Mixedfruits

Title reads the question.
Been hearing that mufflers provide down pressure or something of sorts to help the engine and with out the mufflers the head will dry out head not headers. Anyone know anything about this?

Carsy

I have run motor cycles without mufflers for years without any adverse effects.

Mufflers do add back pressure to to the combustion system .

I dare say the modern car engine is designed to give optimum performance with this back pressure.

Some have said that lessening the backpressure can burn exhaust valves.

I would say that this would not happen overnight!

RLE

I think YOUR head is dried out. That's what I think.

And, it's backpressure.

GHAZAN

i don't see how exhaust valves will burn with less back pressure. If it's less back pressure, exhaust should be leaving at a faster velocity. maybe someone with more knowledge will clarify

Mixedfruits

Thanks for the helpful comment lol

Carsy

Exactly ,I would have thought that shutting hot gas off at a greater velocity will create more wear on the mating surfaces. .

C300Sport

With nothing else changing, reduced back pressure can cause an engine to run lean and hot (more air sucked in with the same amount of fuel injected) with the exhaust valve generally being the first part of the engine that may have issues.

jctevere

The exhaust as it exits the piping is moving in the form of pulses or pressure waves with varying speeds and pressures. These pulses have mass, and want to continue moving at a high rate of speed. These pulses if they are moving fast enough, will create a low pressure region behind them and will help draw out more spent exhaust from the engine, and will create a region of lower pressure inside the exhaust manifold.

If the system is too short, the fast moving pulse will collapse as it exits the end of the pipe, and the low pressure wake will also collapse, reducing the scavenging effect, especially at low RPM. This will be felt as a decrease in performance right off the line.

As RPMS increase, the speed and frequency of these pressure waves increases, negating some of the performance losses and restoring the scavenging effect.

Exhaust scavenging is a function of velocity, not backpressure. Having lower backpressure is a good thing. If a modification decreases the velocity, then a low RPM power loss will be the result. In the case of cutting off the muffler and not at least replacing it with a straight pipe, this modification is reducing the opportunity for the exhaust to built up and keep the speed, and it instead slowing down the exhaust as it exits, creating more backpressure than the stock muffler.

An x-pipe creates a cross flow which allows the pressure waves to accelerate each other and create a positive induction.

If you replace your muffler with a piece of pipe, you will get the sound you are probably after without loosing the velocity that is essential to produce power.

RLE

This is just an old wives tale from decades past. It was thought by some that after shutting down, cold air would rush up the pipe and warp something.

Now I ask you, does this make sense?

RLE

This theory is wrong. Intake air is measured by the mass airflow sensor which sends a signal to the engine management computer which, with other inputs, determines how much fuel to inject.

Even carbureted engines operate this way although jets have to be changed to supply more fuel at high rpms.

The Porsches I owned with Weber triple throat carbs were modified with larger venturis which meant larger idle and main jets. But, enlarging the venturis meant a loss of low end torque. It's a tradeoff.

And, 4-valve heads without variable intake cam timing also costs low end performance.

C300Sport

The theory is actually perfectly sound. It seems like your argument against it left out my "with nothing else changing". I was just stating what happens with no engine management or other variables.
I opened up the exhaust and intake on my old school carburated bike and was running way to lean. If I wouldn't have rejetted, I would have fried the valves within 1000 miles.

envyxc350

I cut my mufflers off a while ago on the 350, no problem at all. And I drive it like I stole it every time. Then I installed headers and cat delete and put mufflers back on as the sounds was to much.

C300Sport

How was the exhaust tone with the muffler cut out?

Mixedfruits

great only around 2k its very annoying and around 1k-2k there is a noticeable vibration in the cabin 2.5k------- sound like xpipe muffler at 3k but a bit louder and for the whole duration instead for a little time. Outside the car I havent let anyone drive my car so idk based on friends, they say sounds great maybe at peak legal sound 95db in cali

wnunez89

was there any fitment issues with your headers?

tanktube67

Is not bad for your engine, you may get some power increase and laud exhaust sound with vibration.

Mixedfruits

headers? my mufflers was taken off didnt even touch my headers lmfao

kirillbenz22

that was right on by the way you couldn't of explained it any better, and I am not beeing sarcastic. I have no mufflers with an xpipe for over a year and a half and no problems so far... and i drive it a LOT!

kirillbenz22

BTW less back pressure less torque. Some say more horespower.

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