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

[King Sir]

^^^^Thats what i was gonna do haha 2.5 from the mani back matched with the mani. I get what your sayin though you mean the inside of the pipe should be 2.5 and then the outside whatever

 

[JDM_DAVE]

imo yes.. but it does depend on your set up.. 2.5 internal may be to big for some engines.. so i always go off what the internal diameter is of the outlet pipe of the manifold or collector

 

[King Sir]

imo yes.. but it does depend on your set up.. 2.5 internal may be to big for some engines.. so i always go off what the internal diameter is of the outlet pipe of the manifold or collector

Ok and lets say its ur car for a minute and the mani is 2.5 so you make a pipe to match that i know the internal diamater is probably less but if you matched that as closely as possible. Would you put baffles (silencers) into it and if so 1 would do would it or would you leave them out?

 

[JDM_DAVE]

no i wouldn't use a silencer... i would have the same internal size pipe all the way through from the manifold (internal) mated to a Mugen twin loop. And believe it or not its not loud.. sound awesome.

 

[LoganK]

If your serious about going on track get a middle box (silencer) and a back box. It will NOT effect performance.

If your just concerned about noise then you will never be able to go on track and the novelty will eventually wear off. No boxes and a straight pipe is fun for a couple of month, then you get pulled by police constant, hate life, hate your car and end up getting a new exhaust with what people said to you to do in the first place.

I speak from experience as I had a straight pipe for a while and #becauseracecar is not an excuse to have an obscenely loud car. Now I am building my car properly for track and have a proper exhaust that isn't overly loud. A straight pipe just gives everyone building a decent trackcar/racecar a bad name

 

[King Sir]

If your serious about going on track get a middle box (silencer) and a back box. It will NOT effect performance.

If your just concerned about noise then you will never be able to go on track and the novelty will eventually wear off. No boxes and a straight pipe is fun for a couple of month, then you get pulled by police constant, hate life, hate your car and end up getting a new exhaust with what people said to you to do in the first place.

I speak from experience as I had a straight pipe for a while and #becauseracecar is not an excuse to have an obscenely loud car. Now I am building my car properly for track and have a proper exhaust that isn't overly loud. A straight pipe just gives everyone building a decent trackcar/racecar a bad name

I have a backbox ordered for the car that has a remote controled silencer built into i tso i can turn off the noise if i want so would be perfect for track days or motorway driving.

Thats why i want to know should i get a Middle box? Sorry i probably should have mentioned that at the start.

Also thanks for all the ideas sugestions and opinions so far lads all taken on board

 

[King Sir]

no i wouldn't use a silencer... i would have the same internal size pipe all the way through from the manifold (internal) mated to a Mugen twin loop. And believe it or not its not loud.. sound awesome.

Oh ok thanks dude i hate twinloops though dont like the sound at all and they are very restrictive

 

[jesse888]

This silencer you speak of, it's not got a butterfly valve in the pipework has it?
If so you might find that it completely sucks to drive and on track you may damage the cylinder head as the gases are backing up too much, everything gets real hot.
Unless it's more of a diverter valve and makes the exhaust take a different route?

 

[jesse888]

Or, you could get a repackable silencer?
So less packing = more noise,
Want to go on track? Pack some more silencer wool in there.

 

[waff]

Oifovo is right, for most track days noise regulations tend to be really strict. As soon as the event is more race regulated, these levels can be a bit higher. This is what usually happens. To the point where some FIA events tend to accept really loud exhaust noise levels (not always).

I have friends here in Spain and in France running straight pipes and exhausts such as Buddy Club Spec II, and they can't enter to any track day event without "silencing" these exhaust systems.

 

[waff]

I think this is more important in the manifold than the "catback" section of exhaust.
My understanding is the same as Oifovo. Wider diameter moves torque upwards abit. Unless your engine makes too much power for the particular bore size you have and is being choked by it.

Yes, normally the most important part is the design of the manifold and the next inches of exhaust pipe after this specific manifold. Usually the "real race engineered" exhaust pipes are quite short compared to road exhausts (as an example, look at race cars with short length side exhausts). So the exhaust pipe is a shorter peice than the one you see on "street performance exhausts".
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.

 

[King Sir]

This silencer you speak of, it's not got a butterfly valve in the pipework has it?
If so you might find that it completely sucks to drive and on track you may damage the cylinder head as the gases are backing up too much, everything gets real hot.
Unless it's more of a diverter valve and makes the exhaust take a different route?

No dont worrie i dont like the ones that close completely this diverts the gases through a seperate route in the backbox it self and makes it actually quieter than stock So il be grand that way.

I can also open it slightly to let some of the noise out or get to a quiet bit of the track and open her up haha

 

[JDM_DAVE]

Oh ok thanks dude i hate twinloops though dont like the sound at all and they are very restrictive

yes they are, but what you would normally loose with the full twin loop system you will gain back by having matched piping to your collector and having no boxes.. this system sounds amazing and you should still pass the noise control at the track. its been a few years since I visited a track but a few friends of mine have done this set up and passed for the track. I don't know, on the other hand what the criteria for passing noise control is today but back then Im sure it had to be under 94db at 4,000 rpm. It came up at 88db everytime.

 

[jesse888]

Yes, normally the most important part is the design of the manifold and the next inches of exhaust pipe after this specific manifold. Usually the "real race engineered" exhaust pipes are quite short compared to road exhausts (as an example, look at race cars with short length side exhausts). So the exhaust pipe is a shorter peice than the one you see on "street performance exhausts".
As a resume, just find the correct outer diameter for the manifold of 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.

Another advantage to routing the exhaust out the side is the aerodynamic benifit of not having a pipe in the underside airflow.

 

[JDM_DAVE]

Yes, normally the most important part is the design of the manifold and the next inches of exhaust pipe after this specific manifold. Usually the "real race engineered" exhaust pipes are quite short compared to road exhausts (as an example, look at race cars with short length side exhausts). So the exhaust pipe is a shorter peice than the one you see on "street performance exhausts".
As a resume, just find the correct outer diameter for the manifold of 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.

(bold underlined) My Question.....wouldn't this work better for turbo cars? is it necessary to route the exhaust this way for N/A engine'd cars.. unless they had big engines I don't understand why it would benefit a b16 or b18. could you explain in more detail? I am genuinely interested, this could be a new route I could take

 

[jesse888]

I wouldn't expect a huge gain over a full length exhaust in terms of the power the engine produces. I'd say less than like 3%
As I said it's more for an aerodynamic advantage IMO
And weight of course

 

[JDM_DAVE]

I wouldn't expect a huge gain over a full length exhaust in terms of the power the engine produces. I'd say less than like 3%
As I said it's more for an aerodynamic advantage IMO
And weight of course

+1 as a opinion.. I still think that the best way is to tune the velocity of the exhaust gases and the velocity of the intake air speed..

 

[waff]

Well, the aerodynamic advantage is not always the 1st reason for short lenght exhaust designs. The race teams or companies who study and use these setups, to design exhaust the 1st rule they keep in mind is the power output over the aerodynamic (it's more in F1 where they match car aero and exhaust output to take most of the two).
The teams/companies who have real experienced engineers and experts on this "balck magic" which is the secrets of real race exhausts, usually use the short exhaust designs taking as priority point the engine power. In some race categories or cases, it's true they combine "aerodynamics" with "engine power given exhaust design", so one of these two points can achieve a superior level of priority over the other.

The type of cars which use these short exhausts, also use front splitters, under-tray panels and rear diffusers, so the underside flow is not a big issue when they use rear exit exhausts. In some cases at the rear diffuser there is a combination of low pressures (exiting the under panels of the race car) finding the higher pressures at the rear of the car. So this is not a real issue, and can greatly differ from case to case.
Even the exhausts on the side will find flow restrictions given the high pressures sometimes found on the side skirts, etc. But this is not an easy "science", it has a lot of variables...

On the performance side (aside of the aero point), why short exhausts?
You know, in resume, short pipe means faster travel of the pressure and sound waves (backpressure comes earlier to the valves, etc.). This equals to fast pulsing, which helps at higher revolution ranges. So it's not good for the lower range of revolutions, or for low maximum revolution engines.

In terms of Honda race cars, it could be seen in some early Group A cars in Japan. Then later on the JTC or JTCC series they kept the short design exhausts, but rather than exiting on the side, these had the exit at the underside... nowaydays it's nearly impossible to see some Honda race car with sided exhaust.
Also some old race Toyota had these type of exhausts there in Japan (some N2 series AE86...).

As exhaust science is constantly changing, and they find things they didn't know before...

Keep your exhaust on the long side, to the rear better

 

[jesse888]

Seen a side exit on afew of last years btcc cars. Exiting before the rear wheel.
Thy where noticeably louder than the rest of the field, perhaps because the exhaust is pointing at you?

 

[waff]

Yes, as Jesse says, don't expect huge gains on a good and properly studied side exhaust. Typically the given gains are very little, well suited for a race environment.
All these modifications tend to move/reduce/extend the powerband... and the experts will determine if they need the powerband "here" or "there" better.

Yes JDM_DAVE, it is also used on high output turbo cars, but again is a matter of studying as each case is different. Some will need longer exhausts.
I don't really know if a short exhaust would add any benefit to a B16/B18 setup. Maybe on a really hardcore NA one. But it would need a proper study.

Anyway, if I was you, I wouldn't use a short pipe on a street Civic. Not only for the sound of it (these generally give deeper and more screamer sounds given the short walk of the pressure/sound waves), but also because it could affect badly your bottom end torque and power.