I've seen many people swap out stock parts and put new stuff in.
What does Cold air intakes and exhaust actually do, besides making your car sound like a jet engine?

cold air, the filter is further away from engine bay so it takes in cold air. basic knowledge of science shows cold air is denser and more compressed, more air u ignite, = more power.

exhaust: air flows more freely, yadda yadda, more useful on FI cars where u need to get rid of backpressure

In layman terms, it frees up a few horsepower. You won't that much of a difference half the time, though.

while it is true exhaust tends to gain a lot more power on FI cars you do not want back pressure whether the car is NA or FI

yes, maybe i worded it wrong, getting rid of backpressure on FI cars is better/more hp, than a NA

I concur. A lot of the ricers think that these mod actually gives you hp. They don't realize it frees up the restrictions.

well u are getting more HP regardless

don't forget they should be used together o.o, putting a huge CAI and keeping your exhaust stock could net you negative figures

frees up restrictions therefore making the engine produce more hp....also the exhaust on an NA car is more than just freeing up restrictions



uhhh 99% of the time doing only one will increase the power produced by the engine

The engine is already making that power. The stock components which is used is what's robbing that power. I wouldn't necessarily say that those mods produce more power. Rather, they free up what was lost.

i think this is gonna lead to a philosophical debate... lol


but i guess "freeing up" power makes more sense.

if you were to get married and pay less on taxes. you arent making more money, just freeing up cash

I can see mods such as cams actually making more power since it's changing the characteristics of the engine by having a more aggressive lift and duration.

no its not already making that power especially with exhaust system which can change the scavenging effects. your argument is more inline with a lightweight flywheel than intake/exhaust which doesnt increases the power output from the engine.

Anything that frees up restriction isn't magically putting out more power.

It's like losing money at a casino. If you lost 300,000 and go back months later and win 100,000, you didn't necessarily win that 100,000. Rather, you got back 100,000 of what you lost.

like i said, philosophical

Over 9000 man. Over 9000.

^ (that's that vegeta meme but i don't get it)

Mr. Chan is saying an increase in airflow efficiency won't change the potential output power of the engine but it will bring the engine's output power closer to its potential.

azn akira is saying an increase in airflow efficiency will result in more power being made in the engine which wasn't being made prior to the airflow mods.

I'm seeing different verbiage to say the same thing: increase in engine output power.

i understand what you are saying, but im saying for things like exhaust systems (and intake runners/velocity stack lengths too but this thread isnt about those) are not just about freeing up restrictions. they can be tuned to make the engine operate more efficiently at differing points in the power band. if it were just about freeing up restrictions than running open exhaust ports would be the best but it's not

^hes got a point




but simply put. wether u make it or free restrictions u get MORE HP

hmm, if u free up restrictions, wouldnt u actually be making more hp?

for example: you need to move bricks. by yourself you can move 10, but with a cart, you can move 50.

well yes, but there is more to it than just that. for NA applications there is a thing call scavenging. basically you use the exhaust pulses to help draw air through the combustion chamber, you have to can change the header length, diameter, and collector style to have differing effects.

i looked up scavenging...

with every exhaust pulse, there's a region of low pressure left behind in its trail. during the brief moment when both the exhaust valve (which is closing) and intake valve (which is barely opening) are still open, that low pressure exhaust pulse can suck more clean air through the intake into the combustion chamber to yield more power. the magnitude, shape, duration etc. of that low pressure pulse can be tuned to maximize the air scavenged through the intake stroke at certain rpm.

i'm guessing the timing of the scavenging is dictated by back pressure so having any kind of back pressure on the exhaust stroke is actually NOT always bad?

i'm also guessing it can take power away at certain rpm to reallocate it at other, more useful rpm. azn akira is saying the way power is attained through scavenging is different than the way power is attained through freeing up airflow restrictions. is that really true? if you run open exhaust ports, can't that also induce a low pressure scavenging effect just like a tuned exhaust, but unlike a tuned (still restrictive) exhaust the scavenging will be maximized across all rpm?

well it's not that you would want back pressure, it's just that back pressure in higher rpm's would be a by product of designing an exhaust system for low or mid range



im not an engineer but the reason why scavenging works is that the the low pressure tail is lower than the ambient pressure. if you ran an open exhaust port the low pressure tail would never be less than ambient pressure so you would have little to no scavenging effects

^makes sense. with that argument, scavenging will boost power more than open exhaust ports can. but only at certain rpm. running open exhaust ports will have a less significant boost in power but it will be across a wider power band. scavenging takes advantage of air restriction whereas opening up exhaust ports is a mindless brute force method without using physics tricks. two different flavors of obtaining more power.

whoa there, OP was talking about intake and exhaust, not the exhaust manifold.

well the never specified and the header is part of the exhaust system, plus the cat back does have some affects on the scavenging so..

here. i will word my answer very very carefully.

Changing out the exhaust and intake will create horsepower gains. Horse power was not added.

I think the reason for the arguments here is because of two differing views. one group sees the whole car as an "engine", saying that changing the exhaust and intake will "add" horsepower. the other only sees the engine as the powerhorse, saying that adding an exhaust and intake will "free up" restricted horsepower.

In essence, both are correct. engine horsepower and power to the wheels differs greatly. if you added an exhaust and intake to JUST and engine, there will always be power loss no matter what exhaust or intake you use. if you changed out the stock intake and exhaust in a CAR, you will have noticable power gains.

these are two different things and you cannot argue against each other.

no....

please explain why sometimes lengthening velocity stacks can increase power when shorter ones are more akin to having no intake. why do formula 1 engines use velocity stacks instead of just open intake ports? velocity stacks smooth out the airflow going into the engine allowing a more even entry into the combustion chamber

http://www.youtube.com/watch?v=Go3Fgd1wgic...feature=related

go to about 4:48 you can see the variable length intake runners there, something f1 car used to have until they were banned. if adding an intake to an engine decreased power why would they spend all of this money to develop these systems?

also having no header will give you no scavenging effects in high rpms which is very important to making power

a standalone engine without an intake/exhaust system connected to it will produce less hp at certain rpm than an engine connected to a properly tuned intake/exhaust system. this argument has already been established...



this is how i imagine the horsepower vs. rpm curves (VERY simplified)



scavenging restricts power at certain rpm so more power can be produced at other rpm. open ports "free up" power at all rpm's but it doesn't peak as high as scavenged power. HOWEVER if you were to take the average power (area under the curves divided by entire rpm range) then

Pavg,open ports > Pavg,scavenging

the argument has been assuming more power is desirable at higher rpm but i believe scavenging may be achieved at any rpm range (like low-to-mid range) if the intake/exhaust are tuned properly. just my interpretation, not based on any proven data.

touche

en garde

for safety.

why are we discussing F1 cars anyways? it has nothing to do with the topic and we are discussing regular road cars. F1 cars are completely different from road cars. Yes, in an F1 car it does that. but have you seen the difference between the intake of an F1 car and an aftermarket CAI? THEY ARE NOTHING ALIKE. the performance of an F1 intake performs nothing like a regular CAI. stop using F1 cars to try and prove your point. its just an excuse you are pulling out of you ass to try and prove your point. we are strictly talking about aftermarket intakes and exhausts for regular road cars. not custom built F1 cars. and guess what? F1 cars come stock with the best intakes and exhausts. we are talking about aftermarket replacements.

you said and i quote "if you added an exhaust and intake to JUST and engine, there will always be power loss no matter what exhaust or intake you use"

which is not true. intake runner and header design are crucial to making making good power. an engine by itself with no intake or exhaust will not be able to breathe as efficiently. intake runner length and header design are designed to use the difference in pressure to literally suck the air into the combustion chamber at a force that is greater than just relying on atmospheric pressure alone

f1 cars use engines just like any other car, the same principles apply, what's true for an f1 engine is true for a regular engine. the laws of physics don't change. it often helps at looking at extremes when trying to figure out if something has an effect on something else



actually they dont because they were banned for making too much power which is why you dont see variable length intake runners in f1 anymore.