ok anytime u guys wanna do around next month count me in, never been on dyno before


how much GT auto charging?

if its ej-ve, get 1.5" piping since thats the smallest ive found so far, stock piping size is hard to find in kl area, i got a friend in penang says got 1.4" if u want to travel all the way there


actually the cat-con can be used as termination box as it does expand the gas to a bigger volume, its just that the boost strength wont be as high as using a bigger volume termination box. i suspect honda use catcon as part of their exhaust tuning on their new models, some of my friends on new honda jazz complaints after changing to 4-2-1 extractor and losing power they used to have but got gain in higher end, i guess the power loss is due to removal of the catcon. the tuned exhaust must have been sync-ed with oem airfuel tuning so removing it tempers with oem air/fuel ratio as well

to play safe so that we wont temper the oem exhaust tuning if there is any, can use cherry bomb bullet to replace catcon, its still an expansion chamber only its free-er flowing of course than the cat

yea, i always thought of that but i cant be sure for now, i have to do dyno on my car and study it. there is also one thing to consider, if it resonates at 4000rpm, there has to be some rpm where anti-resonation occurs in which we will have a torque dip so i guess best to consider all this when choosing rpm to tuned for

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

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

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

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

3-2-1, 1.5" piping, bullet and straight flow muffler, mine is a manual


got it


ok getting more power at higher rpm is consistent with ur current straight flow, that is the trade off of exhaust mod, u gain in one end, and u lose on the other, for ur case, power only felt boosted at 3.2k instead of 2.8k but ur higher end power is more.

do u like the power u have now in higher rpm? or u like the setup but wish the starting boost stays about the same rpm as before? or anything else that u want to improve?

u will feel higher boost with bigger pipe diameter midbox but since noise is an issue, if got space why not install another midbox right after the first one? the bigger the pipe diameter the better but if scared too noisy then keep to same diameter on what u have now but the potential would be limited. it muffles better than bullet and if the 2 midboxes are close enough to each other it would form a bigger termination box than what u have now and thats good for power overall, but some exhaust shop would refuse to do this, i think it would work.

from end of extractor to the first bullet or change of pipe area

collector length usually refer to downpipe, point from header merge collector outlet where 4 pipes merge into one until the first bullet.

the flexi is also a change of area but not a significant one

yes, try allow a length of collector pipe minimum of 18" before putting bullet in, the downpipe will improve torque across all rpm, not just the low end. this is a general number though

if u after a wide powerband:
what about readjust collector length to tune at 4k - 4.5k rpm to raise the torque dip and adjust pipe size so it still maintain high flow velocity at 3k rpm?

if u after for best power:
tune length at 5k u will get high boost when u reach max torque, the dyno curve will form a steeper hill, have to change gear often to stay "tuned" but peak power is increased

small pipe needs throttle control for pickup, big pipe can floor the pedal for instant response

my humble opinion only hehe


i 2nd that, u are indeed a wise person to kitai back the exhaust guy hehe

now i understand why exss exhausts are damn expensive, those blocked mufflers are legendary..didn think we can get it here locally. its perfect for wave tuning purposes

is the midbox blocked type too??

This post has been edited by upontheriversky: Dec 15 2011, 02:55 AM

My general rule of thumb for street exhaust system:

Big front piping/collector before centre bullet/midbox, small back piping after bullet all the way to tailpipe

So far ive seen consistent result with 3 different cars, kelisa, proton waja and putra, all stock engine.

highly impressive pickup / low end to early mid (2k - 4k) due to big sized collector to dump a lot of exhaust at short time during lower gears, the choke only comes at higher rpm (4.5k and above) due to smaller piping at the back but this maintains high exhaust velocity which is pleasant to drive/cruise in highways. Town driveability and top speed are still maintained satisfactory.

Small back piping also suppresses the noise so its a well balanced setup for town driving.

Imagine ur whole exhaust system as a venturi piping (big to small), so exhaust gains velocity progressively as it goes from big front piping to smaller piping at the back

Be practical, we will probably rev high for first few months after exhaust mod due to excitement and start getting bored and spend most of the time cruising at 3k (which happened to me ) so this setup is worth on the long run

cheers

This post has been edited by upontheriversky: Mar 25 2012, 04:18 AM