I was thinking of putting in a straight flow exhaust... but then i hear a lot about back pressure importance and stuffs. please advise....

straight flo as in the box or one long straight mid section. if it's the box, keep it s-flow but with bigger internals.

straight flow as in ermm... the box where i can see tru it to the other side...

currently im on sflow and its partly see tru if angled properly (when u see it tru one hole to the other side.) Mine has a plate on the mid section. 2 inch internals. but on stock pipes.




Dotted lines is the line of sight that u can see tru it if u angle it properly. its still consider sflow?

My ride is MyVi automatic.

This post has been edited by jasondotcom: Mar 14 2007, 11:18 PM

but an Auto car with modded exhaust have worst sound.

updated see photo above

myvi, go for hotbits full exhaust system if u have the money...
i heard its good

I am also using S-Flow, the sound is okay...not loud as straight flow....straight very noisy >.>

so confirm cannot use straight flow lar rite? iyah...too bad. too too bad.

eh how come cannot find any infor in google on sflow exhaust? and how to search in google for this kinda exhaust infor for diff. type gearbox... like which design exhaust is for which etc....

This post has been edited by jasondotcom: Mar 14 2007, 11:37 PM

you can use it if you want ler, no problems 1
Just make sure got enough backpressure

why need back pressure? i read some articles in the net says that to reduce back pressure as much as possible ler... im really

s-flow muffler...


straight flow...

My Honda exhaust tip rustied, I changed twice but it cannot last long. The whole exhaust still okay but only the "outlet part" is rusty !! Any advise ??

This post has been edited by Skyblue: Mar 15 2007, 09:07 AM

A very good and easy understanding write up about exhaust system.

http://www.sportcompactcarweb.com/tech/991...xhaust_systems/

2nd to this. You cannot tarik long long one.. but different people have different taste.

DUmb me, but will there be any benefits changing the exhaust flow except for some noise change?

Then what do you call this type of exhaust, with a side pipe?
Whats the benefits of this type of muffer?

Can it be also classified as S-Flow muffler?

[attachmentid=204689]

This post has been edited by SleeplessEyes: Mar 15 2007, 01:17 PM

why so easy rust??... original replacement muffler arr??..
previous flood in johor, my friend's gen2 muffler rusted inside because she drove pass a floor and the water being sucked into the muffler... thats why people say driving pass a flood, gas pedal must constantly revving so that water is not sucked back into the muffler.....

changing to straight flow reduces back pressure.... good for pickup in manual cars... auto tranny cars, better stick to s-flow box...

twin loop exhaust... usually used in vtec engines....
but i dont know how it works la... so many loop will cause restriction rite??...

This post has been edited by the_catacombs: Mar 15 2007, 04:20 PM

Heard that it works by letting the exhaust go through the muffler twice.
So the noise is filtered twice, but without actually using two mufflers and no need for restrictive silencers.

I've once used a straight flow for my previous wira (auto) and totally regretted the decision.

the oredy lousy pick-up becomes lousy-er. FC increase terribly. and worst of all, the sound is irritating.

after a few months of using it, I sold the car.

If u thinking of using a straight flow, think twice.

cheers.

This post has been edited by shackks: Mar 15 2007, 04:51 PM

Okie. thanks guys for the inputs. im sticking to my s-flow exhaust.
but.... now im thinking if those twin loop exhaust were any better? hahahah...

maybe on of the forumer here kweng can answer ur question... he got customer who change to twinloop... but the car is civic la..

fr what i heard twinloop benefit vtec most.... auto car also benefited fr it....

okay, let get things spicy a little in here..

I have a doubt, according to what Gouki's posted (http://www.sportcompactcarweb.com/tech/991...xhaust_systems/) I got confused on what is backpressure. At first, it stated there that the exhaust at least needs backpressure and while you keep on reading, it will says that engine doesnt need backpressure. Now, what is the difference between this two? The exhaust needs backpressure? But why?

Aside from changing the muffler unit, why not redo the tubing of the exhaust to gain power? Does this can be done? Use new tubing size from CC to muffler and ends with original muffler. How?

If you read carefully, the article said:
"Some self-proclaimed engine gurus claim too large of an exhaust tube on a car can cause problems; engines need a certain amount of backpressure to run correctly."

That was someone else's claim. Now this is his answer for that claim:
"Although the statement about not running too large of a tube is correct, the assumption about engines needing backpressure is not."

hummm....ok... now refering to my drawing posted in the first page... is my exhaust considered s-flow?

I think I happened to read in NST Car,Bikes and Trucks regarding backpressure.

Assuming that after the exhaust cycle, exhaust exiting the pipe flows in high velocity, creating a vacuum as it leaves the pipe.

But, before the gas fully left, the vacuum effect siphoned the air-gas mixture before the valve fully closed in such rapid movement. Without the necessary pressure to helps the valve close in time, air-gas mixture exits with the exhaust together, resulting in the waste of unburnt air-gas mixture (gas is gasoline, or fuel).

Well, that's what it says and why those big MILO TIN is having ultra high FC, loud rumbling of an asthmatic elephant but no power to fart.

Talking about the MILO TINS right, they don't sound that good either. Compared to my stock 1987 Nissan Sentra's exhaust, it sound's better.

Then you'd have to reset the valve timing, don't you? After that, you'd get the max benefit, right?
I'm not sure, still learning about all the valve timing and stuff so please forgive me.
Those milo tin exhaust slows down the velocity of exhaust gases so therefore there is little to no scavenging.
The vacuum is good so that it could help suck in fuel and air because the intake stroke is one of the dead-stroke, there is no power produced, only drag. Having something to help with that I think is good.

I still believe no backpressure is good.

yes, yours is an S-flow muffler.. a straight flow muffler would be those you see in exhaust shop where the size is not big and you can see through the hole. Basically, all stock cars uses S-flow muffler...

http://auto.howstuffworks.com/muffler3.htm

man.. I'm totally lost with this backpressure thingy lol..

I don't know about Myvis, but for an engine like the 1.8L 4G93 with an autobox which spends 99% of its time at 2500-4000rpm, a good exhaust upgrade that maximises power at those rpms (I don't care about sound) will be a straight flow muffler with an internal diameter of roughly 1.7" (which is more or less the same with the stock piping). The stock piping is actually sufficient but the problem is that there are too many kinks, restricting flow. Change that stock piping to mandrel bent piping of the same 1.7" diameter, and remove the resonators.

The end effect will be a direct flowing exhaust of 1.7" inner diameter all the way from the extractor to the exhaust tip... ie. no increases or decreases in inner diameter (ie. volume) from one end to the opposite end. That should maximise the output of the 1.8L engine between 2500-4000rpm.

i wanna ask if there is any dramactical loss in power if i install 2 exhaust on my new wira se

urm.. do you by means those twin pipe you see on the Myvi's and 350Zs?
If you are looking at that, its just the muffler tip. They still uses one exhaust but the outlet from the exhaust being divided into two and ends with a nice muffler tip. That's all. So, power loss? None.

If your car has twin turbo setup, then you can use 2 exhaust, one for each turbine.. hahahaha.. XD

Well.....on my saga 1.5(auto...) i was using the original muffler(which is s-flow) and i changed it to one of em tembak bulan pipes(got a lil excited... )...the result-revs went up much higher...and i mean that....but gear shifting was a problem...i had to pay with the accelarator pedal for the engine to shift gears....but to get to the point of having to shift gears was never a problem....later on i changed to an s-flow muffler(2-inches)...the engine shifts much better now....or should i say it shifts the way an amt is supposed to shift....but i definately that it takes longer to rev to 4k.....Btw....i'm using an open pod filter where air gets sucked in super fast....

if u wanna look nice like the 350Zs, the right muffler is just for display
Focus all on the left 1 which is the original output

Humm... so ur opinion is free flow with no back pressure is good for automatics?

Yes that is indeed my opinion. A free flowing exhaust with no back pressure is good for any car, automatic or manual.

An engine+auto is no different to the same engine+manual trans. The only difference is the rpms where the driver spends most of their time.

But lotsa ppl are going around saying that auto will lose a lot of torque / power at the lower range of the rpm if using free flow / straight flow exhaust?

Just askin....

I dunno how to explain but in fact it is true. Low end power damn sucky....but once the car climbs above 4000rpm the power can be felt. Auto must always use S-flow mufflers. It is possible to use straight flow but pickup like dead liddat

Yeah I experience it myself, lower rpm region, you get nothing but loud noise....around 3.5K and 4K range then you can feel the torque

Auto car can have a nice sound with some nice exhaust...
i heard it be4... quite nice
all is related to ur wallet la...=.=
"monay monay monay" lolx

I heard auto cars must put like 2 bullets?
Aint that a bit restrictive?

yea, exhaust system for auto cars is a bit tricky.. kenot do this and that..

good exhaust system comes with LOW BACKPRESSURE , HIGH VELOCITY gas flow !!!

Like I said, it is the rpm which is important.

For example,

1L engine @ 3000rpm produces n m3 of exhaust gas & needs 1" exhaust piping (no mufflers etc) to vent the gas out most quickly.

1L @ 4500rpm -> n+1 m3 & needs 1.2" piping.

1L @ 6000rpm -> n+2 m3 & needs 1.4" piping.

So, piping must suit the volume of gas produced at the relevant rpm.

So, what is the "relevant" rpm?

For manuals, that's whatever rpm you want it to be.

For automatics, it's usually between 2000-4000rpm. Rarely anything out of that range for 99% of the time. So, in order to have the best piping for this 1L auto, you'll need something between 1" to 1.2".

So, why do most people think autos need "backpressure" and restrictive exhausts or additional resonators?

Simply put, because they go listen to the exhaust shop and install piping which is too big, for eg. 1.4" which will be fine for high rev 1L manuals but not for autos which don't high rev very much.

What happens when they go back to the exhaust shop complaining about low rev sluggishness? Will they replace the piping with a smaller one? No, because that confirms they are not very good in exhaust tuning and they can't charge you $$ for the additional work. So, they make up a fairy tale that "autos need backpressure" and recommend restrictive exhausts or additional resonators to make the entire system more restrictive. For eg, adding a restrictive muffler to 1.4" piping will make it flow as if it is 1.2" piping. On top of that, they make $$ selling you mufflers and resonators.

So again, "backpressure" ie restriction is NEVER good. You simply need to choose the piping size that flows best for your engine's capacity and rpm range. If 1.2" piping is best for your auto, then make sure your free flow exhaust and resonators also have internal diameters of 1.2".

So, im driving a MyVi automatic 1.3litres. With stock pipes, exhaust manifold, mid box but with a after market in house made high flow S-Flow.
So if i were to change my manifold to a 4-1 header (The only currently offered configuration to date), maintained the stock pipe and mid box but changed to sports exhaust / free flow exhaust at the rear, confirm i won't lose any torque / power at lower / higher rpms?

Please advise.

From my understanding 4-1 extractors will boost ur mid to high range rpm but u will suffer from low to mid range. 4-2-1 improves low to mid but lags torque on the mid to high range compared to 4-1.