Alright, I know there have been a thousand of these threads first off.. but none of them really answered my questions..

I am really trying to figure out how I can benefit from this 3" setup I just bought looking through various forums for turbo diesels, dsms, supras whatever I could find, and I gathered this:

larger piping diameter after the turbo will flow more volume, and allow the charge air to expand as it flows creating a venturi effect which cools the air further


better air flow, cooler air...
remind me again how at any power level this can be bad?

 

I know this will not help much but i think most the car out there even running 9's are running 2.5 in pipping. so no real need for 3"

 

There is no benefit. IIRC, David Buschur conducted a back-to-back dyno test which demonstrated that fact.

 

I disagree with the statement there is no effect. The expanding of the air charge is also known as pressure drop. I.e at the compressor oulet it may be rreading 20 psi after pressure drop in the 3 inch piping at the tb it could be around 18.5 psi. Just an example but pressre drop means power loss. My buddy has a 95 gst and swapped the side mount out for a front mount and 3 inch piping it lost 15hp. Bigger ic piping will also slow spool time down as it takes longer for the same turbo to fill a bigger area when its flowing the same amount of air at full speed. That is common sense. Therefore u will lose power. Same as when choosing proper ic size. It matters whether people thinks it does or doesn't. I would stick with 2.5 unless your running an ungodly massive turbo and drag racing.

 

thats when you friend needs to turn the boost up 1.5psi to negate the pressure drop (majority from the intercooler) and if its a quality aftermarket intercooler will most likely make slightly more power. Your argument is flawed.

pressure drop from 2.5-3" is not even noticeable. 2.5" vs 3" is not even worth a discussion for 99% of street cars out there.

 

I'm on 2.5 piping and made a good amount of power. And milspec 65mm tb.

 

Ya great idea when u experience pressure drop just turn the boost up on his evo 3 turbo that's running maxed at 18 psi with it creeping to 24 in higher gears. That's how turbos bite the dust my friend when u over spin them they tend to sling blades pretty quickly. And yes there is a huge difference in2.5 and 3in piping. Here is an example since my argument is flawed to prove my point.

To find the volume of a cylinder u use this formula. Pie times radius squared times length times 7.48.

3in piping= 3.14159times1.5squared times let's say 4 feet of pipe times 7.48= 211.49ci

Now let's see what 2.5 in of piping comes out to using the same 4 foot piece of pipe. Bet u will be surprised.

2.5inpiping= 3.14159times1.25squared times 4 times 7.48= 146.63ci

And that's just 4 feet of piping. My argument is far from flawed its simple math genius I suggest u learn some when it comes to turbos airflow and simple ole ic piping cause that's all that's used is math. So as I said before ic piping can cause power loss. It does matter.

 

you only need to increase your piping size when the speed of airflow in that piping is starting to reach the speed of sound, i'm pretty sure a lot of workshops use 0.8mach as a good limit

 

I looked and searched for those dyno graphs and I couldnt find them anywhere


I understand the spool time loss, but pressure drop?
I dont think that would ever happen if the IC was tight

 

how exactly would you figure this?

 

invented 2.5 piping for a reason. Thats unless your doing major mods

 

I can't recall if this was posted here or in Buschur's forum, but it exists nonetheless.

Basically, 3" IC tubing just takes more space and adds volume to the system.

 

0.3 Mach is where you want to stay below on something like an intercooler pipe where you aren't dealing with pulse flow (for the most part). Above 0.3 Mach the flow becomes more compressible and the losses start adding up.

 

http://www.engineeringtoolbox.com/ma...ber-d_581.html

 

This is the thread most are referencing of David Buschur's testing: https://www.evolutionm.net/forums/ev...schurs-rs.html

Now some other scenario's are being thrown around in here that have no validity or floor to stand on. Saying "X" car lost "Z" amount of power has no bearing on anything without proper testing. Almost any turbo car or evo for that matter WILL lose boost pressure when moving to a bigger intercooler and piping. This is common and yes you will lose power that is until you bring your boost level back up the reference point it was before. Common sense to say the least...

I think 95% of the cars on this forum that make a large amount of power (600whp and above) don't have any issue with 2.5in piping. The theoretical advantages don't outweigh the disadvantages unless certain circumstances exist that otherwise wouldn't be commonly seen by one car. One of the very few cars I see running 3in intercooler piping is Sierra Sierra's evo. But I am sure they have their own reasoning for that.