oldman

thanks Miller, and just about everyone else,

um Tamago

The Don I agree Oldman

jmiller20874

So basically you agree with everything I just said.

Tamago

poor old man.. you know i'm right.

sithscripter

It wasn't explicitly stated that 18psi was measured at the muffler ... I'd imagine that could have been measured anywhere downstream of the collector. 18psi overpressure x 3.14 x (2.5/2) ^2 = 88.3 lbf.

And a lot of the discussion here seems to center around principles that apply for (purely theoretical) incompressible fluids at rest in thermal equillibrium ... sure, it's easy to predict the behavior of an ideal situation at rest with Discovery Kids-level science, but hot, compressible exhaust gases in motion are another matter entirely. Maybe I should just STFU and leave it to "real" engineers. ;-)

Scott17

Tamago, you should have paid more attention in school! It is not 18PSI X Volume = force it is SURFACE AREA X PRESSURE. Would you believe that 9PSI would crack the wing of a 747? You bet! surface area X pressure. But basicly the moral of the story is that while some people think HP gains are cumulative of brochure numbers added at will, reality dictates that there was not a lot of "free" HP left on the table when Toyota designed the powertrain of our cars and you would be hard pressed to make any significant gains cheaply.

Tamago

[quote="jmiller20874"][quote="Tamago"]read what you wrote backpressure.

it is possible to have 18psi of backpressure..

let's say my 2.4L compressor makes 430 CFM..

and i allow 120CFM to escape through my 25FT exhaust with a 1" diameter.... (which, btw would create a 1/4PSI pressure drop

what would be the pressure at the HEAD of the exhaust line..

ZERO?

no.. the compressor is filling the "tank" faster than i can get rid of it.. i will not push 430 cfm through the 1" tube without a rise in pressure, because line velocity and friction will dictate so.

ok, here's an easy one for you..

go to your water hose.. turn it on, and watch the flow come out of the hose.. it goes maybe 3 ft right? what is the pressure inside the water hose AT THE FAUCET?

now.. put your thumb over the end of the hose, and allow only a small portion of water to come out..

it goes a LONG way!!!

what is the pressure inside the hose AT THE FAUCET NOW?

higher, right? this is how you can create backpressure in an exhaust system. (and i'll bet that Magnaflow used some V8 from the 80's with two dinky 1/1-2" exhaust pipes and huge restrictive mufflers to get their 18 PSI, which IS a pretty high number)

although the theory is about water, it does apply to air as well, minus factoring in the compressibility of air....

oldman

Scott: true dat, amen brother.

jmiller20874

Dude, you know where you can put that hose. I was making an arguement in your favor in case you didn't realize it. I know pressure is highest at the faucet, my god man what the hell do you take me for? Of course I know 18psi is possible at the manifold.....ah fu@# it, I give up.

Tamago

Scott, you really should have paid attention when reading my responses. i never once said that FORCE = pressure X VOLUME. in fact, i said the exact opposite. i was trying to figure out how oldman thinks there are tons of pressure pushing out on the walls of a muffler.

force = surface area X pressure.. let's play with that..

if i take a ball with an inside surface area of 100 sq inches, and pressurize it to 10 psi, am i creating 1000 POUNDS of force? no! i am not!

Tamago

you just got done saying that 18PSI backpressure is not possible.. now you agree with me?

cool

jmiller20874

I meant at the muffler, damn, blow it out your exhaust :D.

Tamago

the muffler is too close to the atmosphere to ever see 18PSI .. but we all know that, and we should realize that's not what magnaflow was trying to say.

engifineer

Actually, yes you are... it is distributed over the surface. the overall force does equal that... but since we have a little thing called equilibrium, nothing bad happens. Simple physics.

hahaitzskippy

thats wat jmiller said,

Scott17

YOU should have paid more attention to the last sentance of my post! Now go sit in the corner till I say you can come out! Go buy yourself a bushel of magnaflow mufflers and give them out as Christmas presents for all I care, but you still won't have a race car . PS- save the money from one of those muffler purchases and buy a good physics book!

niguels

Gentlemen, you all, please calm down. The situation is getting out of control and the thread is getting away from its initial purpose.

The goal here, IMO is to put pieces of information together so that way everybody can find a benefit from colective knowledge.

Then, once people is educated, it is possible to perform a critic reasoning in order to tell what is the truth, what are convenient half truths and what are lies.

When I write for this thread my intention is not to tell the people not to buy a certain brand. What I try to do is to give others arguments that can help them to make an informed decision.

Please, for everybody that is going to keep posting to this thread, bring information that sheds light over the main issue of the thread. If anybody has actual data, INDEPENDENT NUMBERS OR GRAPHICS, please share it with us.

If somebody has a relative or friend that is actually working in an engineering position for any car manufacturer, please invite him/her to share what they know with us and know the truth "from the horse's mouth"

Thanks for reading

niguels

Did you read my post titled "BACKPRESSURE-Final Words"

https://www.scionlife.com/forums/viewtopic.php?t=47877

Read it and tell me now who do you think knows more about cars design, the TOYOTA ENGINEERS or the HALF TRUTH TELLERS AT MAGNAFLOW.

DouBLeJ16

mygod people, did this turn into math class?

i almost forgot what the topic of this thread was.

jmiller20874

And the point of digging up this thread was???

bB_Local_Boy

so that I could bump it a year and a half later.