71 replies to this topic

[Stedz_lc]

That's what we'll do then old johno think goin 1 3/4 into 2in into 3 inch which is actually 2 5/8 into 1 7/8 in 2 7/8 internal sizes c what happens equal length as best we can

[Stedz_lc]

Mmm... Il look into this and lookin At merge collector and other ways to bring them together

[Stedz_lc]

Yea looked at them, does there megaphone style shape after the collector decrease in size then big act as a terminator box the megaphone area being large?

[EunUCh]

Bit odd that Holden grouped 123-456 on their stock manifold ?

 6m.JPG   60.86K   0 downloads

At first glance it may appear that they are 6-1 but note the 'bifurcation" angle of the "groups"

Although not the prettiest high performance bit of gear it sort of seems to adhere to the theory of "short" primary pipes

that basically kill the moving peaks of pressure over rpm range and also would seem to help "extract" to a point from the

the next exhausting stoke of the previous,based on the shape of the "bifurcated" angle short secondary runner?

it just does not have the right size holes for performance applications,but having said that a fella that used to race stockies only

ever used a "modified" piece of shit cast exhaust manifold and still holds the track record?...in a little Torana of course.

  

 

[Stedz_lc]

So back on this primary's are almost done, so the "secondary's" oldjohno you think length will have no effect!?! So I can make them long? Really long? Not sure how i would even fit a box or anything under there!! Think I'm
Stuck with just a two into one collector

[Stedz_lc]

I was looking at this tonight, my three into one collectos are sorter next to the outrigger/sump and I was t hinkin if I ran from there all the way past the
trans crossmember (allowing more clearance) then once pass start my three in system.

As you said dj where can we fit a box or anything with large area on the lc/lj!

And because im blown im thinking this and pulsing may not have as much effect

Cheer

[EunUCh]

Have been thinking about the box and it's function,like oljohnno said it's purpose is to kill off any unwanted return pressure waves.

Since space is limited for the right size box i was just thinking about cats,and how good they make the exhaust sound when they get a hole in them?

 

Just thinking along the lines that cats are very close to where a collector box should/would be?,and given that cats have a honeycomb? construction i was just thinking that any return pressure would have a very hard time finding its way back up the cat once it has passed through the cat therefore acting in a way the same as the box.

Cats are available in some fairly small sizes these days with some decent flow ones available and are round but still have the honeycomb cell structure?

Maybe a high flow cat would do the same job as a box given that it would be a hard task for the waves to return up the cat given the pressure difference and number of cells it has to try and find it's way through back up the cat...it may not work...just a thought?  

Edited by EunUCh, 14 April 2015 - 04:17 PM.

[warrenm]

Use your muffler as the "box", it doesn't have to be an empty box, just some where for the pressure wave to expand into before it turns back on it self. 

[TerrA LX]

Pressure waves, wow, how do you measure them???

Cats are close to the engine so the honeycomb structure get hot, so it works.

[EunUCh]

A good muffler should do the same job to some point even if the capacity is not what it should be given the space consideration,an all stainless one would probably be best.

Pressure waves were generally measured with a "morrison indicator" (as per the pictures posted previously).

Probably the easiest way to give an idea on what happens in there is like 2 people walking into and empty room and talking...echo,echo.echo,this is a return pressure wave as sound is pressure,and in an exhaust is similar,the waves will come back from all over the spectrum and in some cases be beneficial or otherwise,sometimes they will resonate.

 

Now fill that same room with some furniture/curtains etc and the echo gets "absorbed",a bit like a sound proof room that music is recorded in,some mufflers are also called "absorbtion mufflers" because they absorb and kill resonance/harmonics etc....that may be the same idea as a box at the end of the collector?

Yes,cats need to get hot,but think about the structure and what would happen to anything trying to get back up from the down side trying to get back upstream?

Punch a hole through a cat,big difference in noise levels,it is a wonder they let anything through one way when you can barely see daylight through some of them.

 

It has been said before that a "tuned" exhaust will only work over a small area of the rev range,i sort of liken it to tuning in an AM radio with a tuning knob,start tuning to find a station and you will find that if you go slow enough with the tuning when you are close to a station you will hear the station start coming on and then it will peak and as you go past the peak it starts to drop off,from my way way of thinking a "tuned" exhaust will behave the same way?

I would hazard a guess and by all means get the primaries and secondaries sort of reasonable and then just kill everything after the collector.

 

Probably the best example of "extractors" and exhaust box would be a Sprint car....don't hear too much of a note change on those things through the range..good example of a non "tuned" system that works?

Edited by EunUCh, 15 April 2015 - 04:41 PM.

[N/A-PWR]

he he, I had a hot-dog after the hurricane tuned extractors.

was about 900mm long.

[N/A-PWR]

was similar to this Hotdog:-

 

http://www.amazon.co...r/dp/B00029J3JS

and Red it was. 

 

just in case the image disappears, here is an uploaded shot:- 

 

 Hotdog.jpg   16.67K   0 downloads

Edited by NA-PWR, 28 February 2016 - 08:15 PM.

[EunUCh]

^ I see what you mean (i think?) ,make it it behave as "its own" negative pressure wave for that that short period under its own steam with what is left from the inertia of the exhaust charge to pull out (extract) that last bit on overlap to scavenge residual ?