unequal length runner exh mani

Enuo said:
What about 4 unequal length stack exhausts poking out the bonnet?
Click to expand...
i,ve finished testing the spare engines, and have left 1 in the red car to test different pipe designs andy,
as far as i can work out, i need to join cyls 1 and 2, then make that secondary a lot longer than the cyls 3 and 4 secondary, so as to get the desired chuff-chuff..................chuff-chuff
i think its gonna be trial and error tbh :)
 
Enuo said:
why not join 1 -3 and 2-4?
Edit: or is that how the normal tubular ones are?
Click to expand...
aye thats how 4-2-1,s are usually designed eh, so that you get chuff....chuff....chuff....chuff
equal length 1-2 and 3-4 should give a very slight burble
 
Sounds silly, but would a really short exhaust do it?
I only say this coz I only have a 2 1/2 foot exhaust from turbo (2.5 inch) because I havnt finished it yet lol

But that burbles and pops real nice

Maybe complete bollocks, still sounds badass
 
pork said:
Sounds silly, but would a really short exhaust do it?
I only say this coz I only have a 2 1/2 foot exhaust from turbo (2.5 inch) because I havnt finished it yet lol

But that burbles and pops real nice

Maybe complete bollocks, still sounds badass
Click to expand...
just very loud i think neil :D i,ll post some vid,s up next week
 
frank said:
just very loud i think neil :D i,ll post some vid,s up next week
Click to expand...
Is on throttle, but idle and low revs, and lift of throttle, it sounds good.
I'm thinking somthing to do with sound waves dispersing/separating quicker out of the exhaust instead of being bunched together on a long pipe

Just my 2 cents
 
what is the difference in length? about a foot?
$(KGrHqN,!jUFE31cf,()BSW,ipDR,!~~60_58.JPG
 
I look forward to seeing how you get on, it'll certainly be a distinctive sounding Micra and something very different, most in the know will be thinking you've got a Subaru engine in your Micra :cool:
 
1275 said:
I look forward to seeing how you get on, it'll certainly be a distinctive sounding Micra and something very different, most in the know will be thinking you've got a Subaru engine in your Micra :cool:
Click to expand...
yes the side exit it exactly how i want it, pretty quiet but close to the driverside window, all it needs now is a bit of a burble :)
 
i sa wear at the birmy meet you white car sounded exactly scooburude at low medium revs when ye pulled of and out
 
1275 said:
I look forward to seeing how you get on, it'll certainly be a distinctive sounding Micra and something very different, most in the know will be thinking you've got a Subaru engine in your Micra :cool:
Click to expand...
Just like Nissanubaru which does have a boxer engine under the bonnet ;)

The signature subaru sound comes from the design of the engine. Even with equal length runners in the rally cars they still sound very distinctive. Good luck Frank I'm intrigued :)
 
frank said:
in what way andy ?
Click to expand...
Couldn't possibly answer. They're still a 4 stroke cylinder engine just banked... so I'm assuming that something in that particular configuration is what causes that noise. As the subaru flat 6 doesn't sound the same despite unequal length headers
As the pulses all mix together regardless
 
h701micra said:
Couldn't possibly answer. They're still a 4 stroke cylinder engine just banked... so I'm assuming that something in that particular configuration is what causes that noise. As the subaru flat 6 doesn't sound the same despite unequal length headers
As the pulses all mix together regardless
Click to expand...
some argue that its because one bank fires both cylinders, then the other bank fires both eh, but they are still equally spaced on a flatplane crank tho.
i,ll be testing different lengths of that pipe tomorrow, and i,ll see what it sounds like :)
 
tuned exhaust eh frank :cool:

what if you could build a temporary flexible variable tubing system out of narrow metal ducting stuff? so you could fine tune in realtime the actual header tubing length before they bunch up with the rest of the other ports.
once tuned, measure the tubing lengths and reproduce in solid tubes?

running on 3 also makes it sound kinda like a scooby too:p
 
frank I was just thinking abit bout it and thought maybe build 3 of the 4 headers like a trombone slider to vary the individual travel lengths (the 4th header is a fixed length) before they all join at the collector bit?

zbh.gif
 
ooh and just reading bout tuned exh, in theory a realtime variable geometry exhaust (coupled with realtime variable cam timing, dyno remap and maybe variable inlet pipes) could broaden the torque range?
may sound like mad but could be acheivable project, just right up ur street doctor frank :D
 
i think the v8/scooby burble occurs when you get pairs of cylinders firing together paul (like the big-bang motogp bikes were in the 90,s)
so cyl,s 1 and 2 fire close together, and the extended pipe on 3 and 4 should exit the pulses at the same time as 1 and 2 (and create a burble hopefully :))
 
pollyp said:
ooh and just reading bout tuned exh, in theory a realtime variable geometry exhaust (coupled with realtime variable cam timing, dyno remap and maybe variable inlet pipes) could broaden the torque range?
may sound like mad but could be acheivable project, just right up ur street doctor frank :D
Click to expand...
i dont really need tuned inlets with forced induction surely paul ? and i doubt if this unequal exhaust setup will give any power gains, it,ll probably pulse the turbo at low rpm
 
I look forward to the results I genuinely do :)

I put it down to the fact every engine has a unique exhaust and the subaru is just like any other.

Whether you achieve that boxer burble or nor I'm sure you'll learn from it

@pollyp the variable exhaust you speak with use with vct. You can use closed cut and open cut exhaust to vary flow
 
How about have cyls 1-2 and 3-4 join, but keep those 2 seperate all way to back, and have a twin exit?
 
frank said:
i dont really need tuned inlets with forced induction surely paul ? and i doubt if this unequal exhaust setup will give any power gains, it,ll probably pulse the turbo at low rpm
Click to expand...

I never said if its for forced or na, I only speak it as a theory.
and whether it increases/decreases performance or noise level/quality is prob dependant on how each variable exhaust length mix together
 
Enuo said:
How about have cyls 1-2 and 3-4 join, but keep those 2 seperate all way to back, and have a twin exit?
Click to expand...
it would still sound like an inline 4 tho andy (unless you had unequal twin pipes, or held your head between the 2 tailpipes :) )
i think i need to get 1 and 4 to exit together, shortly followed by 2 and 3 together, then a silent gap ( of 360 deg)
 
Almost Neil but you 1 flowing to 2 and 4 flowing to 3 they'll cancel each other out

1 & 2 should be longer than 3 & 4 to create the burble
 
That's the whle idea is it not Frank? Get cyls 1&2 to pulse together with 3&4 together will give the impression of firing on 2 no?
 
h701micra said:
That's the whle idea is it not Frank? Get cyls 1&2 to pulse together with 3&4 together will give the impression of firing on 2 no?
Click to expand...
i think it needs to be slightly off phase andy, else it will sound like a 2CV ! (1..3......4..2...........................1..3.....4..2....................)
 
frank said:
i think it needs to be slightly off phase andy, else it will sound like a 2CV ! (1..3......4..2...........................1..3.....4..2....................)
Click to expand...
That'd be what I'd go for :)
Looking at my impreza manifold and the firing order it does look to hit the hit up-pipe in a very similar manner :)
 
im confused... firing order is 1342
you want 1&3 to pulse together, so you make 1 longer so that the delay in 1 syncs it with 3.
and you want 4&2 to pulse together so you need to make 4 longer to sync with 2?
but you have made 1&2 longer?
as for length difference, could you not just use firing frequency and the speed of sound? i.e. @1000RPM I make it 0.03 seconds between 1&3 firing... speed of sound is about 340m/s so the length of tube you would need is 0.03x340=10.2meters (plus the length of cylinder 3 runner).
 
pollyp said:
ooh and just reading bout tuned exh, in theory a realtime variable geometry exhaust (coupled with realtime variable cam timing, dyno remap and maybe variable inlet pipes) could broaden the torque range?
may sound like mad but could be acheivable project, just right up ur street doctor frank :D
Click to expand...

yeah it'd definitely help! you need them adustable on a cam which turns to max lift based on revs. match it with a similar system on the intake and you're onto a winner. Aprillia do it on their 1000cc superbikes, and claim a 10bhp loss throughout the revs without it. they extend by up to 50mm.
 
you,re just shifting 2 cylinders aint you ed, so that they enter the collector with a delay, so that the 4 powerstrokes are close together (then a silent gap)
here,s a longer pipe test (which suits me because the current pipe is too small for the finished mani)

 

Similar threads

Finto_GX
What length velocity stacks?
Replies
3
Views
827
Finto_GX
Finto_GX
pork
Variable length inlet runners
Replies
34
Views
3K
pork
pork
Skinner_87
Inlet track length / trumpet length
Replies
2
Views
738
h701micra
h701micra
S
UEL manifold
Replies
2
Views
783
Steve27
S
Revmau5
CG10DE Thottle Bodies (Trumpet Length?)
Replies
33
Views
4K
tomwest
tomwest
Back
Top