How to adjust backpressure?

[Veloc]

Guys and seniors... I have an issue here that is too much backpressure.
The story is like this... When I bought my Corolla AE111, 4AFE as a second hand, the driver fixed a straight flow muffler with 2.0" dia. inlet and 2.5" dia outlet. This is too noisy and i find the bottom end too weak.

So I changed it back to the s-flow type muffler. The prob is, the dia of the muffler is 1.5". I didn't know before this. The guy only tell me after it is fixed. The original pipe size for 4AFE is 1.75". Torque from 1k - 2.5k rpm is really great but after that, the power is rubbish. no mid range torque. Difficult to accelerate.

To summarize,
At first, my piping was 1.75" and modified to 2.0" towards the rear.
After fixing, my piping was 1.75" modified to 1.5" towards the rear.

I just want to ask is it possible to lower the backpressure by puncturing a few small holes somewhere at the rear of the exhaust piping? I wouldn't want to change the muffler already as I spent a lot of money on it. Can it cure the mid-range torque kill?

Please refer to the diagram on where I want to puncture the holes.

Any sifus can advise? Thank you and really appreciate it!

 

[scoupe]

hey man, i doubt the holes is gonna improve anything.. i think its gonna make things worst.. the flow characteristics is gonna be all over the place.. i dun really see a solution but to change the muffler and get a 1.75in inlet one..

 

[arturo]

Veloc....i think it'll be better to just change back to 1.75".

 

[DanzEterna]

try changing your extractor to tuned length ones.

 

[FGT]

Veloc....i think it'll be better to just change back to 1.75".

Agree and highly recommended.. That's the best setup for power and consumption balance..

But then again, it depends on your preferences.. Mine is an auto. I stumbled upon this setup by accident as I knew nuts about 4AFE when I did this: I got the cat-con removed as it was already rattling. Next the "S" bend near the rear lower arm was replaced with the same size due to leak because of rust (i think it may have hit something at some point of its life). Then I installed the S-flow rear muffler from my old car with 2.1" inlet (or 2.3" cant remember). Only had to attached an adapter at the end of the piping -- no changes made to piping size. I'm not sure what happened but the low-range torque is improved and cruising at 110kmh felt smoother (i think rpm is lower now) and currently doing 65km for every RM10 with Ron95 at RM1.85 :)

 

[Veloc]

Change muffler? That is sad... Have to spend a bunch again... In that case, guess I'll just have to bear with this until I collect enough money to swap in a blacktop straight. Do not want to spend a lot on this engine now... I have already spent enough when I acquire this car as the previous owner is a noob in maintaining car. I am just looking for a low cost temporary solution...

So making some holes really wouldn't ease the backpressure huh?
Sad... Sad... Sad...

---------- Post added at 11:56 AM ---------- 6 hour anti-bump limit - Previous post was at 11:55 AM ----------

That is really a stupid exhaust shop. Damn them to the end!


Why...

 

[3zz]

easier way just buy whole exhaust piping from apexi,hks,or fgk or ae...
got straight flow got s flow oso

 

[FGT]

Change muffler? That is sad... Have to spend a bunch again... In that case, guess I'll just have to bear with this until I collect enough money to swap in a blacktop straight. Do not want to spend a lot on this engine now... I have already spent enough when I acquire this car as the previous owner is a noob in maintaining car. I am just looking for a low cost temporary solution...

So making some holes really wouldn't ease the backpressure huh?
Sad... Sad... Sad...

Heh chill bro.. just change the 1.5" section to 1.75". Should not cost too expensive. Please bear in mind that it will still semput around 4500-5000rpm. This is normal for 4AFE. Sifus, pls correct me if i'm wrong.

Muffler only need to change if needed. Just shake or knock it a bit. It should be still good if there are no rattles. For my case, I just want the extra bit of noise. Heheh..

 

[Veloc]

Heh chill bro.. just change the 1.5" section to 1.75". Should not cost too expensive. Please bear in mind that it will still semput around 4500-5000rpm. This is normal for 4AFE. Sifus, pls correct me if i'm wrong.

Muffler only need to change if needed. Just shake or knock it a bit. It should be still good if there are no rattles. For my case, I just want the extra bit of noise. Heheh..

Cannot bro... The inlet of the muffler is 1.5". Nevermind... Guess I just have to bear with the loss of mid-range torque for around 2 years i hope? Then change to BT.
Btw, what does FGT means? Are you referring to the corolla FGT?:hmmmm:

 

[xtremeleo]

i replied to this thread, but cant find it anywhere now.. musta been the network at office having a dull moment, lol.

iam using an iswara with a 4g91, zorst pipe is 2inch, but the zorst flow is adjusted properly with an s-flow muffler. we spent quite sum time jugek to find a muffler dat is suitable for my setup, a muffler dat compliments the engine's performance to give responsive result from the bottom end, and adjusted the cams for top end power. the engine has been dynoed and give a flat torque of 90 lb.ft through the revv range.

i dont see y u cant get the same effect if ur engine is set and tuned properly sir. pm for more details, tq sir

 

[arm77]

i do think muffler does'nt cost much maybe around 400-500 or less than that,

 

[xtremeleo]

i get a good muffler design and good quality for cheaper. pm for detail on the pricing. i dont think its proper to post it here

 

[FGT]

Cannot bro... The inlet of the muffler is 1.5". Nevermind... Guess I just have to bear with the loss of mid-range torque for around 2 years i hope? Then change to BT.
Btw, what does FGT means? Are you referring to the corolla FGT?:hmmmm:

Ah i see..I thought only the piping is 1.5" because u said "towards the rear'..sorry bro.. Anyway, yeah, have to fork out another 180-250 for a standard SEG muffler.

FGT? err..long story la..haha..but long story short, wasnt a corolla fan at first! hahah.. :P

 

[csl]

Pressure can be reduce but flow will be still restricted.