I will take two in the stainless steel finish /forums/images/graemlins/whistling.gif
CK5
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Backpressure debate
- Thread starter Leadfoot
- Start date
Tim is correct. Even without heads there is backpressure (atmospheric pressure). I see what you are trying to say as I thought along the same lines before. It's not so much that backpressure (or lack thereof) is what is causing you to run right or wrong, it's "flow". At low rpm's exhaust flows poorly in a large pipe. Air is not moved out of the exhaust effeciently and causes problems for subsequent exhaust coming out of the engine. As rpm's increase and exhaust gas volume increases it starts to flow better through the exhaust helping to "scavenge" (a term that has different meaning to different people) exhaust coming from the motor. To run a very "unrestricted" exhaust requires different tuning than if you run a stock exhaust. Also matching components for the rpm range and operating conditions (i.e. type of exhaust) is essential for the motor to run correctly. Changing one compenent (exhaust) without changing others can actually have negative effects if done improperly.
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Check out some of the LT1 and LS1 sites! There was a write up a guy did about backpressure and he actually measured the backpressure and changed exhaust configurations and did dyno testing to determine what the optimal backpressure was
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Unfortuneately he should have had a flowmeter and not a pressure gauge. When flow is interupted pressure is increased. Restricting the diameter of the pipe can cause poor flow, but so can pipes that are too large. Also I doubt he adjusted the motor correctly (as there are limitations as to how much F.I. motors can compensate without reburned chips or higher flow injectors). I assumed he used pipes that were too large and did not adjust accordingly (this caused poor performance and a crappy torque curve), he then probably went small on the pipe and saw a big increase in low end hp/torque....His findings make sense and I believe for his setup, the low end power was better with small pipes, but it was not Increased backpressure that caused increased performance, but rather better flow (which tells me he was not running as well as he could have if he knew what he was doing).
We also have to keep in mind real world driving and know that everything is a comprimise. Having an exhaust that is optimum at low rpm is not optimum at high rpm without the ability to vary in size. That being said, the exhaust that you may need to run for low end grunt may be different from the exhaust someone else runs for high rpm blasts even if using the same motor. The key is to tune the motor to match the components for optimum performance in the operating conditions regardless of what you use.
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Check out some of the LT1 and LS1 sites! There was a write up a guy did about backpressure and he actually measured the backpressure and changed exhaust configurations and did dyno testing to determine what the optimal backpressure was
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Unfortuneately he should have had a flowmeter and not a pressure gauge. When flow is interupted pressure is increased. Restricting the diameter of the pipe can cause poor flow, but so can pipes that are too large. Also I doubt he adjusted the motor correctly (as there are limitations as to how much F.I. motors can compensate without reburned chips or higher flow injectors). I assumed he used pipes that were too large and did not adjust accordingly (this caused poor performance and a crappy torque curve), he then probably went small on the pipe and saw a big increase in low end hp/torque....His findings make sense and I believe for his setup, the low end power was better with small pipes, but it was not Increased backpressure that caused increased performance, but rather better flow (which tells me he was not running as well as he could have if he knew what he was doing).
We also have to keep in mind real world driving and know that everything is a comprimise. Having an exhaust that is optimum at low rpm is not optimum at high rpm without the ability to vary in size. That being said, the exhaust that you may need to run for low end grunt may be different from the exhaust someone else runs for high rpm blasts even if using the same motor. The key is to tune the motor to match the components for optimum performance in the operating conditions regardless of what you use.
backcountry
1/2 ton status
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All engines are not created equal nor are they built the same. Every combination you try will equal different results. One cannot say that in every instance that a larger exhaust system will automatically improve your performance by the reduction of backpressure.
In racing for example: Engines that are professionally built are “fine tuned” for their intended application. This not only includes experiencing with different components and machine work to gain optimal performance, but also header tubing sizes, lengths, coatings, bends etc. Larger is not always better for every application. /forums/images/graemlins/peace.gif
In racing for example: Engines that are professionally built are “fine tuned” for their intended application. This not only includes experiencing with different components and machine work to gain optimal performance, but also header tubing sizes, lengths, coatings, bends etc. Larger is not always better for every application. /forums/images/graemlins/peace.gif
84_Chevy_K10
Banned
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All engines are not created equal nor are they built the same. Every combination you try will equal different results. One cannot say that in every instance that a larger exhaust system will automatically improve your performance by the reduction of backpressure.
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Nonsense. All engines operate on the same principle. Anything you can do to reduce backpressure and maintain exhaust velocity will increase performance.
Although we all know that too large will cut flow and velocity, I don't think I've ever seen someone build an exhaust system that I thought would cut power due to being too large. Maybe 3" duals on a small block in a truck or something, but 3" is a bitch to bend so most shops won't touch it anyway. I'm still not convinced 2 1/2" duals on a 305 is too much. Once you factor in the bends which restrict flow as the diameter decreases, I think that 2 1/2" duals are ideal for any decent small block, even in a truck.
The reason the need for a larger system is typically there is because factory exhaust systems in the past especially, were very restrictive.
Guys in the, "backpressure is good" club:
Give it up already. Learn the theory and you'll realize you're wrong. There are a lot of factors that go into producing a well tuned exhaust system, but there is one that is consistant. That is that backpressure is bad and cuts your power throughout the RPM range.
All engines are not created equal nor are they built the same. Every combination you try will equal different results. One cannot say that in every instance that a larger exhaust system will automatically improve your performance by the reduction of backpressure.
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Nonsense. All engines operate on the same principle. Anything you can do to reduce backpressure and maintain exhaust velocity will increase performance.
Although we all know that too large will cut flow and velocity, I don't think I've ever seen someone build an exhaust system that I thought would cut power due to being too large. Maybe 3" duals on a small block in a truck or something, but 3" is a bitch to bend so most shops won't touch it anyway. I'm still not convinced 2 1/2" duals on a 305 is too much. Once you factor in the bends which restrict flow as the diameter decreases, I think that 2 1/2" duals are ideal for any decent small block, even in a truck.
The reason the need for a larger system is typically there is because factory exhaust systems in the past especially, were very restrictive.
Guys in the, "backpressure is good" club:
Give it up already. Learn the theory and you'll realize you're wrong. There are a lot of factors that go into producing a well tuned exhaust system, but there is one that is consistant. That is that backpressure is bad and cuts your power throughout the RPM range.
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One cannot say that in every instance that a larger exhaust system will automatically improve your performance by the reduction of backpressure
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if the piston has to push against extra pressure on the exhaust stroke then the wasted motoring power goes way up.
racing tuned exhaust systems try and create a vacuum in the exhaust when the exhaust valve is open and the piston is rising.
that is the purpose of tuned headers.
length of primary pipe determines rpm range much like a quarter wave resonance tuned intake manifold
there is even more to gain in many race motors by reducing exhaust valve lift as it is waste of motor friction to lift an exhaust valve too far off the seat
you need just enough to allow the piston to rise on the exhaust stroke with as little cylinder pressure as possible
One cannot say that in every instance that a larger exhaust system will automatically improve your performance by the reduction of backpressure
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if the piston has to push against extra pressure on the exhaust stroke then the wasted motoring power goes way up.
racing tuned exhaust systems try and create a vacuum in the exhaust when the exhaust valve is open and the piston is rising.
that is the purpose of tuned headers.
length of primary pipe determines rpm range much like a quarter wave resonance tuned intake manifold
there is even more to gain in many race motors by reducing exhaust valve lift as it is waste of motor friction to lift an exhaust valve too far off the seat
you need just enough to allow the piston to rise on the exhaust stroke with as little cylinder pressure as possible
supersize75k5
OrganDonorRacing.com
hmmm good reading
84_Chevy_K10
Banned
Since we're revisiting this thread once again, I'll force my opinions on you guys one more time and pick apart a few more myths.
Keep in mind also that more VE doesn't necessarily mean more fuel burned or injected. Your right foot detirmines this, and being able to maintain speed with less throttle = more economy for a given cruising speed. This is why VE is your friend no matter what--it will produce better economy at the gas pump and more power at the dyno.
I don't like this statement. To absolutely state that running open headers will hurt low end performance is false. Typically all the pipe that is necesary to produce scavenging is a set of well tuned headers. Beyond that, everything is restriction. This can be argued due to tuning, but the moral of the story is that a more efficient exhaust system will make more power throughout the RPM range. I doubt that a set of 1 1/2" open headers on a small block will produce less torque than the same set with an exhaust system. A set of 1 7/8" primary headers on a mild small block vs. a set of 1 1/2" or 1 5/8" primaries with an exhaust system and this arguement may hold true.
This statement is false. If you have burned valves from an efficient exhaust system, the only thing that is wrong is your tuning. Running open headers in and of itself on an otherwise healthy engine is not going to cause burned valves, that statement is false.
I don't like this statement either. Running open exhaust really doesn't call for a richer fuel mixture. The ideal fuel mixture is similar for both an engine with open headers and one with a full exhaust system. The difference is that you'll likely need larger jets/smaller metering rods with open headers is that the engine has become more volumetrically efficient and thus needs more fuel to maintain the fuel mixture that it had been at previously. Running open exhaust doesn't lean your fuel mixture directly--it's the resulting increase in exhaust efficiency and, thus, volumetric efficiency that causes a lean fuel mixture.
Air is also a fluid by that definition. Also remember that fuel is atomized into the air (ideally anyway) when in the engine so is not in a liquid state (once again, this is idealy....look inside your intake manifold for that brown residue that indicates fuel falling out of suspension on its way to the intake ports for evidence that the ideal situation isn't always the realistic one.
It is important to maintain VE at all RPMs. More volumetric efficiency = more power from the same engine displacement. It's like getting more for your money. It may be increasingly important at slower RPM simply because less overall work is being performed (remember, horsepower is torque over time) but really it's just as important as idle as at the redline.
Keep in mind also that more VE doesn't necessarily mean more fuel burned or injected. Your right foot detirmines this, and being able to maintain speed with less throttle = more economy for a given cruising speed. This is why VE is your friend no matter what--it will produce better economy at the gas pump and more power at the dyno.
True, and not only true, true no matter what the given RPM.
Running an open exhaust or very big chambered exhaust (size if most important at and near the head) lowers VE at low rpms and will cause a reduction in power (torque/hp).This statement is false, but only because it is partly true. Just becase the exhaust is open doesn't mean that it is reducing scavenging effect. To make that statement as an absolute makes it a false statement. In most cases the exact opposite is true, assuming fuel mixture is optimized for the resulting efficiency.
Not really. Scavenging occurs further forward in the exhaust system prior to the header collector. Sizing the pipes to reduce backpressure is most important, since in most cases the optimum length of the exhaust system at the header collector. Since in the real world we have to run an exhaust system that is relatively quiet, that, in itself, is the first tradeoff. Making sure it is as efficient as possible helps us to continue to get more for our money. Of course if the resulting exhaust system doesn't fit our budget, it is reasonable to think that we made trade off optimum efficiency for our pocket book. If it were a research project and not a truck, that may not be true (although sometimes I swear mine is both).
Yes and no. Yes, it'd be nice to have ideal 100% VE without forced induction at all RPM. The reality is that in this day and age we simply don't have the technology to do so. Although this seems harsh, keep in mind that nearly all engines are operated in a relatively narrow powerband anyway....so while it may not put perfect numbers on the dyno every time, that compromise we make really doesn't sacrifice much in the scheme of things.
This statement is false. Without an actual example it's hard to say just how false it is, but the reality is that nearly every engine on the road will be more efficient with an open exhaust.
Or unless they are electronically fuel injected. All fuel injection systems compensate for changing barometric pressure, intake air temperature, humidity, etc. Even EGR flow affects fuel metering. OBD II systems monitor fuel mixture several times per second. It is not unreasonable to think that the computer can compensate for the increased efficiency, the reality is that it can, and it will do so.
This is more a characteristic of the fact that the, "tight" motor rides the fine line of optimal or near optimal tuning while the "sloppy" motor is always sloppy. The tight motor will probably run better all the time, even when the tuning is off slightly simply because most factory engines are VERY sloppy, more so than you realize. Tradeoffs are made by OEs all over the place to assure they can deliver a product that works as advertised without costing some insane figure per unit.
I don't like that statement either. Most stock exhaust systems, especially ours from back in the day, were/are HORRIBLE. A set of headers can greatly increase efficiency on these engines. Obviously newer stuff is closer to optimal from the factory so this is not as true as it is with with the older junk we drive, but it's true to a certain extent with every engine on the road.
I disagree. Manifolds are a poor choice for every vehicle. The only thing good about maniflolds is the price tag--they come installed on your vehicle. A good quality set of headers will make a DRASTIC difference in most cases, even on an otherwise stock engine and exhaust system.
That statement is also false. The exhaust near the heads is most important....you said it yourself. Before the exhaust ever reaches that single 2.5" exhaust system, it has cooled significantly and lost volume. Headers disipate heat better so this is even more true with headers than anything else. The reality is that headers will likely make a very significant difference because of their placement in the exhaust system.
A low restriction muffler on an otherwise stock system, and I'd agree with you, it's likely not making much difference. Headers? They'll likely make what most would consider significant gains no matter what.
I think You will find that this is a poor decision that you have made, but that is my opinion. I can state with nearly 100% certainty that you will have a significant loss in VE.
Wow, did anyone know a post could be so long winded that you can't post it?
Thunder
3/4 ton status
WOW Tim! Your finger must be real sore after that one
I think the "gas" being referred to is exhaust gas, not gasoline. But you're correct, air (and the gases that make it up - nitrogen, oxygen, and all the others) is a fluid by definition.
Your statement above is wrong as you've written it.. As you've stated yourself in other parts of this very thread, the tuning of the engine will determine what effect an exhaust system change will have on a particular engine. If a carbureted engine is tuned for maximum efficiency with a particular exhaust system (for this discussion, I'll define efficiency as extracting the maximum possible amount of power from a given amount of fuel), removing said exhaust system will result in an engine that runs differently, due to a change in the vacuum signal to the carb, lack of exhaust scavenging (if the engine had good headers installed), etc. The same thing will happen to an EFI engine to a lesser extent, unless the computer is capable of a wide range of adjustment WITHOUT a chip or software change.
I agree with the root premise of your statement - an open exhaust is the most efficient exhaust. But for an engine to run most efficiently with an open exhaust, it needs to be tuned for that configuration. Just like any other engine mod - improve one thing in the system, and other things will have to be changed to realize the full benefit of the change(s).
Just my 2 cents.......
dirtwarrior17
Banned
If the best way to run a motor was withouth backpressure nascar would have been runnin straight headers instead of dual exhaust. The only reason u see top fuels runnin straight headers is because of the extreme pressure a nitro burnin supercharged beast throws down.
I know edelbrock or one of the major performance companies did a dyno test to see if a no restriction exhaust would be the best way to run a motor. the motor made more hp with the right amount of backpressure not no backpressure...this is where it gets tricky. Too much you will rob power because it's slowing down air intake, not enough u will rob power because your gettin too much air, best way is to find the middle between the two.
I know edelbrock or one of the major performance companies did a dyno test to see if a no restriction exhaust would be the best way to run a motor. the motor made more hp with the right amount of backpressure not no backpressure...this is where it gets tricky. Too much you will rob power because it's slowing down air intake, not enough u will rob power because your gettin too much air, best way is to find the middle between the two.
smalltruckbigcid
1/2 ton status
Uhhh Nascar runs less than 1 PSI of backpressure and those headers cost about $3000.00 a set (gotta love that stainless steel bling$$$). Headers are a pain, but its not the flow the system provides but the velocity it maintains from front to back, as the exhaust cools the velocity slows and backpressure goes up (not good) if you are using a longer system. To help keep the speed up you should reduce the tube size after the muffler. The coated headers help keep tempertures up by getting a hotter gasand higher gas velocity farther back in the system which can help your O2 sensor work better and will make your cats work better. I'm not saying the cats will flow better just do their job more effienctly. Exhaust manifolds flow like crap. They have to be able to flow 50% of the carb capacity on a V-8 or they are the first cork in the air pump under your hood. A lot of sbc exhaust manifolds flow 250-275 cfm max. That means the 650cfm carb you put on is now a 500-550 cfm carb at best. To figure out the airflow requirement for your carb heres a formula, engine cubic inches X RPM divided by 3456 + CFM input the engine will need. So 350X 2500rpm =875,000 divided by 3456= 253.1 cfm. This formula is short by at least 20% for a big block. I'm starting to ramble so I'll close by saying this, headers will make your engine run better and be more fuel effiecent IF the rest of the engine is tuned to make the most of this add-on and the exhaust has been thought out completely and correctly. Usually neither of those is done right.....
George
George
Me too
Alot is in the interpretation and my poor ability to put my thoughts into the "correct" wording.
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I actually like it a lot: Most people installing headers are doing so after having a motor tuned for a different (most likely more restrictive) exhaust. Going directly to open headers WILL hurt (trust me been there done that MANY times on trucks, demolition derby cars, enduro cars, etc.). You are correct in saying it's not an "absolute", but the chances are in the real world applications that it will hurt (again assuming going from stock exhaust/tune to wide open with no tuning)........and as I stated (and agreed) that it had nothing to do with backpressure, but rather tuning.
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If you read, I agreed with that.......and I never said a burnt valve could be caused by an effecient exhaust system.
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Again, I agreed, but I also realize most people do not buy or drive a vehicle with open headers on a regular basis. They usually have some sort of exhaust. My statements were all (or mostly) made on the assumption that we were comparing going from stock (or stockish) to completely open, which would most likely require tuning for optimum efficiency (sorry if I did not make that clear originally).
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I was refering to the air/fuel mix as a gas, not gasoline (sorry if that was not clear)
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True, VE at all operating rpms is important (as the statement I made following that one stated). I guess I was emphasising the fact that street driven engines are more concerned with VE at idle and off idle than at 9000 RPM's where it will never see (as compared to some racing engines).
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"for a given rpm" was implying any and all rpms.
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This was in response to too small exhaust affecting overall exhaust performance.
I agree and disagree. Yes the most important portion of the exhaust is just off the head especially when you are only running an open header or tuned pipe, BUT the exhaust aft of the header can affect the gasses within the header and therefor affect scavaging and needs to be considered.
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Actually it's true within the current constraints of todays automobiles. Not only would it be extremely loud with thousands of vehicles running around with open exhausts but under hood temps would soar and wiring and electronics would not last.............
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2 b continued
FALSE F.I. systems based off of manifold air pressure cannot compensate that much (they are algorithym based). Yes speed density systems can compensate for changing conditions, but only as far as the sensors and ECM will allow.
Taken from AFI:
What is meant by speed density and MAF or Mass Air Flow?
SPEED DENSITY-- Speed density is a control algorithm which "infers" the amount of air flow into an engine. Incorporating a MAP sensor (manifold absolute pressure), and measuring the engine RPM's (speed) airflow is calculated. Programmed into the ECM (electronic control module) is a volumetric efficiency table for each specific engine application. This table compares the current engine conditions (speed & pressure or vacuum) and outputs a calculated air flow value. This can now be used to insure the proper amount of fuel based upon the air/fuel requirements of the engine. These systems are very cost effective and work well. The downside is that re-calibration can be required with engine modifications
MASS AIR FLOW-- This system incorporates a mass air flow sensor in between the air cleaner and the throttle body on the intake manifold. This sensor directly measures the precise amount of air flowing into the engine and sends this information to the ECM for proper fuel metering. These systems work very well, are very dependable, but are very costly compared to a speed/density system. More sophisticated air flow control and ducting are required for mass air systems
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Agreed. I guess my point was that other changes "can" be made to complimate the installation of headers and realize an even greater improvement in VE and power.
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The key word of yours there is CAN. I wasn't stating that it can't or couldn't, but not likely. I've done it and noticed very little gains several times. You said in one of your replies that the stock system on our rigs sucks, so just adding headers may give some performance but nowhere near it's full potential.
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I don't know where you buy your manifolds, but manifolds are a hell of a lot more expensive than headers. Manufacturers would actually save money if they ran headers from the factory..............actually strike that, they would lose out in warranty work for leaks and cracking. How many times have you had to replace manifold gaskets and how many times have you had to replace header gaskets???
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I actually think it will be a rich decision. I have run a similar truck with manifolds and had more than enough power and I have not had to change a collector gasket in the middle of a snow storm as I had to do twice with headers (and that was using premium aluminum gaskets).
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Anywho, I think for the most part we agree, we just say it in different ways, and we seem to disagree on the finer aspects rather than the basic principles.
I wasn't going to reply, but I had nothing better to do tonight and I thought it would be great mindless reading for anyone interested........
Wow, I think that is my first post that would not all fit in one
dirtwarrior17 said:
With that reasoning, restrictor plates MUST make power, since NASCAR runs them, and carburetors must be the wave of the future! (As well as FWD cars converted to RWD lol)
Just playing, but hopefully you understand that comparing racing that REQUIRES certain components to what is POSSIBLE when not limited by racing body rules is entirely different.
joeshmo473
Registered Member
backpressure
my dad used to work with indy cars, so listen up. backpressure is bad, why?, because it causes the pistons to do more work on the exhaust stroke. most people think they are losing backpressure with large tubing which is true but thats not whats hurting their power, its flow, the ability to use the velocity of the exhaust gases created by headers, etc. to pull the burnt gases out of the cylinders. headers are good for power because they losen up backpressure, but they create scavaging. the optimal exhaust is to have smaller diameter tubing with no restrictions like bends and mufflers. so the exhaust can go straight out the back really fast. i've got an 80 blazer with dual 2 1/4 exhaust with H pipe and no mufflers, just equal length headers and the pipes, its freakin awesome. i lost a tad bit of low end power but thats because i dont have enough velocity at low rpms to create proper scavaging, but mid to top end is ridiculous. so if you want low end power first of all get a merge pipe to get more equal syncronized flow second get some short length headers and small diameter tubing, such as dual 2 inch or single 2.5 inch running straight pipes. its a winning combination on a 350
my dad used to work with indy cars, so listen up. backpressure is bad, why?, because it causes the pistons to do more work on the exhaust stroke. most people think they are losing backpressure with large tubing which is true but thats not whats hurting their power, its flow, the ability to use the velocity of the exhaust gases created by headers, etc. to pull the burnt gases out of the cylinders. headers are good for power because they losen up backpressure, but they create scavaging. the optimal exhaust is to have smaller diameter tubing with no restrictions like bends and mufflers. so the exhaust can go straight out the back really fast. i've got an 80 blazer with dual 2 1/4 exhaust with H pipe and no mufflers, just equal length headers and the pipes, its freakin awesome. i lost a tad bit of low end power but thats because i dont have enough velocity at low rpms to create proper scavaging, but mid to top end is ridiculous. so if you want low end power first of all get a merge pipe to get more equal syncronized flow second get some short length headers and small diameter tubing, such as dual 2 inch or single 2.5 inch running straight pipes. its a winning combination on a 350
eblick
1/2 ton status
Exhaust?
I am running a 350 TBI with stock exhaust but JBA headers. I am ready to upgrade my exhaust but am a bit confused on the best set up. From the last post it sounds like for me straight pipes in a bout 2" diameter and no cat or mufflers would be best. How loud is this setup going to be? Also will my chip be able to adjust for this setting? Thanks for any help.
I am running a 350 TBI with stock exhaust but JBA headers. I am ready to upgrade my exhaust but am a bit confused on the best set up. From the last post it sounds like for me straight pipes in a bout 2" diameter and no cat or mufflers would be best. How loud is this setup going to be? Also will my chip be able to adjust for this setting? Thanks for any help.
joeshmo473
Registered Member
bla
ok here is some stuff to think about the amount of flow you'll have with dual 2 inch is 25.12 because 2 squared times 3.14 equals the inside area then two pipes. the flow with dual 2.25 pipes is 31.7. i dont know how much power you are running but with headers i would lean towards getting 2.25 with cats if you have emmisions to pass. but other than that i would run dual 2 inch pipes out the back WITH H OR X PIPE. the merge pipe will give you low end power. dual two inch pipes will definatly give you good gas mileage and tons of all around power. you cant beat the sound of straight pipes, its clean and powerful. i like my exhaust to be so loud i cant listen to music but yours wont be. flowmasters gave my truck a deeper sound which annoys most people more. you exhaust will be loud outside the truck but not annoying, inside it wont be very loud. i'm sure you will be very pleased with this setup, oh and the pipes wont mess with any computers unless you take out a cat or header with oxygen sensors.
ok here is some stuff to think about the amount of flow you'll have with dual 2 inch is 25.12 because 2 squared times 3.14 equals the inside area then two pipes. the flow with dual 2.25 pipes is 31.7. i dont know how much power you are running but with headers i would lean towards getting 2.25 with cats if you have emmisions to pass. but other than that i would run dual 2 inch pipes out the back WITH H OR X PIPE. the merge pipe will give you low end power. dual two inch pipes will definatly give you good gas mileage and tons of all around power. you cant beat the sound of straight pipes, its clean and powerful. i like my exhaust to be so loud i cant listen to music but yours wont be. flowmasters gave my truck a deeper sound which annoys most people more. you exhaust will be loud outside the truck but not annoying, inside it wont be very loud. i'm sure you will be very pleased with this setup, oh and the pipes wont mess with any computers unless you take out a cat or header with oxygen sensors.
dirtwarrior17
Banned
uhhh do u know what a restrictor plate is? it restricts the amount of fuel/air goin into the manifold, doesn't add backpressure. Its DECREASING BACKPRESSURE BY GIVING THE MOTOR LESS AIR AND FUEL. they run 1 psi of backpressure because the compression ratios, octane, and rpms run so high it doesn't need a lot of backpressure because it moves a lot more air than any normal motor. An everyday streetrod motor will run with more backpressure because it doen't need to move as much air.
Like i said edelbrock did a dyno test with no backpressure too much and in the middle and in the middle was 25 hp more over no backpressure and about 15 hp over too much backpressure.
common sense. more air goes in = more backpressure. Less air(restritor plate) =less back pressure which means less hp. The main reason the plate cuts the power from 800 to 400 is because the motor can't get the fuel it needs to make 800 not because of backpressure. The plates bolt in between the manifold and restrict the cfms.
Like i said edelbrock did a dyno test with no backpressure too much and in the middle and in the middle was 25 hp more over no backpressure and about 15 hp over too much backpressure.
common sense. more air goes in = more backpressure. Less air(restritor plate) =less back pressure which means less hp. The main reason the plate cuts the power from 800 to 400 is because the motor can't get the fuel it needs to make 800 not because of backpressure. The plates bolt in between the manifold and restrict the cfms.
This is pointless to argue, but here goes.
Just because NASCAR does it, does not mean it is optimal. Racing bodies are generally governed by rules that make the cars more competitive, not that which makes them faster. (Indy and tire restrictions, NASCAR with restrictor plates, Circle track cars with Vortec head restrictions, just for a few examples of rules that don't produce faster cars)
NASCAR teams don't run restrictor plates because they want to, but because they have to. It doesn't make them faster.
I would be willing to bet money that NASCAR has restrictions on exhaust, and that every team out there is running as close to that limit as possible. Not by choice, but because they HAVE to by NASCAR rules.
Just because NASCAR does it, does not mean it is optimal. Racing bodies are generally governed by rules that make the cars more competitive, not that which makes them faster. (Indy and tire restrictions, NASCAR with restrictor plates, Circle track cars with Vortec head restrictions, just for a few examples of rules that don't produce faster cars)
NASCAR teams don't run restrictor plates because they want to, but because they have to. It doesn't make them faster.
I would be willing to bet money that NASCAR has restrictions on exhaust, and that every team out there is running as close to that limit as possible. Not by choice, but because they HAVE to by NASCAR rules.
