flowmaster exhaust
03-11-2009, 08:44 PM
#12
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Join Date: 03-08-2008
Location: United States of Texas
Posts: 505
I am not a fan of the Flowmasters
I have had them on my race car and they sounded decent but hurt the power. Look at the design, the air has to go through a maze to get out and that creates backpressure.
My muffler is a Cherry Bomb Vortex 88101? muffler and it has a great sound but not too loud and no backpressure. MUCH better in my opinion. Curly
My muffler is a Cherry Bomb Vortex 88101? muffler and it has a great sound but not too loud and no backpressure. MUCH better in my opinion. Curly
03-11-2009, 10:00 PM
#13
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Join Date: 06-04-2008
Location: Toledo, OH
Posts: 1,882
after lots of research i have found that our engine needs back pressure on a NA system. now if you have a turbo. backpressure is not your friend. of course the biggest source of back pressure on our exhaust is that tiny cat.
03-12-2009, 06:19 AM
#14
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Join Date: 03-08-2008
Location: United States of Texas
Posts: 505
I picked up 2 MPC city and 4 highway.
And why did my car pick up 2 MPG city and 4 or more on the highway?
Maybe if I stick a potatoe in the pipe it will really haul? I completly disagree there is nothing good about backpressure it is a sales pitch to sell you a poorly designed muffler. On my dragrace car it went much faster when I took the Flowmasters off and ran open headers. On my HHR the mileage picked up when I did the muffler. Something must be wrong with my car.
Can ANYONE offer any kind of proof that backpresssure improves performance or mileage? The factory uses the backpressure to help keep it quiet and meet the emmisions requirements building heat in the system to burn off the contaminants. Performane or mileage, I dont think so.
Now it may cause engine codes to come on if you had a really well designed exhaust system and did not calibrate or tune it to it. But I guarentee you it would perform better in every way if it was tuned for the exhaust system.
I hope this does not sound rude but my car picked up when I did the exhaust as I expected it would. And I can see no intellegent reason why it would need any backpressure. Or intake restriction for that matter.
03-12-2009, 03:44 PM
#15
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Join Date: 06-04-2008
Location: Toledo, OH
Posts: 1,882
yes back pressure is a complicated subject. some people say good some people say bad. i should have stated before. "in moderation". I was not trying to say that you were wrong. just too low of back pressure can hurt your performance just like too much. too much back pressure will lead to lower exhaust velocities and leave some exhaust in the cylinder. too little and when you get off the gas there can literally be a vacuum in the exhaust pulling very cold air over you very hot exhaust valve, ending in a bent valve. Take a piece of tin and he it with a blow torch then quench it. it will bend. this is why top fuel drag racers shut down their engines at the finish line so as to not cause catastrophic damage to the engine. On a race engine backpressure = bad. on a street application some is good too much is bad. I will agree with you that backpressure does hurt performance but it keeps bad things from happening. hence why i say back pressure is good, well some back pressure is good
03-12-2009, 05:54 PM
#16
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Join Date: 07-05-2008
Location: Akron Ohio
Posts: 5,464
Flow masters do not rust any more or less than any other steel exhaust.
With the factory putting on Stainless now most of us are spoiled by not having to install a exhaust every 4-5 years like we used to.
Most exhaust companies like Flowmaster offer their lines in Stainless. They are more expensive but if your going to keep the vehicle it pays off in the long run.
My Fiero is factory stainless and 25 years old. Hard to beat that.
The only beef I have is it is hard to make a 4 cylinder sound good. Too often it comes out as a fart in a can sound. A few get it right but many get it so wrong.
With the factory putting on Stainless now most of us are spoiled by not having to install a exhaust every 4-5 years like we used to.
Most exhaust companies like Flowmaster offer their lines in Stainless. They are more expensive but if your going to keep the vehicle it pays off in the long run.
My Fiero is factory stainless and 25 years old. Hard to beat that.
The only beef I have is it is hard to make a 4 cylinder sound good. Too often it comes out as a fart in a can sound. A few get it right but many get it so wrong.
03-12-2009, 07:55 PM
#17
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Join Date: 01-13-2008
Location: Washington State, where it rains
Posts: 4,708
Backpressure: The myth and why it's wrong.
I. Introduction
One of the most misunderstood concepts in exhaust theory is backpressure. People love to talk about backpressure on message boards with no real understanding of what it is and what it's consequences are. I'm sure many of you have heard or read the phrase "Engines need backpressure" when discussing exhaust upgrades. That phrase is in fact completely inaccurate and a wholly misguided notion.
II. Some basic exhaust theory
Your exhaust system is designed to evacuate gases from the combustion chamber quickly and efficently. Exhaust gases are not produced in a smooth stream; exhaust gases originate in pulses. A 4 cylinder motor will have 4 distinct pulses per complete engine cycle, a 6 cylinder has 6 pules and so on. The more pulses that are produced, the more continuous the exhaust flow. Backpressure can be loosely defined as the resistance to positive flow - in this case, the resistance to positive flow of the exhaust stream.
III. 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 exhaust 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 suitable exhaust gas velocity. Backpressure in it's most extreme form can lead to reversion of the exhaust 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. Exhaust pipe diameters are best suited to a particular RPM range. 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.
Many engineers try to work around the RPM specific nature of pipe diameters by using setups that are capable of creating a similar effect as a change in pipe diameter on the fly. The most advanced is Ferrari's which consists of two exhaust paths after the header - at low RPM only one path is open to maintain exhaust velocity, but as RPM climbs and exhaust volume increases, the second path is opened to curb backpressure - since there is greater exhaust volume there is no loss in flow velocity. BMW and Nissan use a simpler and less effective method - there is a single exhaust path to the muffler; the muffler has two paths; one path is closed at low RPM but both are open at high RPM.
IV. So how did this myth come to be?
I often wonder how the myth "Engines need backpressure" came to be. Mostly I believe it is a misunderstanding of what is going on with the exhaust stream as pipe diameters change. For instance, someone with a civic decides he's going to uprade his exhaust with a 3" diameter piping. Once it's installed the owner notices that he seems to have lost a good bit of power throughout the powerband. He makes the connections in the following manner: "My wider exhaust eliminated all backpressure but I lost power, therefore the motor must need some backpressure in order to make power." What he did not realize is that he killed off all his flow velocity by using such a ridiculously wide pipe. It would have been possible for him to achieve close to zero backpressure with a much narrower pipe - in that way he would not have lost all his flow velocity.
V. So why is exhaust velocity so important?
The faster an exhaust pulse moves, the better it can scavenge out all of the spent gasses during valve overlap. The guiding principles of exhaust pulse scavenging are a bit beyond the scope of this doc but the general idea is a fast moving pulse creates a low pressure area behind it. This low pressure area acts as a vacuum and draws along the air behind it. A similar example would be a vehicle traveling at a high rate of speed on a dusty road. There is a low pressure area immediately behind the moving vehicle - dust particles get sucked into this low pressure area causing it to collect on the back of the vehicle. This effect is most noticeable on vans and hatchbacks which tend to create large trailing low pressure areas - giving rise to the numerous "wash me please" messages written in the thickly collected dust on the rear door(s). Article Tools
Please don't compare a wide open full RPM operating motor to a street car on electronics..its apples and oranges...a race car is tuned and run at max power/rpm range..which is quite narrow...total different set of equations.
I. Introduction
One of the most misunderstood concepts in exhaust theory is backpressure. People love to talk about backpressure on message boards with no real understanding of what it is and what it's consequences are. I'm sure many of you have heard or read the phrase "Engines need backpressure" when discussing exhaust upgrades. That phrase is in fact completely inaccurate and a wholly misguided notion.
II. Some basic exhaust theory
Your exhaust system is designed to evacuate gases from the combustion chamber quickly and efficently. Exhaust gases are not produced in a smooth stream; exhaust gases originate in pulses. A 4 cylinder motor will have 4 distinct pulses per complete engine cycle, a 6 cylinder has 6 pules and so on. The more pulses that are produced, the more continuous the exhaust flow. Backpressure can be loosely defined as the resistance to positive flow - in this case, the resistance to positive flow of the exhaust stream.
III. 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 exhaust 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 suitable exhaust gas velocity. Backpressure in it's most extreme form can lead to reversion of the exhaust 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. Exhaust pipe diameters are best suited to a particular RPM range. 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.
Many engineers try to work around the RPM specific nature of pipe diameters by using setups that are capable of creating a similar effect as a change in pipe diameter on the fly. The most advanced is Ferrari's which consists of two exhaust paths after the header - at low RPM only one path is open to maintain exhaust velocity, but as RPM climbs and exhaust volume increases, the second path is opened to curb backpressure - since there is greater exhaust volume there is no loss in flow velocity. BMW and Nissan use a simpler and less effective method - there is a single exhaust path to the muffler; the muffler has two paths; one path is closed at low RPM but both are open at high RPM.
IV. So how did this myth come to be?
I often wonder how the myth "Engines need backpressure" came to be. Mostly I believe it is a misunderstanding of what is going on with the exhaust stream as pipe diameters change. For instance, someone with a civic decides he's going to uprade his exhaust with a 3" diameter piping. Once it's installed the owner notices that he seems to have lost a good bit of power throughout the powerband. He makes the connections in the following manner: "My wider exhaust eliminated all backpressure but I lost power, therefore the motor must need some backpressure in order to make power." What he did not realize is that he killed off all his flow velocity by using such a ridiculously wide pipe. It would have been possible for him to achieve close to zero backpressure with a much narrower pipe - in that way he would not have lost all his flow velocity.
V. So why is exhaust velocity so important?
The faster an exhaust pulse moves, the better it can scavenge out all of the spent gasses during valve overlap. The guiding principles of exhaust pulse scavenging are a bit beyond the scope of this doc but the general idea is a fast moving pulse creates a low pressure area behind it. This low pressure area acts as a vacuum and draws along the air behind it. A similar example would be a vehicle traveling at a high rate of speed on a dusty road. There is a low pressure area immediately behind the moving vehicle - dust particles get sucked into this low pressure area causing it to collect on the back of the vehicle. This effect is most noticeable on vans and hatchbacks which tend to create large trailing low pressure areas - giving rise to the numerous "wash me please" messages written in the thickly collected dust on the rear door(s). Article Tools
Please don't compare a wide open full RPM operating motor to a street car on electronics..its apples and oranges...a race car is tuned and run at max power/rpm range..which is quite narrow...total different set of equations.
03-12-2009, 08:07 PM
#18
Senior Member
Join Date: 03-08-2008
Location: United States of Texas
Posts: 505
I guess we just agree to disagree
Not once have I ever seen a motor that even had open headers with no exhaust bend valves and I raced for many years and most everyone ran open headers.
Not once have I ever seen where a car picked up performance or mileage with a more restrictive exhaust. I personally know people who bought into the Flowmaster sales pitch and put mufflers on their race car and everyone lost power and most ended up taking them off. My car was faster when I removed the mufflers. Now the last few years I ran my car with "Mufflers" but they were 4" inside diameter with turn outs in front of rear wheels. Made it much quieter than open headers but nothing you would want on the street.
Carburators and intakes is another urban legend. With my car early in my race career the car books said my car would be fastest with a 535 CFM carb. I set up three carbs all the same and went to the track. The first passes was with a 650 DP Holley then I put a 750 DP Holley on there and it went faster! Then I put a 850 DP Holley on there and it went MUCH faster! 60 Foot times, Miles per hour and everything was better. Then I put the 650 back on there to verify it and it went back to the same ETs as the first passes. That motor was not much more than a stock 350 Chevy.
I also do not believe that too big of and exhaust "Kills" the low end. I just believe that it makes bigger increases in the top end ranges. But if you look at dyno sheets most likely at 2500, to 3500 the hp and torque will still be the same but the top end will really show gains.
I read on one post where someone said when they put the 2.4 intake manifold on their 2.2 it killed the low end. I immediatly felt an increase in the low end just driving my first few miles out of the shop. It helps it more wide open but there is even a few Hp down low with the larger intake.
What happens if you put too big of an exhaust or carb on a car? Nothing! The car just does not use the extra.
What happens when you put too small of an exhaust or carb on a car? The car runs slower and does not get optimum performance or mileage.
A larger less restrictive exhaust will probably make the car louder and I do not like the noise but it will help perrormance and mileage.
Soon I am going to put a 2.4 throttle body on my car and I bet it will help it. The 2.4 is noticably larger than the 2.2 TB. The problem is I will have to do the Trifecta tune at the same time because the map is different for the 2.4 so it will be hard to tell exactly how much the TB helps and how much is the tune.
Not once have I ever seen where a car picked up performance or mileage with a more restrictive exhaust. I personally know people who bought into the Flowmaster sales pitch and put mufflers on their race car and everyone lost power and most ended up taking them off. My car was faster when I removed the mufflers. Now the last few years I ran my car with "Mufflers" but they were 4" inside diameter with turn outs in front of rear wheels. Made it much quieter than open headers but nothing you would want on the street.
Carburators and intakes is another urban legend. With my car early in my race career the car books said my car would be fastest with a 535 CFM carb. I set up three carbs all the same and went to the track. The first passes was with a 650 DP Holley then I put a 750 DP Holley on there and it went faster! Then I put a 850 DP Holley on there and it went MUCH faster! 60 Foot times, Miles per hour and everything was better. Then I put the 650 back on there to verify it and it went back to the same ETs as the first passes. That motor was not much more than a stock 350 Chevy.
I also do not believe that too big of and exhaust "Kills" the low end. I just believe that it makes bigger increases in the top end ranges. But if you look at dyno sheets most likely at 2500, to 3500 the hp and torque will still be the same but the top end will really show gains.
I read on one post where someone said when they put the 2.4 intake manifold on their 2.2 it killed the low end. I immediatly felt an increase in the low end just driving my first few miles out of the shop. It helps it more wide open but there is even a few Hp down low with the larger intake.
What happens if you put too big of an exhaust or carb on a car? Nothing! The car just does not use the extra.
What happens when you put too small of an exhaust or carb on a car? The car runs slower and does not get optimum performance or mileage.
A larger less restrictive exhaust will probably make the car louder and I do not like the noise but it will help perrormance and mileage.
Soon I am going to put a 2.4 throttle body on my car and I bet it will help it. The 2.4 is noticably larger than the 2.2 TB. The problem is I will have to do the Trifecta tune at the same time because the map is different for the 2.4 so it will be hard to tell exactly how much the TB helps and how much is the tune.
03-12-2009, 09:32 PM
#20
Senior Member
Join Date: 01-13-2008
Location: Washington State, where it rains
Posts: 4,708
Though its not a HHr this is an interesting read http://www.corvetteactioncenter.com/...omparison.html
Its nice to be able to run wide open with open headers, but we run the street,have to have a legal exhaust( mostly anyways) so really can't compare wide open race cars to street driven cruisers......I'd like to see a dyno run at cruise compared to wide open..
Its nice to be able to run wide open with open headers, but we run the street,have to have a legal exhaust( mostly anyways) so really can't compare wide open race cars to street driven cruisers......I'd like to see a dyno run at cruise compared to wide open..