4age exhaust secondarys

[Caveman]

Hi everyone

basically i have a smallport 4age motor and I am getting silvertop 4-2 headers for it (in transit). I wana tig up a 2-1 section but Im clueless when it comes to tuning lengths.

Is there a known ratio of area with primarys and secondarys? From what I can gather longer will give good low end power and shorter will bring the power to the top of the rpm band. Problem is I dont know how long 'long' is and how short 'short' is. I'll probably use 1 1/2 pipe for the 2-1 section. what sort of lengths should I be using? If someone could tell me stock length and pipe size that would help

Cheers

I have read this thread which was very useful, but doesnt really answer my question.

http://forums.toyspeed.org.nz/viewtopic.php?t=23885&highlight=exhaust+lengths

[Mr Revhead]

500mm is a good lenght secondaries.
i have seen some forumlas for working it out, if ya maths is up 2 it....
shouldnt be too hard to find on google

[Caveman]

yep my maths should be up to it, however if I can be bothered with the maths is the real problem

thanks revhead

[Stealer Of Souls]

I read that exhaust lengths are the opposite of that...
Shorter length for lower rpm.
Longer for higher rpm.

[HELBND]

jeez dylan - i have a set of blacktop 4-2 section you could have had for 20 bucks, the difference is rather large

[RedMist]

I read that exhaust lengths are the opposite of that...
Shorter length for lower rpm.
Longer for higher rpm.

Depends on how many reflections you are looking for. As you shorten the length you tune for higher RPM, until that is, you shorten enough to loose a reflection and then you're tuning for low RPM again.

[QikStarlie]

the ones i made for mine are pretty long. must be around 700mm i guess. gave plenty of midrange power over the stinky cobys it had on it. while still reving right out nicely
i'l have a measure just how long the are soon