4age new exhaust

[RickGT]

just put new exhaust on my fx, its 2 1/4" inch with 25" long coby with 2.5" muffler at the back, it feels quite laggy up till 3,000rmp then sorta kicks into life after that, anyone noe why??
thanks

[Truenotch]

4ages should have a 2 inch cause 2 1/4 could be making it too free flowing.

Should be alright though.

[Brolli]

Aren't most 4age engines standard 2.25' piping anyway ?

[RickGT]

will another little coby help to keep the flow down?

[Truenotch]

I dunno eh man,

haha put a cat in it to restrict some flow.

[CozmoNz]

Aren't most 4age engines standard 2.25' piping anyway ?

more 2", but by the time you replace your exhaust, its probbaly falling to peices anyway, plus, its an excuse to make the neighbours wake up when you get home at 3 in the morning

will another little coby help to keep the flow down?

probbaly wont drop the flow, will just make it dronier.

if you wanted low down torque, shouldnt have got a 4age... think about it, engines need back pressure... go unbolt your exhaust manifold from your exhaust piping itself to see what im talking about.

now, a bigger exhaust removes some back pressure when there is less of the exhaust itself being filled, or used, however in the high end there is far less restriction, again, the bigger piping.

Pick one, high end or low end, cant have both in a 1600 high revving, not like you had any down low in the first place.

If you want low end + high end, go get a 1uz, then turbo it

[RickGT]

hey yea thanks for that, kinda sumed it up for me, but i disagree bout the low torque, it would take off out of roundabouts pretty quick when i put my foot down in 2nd gear, but yea i noe its not the gruntiest thing around but it satisfies me, small an quick. is the 2 1/4 gona do anything to fuel consumption?

[RedMist]

... think about it, engines need back pressure... go unbolt your exhaust manifold from your exhaust piping itself to see what im talking about.

now, a bigger exhaust removes some back pressure when there is less of the exhaust itself being filled, or used, however in the high end there is far less restriction, again, the bigger piping.

Pick one, high end or low end, cant have both in a 1600 high revving, not like you had any down low in the first place.


God I hate statements like this.

Engines do NOT like or need backpressure. Think about it, an engine is in its simplist form a pump, restrict the exhaust of the pump and the engine isnt as efficient and doesnt produce as much HP... throughout the RPM range.
Reduce the backpressure, time the engine accordingly and SNAP CRACKLE POP, instant HP throughout the rev range.
In stating this engines are however factory tuned to accept factory backpressure. To get the best out of a change in restriction both cam and ign timing should be altered. I'm not saying that you will loose HP by reducing restrictions, just that you won't get all the potential HP gained by reducting restrictions until you change your timing.

Two things to note. Firstly are you sure you just havent gained a big kick at 3k RPM? and not lost anything below? Butt dynos are incredibly accurate. 3k RPM, your lucky, my race engine feels like a fast 4age until 5.5k, then it just goes all silly.
Secondly, just in case this comes up.... there is a limit as to how large an exhaust size you can use. Why because at a certain point as you go larger you LOOSE flow!! Its nothing to do with the famed "lack of backpressure", because by going larger you actually increase backpressure!! 2.25inch on a stock or slightly modified engine should be fine. I run a 2.5 inch on a very unrestricted exhaust (no noise regs in off road racing), and a very high spec engine.

General rule of thumb, if it sounds like rice ITS CRAP. Not much scientific resoning, I just hate rice! Oh and if you have a loud exhaust on an auto car. I have a baseball bat, with a slight indentation in the shape of a head that wants to meet you.

Yes, it has everything to do with Helmholtz.