Ok, I am boggled about this setup. I was told that when I setup my 240 for a turbo to run 2.5" hot pipe to the intercooler and 3"?, I believe, to the throttle body.

Why would one step the size of the pipe up AFTER the intercooler when the air is more dense and can be packed into a smaller area?

Is it simply because of the transition from a 2.5" cold pipe to the 3" throttle body would create a restriction on the flowing air or what. I would think you would lose some of boost, or create non-needed lag, when stepping from a 2.5" hotpipe to a 3" coldpipe. With the air being much more dense after the intercooler stepping to a 3 inch coldpipe is similar to just running the hot pipe into a 3.5" or bigger coldpipe (w/o the added benefits of colder air).

Sooo...Why would one go a larger pipe size on the cold side of the intercooler, in theory you could probably DROP a size and create no loss of flow or boost pressure? Right? Wrong?

 

I understand the hotpipe, that makes perfect sense.

well, say the intercooler inlet/outlet are 2.5" and the throttle body is 3. So you transition from a 2.5" to 3" diameter pipe which creates lag right. Now if you just ran the 2.5" all the way to the throttle body your not creating any restriction since the throttle body will use/see all 2.5" diameter of the air.

Thanks,
Tyler

 

a friend whos shop is going to re do my drag piping told me the same thing, that cause i have 2inch off the turbo and 2.5 going into the motor that i should upgrade, they said that alli would have to do is go a little more with thte boost to compensate for the larger pipe but i would be able to move more air velocity, at a better rate, i thought that the bottle neck theory would be better and go from larger to smaller but im not the turbo guru i guess

 

I have a 2.25" elbow off of the turbo and then about a foot of 2.25" , that flares to 2.5" before the intercooler, then exiting the intercooler the whole cold pipe is 2.5".... I have measured boost at the compressor, then at the manifold, and had no pressure loss, and my spool times are extremely minimal.....

 

Nice... I would like to see the same test done with a 3" coldpipe to see the difference. I mean if upping the boost a hair will cure the lag time that it takes to fill the extra space on a bigger pipe and you can flow more air with a 3"...(I'm contradicting my first post. Scratch that.)

How much horsepower are you running and what is your boost pressure?

I am only looking for 220hp or so now but down the road no more than 300hp (I know, I know, that's what they always say )

To keep my current turbo in its efficiency range I need to run at least 8 - 10 psi. Based on that information, will 2.5" suite me or is 3" still the route to go.

Oh, can a 3" pipe be wedged between the battery and fan shroud on an S14? Or should I relocate the battery to run pipe down the hole near the battery so there are less bends in the pipe (or less of a radius I should say?)

Thanks guys,
Tyler

 

Im just running a little baby 50 trim @ around 16 psi (should be around 320 whp after tuning) and I make full boost by about 4400-4600 rpms and like I said, Ive measured boost at the compressor outlet (referenced off the wastegate signal line) , and off the intake manifold, and there is no pressure drop.....

 

if you're running a To4E compressor, run a 2.25" hot pipe and a 2.5" cold pipe. you dont need 3" nor will you feel any differences. if you feel a difference its more than likely a leak or your FMIC is too small. (dont worry that Johnnyracecar core should be good for you up to about 300whp)

 

Thanks Dan.

 

I'm not so sure that you'd really see any meaningful difference in making the coldside bigger. The reason I say that is because most of us can pack more air into our engines than they can handle anyway. When that is the case, efficiency of design sort of loses some of it's luster. I did it just to even out the transition between all the components. MY IC, TB and Mass air are all 3" give or take a little bit. Didn't see the sense in making my pipe look like link sausages or pop beads. But, let's just say that I did it for what I'll call the Hair Spray effect. (That would be the drop in temperature you get whenever a compressed gas is going from a higher pressure zone to a lower one. In my case, from a 2.5" pipe into a 3" one.) Mostly insignificant in this case but hey!!! Ain't physics fun?

Ooops, I forgot most of you don't know what a spray can is that you don't have to pump with your finger....never mind. :roflmao: