exhaust too loud?

[Quinton Exler]

Turbo especially likes a single back pressure according to my calculations. The proper diameter-length tube and obstruction are needed. Once you have created said obstruction and have your interior cubic pipe space calculated you can begin to calculate the back and front pressure the engine will create. Traditionally back and front pressure will cancel itself and create -HP this is why everyone just skips the mass amount of calculations and slaps a straight pipe on! It is the easiest way with no math or major effort. However it still cancel back and front waves slightly, Ideally you want the waves of pressure to meet and travel together with no cancellation (back wave travels slower than front wave) therefor a flawless amount of back pressure is needed to match the waves and will cancel horribly if not done right. This is one example of a proper Borla exhaust, They implement great sizing and tunneling in general however not perfect for every car... My friend actually races his wrx STI on mud track and previously had a full 3" straight pipe, adding a Borla added obstructions however oddly gained him 15+whp? because he had came closer to that perfect pressure match!

 

[Eric Smit]

can you cite any sources?


-Eric Smit

 

[Quinton Exler]

Just math, if you know how to apply pressures to push one another rather than cancel; it will create flow. Many people do not think this way and they will continually think a straight pipe is optimal... This is not true, even a 5" straight pipe is not optimal. No pipe at all however could be optimal because no cancellation could occur during travel through the pipe. The perfect amount of pressure is needed throughout.

 

[rdss]

Just math, if you know how to apply pressures to push one another rather than cancel; it will create flow. Many people do not think this way and they will continually think a straight pipe is optimal... This is not true, even a 5" straight pipe is not optimal. No pipe at all however could be optimal because no cancellation could occur during travel through the pipe. The perfect amount of pressure is needed throughout.

That's not a source, just an opinion...

 

[Quinton Exler]

That's not a source, just an opinion...

Agreed, I have no source with my own current experimental exhaust. The only Source I'm sure I could find is why Borla produces more HP gains than straight. There is a LOT of math behind this... I absolutely had help calculating this crazy ideal for an exhaust, My friend, 8 years college for NASA rocket science has assisted me.

 

[sx sonic]

I will work on citing sources why back pressure is irelevant. Basically when the exhaust hits the exit (ambient temps and change in pressure front) a negative pressure is created that travels back towards the combustion chamber. If timed properly that - pressure wave can help scavenge the cylinder of spent gases out of the combustion chamber allowing more fresh air and fuel to enter for more power.

The timing of this wave and its amplitude (ie. Which part of the powerband it works) is controlled by header design, pipe dia., total pipe length, muffler, and a few other variables.

The style of muffler can effectively determine total exhaust length, this is why several major muffler power comparisons are flawed. The magazine testers coupled an exhuast with a certain "optimum exhaust length" and then tried different mufflers on a dyno to see which made more power. This only works on chambered vs chambered style mufflers or turbo vs turbo mufflers (glass packs). One effectively equals the end of an exhaust as the pressure wave enters (chambered muffler) while the other acts like a straight pcs of pipe.

Obstructions do not add power by themselves and are never good, but they can change total exhaust. Tuning and by "accident" increase power. More power could actually be made without them if more careful tuning was done.

Again turbo cars exhaust wave tuning doesn't really work after thhe turbo. The turbine breaks up the exhaust pulses going out, and they would be even less effective comeing back.

Check out headerdesigns.com , it does not prove my point but you can play around with different factors and see how it affects optimal header sizing.. the same engine will have a fairly different haeader if you want a wide power band vs a pipey powerband or high or low end power

 

[rdss]

Agreed, I have no source with my own current experimental exhaust. The only Source I'm sure I could find is why Borla produces more HP gains than straight. There is a LOT of math behind this... I absolutely had help calculating this crazy ideal for an exhaust, My friend, 8 years college for NASA rocket science has assisted me.

Fair enough.

sx sonic, informative wall of text!lol

 

[sx sonic]

Btw that's not a rant haha and sorry for the wall post just trying to share some generalized advanced knowledge.

Its way cool what your setting up

 

[Quinton Exler]

Thank you Sx sonic, but you must consider the idea! Which I must admit has done fantastic for me so far and I truly feel a gain from it. a really nice gain at that. Back pressure is generally a horrible thing unless used properly! Consider this, Pressure itself creates the exhaust flow, if somebody has a straight pipe it would be far better than stock pipe however would have cancellation bouncing down the entire pipe! Granted one may tune the said straight pipe (according to my calculations 2 feet from the downpipe would be optimal at 3.5") and that's for 0 cancellation and maximum performance.

 

[rdss]

Btw that's not a rant haha and sorry for the wall post just trying to share some generalized advanced knowledge.

Its way cool what your setting up

No problem, we are all here to share opinions and information.

 

[Eric Smit]

You shouldn't feel a gain. The stock ECM tunes down the engine to provide you with a consistent driving experience, which nullifies any mod you do without an aftermarket tune.

because informative.


-Eric Smit

 

[Quinton Exler]

You shouldn't feel a gain. The stock ECM tunes down the engine to provide you with a consistent driving experience, which nullifies any mod you do without an aftermarket tune.

because informative.


-Eric Smit

Got a tune.

 

[rdss]

Does Eric have a tune?!lol He is a Trifecta reseller and one of the first to have a tuned Sonic..... Because... Informative!lol

 

[Quinton Exler]

Does Eric have a tune?!lol He is a Trifecta reseller and one of the first to have a tuned Sonic..... Because... Informative!lol

Nooo, I recently got tuned.

 

[Eric Smit]

Oh, my mistake then. Carry on.


-Eric Smit

 

[rdss]

Gotcha. On the same page now.

 

[Quinton Exler]

Objections against this?

JEGS Performance Products 30930 JEGS Polished Stainless Exhaust Tips

If you find better post it! I want 5" outlets please.

 

[Eric Smit]

good god.


-Eric Smit

 

[$ub$onic]

U need that Eric

 

[Eric Smit]

I just came.


-Eric Smit