The Top Mitsubishi Galant VR-4 Resource

Join the best E39A 1991-1992 Mitsubishi Galant VR-4 community and document your GVR4 journey.

  • Software Upgraded - Reset Your Password to Login
    In order to log in after the forum software change, you need to reset your password. If you don't have access to the email address you used to register your GVR4.org account, you won't be able to reset your password. In that case, follow the instructions here to regain access to the forum.

Intercooler piping 3in or 2.5in

Andy_S

Well-known member
Joined
Jan 30, 2007
Messages
982
Location
Shithole Wisconsin
I am re-doing the intercooler piping on my galant. I like the way its routed, but I am going with aluminum over the steel which is on it now. Its short route and a treadstone vertical flow intercooler with 3in inlet/outlet on one side. I already have the piping coming from the turbo to IC which will be 2.5". My question is would 3" be overkill from the IC to the TB? Reason I ask is because I have extra 3" pipe laying around to use. I don't want to initiate any more lag than I have to, thats the main concern. My common sense is saying no because the 2.5 wasn't restrictive yet and it would cause the turbo to work harder/longer to fill the pipes with air. Also the velocity of the air must be reduced. I suppose price doesn't matter because I would have to buy new couplers(2) which could easily be more than 2.5 piping anyway. Also, the car is sporting a 6152E and meth. It will also have a Non-Turbo TB and is currently on a stock intake manifold. Any input is appreciated. Thanks, Andy

:Cliff Notes: 2.5in or 3in IC pipes, which is better.
 
Last edited by a moderator:

2.5inch FTW but if you already have the 3in piping /ubbthreads/images/graemlins/dunno.gif use it, cant see lag being affected much.
 

the new version of the ets runs 2.5 its the way to go unless you have a huge turbo. The 2.5 is just right for a evo3 16g, 20g, 50 trim etc. The old ets kit used 2.25 i think, or it might have allways been 2.5.
 

It used to be 2.25 on the hot side and 2.5 on the cold. Now it's 2.5 all the way. I don't think your setup warrants 3" pipes.
 

Polish

Well-known member
Joined
Jan 10, 2005
Messages
8,936
Location
NE, IN
I'd stick with 2.5".
 

onesickcrx

Well-known member
Joined
Jun 3, 2007
Messages
1,076
Location
NY
Some where on either the Evo or Buschur Forums there was a back to back test with a 35R I believe 2.5" cold side vs 3" cold side and I think Buschur's final numbers were a gain of 7 HP and 3 TQ over 2.5" but it slowed spool down by 300 rpm later or something similar to these numbers and this was on a 600-700 hp car

So not worth the Hassle in my mind
 

curtis

Well-known member
Joined
May 4, 2003
Messages
11,892
Location
Clarksville TN
I put 3 inch on mine and could tell a difference but others test without pictures may not tell the whole story. If you come out of the turbo and instantly go huge this is bad. if you transition a pipe from 3" to 2 1/2" instantly this is bad. Don't know what Dave Buschur did but not to may places sell cone shaped pipe and this part is easily over looked because of the masses selling transitional reducers

Now on my car it comes out at 2.3" or something id on the turbo I found an elbow and welded to a v band clamp for the schwitzer then gradually increased the size by making a long cone and welding together then in had an elbow welded to the IC, air passed through the core and then out another 3" elbow that was welded to the core. Then up past the radiator into the pipe on the throttle body that transitioned from 2.5 inch to 3 inches over about 8 inches. At first it had a silicone reducer and when i rebuilt the top pipe the car lost like 4 pounds of boost without changing a thing so this was a major bottle neck. 3 inch IC pipes if done correctly can show a large benefit I'm sure as long as you have a turbo large enough to handle it. You just have to remember air has mass and flows more like water than what people think,the statement It will be fine is used to much for fluid dynamics, as long as the flow is laminar and the flow doesn't go turbulent benefits can be made but fast transition couplers should never be used. The atoms on the side of your IC pipe are locked on there because of the friction facto/roughness of the pipe then the air molecules pass over each other in sheer into a cone shape point.

For example the picture below is one that I built, its in the for sale section now. The air as it changes from 3 to 2.5 gradually reduces to increase the velocity and fill the entire pipe instead of going turbulent in a reducer and only filling a small part. You have to imagine a cone flowing through the pipe if you hit a 1/2 inch tall wall around the whole edge the air that is traveling super sonic in the pipe now smacks the wall and angles inward going turbulent and blocking flow. a 3 inch to 2.5 fast reducer may coke bottle the shape of the airstream for a few inches but thats still a reduction of flow in the system and may make it worst that what you originally had. I could preach on this for hours stuff fascinates me. But my reply go for it it does improve performance if you a have
(a) turbo large enough to support it and
(b) do it correctly
Its not that hard to make a cone cut the pipe down the middle and then use a box of worm clamps or if using steel you'll be needing T bolt clamps. clamp it down letting one side ride over the other and when you have correct shape and size mark it with a sharpie and remove clamps then cut out the wedge/pie shape reinstall the clamps and then stitch weld.
just google research turbulent flow, laminar flow, relative roughness, friction factor, reynolds number, cone reducers,turbulent flow in orifice... pictures help so just google and click the image link at the top

 

Andy_S

Well-known member
Joined
Jan 30, 2007
Messages
982
Location
Shithole Wisconsin
Thanks Curtis for the informative post. This stuff fascinates me as well. When you say "a turbo large enough to support it" what are we talking here? Is there a lb/min at which 3in has a larger gain in efficiency? Right now the piping will be going from 2in out the turbo, to 2.5 piping to 3in intercooler inlet. Since the outlet is 3in as well, I figured I would keep the whole coldside 3in. The TB is 2.75. In your opinion 3in to 2.75 with a coupler will cause turbulence? I could always cut and weld the pipe to the TB to reduce in about 6" to 7". Do you have any pics of your setup.

As mentioned before, if the lag was increased by 300 rpm, that seems minuscule. I was expecting it to be more substantial. Does anyone agree?
 

jepherz

Staff member
Joined
Aug 8, 2004
Messages
7,877
Location
KC, Missouri
I think that this question is very similar to "should I go with X diameter exhaust?" I would think larger IC piping will always improve your top-end horsepower, but will hinder your spool up. I'm going to help you out and suggest that maybe the fact that you have a bunch of 3" piping should be the deciding factor? Keep in mind the other cons, though, such as routing/fitting difficulties.
 

Polish

Well-known member
Joined
Jan 10, 2005
Messages
8,936
Location
NE, IN
Just hold a 3" pipe under the hood, they are WAY bigger than 2.5". You'll have to do a lot more work fitting it also as jepherz just mentioned.
 

Andy_S

Well-known member
Joined
Jan 30, 2007
Messages
982
Location
Shithole Wisconsin
I have mocked up with 3in and I will have no problems fitting it in. There is almost nothing in my engine bay and it will be a straight shot to a bend before the TB. Its not really if I can, but if I should.
 

curtis

Well-known member
Joined
May 4, 2003
Messages
11,892
Location
Clarksville TN
Man the pipe in the picture is part of my old one. When the car goes back together its getting either a 90 Q-45 or a dual butterfly ford t-body. if I do the dual I'll be buying a mustang oval inlet from BBK or somewhere at about 200 for one piece. These are old pictures of the cold side. I built it from an advance auto parts/aem honda ricer setup for like 80 dollars.



 

Barnes

Well-known member
Joined
Feb 9, 2003
Messages
6,249
Location
Richland, WA
Quoting onesickcrx:
Some where on either the Evo or Buschur Forums there was a back to back test with a 35R I believe 2.5" cold side vs 3" cold side and I think Buschur's final numbers were a gain of 7 HP and 3 TQ over 2.5" but it slowed spool down by 300 rpm later or something similar to these numbers and this was on a 600-700 hp car



Okay. I have a very hard time believing that. That's basically a 30% increase in volume, but the volume on a 3" cold pipe(insert assumptions) is like 0.15 ft^3. That is tiny relative to the volume of air moved by a turbo.
 
Last edited by a moderator:

curtis

Well-known member
Joined
May 4, 2003
Messages
11,892
Location
Clarksville TN
Probably because of a use of 3 to 2.5 reducers and the air was going crazy turbulent. If done properly might have picked up alot more power and spool. Without two kits a car and a dyno we'll never know but my butt o meter said that the car ran stronger and spooled faster, that or tire spin made it come on faster..
 

Barnes

Well-known member
Joined
Feb 9, 2003
Messages
6,249
Location
Richland, WA
I'm starting to think that the new tools in product development like this should be a highly accurate flow meter, and a pressure differential gauge.

Those two instruments could show any shortcomings in the design, or if it is doing anything at all.
 

curtis

Well-known member
Joined
May 4, 2003
Messages
11,892
Location
Clarksville TN
Thats just the thing the companies that are flooding the market with this stuff don't have a flow meter, flow bench or anything else they bend pipe to fit and sell it dirt cheap. As long as it looks good and sells they don't care about hp gains or anything else.
 

Barnes

Well-known member
Joined
Feb 9, 2003
Messages
6,249
Location
Richland, WA
Well. To this day I've never see pressure differential readings for ANY fmic piping kit or intercooler. Even from the good vendors.
 

Do you guys think that customers are going to pay the increased cost of the product if companies spend more time in R&D?
 

Barnes

Well-known member
Joined
Feb 9, 2003
Messages
6,249
Location
Richland, WA
For the cost of the stuff I would personally measure, it would not cost that much.

And yes, I'd pay more/buy from someone else if they had solid numbers that showed their product is superior.
 
Support Vendors who Support the GVR-4 Community
Boosted Fabrication ECM Tuning ExtremePSI Fuel Injector Clinic Jacks Transmissions JNZ Tuning Kiggly Racing Morrison Fabrications RixRacing RockAuto RTM Racing STM Tuned

Recent Forum Posts

Top