3" exhaust is no better than a 2.5"... based on a test by VD
09-17-2003, 02:03 PM
#1
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3" exhaust is no better than a 2.5"... based on a test by VD
I sent an email to Corsa regarding a 3" system for the ZR-1, and this was the response I got back.
Now this is a complete 180 from everything else that has been tested/posted before. What gives?
[Modified by Jeffvette, 11:03 AM 9/17/2003]
Jeff,
Carmen at Vette Doctors dyno tested our 2.5" against a 3" B&B system on a think a 368 cid ZR-1 motor.
The car made 438 HP with our system and 436 with the B&B system. That tells me that we are equal if not better than the B&B system.
At this time, we have no plans for the 3" ZR-1 systems....because of this test down a few years back. If you need Carmens number, I can get that for you.
Thanks,
Jim
Carmen at Vette Doctors dyno tested our 2.5" against a 3" B&B system on a think a 368 cid ZR-1 motor.
The car made 438 HP with our system and 436 with the B&B system. That tells me that we are equal if not better than the B&B system.
At this time, we have no plans for the 3" ZR-1 systems....because of this test down a few years back. If you need Carmens number, I can get that for you.
Thanks,
Jim
[Modified by Jeffvette, 11:03 AM 9/17/2003]
09-17-2003, 02:30 PM
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Re: 3" exhaust is no better than a 2.5"... based on a test by VD (Jeffvette)
Good marketing?? :rolleyes:
Actually,I think it's :bs :D
Actually,I think it's :bs :D
09-17-2003, 03:03 PM
#3
Burning Brakes
Re: 3" exhaust is no better than a 2.5"... based on a test by VD (Jeffvette)
Carmen at Vette Doctors dyno tested our 2.5" against a 3" B&B system on a think a 368 cid ZR-1 motor.
The car made 438 HP with our system and 436 with the B&B system. That tells me that we are equal if not better than the B&B system.
The car made 438 HP with our system and 436 with the B&B system. That tells me that we are equal if not better than the B&B system.
09-17-2003, 03:24 PM
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Re: 3" exhaust is no better than a 2.5"... based on a test by VD (A1990)
Maybe I'm wrong, but don't the 368 put down more HP that this??
09-17-2003, 03:57 PM
#5
Le Mans Master
Re: 3" exhaust is no better than a 2.5"... based on a test by VD (Jeffvette)
most reports I've seen show folks picking up HP with going with a good 3" exh in comparison to 2.5.
I would contact Vette Doctors to see if this is true.
if that HP is referencing RWHP it's a pretty stout 368 that could benefit from a 3" exh.
I would contact Vette Doctors to see if this is true.
if that HP is referencing RWHP it's a pretty stout 368 that could benefit from a 3" exh.
09-17-2003, 05:11 PM
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Re: 3" exhaust is no better than a 2.5"... based on a test by VD (Rkreigh)
I am looking at going to a 3" exhaust to replace my 2.5" system. But I want to keep my Flowmaster mufflers (I just love the sound). If I can find someone here in my area to do it I will post the results.
As for the email you received, Just look at where it came from. Of course their system is just as good if not better than another. Email B&B and see what kind of response you get.
As for the email you received, Just look at where it came from. Of course their system is just as good if not better than another. Email B&B and see what kind of response you get.
09-17-2003, 07:19 PM
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Re: 3" exhaust is no better than a 2.5"... based on a test by VD (Jeffvette)
Jeff:If you use X pipe (Crossover) 2.5" is fine,unless you use a 3' without a X pipe
here is a better descriptions about headers and pipes size
Header Basics by Loren Barnes
In the case of V-8 firing order, the five pulses fire alternately back and forth from left to right collector, giving the ideal 180 degree firing cycle. Then it fires two in succession into the left collector, then two in succession into the right collector. If the proper collector outlet diameter is being used (two sizes larger than primaries) the two pulses in succession load up the collector with more air than it can flow. This results in a very strong midrange torque, but causes the engine to "sign off" early, not reaching its potential peek R.P.M. The improper firing order on a V-8 engine results in the need to use large diameter collectors so the engine will perform well at high R.P.M.s. Unfortunately the large diameter collectors cause a tremendous drop in air velocity, resulting in less scavenging through the entire R.P.M. range.
Often cams are used with extended valve timing to help the exhaust cycling. This results in valve timing overlap (Intake and Exhaust valves both open at T.D.C.) which causes a "Reversion"cycle in the exhaust. When this happens, exhaust actually backs up into the cylinder causing intake air to be pushed back out the intake. This reversion causes "Standoff" (fuel blowing out of the Intake) at low R.P.M.s. This whole improper cycling has resulted in a number of "Cure Alls" to help stop this reversion and standoff.
The plentum intake was created to stop the fuel "Standoff". Then came "Anti Reversionary" Cones in the exhaust tubes, and stepped tube diameter in the header, extended collector lengths and even plentums in the exhaust tubes.
In this chain of events beginning with improper firing order, a series of cures has developed, each one causing a new problem.
The optimum cure to this whole problem is to correct the exhaust firing cycle. The two cylinders that fire in succession into each collector have to be separated. This can be done partially by a "Tri-Y" header, where the four primary tubes from each bank merge into two secondary tubes (separating the two pulses firing in succession) and finally collect into a single collector. This type of header helps, but the two pulses are still coming back together at the collector.
The second optimum cure is to cross the two center tubes from each bank, across the engine running them into the collector on the opposite side. This makes the firing cycle in each collector 180 degrees apart, the same as a four cylinder engine. Once this firing order is achieved, the small collector outlet diameter can be used and the "High Velocity Scavenging" at low R.P.M.s cures the reversion problems and eliminates the need for extreme cam duration.
This sounds so easy, you are probably asking why wasn't this done from the start?
If you have ever seen a set of 180 degree headers you would understand.
On today's cars, with space virtually nonexistent, crossing four tubes either under the oil pan or around the front or rear of the engine presents major problems. On racing applications where it is possible, there is still the problem of keeping the tube length down to a reasonable 32" long. If that's not enough challenge, then try to arrange the tubes into each collector so they fire in a "Rotational Firing" pattern. Then you have, what has been called "A Bundle of Snakes".
Arranging the tubes to fire rotationally adds to the scavenging capabilities. The exhaust gas exiting one tube, passing across the opening of the tube directly beside it, creates more suction on that tube than it would on a tube on the opposite side of the collector.
The next problem is "Turbulence" in the collector. When four round tubes are grouped together in a square pattern, so a collector can be attached, you notice a gapping hole in the center of the four tubes. The standard method in manufacturing headers is to cap this hole off with a square plate. This plate in the center of the four tubes creates dead air space, or turbulence, disrupting the high velocity in the collector. This problem is solved by using a "Merge Collector". This collector is formed from four tubes, cut at approximately an 8 degree angle on two sides. When the tubes are all fitted together they form a collector with a "Pyramid" in the center. This has eliminated the need for the square plate and has taken up some of the volume inside the collector, speeding up the air velocity.
Other methods of curing this problem are: fabricating a pyramid out of sheet metal and welding it over the hole between the tubes, or squaring the tubes on two sides so they fit together forming a "+" weld in the center eliminating the hole all together.
You can see that there are a great many factors that go into making a good header. When the header, intake system, and cam timing are all designed to operate to their maximum in the same R.P.M. range, then you have a "Compatible Combination". This combination can be tuned to deliver maximum power at any desired R.P.M. range.
These are some of the "Basics" you need to know about building a good high performance header. There are many other adjustments that can be made to fine tune a header, but this should give you a basic understanding of how all the components work together.
here is a better descriptions about headers and pipes size
Header Basics by Loren Barnes
In the case of V-8 firing order, the five pulses fire alternately back and forth from left to right collector, giving the ideal 180 degree firing cycle. Then it fires two in succession into the left collector, then two in succession into the right collector. If the proper collector outlet diameter is being used (two sizes larger than primaries) the two pulses in succession load up the collector with more air than it can flow. This results in a very strong midrange torque, but causes the engine to "sign off" early, not reaching its potential peek R.P.M. The improper firing order on a V-8 engine results in the need to use large diameter collectors so the engine will perform well at high R.P.M.s. Unfortunately the large diameter collectors cause a tremendous drop in air velocity, resulting in less scavenging through the entire R.P.M. range.
Often cams are used with extended valve timing to help the exhaust cycling. This results in valve timing overlap (Intake and Exhaust valves both open at T.D.C.) which causes a "Reversion"cycle in the exhaust. When this happens, exhaust actually backs up into the cylinder causing intake air to be pushed back out the intake. This reversion causes "Standoff" (fuel blowing out of the Intake) at low R.P.M.s. This whole improper cycling has resulted in a number of "Cure Alls" to help stop this reversion and standoff.
The plentum intake was created to stop the fuel "Standoff". Then came "Anti Reversionary" Cones in the exhaust tubes, and stepped tube diameter in the header, extended collector lengths and even plentums in the exhaust tubes.
In this chain of events beginning with improper firing order, a series of cures has developed, each one causing a new problem.
The optimum cure to this whole problem is to correct the exhaust firing cycle. The two cylinders that fire in succession into each collector have to be separated. This can be done partially by a "Tri-Y" header, where the four primary tubes from each bank merge into two secondary tubes (separating the two pulses firing in succession) and finally collect into a single collector. This type of header helps, but the two pulses are still coming back together at the collector.
The second optimum cure is to cross the two center tubes from each bank, across the engine running them into the collector on the opposite side. This makes the firing cycle in each collector 180 degrees apart, the same as a four cylinder engine. Once this firing order is achieved, the small collector outlet diameter can be used and the "High Velocity Scavenging" at low R.P.M.s cures the reversion problems and eliminates the need for extreme cam duration.
This sounds so easy, you are probably asking why wasn't this done from the start?
If you have ever seen a set of 180 degree headers you would understand.
On today's cars, with space virtually nonexistent, crossing four tubes either under the oil pan or around the front or rear of the engine presents major problems. On racing applications where it is possible, there is still the problem of keeping the tube length down to a reasonable 32" long. If that's not enough challenge, then try to arrange the tubes into each collector so they fire in a "Rotational Firing" pattern. Then you have, what has been called "A Bundle of Snakes".
Arranging the tubes to fire rotationally adds to the scavenging capabilities. The exhaust gas exiting one tube, passing across the opening of the tube directly beside it, creates more suction on that tube than it would on a tube on the opposite side of the collector.
The next problem is "Turbulence" in the collector. When four round tubes are grouped together in a square pattern, so a collector can be attached, you notice a gapping hole in the center of the four tubes. The standard method in manufacturing headers is to cap this hole off with a square plate. This plate in the center of the four tubes creates dead air space, or turbulence, disrupting the high velocity in the collector. This problem is solved by using a "Merge Collector". This collector is formed from four tubes, cut at approximately an 8 degree angle on two sides. When the tubes are all fitted together they form a collector with a "Pyramid" in the center. This has eliminated the need for the square plate and has taken up some of the volume inside the collector, speeding up the air velocity.
Other methods of curing this problem are: fabricating a pyramid out of sheet metal and welding it over the hole between the tubes, or squaring the tubes on two sides so they fit together forming a "+" weld in the center eliminating the hole all together.
You can see that there are a great many factors that go into making a good header. When the header, intake system, and cam timing are all designed to operate to their maximum in the same R.P.M. range, then you have a "Compatible Combination". This combination can be tuned to deliver maximum power at any desired R.P.M. range.
These are some of the "Basics" you need to know about building a good high performance header. There are many other adjustments that can be made to fine tune a header, but this should give you a basic understanding of how all the components work together.
09-17-2003, 09:18 PM
#8
Team Owner
Re: 3" exhaust is no better than a 2.5"... based on a test by VD (Jeffvette)
Aaron Scott picked up 25-30 rwhp on his 368 when going from a 2.5 inch to a B+B triflo with X-pipe (3 inch system). This is on his dyno for before and after, and he noted that the x-pipe helped quite a bit, but the 3 inch system gave a good 10 rwhp gain or more as well. I've never heard of this test by the Vette doctors, so they should chime in and explain the conditions of the test for scrutiny. :seeya
09-17-2003, 09:26 PM
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Re: 3" exhaust is no better than a 2.5"... based on a test by VD (DDSLT5)
I've never heard of this test by the Vette doctors, so they should chime in and explain the conditions of the test for scrutiny. :seeya
09-18-2003, 11:25 AM
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Re: 3" exhaust is no better than a 2.5"... based on a test by VD (Jeffvette)
It's true, I was there, It was back to back tests, As a matter of fact it was my old 90 That I sold to Carmen.
09-18-2003, 01:14 PM
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Re: 3" exhaust is no better than a 2.5"... based on a test by VD (Phil DeJohn)
The numerical difference is statistically a wash. A 2 hp drop or gain would be irrelevant due to variations incurred even on back to back tests. Plus, add the fact that this is a sample of one. So, I wouldn't get to wrapped up in the test outcome.
On that car, on that day, it didn't make a difference. Maybe the 3 inch system needed a different cal to take advantage of the bigger ID?? Maybe 368's don't need 3.0 inch exhaust. Maybe the 368 Aaron tested was really plugged up before the swap?? To many variations to come to a definitive conclusion.
:cheers:
[Modified by 415LT5, 12:20 PM 9/18/2003]
On that car, on that day, it didn't make a difference. Maybe the 3 inch system needed a different cal to take advantage of the bigger ID?? Maybe 368's don't need 3.0 inch exhaust. Maybe the 368 Aaron tested was really plugged up before the swap?? To many variations to come to a definitive conclusion.
:cheers:
[Modified by 415LT5, 12:20 PM 9/18/2003]
09-18-2003, 01:35 PM
#12
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Re: 3" exhaust is no better than a 2.5"... based on a test by VD (415LT5)
one thing is for sure.. all the big boys running the Big numbers are running the 3" B&B + X Pipe.... :yesnod:
09-18-2003, 03:34 PM
#13
Burning Brakes
Re: 3" exhaust is no better than a 2.5"... based on a test by VD (xsmph)
My car (see sig.) benefited from the 3" B&B's with X pipe. 3mph. in the traps, (no dyno #'s.)
Beware when comparing exhausts. The resonator inlets, and muffler construction on 3" and 2 3/4 systems neck down to create restrictions. that's why I ditched my B&B res.(2 1/2") for an X pipe (3"). IMO, an exhaust will only flow as much as it's most restrictive component.
BTW, at the dragstrip, with the mufflers removed, just headers, no cats, x pipe, and exhaust pipes, this stocker sounds verrry scary :yesnod: :crazy: :crazy: :eek: :eek:
Beware when comparing exhausts. The resonator inlets, and muffler construction on 3" and 2 3/4 systems neck down to create restrictions. that's why I ditched my B&B res.(2 1/2") for an X pipe (3"). IMO, an exhaust will only flow as much as it's most restrictive component.
BTW, at the dragstrip, with the mufflers removed, just headers, no cats, x pipe, and exhaust pipes, this stocker sounds verrry scary :yesnod: :crazy: :crazy: :eek: :eek:
09-18-2003, 04:12 PM
#14
Re: 3" exhaust is no better than a 2.5"... based on a test by VD (Phil DeJohn)
Phil, Did that car have cats on it? If so, I wonder if the cats could have been a factor, because of their restrictive nature, in getting a true comparison between the two. :chevy
09-18-2003, 04:27 PM
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Re: 3" exhaust is no better than a 2.5"... based on a test by VD (fort94z)
Phil, Did that car have cats on it? If so, I wonder if the cats could have been a factor, because of their restrictive nature, in getting a true comparison between the two. :chevy
09-18-2003, 04:43 PM
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Re: 3" exhaust is no better than a 2.5"... based on a test by VD (Phil DeJohn)
I will be getting 3" pipe installed tomorrow along with a X-pipe. I will be using the same Flowmaster mufflers. I will have to go with a SOTP difference until I can get it on the dyno to see if there was any gains.
:cheers:
:cheers:
09-19-2003, 12:28 PM
#17
Le Mans Master
Re: 3" exhaust is no better than a 2.5"... based on a test by VD (Jeffvette)
I could see those results being true if both systems were tested w/ cats and resonators. I'd love to see Corsa do a dual 2.75" or 3" titanium system with an X pipe. :yesnod:
09-19-2003, 07:28 PM
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Re: 3" exhaust is no better than a 2.5"... based on a test by VD (LT4POWR)
All did not go as planned today. I wanted to use my "50" series Flowmasters with the 3" pipe. But the installer called me and told me that it was going to be a problem. The 50 series have a smaller inlet than what I needed. So I went ahead and bought a pair of "40" series Flowmasters. The car now has 3" pipe, a X-pipe, and 40 series Flows. The car is very loud now and it has resonance too. But it sure sounds downright nasty. I haven't had much seat time yet but I plan on taking it out for a romp tonight. I will let you know what I come up with.
BTW anyone looking for a Flowmaster Force II system get in touch with me. It should bolt right up to a header equipped ZR-1, since it came off a header equipped ZR-1.
:cheers:
BTW anyone looking for a Flowmaster Force II system get in touch with me. It should bolt right up to a header equipped ZR-1, since it came off a header equipped ZR-1.
:cheers:
09-19-2003, 10:12 PM
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Re: 3" exhaust is no better than a 2.5"... based on a test by VD (randy_red_texas)
Judging from the amount of resonance the car has I would say they are the original 40 series. I will have to call them to verify.
But it sure does feel like I picked up some power. I have to be very close to 400rw now. I ran second from 50 up to redline and it sure did feel stronger. I will have to try to book some dyno time soon to see what it says. I still need a chip though too. I may have to take a drive up to SGC and let Aaron take care of it. You know the old kill 2 birds with one stone theory.
But it sure does feel like I picked up some power. I have to be very close to 400rw now. I ran second from 50 up to redline and it sure did feel stronger. I will have to try to book some dyno time soon to see what it says. I still need a chip though too. I may have to take a drive up to SGC and let Aaron take care of it. You know the old kill 2 birds with one stone theory.