X Pipe Pricing
03-05-2005, 02:30 PM
#76
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Originally Posted by Warren928
I got some pricing.
$350 for the x-pipe (aluminized steel?)
$50 for the ceramic coating
$450 for stainless steel plus coating.
Doesn't the porsche have stainless on it already? If so, why would anyone want to put something substandard on theirs? Maybe the ceramic coating eliminates the need for stainless for rust prevention. Not sure on that.
$350 for the x-pipe (aluminized steel?)
$50 for the ceramic coating
$450 for stainless steel plus coating.
Doesn't the porsche have stainless on it already? If so, why would anyone want to put something substandard on theirs? Maybe the ceramic coating eliminates the need for stainless for rust prevention. Not sure on that.
The ceramic coating would be applied to the steel X-pipe. Stainless steel is a lousy heat conductor (that's a good thing in this case), but it's not quite as good an insulator as ceramic. The ceramic coating protects against rust and improves flow rate. Stainless is less fragile, looks pretty, and is a close second to ceramic coatings in terms of flow.
I'll have a look at the Summit catalog tonight to see if they offer any appropriate cats.
Tom Cloutier
03-05-2005, 02:30 PM
#77
3" out of the Y into the turno feeding pipe? Really?
Someone had some info on those dimensions that STS is using. I forgot where that is.
Someone had some info on those dimensions that STS is using. I forgot where that is.
03-05-2005, 02:34 PM
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Originally Posted by BrendanC
But the legs have been changed to suite the exhaust I had made. The transissions are horrible because they were cobbled back together.
That looks pretty good to me. The angles look to be in the ball park. I was concerned that they were really large, but I think you're ok.
Tom Cloutier
03-06-2005, 12:09 AM
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Originally Posted by BrendanC
3" out of the Y into the turno feeding pipe? Really?
Someone had some info on those dimensions that STS is using. I forgot where that is.
Someone had some info on those dimensions that STS is using. I forgot where that is.
I talked with a buddy who owns the Porsche shop where I have my dyno. He thought 2.5" pipe would be fine for a rear mounted turbo where presumably the boost will be relatively low--5-8psi.
Tom Cloutier
03-06-2005, 02:00 PM
#80
I was simply concerned about the volume of the 3" - Would that decrease velocity but allow more boost later on?
03-06-2005, 04:17 PM
#81
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928ntslow,
Thanks for the email and I apologize for the delay. I was a little confused with your description but I will try to answer your question. You want to conserve your gas energy as much as possible and have the smallest angle as possible with the biggest bend radius. Normally the outer gases have to travel faster than the inner gases in a corner but they are rubbing against the pipe wall and all the other layers are trying to go straight too. They bump into each other and cause turbulence. It takes a few inches for the gases to dampen out and return to laminar (straight) flow, so try not to have a corner and a reduction close to each other. The pressure builds up in a corner because of the bouncing between the layers and all the turbulence caused. Ideally you want the gases to even out before they are forced into a reduction in diameter. You can compare gas flow molecules to say a golf ***** in a big pipe and if they are flowing at say 50 ***** per second in a 3" dia pipe, which means every second 50 ***** fly by. To maintain conservation of mass that same 50 ***** per second have to flow in every part of the exhaust system regardless it’s dimension. The ***** keep pilling up and start pushing, so if you reduce the dia. to 2.5" the same amount of gas has to go through. The pressure increases at the transition from 3” to 2.5” and will be higher in the 2.5”. The same amount of 50 ***** per second in the 3” are flowing in the 2.5” however the cross sectional area is reduced and the velocity has to go up to keep up with the same 50 ball per second. If the dia. reduces the flow goes up and because the gases flow faster they rub more on the pipes. The faster speeds cause more problems within the boundary layers and there is more pressure drop. Remember the gas is just like little ***** rubbing against the walls of the pipe and pushing/shoving each other all the way though the pipe.
Carl Pires
Carl Pires
Thanks for the email and I apologize for the delay. I was a little confused with your description but I will try to answer your question. You want to conserve your gas energy as much as possible and have the smallest angle as possible with the biggest bend radius. Normally the outer gases have to travel faster than the inner gases in a corner but they are rubbing against the pipe wall and all the other layers are trying to go straight too. They bump into each other and cause turbulence. It takes a few inches for the gases to dampen out and return to laminar (straight) flow, so try not to have a corner and a reduction close to each other. The pressure builds up in a corner because of the bouncing between the layers and all the turbulence caused. Ideally you want the gases to even out before they are forced into a reduction in diameter. You can compare gas flow molecules to say a golf ***** in a big pipe and if they are flowing at say 50 ***** per second in a 3" dia pipe, which means every second 50 ***** fly by. To maintain conservation of mass that same 50 ***** per second have to flow in every part of the exhaust system regardless it’s dimension. The ***** keep pilling up and start pushing, so if you reduce the dia. to 2.5" the same amount of gas has to go through. The pressure increases at the transition from 3” to 2.5” and will be higher in the 2.5”. The same amount of 50 ***** per second in the 3” are flowing in the 2.5” however the cross sectional area is reduced and the velocity has to go up to keep up with the same 50 ball per second. If the dia. reduces the flow goes up and because the gases flow faster they rub more on the pipes. The faster speeds cause more problems within the boundary layers and there is more pressure drop. Remember the gas is just like little ***** rubbing against the walls of the pipe and pushing/shoving each other all the way though the pipe.
Carl Pires
Carl Pires
03-06-2005, 04:42 PM
#82
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Ok guys/ladies,
I know we all want to see dyno runs to compare results if we have an increase. But that is tough because of the time it takes to change over the exhaust system. However we have to be careful that the ambient temps and humidity as similar on both runs and is the car at the same operating temps? It is a close comparison at best.
An experienced tester can make his/her equipment shine by stacking the odds in their favor, (this is not directed at anyone but just a statement).
In the aerospace industry we do CFD analysis as a guideline but testing would be done too. To get a better comparison you would blow metered air into the two inlets of the exhaust and measure the flow, temp and pressure at the inlet and exit. The greater the delta pressure between the inlet and exhaust the more restrictions you have.
The problems is what pressure does the 928 engine want?
Tom Cloutier can flow air into his system on the bench and change over to “ott’s X pipe” and tell you if there is any significant difference. I suspect you would have to be very different to have a significant change.
Carl Pires
I know we all want to see dyno runs to compare results if we have an increase. But that is tough because of the time it takes to change over the exhaust system. However we have to be careful that the ambient temps and humidity as similar on both runs and is the car at the same operating temps? It is a close comparison at best.
An experienced tester can make his/her equipment shine by stacking the odds in their favor, (this is not directed at anyone but just a statement).
In the aerospace industry we do CFD analysis as a guideline but testing would be done too. To get a better comparison you would blow metered air into the two inlets of the exhaust and measure the flow, temp and pressure at the inlet and exit. The greater the delta pressure between the inlet and exhaust the more restrictions you have.
The problems is what pressure does the 928 engine want?
Tom Cloutier can flow air into his system on the bench and change over to “ott’s X pipe” and tell you if there is any significant difference. I suspect you would have to be very different to have a significant change.
Carl Pires
03-06-2005, 05:09 PM
#83
Drifting
A simple 10 degree change in bends gave us the 15hp difference during our dyno testing, and it was not the inlet or outlet angles being changed.
Louie brought up a good point recently, that I should be dynoing the Dr. Gas using the 2.5" cat back system instead of the factory one. Any thoughts? Do people want the most efficient for the factory exhaust or for an upgraded one?
Louie brought up a good point recently, that I should be dynoing the Dr. Gas using the 2.5" cat back system instead of the factory one. Any thoughts? Do people want the most efficient for the factory exhaust or for an upgraded one?
03-06-2005, 05:16 PM
#84
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Tom,
Thank you for your compliment. I have watched the postings for a while but I decided to try help out with you explanation. I am not an automotive exhaust expert but I do have twenty years in the aerospace industry working on engine bleed air (1200°F), heating and air conditioning for aircraft and military vehicles; both testing/design. The software we use is custom made and classified, however I will talk with the boys at work to see if I can find software that we can buy in the open market. Normally I am used to seeing print outs that show velocities, pressures and temps along the ducting and plenums. The different layers with different colors and you change the geometry and run again.
It has been fun reading all these messages and one of these days I need to change my stock 90 GT with headers and an aftermarket exhaust too.
Respectfully
Carl Pires
Thank you for your compliment. I have watched the postings for a while but I decided to try help out with you explanation. I am not an automotive exhaust expert but I do have twenty years in the aerospace industry working on engine bleed air (1200°F), heating and air conditioning for aircraft and military vehicles; both testing/design. The software we use is custom made and classified, however I will talk with the boys at work to see if I can find software that we can buy in the open market. Normally I am used to seeing print outs that show velocities, pressures and temps along the ducting and plenums. The different layers with different colors and you change the geometry and run again.
It has been fun reading all these messages and one of these days I need to change my stock 90 GT with headers and an aftermarket exhaust too.
Respectfully
Carl Pires
03-06-2005, 06:22 PM
#85
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Keith/Tom,
I agree with Tom…he is a wise guy and knows his stuff.
As each exhaust valves opens it causes a sudden pressure wave and that gas looks for a low pressure place to go to…high pressure to low pressure. The greater the difference in pressure the faster the flow. If the dia of the header is say 1.6” and suddenly it is in a 3” dia. collector the dia. is twice, so the pressure and flow will drop to half. This pressurized gas flowing down the pipe meets the “Y” and wants the path of least resistance and if you have a big “Y” angle then some of the gas will try to go up towards the other collector…the wrong way. This is wasteful and will pressurize the other leg of the exhaust inlet to destroy the scavenging effect and work against the gas trying to get out of the cylinder. If the angle is small the gas flows down through the “Y” without much loss in energy and as it passes it causes a low pressure/vacuum on the other inlet pipe. As it flies past the Y it pulls on the other low pressure gas and the faster it flows the more it pulls on the low pressure gas. As each valve opens this pressure wave bounces from left side to right side, each helping each other pulling/scavenging the gases out of the exhaust valve. I would be wise to keep the velocities as high as possible through the “Y” to help scavenge the gases.
Like Tom said if the collector was smaller say 2.5” then there would be fewer losses from a 1.6” header pipe to a 2.5” collector, however this is a balance and the engine may want a certain pressure. So the only way is to test it and see wish would work better for the 928.
Carl Pires
I agree with Tom…he is a wise guy and knows his stuff.
As each exhaust valves opens it causes a sudden pressure wave and that gas looks for a low pressure place to go to…high pressure to low pressure. The greater the difference in pressure the faster the flow. If the dia of the header is say 1.6” and suddenly it is in a 3” dia. collector the dia. is twice, so the pressure and flow will drop to half. This pressurized gas flowing down the pipe meets the “Y” and wants the path of least resistance and if you have a big “Y” angle then some of the gas will try to go up towards the other collector…the wrong way. This is wasteful and will pressurize the other leg of the exhaust inlet to destroy the scavenging effect and work against the gas trying to get out of the cylinder. If the angle is small the gas flows down through the “Y” without much loss in energy and as it passes it causes a low pressure/vacuum on the other inlet pipe. As it flies past the Y it pulls on the other low pressure gas and the faster it flows the more it pulls on the low pressure gas. As each valve opens this pressure wave bounces from left side to right side, each helping each other pulling/scavenging the gases out of the exhaust valve. I would be wise to keep the velocities as high as possible through the “Y” to help scavenge the gases.
Like Tom said if the collector was smaller say 2.5” then there would be fewer losses from a 1.6” header pipe to a 2.5” collector, however this is a balance and the engine may want a certain pressure. So the only way is to test it and see wish would work better for the 928.
Carl Pires
03-07-2005, 03:31 PM
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Originally Posted by Warren928
Still waiting for x-pipe with cat quotes. I thought that a stainless summit or magnaflow dual unit would be fine, but others think different brands are better. I would like to know why they think this is true, just for research purposes.
There are 163 pages of catalytic converter info on the Summit Racing website. We already know that Random Tech cats cost $250 each and both Magnaflow and Carsound cats cost on the order of $85 - $100. These makes will work on the X-pipe. If you want another type, I'm going to let you do the leg work. You need a cat 4" in diameter and the body of the cat (not including the inlet and outlet pipes, usually about 2" long) must be no longer than 8". Need 2.5" inlet and outlet pipes. Send me some part numbers and I'll check them out.
Tom Cloutier
www.thePowerBroker.net
03-07-2005, 04:20 PM
#87
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Tom/Carl...Thanks for the explanations! I have a single Borla outlet to Daylight. The beginning of the Borla system is a 2.5" single inlet. The MSDS header collectors are 3". Since there is no room for a cat with this configuration, I had a Y pipe made. It is a bad design, so I will be having another fabricated. Because of the distance issue from header collectors to the Borla inlet flange, I will need to have the Borla pipe cut, lengthening the distance between the two. This will allow me to bolt in an aftermarket cat in the future, but in the meantime installing a Y pipe with a nicer angle, closer to a V pipe. This will give the 10 to 15 degree adjoining angles mentioned.
The question is, with all that was mentioned about gas flows, corners reduction, wouldn't it be better to reduce immediately after the 3" header collectors to 2.5" and then a nice long gradual meeting (20" 's or so) of the 2 - 2.5" pipes where they would then enter the Borla system? Wouldn't this allow proper scavenging and a better chance for the exhaust gas velocity to stay the same?
The question is, with all that was mentioned about gas flows, corners reduction, wouldn't it be better to reduce immediately after the 3" header collectors to 2.5" and then a nice long gradual meeting (20" 's or so) of the 2 - 2.5" pipes where they would then enter the Borla system? Wouldn't this allow proper scavenging and a better chance for the exhaust gas velocity to stay the same?
03-08-2005, 11:17 AM
#88
Burning Brakes
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Tom,
Thanks for the reply.
I have a question about the cost of the cats you saw in summit added to the x-pipe pricing.
Will there be an extra charge to weld the cats in besides the actual cost of the units?
Thanks for the reply.
I have a question about the cost of the cats you saw in summit added to the x-pipe pricing.
Will there be an extra charge to weld the cats in besides the actual cost of the units?
03-08-2005, 11:19 AM
#89
Burning Brakes
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Tom,
In regards to the x-pipe with cats:
I guess I was thinking that there is a minus $ in material used for the x-pipe, but a little extra $ in welding time.
In regards to the x-pipe with cats:
I guess I was thinking that there is a minus $ in material used for the x-pipe, but a little extra $ in welding time.