Header/Sidepipes vs headers true duals
Drifting
Joined: Jun 2011
Posts: 1,704
Likes: 27
So, I have studied mechanical engineering and have a PhD in physics. Moreover, my PhD involved (in part) the expansion of gases through restrictive apertures. Without a doubt, the one who is correct here is Lionel. Backpressure is an unfortunate side-effect of sizing pipes for 'ideal' flow velocity and scavenging. It, in and of itself, is not beneficial.
You notice though that DIESELS run much larger exhaust....hmmmmm.....
That was a nice try though, I still don't buy it.
Le Mans Master
Joined: Oct 2010
Posts: 6,930
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From: melbourne florida
2023 C3 of the Year Finalist - Modified
Pressure and volume work together but are not the same, it works that way with the water supply in your house and the exhaust system in your car.
Take a hose, turn it on full blast, how far does it stream out the hose? Now cover 3/4 of the hose, the water shoots out further but with less volume. Does the pressure go up,? No it stays the same.
An interal combustion engine is nothing but an air pump,intake restriction lose power exhaust restriction, lose power. But it's more noticible at higher speed.
Take a hose, turn it on full blast, how far does it stream out the hose? Now cover 3/4 of the hose, the water shoots out further but with less volume. Does the pressure go up,? No it stays the same.
An interal combustion engine is nothing but an air pump,intake restriction lose power exhaust restriction, lose power. But it's more noticible at higher speed.
Drifting
Joined: Jun 2011
Posts: 1,704
Likes: 27
Man I guess I need to go tear up my engineering degree and pay back the 2 million bucks I've made over the last 25 years. While I'm at it, I need to tell my clients to pull up all those 100's of millions of dollars worth of equipment off the seabed that I've designed over the years. Turns out none of it's any good because I don't know anything. LOL. I'm done ...
Race Director
Joined: Apr 2007
Posts: 11,150
Likes: 890
From: South Western Ontario
So Lionel, what's your point? Why don't all Vettes, Challengers, Camaros, Vipers, etc. come from the factory with dual 4" exhaust then? Have you ever heard of flow velocity? You should work for Borla & change all their performance systems to 3.5" or 4". Let me 'splain it again to you, then you can "correct" me & tell me I'm wrong. Diesels hate backpressure so bigger is better, but gas engines require a proper diameter system to maintain flow velocity, & if the system diameter is too big & too free-flowing, a gas engine will lose bottom-end & midrange performance. Now tell us all this is a load of crap. I have logged hundreds of hours of conversations with racers, musclecar builders, doing it myself, engineers at Ford & Chrysler, etc. to get to the point where I am today. I have logged an extensive history of knowledge & you are basically saying the flow velocity data is garbage. Please share your real-world experience with us all - we are waiting. We want to know what you know.
WTF does flow wanting flow velocity have to do with wanting a restriction in the exhaust?
CAN YOU ANSWER WHY YOU WOULD WANT A RESTRICTION AND NOT FREE FLOWING, AS LONG AS YOU GET THE VELOCITY?
Can you answer the above questions with some actual technical info?
You 100% completely blew it in your rant at the part I highlighted in red. You 100% want free flowing as long as you get the velocities and scavanging required to tune the engine for low-mid range torque.
I also never said flow velocity data is garbage. Learn to read FFS before going on about something I never posted.
Last edited by lionelhutz; Dec 14, 2015 at 10:05 AM.
Race Director
Joined: Apr 2007
Posts: 11,150
Likes: 890
From: South Western Ontario
Man I guess I need to go tear up my engineering degree and pay back the 2 million bucks I've made over the last 25 years. While I'm at it, I need to tell my clients to pull up all those 100's of millions of dollars worth of equipment off the seabed that I've designed over the years. Turns out none of it's any good because I don't know anything. LOL. I'm done ...
You should if you can't comprehend the basic concept that any restriction is a undesirable side effect of the pipe size you picked to get the velocity you want.
Last edited by lionelhutz; Dec 14, 2015 at 10:08 AM.
Safety Car
Joined: Jan 2009
Posts: 4,000
Likes: 299
From: New York
So Lionel, what's your point? Why don't all Vettes, Challengers, Camaros, Vipers, etc. come from the factory with dual 4" exhaust then? Have you ever heard of flow velocity? You should work for Borla & change all their performance systems to 3.5" or 4". Let me 'splain it again to you, then you can "correct" me & tell me I'm wrong. Diesels hate backpressure so bigger is better, but gas engines require a proper diameter system to maintain flow velocity, & if the system diameter is too big & too free-flowing, a gas engine will lose bottom-end & midrange performance. Now tell us all this is a load of crap. I have logged hundreds of hours of conversations with racers, musclecar builders, doing it myself, engineers at Ford & Chrysler, etc. to get to the point where I am today. I have logged an extensive history of knowledge & you are basically saying the flow velocity data is garbage. Please share your real-world experience with us all - we are waiting. We want to know what you know.
I have read through this topic to much dismay.
You in this post ARE NOT stating back pressure , you are now talking about the same thing as lionelhutz . It is NOT back pressure you seek but a flow that interacts in such a way as to promote the evacuation of exhaust gas as efficient as possible.
We have a few guys running open under the car headers and they usually add a section of pipe from 10 to 20 inches after the collector to tune the exhaust and gain more power , it is NOT for back pressure it is to aid the collector in scavenging.
Back pressure in and of itself is a power killer at all RPM , any force used to push the gas past a restriction is force not at the rear wheels. WE dont want restrictions we want a free flowing system that aids in pulling gas down the pipes not slowing it down or limiting how much can pass through
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Race Director
Joined: Apr 2007
Posts: 11,150
Likes: 890
From: South Western Ontario
Where was that? I didn't see it in either of the links. I did see however that the author of the first post notes the importance of velocity. He also knows that the same thing that creates velocity - a smaller pipe or other restriction - also creates backpressure. The two are inseparable. He goes on to say "Thus if your powerband is located 2-3000 RPM you'd want a narrower pipe than if your powerband is located at 8-9000RPM." In other words, the greater backpressure produced by a narrower pipe equates to increased low end torque.
Like I said, it's all about speed and pressure.
Like I said, it's all about speed and pressure.
Try this one,
http://my350z.com/forum/intake-exhau...ml#post7435408
The back pressure DOES NOT create more low end torque. TUNING THE FLOW DOES!
Say a 1.5" pipe creates the best low end torque. Would using a 3" pipe with a 1.5" ID washer over the end create the same torque?
You NEVER EVER, EVER, EVER want back pressure. It is a completely UNDESIRABLE side effect of tuning the exhaust.
Last edited by lionelhutz; Dec 14, 2015 at 03:07 PM.
Drifting
Joined: Jun 2011
Posts: 1,704
Likes: 27
I never once said in my posts that backpressure is good for power. But you do need it in a street motor for low end and mid range. I did say that. And it's a fact. By properly designing an exhaust system, you get the power band you want. Your right and I'm right. We are both right.
Race Director
Joined: Apr 2003
Posts: 19,348
Likes: 654
From: Tampa, Florida
Example... if my engines spinning 6,000 rpm it cant develop velocity until the exhaust is restricted down to a particular diameter.
It's a balance...
Last edited by jim2527; Dec 14, 2015 at 04:36 PM.
Racer
Joined: Jul 2013
Posts: 307
Likes: 19
From: Kirkland WA
Looks like we could've preempted the whole argument by simply agreeing that increased exhaust velocity is not the same as adding backpressure. Backpressure sucks.
Anyway, for the OP I watched all of Lionel's video and now feel very well justified with my earlier optimal recommendation for a moderately built street motor to use Tri-Y headers (and an X-pipe and straight through mufflers, not chambered).
Anyway, for the OP I watched all of Lionel's video and now feel very well justified with my earlier optimal recommendation for a moderately built street motor to use Tri-Y headers (and an X-pipe and straight through mufflers, not chambered).
Race Director
Joined: Apr 2007
Posts: 11,150
Likes: 890
From: South Western Ontario
Yes, you try to tune the exhaust while adding minimum back pressure. Unfortunately, you will end-up with some, but that doesn't mean you want it or you purposely added it.
Yes, on both counts. Back pressure sucks and tri-Y headers can create a really nice wide torque curve.
Looks like we could've preempted the whole argument by simply agreeing that increased exhaust velocity is not the same as adding backpressure. Backpressure sucks.
Anyway, for the OP I watched all of Lionel's video and now feel very well justified with my earlier optimal recommendation for a moderately built street motor to use Tri-Y headers (and an X-pipe and straight through mufflers, not chambered).
Anyway, for the OP I watched all of Lionel's video and now feel very well justified with my earlier optimal recommendation for a moderately built street motor to use Tri-Y headers (and an X-pipe and straight through mufflers, not chambered).
Yes, on both counts. Back pressure sucks and tri-Y headers can create a really nice wide torque curve.
Last edited by lionelhutz; Dec 14, 2015 at 07:22 PM.
Race Director
Joined: Apr 2007
Posts: 11,150
Likes: 890
From: South Western Ontario
Post one piece of evidence which shows that back pressure only, by itself increases the power or torque output of a gasoline fueled engine. Not some one-off example due to a crappy tuned or messed-up engine but where an engine was properly tuned and tested back-to-back with the only change being back pressure. You believe this is fact, so there must be proof.
If not, then post an explanation of why you want back pressure. Not how tuning the piping for flow and scavenging adds unwanted restriction even though it increases power, but how only adding more restriction to exhaust flow helps the engine produce more torque.
Last edited by lionelhutz; Dec 14, 2015 at 07:39 PM.
Race Director
Joined: Jan 2005
Posts: 11,020
Likes: 166
From: Milford Michigan
I have read through this topic to much dismay.
You in this post ARE NOT stating back pressure , you are now talking about the same thing as lionelhutz . It is NOT back pressure you seek but a flow that interacts in such a way as to promote the evacuation of exhaust gas as efficient as possible.
We have a few guys running open under the car headers and they usually add a section of pipe from 10 to 20 inches after the collector to tune the exhaust and gain more power , it is NOT for back pressure it is to aid the collector in scavenging.
Back pressure in and of itself is a power killer at all RPM , any force used to push the gas past a restriction is force not at the rear wheels. WE dont want restrictions we want a free flowing system that aids in pulling gas down the pipes not slowing it down or limiting how much can pass through
You in this post ARE NOT stating back pressure , you are now talking about the same thing as lionelhutz . It is NOT back pressure you seek but a flow that interacts in such a way as to promote the evacuation of exhaust gas as efficient as possible.
We have a few guys running open under the car headers and they usually add a section of pipe from 10 to 20 inches after the collector to tune the exhaust and gain more power , it is NOT for back pressure it is to aid the collector in scavenging.
Back pressure in and of itself is a power killer at all RPM , any force used to push the gas past a restriction is force not at the rear wheels. WE dont want restrictions we want a free flowing system that aids in pulling gas down the pipes not slowing it down or limiting how much can pass through
Race Director
Joined: Jan 2005
Posts: 11,020
Likes: 166
From: Milford Michigan
Hey Lionel, I have a couple questions for you. Give me your take on X-pipes vs. H-pipes - which is better for making power? Also - headers. Full-length, shorties with 45^ dumps, or tri-Y's?
Race Director
Joined: Apr 2007
Posts: 11,150
Likes: 890
From: South Western Ontario
Yep - that's what I'm talking 'bout. Our Canadian "expert" is talking about you can't go too large a diameter to do any harm however. That is incorrect. The optimum diameter promotes scavenging, flow velocity, & minimal backpressure. If the system diameter is too large on a gas motor, you lose flow velocity & scavenging. You also have to figure sound into the equation - what sound are you looking for? Controlling decibels as they relate to the system diameter can also be a challenge.
I never once posted just to use big pipes. I never once posted that flow velocity is not important. You've posted that I have written both of these multiple times now and I'm sick and tired of reading your lies.
Then then the part is bold is apparently your attempt to show how you're the expert coming up with the "truth". It's the same information as I have been posting all along, right down to the part I have been posting all along about wanting to minimize back pressure.
I'm not sure what your problem is exactly. You point blank told me that I was wrong about back pressure not being wanted or required. I will NEVER agree with any claims about an engine needing back pressure. It's a negative side effect of creating an exhaust system, as I have written all along.
Did you fail to notice I didn't make any comments about your post where you explained that you pick the pipe to get the right flow without adding too much back pressure?
Why would I bother with you any more? You constantly write lies about what I posted.
Last edited by lionelhutz; Dec 16, 2015 at 09:45 PM.
