jst the other day for fun, i was driving my NHC. i took out the airfilter n drove around the garden.

when i revved up i can hear the "vtec" kick in yo!! LOL. i didnt pay attention on which RPM

after tat jst put back the air filter back in haha.. felt a real different with n without the air filter

your house garden that big ar?
can drive around ?

aiyo, around my housing area la.

please take some time to read about this

1. exhaust termination box - how to design a street compliant exhaust system that runs like tuned racing open header - by David Vizard

http://www.popularhotrodding.com/enginemas...exh/index1.html

summary:
- termination box should have minimum twice volume of engine displacement, but this strictly apply to WOT application. in practical 1.5 times engine displacement is sufficient for part throttle, city driving application
- this does not apply to sflow setup, only straight flow.
- since we dont have open chamber muffler here, fit the biggest straight bullet at the end of collector so it also acts like open atmosphere

to confirm that straight bullet can be used as exhaust termination box, this is my discussion in speedtalk.com forum:

http://speedtalk.com/forum/viewtopic.php?f=1&t=27535

this is why some enthusiast found that fitting a bullet gives better power overall than having straight pipe till the end and thought this is due to backpressure but its not, the bullet actually acts as exhaust termination box and make ur exhaust system seems shorter like those in open header and collector racing setup which contribute to the power gain

2. equal length header is not critical compared to secondary/collector length when it comes to header design, in practical it is more like polishing the port for bling factor so customer would think they are in the right step of buying high quality product and buying iridium spark plug supposedly for increased horsepower

http://www.sandersonheaders.com/Lets-Get-Technical.html

to summarize:
- these are the sequence of importance when it comes to exhaust tuning:
a) collector / downpipe length (until first bullet/resonator)
b) colector / downpipe diameter
c) header primary length
d) header primary diameter

this summary above is based on David Vizard's tuning 4 stroke book, google him up, he's a big shot in car tuning in the U.S. so in contrary, dont spend too much time on header because collector length is more sensitive to powerband curve than header itself

general rule for collector length:

18" - 24" for higher rev range (6k-7k peak), longer 30" - 40" for lower rev range (3k-4k peak) and if u wish to tune it further down slight higher than stock exhaust, use as long as 50"

a video of different collector length dyno test:

http://www.youtube.com/watch?v=1ywUEz5XtdE

if you are really into exhaust and intake tuning, pay ~rm200 for this PipeMax software and 90% chance says u will get the optimum result in real life. this should be worth for exhaust businesses. the software takes into account ur valve lift, intake port size, valve diameter etc so it is very specific and pretty accurate

it can also be used to calculate intake side

http://maxracesoftware.com/pipemax36xp2.htm

just to share some proven very useful info in exhaust tuning, especially for NA, i dont think this technique is applied anywhere in most exhaust shops here, most of us have only this in mind when modding exhaust system " how much and how fast the exhaust/ muffler/ pipe can flow".

nowadays, when u ask how to modify exhaust, u get typical answer like " manual use straight flow, auto use s-flow", "pickup use 4-1, top speed use 4-2-1". honestly, i think even auto can use straight flow which is better and get faster than stock pickup, achieve top speed easier than stock and the car is snappy. just swap to a smaller pipe and put straight flow in, definitely better than using large pipe than fit in 3 bullets to restrict it, waste of money on large pipe and the 3 bullets

fact is, the most important factor contributing to highest gain in exhaust system is " pressure wave tuning ", go to ur local exhaust shop and ask them this, im sure most of them will say its not related or dont have any idea. ive searched through all local auto forums, not one ever open this discussion so lets start now coz in exhaust modding scene in the states, they put extra effort on pressure wave tuning rather than having the highest flow coz its quite easy to figure out which is "when in doubt, always use smaller pipe size".

a quote that i really like in exhaust tuning:



there is more to this, search them up for more detailed info like determining collector length before terminate to resonator for ur engine. im just here to open some new perspective in exhaust tuning

guns for show, knife for pro, turbo for show, NA for pro

This post has been edited by upontheriversky: Jul 26 2011, 03:09 AM

can i know that wat is the different between spiral bullet and straight bullet?

compare between that two....
neither 1 spiral bullet will cause better performance and FC..
Or 2 Straight bullet will cause better performance and FC..???

Btw, in alot of videos I saw, MIVEC/VTEC when activated the RPM needle seems to jump and raise much faster...

of coz maa... that is what makes it special...

n the sound when it activates!!! PPPRAAAANNNNNGGGGGGGGGG

recently my setup for bullet and midbox,the distance between bullet and midbox is around 4inch..if i change the distance to 12inch,is it will affect the power?

This post has been edited by samwongjyhhorng: Aug 10 2011, 09:58 PM

search swirl bullet in this forum, u will find answer for spiral bullet there, same goes for straight bullet

straight bullet more performance than spiral for sure, FC depends on exhaust setup. if its custom to ur rpm habit then FC is lower, if it is set out of ur rpm habit then FC can be high

1 bullet is the best, 2 bullets just add up backpressure, if some people tell u to use 2 bullets for power, that means ur pipe is too big for ur engine or ur application. in that case, swap smaller pipe and remain 1 bullet, that is way better, no flow restriction, just faster flow velocity


12inch is better than 4 inch i suppose cause u have longer pipe length after bullet to build up exhaust velocity and aid scavenge out gas from the bullet before the gas enter ur midbox

why using bullet and midbox? for noise reduction or power improvement?

here is setup for race performance exhaust with street muffled system:


the resonator box (bullet) separates ur header and collector from the rest of exhaust system so header and collector length are kept tuned.

This post has been edited by upontheriversky: Sep 24 2011, 11:44 AM

midbox to reduce the noise lo..previously use 2 bullet,sound very noisy..so tat means after change to 12inch,then can gain more pick up and top speed?

what is ur current setup? best power curve is to use 1 midbox only, if its too noisy, better swap smaller pipe and get bigger body straight muffler at the back

mine is a straight flow setup but sounds like sflow. the back muffler has small piping and really big body.

i suppose ull get more power across certain rpm with 12" distance but no special peak. if u want some noticeable boost, use only one 3" midbox in the middle, everything else remain the same. this will fatten ur midrange, trust me

noise wise, if the drone is bothering u, custom a side branch resonator. this will confirm eliminate the drone. ill tell u how to do if u want




This post has been edited by upontheriversky: Sep 24 2011, 11:13 PM

wat is d sid branch resonator?how to do it my current setup is 4-2-1 powerzone extractor,bullet,midbox then is s flow muffler..my one is auto..the whole piping still remain ori size..

bro, I like how you mention this.

so earlier I post a question for a reputable exhaust shop for suggestion.

can I get some suggestion from you too.

i'm trying to get better overtaking,pickup,good response,snappy feel with speed range of 60-130km/h, rpm i think 2.5k to 4.5k



also from your post, I found out that the very important thing is where to place the muffler/midbox/bullet and length apart from each other. also size of piping and size of muffler/midbox/bullet

i could not come up with anything even after taking note of all this.

original piping size for Myvi should be 1.6" i'm not wrong.

This post has been edited by [ r u g a ]: Sep 26 2011, 08:31 PM

hi, tell me what is the best header and inch for piping to stock H22A. thanks

2.5 inch?.. heavily modded can consider 3.0 inch...

What bhp is the H22A producing?
My 200bhp done with 2.5" and if above 250bhp recommend 3" piping

can u describe the power from this setup?

my honest opinion for best city torque setup, keep ur 4-2-1, use 1 big diameter straight bullet, 1 big body straight muffler having same diameter as ur tailpipe. If u need a 3 restrictors (bullet, midbox, sflow) for ur engine to run good then ur piping size is more than big d, get a small diameter piping, NA is about flow velocity, turbo is about flow volume

1 big bullet is to separate ur 4-2-1 and downpipe tuned length, a straight muffler having same diameter as tailpipe and big body is to keep the straight flow noise to street friendly level

exhaust cools down and slows rapidly as it travels thru piping which induces backpressure so having big piping at the back does not make ur car torque-y, not that fun to drive IMO. Dont get confused with drag exhaust setup, those cars cant beat torque-y small engine small exhaust car in heavy traffic hehehe

i quote this from other site for side branch resonator, just read carefully and apply to ur scenario:




hehe touge spec engine is nice to drive across LDP/ MRR2 right? im having the same mindset too fast rpm climb at cornering exit, highest torque output across 2.5k - 4.5k for kelisa is what i need for non-track application. i dont bother with 5k power and above for a small engine, i keep tuning practical hehe

my usual place is torque gear and supercircuit in sunway, i like the workmanship but the price can be reasonably high. if small simple stuff i go to wai heng sunway instead coz its cheap. but if u know the design and spec, what u can do is go to cheap exhaust shop (wai heng, wei yip) and supervise them to do it. check welding finishing making sure no leaks after finish, basically be a b****y boss checking everything before u finally pay, i hate doing that coz seems disrespectful to the workers so judging by the work needs to be done, i select the desired shop

yes indeed bro, diameter tuning unlocks probly 40% of ur exhaust potential, its the length of ur header and downpipe to first bullet that makes the big difference

try this, if u r on 4-2-1, assuming extractor length is 15" like mine, then use 37" downpipe length and put ur bullet there. if header length is different, just makes sure header+downpipe length = 52". +- 1 inch is ok.

use 1.6" piping for downpipe, this will flow good up to 4500rpm on myvi engine. with myvi exhaust open BBDC at 30 degree, 52" of header+downpipe would give u boost at myvi peak torque 3200 rpm. for max boost effect, ur bullet internal pipe volume has to be minimum 2X engine cc i.e. 2.6L of bullet volume

if 4-1 then 52" starting from extractor flange to end of downpipe then put bullet there.

i tested this theory on kelisa, 34" downpipe to boost at 3500rpm, i felt boost at 3400rpm which made me happy coz it was really close to my approximation.

try this first and let me know the result, then i can propose something more to lengthen the boost duration

oh yeah, avoid openpodding ur intake, it does not do good for touge tuning, keep ur airbox, modify it to let airflow in easily up to ur rpm habit and call it a day. once air can flow easily thru ur airbox, there is no need for aftermarket drop in. use oem filter that was highly R&D-ed, designed and tested purposely for myvi

This post has been edited by upontheriversky: Sep 27 2011, 10:32 PM

Can I apply this method on blm??

wow. you really goes into calculation on that.
thanks alot for sharing. i'm not good at math and this really helps.

and yups on the practical tuning, since there will be no chance of track full performance on this car.

actually I'm going to do whole set of exhaust from extractor onward, since I have a 4-1 Stainless Steel Hotbits(OEM Fit) I'll just keep and use it.

basically I need to enquire more from you It seems like you are around subang/shah alam area too, if really wanted to experiment the different with me we should maybe further meet up when I'm going to do it. most probably also around sunway or shah alam area(wai heng new branch seksyen 20)

but I'm absolute newbie on this, first car, first exhaust change. plus this change is also because partly the exhaust has some unwanted noise because of wear and tear in muffler as mention in my last post.

yeahh I did not open pod on this car since is an auto, instead there's a high flow drop in there.
__________________________________________________________________________________________________

theres still tons of doubts regarding my setup.

from what I understand and confirm till mid section is that, placing of the bullet/midbox is aprox. 52" from starting from extractor(from engine) till after downpipe with volume of aprox. 2.6L(?)

you mention that correct tuning of exhaust doesnt really just stick to those 4-1, 4-2-1 or not, straight or sflow, straight or oem pipe route.

so basically even auto can go full straight or manual can go all s-flow they wanted provided that we used the correct theory and matching.

but my problem is now selecting and mix matching all those to form a applicable setup set.
__________________________________________________________________________________________________

So you mention good exhaust system only play with 1 bullet/midbox and 1 rear muffler.

Its time to decide whats the suitable middle part, I suppose bullet is either straight or swirl, and midbox is something like s-flow box. And from your concept of termination box, we should stick to bullet and not a midbox?

how about the internal diameter, inlet and outlet of the bullet? length? I really don't know how to see if the bullet makes up to 2.6L of capacity.



Progress;

4-1 Extractor --> Downpipe 1.6" --> [52"] Bullet 2.6L --> ?

Piping size after bullet = ?
Distance to place rear muffler = ?

p/s : now I wonder, can my Auto Myvi go with straight muffler with this 1.6" piping with 1 bullet and not be crazy loud.
too much doubt lol. or I should downsize the piping.

This post has been edited by [ r u g a ]: Sep 29 2011, 09:32 PM