Is it auto car can use 4-1?wat difference wit 4-2-1?

can but i think u will tend to lose out on low end . auto transmission are bad here

hmm this is from team integra http://www.team-integra.net/forum/blogs/mi...ssure-area.html

there r 2 types of 4-1. d usual people say low power on low rpm is d long type,.. there is another type which is short 4-1.. its something like exhaust manifold.. d short 4-1 is extrememly suitable for town drive...but will mati pucuk vry fas... mayb 4krpm.. not sure..

so..bro..if i use 1.5" pipe will i get the same result as 1.6" since they jus diffe 0.1"?
Straight muffler? how abt S-flow muffler?

I have made some observation that ... for a given length .. there are several fitting RPM to achieve the desired pressure wave scavenging effect.

For example for my MYVi (pipe length 45") ...have several resonance between RPM 2000-4500. They are
2000, 2200, 2800, 3300, 3900. Which means, I should be able to feel "power" between RPM 2000-4500 as I jump from one RPM to the other.

Other resonance RPM outside 2-4.5K are 4800 and 6500 .. but those are too far apart (cant expect the RPM to jump from 3900 -> 4800 -> 6500 easily like it does between 2000 -> 3900... LOL) ... this is MyvI only maaa

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Added on October 17, 2011, 3:11 pmIf you feel an extra 10-15 HP is negligible ... then you can ignore pressure wave tuning ...

This post has been edited by luqmanz: Oct 17 2011, 03:11 PM

Change my muffler 3 weeks ago. Compare to previous setup (mod+original muffler), car feel like power lose, what is the problem? But FC still maintain, RM50 300km..

My ride : BLM
Mod: header 4-2-1, midbox, air filter, and spark plug.

300km with 26.31 liter RON 95 ? 11.40 Km/L ... ... is this Auto car ?

Driving manual. Why?

This post has been edited by edison_84: Oct 17 2011, 04:08 PM

u will be surprised with how different the car goes with 0.1" pipe change. increasing pressure in exhaust increases gas velocity in squares i.e. 2 pressure increase = 4 velocity increase, 3 pressure = 9 velocity. so u can imagine how 0.1" change can make lots of difference

if backpressure happens, the velocity will be reduced in same fashion too

i only know straight flow setup bro. have to ask others who have experience with sflow in their setup

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Added on October 17, 2011, 6:54 pmmay i ask what is the muffler spec? and any mod on stock piping?

This post has been edited by upontheriversky: Oct 17 2011, 06:54 PM

piping original. straight muffler.

i agree it is not as significant on stock valvetrain when my engine has only 9 degree overlap and results i have got from testing on my own car is not that impressive but it certainly works and thats enough for me. ive seen impressive result helping others with more aggresive cam with this idea when it was opposed and mocked by most exhaust shops i consulted and that means something to me
What matters is the grab of knowledge and know how to apply, coz to be able to apply it to any cars in future, that is priceless, it can save us a lot of money in future mod with bigger more overlap engines. worthiness of things has different meaning to everyone

also to challenge conventional ideas is what makes the forum fun and make our forum looks more sophisticated hehe



what is the diameter of that muffler?

This post has been edited by upontheriversky: Oct 17 2011, 11:12 PM

piping diameter about 0.2mm bigger than original piping

ok this is tough..mind sharing ur driving experience before and after u mod?

Before change muffler:
Can feel the boost when rpm almost reach 3,000rpm. Normally change gear at 3,000 rpm

After change muffler:
Have to rev higher, 3,000 rpm and above, 3,200 rpm can feel the boost, change gear around 3,200 - 3,500rpm, if below 3,000 rpm, have to press more gas to get the speed. Overall, car feel slow at day time, can feel the power at nite time.

i'm just sharing what i've came across reading. just to hear whats is the opinion here regarding the quote so that i could understand more.

yeap, thank you again for sharing out all these.

we will find out further when we are going for dyno and can explore the result.

hopefully i can do mine soon, but i'm thinking whether should i dyno the based standard output first beforehand.

although still not able to figure out all the calculation and concept, but still i have faith in this type of unconventional tuning.

bro teach me how u derived those resonating rpms from 2k,2.2k to 3.9k and so on..?
wait till u do ur own exhaust, sure u find myvi is capable of revving that high hehehe


ok i can probably say that the muffler actually raised ur powerband from 2.8k to somewhere near 3.2k, reason can be the straight muffler opened up a bigger path so the gas velocity now takes higher rpm to match ur usual driving habit.

but just want to see other factors, what do u have in between the new muffler and the 4-2-1?

did u find more power at higher rpm than before?

apart from colder air at night giving more power, pressure wave tuning will change at night too because of exhaust wave speed is slower at lower temperature so meaning if during day boost is felt at 3500 rpm, at night time the boost might be felt at 3,000 rpm

in general, i believe an engine performs differently between day and night especially when we have 2 extremes of shiny hot days to breezing rainy night coz engine performance overall is largely affected by temperature..exhaust speed, intake air temperature, thermal efficiency etc...

who knows in rainy days where air is dense with moisture, we got free water injection upgrade for a while haha

yes i really want to get my hands on my own dyno chart, even though a lot of theory been covered here but only the dyno will actually tell us how accurate the theory is to the reality.

ey if u got extra budget, i 2nd ur thought to dyno the stock performance, i wanted to do that but my car has been modded when i bought it. Its really useful when it comes to tuning, so we can see what perodua has done for us, we take it from there and do the rest hehehe easier to justify the power increase with all upgrades we are going to do in future

actually i really hope someone who already been practising this method for ages, read this thread and come up with something more shocking, that someone is gonna be godlike haha

This post has been edited by upontheriversky: Oct 18 2011, 02:07 AM

can u share your straight flow full setup ?
u manual or auto??

I'm using the formula ... n*L = (speed of sound) * (degree difference btween Exh open and Intake Open) / 6 / RPM

n = 2,4,6,8,10,12,14

L = chosen length ...


When we change the n .. we get different RPM ...

n = 2 means one-round-trip (from manifold -> collector -> manifold)
n=4 means 2-round-trip

etc...

Example ...

L = 1.143 meter (45 inch) ...

and RPM = 3700 ... n = 8 ... the pressure wave made 4 round-trips before arriving at the the manifold during intake open.

This post has been edited by luqmanz: Oct 18 2011, 11:58 AM

Change to aftermarket midbox between new muffler and 4-2-1, pipe diameter also around 0.2mm bigger than original exhaust pipe.
Yup, more power at higher rpm and easier to rev up to 5k-6k rpm.
Can I add bullet after midbox? My friend complain exhaust sound too loud, she don't like it.