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Old 11-23-2012, 02:21 PM
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x pipe distance from valves? does it make a difference?

This all is in relation to a 90 degree v8.

So myself and a college have been doing quite a bit of research on exhaust dynamics for the past 8 months or so. He even got a chance to talk with Vizard for a short while. Interesting conversation there.

One thing that is troubling me and my friend is the exhaust pules in relation to the x pipe location.

One thing we are looking for is a particular sound. We have a preference toward the European v8 sound. Not JUST the performance in mind here. If you are familiar with 180* headers and how they sound you will understand this.

We have come down to using a particular design of x pipe based on the "IPE F1 exhaust for the e92 m3". Try google images to see what I am talking about. The problem we are seeing is the multitude of locations that the x pipe is placed along the travel of the exhaust. I have seen a lot of factory vehicles (maserati and ferrari including here) that tend to place the x pipe in the middle of the car (when front engine rear wheel drive in mind) or farther back. Some performance ideas are that the closer the x pipe to the collectors the closer it will perform like a 180* header. Also I have read some bs theory that the exhaust temp is a big deal here as in where ever it gets the hottest that is where the x pipe should be placed. The exhaust temp can be controlled by the engine tune. So to me this is a load of crap.

What I am asking is - is there any factual information on the relation to the x pipe location compared to the distance of the exhaust valves?

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Old 11-23-2012, 02:34 PM
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the exhaust temp is how we determined how long collector extensions need to be.we used spray paint as an indicator,crude but accurate. The 180 degree sound will come with the X pipe.I would put the x pipe at the end of the collector extension if there is room to allow this. To tune the exhaust properly a lot of dyno time is required,then retuning of the entire package after exhaust wakes up the car. The headers and extensions will determine the power,where the torque or horse power is enhanced the most,after that,the exhaust system will determine how much you will lose after the quieting happens.
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Old 11-23-2012, 04:38 PM
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I was always told to take a regular old Crayola crayon and put a line down the exhaust pipe, start the car and let it warm up to the temperature where the thermostat opens. Now check out the crayon line. Wherever it stopped melting is where the x pipe should be....

kind of like vinniekq2 spray paint concept, just with a crayon you won't have overspray issues.
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Old 11-23-2012, 06:00 PM
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Originally Posted by lakeroadster View Post
I was always told to take a regular old Crayola crayon and put a line down the exhaust pipe, start the car and let it warm up to the temperature where the thermostat opens. Now check out the crayon line. Wherever it stopped melting is where the x pipe should be....

kind of like vinniekq2 spray paint concept, just with a crayon you won't have overspray issues.
i heard the cran idea from my associate as well.

i just don't buy the "hottest location" theory. something just doesn't seam right.
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Old 11-23-2012, 07:48 PM
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Originally Posted by blight View Post
i heard the cran idea from my associate as well.

i just don't buy the "hottest location" theory. something just doesn't seam right.
It doesn't seem right because its total bull ****e. your BS meter should be pegging red and lights and whistles going off.

first off, and X pipe is useless for power, BUT if you are trying to locate to some harmonic length you feel is somehow magical enough to grant you power the heat generated or translated along the length of an exhaust pipe is irrelevant.
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Old 11-23-2012, 07:53 PM
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It doesn't seem right because its total bull ****e. your BS meter should be pegging red and lights and whistles going off.

first off, and X pipe is useless for power, BUT if you are trying to locate to some harmonic length you feel is somehow magical enough to grant you power the heat generated or translated along the length of an exhaust pipe is irrelevant.
Sooooo.. behind the mufflers is ok?
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Old 11-23-2012, 09:24 PM
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Sooooo.. behind the mufflers is ok?
no. Not running one at all is okay, running one ahead of the mufflers will change your sound, it won't change your power at all.
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Old 11-24-2012, 08:22 AM
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The Ferrari V8 sound comes from the 180 degree crankshaft that Ferrari uses. You are always alternating banks of cylinders in the firing order.

A 90 degree crankshaft will fire two cylinders on the left bank, and two cylinders in the right bank next to each other, sometime in the firing order.

To make 180 degree headers for a 90 degree V8, you have to cross over one exhaust pipe from each bank to the other side of the engine, and that is a plumbing nightmare, and usually results in header primary length being too long to tune for high RPM power.

You can find some clues on how long header pipe should be, but is is based on the speed of sound, and you also have to consider the gas the sound wave is moving through is hot, and also moving.
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Old 11-28-2012, 04:31 AM
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The Ferrari V8 sound comes from the 180 degree crankshaft that Ferrari uses. You are always alternating banks of cylinders in the firing order.

A 90 degree crankshaft will fire two cylinders on the left bank, and two cylinders in the right bank next to each other, sometime in the firing order.

To make 180 degree headers for a 90 degree V8, you have to cross over one exhaust pipe from each bank to the other side of the engine, and that is a plumbing nightmare, and usually results in header primary length being too long to tune for high RPM power.

You can find some clues on how long header pipe should be, but is is based on the speed of sound, and you also have to consider the gas the sound wave is moving through is hot, and also moving.

been there done that- I am waiting to hear from reeves callaway. he will get back to me after some car show. depending on what he says, I am going to pick on jere stahl to make me a set of 360 headers.
http://www.lincolnvscadillac.com/att...1&d=1089120898
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Old 11-28-2012, 09:36 AM
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Have you tried putting ferrari mufflers on your car. alot of the sound comes from them. If you cut the mufflers of a ferrari they do not sound the same anymore.

Traditianl 90 degree is not going to make the flat plane crank sounds. But a 4-7 swap with the right headers my help a little. also you will find you can install a 180 crank but I think the cams they sell for them fire two cyinlinder on same rotation. you got to hear one. truck pull guys used to use them. not sure if they do any more.
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Old 11-28-2012, 10:28 AM
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The quality of Jere Stahl headers is very good.His shop built mt step headers.He needs to know the engines horse power to determine pipe size(s)
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Old 11-28-2012, 10:42 AM
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Originally Posted by hcompton View Post
Have you tried putting ferrari mufflers on your car. alot of the sound comes from them. If you cut the mufflers of a ferrari they do not sound the same anymore.

Traditianl 90 degree is not going to make the flat plane crank sounds. But a 4-7 swap with the right headers my help a little. also you will find you can install a 180 crank but I think the cams they sell for them fire two cyinlinder on same rotation. you got to hear one. truck pull guys used to use them. not sure if they do any more.
there is so much wrong in this statement i don't even know where to start...

ug... ok YES it is the 180 crank but that is because of the exhaust pulse. IT HAS NOTHING TO DO WITH THE MUFFLER ON THE FERRARI!!!!!!!!!!!!!!!!!!!!!!! OMG. I have seen them cut open. There is nothing in any of the exotic car mufflers that make a difference in the sound. They are designed entirely around muffling the exhaust. Its the design of the x pipe (shape etc), the headers, the cam(s), and the initial throw of the crank. 180 headers basically get the 4 cyl pulses together so its like having two 4 cyls. Its the cyls that are 180 degrees from each other. This is the same thing a 180 crank does but without all the vibration that goes with the 180 crank. The cross plane crank is a better design because of vibration/harmonics, but the exhaust pulses fire every 90 which does not take advantage of the vacuum effect of the exhaust to scavenge the heads.

To me it looks like if the x pipe location changes the sound of the engine changes for a couple of reasons. This is without the 180 crank or headers in mind. Think tri-y headers. If its further down the car will the tone be a higher freq or lower freq and vise versa when it is closer to the valves? that is what I am looking to know. OR does it matter at all. To me it would just because a pipe length will affect the note, as well as when the exhaust gasses merge from left to right. It just makes sense. BUT I am not sure which is which. Hence the question.

This has turned into what sounds like a ferrari. I know what does. I care about x pipe location.
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Old 11-28-2012, 10:45 AM
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Originally Posted by ap72 View Post
no. Not running one at all is okay, running one ahead of the mufflers will change your sound, it won't change your power at all.
I think it may effect the power but so little that it doesnt really matter. If you don't have 180 headers, depending on how close it is after the collectors it should help with the scavenging effect. It would almost be like part of the headers for it to work.

I do think it would change the sound though. Good call.
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Old 11-28-2012, 10:51 AM
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You know what sounds like a Ferrari- a Ferrari.

There is a LOT more to their engines than some magic crank design. An sbc is VERY little like a Ferrari, hell by your crank theory a air-cooled VW 1600 should sound like a Ferrari...
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Old 11-28-2012, 10:57 AM
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Originally Posted by blight View Post
This all is in relation to a 90 degree v8.

So myself and a college have been doing quite a bit of research on exhaust dynamics for the past 8 months or so. He even got a chance to talk with Vizard for a short while. Interesting conversation there.

One thing that is troubling me and my friend is the exhaust pules in relation to the x pipe location.

One thing we are looking for is a particular sound. We have a preference toward the European v8 sound. Not JUST the performance in mind here. If you are familiar with 180* headers and how they sound you will understand this.

We have come down to using a particular design of x pipe based on the "IPE F1 exhaust for the e92 m3". Try google images to see what I am talking about. The problem we are seeing is the multitude of locations that the x pipe is placed along the travel of the exhaust. I have seen a lot of factory vehicles (maserati and ferrari including here) that tend to place the x pipe in the middle of the car (when front engine rear wheel drive in mind) or farther back. Some performance ideas are that the closer the x pipe to the collectors the closer it will perform like a 180* header. Also I have read some bs theory that the exhaust temp is a big deal here as in where ever it gets the hottest that is where the x pipe should be placed. The exhaust temp can be controlled by the engine tune. So to me this is a load of crap.

What I am asking is - is there any factual information on the relation to the x pipe location compared to the distance of the exhaust valves?
All in the math; if you're looking for tuning the note, the crossover needs to be at a place where the timing of the pulses is correct to make the sound. Unfortunately trying to make 90 degree headers on a 90 degree V8 with a 90 degree crankshaft will result in the sound you want only happening at the tuned RPM for the length and at major harmonics of that length and RPM, the rest of the time it will sound like a 90 degree American V8.

By now in your classes you should have crossed the data point that the temperature within in the exhaust system is higher than STP and constantly variable with distance from the exhaust valve, RPM, and loading on the crankshaft; so using STP calculations of Mach number within the exhaust system is at best approximately correct and at the same time absolutely wrong. So without a ton of test equipment and the engine strapped to a dyno you end up totally shooting the math into the dark.

A cross-over whether H or X for the sake of engine efficiency must be ahead of the most restrictive elements such as catalytic converter and muffler because the whole purpose of the cross over is to establish some peak flow sharing between the individual capacities of each side. This is the only thing that will be constant with RPM and loading where tuning will be sensitive to RPM (frequency of input) as well so will be constantly variable. The exhaust comes in pulses rather than a stream which allows all of the shared capacity and tuning to happen. Even a gas turbine does this, in high speed photography of jet exhaust you can see the individual pulses as balls of flame inside the exhaust stream.

You have to be careful with cross-overís especially the X because they can (or not) trip a return wave as if the exhaust stream has hit the end of the pipe. Depending upon residual strength of the original exiting pulse you can also get additional return waves tripped by the cat converter, muffler, resonator, and pipe tip, obviously each of differing strength. So the cumulative effect of waves coming and going with the resuting wave attenuation or amplification this quickly gets really nasty. Often Smokey's old fashion approach of cut and try becomes as good a process as it gets. You could model this but the freaking data needed going in leads back to the original problem of the number of calculations against a constantly changing environment. Sounds like a good Senior Thesis to me, one big enough to take a line of thought all the way through graduate school. Brush up up on your Calculus.

Bogie
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