Bypass exhaust screamer valves

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tzortzViper

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Which one of these best describes your goal:

1. Have the cutouts always open at a specific RPM and tune according to this. (i assume this is what ZO6/ferrari/porsche do...)(only downside i see to this on your Gen4 is that it could get annoying having those things always popping open making an obnoxious sound as where the ZO6/ferrari/porsche systems are "tuned" to sound good.)

2. Have the cutouts open on demand of the operator while leaving the "cutout tune" running on the car. (this could cause the car to run poorly with a non-optimal A/F ratio when the cutouts are Not open)

3. Have the cutouts open on demand of the operator without a tune. (this could cause the car to run poorly with a non-optimal A/F ratio when the cutouts Are open)

4. Have the cutouts open on demand of the operator while simutaniusly being able to switch the tune on-demand to compensate for the cutout.
This would be the best case senereo IMO, However i do not think it is possible to change the Viper's tune on the fly.

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I personally think that a better approach to making power and getting a better sound from your viper would be to do headers, full exhaust system, &Tune. These mods are proven to make over 50hp&tq. so use that as a reference when you get to test out your cutout mod on the dyno.

It is exactly what I have been thinking all these days.

Firstly, that modified wastegate I will use, will open and close instantly. So, it will be no intermediate positions (half closed, little open, etc.).
Hence, I can, at once, have it automaticaly open at around 4,500rpms.

At that range (from 4,500rpm to redline) and WOT , the EFI is in open loop. Means that the A/F is not based in the oxygen sensors' feedback anymore.

Now, I am trying to find if I intervene in the MAP sensor to alter the signal, so the PCM get a little richer mixture (this will happen only at that rpm range and WOT, simultaneously while openning the exhaust valves).

I am not quite sure if the PCM algorithm, would let me alter the signal instantly and get it back to normal again ( I will have to check it with a wideband and a datalogger).

If anyone has tried it, please comment.


ps. I know there are certain combinations of headers and catbacks with proven results. But, I really dont compare it with the feeling of experimenting with your own car !


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tzortzViper

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Yes, I agree, post this on ViperAlley. I'm sure they can give you some more "feedback".

PS, I have built several race cars (most recently building a 8 second Daytona) I know just a little about making HP. This is an exercise in futility. Will you make any more power? Maybe a couple, will it need to be tuned to make the power? Yep!, Is it worth the effort? Nope.

A high flow cat, and good cat back system, engineered to be correct for your vehicle will out perform seat of the pants design. Have fun, it's your car do anything you want.


It would be nice to explain us the reason for not gainning anything to a zero backpressure exhaust system.


By the way, will that 8sec Daytona have a high flow cat and a good cat back system??




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Mopar Steve

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It would be nice to explain us the reason for not gainning anything to a zero backpressure exhaust system.


By the way, will that 8sec Daytona have a high flow cat and a good cat back system??




.

Nope the Daytona wont but my previous two Vipers did and so did my Corvette, Ok You win...GREAT IDEA!

Like I said before it's your car, enjoy it any way you like.
 
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tzortzViper

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Nope the Daytona wont but my previous two Vipers did and so did my Corvette, Ok You win...GREAT IDEA!

Like I said before it's your car, enjoy it any way you like.


Great answer, but still without explanation.



ps. Plum$$ , will you do it together?


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Mopar Steve

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The fact that you are calling these "Screamer valves" says that you are looking for noise not power. This is the kind of stuff that kids are always doing to screw up their cars. You will be selling this car at some point and with screwed up attempts at modifying the car like this you are just making the car worth much less than an un-modified car. Do you think that you are the only one that has ever thought of this? There are engineers that are modifying car for ultimate performance with virtually unlimited budgets that DO NOT do anything like this on these cars. Maybe there is a reason. I was amused by this post but am now becoming bored. Do some research yourself and learn why things work and don't work.

Most everyone has told you this but for some reason you are looking for more of an answer.

HERE:
Backpressure and velocity
Some people operate under the misguided notion that wider pipes are more effective at clearing the combustion chamber than narrower pipes. It's not hard to see how this misconception is appealing - wider pipes have the capability to flow more than narrower pipes. So if they have the ability to flow more, why isn't "wider is better" a good rule of thumb for exhaust upgrading? In a word - VELOCITY. I'm sure that all of you have at one time used a garden hose w/o a spray nozzle on it. If you let the water just run unrestricted out of the house it flows at a rather slow rate. However, if you take your finger and cover part of the opening, the water will flow out at a much much faster rate.

The astute exhaust designer knows that you must balance flow capacity with velocity. You want the exhaust gases to exit the chamber and speed along at the highest velocity possible - you want a FAST exhaust stream. If you have two pulses of equal volume, one in a 2" pipe and one in a 3" pipe, the pulse in the 2" pipe will be traveling considerably FASTER than the pulse in the 3" pipe. While it is true that the narrower the pipe, the higher the velocity of the exiting gases, you want make sure the pipe is wide enough so that there is as little backpressure as possible while maintaining suitablehttp://www.thumpertalk.com/forum/showthread.php?t=659727# velocity. Backpressure in it's most extreme form can lead to reversion of the stream - that is to say the exhaust flows backwards, which is not good. The trick is to have a pipe that that is as narrow as possible while having as close to zero backpressure as possible at the RPM range you want your power band to be located at. A smaller pipe diameter will produce higher exhaust velocities at a lower RPM but create unacceptably high amounts of backpressure at high rpm. Thus if your powerband is located 2-3000 RPM you'd want a narrower pipe than if your powerband is located at 8-9000RPM.

And:

Exhaust Scavenging

When an engine starts its exhaust stroke, the piston moves up the cylinder bore, decreasing the total chamber volume. When the exhaust valve opens, the high pressure exhaust gas escapes into the exhaust manifold or header, creating an exhaust pulse comprising three main parts: The high-pressure head is created by the large pressure difference between the exhaust in the combustion chamber and the atmospheric pressure outside of the exhaust system. As the exhaust gases equalize between the combustion chamber and the atmosphere, the difference in pressure decreases and the exhaust velocity decreases. This forms the medium-pressure body component of the exhaust pulse. The remaining exhaust gas forms the low-pressure tail component. This tail component may initially match ambient atmospheric pressure, but the momentum of the high- and medium- pressure components reduces the pressure in the combustion chamber to a lower-than-atmospheric level. This relatively low pressure helps to extract all the combustion products from the cylinder and induct the intake charge during the overlap period when both intake and exhaust valves are partially open. The effect is known as scavenging. Length, cross-sectional area, and shaping of the exhaust ports and pipeworks influences the degree of scavenging effect, and the engine speed range over which scavenging occurs.
The magnitude of the exhaust scavenging effect is a direct function of the velocity of the high and medium pressure components of the exhaust pulse. Performance headers work to increase the exhaust velocity as much as possible. One technique is tuned-length primary tubes. This technique attempts to time the occurrence of each exhaust pulse, to occur one after the other in succession while still in the exhaust system. The lower pressure tail of an exhaust pulse then serves to create a greater pressure difference between the high pressure head of the next exhaust pulse, thus increasing the velocity of that exhaust pulse. In V6 and V8 engines where there is more than one exhaust bank, Y-pipes and X-pipes work on the same principle of using the low pressure component of an exhaust pulse to increase the velocity of the next exhaust pulse.
Great care must be used when selecting the length and diameter of the primary tubes. Tubes that are too large will cause the exhaust gas to expand and slow down, decreasing the scavenging effect. Tubes that are too small will create exhaust flow resistance which the engine must work to expel the exhaust gas from the chamber, reducing power and leaving exhaust in the chamber to dilute the incoming intake charge. Since engines produce more exhaust gas at higher speeds, the header(s) are tuned to a particular engine speed range according to the intended application. Typically, wide primary tubes offer the best gains in power and torque at higher engine speeds, while narrow tubes offer the best gains at lower speeds.
Many headers are also resonance tuned, to utilize the low-pressure reflected wave rarefaction pulse which can help scavenging the combustion chamber during valve overlap. This pulse is created in all exhaust systems each time a change in density occurs, such as when exhaust merges into the collector. For clarification, the rarefaction pulse is the technical term for the same process that was described above in the "head, body, tail" description. By tuning the length of the primary tubes, usually by means of resonance tuning, the rarefaction pulse can be timed to coincide with the exact moment valve overlap occurs. Typically, long primary tubes resonate at a lower engine speed than short primary tubes.
Some modern exhaust headers are available with a ceramic coating. This coating serves to prohibit rust and to reduce the amount of heat radiated into the engine bay. The heat reduction will help prevent intake manifold heat soak, which will decrease the temperature of the air entering the engine.
 
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tzortzViper

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The fact that you are calling these "Screamer valves" says that you are looking for noise not power. This is the kind of stuff that kids are always doing to screw up their cars. You will be selling this car at some point and with screwed up attempts at modifying the car like this you are just making the car worth much less than an un-modified car. Do you think that you are the only one that has ever thought of this? There are engineers that are modifying car for ultimate performance with virtually unlimited budgets that DO NOT do anything like this on these cars. Maybe there is a reason. I was amused by this post but am now becoming bored. Do some research yourself and learn why things work and don't work.

Most everyone has told you this but for some reason you are looking for more of an answer.

HERE:
Backpressure and velocity
Some people operate under the misguided notion that wider pipes are more effective at clearing the combustion chamber than narrower pipes. It's not hard to see how this misconception is appealing - wider pipes have the capability to flow more than narrower pipes. So if they have the ability to flow more, why isn't "wider is better" a good rule of thumb for exhaust upgrading? In a word - VELOCITY. I'm sure that all of you have at one time used a garden hose w/o a spray nozzle on it. If you let the water just run unrestricted out of the house it flows at a rather slow rate. However, if you take your finger and cover part of the opening, the water will flow out at a much much faster rate.

The astute exhaust designer knows that you must balance flow capacity with velocity. You want the exhaust gases to exit the chamber and speed along at the highest velocity possible - you want a FAST exhaust stream. If you have two pulses of equal volume, one in a 2" pipe and one in a 3" pipe, the pulse in the 2" pipe will be traveling considerably FASTER than the pulse in the 3" pipe. While it is true that the narrower the pipe, the higher the velocity of the exiting gases, you want make sure the pipe is wide enough so that there is as little backpressure as possible while maintaining suitablehttp://www.thumpertalk.com/forum/showthread.php?t=659727# velocity. Backpressure in it's most extreme form can lead to reversion of the stream - that is to say the exhaust flows backwards, which is not good. The trick is to have a pipe that that is as narrow as possible while having as close to zero backpressure as possible at the RPM range you want your power band to be located at. A smaller pipe diameter will produce higher exhaust velocities at a lower RPM but create unacceptably high amounts of backpressure at high rpm. Thus if your powerband is located 2-3000 RPM you'd want a narrower pipe than if your powerband is located at 8-9000RPM.

And:

Exhaust Scavenging

When an engine starts its exhaust stroke, the piston moves up the cylinder bore, decreasing the total chamber volume. When the exhaust valve opens, the high pressure exhaust gas escapes into the exhaust manifold or header, creating an exhaust pulse comprising three main parts: The high-pressure head is created by the large pressure difference between the exhaust in the combustion chamber and the atmospheric pressure outside of the exhaust system. As the exhaust gases equalize between the combustion chamber and the atmosphere, the difference in pressure decreases and the exhaust velocity decreases. This forms the medium-pressure body component of the exhaust pulse. The remaining exhaust gas forms the low-pressure tail component. This tail component may initially match ambient atmospheric pressure, but the momentum of the high- and medium- pressure components reduces the pressure in the combustion chamber to a lower-than-atmospheric level. This relatively low pressure helps to extract all the combustion products from the cylinder and induct the intake charge during the overlap period when both intake and exhaust valves are partially open. The effect is known as scavenging. Length, cross-sectional area, and shaping of the exhaust ports and pipeworks influences the degree of scavenging effect, and the engine speed range over which scavenging occurs.
The magnitude of the exhaust scavenging effect is a direct function of the velocity of the high and medium pressure components of the exhaust pulse. Performance headers work to increase the exhaust velocity as much as possible. One technique is tuned-length primary tubes. This technique attempts to time the occurrence of each exhaust pulse, to occur one after the other in succession while still in the exhaust system. The lower pressure tail of an exhaust pulse then serves to create a greater pressure difference between the high pressure head of the next exhaust pulse, thus increasing the velocity of that exhaust pulse. In V6 and V8 engines where there is more than one exhaust bank, Y-pipes and X-pipes work on the same principle of using the low pressure component of an exhaust pulse to increase the velocity of the next exhaust pulse.
Great care must be used when selecting the length and diameter of the primary tubes. Tubes that are too large will cause the exhaust gas to expand and slow down, decreasing the scavenging effect. Tubes that are too small will create exhaust flow resistance which the engine must work to expel the exhaust gas from the chamber, reducing power and leaving exhaust in the chamber to dilute the incoming intake charge. Since engines produce more exhaust gas at higher speeds, the header(s) are tuned to a particular engine speed range according to the intended application. Typically, wide primary tubes offer the best gains in power and torque at higher engine speeds, while narrow tubes offer the best gains at lower speeds.
Many headers are also resonance tuned, to utilize the low-pressure reflected wave rarefaction pulse which can help scavenging the combustion chamber during valve overlap. This pulse is created in all exhaust systems each time a change in density occurs, such as when exhaust merges into the collector. For clarification, the rarefaction pulse is the technical term for the same process that was described above in the "head, body, tail" description. By tuning the length of the primary tubes, usually by means of resonance tuning, the rarefaction pulse can be timed to coincide with the exact moment valve overlap occurs. Typically, long primary tubes resonate at a lower engine speed than short primary tubes.
Some modern exhaust headers are available with a ceramic coating. This coating serves to prohibit rust and to reduce the amount of heat radiated into the engine bay. The heat reduction will help prevent intake manifold heat soak, which will decrease the temperature of the air entering the engine.


At my initial post on this thread, I clearly say that I am looking for the power gain of this mod.

This what you just posted is a copy-paste, which also verifies what I am trying to do. Did you read it?
I will keep the stock backpressure at the low rpms, and make zero backpressure at higher rpms.


Does it sound that strange??

Anyhing that comes from your personal experience?




.
 

plumcrazy

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The HP gains are going to be epic. Pretty much the same as bolting on a supercharger. Think of all the time and money you will have saved too. This is a great idea!
 

DanielR

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Why not just do a set of THESE ? Seems like a simpler approach that will get you to the same place your headed.

For the dense: Sarcasm ON:

You're missing the point. A standard right out of the box proven solution is not as cool as using a wastegate with no boost. I personally have developed a set of exhaust manifold screamer valves. They were designed to replace the exhaust manifold gasket and have electronic valves that open on demand to completely bypass the entire exhaust system. I also installed a set of wastegate screamer valves directly in my hood to vent the pressure/heat and on occasion, fire from under the hood when I open the exhaust manifold screamer valves.

For the dense: Sarcasm OFF:

You cannot help those who are not willing to help themselves. :brick:
 
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tzortzViper

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Cool posts!

So many gurus in this forum...:2tu:


Maybe I am too ******** for this forum... :wrong:





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shine

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And how can I control it?

Electric cutouts use a motor and rocker switch mounted in the cockpit; those are manual where the cable would be run into the cockpit and you'd pull it to physically pull the cutouts open, or push it to close them back. Where you actually mounted it would be up to you.
 

ILLSMOQ

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Electric cutouts use a motor and rocker switch mounted in the cockpit; those are manual where the cable would be run into the cockpit and you'd pull it to physically pull the cutouts open, or push it to close them back. Where you actually mounted it would be up to you.


Yes, installing the cable would require some "custom" fabrication, Tortis seems to be up to the challenge.

I'd suggest a tool of this nature --> TOOL

You will find many tools appropriate for your Viper at that online store.:2tu:
 

Mopar Steve

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You must be registered for see images attach


Or maybe this:

You must be registered for see images attach


Maybe make it a Corvette?

You must be registered for see images
 

ViperTony

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I don't understand the point of this modification. :dunno: If it's for a screaming exhaust sound, try these: [media]http://www.youtube.com/watch?v=GI9eIgvjCHo[/media]

If it's for a meaner sounding or performing Viper...stop wasting time and build the engine or install turbos.
 

plumcrazy

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TONY, THANK YOU !!!!!

this mod will hold me over till he gets the screamer mod done. woohoo....autozone, here i come !
 

Phun70

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At my initial post on this thread, I clearly say that I am looking for the power gain of this mod.

This what you just posted is a copy-paste, which also verifies what I am trying to do. Did you read it?
I will keep the stock backpressure at the low rpms, and make zero backpressure at higher rpms.


Does it sound that strange??

Anyhing that comes from your personal experience?




.

Whether or not he copy pasted it, he is correct! You mod will not gain you anything and will probably hurt your power output. If you want personal experience, take it from me, I'm an ASE double master auto technician, I'm also certified in advanced engine and undercar, not to mention 13 other certification classes that I'm not really counting, oh, and I'm a viper tech. I own and operate an auto repair facility and have been turning wrenches on daily drivers and race cars for about 20 years. Is that personal experience enough for you??:eater:
 

shine

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I don't understand the point of this modification. :dunno: If it's for a screaming exhaust sound, try these: [media]http://www.youtube.com/watch?v=GI9eIgvjCHo[/media]

If it's for a meaner sounding or performing Viper...stop wasting time and build the engine or install turbos.

Maybe you mean the Bubb Rubb whistle tips that go WOOOO WOOOOO

[media]http://www.youtube.com/watch?v=Nnzw_i4YmKk[/media]
 

plumcrazy

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that cant be worse than me driving down their street.

but i think they are just being racist. stopping those good citizens from having some fun with the wooooooowooooooooo
 

Omega

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This is a strange idea.. I don't understand the finality off this project..Stupid? Probably..

I can't explain why that's crazy in English language but it's a loose time..
 

Mopar Steve

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tzortzViper, if you are still reading this, and still stopping by, please don't leave. We were just goofing on you a little. I feel bad (a little) that you may have left because we all (most of us) picked on you. I know you are new here, and that is uncomfortable anyway. Viper owners are a very close group, we all try to help one another and we bust chops on each other as well. As a Viper owner you are welcome. Just don't do silly stuff on your first visit.

If I don't speak for everyone go ahead and let's hear it.
 

plumcrazy

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steve, you make all the fun you want, my installer is close to being done with this mod.......I CANT WAIT !

before and after dyno results to come
 

ViperTony

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Actually, I'd like to see it done. Why not? It's his Viper and he can do anything he wants to it. Maybe he's a DIY'r that loves wrenching on his snake.
 
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