Anyone using 2.5"+ /3" N/A exhaust system???


689R said:
I pretty much take American WHP to equal our BHP, it makes the figures much more accurate haaa.


Im going to use 3" on my EK once its Kswapped, Iv read loads about this and it seems pretty straight cut. Alex's K20 EK made more power both midrange and top end with a 3" over his previous mugen twinloop.

TDI North also used and suggest 3" exhausts on K20 vehicle and have got one on their K20 EG.
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Yea i was thinking that. As i have seen plenty of builds with higher spec only reaching around 225fly hp.

Looks like its going to have to be 3" for me then seing as a K20 is on the cards for me or at the least a well built b20, may aswell do it right and only do it once.

But will point out the mugen twin loop on EK's are like only 2" at the back box so are prity poo for performance flow. Even the DC2 one is only 2.3".

I just hope i can make a quiet 3" system :nerv:
 
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KieranEG6 said:
218 whp????

So thats like 260hp at the fly. Must be some mega motor. Are you sure?
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it doesnt always scale that way. 218whp can be around 230-240 true bhp. All dynos aint scaled the same.
 
You guys don't really need 3.0" if your under 2000cc. Even if you gain another 2-3 peak power, you loose a shitload of power from idle till 7000rpm. What this gives you is a dramatic power surge when the exhuast gases start moving. Its epic for driving on the redline, but the bad thing is, car is super sluggish on the street during normal driving. And if your gearing and redline doesnt give you the ideal rpm after changing gears(for example above 7000rpm), your actually going slower.

If your car is for the track/drags, go for it. But for the street. Lots of noise doesnt equate to quick acceleration. Just a different and more realistic view here as most of us here use our cars as a daily.
 
jugbugz said:
You guys don't really need 3.0" if your under 2000cc. Even if you gain another 2-3 peak power, you loose a shitload of power from idle till 7000rpm. What this gives you is a dramatic power surge when the exhuast gases start moving. Its epic for driving on the redline, but the bad thing is, car is super sluggish on the street during normal driving. And if your gearing and redline doesnt give you the ideal rpm after changing gears(for example above 7000rpm), your actually going slower.

If your car is for the track/drags, go for it. But for the street. Lots of noise doesnt equate to quick acceleration. Just a different and more realistic view here as most of us here use our cars as a daily.
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This isnt true, dozens of threads on HondTech showing gains all through the rev range...

A guy posted a graph of a stock b16a with a 3" sytem bolted to it and it still gained power and torque all over.

All the info is out there.
 
Full 2.5" system here on a high spec'd B18C, slip jointed so no bottlenecks, single rear race silencer and the header is 4-1 true merge with a 2.5" downpipe

Certainly seems to work well, powerband is very linear and basically a straight line, holds power right through to 9.5k

Would it have worked better with a 3" system? I dunno, but certainly pleased with it as it is

As mentioned you will be hard pushed to get the noise down on a 3" system without adding huge resonators, i've only got 1 rear silencer and would easy pass scrutineering for track days ;)
 
Noise is the big issue with 3", as you say larger and more boxes/resonators is the answer, but the added weight of this, kinda eats into your power gains...
 
I didn't realise Knockhill actually stood by there sound limit. What I heard they don't seem to care lol, shame none/not many are like that in England
 
jugbugz said:
You guys don't really need 3.0" if your under 2000cc. Even if you gain another 2-3 peak power, you loose a shitload of power from idle till 7000rpm. What this gives you is a dramatic power surge when the exhuast gases start moving. Its epic for driving on the redline, but the bad thing is, car is super sluggish on the street during normal driving. And if your gearing and redline doesnt give you the ideal rpm after changing gears(for example above 7000rpm), your actually going slower.

If your car is for the track/drags, go for it. But for the street. Lots of noise doesnt equate to quick acceleration. Just a different and more realistic view here as most of us here use our cars as a daily.
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Thats it though, I will be going 2L in the future, either a highly built B20 or K20 swap. Will be aiming for around 235hp minimum but with bags of torque. The car is off the road for at least 2-3 years so I have plenty of time to do it all but want to do it right so when it is back in use I wont need to touch it.

The thing is my current 60mm(2.4in) system needs the resornators replacing as their prity much hollow now. So seeing as I was going to cut out the old silencers and fit new ones why not just build a Full 3" system for a bit extra. Then i will have an exhaust that will be perfect whatever i choose B20, K20 or even turbo.

As for noise I was planing on making it a 3 box system with 2 decent sized resornators in the center section and the bigest silecer box i can fit as a back box so it should be prity quiet. If it comes out to still be to loud for road or some tracks I can always addapt my 60mm DC2 Mugen twin loop back box to fit on the system or make a silencer bung. I know it sort of defeats the object but it would only be a temp fix to be quieter when needed. We have a Db meeter at my work anyway so i should be able to test how loud it ends up as.

In total it shouldn't cost me more than £400 in parts and im making it myself. So its not gona cost that much in comparison of spending around £5000-£7000 on an engine that it will be attached to.

As for the extra weight of the added 2 center silencers thats not really going to make that much differenc. For one its only going to be a max of around 10kg extra with both so similar to your spare wheel and jack. Secondly its not like its on the roof, its attached to the lowest central part of the car possible so won't have much affect on center of gravity. Yes 10kg is still more weight but in a place with the least influence on the car. As for power to weight, 10kg aproximatly equates to around 2hp less per ton but having the 3" system should give plenty more gains than that over a 2.5" system.
 
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Wazer said:
I didn't realise Knockhill actually stood by there sound limit. What I heard they don't seem to care lol, shame none/not many are like that in England
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they don't, however i plan on doing trackdays on the other side of the border this year :)
 
a lot of people suggest 20''- 22'' resonators to keep noise levels down.

i believe its gonna be lighter than a mugen twinloop anyway...

when N/A every hp counts and 3'' will make power everywhere in the powerband
bigger engines will see bigger gains as always.
 
abunai888 said:
a lot of people suggest 20''- 22'' resonators to keep noise levels down.

i believe its gonna be lighter than a mugen twinloop anyway...

when N/A every hp counts and 3'' will make power everywhere in the powerband
bigger engines will see bigger gains as always.
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I was planning 2, 5"x18" silencers in the center section then a fatter 6"x14" for the back box. Cant really fit much more length on the back box i dont think without useing a skinyer box to fit in between the sus arm and chassis. But dont really fancy trying that.
 
There are quotes on the internet to back up gains all through the rpms but what about part throttle i.e daily driving. Are there gains to partial throttle for going to 3"??? What time worried about is losing a lot of part throttle response if goong to the bigger 3" diameter.
 
It is mentioned in the threads I posted I think.... Throttle response is dealt with on the intake side of the engine not exhaust, or so I've read.

TBH I dont see the issue with part throttle, if you wanna go quicker you are in WOT...?
 
abunai888 said:
a lot of people suggest 20''- 22'' resonators to keep noise levels down.

i believe its gonna be lighter than a mugen twinloop anyway...

when N/A every hp counts and 3'' will make power everywhere in the powerband
bigger engines will see bigger gains as always.
Click to expand...

More info on this please? is this just a type of silencer box?

3" is ideally what I want on my car, but I dont want it to be super load, im definately fed up with super loud police attractors. I wanna go fast stealth.
 
689R said:
More info on this please? is this just a type of silencer box?

3" is ideally what I want on my car, but I dont want it to be super load, im definately fed up with super loud police attractors. I wanna go fast stealth.
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x2
im in the same boat....
 
I imagine 22" resonators would be custom made. You can buy 18" ones from Vibrant
 
If your after a quiet 3" system then you'll have to go custom with a large center resonator.
Mine's not loud, but it's not quiet either.
 
To be honest I don't think one dig long resornator is the answer. I'm prity sure the reason they only make 18" max is because anything longer would slow down the gas to much from having to pass through so much perforated tube in one go. There is enough room to fit 2x 18" ones that equates to 36" of silencing but at two points which should keep the gas velocity higher. Even with the k swap manifolds deleting the cat there should still be just enough space, if not then you would only have to opt fir a 16" one after the manifold which still comes to 34" of silencing. So should be plenty.

I hope :nerv:

But when you actualy add up how much sillencing you will have over the usual aftermarket systems which only have 1 center box usualy only around 14"-16" and only 4" wide. Having doulble that with at least 5" wide box's should be plenty. I have a feeling the 3" exit will still give a fair drone but wont be that bad.
 
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