.: Exhaust Modification Corner :.

[Andy0625]

possible sources:
the pecah sound can come from the 3"-4" muffler, this type of muffler acts like a hailer/trumpet (small mic to big wide flared mouth to widen and amplify the sound) so any noise from engine will be amplified when it goes out the 4" mouth, and uve got 2" piping going to 3" and 4" at the end so it behaves much like a hailer. Bassy sound sflow usually has constant diameter, so it only gets noisy when exhaust flow rate is fast i.e. acceleration

u have changed to swirl bullet and the pecah noise still persists, it is a good indication that ur FGK muffler is the culprit.

my recommendation is swap the 3"-4" FGK to 2" big body (non-trumpet) straight flow muffler. I bet u will get improvement in both noise level and performance

My experience: i swapped my 2" oval straight flow to 1.6" big body straight flow and the noise level decreased a lot and gained top speed at the same time :)

---------- Post added at 04:55 PM ---------- 6 hour anti-bump limit - Previous post was at 04:48 PM ----------



if low end is not satisfying, try change the 2" piping after last bullet to 1.75", smaller pipe has higher exhaust velocity at low rpm so it helps.

thanks for reply bro.
any reasons to change to smaller piping after the last bullet and not start right at the connection with extractor?

 

[endy7527]

Im using kenari-VET, strait flow system. Now wan 2 change the whole system coz tired wt the sporty sound. I'm planning to use single s-flow muffler. I was thinking to use FGK or Tanabe muffler. How much the s-flow will affect my performance & FC?

Really need an advice for this thing.

 

[upontheriversky]

thanks for reply bro.
any reasons to change to smaller piping after the last bullet and not start right at the connection with extractor?

exhaust gas cools off rapidly as it goes from extractor to the tailpipe, u can lightly touch the tailpipe on hot days but definitely not the header on any day :)

reason:
- cooler exhaust is denser therefore heavier and slower
- also exhaust velocity increases with temperature, so cooler exhaust is slower, smaller pipe as u approach the end keeps the velocity higher which is the key to NA street exhaust performance. The front part before bullet can be made bigger since exhaust is much hotter here so it is rather fast already, no need to worry too much about gas velocity.

So by making front part bigger, we can take advantage of more exhaust flow volume coz exhaust can be dumped more at a short time giving what we call "pickup"

i like to think of the whole exhaust system as a water nozzle, the engine being the water tap and tailpipe is the nozzle, smaller nozzle shoots out water faster while big nozzle needs more water pressure to get the same velocity as the smaller one..so we can see low end power on big nozzle is obviously compromised

this is mostly true for street exhaust, racing purposes im not so sure :)

 

[Andy0625]

exhaust gas cools off rapidly as it goes from extractor to the tailpipe, u can lightly touch the tailpipe on hot days but definitely not the header on any day :)

reason:
- cooler exhaust is denser therefore heavier and slower
- also exhaust velocity increases with temperature, so cooler exhaust is slower, smaller pipe as u approach the end keeps the velocity higher which is the key to NA street exhaust performance. The front part before bullet can be made bigger since exhaust is much hotter here so it is rather fast already, no need to worry too much about gas velocity.

So by making front part bigger, we can take advantage of more exhaust flow volume coz exhaust can be dumped more at a short time giving what we call "pickup"

i like to think of the whole exhaust system as a water nozzle, the engine being the water tap and tailpipe is the nozzle, smaller nozzle shoots out water faster while big nozzle needs more water pressure to get the same velocity as the smaller one..so we can see low end power on big nozzle is obviously compromised

this is mostly true for street exhaust, racing purposes im not so sure :)

Thanks for your reply! Really learned a valuable knowledge on exhaust today. In this case, do you suggest me changing one of the bullet to midbox? Reason for me to ask is because 2 of the bullet that comes originally with the piping seems to be small in diameter/width which in my opinion, less wool/fiber inside to absorb noise? or should I change the piping first and see how the sound will like?

 

[GEFORCEXTREME]

exhaust gas cools off rapidly as it goes from extractor to the tailpipe, u can lightly touch the tailpipe on hot days but definitely not the header on any day :)

reason:
- cooler exhaust is denser therefore heavier and slower
- also exhaust velocity increases with temperature, so cooler exhaust is slower, smaller pipe as u approach the end keeps the velocity higher which is the key to NA street exhaust performance. The front part before bullet can be made bigger since exhaust is much hotter here so it is rather fast already, no need to worry too much about gas velocity.

So by making front part bigger, we can take advantage of more exhaust flow volume coz exhaust can be dumped more at a short time giving what we call "pickup"

i like to think of the whole exhaust system as a water nozzle, the engine being the water tap and tailpipe is the nozzle, smaller nozzle shoots out water faster while big nozzle needs more water pressure to get the same velocity as the smaller one..so we can see low end power on big nozzle is obviously compromised

this is mostly true for street exhaust, racing purposes im not so sure :)

Nice post, but the way I see it, is right from the engine. When the exhaust system is restrictive, the force produced from combustion is used to push harder your pistons, so you get more torque. In a less restrictive exhaust system, there is more "leak". Instead of pushing your pistons harder, some of the force is "leaked" through the exhaust system.

---------- Post added at 06:35 PM ---------- 6 hour anti-bump limit - Previous post was at 06:33 PM ----------

I don't think it is something to do with how fast the exhaust gas flows out, rather how much pressure or how restrictive it is. That's why ppl say you need some back pressure for low end, otherwise on the high end.

---------- Post added at 06:40 PM ---------- 6 hour anti-bump limit - Previous post was at 06:35 PM ----------

Just take the blowing balloon as an example. When a balloon is good, you blow it, and it becomes bigger, but when there is a hole there, you blow hard, but the balloon grows bigger at a lower rate.

In this case, the exhaust system, how restrictive is it is just like how big the hole is.

---------- Post added at 06:43 PM ---------- 6 hour anti-bump limit - Previous post was at 06:40 PM ----------

So "I think" besides the exhaust setup, the valve timing should be also part of the equation, for eg when you use high cams and such.

 

[AeroDek]

Need help all sifus..
My car 4G93 hi compression hi cammed
cusco replica 4-2-1

before:
2"piping
midbullet long
trumpet muffler
result: good respone and pickup

Current setup:
2.2inch pipe
same mid bullet long
straightpipe
rear bullet short
after that Y split twin pipe ended with tip
But the Y split is 2.5 inch.
Result: sluggish pickup,the rev become slower than before.

So what are suggestion to get my pickup again??
1.Add twister bullet
2.Change mid bullet to square type straight flow
3.s-flow
4.???

I also cant decide alrdy. huhuhu headache2

 

[^pomen_GTR^]

Need help all sifus..
My car 4G93 hi compression hi cammed
cusco replica 4-2-1

before:
2"piping
midbullet long
trumpet muffler
result: good respone and pickup

Current setup:
2.2inch pipe
same mid bullet long
straightpipe
rear bullet short
after that Y split twin pipe ended with tip
But the Y split is 2.5 inch.
Result: sluggish pickup,the rev become slower than before.

So what are suggestion to get my pickup again??
1.Add twister bullet
2.Change mid bullet to square type straight flow
3.s-flow
4.???

I also cant decide alrdy. huhuhu headache2

change back into 2inch pipe.....

 

[D7zul]

bigger DOES NOT mean better..

especially for exhaust..

if i were u, i change back to 2" pipe..

above than 2" is good for turbo/supercharge or bigger engine

 

[TitanRev]

I've did some readings and findings and my stock exhaust outer diameter is 2.3 inch..how much would the inner be? my guess is 2 inch...the engine is a 2.4 liter AT with Mivec. I havent changed any part of the exhaust and my plan is just to get the rear muffler replaced with a less restrictive one. I've saw Fujitsubo's website also recommends using back the same diameter but most exhaust i saw on sales are 2.5 inch...there's justa slight difference between 2.3 and 2.5 but I wonder if it's ok...

 

[D7zul]

i don't know about u guyz.. but for me, i prefer an aftermarket exhaust system.. not the 'pakar ekzos' custom one..

for daily use, a slightly bigger exhaust is good .. around 0.25 inch bigger than stock exhaust..

for drag race, around 0.5 inch.. i think.. depend on the mods too..

and this is for manual transmission of coz.. if auto, u'll feel ur car very sluggish..

 

[superchargedx]

hi my currently set up for my ke70 4agze with 4-1 extrator straight pipe 2.5 till the aftermarket s-slow..
it seem like bit loud, i wanna more silence. is there any suggestion?

what i gonna do is :
-change the 4-1 to 4-2-1 and add in a 2.5 straight centre bullet.

any suggestion?

 

[D7zul]

hi my currently set up for my ke70 4agze with 4-1 extrator straight pipe 2.5 till the aftermarket s-slow..
it seem like bit loud, i wanna more silence. is there any suggestion?

what i gonna do is :
-change the 4-1 to 4-2-1 and add in a 2.5 straight centre bullet.

any suggestion?

i think changing the extractor won't reduce sound..

put in bigger center bullet for quieter ride..

just my opinion.. waiting other people to comment..

 

[superchargedx]

hm thanks for ur suggestion bro....add in straight type centre bullet will reduce a lot the sound?

 

[D7zul]

most center bullet is a straight type..

small bullet reduce sound a bit..

big bullet reduce sound a lot..

gudluck

 

[superchargedx]

wu...ok so what ur mean is 2.5" used 3" centre bullet? how bout maintain 2'5" centre bullet with 2.5" piping?

---------- Post added at 11:05 AM ---------- 6 hour anti-bump limit - Previous post was at 10:20 AM ----------

get what ur mean dy..haha...body of centre bullet bigger more silent..haha..any way that for ur comment.. :)

 

[D7zul]

sorry, my comment is not very clear..

the body of the center bullet will determine how loud ur exhaust sound..

usually people use the same pipe size for their exhaust system..

 

[blissfulshadow]

Hi, I want to ask about Proton Savvy. Anybody can help? Kweng?

My proton Savvy is AMT..

I want to change my exhaust system to 4-2-1 extractor, 2inch pipe, 1 twister/swirling bullet (change my normal midbox), and s-flow muffler.. will it be very nice? in low end to high end? I want pick up.. but i don't want loud noise like changing to straight mufflers even though this car can change to straight mufflers..

Anyone?

 

[kokhing]

can i still find 1.6/1.5" inlet outlet bullet and muffler in those exhaust shop now?
mostly i saw they selling only 2.0" only ><

 

[^pomen_GTR^]

can i still find 1.6/1.5" inlet outlet bullet and muffler in those exhaust shop now?
mostly i saw they selling only 2.0" only >quote]



don't go to those shop with "stock like a hill"....just normal small exhaust shop surely u'll find those small size bullet...


as i do have it installed end of last year on my stock car....no sweat with that....now happy with the "stock mivec" sound and improved acceleration a bit.. (my stock car was auto btw)

 

[mick87]

what will be a better suggestion for Alza 1.5 Auto?
what i need is smoother pick-up, better fuel consumption or same but with improvement on performance.