i have full 3inch system on my 4agte. its turbo back and got no problems, maybe cuz its turbo so its different story
I have a 2.5" exhaust with only one muffler at the back, which is loud as all urine and Im wanting to quieten it down. Today I went to the muffler shop and the guy there reckons 2.5" is too big for a 4AG because it doesnt have enough back pressure and 2.25" is the maximum size he'd go.
I know that small engines need back pressure but my cams apparently have the inlet and outlet valves open at the same time and I don't know weather this is why there is such a large exhaust.
I also have an almost complete 2" system I could put on.
Does anyone know anything to help me out?
i have full 3inch system on my 4agte. its turbo back and got no problems, maybe cuz its turbo so its different story
I think turbos and big engines are a different story like you said, little NA engines need back pressure to run properly.
yeah dude, defiently on the big side of things, 2.5 would be ideal for a ZE but for NA it is to big, every car runs overlap in their cam timing. even from factory... finsih the 2" system off and see how u go with that, unlessu add more mufflers it wont necesarrly be quiter
Thanks for that.
Also I was wondering if I did have to use the 2.5" exhaust if putting more backpressure in it would work or would that just be stupid.
Thanks for the help.
Back pressure is bad!
End of story.
85' JDM TA63 GTTR sedan - Godlike
89' JDM GZ20 Soarer - 1jz + R154 bus
Originally Posted by joeschmo_57
You could create backpressure by putting more stuff in there, resonators or silencers etc..
Generally 2.25 is optimum for a worked 4age.
depends on flow... 2.5" press bent system can go less than 2" in some of the bends.. people will argue that mandril bends don't make that much of a difference.. i want to hit them in the head with a nice big pressbent system.... if you want a quiet system.. you should shut it up a bit with some mufflers.. like a s bend one.. so the flow physically blows into the side of the muffler.. rather than 'straight through' i'll tell you now though.. there is a certain limit you can go.. power or flow... to shut it up.. you kinda need to block the flow.. but as you said a bit of resistance can help torque..
The 2.5" system on at the moment is mandrel bent and the 2" one is just bent and theres a lot of difference in the bends. I know I'll have to lose a bit of power for the quietness but I think it'll be worth it. I guess I'll just take it to the exhaust guy and see what he says
Small NA engines need a certain ammount of backpressure to work properly. Do some research.
Okay lets do some myth busting... Back pressure is needed for engine to run well= myth!!! (well i think so anyways)
From everything i've studied, back pressure is bad... To create maximum torque at any given rpm, u need to achieve maximum cylinder fill rate... back pressure is detrimental to achieving that... the whole point of having tuned length extractors etc. is to tune the pulsing of the exhaust wave so that a low pressure region will be generated at the exhaust valve when it opens to extract maximum exhaust gas. All the scavenging effect occurs inside the extractors and have not much to do with the rest of the exhaust... The only basis for exhaust too big is not the back pressure, but the increased cooling surface as well as the volume of exhaust to push... technically SOMETIMES in SOME applications it is possible to flow better with a smaller exhaust but thats in RARE instances!!!
I'm simplifying a lot of stuff here and not everything is quite true but thats the rough idea... with good tuning... u want to MINIMIZE back pressure to MAXIMIZE exhaust flow to produce MAXIMUM torque...
2.5" too big... i dont think so... TODA extractors measure 60mm at the collector which is bigger than 2.25" and closer to 2.5".... it would be stupid if u fitted a exhaust smaller than the collector...
Noise problem... well there's not a whole lot u can do except for adding more mufflers... noise cancelation is a difficult science and just because one muffler works well on one car doesnt mean it'll work well on another... mufflers and resonators target different frequencys and usually a combination will work better... but from my personal experimentations... 4ages are just a f***ing loud engine and theres f*** all u can do unless u use really restrictive mufflers... restricting gas flow is the easiest way to reduce noise....
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