Intercooler Piping Size?

[robbbby]

What size is the IC piping on the s13 IC kits, greddy v/r and blitz LM, I thought they would be 3" but I just got my s13 hotpipe from Heavy throttle today and it is about 2-1/4" ?Isn't the size of the hotpipe supposed to be the same as the rest of the IC piping?

[97 Silvia]

Usually the piping after the intercooler is larger diameter because after the boost has been cooled it becomes more dense and thus needs a larger pipe so the flow is not restricted.

[SpeedRacer1]

If something is colder it becomes less dense and takes up less space. Hence part of the reason why NOS is used, since it allows more O to fit into the same size space.

[97 Silvia]

Yeah that's what I meant to say... just typing too fast without thinking. It becomes less dense so it has to expand and thus needing the larger piping.

[hurddawg]

If something is colder it becomes less dense and takes up less space. Hence part of the reason why NOS is used, since it allows more O to fit into the same size space.

this isn't wholly true either...cold air IS more dense, but takes up less space. "Air" contracts in size as it gets colder, which doesn't mean there is less air, just air packed in more efficiently (effectively taking less space up).

Density = amount of particles in given area, more particles in given area is more dense.

edit:

a turbo does the samething, all the turbo does in compress the air into a given area and packs-in the air more efficiently. Although temperature derived "compression" is naturally occuring.

[SpeedRacer1]

Oops looks like I didnt read what I wrote either. Oh well way too lazy

[robbbby]

So no one knows the size of the piping on the greddy and blitz kits?

Also if the air is less dense on the hot side shouldn't the hotpipe be larger then the piping after it has been cooled since air expands when it's hot and contracts when it's cooled?

[fiznat]

Im no physics major, but wouldnt a smaller pipe help to keep the compression up? I mean, whats the point of compressing air if you're only gonna toss it into a larger space-- wont it loose some of its compression? Take the compressed air and force it into a smaller area-- wont that keep it more stable? I donno maybe I just have no idea what im saying.

[robbbby]

That does make sense but then after the air is cooled the piping on the other side of the IC would have to be even smaller for the cold air to keep compression?

[fiznat]

heh yeah, in theory. thats what makes me think I'm wrong. either that or we've just now developed some revolutionary method to get higher compression using smaller tubes?!?! we could be rich!!

seriously though, if my compression theory thing is right-- the cold pipe SHOULD be of a smaller diamater- to account for the smaller space the cooled air takes up. Maybe you got a cold pipe by mistake??

[Cyberkreig]

You are partly right, and intercoolers do cause a small (if its a good IC its a small) pressure drop.

I'm no physics professor myself, but I think they idea is that you can put more "small" dense cold air, in a big tube.. thus the benifit of larger turbo..

after all, when turbo-ing. we are tryign to pack as much air in as possible..

[Cyberkreig]

sorry to double post.. but as soon as I posted that i thought of this:

Larger pipes woudl also create less resistance on the compressor wheel, allowing for turbo longevity (?)

If more experinced ppl would comment on the above ideas.

[fiznat]

yeah I was thinking about that-- the bigger the turbo, the bigger the piping needs to be so that it doesnt restrict flow. the piping should also be able to maintain a certain pressure though- dumping into too large of a pipe will most certanly cause a pressure drop... no sense in that.

Soooo shouldnt IC pipes be specific to what turbo they're attached to? Get a bigger turbo should mean get new IC pipes, but I never hear of people doing that... Maybe a quarter or half an inch in the diamater of the pipe doesnt really matter though... and around 3" is a good size that fits most turbo applications? I really cant say...

[BinaryVertigo]

imo the "hot pipe" is usually smaller than the "cold pipe" on engineered i/c kits because in theory you are trying to pack and force as much air away from the turbo as possible to make it readily available for the throttle body (hence boost) ...therefore if the piping is smaller on the hot pipe (compared to the cold pipes) you can get the mass of air to and through the i/c quicker than a larger piping....those guys at apex'i and greddy etc know what they're doing and if i was doing a custom i/c setup i'd pay close attn to how they designed theirs

[AllTurBo]

air density is a function of air mass and volume, so theoretically a smaller cold pipe would give you a higher pressure BUT pressure is also dependant on velocity and temperature, the higher the velocity of the air, the less dense it becomes, also the higher the temp the less dense. The best way to think about it is that in a system with one inlet and one outlet (ie. an intercooler) the amount of mass entering a system is equal to the amout of mass exiting the system. Unless your intercooler is leaking, the amount of air the turbo puts into th i/c will be the exact same amount of air exiting. The air may have different temps, velocities, and densities at the inlet and outlet but the air mass flow will be the same at both ends. I believe this is the 2nd law of thermodynamics. The reason to have larger pipes is to put less stress on the turbo and to maintain a smooth laminar flow across the intercooler. I can provide equations if need be, there will be a quiz next week

[fiznat]

yeaaah but its not mass we're concerned with really. we know that air is gonna get from one end to the other... it's just wont dumping all that compressed air into a big tube allow the air to spread out and lose the compression we just worked so hard for?

Also, on the cold pipe, since the air is more dense it will take up a smaller amount of space... so if we put that same air into the same size pipe as the hot pipe, that'll allow even more room for it to expand, wasting compression....

....or are you a physics teacher and I just got an F on the quiz? lol

[Cyberkreig]

so if we put that same air into the same size pipe as the hot pipe, that'll allow even more room for it to expand, wasting compression.... I thought we said Hot Pipes are smaller? Leaving less room for expansion.. blah blah

Your still not looking at it completely WE knew that Density is a funcion of Mass and Volume.. What we did not take into account was velocity. We know mass is a constant, we also know that temperature decreases (puprose of IC) and Density thereby Increases. Now to put it all together.. I can see that the air leaving the IC has slowed down. It HAS to have slowed down b/c if mass is constant yet the air is in a larger space at the same pressure, there must be moving slower (as apposed to the hot side).

So then the IC actualy serves to cool the air, and create a sort of pileup of useful air at the throttle plate.

How'mai doin?

[I H8 UR DSM]

i didnt read all these post at all but.....

the hot pipe is usually smaller, because the greddy kits dont include the hotpipe, so a stock hotpipe is still used...and compnies like HT sell remade 'stock' hotpipes, to be used with the kits, which include larger diameter piping....

like i said, i didnt read the thread, so if that was said, or offtopic, sorry : )

[AllTurBo]

exactly. When air leaves the turbo it's hot, moving very fast, and is useless unless you want to detonate you engine. the air at the other end of the I/C is at the same pressure but it is colder and moving slower and thus more dense. I think a larger hot pipe will aid cooling because the air coming from the turbo will have a lower velocity because it's in a larger area. but because now you have a larger area you just need to wait longer for the boost to build up. Hopefully the extra time you wait for the boost to build will be offset by the power you are produceing with the more dense air.

[I H8 UR DSM]

well with a stock turbo, youd use a stock hotpipe, with a larger turbo, you'd prob go with a larger piping, in turn offsetting that delay in boost buildup......or something.