4-2-1? 4-1? Extractors broken down!

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drexchan

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drexchan

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Zeroed has got it exactly right about the size, scavenging effect and what 'back-pressure' is.

---------- Post added at 03:27 PM ---------- 6 hour anti-bump limit - Previous post was at 03:13 PM ----------

PV=RT

P = fluid pressure
V = fluid velocity
R = fluid constant (I guess)
T = fluid temperature
V is volume. This is the Gas Law for for gas thermodynamics, not fluid dynamic.

The correct relation is PV=nRT, with n being number of mol (1 mol = 6.02x10^22 particles).

---------- Post added at 03:36 PM ---------- 6 hour anti-bump limit - Previous post was at 03:27 PM ----------

Therefore I was wondering is it possible to cool down the exhaust temperature? Because due to the formula, high velocity, low temperature exhaust system can create less pressure thus can pull out more exhaust gasses from engine cylinder. Is my assumption correct?
You started with using the wrong formula so.....

Anyway, you don't want to cool it down because that will only increase the density, and denser gas has higher inertia like a heavier pulley is harder to spin. You want to keep it hot.

Then there's a consideration on the piping size too as bigger pipe has larger external surface for heat dissipation. Like what Zeroed has pointed out on how the size affects velocity and scavenging, it affects the temperature (and then the density, then the pumping lost) too.
 
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monsh

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monsh

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well, to my believe, there's a reason the engineer created the pipe path and also size they used for each engine .
probably the best option u have for ur system .
unless u go for performance engine or turbocharge ur engine, then its already a different story.

i think there should be a follow up on this .
probably the effect of s-flow, straight, twin exhaust .

and also the effect of straight pipe, orignal path pipe .

btw, after a few months of research, i think its best to stick to the original route + original pipe size.

probably just change to 4-2-1 header,catcon, mid bullet,back bullet, straight muffler.

well to me, i dont want to compensate the fuel consumption just for power. its not worth the modification then i believe .
 

monsh

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monsh

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yeap, thumbs up for the great article but then again, there's a lot of factor to the performance and its always the "lose some gain some" condition when u play around these things .
 

kumbang

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kumbang

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nice write as always.

Yup, wish theres more explaination on pipe size, bullets, s-flow n etc

can i like mix the pipe size, ex : 1.6 till mid then smaller size?
 

LOPI

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LOPI

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Thanks bro for gud info..you really helping us to understand much better..go through detail..:)
For those who confius this tread really help..
 

Izso

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Izso

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As I've mentioned a few times before, the real sifus are the ones in the background keeping quiet. I'm only sharing what I learnt from them. In this particular case it's Drexchan's extractor post, not mine! :biggrin: so kudos to the silent sifus
 

csl

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csl

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How can the valve over lapping coverage missing in an exhaust related topic?
 

Izso

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Izso

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How can the valve over lapping coverage missing in an exhaust related topic?
Erm.. this is an extractor topic, not exhaust topic. Not quite the same thing? Related but not related. LOL
 

drexchan

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drexchan

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We are assuming the entire head assembly being untouched, with only the extractor replaced, and comparing both common types of extractor for a straight four. This is the most common thing beginners do.

Advanced users will look into optimizing the performance (with the new extractor) by means of cam adjustment, air/fuel ratio and ignition timing. Some will go further with port & polish, valve angle cut, high compression, management, etc.

However, whatever one do to a 4-2-1 can't make it performing like a 4-1, or vice-versa. Therefore the other tuning techniques are not discussed here.
 

D7zul

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D7zul

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After calculating..

the right extractor for me is a bigger 4-2-1 :biggrin:

namely HKS extractor.. any1 here have this for sale??? :burnout:
 

r3dster

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r3dster

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hmm..good read.
but i've been reading around and yet still unable to get a concrete answer to it.
if 4 - 1 provides power at higher rpm and 4-2-1 at lower...
how about...equal lengths and unequal length headers? as such for example; scoobies have performance setup for both equal and unequal lengthed extractors....
dispite the fact uneqal length gives you a much clear growling,but....if aftermarket high performance company makes both of them surely there's a difference in it's output...anyone has a concrete answer to this?

Thanks a bunch
 

Izso

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Izso

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hmm..good read.
but i've been reading around and yet still unable to get a concrete answer to it.
if 4 - 1 provides power at higher rpm and 4-2-1 at lower...
how about...equal lengths and unequal length headers? as such for example; scoobies have performance setup for both equal and unequal lengthed extractors....
dispite the fact uneqal length gives you a much clear growling,but....if aftermarket high performance company makes both of them surely there's a difference in it's output...anyone has a concrete answer to this?

Thanks a bunch
You're getting into specifics and that's more advanced than what Drex has explained. Have a read here and see if it answers your questions :

Custom Extractor

Apparently this guy got inspiration from someone in ZTH! Doesn't really talk about how he did the calculation though but is still a pretty good read.