General exhaust questions thread

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guska

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I thought I would start this thread for people to ask any questions they mnay have about any aspect of a car's exhaust system that they don't understand, or to ask for advice on different aspects of exhaust systems.

Please try to keep things polite.

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I'll start by asking which of these ECVs should I use for a 3.5" turbo back exhaust on my RB20det powered HR31 GTS-x? Keeping in mind it is purely for track purposes, and will be just a pipe running from the turbo to the rear, with no cat or mufflers of any sort, just the ECV.

http://www.nengun.com/apexi/exhaust-control-valve

I am mainly after sizing reccomendations, as 3.5" is approx 89mm, and I don't know whether I need to go bigger than the pipe, or smaller. Thanks in advance.
 
What size is your pipe? Can't you get it in the same size?

Why not do this:
http://www.youtube.com/watch?v=K7jGYnhbQQU
instead?

Kinda expensive, though.

If you're doing this for track work, some tracks may not like the sound of a totally uncorked system... and if you're uncorking only for trackwork, you might even want to consider just having a quick-release set-up for your muffler... would be cheaper and less compromised than a regular cut-off valve.
 
The track it would be at (Mallala Motorsport Complex) is okay with totally uncorked turbo systems, as the turbo takes a fair bit of volume and bark out of the note of a 2L I6. The only time I would cork it is when I'm putting it on and off the trailer at home.

By quick release muffler, I assume you mean a bolt-on unit? I want the 3.5" pipe to hang out the rear, not stop under the car.

As for the remote control one, too expensive, and too 'sensitive' for a drift car, I'd hurt it within about 3 seconds. Besides, it's just the same thing, only in a different location, and instead of a cable running up through the floor, its electronically controlled.
 
My exhaust pipe has a hole in it(like before the cat converter), other then the noise produced is this bad?
 
Up to you, then. I'd route it out the front bumper for the straightest shot and the shortest pipe.
 
Thatman - It releases toxic fumes into the atmosphere. However, depending on the age of the car, that may not be any different to the fumes it releases after the cat, as they only actually last a few years (As I understand it). Also your back pressures will all hinky, which can lead to loss of power and exhaust valve burnout.

[EDIT]
Thats not such a stupid idea niky, except for the 6' flames that it will produce on back-off.
 
I see, well it sounds like it robs power. makes sense. but the thing can only output max 92 anyways, thanks for the comment back.
 
And since when have flames shooting sideways out of the car been a bad thing? :lol:

It would also be easy to work out... you'd just have a test pipe welded to the side of your downpipe, and the exhaust cut off would sit in your bumper covered by a thick metal plate and a gasket. Three screws and it's open. :D

Of course, the Apexi valve would look so much better. I've been looking at those systems, but since I'm NA, I want one that's rpm-activated.
 
Then what you need is a weighted valve, as the gasses flow quicker, it pushes the valve open, and when you back off, or are cruising, it shuts up, similar to the flap on a truck stack.

I wasn't thinking of flames out the side of the car being bad,m except that I would fry the spectators and the lead car when I'm following through right hand corners.

Could always point it straight forward...
 
Making a front bumper exit exhaust will take "loud" to a whole new level, I wouldn't recommend it.

Why not just get a nice big exhaust and put a silencer in it when you go on the street?
 
Perfect Balance
Making a front bumper exit exhaust will take "loud" to a whole new level, I wouldn't recommend it.

Why not just get a nice big exhaust and put a silencer in it when you go on the street?
Click to expand...

On the street? Now why would I want to give the popo any more reason to rape me? Whats the first most people would think if they saw a fully stickered up track car on the road, complete with missing back seat, big 5" tacho and shiftlight, an intercooler the size of your average commercial airconditioner, a locked diff and an intake noise that sounds not unlike a jet turbine?

I can tell you what would happen, I would get maybe 2km down the road, see red and blue flashing lights behind me, pull over, get a nice yellow sticker on the windscreen, and be told to walk home.
 
guska
On the street? Now why would I want to give the popo any more reason to rape me? Whats the first most people would think if they saw a fully stickered up track car on the road, complete with missing back seat, big 5" tacho and shiftlight, an intercooler the size of your average commercial airconditioner, a locked diff and an intake noise that sounds not unlike a jet turbine?

I can tell you what would happen, I would get maybe 2km down the road, see red and blue flashing lights behind me, pull over, get a nice yellow sticker on the windscreen, and be told to walk home.
Click to expand...
I was under the assumption that you would also be driving the car on the street.

In that case, why do you need any sort of ECV?
 
I guess this could be somewhat of an exhaust question, but why is the turbine housing of a turbocharger always rusty and crusty looking? Is it made from steel while the compressor housing is aluminum, and does the steel oxidize with all of the heat?
 
Perfect Balance
I was under the assumption that you would also be driving the car on the street.

In that case, why do you need any sort of ECV?
Click to expand...
Politeness to my neighbours, who wouldn't appreciate me starting up a straightpipe on a Saturday afternoon to load in on the trailer.



Omnis
I guess this could be somewhat of an exhaust question, but why is the turbine housing of a turbocharger always rusty and crusty looking? Is it made from steel while the compressor housing is aluminum, and does the steel oxidize with all of the heat?
Click to expand...
Correct. IFAIK
 
An exhaust cut-out is a very easy way for the car to make much more power, as long as track regulations allow it. You can only go so wide with a full-lengthe exhaust before you run into fitment issues and low-exhaust velocity issues. The cut-out just skips the entire problem by cutting out the rest of the exhaust.

Heck, even non-turbo cars can make power with a straight through exhaust, some guy with a Civic finally put it to the dyno-test (for a K20A engine)... an electric exhaust cut-out on a stock engine produced 11 hp more, with torque gains all the way through the rpm band... despite what people may say, you don't need backpressure to maintain low rpm torque, just non-turbulent airflow, which a cut-out right after the headers easily provides.

My only issue with it is, on a naturally aspirated car, it's likely that a full-length exhaust will give the same gains or a bit more without making an ungodly racket. On a turbo? hehehe... who cares?

Is there space on the front rocker panel for you to route the exhaust to? Maybe a diagonal exit exhaust?
 
guska
Politeness to my neighbours, who wouldn't appreciate me starting up a straightpipe on a Saturday afternoon to load in on the trailer.




Correct. IFAIK
Click to expand...
That's a crappy reason IMO. In that case I would just push it and save a few bucks.
 
niky
Is there space on the front rocker panel for you to route the exhaust to? Maybe a diagonal exit exhaust?
Click to expand...
The what? I only talk Ostraalyan!


Perfect Balance
That's a crappy reason IMO. In that case I would just push it and save a few bucks.
Click to expand...
Ok, I may have to describe the area it will be parked in.

To get out of my driveway, you need to go UPhill, and since the car can't even legally stand on the road, it will have to be loaded onto the trailer in the driveway. That means trying to push a family-sized car uphill, and then up a steeper angle onto a trailer. Sure I'll have a winch, but I would rather drive the sucker on.

I have however been toying with the idea of having a clamp-on rear section, with a silencer for home, and an upturned single dump dump pipe that can be replaced as required. The other idea, is get my mate to make up some more silde-in silencers. They clip in and shut the exhaust right up.
 
Rocker, or whatever they call it, where they attach the side skirts to.

Of course, a side exit exhaust often requires some cutting and welding to get those annoying pieces of the frame out of the way... :lol:
 
Not to mention you can burn the 🤬 out of your legs with a side exhaust. I saw it happen to some guy getting out of someone else's side-exaust Viper at a car meet.
 
Nah, I'll just go for a boring old rear exiting zorst
 

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