anyone have regrets going with 3" dual exhaust?
02-03-2010, 11:37 AM
#21
Heel & Toe
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my 87' has borla exhaust (2 1/4'' inlet pipe w/ 3'' outlet tips) no cats.
i think they sound great. they do have a lot of drone at lower gears. but i like that sound
sound great when reving, but id love to add some long-tube headers and possibly a cam to give it that nice lope
i think they sound great. they do have a lot of drone at lower gears. but i like that sound
sound great when reving, but id love to add some long-tube headers and possibly a cam to give it that nice lope
02-03-2010, 04:58 PM
#22
Le Mans Master
False.....
If you take a regular v8 say a 80 malibu and hack the exhaust right off and run it wide open(and thats the ultimate flow), it will have considerably less low end power. Its not until you start revving that you start having some grunt. I actualy had that experience on a highish performance level aswell. My Malibu Wagon had a 9.5:1 400ci small block in it. Nice aluminum heads, cammed, performer intake, 675cfm carb, headers. When that car had open headers it had little to no low end. 2.5" true dual, I could roll those tires all day long. So no its not a wives tale.
What you experienced was an effect of a change in collector length as opposed to the "backpressure theory" which is complete BS.
You are correct in that by running open headers you lost power.
You are incorrect in assuming that it was the flow restriction (or lack of restriction) that caused this change.
The reason for tuned length primaries is the same as a tuned collector length (here defined as the exhaust beginning at the collector.) You can alter the efficiency curve of the exhaust system depending on length, open headers (~3" collector length) would require some serious RPM to see benefits with. If you have pipe that is not a flow restriction and you had say a 26" collector, you could make more power without loosing that low end. However, at the power level where that 3" collector has peak efficiency will obviously not be as high with the 26" collector. Like all things, it is give and take.
The moral of the story is, back pressure is not the culprit.
I suggest reading some of David Vizards books for clarification from an expert with tons of experience and a technical background.
Last edited by USAsOnlyWay; 02-03-2010 at 05:01 PM.
02-03-2010, 05:21 PM
#23
Le Mans Master
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Velocity is what matters. All the tests show that the best exhaust on a 350 race use is basically open headers. The hp/tq curve may shift but not decrease. I think the real question is, will the 2.5" have a higher velocity then the 3" or vice versa. Also need to consider x-pipe, type of bends, mufflers, etc. I'd go with the 3" with an x-pipe for room to grow. IMO
Last edited by rickneworleansla; 02-03-2010 at 05:24 PM.
02-03-2010, 06:24 PM
#24
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this is too funny. I had this topic on another forum and I was saying the same thing that all of you are saying about giving up bottom end with too big of pipe and some of the guys that think they know it all said I didnt know what I was talking about. they guy I tried to help wanted a new system for his 92 lt1 and I told him not to go too big with the setup he had. too good when you hear from so many that your not crazy
02-04-2010, 09:59 AM
#25
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St. Jude Donor '10-'11-'12-'13
Anybody know how this sounds on a stock motor the sound clip they supply sucks.
http://www.hottexhaust.com/detail.asp?PRODUCT_ID=16837
thanks for input
http://www.hottexhaust.com/detail.asp?PRODUCT_ID=16837
thanks for input
02-04-2010, 10:27 AM
#26
Safety Car
The OP asked about his exhaust system size, not his header pipe size. No one is suggesting three inch primary pipe size. 
Your Malibu example is just anecdotal evidence. (In science, you have what we call a "sample size of one". Doesn't mean much.) My Corvette does just the opposite of your car. Mine has more power (due to the reduction in exhaust backpressure) when it's uncorked. When it's uncorked, the engine's pumping efficiency increases (at all RPMs), making it more responsive, and increasing power.
It sounds like your Malibu needs the carburetor looked at. A restrictive exhaust increases the magnitude of the intake reversion pulses, causing the intake air to pass by the venturi multiple times, richening the mixture. A low restriction exhaust decreases the amount of intake air enrichment due to the reduction of the reversion pulse magnitude, leaning out the mixture, often resulting in a power loss. This is a carb tuning issue, not a magical phenomenon where choking the exhaust makes (low end) power.
As I said before, an engine makes power by pumping fresh air into the cylinders, and pumping out the combusted air, with minimal restrictions in the intake and exhaust systems. This is why small throttle sizes and small (restrictive) exhausts are not the hot setup to make power.
As I said earlier, some old wive's tales just refuse to die.
Your Malibu example is just anecdotal evidence. (In science, you have what we call a "sample size of one". Doesn't mean much.) My Corvette does just the opposite of your car. Mine has more power (due to the reduction in exhaust backpressure) when it's uncorked. When it's uncorked, the engine's pumping efficiency increases (at all RPMs), making it more responsive, and increasing power.
It sounds like your Malibu needs the carburetor looked at. A restrictive exhaust increases the magnitude of the intake reversion pulses, causing the intake air to pass by the venturi multiple times, richening the mixture. A low restriction exhaust decreases the amount of intake air enrichment due to the reduction of the reversion pulse magnitude, leaning out the mixture, often resulting in a power loss. This is a carb tuning issue, not a magical phenomenon where choking the exhaust makes (low end) power.
As I said before, an engine makes power by pumping fresh air into the cylinders, and pumping out the combusted air, with minimal restrictions in the intake and exhaust systems. This is why small throttle sizes and small (restrictive) exhausts are not the hot setup to make power.
As I said earlier, some old wive's tales just refuse to die.
The 3" exhaust pipes will not loss any power! It is an old wive's tale. The header and collector determine the powerband the best the exhaust pipes can do is to not screw up the scavaging of the header and collector.
02-04-2010, 10:37 AM
#28
I have the 3" magnaflow system on what is essentially a stock LT1. I have no complaints. No dyno comparison but I certainly didnt feel any loss of torque from the drivers seat. Contrary to what a lot of people say about 3" or magnaflow my exhaust is not obnoxiously loud. Sure it is louder then stock but that was kinda the point. It doesn't resonate or drone at any rpm and isn't half as loud as some of those honda boys. The car does have the stock cats/heads/cam and that may be helping to tone it down. I imagine with headwork, cam and longtubes and this exhaust would be much louder.
02-04-2010, 11:39 AM
#29
Melting Slicks
skipping through this thread....noticed there is alot of talk about resonance...
Best way to kill resonance is to extend the tailpipes/tips about 2-3 inches past the rear bumper. It may look a tad odd at some angles, but it works!
Best way to kill resonance is to extend the tailpipes/tips about 2-3 inches past the rear bumper. It may look a tad odd at some angles, but it works!
02-05-2010, 06:40 PM
#30
Instructor
The OP asked about his exhaust system size, not his header pipe size. No one is suggesting three inch primary pipe size.
Your Malibu example is just anecdotal evidence. (In science, you have what we call a "sample size of one". Doesn't mean much.) My Corvette does just the opposite of your car. Mine has more power (due to the reduction in exhaust backpressure) when it's uncorked. When it's uncorked, the engine's pumping efficiency increases (at all RPMs), making it more responsive, and increasing power.
It sounds like your Malibu needs the carburetor looked at. A restrictive exhaust increases the magnitude of the intake reversion pulses, causing the intake air to pass by the venturi multiple times, richening the mixture. A low restriction exhaust decreases the amount of intake air enrichment due to the reduction of the reversion pulse magnitude, leaning out the mixture, often resulting in a power loss. This is a carb tuning issue, not a magical phenomenon where choking the exhaust makes (low end) power.
As I said before, an engine makes power by pumping fresh air into the cylinders, and pumping out the combusted air, with minimal restrictions in the intake and exhaust systems. This is why small throttle sizes and small (restrictive) exhausts are not the hot setup to make power.
As I said earlier, some old wive's tales just refuse to die.
Your Malibu example is just anecdotal evidence. (In science, you have what we call a "sample size of one". Doesn't mean much.) My Corvette does just the opposite of your car. Mine has more power (due to the reduction in exhaust backpressure) when it's uncorked. When it's uncorked, the engine's pumping efficiency increases (at all RPMs), making it more responsive, and increasing power.
It sounds like your Malibu needs the carburetor looked at. A restrictive exhaust increases the magnitude of the intake reversion pulses, causing the intake air to pass by the venturi multiple times, richening the mixture. A low restriction exhaust decreases the amount of intake air enrichment due to the reduction of the reversion pulse magnitude, leaning out the mixture, often resulting in a power loss. This is a carb tuning issue, not a magical phenomenon where choking the exhaust makes (low end) power.
As I said before, an engine makes power by pumping fresh air into the cylinders, and pumping out the combusted air, with minimal restrictions in the intake and exhaust systems. This is why small throttle sizes and small (restrictive) exhausts are not the hot setup to make power.
As I said earlier, some old wive's tales just refuse to die.
Think AIR PUMP, more air IN more air OUT more POWER!
02-05-2010, 10:04 PM
#31
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went with this system:http://www.summitracing.com/search/?...d=scc40r&dds=1
looks good, price was right
no one local would do a custom 3"
only "factory replacement"--y pipes, epa regulations, etc--whatever
ill let you know how it turns out
thanks for all the responses!
matt
looks good, price was right
no one local would do a custom 3"
only "factory replacement"--y pipes, epa regulations, etc--whatever
ill let you know how it turns out
thanks for all the responses!
matt
02-05-2010, 10:30 PM
#32
Team Owner
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St. Jude Donor '05
Pypes makes decent stuff, sure youll be happy.
Everyone has their opinions on sizing, personally I wouldnt use dual 3 on a 350 unless it was pretty wild
Everyone has their opinions on sizing, personally I wouldnt use dual 3 on a 350 unless it was pretty wild
02-05-2010, 10:44 PM
#34
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St. Jude Donor '05
02-06-2010, 11:41 AM
#35
Le Mans Master
I think the problem here is concept.
What is your concept for your application?
A corvette drag car is an oxymoron......corvettes weren't made to be a drag car, but people turn them into drag cars, and then start modifying EVERYTHING to turn it into one.
If you want a drag car, then the exhaust will be considered in the total package for a 12 second WOT track event, and not part throttle operation.
If you have an autocrossing event car, part throttle operation is key, with minimal WOT operation, and intermittant 2-3 second WOT operation is desired.
For a street operated car, the car is mostly part throttle, and is driven slow to fast, and in various gears for undulating periods of time.
How do you want to drive your car?
A. Drag car.......A short race muffler is probably requiredB. autocross....... Torque is king...getting the car to move requires massive amounts of torque quickly and smoothly so the transitions from on the throttle to off the throttle sets up the cylinder conditions to be lean, and ready for fuel and air for the next throttle stab.
This is probably the direction most of us want to go.
C. Street......This is where most of our budgets put us. Unfortunately, if you put $5000 in your car, you have to drive it for 5 years to justify the expense. Some don't have to.
But here we are.....driving on the street. The street car is variety of compromises. One compromise is exhaust. If you put headers on it, and leave the rest of the exhaust alone, it's going to bug you till the day you die......."am I getting all I can out of my exhaust?"
WEll, if you want a drag car, no. If you want an autocrosser, no. If you are going to continue to drive it on the street and enjoy your car, maybe.
How much money do you want to spend?
ok, say you take your car to a dyno shop, and you have your significant other drive your pickup hauling a trailer with various lengths of pipe, and 150 different pairs of various manufacturer's mufflers.
Behind her is a mobile muffler truck able to produce any form of exhaust you desire, and an experienced exhaust fabricator at the wheel.
Ok, you put your car on the dyno, and get a base line.
Now, the exhaust guy says well, we need 3 inch pipes here......and (because this is hypothetical) he pulls out some quiet 3 inch inlet mufflers with dual 2" outlets.
you go through the dyno pulls, and it isn't what you want.....no significant increase or decrease......but where are you making the power?
out come the reducers and different mufflers, and now you modify the pipes, go through myriad muffler changes, X pipe changes, H pipe changes, X and H pipe placement, and change the pipe sizes, muffler placement, etc.
Finally, after about a week or 2, you get what you want. more power.........WEll, is that going to be in the RPM ranges that you desire? WOT? Are you giving up low speed torque for 150 MPH cruising speed?
In the end, you will have made about 5 complete exhaust systems that have to be installed for today's driving experience. You want a drag car, you have an exhaust for that. You want to go make some fast lap times at the track, you have an exhaust for that. You want to go to dinner with your babe, well, you have a set that makes your car quieter than a caddy. etc. etc. etc. because you already spent the thousands to research that, and now you know what you need for each form of driving.
Heaven help you if you change something like heads or injectors or header brands......you will have to start all over again!!!!!!!!! (this is your car manufacturer's position with the EPA)
Everything is a compromise....the car, engine, rear, EXHAUST, ride height, engine placment, transmission, etc.
What you want to do is decide how you will drive the car, what suits you, and your budget,, and go from there.
I for one, have no time to devote a few thousand dollars and a week or two of testing to get the optimum.
If the thing goes like stink, I can stand the noise, and it looks better than all your cars, I'm happy.
Right now, I'm happy
If you are happy, post what you DID, not what you think works for somebody else, and let's dispense with the ideology.
This is what I did
.
What is your concept for your application?
A corvette drag car is an oxymoron......corvettes weren't made to be a drag car, but people turn them into drag cars, and then start modifying EVERYTHING to turn it into one.
If you want a drag car, then the exhaust will be considered in the total package for a 12 second WOT track event, and not part throttle operation.
If you have an autocrossing event car, part throttle operation is key, with minimal WOT operation, and intermittant 2-3 second WOT operation is desired.
For a street operated car, the car is mostly part throttle, and is driven slow to fast, and in various gears for undulating periods of time.
How do you want to drive your car?
A. Drag car.......A short race muffler is probably requiredB. autocross....... Torque is king...getting the car to move requires massive amounts of torque quickly and smoothly so the transitions from on the throttle to off the throttle sets up the cylinder conditions to be lean, and ready for fuel and air for the next throttle stab.
This is probably the direction most of us want to go.
C. Street......This is where most of our budgets put us. Unfortunately, if you put $5000 in your car, you have to drive it for 5 years to justify the expense. Some don't have to.
But here we are.....driving on the street. The street car is variety of compromises. One compromise is exhaust. If you put headers on it, and leave the rest of the exhaust alone, it's going to bug you till the day you die......."am I getting all I can out of my exhaust?"
WEll, if you want a drag car, no. If you want an autocrosser, no. If you are going to continue to drive it on the street and enjoy your car, maybe.
How much money do you want to spend?
ok, say you take your car to a dyno shop, and you have your significant other drive your pickup hauling a trailer with various lengths of pipe, and 150 different pairs of various manufacturer's mufflers.
Behind her is a mobile muffler truck able to produce any form of exhaust you desire, and an experienced exhaust fabricator at the wheel.
Ok, you put your car on the dyno, and get a base line.
Now, the exhaust guy says well, we need 3 inch pipes here......and (because this is hypothetical) he pulls out some quiet 3 inch inlet mufflers with dual 2" outlets.
you go through the dyno pulls, and it isn't what you want.....no significant increase or decrease......but where are you making the power?
out come the reducers and different mufflers, and now you modify the pipes, go through myriad muffler changes, X pipe changes, H pipe changes, X and H pipe placement, and change the pipe sizes, muffler placement, etc.
Finally, after about a week or 2, you get what you want. more power.........WEll, is that going to be in the RPM ranges that you desire? WOT? Are you giving up low speed torque for 150 MPH cruising speed?
In the end, you will have made about 5 complete exhaust systems that have to be installed for today's driving experience. You want a drag car, you have an exhaust for that. You want to go make some fast lap times at the track, you have an exhaust for that. You want to go to dinner with your babe, well, you have a set that makes your car quieter than a caddy. etc. etc. etc. because you already spent the thousands to research that, and now you know what you need for each form of driving.
Heaven help you if you change something like heads or injectors or header brands......you will have to start all over again!!!!!!!!! (this is your car manufacturer's position with the EPA)
Everything is a compromise....the car, engine, rear, EXHAUST, ride height, engine placment, transmission, etc.
What you want to do is decide how you will drive the car, what suits you, and your budget,, and go from there.
I for one, have no time to devote a few thousand dollars and a week or two of testing to get the optimum.
If the thing goes like stink, I can stand the noise, and it looks better than all your cars, I'm happy.
Right now, I'm happy
If you are happy, post what you DID, not what you think works for somebody else, and let's dispense with the ideology.
This is what I did
.
Last edited by coupeguy2001; 02-06-2010 at 12:01 PM.
