Backpressure is it a mith or should i get one silencer in my exhaust?


Yes Jesse, this is also a good point of view. It's part of the "sound game", combined with the speed of the pulses, etc.

Also you are right about aerodynamics on side exhausts, not always, but sometimes if they find they will combine aero with exhaust design for engine performance, depending on the angle exiting the side exhaust it can help a lot, over the typical rear exhaust.
 
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waff said:
As a resume, just find the correct outer diameter of the manifold for your specific engine setup (for maximum output), and make the exhaust pipe to the same diameter.

We could speak of exhaust tapered sections and anti reversion too, but this is not necessary by now.
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So for my set up you recommend making the exhaust pipe as big as the internal diamater of the mani is it?

So my mani is the toda rep which is 2.5 but the internal pipeing might be smaller il messure it tmr.

But lets say for example its 2.4 or 2.35 would that be what size you would recomend me gettin the exhaust made up too.

Or have i misunderstood you? :D
 
Yes, match internal to internal.. the external should match automatically... should!!!!!
 
Exactly, you understood it correctly. As JDM_DAVE says, match internal with internal.

If the outside diameter of your manifold is 2.5" (about 63mm), it is really possible the internal diameter is around 2.37" (about 60mm). It is not a bad diameter for a B16B if you use some silencer or some type of catalytic converter. It will breath better at a higher revolution band (I mean for this diameter, not because of the silencer/catalytic converter).

I think these 1.6 litre engines in OEM form, for street use performe better with 2.25" (57mm) inside diameter exhausts, so the whole powerband is slightly better (with a bit less top end). Anyway I prefer the 2.37" (60mm) inside diameter mark for them ;) (higher revolution use...:secret::naughty:)

If the exhaust tube inside diameter is smaller than the one for the manifold, the low pressure waves could slightly "shut" the scavenging process...
 
Oh, I just noticed now your route is a B18C R.
2.37" (60mm) inside diameter is good! :clap: Even in some case one step further is good as well.
 
Back pressure is NOT the same as the scavenging effect/pulse tuning in an exhaust! It even contradicts; how would an exhaust be able to get it's own gasses out with more pressure holding back the gasses? Backpressure is bad so you want as little as possible. Some people therefor choose a very big exhaust. But this is only half the story. You want your exhaust gas velocity to be as high as possible to maximize the scavenging effect. Too big an exhaust will cause exhaust gas velocity to decrease = performance loss. So in the end you want the diameter that will give you maximum exhaust gas speed (which means it shouldn't be too big in diameter) but also gives you as little backpressure as possible (not too small in diameter).
 
_JT said:
Back pressure is NOT the same as the scavenging effect/pulse tuning in an exhaust! It even contradicts; how would an exhaust be able to get it's own gasses out with more pressure holding back the gasses? Backpressure is bad so you want as little as possible. Some people therefor choose a very big exhaust. But this is only half the story. You want your exhaust gas velocity to be as high as possible to maximize the scavenging effect. Too big an exhaust will cause exhaust gas velocity to decrease = performance loss. So in the end you want the diameter that will give you maximum exhaust gas speed (which means it shouldn't be too big in diameter) but also gives you as little backpressure as possible (not too small in diameter).
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Was thinking this.
Simpler way to say it would be that flow and velocity(or gas speed) aren't the same thing.
3" will have higher flow but lower velocity(net loss on a b series usually)
2" will have high velocity but low flow because of small diameter
 
Right i understand what ye are saying so basically what i want by the sounds of it would be a 2.75 exhaust no??

One of the lads had a 2.75 kakimoto on his b18cr with basic bolt ons and he made sick power.

But that was a ridiculously healthy engine.

What do ye recommend or would matching the internal diameter still be best?
 
Based on what I've read: stock to moderately tuned B16/B18" 2,5". Take into account that a 2,5" collector on the header is also very important! This was stock on the stock 98 spec JDM s/s header. For a heavily tuned engine I think 2,75" would be wise.
 
A 2.75 external diameter is better for the k20, but would still be a good on a b18c-r.. imo tho I think for street use 2.75 on a b18 would be the very max before you start complicating things. the buddyclub pro spec for the dc5 I had was 2.75 external.. made hell of a difference over a spoon or fujitsubo system. Iv run a pro spec on a dc2 and can confirm it works very very well, one of my top choices for off the self systems.
 
JDM_DAVE said:
A 2.75 external diameter is better for the k20, but would still be a good on a b18c-r.. imo tho I think for street use 2.75 on a b18 would be the very max before you start complicating things. the buddyclub pro spec for the dc5 I had was 2.75 external.. made hell of a difference over a spoon or fujitsubo system. Iv run a pro spec on a dc2 and can confirm it works very very well, one of my top choices for off the self systems.
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Right forogt to add my b18cr has ek9 pistons and has been bored and honed so should be fairly high compression so would 2.5 or 2.75 be best? Tbh id prefer 2.5 cos 2.75 is ridiculously loud but more power is good :nono::wtf: If i was getting 2.75 there would definatly be baffles put in (Middle box)
 
id run a 2.75 external exhaust if thats the case, but it depends on what u want, matching the internal size of the exhaust with the collector will speed the velocity up but may get choked top end if your running higher compression. Id go with the 2.75 / 2.70 external exhaust that way the internal size should be around 2.5 or a little under, that would be good for all round power and should pull towards top end
 
I think we may be looking way too far into it, considering its a road driven civic and not a race special that needs every HP it can muster.
 
make a custom exhaust that is as straight as possible
straight trough design resonators wont affect power
they work only as sound cancelers but they add some weight in the system.
consider yor hi comp set up i would go with a 2.75'' - 70mm exhaust using a hi flow cat and 2 big resonators.
Also a 2.75'' - 70mm exhaust will let you more room for future engine upgrades.
 
King, make it simple. As I said earlier on this thread, go with 2.5" internal diameter for your engine. It's more than enough, and you just wouldn't feel the difference with sligthly different setups (sligthly bigger ones).
 
_JT said:
Back pressure is NOT the same as the scavenging effect/pulse tuning in an exhaust! It even contradicts; how would an exhaust be able to get it's own gasses out with more pressure holding back the gasses? Backpressure is bad so you want as little as possible. Some people therefor choose a very big exhaust. But this is only half the story. You want your exhaust gas velocity to be as high as possible to maximize the scavenging effect. Too big an exhaust will cause exhaust gas velocity to decrease = performance loss. So in the end you want the diameter that will give you maximum exhaust gas speed (which means it shouldn't be too big in diameter) but also gives you as little backpressure as possible (not too small in diameter).
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Don't know if this is for me, but if it is, I never said backpressure is the same as pulse and scavenging. I just was stating the two last theories alone, without touching the backpressure :))

Even it's not the same, all these effects go "hand in hand" :blinx:. Backpressure affects different without the pulses and pressure waves, and vice versa.
 
jesse888 said:
I think we may be looking way too far into it, considering its a road driven civic and not a race special that needs every HP it can muster.
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You dont understand i drive my car within an inch of its life......

I let it warm up fully drive to my destination and then on the way back its pushed to the edge of its limit

So id notice every extra hp :run:

Ha i want everything i can get out of it ;)

@waff Your dead right il do that thanks :D
 
abunai888 said:
make a custom exhaust that is as straight as possible
straight trough design resonators wont affect power
they work only as sound cancelers but they add some weight in the system.
consider yor hi comp set up i would go with a 2.75'' - 70mm exhaust using a hi flow cat and 2 big resonators.
Also a 2.75'' - 70mm exhaust will let you more room for future engine upgrades.
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Thanks man but i have no future mods planned this will be it any other mods will be to interior or exterior
 
King Sir said:
You dont understand i drive my car within an inch of its life......

I let it warm up fully drive to my destination and then on the way back its pushed to the edge of its limit

So id notice every extra hp :run:

Ha i want everything i can get out of it ;)

@waff Your dead right il do that thanks :D
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Is this a Joke ^^ You can't be serious lol

I'm all for a bit of sporting on the road when its reasonably safe to do so and there is no other cars about but "pushing a car to its limit and within an inch of its life" on the road with end up killing you or someone else if you don't loose the licence before then

If you like speed then you should build a dedicated track car that you can use properly on a circuit and push the car far more than you could on the road, or build a fast road/track car for the same purpose on track. If you want a really fast car for the track then but a GTR skyline or an EVO for example and turn the boost up, n/a Hondas are quick for what they are in a straight line but they are not fast cars compared to big engine and turbo'd cars
 
SPek9 said:
Is this a Joke ^^ You can't be serious lol

I'm all for a bit of sporting on the road when its reasonably safe to do so and there is no other cars about but "pushing a car to its limit and within an inch of its life" on the road with end up killing you or someone else if you don't loose the licence before then

If you like speed then you should build a dedicated track car that you can use properly on a circuit and push the car far more than you could on the road, or build a fast road/track car for the same purpose on track. If you want a really fast car for the track then but a GTR skyline or an EVO for example and turn the boost up, n/a Hondas are quick for what they are in a straight line but they are not fast cars compared to big engine and turbo'd cars
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Thats very true ya must build a track car. Ah i only drive backroads with no houses and in the middle of the night worse thing thats gonna happen is il do myself or an animal in.

I know it sounds stupid but everyone on here has done it somestage.

But you are completely right about saving it for the track way safer :nice:

And i would advise against anyone using backroads at all :lol:
 
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