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still confused with intercooler pipes

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1fast97gsx

15+ Year Contributor
4,520
17
Jul 6, 2003
Orland Park, Illinois
I have to order a few more bends and what not for the pipe from the turbo to the intercooler. The turbo is a decent size ( precision sc61 ), and people are telling me to go with at least 2.25" piping, 2.5" would be ideal. Now when I measure the outlet on the turbo the inner diameter is only 1.75" and the total diameter is 2". Now wouldnt it be fine just to run 2" piping into the intercooler, and then 2.25" out? It seems like there is no need to go from 1.75" to 2.5" right where my lower piping would meet the turbo ... although I do understand that after the intercooler it would make sense to make the piping a bit larger. Can someone explain to me why 2" piping in and 2.25" piping out of the intercooler would not be sufficient if the outlet on the turbo is only 1.75"? I'm not arguing or anything, but just trying to understand. I know the greddy kit uses 2.0" in and 2.25" out. What's wrong with this? Thanks to whom ever can explain it!!
 
Think of it in terms of volume. For a turbocharger to flow the amount of air it is capable of, it needs larger pipes. Take the good old straw analogy for example. the bigger the straw, the faster you can finish your favorite beverage. Thats pretty basic but it doesnt need to be any more complicated than that.
 
right ... BUT then why is the place where the intercooler pipe connects to the turbo only 1.75"? Wouldn't that resrict flow there as much as 1.75" piping all the way to the intercooler would since only so much can pass through that opening at once? Thats what I mean....
 
think about the size of the intercooler. bigger inlet and outlets would just make the cooler cool slower. its kinda of simple.;)
 
The theory is sound I guess. For the record I have 2" to the cooler and 2.25" to the throttle body and don't seem to have much problem with it. I was considering making new pies and going upto 2.25 from the turbo to the cooler and 2.5" from the cooler to throttle body (since my cooler is setup that way) but I have a feeling all the work to make those new pipes would be in vain.
 
ok so now the question is. What actually happens if the pipes are "too small?" Will they just blow off? Will I get compressor surge? What are the sideaffects and how would I be able to tell if what I have is sufficient? Thanks.
 
the only thing the bigger pipes will add is lag. If you run the same amount as the opening of the turbo that would be ideal. Any bigger and your creating more volume for the turbo to fill before boost.

actually I just had a thought, if any body can say what size piping the evo uses might confirm or disproove my theory, engineer teams at mitsu have already done the work on this one.
 
Most turbo's have a 2" outlet to the intercooler. I gaurantee you NONE of the faster DSM's have 2" intercooler piping. I can't really give you the smart physics answer here, but I would say that the larger pipes allow the same amount of air to pass through the pipes as smaller pipes, but at an increased velocity. There may be more space to fill but the turbocharger is already pushing the air out in a compressed form (boost) so therefore more space will allow a bigger volume of air to pass in the same amount of time. Just a theory, maybe someone who actually knows physics can chime in here.
 
TwoLiterV8Eater said:
Most turbo's have a 2" outlet to the intercooler. I gaurantee you NONE of the faster DSM's have 2" intercooler piping. I can't really give you the smart physics answer here
You should have left it at that




TwoLiterV8Eater said:
but I would say that the larger pipes allow the same amount of air to pass through the pipes as smaller pipes, but at an increased velocity. There may be more space to fill but the turbocharger is already pushing the air out in a compressed form (boost) so therefore more space will allow a bigger volume of air to pass in the same amount of time. Just a theory, maybe someone who actually knows physics can chime in here.
But no. Here i get to read the most uneducated response ive ever read on the internet hands down. This is better than "how many cylenders does an rx7 have?"

Comes out in boost form? Please guy, do some more reading about how a turbo charged system works it will help you, a good start would be howstuffworks. Then work on understanding the physical properties of air so that this crazy stuff like "boost form" doesn't come out of you in a conversation. Also you would be right about the faster dsm's not using smaller piping, but the reason is that there not using a smaller turbo. It's all relative to the size of the outlet on the turbo.
 
14.5 drift said:
You should have left it at that




But no. Here i get to read the most uneducated response ive ever read on the internet hands down. This is better than "how many cylenders does an rx7 have?"

Comes out in boost form? Please guy, do some more reading about how a turbo charged system works it will help you, a good start would be howstuffworks. Then work on understanding the physical properties of air so that this crazy stuff like "boost form" doesn't come out of you in a conversation. Also you would be right about the faster dsm's not using smaller piping, but the reason is that there not using a smaller turbo. It's all relative to the size of the outlet on the turbo.

I thought I made it clear in my post that I was not a physics major. If you want to be an ass about things, you spelled CYLINDER wrong. Most turbos (the ones we are concerned about, the ones on street cars) do not have a bigger than 2" diameter outlet. However you will not find many places that even sell a 2" upper intercooler pipe. Why don't you tell me why that is since you have all the answers.

To clarify what I said, since I did in fact not word it correctly, a turbo is pushing a volume of air into the piping at a rate faster than it can be consumed by the motor. This is what creates pressure in the system.
 
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Hey guys...

Here's the formula for gas flow in a pipe. When you can figure it out you can start throwing stones.

There's no advantage to having a pipe larger than the the opening to which it leads. In this case I think the largest opening is normally 2 1/4" or possibly 2 1/2" with an upgraded intercooler.
 
well my intercooler has 3" inlet/outlets ( 2 3/4" ID .. ) but I was referring to the size of the outlet pipe on the turbo .. not on the intercooler.
 
14.5 drift said:
You should have left it at that




But no. Here i get to read the most uneducated response ive ever read on the internet hands down. This is better than "how many cylenders does an rx7 have?"

Comes out in boost form? Please guy, do some more reading about how a turbo charged system works it will help you, a good start would be howstuffworks. Then work on understanding the physical properties of air so that this crazy stuff like "boost form" doesn't come out of you in a conversation. Also you would be right about the faster dsm's not using smaller piping, but the reason is that there not using a smaller turbo. It's all relative to the size of the outlet on the turbo.

Don't waste your breath man, there are guys like him all over these forums.
 
Why does anyone have IC piping larger than the size of the throttle body if it doesnt do any good?

I should probably just let this die since no one seems to know the facts here.

Igs were you refering to me or him?
 
A larger intercooler pipe adds volume. At higher rpms, a small pipe might not support enough airflow or cfm ant you can loose top end. While a 2.5" might take 100-150 more rpms to spool, You wont have to upgrade later. With a larger turbo, you need the extra volume of the larger pipe because if it is small, you will work the turbo harder. If you plan to go no bigger than a evoIII 16g, 2" will be fine but if you plan on stepping up to a 50 trim or larger, you should go with at least 2 1/4" It all has to do with efficiency.
 
A larger intercooler pipe adds volume. At higher rpms, a small pipe might not support enough airflow or cfm ant you can loose top end. While a 2.5" might take 100-150 more rpms to spool, You wont have to upgrade later. With a larger turbo, you need the extra volume of the larger pipe because if it is small, you will work the turbo harder. If you plan to go no bigger than a evoIII 16g, 2" will be fine but if you plan on stepping up to a 50 trim or larger, you should go with at least 2 1/4" It all has to do with efficiency

There's no advantage to having a pipe larger than the the opening to which it leads. In this case I think the largest opening is normally 2 1/4" or possibly 2 1/2" with an upgraded intercooler.
With out a large 3 inch throttle body there wouldn't be much benefeit.
 
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