Nicely put! Looking forward to getting mine installedYou have a lot of time on your hands Eb
The answer is that all of them affect the sound.
Exhaust flow is not like water in a pipe, it comes in pulses, which start at the exhaust port.
The theory is that any change in pipe cross section (I.e. the crossover) causes a reflection of the pressure pulse back in the opposite direction (a shockwave rather than a reversal of flow). The distance from the port of the change determines the travel time and therefore the point in the rpm range at which the exhaust is “tuned”. By tuned I mean that if the shockwave arrives back at the exhaust port while both the inlet and exhaust valves are open this assists with cylinder filling. In addition, the crossover reduces the overall back pressure by splitting the flow between two pipes.
The smaller the crossover, the smaller the “signal”.
Full bore x-pipes give the lowest back pressure and largest signal.
H pipes have the pulse rushing past the full bore link pipe giving a pressure reduction on the other side, increasing scavenging (and sounding a bit rortier).
In a single make race series where 1-2 hp might make a difference, there is probably an ideal. On a road car it’s unlikely to be measurable (and will be affected by all sorts of other stuff). So just go for the sound you like.
Silly me, Eb, I always assumed that the dapper gent behind the wheel of your car may be more interested in a pipe such as this:Thanks Zep. Yes I expected it to change but does any one have any description what the changes would be?
Perhaps we need to measure the different x-pipe offerings and record how each sounds to get an insight?
Eb
Thanks Zep. Yes I expected it to change but does any one have any description what the changes would be?
Perhaps we need to measure the different x-pipe offerings and record how each sounds to get an insight?
Eb
That’s a great reply, very, very informative.You have a lot of time on your hands Eb
The answer is that all of them affect the sound.
Exhaust flow is not like water in a pipe, it comes in pulses, which start at the exhaust port.
The theory is that any change in pipe cross section (I.e. the crossover) causes a reflection of the pressure pulse back in the opposite direction (a shockwave rather than a reversal of flow). The distance from the port of the change determines the travel time and therefore the point in the rpm range at which the exhaust is “tuned”. By tuned I mean that if the shockwave arrives back at the exhaust port while both the inlet and exhaust valves are open this assists with cylinder filling. In addition, the crossover reduces the overall back pressure by splitting the flow between two pipes.
The smaller the crossover, the smaller the “signal”.
Full bore x-pipes give the lowest back pressure and largest signal.
H pipes have the pulse rushing past the full bore link pipe giving a pressure reduction on the other side, increasing scavenging (and sounding a bit rortier).
In a single make race series where 1-2 hp might make a difference, there is probably an ideal. On a road car it’s unlikely to be measurable (and will be affected by all sorts of other stuff). So just go for the sound you like.
I'm not a yob, I'm a ******* connoisseur!This could be come a separate sub genre of the audiophile thread....
Eb
That’s a great reply, very, very informative.
I tend to be overly analytical about the simple things in life, such as X Pipes etc lol! I fully agree with Zep that any change in design, whether it be position of the X/H, the length / diameter of the cross over point, the direction of the gas flow, through to the material type, material thickness, bore size etc, will all have an affect on the sound. It will also have an impact on how well the gases travel, which in turn determines the “sound” made, plus performance.
I loved the sound of the Larini X on my last Granturismo. The tone and loudness for me were perfect. With so many others on the market (Sportsitalia, Urutu, Jarens, Simetti, Autoshield, Supersprint, Capristo and a number of European sourced and not forgetting you can get one fabricated), I’d guess they all sound similar ish! However, on past V8 cars (Merc / TVR) I always went with the theory that the X should be closer to the engine, plus that quality counts. So on that basis and the fact I loved the sound of the Larini, I either wanted one of those for my new Granturismo or something close. I got it down to the Sportsmaserati, Jarens and Larini, this is purely because of the design, position of the X (my preference is nearer the engine), type of X and material type (T316 preference). Jason at Jarens responded very quickly and said he’d make it however I wanted it, so I went that route and had him position the X further up the piece than he normally would.
I’m sure all the other X pipes are great, but thought I’d share my thought process (some of it).
Hopefully you haven’t yawned too much with my reply lol lol
Jules