blinx9900
Super Moderator
- Joined
- Dec 5, 2006
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I have decided to compile both threads into one to clean up the stickies, however for those that wish to view the original threads and discussions that followed them here you are:
The original Exhaust thread can be found here:
http://www.ek9.org/forum/air-intake...velocity-backpressure-all-explained-here.html
The original Intake thread can be found here:
http://www.ek9.org/forum/air-intake...ntake-thread-intake-really-best-i-answer.html
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But first let me say I don’t care what your friend said or what the exhaust shop says or what the v8 drag racer said to you, trust me on this one:
First I will address back pressure:
its simple, back pressure is BAD always BAD! Forget the idea of some engines need back pressure it’s a LIE!! Back pressure means the engine has the waste its HP to push the exhaust out of the system (also known as pumping loss) so you will ALWAYS lose power with back pressure!
Now I will address velocity:
exhaust velocity is what’s important, increase in exhaust velocity is what will free up extra power. now if your wondering how then read on:
Why does velocity free up more power: exhaust velocity is when the exhaust flow is so smooth that each exhaust pulse leaves a vacuum behind to suck out the next pulse so instead of the engine pushing the exhaust out the exhaust itself is sucking out exhaust hence taking the load off the engine and reducing pumping losses. This is where exhaust piping is important, different size piping will give you ideal exhaust velocity at different RPM points. You can’t have perfect velocity throughout your entire rpm range. a smaller piping will give you better velocity down low but too small and your sacrificing top end power because your restricting flow, a large exhaust will give you that ideal velocity higher up in the power band but you may loose some power down low.
Why do you loose power down low with large exhaust: when I say large I mean like having a 3" piping on a stock low revving na 1.6 sohc, what this does is it takes longer for the exhaust to exit the tail pipe because it takes longer to fill up the system, so the engine has to constantly push the exhaust through the system until it gets to the tail pipe. Basically there are more pumping losses. Basically the exhaust has more space to fill before it exits the tailpipe and the engine has to work harder to do that.
So now you know BACK PRESSURE IS BAD! And VELOCITY IS GOOD. but your wondering why so many people think back pressure is good, ill explain that too:
Why people think back pressure is good: in the 1960's racers would put larger pipes on there cars but there cars felt slower sometimes because they where shifting there ideal velocity to a higher rpm, V8's most redlined at 4500-5000rpm in those days so they shifted the point past there engine operating range, then they put much smaller pipes on which gave them a great deal of velocity down low so they had a jump in hp and tq say from 1500-3000 rpm and they thought it was because of back pressure, but it was actually velocity that had increased. Basically it was all a misunderstanding.
How do I know what size to choose to have ideal velocity:
well it’s really complicated it depends on a lot of stuff like your driving style and mods you have etc... So I don’t feel like getting into it, plus everybody has there own preference so I can’t decide what is good for YOU, only you can. And I don’t want to start an argument here.
But blinx I really wanna know your opinion on piping size, I promise not to argue I know it’s just your opinion:
ok fine this is my opinion and preference only. first your exhaust piping size should match the size of your collector on your header (or larger) in most cases, the header collector can always be modded to be larger to match the exhaust size you need, don’t limit yourself to a 2" just cause your collector is 2" that just means you need to cut it off and have a larger collector welded on.
-I think most vtec engines 1.6-1.8 stock or mildly moded (stock internals) are good with 2.5" with a high flow cat or no cat at all, you can get away with a 2.25 if you have NO cat but i just don't see why you would choose such a small exhaust.
-for 1.6-1.8 vtecs with internal work like cams, raised compression, higher redline, port work etc.. I prefer a minimum of 2.5 to 2.75". You can try to step up to 3" if your heavily modded, you might see some gains.
-for 1.9-2.1+ vtecs 3" all the way! B-series 1.9+, H22, K20, or K24 setups should all use 3" for max power, even if the internals are OEM, you will in most cases see gains across the whole power band.
-for turbo Honda’s making 400whp and less 3" if your making under 300whp you could do a 2.5" with no cat but you will make more power with a 3". You can make a lot more than 400whp on a 3" but some people chose to step up to 3.5 or 4" at this point its really preference as ground clearance is heavily sacrificed at this point...
There now next time someone tries to tell you back pressure is good you can educate them
THE END
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So I’ve been thinking lately, a lot of people ask which intake (induction) setup is best, there are a lot of great ones like: mugen, aem, arc, j's, etc... And we always wonder which is better, which is best, that’s always the question "which is best" well im going to answer that, well kind of
Before I go on I just want to say this is not a debate about brand, nor is it a debate about cold air feeds vs short intakes etc...
just like cams, an induction kits performance will depend on other mods, for example if you buy an AEM intake for you civic you may think its great when the motor is stock, but later if you build the motor up it may become restrictive, intake systems like (exhaust systems) are mostly designed for stock to mildly modified vehicles after all they are designed on stock vehicles and all the research and development is done on a stock vehicle.
So now we have a problem, we have an intake that was designed for a stock car, or perhaps a mildly modded car, like with just header/exhaust/decat/ecu. What happens when you get that stroker kit or a ported head, or maybe some cams, or even all of those, then what intake do you use? Well here is the simple answer: you go custom, seriously it’s not as hard as you think.
Most intakes are 2.25" and that works great for a stock motor, but for a motor that has a lot of mods like cams or whatever something bigger is in order, I personally have found that a 3" pipe works A LOT better for most b series engines. just like I described velocity in regards to exhaust flow in my exhaust thread which can be seen here: http://www.ek9.org/forum/air-intake...velocity-backpressure-all-explained-here.html intake flow can be described the same, a smaller pipe will give you that ideal velocity at a lower rpm, a larger pipe will give you ideal velocity at higher rpm. Pipe length also plays a role, a longer intake pipe will give you more top end power while a shorter pipe will give you a little midrange boost, anyways im sure there is some complicated math formula to decide the perfect length and diameter for your intake pipe but im not going to get into all of that.
So now the true answer is there is no such thing as "the best intake" only a good set up for what you have. I personally think most people on this forum will benefit most from a 3" pipe with a velocity stack and filter on the end.
Velocity stacks can be found here:
http://www.bpinitiatives.com/products.html
BLOX Aluminum Velocity Stack - JHPUSA.COM Serving JDM Since 1999
For the BPI stack you can use k&n filter part number RF-1048, the blox stack has a filter that can be purchased with it also made by blox, im not sure if the rf-1048 filter will fit on the blox stack but it should.
as far as getting a 3" intake pipe you can have one made for you, its simple, if you cant have one made you can always buy a cheap short intake made for a usdm 99 Honda civic SI or EX off eBay (usually $40) and use the pipe from that as long as its 3".
Average cost of doing this is $150 (50 for the pipe, 50 for the filter, and 50 for the velocity stack) or less which is cheaper than most intake kits and better in my opinion.
I personally used the BPI velocity stack with the K&N RF-1048 filter when I was NA and I really liked it, blox now makes aluminum versions of that velocity stack for very cheap, I have posted up links to both above.
well I hope you guys find this a little bit helpful and may help your search for the best intake.
THE END.
The original Exhaust thread can be found here:
http://www.ek9.org/forum/air-intake...velocity-backpressure-all-explained-here.html
The original Intake thread can be found here:
http://www.ek9.org/forum/air-intake...ntake-thread-intake-really-best-i-answer.html
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OFFICIAL EXHAUST THREAD
So far I’ve seen A LOT of exhaust questions and A LOT of misconceptions, so im typing this up to clear those up and hopefully some people will learn the truth about exhaust systems back pressure and velocity, I will try to keep this as brief as possible, But first let me say I don’t care what your friend said or what the exhaust shop says or what the v8 drag racer said to you, trust me on this one:
First I will address back pressure:
its simple, back pressure is BAD always BAD! Forget the idea of some engines need back pressure it’s a LIE!! Back pressure means the engine has the waste its HP to push the exhaust out of the system (also known as pumping loss) so you will ALWAYS lose power with back pressure!
Now I will address velocity:
exhaust velocity is what’s important, increase in exhaust velocity is what will free up extra power. now if your wondering how then read on:
Why does velocity free up more power: exhaust velocity is when the exhaust flow is so smooth that each exhaust pulse leaves a vacuum behind to suck out the next pulse so instead of the engine pushing the exhaust out the exhaust itself is sucking out exhaust hence taking the load off the engine and reducing pumping losses. This is where exhaust piping is important, different size piping will give you ideal exhaust velocity at different RPM points. You can’t have perfect velocity throughout your entire rpm range. a smaller piping will give you better velocity down low but too small and your sacrificing top end power because your restricting flow, a large exhaust will give you that ideal velocity higher up in the power band but you may loose some power down low.
Why do you loose power down low with large exhaust: when I say large I mean like having a 3" piping on a stock low revving na 1.6 sohc, what this does is it takes longer for the exhaust to exit the tail pipe because it takes longer to fill up the system, so the engine has to constantly push the exhaust through the system until it gets to the tail pipe. Basically there are more pumping losses. Basically the exhaust has more space to fill before it exits the tailpipe and the engine has to work harder to do that.
So now you know BACK PRESSURE IS BAD! And VELOCITY IS GOOD. but your wondering why so many people think back pressure is good, ill explain that too:
Why people think back pressure is good: in the 1960's racers would put larger pipes on there cars but there cars felt slower sometimes because they where shifting there ideal velocity to a higher rpm, V8's most redlined at 4500-5000rpm in those days so they shifted the point past there engine operating range, then they put much smaller pipes on which gave them a great deal of velocity down low so they had a jump in hp and tq say from 1500-3000 rpm and they thought it was because of back pressure, but it was actually velocity that had increased. Basically it was all a misunderstanding.
How do I know what size to choose to have ideal velocity:
well it’s really complicated it depends on a lot of stuff like your driving style and mods you have etc... So I don’t feel like getting into it, plus everybody has there own preference so I can’t decide what is good for YOU, only you can. And I don’t want to start an argument here.
But blinx I really wanna know your opinion on piping size, I promise not to argue I know it’s just your opinion:
ok fine this is my opinion and preference only. first your exhaust piping size should match the size of your collector on your header (or larger) in most cases, the header collector can always be modded to be larger to match the exhaust size you need, don’t limit yourself to a 2" just cause your collector is 2" that just means you need to cut it off and have a larger collector welded on.
-I think most vtec engines 1.6-1.8 stock or mildly moded (stock internals) are good with 2.5" with a high flow cat or no cat at all, you can get away with a 2.25 if you have NO cat but i just don't see why you would choose such a small exhaust.
-for 1.6-1.8 vtecs with internal work like cams, raised compression, higher redline, port work etc.. I prefer a minimum of 2.5 to 2.75". You can try to step up to 3" if your heavily modded, you might see some gains.
-for 1.9-2.1+ vtecs 3" all the way! B-series 1.9+, H22, K20, or K24 setups should all use 3" for max power, even if the internals are OEM, you will in most cases see gains across the whole power band.
-for turbo Honda’s making 400whp and less 3" if your making under 300whp you could do a 2.5" with no cat but you will make more power with a 3". You can make a lot more than 400whp on a 3" but some people chose to step up to 3.5 or 4" at this point its really preference as ground clearance is heavily sacrificed at this point...
There now next time someone tries to tell you back pressure is good you can educate them
THE END
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OFFICIAL INTAKE THREAD:
blinx's official guide: which intake really is the best? i answer it.So I’ve been thinking lately, a lot of people ask which intake (induction) setup is best, there are a lot of great ones like: mugen, aem, arc, j's, etc... And we always wonder which is better, which is best, that’s always the question "which is best" well im going to answer that, well kind of
Before I go on I just want to say this is not a debate about brand, nor is it a debate about cold air feeds vs short intakes etc...
just like cams, an induction kits performance will depend on other mods, for example if you buy an AEM intake for you civic you may think its great when the motor is stock, but later if you build the motor up it may become restrictive, intake systems like (exhaust systems) are mostly designed for stock to mildly modified vehicles after all they are designed on stock vehicles and all the research and development is done on a stock vehicle.
So now we have a problem, we have an intake that was designed for a stock car, or perhaps a mildly modded car, like with just header/exhaust/decat/ecu. What happens when you get that stroker kit or a ported head, or maybe some cams, or even all of those, then what intake do you use? Well here is the simple answer: you go custom, seriously it’s not as hard as you think.
Most intakes are 2.25" and that works great for a stock motor, but for a motor that has a lot of mods like cams or whatever something bigger is in order, I personally have found that a 3" pipe works A LOT better for most b series engines. just like I described velocity in regards to exhaust flow in my exhaust thread which can be seen here: http://www.ek9.org/forum/air-intake...velocity-backpressure-all-explained-here.html intake flow can be described the same, a smaller pipe will give you that ideal velocity at a lower rpm, a larger pipe will give you ideal velocity at higher rpm. Pipe length also plays a role, a longer intake pipe will give you more top end power while a shorter pipe will give you a little midrange boost, anyways im sure there is some complicated math formula to decide the perfect length and diameter for your intake pipe but im not going to get into all of that.
So now the true answer is there is no such thing as "the best intake" only a good set up for what you have. I personally think most people on this forum will benefit most from a 3" pipe with a velocity stack and filter on the end.
Velocity stacks can be found here:
http://www.bpinitiatives.com/products.html
BLOX Aluminum Velocity Stack - JHPUSA.COM Serving JDM Since 1999
For the BPI stack you can use k&n filter part number RF-1048, the blox stack has a filter that can be purchased with it also made by blox, im not sure if the rf-1048 filter will fit on the blox stack but it should.
as far as getting a 3" intake pipe you can have one made for you, its simple, if you cant have one made you can always buy a cheap short intake made for a usdm 99 Honda civic SI or EX off eBay (usually $40) and use the pipe from that as long as its 3".
Average cost of doing this is $150 (50 for the pipe, 50 for the filter, and 50 for the velocity stack) or less which is cheaper than most intake kits and better in my opinion.
I personally used the BPI velocity stack with the K&N RF-1048 filter when I was NA and I really liked it, blox now makes aluminum versions of that velocity stack for very cheap, I have posted up links to both above.
well I hope you guys find this a little bit helpful and may help your search for the best intake.
THE END.
Last edited:
