SOHC 4G93 Losing Torque

[kairigi]

Guys, I know I don't belong with you 4G6X engines
But something is very wrong with my car.. I'm lacking a lot of throttle response for a 1.8, and my throttle fuel consumption is quite high.. I'm not sure whether this is a problem with my setup,

SOHC 4G93 NA
F4A42 Auto tranny
2" piping with kinda big muffler (wrong choice since I had to rush to replace)
Stock extractor

I'm quite sure it's my exhaust setup.. that or my engine has serious problems.

I mean, this engine is GDI but my carbureted wira has better pickup and response than it..

Any sifus know why? Mind sharing your 2 cents?

 

[xtremeleo]

was it performing good before u changed the muffler to dat "kinda big" unit sir? i suspect its the muffler, it is a straight flow design?

 

[kairigi]

was it performing good before u changed the muffler to dat "kinda big" unit sir? i suspect its the muffler, it is a straight flow design?

performance wise i dont know because i just bought the car recently and i quickly changed the muffle because it was tin kosong.. (no more fiber)
hmm yea straight pipe.. i think it was meant for turbo engines. A lot of my friends told me to change into s-flow but im not sure of the differences. straight flow releases exhaust very fast until my car has no backpressure? so i need s-flow to keep some backpressure? :hmmmm:

 

[xtremeleo]

i dont think there are such a thing as "muffler for turbo" or "muffler for na", the most important part is it suitable for ur application. sum guys prefer the curve to be steep at the end and opted for the straight flow muffler design with a big diametere zorst pipe, and sum guys prefer the engine to be responsive and go for an s-flow muffler with moderate zorst pipe, its up to ur preference actually.

i think u need a good s-flow muffler design sir

 

[HKS-GT2835R]

performance wise i dont know because i just bought the car recently and i quickly changed the muffle because it was tin kosong.. (no more fiber)
hmm yea straight pipe.. i think it was meant for turbo engines. A lot of my friends told me to change into s-flow but im not sure of the differences. straight flow releases exhaust very fast until my car has no backpressure? so i need s-flow to keep some backpressure? :hmmmm:

s-flow, like its namesake..

automatic cars needs a bit of backpressure to make things work.

 

[^pomen_GTR^]

that warlock s-flow muffler looks good...

 

[lancer7891]

Hmmm...

maybe your oversize your exhaust pipe kot...

or maybe you can re-check your A/F ratio..

just my 2cent...

Your engine GDI SOHC?

 

[kairigi]

thanks to all your opinions guys.. really cleared my mind a bit hahaha :)

@lancer7891 yup gdi sohc..

 

[HKS-GT2835R]

thanks to all your opinions guys.. really cleared my mind a bit hahaha :)

@lancer7891 yup gdi sohc..

It's just bernoulli's principle lar.

IMO maybe not so about back pressure, but I believe that you’re really talking about flow velocities. see, you just changed that by adding a bigger diameter pipe.
blowing thru 4 straws instead of 1.

A smaller pipe will tend to keep the flow rate up. However, a large pipe will slow the velocity due to expansion. and, the exhaust gas is constantly cooling from the moment it leaves the cylinder, meaning it’s getting denser and slower (since the slow velocity caused by bigger pipe).

 

[Veloc]

i dont think there are such a thing as "muffler for turbo" or "muffler for na", the most important part is it suitable for ur application. sum guys prefer the curve to be steep at the end and opted for the straight flow muffler design with a big diametere zorst pipe, and sum guys prefer the engine to be responsive and go for an s-flow muffler with moderate zorst pipe, its up to ur preference actually.

i think u need a good s-flow muffler design sir

Agree... Before I changed my muffler to s-flow for my 4AFE, I was using straight flow with 2.0" diameter. The stock is s-flow with 1.75" diameter. After I changed it, there is a significant bump in throttle response and low-end torque. I think 2.0" is a bit overkill for a 1.8L SOHC too... Maybe try use 1.8"?

 

[kairigi]

@HKS - I guess 1.8s can't bear with 2 inches then..

@veloc - I heard a lot of people commenting me to use 2 inch since 1.8, even in other forums, they all use 2 inch for my engine.. but since mine is an auto.. i guess i know why not hahahaha. my car is not with me right now, my friend is taking care of it. he told me he's going to try to change to s-flow for me soon, and i'll ask him if there is any big differences :)

 

[xtremeleo]

its not so much about the zorst pipe when u know how to preserve the flow. i know of a guy dat uses 2.5inch in his 4g91, and yet the engine is responsive in ALL the gears, mainly because of the HKS s-flow muffler at the end. yes, u guys know who he is.. and his legendary iswara, hehe..

 

[kampoon]

S-Flow is always advisable for Auto Tranny, here is some advice:

1. Piping - make sure dun enlarge your piping too much if your car is stock.....stock pipe is 1.6" and you might looking into enlarge it to max of 1.8"
2. Extractor - replace extractor with 4-2-1 if you wan more response for daily street use or 4-1 if you still need your top speed in case.
3. Decat - will be a good choice for your pocket but not to the environment
This will reduce the fuel consumption and will increase the ekzoks air flow.
4.Centre Bullet - make sure that some modification to be carried out by the ekzoks installer b4 they install it to ur car (Auto and Manual setups for Ctr bullet is diff)
5. Muffler - S-Flow is a must for AUto Tranny (please accept it and this is the fact...)

My 2 Cents.....
Happy Modding

 

[Veloc]

S-Flow is always advisable for Auto Tranny, here is some advice:

1. Piping - make sure dun enlarge your piping too much if your car is stock.....stock pipe is 1.6" and you might looking into enlarge it to max of 1.8"
2. Extractor - replace extractor with 4-2-1 if you wan more response for daily street use or 4-1 if you still need your top speed in case.
3. Decat - will be a good choice for your pocket but not to the environment
This will reduce the fuel consumption and will increase the ekzoks air flow.
4.Centre Bullet - make sure that some modification to be carried out by the ekzoks installer b4 they install it to ur car (Auto and Manual setups for Ctr bullet is diff)
5. Muffler - S-Flow is a must for AUto Tranny (please accept it and this is the fact...)

My 2 Cents.....
Happy Modding

Kampoon sifu,

A few people told me this before too. That Straight flow is nto good for auto. I also experienced it myself when I changed straight flow to s-flow. Can explain why please? I really don't understand.... So big difference? Why is the difference not so obvious in manual?

 

[kampoon]

Kampoon sifu,

A few people told me this before too. That Straight flow is nto good for auto. I also experienced it myself when I changed straight flow to s-flow. Can explain why please? I really don't understand.... So big difference? Why is the difference not so obvious in manual?

automatic gearboxes are VERY sensitive to back pressure. if you using straight flow muffler, it will allow more air to flow directly faster and that will definitely reduce or remove back pressure, you will definitely need a s flow setup in-order to maintain the torque for your engine.......

 

[kairigi]

Wow... thanks for the big info kampoon! this will definitely help!

But is aftermarket s-flow better or standard? in terms of car beauty of course aftermarket but performance?

 

[xtremeleo]

of course aftermarket sir, the standard unit is made more towards improving fuel consumption and emission. but then, u need to select the best one for ur application or else its gonna be worse then standard setting

 

[kampoon]

Build quality for standard muffler is always better and will last longer....if you want better sounds and looks better, you should goes for the after market....make sure you chooose the right size this round....dun be suprise that ori muffler also made by Stainless steel......hehe

 

[kairigi]

hahahaha thanks to u 2 bros.. will seek some out and ask from u 2 ifi have any more questions :)

thanks!

 

[HKS-GT2835R]

@HKS - I guess 1.8s can't bear with 2 inches then..

@veloc - I heard a lot of people commenting me to use 2 inch since 1.8, even in other forums, they all use 2 inch for my engine.. but since mine is an auto.. i guess i know why not hahahaha. my car is not with me right now, my friend is taking care of it. he told me he's going to try to change to s-flow for me soon, and i'll ask him if there is any big differences :)

its the combination of yur pipe diameter + yur muffler design /type lar.

and you really shouldn't use anything bigger than stock piping's diameter. if it's rusty or damaged, i'd replace it with the same diameter pipe.

on the 'bigger exhaust only fer turbo' part, here's my exp. this was some years ago meh!

(this mishap was on my RB20det's uber-fragile-on-higher-boost ceramic turbo).

i upped the 2.0" pipe to 2.5" from dumpipe straight to the rear bumper with no muffler. the throttle response was improved by a bit, but blew the exhaust side turbine wheel to pieces some few days later, IIRC. i believe reason fer that is the boost did increased by a bit (it went higher than .8bar) after the fitment of the bigger pipe, but i left it like that ( i should'nt be THAT ignorant)

the IHI rhf4 was in place, till now.

damn garrett!