unequal length japspeed 4 branch = loss of flat 4 burble?

[scottishtaffy]

after putting a new 4 branch stainless manifold on last year ive lost
the classic burble. i have a straight cut 3in stainless one pice exhust
and change it fo. r a two piece with the front bullit in line silencer
on but tho it made it quieter i seem to have lost a bit of power like
its strangling it a bit but still no burble. has anyone come across this
when fitting 4 branch manifolds? below is a pic of the manifold .



i
miss the burble but am also wondering if when i get it mapped it might
make a difference as the ecu will be matched to the flow. it was a
standard manifold on before.

[Jay762]

mapping may improve the power  - strange you have lost the burble with unequal length headers though??

[scottishtaffy]

i have a straight rhu decat stainless exhaust with just a rear silencer but that was on with the standard header just since ive put on the stainless 4 branch.  it still got a slight burble but more tinny now then the deep rumble. maybe heat wrap the front ? to muffle the tinny sound?

[savage bulldogs]

They look like equal length bud ;-)

Which would make you loose the burble ,as burble is caused by the exhaust gasses hitting one another in the unequal headers not by the boxer flat four engine itself.

I know someone with a newage jdm sti (which has equal length headers as standard) which doesn't burble either

[scottishtaffy]

i bought them new as unequal lenght. if you type in eBay 'unequal lenght headers subaru you will see them. the o/s pipes are slightly shorter but speaking to a friend of mine he said i have no more gain with the 4 branch as i would a standard set with good up pipe . 4 branch comes into its own when going 400 plus brake. where as im looking at 350 ish

[Gambit]

Is strange any unequal should still give the burble. So to get it back I'm guess would need to change it again. :( 

[savage bulldogs]

Yeah I've been having a look at Google images and they do look like aftermarket un equals .

The reason I thought they weren't was because of the extra scroll on the turbo side which o.e headers dont have .

Mabey their just close enough to being equal to loose a bit of burble ?

Ie turbo side is that bit longer than oe but not enough to be equal

Get your old oe ones ported and sell those mabey

[Gambit]

Mabey their just close enough to being equal to loose a bit of burble ?

Ie turbo side is that bit longer than oe but not enough to be equal

That's what I was thinking 

[Ash007ks]

I found this as well when fitting the headers, and I put it down to heat wrap, when I finally got them heat wrapped it was a lot better, ive heard multiple reasons why, also check the welds on the insides as one of the holes may be obstructed more and lastly the !Removed! join, I found mine to be blowing more than a £5 who**

[scottishtaffy]

i think if im going to take it off to wrap it them i will just put on the oe one as no extra gain with the 4 branch anyway.. also by putting back on th oe one i might regain some of the lost spool and increase it to spool quicker

[savage bulldogs]

I'll eventually need aftermarket headers but for now i bought a haywood  & scott  slip jointed upipe  and ported the oe headers to match the new gaskets  ;)  

I increased the bore quite a bit heres a pic of a before and after porting

[Gambit]

Yep made that a little bigger :D 

[Jay762]

i think if im going to take it off to wrap it them i will just put on the oe one as no extra gain with the 4 branch anyway.. also by putting back on th oe one i might regain some of the lost spool and increase it to spool quicker

 

bearing in mind its the whole end to end system and it depends what you want performance wise - bolt on some extra dimension / flow tubing in one link of the chain it will have an impact on overall performance.

 

Sounds like you could go one of two ways, revert and be happy with existing or stick with and start looking at fine tuning everything else in line with the change you have made

[scottishtaffy]

thing is jay that the japspeed headers are a one piece item so cant just change the up pipe and the exhaust is also a one pice straight thru from the down pipe straight out to the back.. im not looking for big powere gains. from the fromt set up, 350 is my goal, so standard headers would probably be ok

[Gambit]

I was running standard headers with the same power gain's you want and had no problems. 

[Jay762]

yup does sound like the standard headers will do the job you want just fine