why x pipe?

[ZStig]

whoever here thinks a X-pipe is a useless exhaust part of a Z4M exhaust you're welcome to remove it and run the 2 pipes seperate, and find out how shitty it will sound at your own cost

[Westersund]

Originally Posted by ZStig

whoever here thinks a X-pipe is a useless exhaust part of a Z4M exhaust you're welcome to remove it and run the 2 pipes seperate, and find out how shitty it will sound at your own cost

Sounds good to me.

Originally Posted by johanness

I think Westersund is 12yrs old

Saying that a X-pipe is a gimmick was bluntly put by me. What I should have said instead was that the minimal difference I believe it makes on a car that already has equal length headers before the X-pipe install is not worth the time, money nor added weight.

When I ordered my custom mufflers for my car I went to the leading exhaust manufacturer in Sweden and talked to them specifically about X-pipes. They make exhaust systems to all kinds of high end racing cars and road cars. What they told me was that it won't make a noticable difference in performance. The sound however might change. But for the better? That's up to the beholder.

[Gallardo Rosso]

If you would have mentioned the guy in Sweden you talked to first, most of us could have just agreed that x-pipes were gimmicks from the start and avoided most of this thread.

[GuidoK]

Originally Posted by Westersund

What I should have said instead was that the minimal difference I believe it makes on a car that already has equal length headers before the X-pipe install is not worth the time, money nor added weight.

Then how much difference does it make?
I mean: If you judge on that, then you must have something of a dynochart for a car with and a car without x-pipes on the otherwise same exhaust system.
In the small clip (the one with the shabby guy) you could clearly see that air flowing in the one pipe creates a suction/low pressure in the other pipe, helping to scavenge the next firing cilinder when its exhaust valves open. The only thing is that because an engine produces a pulsating pressure, it will have more effect in some rev bands. Great, more torque in that rev band.

Also I don't see much added weight

And if or not it's worth money: depends on the gains doesn't it? If you're tuning a car, I personally have a standard/target of about 50-75usd per gained HP (ex install; I do everything myself). A lot of FI sets fall into that category. Even my schrick cams fell into that category.
So if the x pipe costs 100usd, it should gain about 1,5HP. Then it's worth the money to me
I also don't seen an x pipe as a particularly expensive part. A lot of stock aftermarket resonators (like certain magnaflow models etc) already have x pipes intergrated.

[Westersund]

Originally Posted by Gallardo Rosso

If you would have mentioned the guy in Sweden you talked to first, most of us could have just agreed that x-pipes were gimmicks from the start and avoided most of this thread.

Very funny.

http://www.ferrita.com/en/

Originally Posted by GuidoK

Then how much difference does it make?
I mean: If you judge on that, then you must have something of a dynochart for a car with and a car without x-pipes on the otherwise same exhaust system.
In the small clip (the one with the shabby guy) you could clearly see that air flowing in the one pipe creates a suction/low pressure in the other pipe, helping to scavenge the next firing cilinder when its exhaust valves open. The only thing is that because an engine produces a pulsating pressure, it will have more effect in some rev bands. Great, more torque in that rev band.

Also I don't see much added weight

And if or not it's worth money: depends on the gains doesn't it? If you're tuning a car, I personally have a standard/target of about 50-75usd per gained HP (ex install; I do everything myself). A lot of FI sets fall into that category. Even my schrick cams fell into that category.
So if the x pipe costs 100usd, it should gain about 1,5HP. Then it's worth the money to me
I also don't seen an x pipe as a particularly expensive part. A lot of stock aftermarket resonators (like certain magnaflow models etc) already have x pipes intergrated.

How much difference it makes? That's exactly what I wanted to find out by going into this thread. I thought one of the X-pipe advocates had some dyno charts of the difference. Don't get me wrong, I want it to work but I'm not convinced it make a significant difference in power.
I saw the clip with the shabby looking guy, it was interesting I'll admit. However there's a difference between the pressure/vaccum an engine can create and an air compressor that puts out 5 bar or more. The effect is there, but can the engine create that much pressure it will matter? Will it get you 0,5 HP? 1 HP? 5HP?

[Westersund]

Found a good thread, it's a Mercedes. However the X-pipe removed the secondary cats as well.

http://mbworld.org/forums/c63-amg-w2...-2010-c63.html

[GuidoK]

Originally Posted by Westersund

However there's a difference between the pressure/vaccum an engine can create and an air compressor that puts out 5 bar or more.

That air hose doesn't make a 5 bar air column in the exhaust. (that 5 bar is there before the pinhole of the air blow gun). In the exhaust it just creates an air velocity, and I bet that the air velocity coming out of the engine at higher revs is way more (like a factor 5 or so) than that small air blow gun.
If there was 5 bar of air pressure difference coming from that 60mm piping outlet, that garage wouldn't be standing there.
If you want the exact pressure in the pipes, a good estimate would be to devide the exhaust piping area by the pinhole area. Devide the air hose pressure by that factor and you have the pressure in the exhaust. That will probably be a few millibars.

But anyway: bmw put a crossover in the stock exhaust of the z4m, so they probably gained something by that. Otherwise they would have left it out as that is cheaper. It is not a unique selling point otherwise they've put it with big letters in their folders.

[p1nk50ck]

definitely some interesting stuff in here!

I didn't think i was gonna cause all of this commotion with what i thought was a simple question

[inTgr8r]

Originally Posted by Westersund

Saying that a X-pipe is a gimmick was bluntly put by me. What I should have said instead was that the minimal difference I believe it makes on a car that already has equal length headers before the X-pipe install is not worth the time, money nor added weight.

Equal length headers has no impact until pulses reach the X.

One other point to consider is the pulse timing as related to firing order.
In a single side you will have 3 pulses out of the complete 6 cylinder firing sequence.
Cyl 1,2,3 on one side; 4,5,6 in the other side.
Since firing order is not sequential, those 3 pulses in one bank are not evenly spaced.
Some pulses(of the 3) will have a larger gap between them than others.

The X-pipe marries the pulses and gaps of all 6 as they flow past the X, so that all spacing is equal.


:edit:
Double checked And firing order is such that gaps are equal....
So X pipe just shortens the gaps

[mfanatic325]

I've just been lurking for the past half year on the forums, but today I'm a bit bored at work so I've decided to post

All I know is...our cars sound like doodoo

[p1nk50ck]

Originally Posted by mfanatic325

I've just been lurking for the past half year on the forums, but today I'm a bit bored at work so I've decided to post

All I know is...our cars sound like doodoo

It's not THAT bad. but it could be better. I mean, how does a tiny little 1.4 liter Abarth 500 sound so amazing, and our cars sound so mehhhh?

and thanks for choosing my thread to respond to after a 1/2 year of lurking!

[DRedman45]

Originally Posted by mfanatic325

I've just been lurking for the past half year on the forums, but today I'm a bit bored at work so I've decided to post

All I know is...our cars sound like doodoo

I thought that too when I heard every exhaust on every s54 car....the ar20's fixed that issue haha

[Westersund]

Originally Posted by GuidoK

That air hose doesn't make a 5 bar air column in the exhaust. (that 5 bar is there before the pinhole of the air blow gun). In the exhaust it just creates an air velocity, and I bet that the air velocity coming out of the engine at higher revs is way more (like a factor 5 or so) than that small air blow gun.
If there was 5 bar of air pressure difference coming from that 60mm piping outlet, that garage wouldn't be standing there.
If you want the exact pressure in the pipes, a good estimate would be to devide the exhaust piping area by the pinhole area. Devide the air hose pressure by that factor and you have the pressure in the exhaust. That will probably be a few millibars.

But anyway: bmw put a crossover in the stock exhaust of the z4m, so they probably gained something by that. Otherwise they would have left it out as that is cheaper. It is not a unique selling point otherwise they've put it with big letters in their folders.

I haven't tried, but it feels like a blow gun will produce more vaccum/suction than the engine. But I don't know that for sure, could be the other way around.

Yes the Z4M has a cross over, but at the same time many very expensive super sport cars don't. Seems like the car industry is divided in this subject.

Originally Posted by inTgr8r

Equal length headers has no impact until pulses reach the X.

One other point to consider is the pulse timing as related to firing order.
In a single side you will have 3 pulses out of the complete 6 cylinder firing sequence.
Cyl 1,2,3 on one side; 4,5,6 in the other side.
Since firing order is not sequential, those 3 pulses in one bank are not evenly spaced.
Some pulses(of the 3) will have a larger gap between them than others.

The X-pipe marries the pulses and gaps of all 6 as they flow past the X, so that all spacing is equal.


:edit:
Double checked And firing order is such that gaps are equal....
So X pipe just shortens the gaps

Good explanation, it sounds logical...

[pokeybritches]

The car industry isn't "divided". There are times an X-pipe is beneficial, and there are times when it isn't.

[GuidoK]

Exactly. I don't think car manufacturers see it as a 'decision in principle'.
They develop an exhaust system that has to meet certain specs. An x-pipe can be part of that. I can imagine that the number of cilinders, or the possible places where you can fit that x-pipe all play part in that descision combined with what gains are to be expected in what revrange.
Because the scavenging effect that comes from an x pipe is pulsated (the 'drive' that initiates the effect is also pulsated) that means that there are also moments in time that it works non beneficial, because the air in the exhaust moves like an 'air column' through the exhaust in those frequencies. That means that the effectiveness of the x pipe depends on the rev range, and that there are also parts of the revrange that the xpipe may not work beneficial at all, it will restrict (the air pressure column can suck the air out of the cilinder, but when not properly timed (depending on revs, as the distance between xpipe and cilinder valve is a set value) it can also press down on the air in the cilinder.
Not only an x pipe does that, an exhaust itself does that too. That's why different exhaust lengts give different gains at different revs. It's one big pile of harmonics.

[Gallardo Rosso]

If you wish to be an expert on this subject read the following book

http://books.sae.org/r-186/

All will be revealed! It's all math and science. You can actually calculate (and simulate). What an x-pipe will (and won't) do.

You will actually learn that the systems aren't as linear as you think and certain concepts like equal length headers aren't necessarily "optimal", back pressure is a meaningless term in exhaust design and it's all about wave motion. Air actually "flows" INTO and OUT OF your exhaust tip as well as your throttle body.

[habitat412]

I just had a custom complete exhaust system made for my Z4M and the x-pipe drastically helped with back pressure in turn creating more torque for my car. Now mind you I have no primary nor secondary cats and no resonators as well in my system. I am running CSL headers though. Being that there is no other part of my system that creates back pressure the x-pipe is important as far as it pertains to my system in creating that to give me the torque. When the x-pipe didn't have the proper turbulence created at the crossover point I felt a drop in torque because I had little to no back pressure created from the x-pipe. Plus when I let go of the throttle at WOT there would be no backfire what so ever but now since the x-pipe has been properly fixed when I let go of the throttle at WOT it sounds like a AK-47 going off!

[habitat412]

As far as the Pagani and any other forced inducted engines go x-pipe are useless since you have boost running and you are mainly just trying to get the exhaust gases out as soon as possible but then again I'm not too sure about that. I see a lot of turboed and supercharged cars with the dump pipes and they seem to have little or no effect on power numbers because of the velocity of exhaust gases produced by the turbos.

[racerbruce]

http://www.turnermotorsport.com/p-16...-2-x-pipe.aspx

Our car has an x-pipe, but it includes a resonator muffler....has anyone installed this resonator-delete x-pipe? This x-pipe retains the cross over concept but deletes the resonator muffler....anyone?

[inTgr8r]

Yes, many have installed this one or the R.Eng. Xpipe.
The advantage of the R.Eng pipe is that it's a direct OE replacement.
The SS pipe you linked to requires the use of SS rear mufflers as well.

[NickyC]

The S54 has and always will sound like crap to me regardless of what is done to it. It's either a quiet mess like in the Z4M stock, a raspy annoyance like in the E46 M3 and Z3M, or a total monstrosity when people put Rpi exhausts and other crap on the car and then come on the forums and try to tell people it sounds "exotic". The S54 doesn't sound "exotic", it doesn't even sound good no matter how much money you throw at it. 9/10 of the exhaust systems for our cars give it a horrible drone. I wanted to shoot myself when I installed Diablos on my last Z4M, it made me sick every time it hit that 2300rpm area.

This time around, I'm just going to be looking into perhaps making the exhaust tips look nicer on the stock system. Maybe weld some larger tips on and call it day. I'd rather have quiet, than some annoying, droning, raspy mess which is all this engine produces.

Also, if you think that coupe above sounds good, you're lying to yourself just like the Rpi owners and their "exotic" bullshit.

[GuidoK]

The raspy metallic sound is a characteristic sound for an inline six.
The more revs, the more you hear it. If you don't want that, you have to muffle it.
That's why you hear it more on certain i6 engines than others: revs and how much the exhaust (or if present: turbo) muffles it. But it is a base part of the inline six sound.
Just as the the burbling sound is a base characteristic of a (crossplane) v8.