[AlanHo]

You guys down under with diesel i30's are so lucky.

You are able to buy the Australian JETPIA exhaust device that will transform the economy and performance of your car.

You just put your hand deep in your pocket to buy this wonder invention - fasten it to the end of your exhaust pipe - and enjoy fantastic, awesome, fabulous and mind-boggling fuel savings etc.

Don't hesitate - rush to buy one now - before stocks run-out.

http://jetpia.goodtechnologies.com.au/what-is-jetpia/

I would make clear that I am in no way affiliated with JETPIA, neither am I a gullible user of this unbelievable device which sucks (on your exhaust).

[Surferdude]

^^
This Alanho character is obviously a troll. Maybe we should ban him.

[Phil №❶]

[Doggie 1]

Anything that wants to suck on my exhaust has to be a good thing IMO.

[The Gonz]

 

[rustynutz]

Anything that wants to suck on my exhaust has to be a good thing IMO.

You want one of those rammed up your clacker? 

[The Gonz]

Anything that wants to suck on my exhaust has to be a good thing IMO.

You want one of those rammed up your clacker? 

Looking closely at the technology, I would guess one of these up your clacker would have you singing like a choirboy! 

[Phil №❶]

In all seriousness, would someone like to define what back pressure is, relative to exhaust systems.

[The Gonz]

My oversimplistic view of the whole tuned exhaust philosophy is that given a finite length of pipe, there will always be some flow restriction and therefore some back pressure. To allow your engine to experience minimal back pressure, the length can be tuned to make the reflected pressure waves (they travel the length of your exhaust system) coincide with the exhaust ports of your engine so that that they appear pressureless at just the right exhaust point in the stroke sequence.

I could go on but I don't want to put anyone to sleep.

[rustynutz]

I am feeling exhausted.... 

[Phil №❶]

Thanks Gonz, I thought restrictions from mufflers, converters, dpf's etc would be the contributors to back pressure, however let's consider this.

Airflow through the exhaust on our Diesels is already compressed before combustion, therefore after being heated severely and considerably expanded the pressure inside the exhaust pipe will always be significantly positive. We can't eliminate the devices fitted to the exhaust so that will always remain as back pressure to an extent, so after travelling through the devices, we're left with exhaust gas that is being cooled by outside air and sometimes water, cooling the exhaust pipe and also contracting the gasses inside, very similar to a chimney. The effect of chimneys is to encourage "draw" and this principle should exist in cars too. To get venturi activity you have to restrict airflow into a smaller chamber, isn't that an increase in back pressure, not a reduction.

Are we asleep yet 

[The Gonz]

Release the sleep fog!

I consider the thermal effect of draw to be minimal for the amount of pressure generated. Since we cannot eliminate the pressure, the complex profile of flow restriction created by all the elements you listed, including bends and surface imperfections, amounts to an equivalent set of lengths that might well be represented as a tree or herringbone, with each branch representing each restricting element.

Another way to picture it is as a corridor with the width slightly reduced for each restriction along the way since each will represent a different resulting reflection back at the source. This is more about travelling waves and harmonics (at different rpm, just to complicate things!) than it is about simple thermodynamics.

[Phil №❶]

Er, does that mean I'm wrong   

[The Gonz]

  Not necessarily, but the chimney analogy is dominant only for very slow moving fluids. Think 'tuned exhaust' as in musically tuned and you might make more sense of it, and while you're thinking music, playing in time means you won't get smacked in the face by the drummer (OK, I might have lost you with that one ).

[Just Rick]

Looks like hocus pocus to me

[Phil №❶]

Not necessarily, but the chimney analogy is dominant only for very slow moving fluids. Think 'tuned exhaust' as in musically tuned and you might make more sense of it, and while you're thinking music, playing in time means you won't get smacked in the face by the drummer (OK, I might have lost you with that one ).

[The Gonz]

Not necessarily, but the chimney analogy is dominant only for very slow moving fluids. Think 'tuned exhaust' as in musically tuned and you might make more sense of it, and while you're thinking music, playing in time means you won't get smacked in the face by the drummer (OK, I might have lost you with that one ).

There's an electrical equivalent to this used for tuning antennas. If your antenna is not the right length compared to the wavelength (think rpm) of your radio transmission, you'll get wasted energy in partial reflection along the length of your antenna dipole and antenna cable for that matter. So antennas are tuned the same way exhaust systems can be, and both can experience 'standing waves' when incident and reflected waves accumulate at points along the length. Clear as mud now? 

[Phil №❶]

What's that got to do with getting smacked in the face by the drummer, have I gone off on a rude tangent in my mind. 

[The Gonz]

Sit in a bathtub and make waves with your hands. When they come back off the other end, they resist your hand motion, but you can tune (time) your hand motion to coincide with the wave action and build on it. You're now in tune with the resonance of the bathtub. You can now make bigger waves with very little extra effort.
Congratulations Mr Exhaust, the drummer isn't smacking you with a wet fish anymore. 

Now if your drummer engine wants to move its hands faster, you'll need a slightly longer or shorter bathtub (exhaust pipe length).

[Phil №❶]

 Simple analogies for simple minds 

[AlanHo]

I went to considerable trouble to find this awesome device for you guys and you pay me back by insinuating I am a troll, express delight at the thought of having your exhaust sucked and try to mock the idea with stories of bunged up clackers, reflecting pressure waves and hot chimneys.

Why not accept the fact that it was designed and patented by Korean Experts and is proven technology - so do as I suggested and rush out and buy one.  You can then come back here and report on the huge benefits you now enjoy in terms of engine performance and economy.

Just think - you could have a chip on your engine, a go-faster stripe on the car, blue lights in your wheel arches, his and her names at the top of the screen, fluffy dice hanging from the mirror and now - to cap it all - a sucker on your exhaust.  You could break the speed of sound with such a combination.

[Phil №❶]

Bl***y h**l, he leaves the forum for a few days and looses his sense of humour totally. What's wrong Alan, your mob  won the 1st test







 

[The Gonz]

Some unkind souls might suggest he's upset at not grasping the bathtub analogy, being a Pom and all, but I never would. 

[Phil №❶]

 

[The Gonz]

Was that a bit much? All in jest, of course.

[AlanHo]

Some unkind souls might suggest he's upset at not grasping the bathtub analogy, being a Pom and all, but I never would. 

I was quite willing to have a go in the bathtub - but there is a plumber in the house doing work on the heating system and the boiler is off. I doubt that with a cold water shrunken clacker I would have the energy to make waves.

I must go - I am in the middle of a search for the next awesome Aussie automotive invention to advise you about.

So watch this space.

[The Gonz]

Looking forward to it, Alan.

[Lakes]

snake oil, hey Phil back pressure is when your sitting on a cushion & try to fa..t 
cheers

[Phil №❶]