Manifold and exhaust questions
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1)Why do i need to change my banana manifold?What kinds are there and what are the differences ?Is it just bgger/smaller or is there any other differences?If i get very big piping for manifold,will it have any downside?
You need to change ur manifold if ur making monster power, or change to a non standard turbo. There are many different configurations for turbo engines. Basically you want the exhaust gas to arrive at the turbine with as much energy as possible. Therefore you don't want to make ur manifold piping too big. Bigger pipes = lower velocity = colder exhaust, less energy. This will hurt your turbo response.
2)What size pipings should i get ? I heard i should keep my downpipe small to reduce turbo lag.How small should i have it?And why smaller down pipe = less lag ?
3) For midpipe and muffler,is 3" ok if i want to get about 300 WHP on a SR20DET ?Or should i make it 3.5 " ? Will there be any downsides if i get the biggest piping possible ?
4)Another thing i am wondering,i thought Manifold and exhaust is just to EXPEL air from the engine?So why people advice not to make it too big to prevent losing low end/high end ? How can a pipe that expels air make you lose engine power?Wont bigger be better since bigger = less restriction and air can be expelled faster ?
Anything after the turbo should be as big as possible. Turbos work on pressure differential, i.e. pressure before the turbo shud be as high as possible and after the turbo as low as possible. This will increase the rate of flow across the turbine wheel. Faster flow = better response, more power.
Turbo engines are not like NA engines where they need to maximise exhaust gas velocity, so NA engines need specifically calculated exhaust diameters. The turbine wheel is like a big blender that messes up the exhaust pulses. So turbo engines have little or no scavenging.
Therefore bigger = better applies because more flow and reduced pressure after the turbo. No doubt, exhaust velocity is slower and this will affect your off-boost response. But it will bring in boost earlier as well. And that's what you want in a turbo car.
You need to change ur manifold if ur making monster power, or change to a non standard turbo. There are many different configurations for turbo engines. Basically you want the exhaust gas to arrive at the turbine with as much energy as possible. Therefore you don't want to make ur manifold piping too big. Bigger pipes = lower velocity = colder exhaust, less energy. This will hurt your turbo response.
2)What size pipings should i get ? I heard i should keep my downpipe small to reduce turbo lag.How small should i have it?And why smaller down pipe = less lag ?
3) For midpipe and muffler,is 3" ok if i want to get about 300 WHP on a SR20DET ?Or should i make it 3.5 " ? Will there be any downsides if i get the biggest piping possible ?
4)Another thing i am wondering,i thought Manifold and exhaust is just to EXPEL air from the engine?So why people advice not to make it too big to prevent losing low end/high end ? How can a pipe that expels air make you lose engine power?Wont bigger be better since bigger = less restriction and air can be expelled faster ?
Anything after the turbo should be as big as possible. Turbos work on pressure differential, i.e. pressure before the turbo shud be as high as possible and after the turbo as low as possible. This will increase the rate of flow across the turbine wheel. Faster flow = better response, more power.
Turbo engines are not like NA engines where they need to maximise exhaust gas velocity, so NA engines need specifically calculated exhaust diameters. The turbine wheel is like a big blender that messes up the exhaust pulses. So turbo engines have little or no scavenging.
Therefore bigger = better applies because more flow and reduced pressure after the turbo. No doubt, exhaust velocity is slower and this will affect your off-boost response. But it will bring in boost earlier as well. And that's what you want in a turbo car.
So for turbo car,my downpipe and exhaust should be as big as possible for better power ?Then how come some turbos choose to go 2.5" and not 3.5 exhaust?
And Manifold should be as small as possible to maintain the pressure ?
Thanks for response bro.
And Manifold should be as small as possible to maintain the pressure ?
Thanks for response bro.
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Comes a point where going any bigger won't make much difference because your setup aggressive enough. Maybe a 3.5 inch pipe won't fit and so they go for 2.5 inch. Or maybe they just don't know better.
Not that manifold should be as small as possible. It must be the ideal size. Not too large nor too small.
Not that manifold should be as small as possible. It must be the ideal size. Not too large nor too small.
Because in an NA car, getting the best flow and power from the engine depends on most efficient extraction of exhaust gasses. The exhaust pulses from each cylinder have to line up precisely, so that each exhaust pulse meets the tail end of the pulse before it. Do a google search on exhaust pulse tuning if u wanna know more.
As i said earlier, in a turbo engine, the turbine blades basically chop up the exhaust pulses. Since there is very little pulse effect left after that, you get best flow by going big. That's why you need a precise diameter for the manifold piping BEFORE the turbo, and the biggest piping you can get AFTER the turbo.
As i said earlier, in a turbo engine, the turbine blades basically chop up the exhaust pulses. Since there is very little pulse effect left after that, you get best flow by going big. That's why you need a precise diameter for the manifold piping BEFORE the turbo, and the biggest piping you can get AFTER the turbo.
daryl: u have 5" exos rite?
just helping a little here..
Exhaust Basic
http://www.team-integra.net/sections/articles/showArticle.asp?ArticleID=47
Advance Exhaust Tech
http://www.team-integra.net/sections/articles/showArticle.asp?ArticleID=355
warning, you need to read the basic to understand the advance. I only manage to read basic.. lol..
Exhaust Basic
http://www.team-integra.net/sections/articles/showArticle.asp?ArticleID=47
Advance Exhaust Tech
http://www.team-integra.net/sections/articles/showArticle.asp?ArticleID=355
warning, you need to read the basic to understand the advance. I only manage to read basic.. lol..
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quite interesting topic here bout the pressure differential..
here's another site bout pressure differential on turbos,http://www.thedodgegarage.com/turbo_fun.html
here's an example
All else being equal, The amount of work that can be done across an exhaust turbine is determined by the pressure differential at the inlet and outlet_ (in english, raise the turbo inlet pressure, lower the outlet pressure, or both, and you make more power) Pressure is heat, heat is pressure. Raising the inlet pressure is possible, but tough. Lowering the outlet pressure is easy - just bolt on a bigger, free flowing exhaust. I've seen a couple of posts from people who added aftermarket exhausts, who report "my turbo spools up faster now" Well, that's because by lowering the outlet pressure, you increased the pressure differential, and now the exhaust gas can expand more, and do more work. That increased work pushes harder on your turbo, and it spools up faster. You should also see less boost drop at redline, because if an exhaust system is flow-limited, once you pass the flow limit of the system, any additional gasses you try and force through it only raise the outlet pressure. Higher outlet pressure, lower pressure differential, less work, less boost.
then the question:
"What about people who wrap up there downpipes to keep heat in and the exhaust gases hotter after the turbo. The hotter gases travel faster right, and that decreases pressure (good)? Or, the higher retained heat keeps the gases hot and the pressure stays higher and that would lower the pressure differential (bad)?"
Heh, welcome to the real world. :) Both are legit ways of examining the problem, and either scenario is possible, depending on the flow capacity of the exhaust system. If it is capable of flowing the exhaust, then the retained heat will serve to increase the velocity, lower the pressure seen at the outlet, increase pressure differential, and increase power. If, however, the system cannot flow the gas produced, then the retained heat only serves to increase the pressure seen by the outlet, decrease the pressure differential, and reduce power. Theory is a wonderful thing. It lets you gain an understanding of what's going on, allows you to ask meaningful questions, and leads you to try things in an intelligent manner. Ultimately though, when you start talking about _specific applications_, there's no substitute for trying it out and testing it. "will boring out my exhaust manifold make more power?" Well, calculate how much exhaust gas you should be producing at redline at your desired boost level, and then put your manifold on a flow bench. Are you flowing enough? What's the current pressure at the turbine inlet? What was it when you tried a bored-out manifold? (Here's the kicker) What happened when you put the changed engine on the dyno? Crew chiefs in F1, IndyCar, NASCAR - all these guys have forgotten more theory than I'll _ever_ know, and they still end up trying stuff out on the dyno. But trying stuff _without_ knowing the theory is just blind guessing, putting monkeys on the typewriters and hoping for Shakespeare.
here's another site bout pressure differential on turbos,http://www.thedodgegarage.com/turbo_fun.html
here's an example
All else being equal, The amount of work that can be done across an exhaust turbine is determined by the pressure differential at the inlet and outlet_ (in english, raise the turbo inlet pressure, lower the outlet pressure, or both, and you make more power) Pressure is heat, heat is pressure. Raising the inlet pressure is possible, but tough. Lowering the outlet pressure is easy - just bolt on a bigger, free flowing exhaust. I've seen a couple of posts from people who added aftermarket exhausts, who report "my turbo spools up faster now" Well, that's because by lowering the outlet pressure, you increased the pressure differential, and now the exhaust gas can expand more, and do more work. That increased work pushes harder on your turbo, and it spools up faster. You should also see less boost drop at redline, because if an exhaust system is flow-limited, once you pass the flow limit of the system, any additional gasses you try and force through it only raise the outlet pressure. Higher outlet pressure, lower pressure differential, less work, less boost.
then the question:
"What about people who wrap up there downpipes to keep heat in and the exhaust gases hotter after the turbo. The hotter gases travel faster right, and that decreases pressure (good)? Or, the higher retained heat keeps the gases hot and the pressure stays higher and that would lower the pressure differential (bad)?"
Heh, welcome to the real world. :) Both are legit ways of examining the problem, and either scenario is possible, depending on the flow capacity of the exhaust system. If it is capable of flowing the exhaust, then the retained heat will serve to increase the velocity, lower the pressure seen at the outlet, increase pressure differential, and increase power. If, however, the system cannot flow the gas produced, then the retained heat only serves to increase the pressure seen by the outlet, decrease the pressure differential, and reduce power. Theory is a wonderful thing. It lets you gain an understanding of what's going on, allows you to ask meaningful questions, and leads you to try things in an intelligent manner. Ultimately though, when you start talking about _specific applications_, there's no substitute for trying it out and testing it. "will boring out my exhaust manifold make more power?" Well, calculate how much exhaust gas you should be producing at redline at your desired boost level, and then put your manifold on a flow bench. Are you flowing enough? What's the current pressure at the turbine inlet? What was it when you tried a bored-out manifold? (Here's the kicker) What happened when you put the changed engine on the dyno? Crew chiefs in F1, IndyCar, NASCAR - all these guys have forgotten more theory than I'll _ever_ know, and they still end up trying stuff out on the dyno. But trying stuff _without_ knowing the theory is just blind guessing, putting monkeys on the typewriters and hoping for Shakespeare.
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but wrapping up the downpipes with thermal wraps will eventually create higher pressure since the HOT exhaust gas is moving at a higher velocity..isn't that so..??high pressure=high velocity..then it states that heat=pressure,pressure=heat..wrapping up the downpipes is to retain the heat inside the pipes..and by doing this you are actually trying to increase the outlet pressure,am i right??correct me if i'm wrong..and how does that help in lowering the outlet pressure whereas you are trying to increase it..??..i dun get it..but by allowing the xhos gas to travel faster,it will enable the gasses to flow freely as well..right..??
more confused the more i read it.. :P
duno wat i'm saying as well..hehehe..
more confused the more i read it.. :P
duno wat i'm saying as well..hehehe..
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Hi,
But if you wrap the downpipe to make the gases hotter so that they flow out faster,wont it be the same thing?Because to my understanding,hotter gases = bigger pulses.Bigger pulses = more restriction unless you got a super big exhaust.
Correct me if i am wrong.THanks for the responses!
But if you wrap the downpipe to make the gases hotter so that they flow out faster,wont it be the same thing?Because to my understanding,hotter gases = bigger pulses.Bigger pulses = more restriction unless you got a super big exhaust.
Correct me if i am wrong.THanks for the responses!
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errr hanjackal,i'm not too sure also..yup ur right hotter gasses flows faster
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hahaha..bro this is the same exact question in my mind as well...:_:
no argument there about the piping sizes BEFORE the turbine, but there's some argument there about being bigger = better AFTER the turbine (means the exhaust piping), setup and cc of the engine needs different piping sizes, not all engines need large size exhaust pipes. If you are using SR20det with STANDARD turbine, 2.5" is enough, that's because the only function for the exhaust pipes are to push exhaust air fast enough out of the engine, if you use 3" or 3.5", hot exhaust air will become colder when travelling through the pipes, colder air means heavier air, heavier air means the engine will use more power to PUSH the air out of the exhaust pipes, meaning engine will loose power when doing this. So using the SUITABLE size of exhaust pipes IS VERY IMPORTANT ALSO!!! If you use 3" or 3.5" or even 4" of exhaust pipes in a 3 litre or 4 litre engine, it's suitable, because these engines produces denser and hotter air because of their large cubic capacities.
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HanJackaL said:
exhaust air INSIDE the exhaust pipes are not considered COMPLETELY out of the engine yet, 'cause the pipes are almost air-tight (if it's not, then your exhaust pipes have a hole in it). Why does those GT cars have side exhaust, which is VERY near the engine? why does does super drag cars have so short exhaust systems that most of them directly output the exhaust air just BESIDE the engine (if it has a front engine), not at the back?
As I said before, the heavier the exhaust air, the more power the engine will need to push the exhaust air out, that will mean your engine will loose some strength to push your car. What is meant by heavy exhaust air? it means the air is colder and denser, remember that the hotter the air, the lighter it is.
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