is BACK PRESSURE a myth?

After posting about a bad cat and wondering if I should just do a cat delete everyone was saying it will reduce back pressure in the engine. I've seen this "back pressure" discusses on many other threads. But I haven't every heard of a F1 car or NASCAR having any restrictive exhaust.
I know that modern cats arent very restrictive in the first place though, but people say reduced back pressure will reduce torque. Now I have read that modern engines are designed with back pressure in mind and when its reduced it produces a fuel curve which makes it run more lean and this effect torque.

Now if this is true would a device like the urd MAF sensor simulator return this fuel curve to normal or adjust for it.

 

Back pressure helps with low end power. NASCAR, F1, ect are running in the higher rpm range. No need for back pressure, less restriction the better to a point.

As far as the URD thing, I'm not sure.

 

Guess what. If you take out your 02 sensor and put on a back pressure tester, if you have back pressure, that's means your exhaust is restricted. That's bad. It'll run like piss, if at all. You don't want any. There's enough restriction built into the factory exhaust.

 

If you have the 2.7 back pressure is probably your friend. I would never throw, say! a 3" exaust on a taco with a 2.7. They paid designers quite a bit of money to come up with this stuff...most of it is good...I would not mess with it.

 

It's not really about back pressure. It's about scavenging. Google it and do some reading. Yes, exhaust pipe diameter, and length will have an effect.

 

I did do some reading and people said that a internal combustion engine does not need back pressure but the designers have to design with back pressure in mind because of mufflers etc. So that's why lack of back pressure causes loss of power because the ecu thinks it needs back pressure because it was designed with it.

 

And what about commercial engines, like none auto mobile engines? If back pressure helps with low end torque then why don't we see cats and mufflers on them?

 

scavenging...

 

I'm wondering, has anyone done dyno testing comparing a stock, more restrictive exhaust to a more free flowing exhaust.

 

There's a post somewhere, I think by chris4x4, that talks through this.

As posted above, it's not really back pressure that's a problem, as back pressure is nothing more than the measure of restriction. The true issue is exhaust gas velocity through the exhaust system. For low-end, small pipes that keep the gases moving and enable scavenging within the exhaust system that help create some torque. For high-end, larger pipes enable exhaust gases to flow freely out of the system quicker.

Designers then, have to design to a happy-medium for low-end and high-end use. Modifiers can tweak their own performance for low or high end by optimizing the pipe sizes for their own needs. Keep in mind the bends, lengths, cats, mufflers, connections, etc. all go into the exhaust system, so all changes can have an affect.

 

if you ran at higher rpms all the time then you do not want back pressure....BUT for everyday driving i.e. stop and go traffic...you would want back pressure. Like said before, you will lose low end torque. If you want to get the both of best worlds, then install an exhaust valve. Closed at a stop light (low end torque) open at highway speed (high end torque)... some if not most industrial engines have mufflers but normally that is for sound reduction...which does cause some back pressure BUT in their applications they stay at a steady speed while in use

 

That makes since. Finally some answers!