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


KieranEG6

KieranEG6

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As the title says.

Is anybody running an exhaust system larger than 2.5" up to like 3" on N/A??

I have been researching exhaust sizes for ages now. 2.5" always seemed like the way to go but from what i have seen on a few forums people with b18, b20 and k20's seem to get better mid range gains with a 70mm systems. Im just worried that with me putting in a b20 or k20 with aims on 230-240 will just a decent 2.5" system do.

Just check out this DC5 dyno comaparison. going from 2.75" (70mm) buddyclub system down to 2.25" (55mm) mugen, destroys the power band across the board. He does eventually swap it out for a 2.5" (60mm) fujitsubo in the sequal video but still never gains back the difference with the 2.75" sysem.

Honda Integra DC5 - Performance Parts Test + Hondata Dyno Tune - ONE - YouTube

Honda Integra DC5 - Performance Parts Test + Hondata Dyno Tune - TWO - YouTube
 
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For a K20 3" seems to work best. For a b18c even in stock form 70mm diameter piping produces the best power I have found.
 
As above, if you want the best gains, a straight through 70mm system will do it - with the right mods, but with it comes noise, plenty of it. Apart from seeing it on the dyno, will you notice the difference between a true 2.5" & a 2.75"...most likely not.
Im running a true 2.5" system, a big silencer and a quieter backbox, 235bhp/160lbft & 93db @6k, compared to most K20's its on the low side, but my manifold is probably not helping, I didnt go 2.75 because of the noise, no regrets, its plenty fast enough.
 
am using 2.5" exhaust on a b16 fully tuned and the said i need 2.75 to get maximum power out of it but am still above 200 whp
 
The only thing is the difficulty in making a 70mm custom system or the cost of buying one new, as they are all way to laud as i allready have decent 2.5" piping already. Finding a used 70mm SK2 mega power RR to chop up and fit better silencers would be perfect.
 
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BuddyClubctr said:
am using 2.5" exhaust on a b16 fully tuned and the said i need 2.75 to get maximum power out of it but am still above 200 whp
Click to expand...

200whp?? from a b16?? thats like around 240hp fly! From a b16?

That must be some setup. Didnt think that was possible N/A.
 
Hi kieran,

I'm using the skunk2 2,75" system on my ek, Saw much better mid/top range gains over the twinloop which was on originally. Pretttty loud I must admit :angry:
 
stock internal cams etc b18cr here
after the header i use 2.75'' (70mm) exhaust it made 208ps
also the same day a mates car (dc2) with stock header and 70mm exhaust made 207ps !!

i would go 3'' (76mm) but i found my current exhaust cheap back then...
a 3'' prop will give 2-3ps max more than the 2.75''...

you won't loose midrage or anything only the opposite
anyway 3'' is the best use big resonators to keep noise down :secret:
 
Cheers guys, just what i thought.

I actualy work in a garage that makes custom exhausts, but they use a pipe bending machine. I cant stand how they crimp the pipes kind of defeating the object. So i think im just going to have to wait for a 70mm exhaust to come up second hand for me to chop up and use the piping off with like 3 silencers.

I need a new exhaust so there is no point in me waisting time building a nice 2.5" system if I know it isn't going to be enough.
 
Why dont you just order some mandrel bends then... if you work in an exhaust place making the rest up wont be hard.. a custom exhaust if you have a decent fabricator will ALWAYS be better than an after market system imo
 
guys as we are in this topic can i ask a question?? having some headears 2.5'' diameter and from there to the back using a 2.75'' or even 3'' pipe and catback will show any gains? or it has to be 3 inch headers also??
 
BuddyClubctr said:
guys as we are in this topic can i ask a question?? having some headears 2.5'' diameter and from there to the back using a 2.75'' or even 3'' pipe and catback will show any gains? or it has to be 3 inch headers also??
Click to expand...

The collector doesnt necesarily need to be 3". As it depends on what design of header/collector you have. Most have a merge type which uses a straight pipe from the joint of the 2 primaries into 1. Where as the toda 421 has a venturi merge type collector where the joint of the 2 primaries is set slightly smaller then the pipe tapers out to a wider diameter before joining the main system. This is the best type to have as it suites going into a larger diameter (optimum) system as the collector is already tapering out speeding up the gasses.

Im not to sure what type the more expensive brands like mugen or spoon have as I have never seen them.

If you do have a straight merge type collector then the best option would be to fit the normal 2.5" joint that tapers into a 3" system instead of a big step.
 
3" systems are available cheap on U.S ebay... I have one for my DC2 it was only £170 to my door, they taper down to 2.5" where it bolts to the cat, I'm having that part cut off and a new 3" flange welded on, I will also do this to my header to make a true full 3" system for my B18C6.

DSCF1171.jpg
 
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if collector is 2,5'' the ideal for flow would be to taper to 3'' or 2.75''

also search tsudo 3'' exhausts on ebay :nice:
 
Ernie said:
3" systems are available cheap on U.S ebay... I have one for my DC2 it was only £170 to my door, they taper down to 2.5" where it bolts to the cat, I'm having that part cut off and a new 3" flange welded on, I will also do this to my header to make a true full 3" system for my B18C6.

DSCF1171.jpg
Click to expand...

That system looks ideal for me to chop up and just use the piping off. As it would cost me around £100 just to buy the mandrel bends before joining them all correctly. What make is that, how long have you had the system, is it lasting well, are the flanges stainless and how thick is the piping?

Sorry about all the questions but you might have found exactly what I need.
:nice:

I should realy search on the US ebay more often.
 
I havnt fitted it yet, saving for a new header.

Quality wise, it looks ok, pipework is quite thin, not sure if flanges are stainless or not, but at that price if it only lasts a year, I'm not worried.
 
just some advice,

be carefull with them cheap 3" systems, i bought one very similar, when i went to fit it, instead of the pipe bending over the lower control arm it bent round it and sat about an inch off the floor and knocked into the fuel tank.

i had to get it chopped and re-welded to get it to fit.

when i spoke to the company saying it was not the same exhaust in the picture and wasnt a 100% perfect fit they got very funny and i had to open a dispute which didnt end in my favour

apart from that the pipe work is very good and suits my turbo very well

the seller on EBAY uses the name INDYRACINGPARTS or SPEEDYRACER

Beware

when i sent him a message the guy was all like "please dont open a dispute, me and you are friends, remember in the begining you said i could trust you"

he started sending me some really f**ked up messages after that saying "i keep messing up, my boss will fire me, he also has a gun"

after that i reported him to ebay, i will trail my emails see if i can find them lol
 
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