What size exhaust & what Mufflers?
10-10-2016, 03:18 PM
#21
Jesus what a mess of a thread.
2.5" duals would probably be ok for the car as it sits...but at some point more power is going to be added and the car will need larger to be optimal...just do it once if you have room for 3" to clear.
Really sick if seeing crap about undersized intake/exhaust "supporting" xxx HP. Well sure a car might make xxx HP through a **** exhaust....but there's still a good chance it will make more with a properly efficient system.
A car doesn't magically go from making 100% of the power possible to not making any more power at all if there is an airflow problem.
2.5" duals would probably be ok for the car as it sits...but at some point more power is going to be added and the car will need larger to be optimal...just do it once if you have room for 3" to clear.
Really sick if seeing crap about undersized intake/exhaust "supporting" xxx HP. Well sure a car might make xxx HP through a **** exhaust....but there's still a good chance it will make more with a properly efficient system.
A car doesn't magically go from making 100% of the power possible to not making any more power at all if there is an airflow problem.
10-11-2016, 09:04 AM
#23
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I appreciate it Thunderstruck, and that is the plan put 3" on and be done since like i said before it will be built bigger faster louder sooner then later. 
10-11-2016, 09:46 AM
#24
I made the mistake of building mine at 2.25", luckily it had cutouts because the car was nearly .3 and 2.5mph faster with them open on that system. Even with 3" duals the car will run a tad faster with them open (we are talking less than a tenth and less than 1 mph though) most likely because I like my chambered Terminator mufflers...if they were a bullet or straight through style muffler it might be different.
I run 2.5" on my truck because it was cheaper and I have no plans to get crazy with the truck. Sounds good, not too loud, no drone, and flows better than the stock exhaust did.
It's all about application and desired results versus budget and sometimes space constraints...some cars simply can't run 3" or larger. But for a high performance application if you can run dual 3" run dual 3". If you have to run a y then run 3" into 3.5" single if possible. Just my $.02 based on real world results, not theoretical "the chart says this is good to 600hp"
I run 2.5" on my truck because it was cheaper and I have no plans to get crazy with the truck. Sounds good, not too loud, no drone, and flows better than the stock exhaust did.
It's all about application and desired results versus budget and sometimes space constraints...some cars simply can't run 3" or larger. But for a high performance application if you can run dual 3" run dual 3". If you have to run a y then run 3" into 3.5" single if possible. Just my $.02 based on real world results, not theoretical "the chart says this is good to 600hp"
10-12-2016, 09:26 PM
#25
This might take hundreds of thousands of dollars, calculus, computer simulation, and dyno time. Not something you can produce in a backyard with a hacksaw and mig welder.
Some say the 'tuning' of exhaust is 'easy'
http://www.eng-tips.com/viewthread.cfm?qid=167504
Knap (Industrial)
4 Jan 07 15:49
Exhaust tuning theory is actually fairly simple, it’s all about getting the negative (and, hence, scavenging) pressure pulse to arrive at the exhaust valve as it is opening. To do this we have to set the pipe lengths and diameters correctly.
The formula for Primary pipe length is:
P = [(850 x ED) / RPM] - 3
Where:
RPM is the engine speed to which the exhaust is being tuned.
ED = 180° plus the number of degrees the exhaust valve opens before BDC.
P = Primary pipe length (on a 4-1 manifold), or Primary pipe length plus Secondary pipe length (on a 4-2-1 manifold), in inches.
Generally road engines will require the manifold to be tuned to the max torque rpm whereas race engines will be tuned to work either at max bhp rpm or a speed midway between the max bhp rpm and max torque rpm.
4 -1 manifolds restrict the the power band whereas 4-2-1 manifolds give better mid-range power but reduce top end power by as much as 5-7%.
Generally speaking with a 4-2-1 manifold the starting point for Primary pipe length is 15 inches, thus Secondary pipe length is P - 15 inches. Changing the length of the Primary pipe tends to rock the power curve around the point of max torque. Shorter Primaries gives more top end power but less mid-range, and vice-versa. There is, however, little change in the peak torque or the rpm where this occurs.
Ideally the Primaries should come off the cylinder head in a straight line for around 4 inches before any turns occur.
Inside diameter of the pipe can be gained from:
ID = ? [cc / {25 x (P + 3)}] x 2.1
Where:
cc = cylinder volume in cc.
P = Primary length in inches.
In some engines it can be useful to have a 'step' between the exhaust port and the Primary (ie the Primary bore is greater than that of the exhaust port). This tends to be the case in engines with rectilinear exhaust ports.
For a 4-2-1 system then, Primary pipe diameter is calculated as above. Secondary pipe diameter is given by:
IDS = ?(ID x ID x 2) x 0.93
Where:
ID = calculated inside diameter of the primary pipes.
The pipe diameter can be used to change the peak torque rpm – a reduction in diameter of 0.125 inches will drop the peak torque rpm by 500-600 rpm in engines over 2 litres and by 650-800 rpm in smaller engives. Increasing the pipe diameter by 0.125 rpm has approximately the opposite effect.
The total length of the Collector and Tailpipe (to the front of the silencer) sould be equal to P + 3 inches (or any full multiple of P + 3 for a road car).
Tailpipe internal diameter is given by:
IDT = ?[(cc x 2) / (P + 3) x 25] x 2
Where P is calculated as above.
Collector length is given by:
CL = [(ID2 – ID3) / 2] x CotA
Where:
ID2 = diameter of Collector inlet
ID3 = diameter of Collector outlet.
CotA = Cotangent of angle of Collector taper (which ideally should be around 7-8° (certainly less than 10°).
The design of the collector should be such that the inlet pipes terminate abruptly otherwise the tuned exhaust pressure wave will carry on into the tailpipe and the calculations done to get the negative scavenging wave back to the exhaust valve on time will all be wrong.
And some say it requires dyno time
evelrod (Automotive)
3 Jan 07 15:25
There is a lot of engineering that goes into all this, but sad to say, in every race car I have built over the years, it comes down to "cut and try" on the dyno.
If someone has a "magic" bullet, I'm ready for it!
3 Jan 07 15:25
There is a lot of engineering that goes into all this, but sad to say, in every race car I have built over the years, it comes down to "cut and try" on the dyno.
If someone has a "magic" bullet, I'm ready for it!
None of them(engineers) will probably ever say "just go 3 inch dual and forget it". that isn't actually a thing, requires no thought, and is based on "hope".
10-12-2016, 11:37 PM
#26
This is amazing. We're talking about exhaust pipe diameter and mufflers, and this guy copy and pukes a bunch of theory about header design. How do you miss the point so badly?
Yes, header size, shape, length, method of merge, collector merge, collector diameter and length a very critical to both wide-open throttle performance and part throttle performance. Everything past the end of the collector serves mostly as a restriction you work to reduce. So, go big and reduce it. A "balance" or "scavenging" pipe can help to give a boost to power, but that has to be tuned and is a bit of a guess and check situation. Most people just put it where it fits or follow some rule of thumb on placement. But, that's not what we're talking about here. Will a gigantic exhaust make your car drive like ****? No. Will it give you more power? No. Will it give you no restriction? Yes! If you don't understand WTF I'm talking about, you should go.
Yes, header size, shape, length, method of merge, collector merge, collector diameter and length a very critical to both wide-open throttle performance and part throttle performance. Everything past the end of the collector serves mostly as a restriction you work to reduce. So, go big and reduce it. A "balance" or "scavenging" pipe can help to give a boost to power, but that has to be tuned and is a bit of a guess and check situation. Most people just put it where it fits or follow some rule of thumb on placement. But, that's not what we're talking about here. Will a gigantic exhaust make your car drive like ****? No. Will it give you more power? No. Will it give you no restriction? Yes! If you don't understand WTF I'm talking about, you should go.
10-13-2016, 09:36 AM
#28
every time. Like WTF is this guy talking about? Is he replying to the right thread? Now I see it's him and expect it. And just gloss over his posts.And I hate his dumb picture. Sorry, but it's annoyingly bad too.
10-14-2016, 01:24 AM
#29
ur not supposed to read that mess. it just goes to show one aspect of what engineers go through to create an exhaust system for a car. If you think you can point and "shoot" with closed eyes to hit a target- think again. This area of engine engineering is all about math, and computer design, and especially for when dealing with N/A applications that need every spare air molecule.
I disagree, if you cut the exhaust off a stock vehicle it will get slower. There is something to be said for hot exhaust gas traveling in a tube away from the engine. And diameter plays a roll with how fast it moves.
I disagree, if you cut the exhaust off a stock vehicle it will get slower. There is something to be said for hot exhaust gas traveling in a tube away from the engine. And diameter plays a roll with how fast it moves.
Last edited by kingtal0n; 10-14-2016 at 01:29 AM.
10-14-2016, 08:03 AM
#30
I disagree, if you cut the exhaust off a stock vehicle it will get slower. There is something to be said for hot exhaust gas traveling in a tube away from the engine. And diameter plays a roll with how fast it moves.
10-14-2016, 10:56 PM
#32
ur not supposed to read that mess. it just goes to show one aspect of what engineers go through to create an exhaust system for a car. If you think you can point and "shoot" with closed eyes to hit a target- think again. This area of engine engineering is all about math, and computer design, and especially for when dealing with N/A applications that need every spare air molecule.
I disagree, if you cut the exhaust off a stock vehicle it will get slower. There is something to be said for hot exhaust gas traveling in a tube away from the engine. And diameter plays a roll with how fast it moves.
You're a terrible troll, but I have to admit I look forward to what senseless comment you're going to make next.
10-21-2016, 07:33 PM
#33
I've already presented the info, it is your job to do what you need to do with it. I can re-emphasis and re-word it, if you want, but thats it.
1. exhaust tube design by professionals is generally either configured via math/computer simulation, or, by trial and error (the point of the previous post, and the only point I wanted to make) or a combination of those. A real pro doesn't point and shoot and call it a day. That can't win any race, in todays world.
2. Hot exhaust gas contains energy which was put there by fuel. You see it in a turbocharger system, working to provide additional power by absorbing the temperature energy the exhaust has to relinquish, and you see it in a scavenging system, either by taking advantage of acoustics or pressure differentials caused by the hot moving gas. In an optimal system of any nature, the exhaust gas will leave at room temperature or colder (once we have extracted the most energy we can from it). A "perfect engine" in physics will show this exact scenario- air entering at ambient and leaves colder, requiring no other energy source to drive the vehicle than what is available in the air to begin with as temperature.
Now you put 1 and 2 together. Math, physics, computers, hot exhaust gas contains energy you want to extract. The system should be configured to this end, not the other end. And this applies to any system where you input energy in the form of dollars (fuel = $$) such as a water heater. You spend so much $$ heating up a tank of water, but if the insulation is terrible, you wind up wasting alot of energy.
1. exhaust tube design by professionals is generally either configured via math/computer simulation, or, by trial and error (the point of the previous post, and the only point I wanted to make) or a combination of those. A real pro doesn't point and shoot and call it a day. That can't win any race, in todays world.
2. Hot exhaust gas contains energy which was put there by fuel. You see it in a turbocharger system, working to provide additional power by absorbing the temperature energy the exhaust has to relinquish, and you see it in a scavenging system, either by taking advantage of acoustics or pressure differentials caused by the hot moving gas. In an optimal system of any nature, the exhaust gas will leave at room temperature or colder (once we have extracted the most energy we can from it). A "perfect engine" in physics will show this exact scenario- air entering at ambient and leaves colder, requiring no other energy source to drive the vehicle than what is available in the air to begin with as temperature.
Now you put 1 and 2 together. Math, physics, computers, hot exhaust gas contains energy you want to extract. The system should be configured to this end, not the other end. And this applies to any system where you input energy in the form of dollars (fuel = $$) such as a water heater. You spend so much $$ heating up a tank of water, but if the insulation is terrible, you wind up wasting alot of energy.
10-22-2016, 09:11 AM
#36
1. exhaust tube design by professionals is generally either configured via math/computer simulation, or, by trial and error (the point of the previous post, and the only point I wanted to make) or a combination of those. A real pro doesn't point and shoot and call it a day. That can't win any race, in todays world.
2. Hot exhaust gas contains energy which was put there by fuel. You see it in a turbocharger system, working to provide additional power by absorbing the temperature energy the exhaust has to relinquish, and you see it in a scavenging system, either by taking advantage of acoustics or pressure differentials caused by the hot moving gas.
.
2. Hot exhaust gas contains energy which was put there by fuel. You see it in a turbocharger system, working to provide additional power by absorbing the temperature energy the exhaust has to relinquish, and you see it in a scavenging system, either by taking advantage of acoustics or pressure differentials caused by the hot moving gas.
.
1 Exhaust design by manufacturers has little to do with performance, Yes it's engineered to flow well but the main emphasis is routing and then sound. They have to make it fit under the car and not hit anything and not hang down and not transfer heat to area's they don't want it. They actually have people who's sole job is to get the sound right, Many cars even have sound pumped into the cabin to make the vehicle more appealing to the driver.
Power is made at the exhaust manifold/header not the rest of the exhaust, Equal length headers would be great but most vehicles whether street or all out race don't have room for them so they have to compromise between tube size/length and available space. Header tuning is done with tube diameter/length and collector size/shape/length.
Anything after the collector is considered a restriction ( That's why real race cars run open headers) so bigger is better but again size becomes an issue.
If full exhaust had the potential to make more power than open headers why don't you see them on all out race cars? The only reason to have any exhaust after the collector on a race car is to keep exhaust gases out of the drivers compartment. Again they see this as a restriction so they engineer a system that will serve that purpose with the least restriction...Not to make more power but to keep from losing it!
Quit quoting header concept/design and trying to apply it to a full exhaust system.... It doesn't apply there!