Larini Sports Center ‘H Pipe’
- Thread starter ChrisQP09
- Start date
While pondering x-pipes I've wondered what the parameters are that affect the sound
eg
- where the cross over is relative to the manifold/exit. ie further towards the engine or away
- Shape of the X
- long X with a large shared chamber
- tight X where the shared chamber is smaller (most like an H pipe?)
Eb
eg
- where the cross over is relative to the manifold/exit. ie further towards the engine or away
- Shape of the X
- long X with a large shared chamber
- tight X where the shared chamber is smaller (most like an H pipe?)
Eb
Zep
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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.
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.
Last edited:
ChrisQP09
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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.
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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:
Zep
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If I have learned anything from years of seeing people trying to describe a noise, you might be right, but even then, it will vary from car to car.
Cyclone1
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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 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
Sam McGoo
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Also, when comparing sound, the the effect due to the condition/mileage of your exhaust Cats and rear boxes cannot be underestimated. My car sounds substantially more vocal than it did when I first got it 3.5 years, and 16k miles ago. From 18k to 34k has really opened it up. (I do like to use the revs as well) which does make sense.
Sam McGoo
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Also, when comparing sound, the the effect due to the condition/mileage of your exhaust Cats and rear boxes cannot be underestimated. My car sounds substantially more vocal than it did when I first got it 3.5 years, and 16k miles ago. From 18k to 34k has really opened it up. (I do like to use the revs as well) which does make sense.
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I'm not a yob, I'm a ******* connoisseur!
ChrissGT
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From what I understood to gain the most performance is to have the crossover as close as possible to the engine. This would increase scavenging and thus flow. So ideally right where both downpipes meet you should place a crossover (h or x).
In the larini options, on the H pipe the crossover is to the front, where the X is in the middle and for oem the x is at the rear. These are small, but probably measureable differences.
I found this picture, of a exhaust install on a granturismo. But this seems to me to be best position for the crossover.
ChrisQP09
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Happy to report that the H pipe is now fitted. Wow what a difference!
While I will put videos up, Its really in person when it can be appreciated.
First impressions. Start up is a slight bit louder with valves closed. Valves open is transforms the sound.
On the move low down, the only way I can describe it is a blend between American muscle and Italian. The Italian becomes more pronounced at volume as the rev range progresses. The downshifts are louder but not absurd, with more pops and bangs.
No drone that my ear can pick up on but the difference is an improvement overall in my opinion. Definitely worth the money, and the best bit is that the sound will probably age better as the exhaust beds in.
While I will put videos up, Its really in person when it can be appreciated.
First impressions. Start up is a slight bit louder with valves closed. Valves open is transforms the sound.
On the move low down, the only way I can describe it is a blend between American muscle and Italian. The Italian becomes more pronounced at volume as the rev range progresses. The downshifts are louder but not absurd, with more pops and bangs.
No drone that my ear can pick up on but the difference is an improvement overall in my opinion. Definitely worth the money, and the best bit is that the sound will probably age better as the exhaust beds in.