine and see what pressure it reada out at WOT

[2000celicagtmg]

Why not just go with a performance cat that has the hookups and a diff exhaust??? Magnaflow will work with you to Tune your exhaust system to get the max pony power out of your individual vehicle.

[subspec]

Shakes head. Look up Bernoulli's principle, this is why back pressure is so important.

Air/gasses have the same characteristics as water. If you go too big or eliminate too much backpressure you are essentially slowing down the velocity of the gasses coming out of the motor. Essentially making your motor push harder to remove the gasses.

[Snowfork]

Originally Posted by subspec

Shakes head. Look up Bernoulli's principle, this is why back pressure is so important.

Air/gasses have the same characteristics as water. If you go too big or eliminate too much backpressure you are essentially slowing down the velocity of the gasses coming out of the motor. Essentially making your motor push harder to remove the gasses.

I think we are the only two people on this forum that have even the most remote understanding of Bernoulli's principle. Fluid dynamics isn't exactly in the usual curriculum.