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By Lewisgame
#3677981
+1 for a poor map. The idea of variable valve timing is for the torque to peak early and stay consistent at that point over a rev range. As the civic has 2 can profiles this will happen twice.

Back pressure isn't a myth. It's basic physics. The idea of changing the exhaust and header is for more free flowing and adjusting the exhaust resonance.
On a 4 stroke, as the exhaust pressure is going towards the engine, you want it at the same time the exhaust valve is closed. Obviously this is impossible over the whole rev range, but achievable at a certain rev range. One size exhaust might get you a low rev peak power, another might make high rev peak power. The diameter, shape and length of both the header and exhaust system all play effect in the exhaust resonance.
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By gearinator
#3678075
Lewisgame wrote:+1 for a poor map. The idea of variable valve timing is for the torque to peak early and stay consistent at that point over a rev range. As the civic has 2 can profiles this will happen twice.

Back pressure isn't a myth. It's basic physics. The idea of changing the exhaust and header is for more free flowing and adjusting the exhaust resonance.
On a 4 stroke, as the exhaust pressure is going towards the engine, you want it at the same time the exhaust valve is closed. Obviously this is impossible over the whole rev range, but achievable at a certain rev range. One size exhaust might get you a low rev peak power, another might make high rev peak power. The diameter, shape and length of both the header and exhaust system all play effect in the exhaust resonance.
[smilie=karls_thumb.gif]
User avatar
By Ernie96
#3678080
Lewisgame wrote:+1 for a poor map. The idea of variable valve timing is for the torque to peak early and stay consistent at that point over a rev range. As the civic has 2 can profiles this will happen twice.

Back pressure isn't a myth. It's basic physics. The idea of changing the exhaust and header is for more free flowing and adjusting the exhaust resonance.
On a 4 stroke, as the exhaust pressure is going towards the engine, you want it at the same time the exhaust valve is closed. Obviously this is impossible over the whole rev range, but achievable at a certain rev range. One size exhaust might get you a low rev peak power, another might make high rev peak power. The diameter, shape and length of both the header and exhaust system all play effect in the exhaust resonance.
Why do drag cars run no exhaust at all then?

I'm not saying your wrong, I'd just like to know....
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By Ernie96
#3678115
Lewisgame wrote:They do run an exhaust... Well each cylinder has it's own pipe. The engine builders would of spent a lot of time changing the length and diameter of that pipe to get the best results.
I would call that open header myself... its hardly an exhaust... [smilie=karls_thumb.gif]

Either way 3" is the way to go on n/a K20...
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By sammo303
#3678749
pulpmelon_r wrote:Internet engine builders and their back pressure, still spouting the same old.

Guess what the 'exhaust' looks like on a 9 second NASP Honda:

Image
That'll be built for decent torque throughout the rev range yeah? :thumbup:
User avatar
By pulpmelon_r
#3678777
sammo303 wrote:
pulpmelon_r wrote:Internet engine builders and their back pressure, still spouting the same old.

Guess what the 'exhaust' looks like on a 9 second NASP Honda:

Image
That'll be built for decent torque throughout the rev range yeah? :thumbup:
Give a fuck, you launch this car at 6000RPM, rev it out to 10500 four times then switch it off.
User avatar
By ::Adds::
#3678933
pulpmelon_r wrote:
sammo303 wrote:
pulpmelon_r wrote:Internet engine builders and their back pressure, still spouting the same old.

Guess what the 'exhaust' looks like on a 9 second NASP Honda:

Image
That'll be built for decent torque throughout the rev range yeah? :thumbup:
Give a fuck, you launch this car at 6000RPM, rev it out to 10500 four times then switch it off.
Above needs to watch check out proper US drag civics and some 4bangerproduction/iamtaiboogie vids... These boys build some mean cars
User avatar
By ::Adds::
#3678965
Liam Type-R wrote:
mickdj wrote:Image

Like this

Im away on my phone can someone sort my pic out thanks
Image

Was that it?
Looks familiar, wasn't this a video of some sort
User avatar
By mickdj
#3680022
Top gear India special clarkson decided to do away with his exhaust as i think he kept catching it and had about a foot of exhaust sticking out of the bonnet for each cylinder, but i was struggling to find a pic or video clip, i thought the one i pasted was it, but that one was when he decided it was too loud and stuck a back box on the end off each pipe.
User avatar
By ::Adds::
#3680130
mickdj wrote:Top gear India special clarkson decided to do away with his exhaust as i think he kept catching it and had about a foot of exhaust sticking out of the bonnet for each cylinder, but i was struggling to find a pic or video clip, i thought the one i pasted was it, but that one was when he decided it was too loud and stuck a back box on the end off each pipe.
That's the one... Rather tasteful
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By Lewisgame
#3680652
Just to be clear. I've never said that a 2.5 inch is better over a 3 inch system. Just stated the fact that back pressure is physics. Whether you've got an open header for drag, or a complete system for the road, size, shape and length will make a difference.
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