GalantVR4.org The Mitsubishi Galant VR-4 Forum
Galant VR-4 Forums » Galant VR-4 » Technical Discussions » Does external wastegate dump increase effective exhaust size under boost?
Previous thread Next thread

Does external wastegate dump increase effective exhaust size under boost?


blkchr91
Unregistered


Galant VR-4 org Post #: 1122449 posted 05/09/13 01:05 AM     Remind Me!  Send Private Message   Edit Post      
So I have a 2.5 inch exhaust from essentially the turbo back. I also have an open cutout pre cat which is loud and getting on my nerves.

I never stopped to think about whether or not the 1.5 inch EWG dump adds to the 2.5 inch exhaust for a total of 4 inches diameter under boost.

If not, does it at least equal a 3 inch exhaust under boost? I have been googling this and it seems like 2.5 inch exhaust + 1.5 inch exhaust = 4 inches under boost period. That would be too good to be true but I would be happy if it were.

Thoughts?

Thanks

| | | IP: (71.63.107.192) | Report this post to a Moderator

blkchr91
Unregistered


Galant VR-4 org Post #: 1122451 posted 05/09/13 01:40 AM     Remind Me!  Send Private Message   Edit Post      
I just thought about it and the answer would be NO...since the wastegate won't be open until after target boost is exceeded.

| | | IP: (71.63.107.192) | Report this post to a Moderator

blkchr91
Unregistered


Galant VR-4 org Post #: 1122453 posted 05/09/13 02:01 AM     Remind Me!  Send Private Message   Edit Post      
hmmm...I think I was right the first time. Exhaust will free up right when target boost is reached and target boost will stay there....this could work out if I have it correct...not sure if I do though.

| | | IP: (71.63.107.192) | Report this post to a Moderator

91_427
Member
427/2000
490/2000


Galant VR-4 org Post #: 1122454 posted 05/09/13 02:17 AM     Remind Me!  Send Private Message   Edit Post      
Quoting blkchr91:

So I have a 2.5 inch exhaust from essentially the turbo back. I also have an open cutout pre cat which is loud and getting on my nerves.

I never stopped to think about whether or not the 1.5 inch EWG dump adds to the 2.5 inch exhaust for a total of 4 inches diameter under boost.

If not, does it at least equal a 3 inch exhaust under boost? I have been googling this and it seems like 2.5 inch exhaust + 1.5 inch exhaust = 4 inches under boost period. That would be too good to be true but I would be happy if it were.

Thoughts?

Thanks




One 2.5 inch pipe plus one 1.5 inch pipe does not have the same flow as a 4 inch pipe because the areas of the two pipes is still less than the area of the 4 inch pipe.



427/2000-Designated Donor
490/2000-Newest Project Pending EAS

Posts: 101 | From: South Jersey | Member Since: 04/02/12 | IP: (214.15.218.74) | Report this post to a Moderator

blkchr91
Unregistered


Galant VR-4 org Post #: 1122456 posted 05/09/13 02:28 AM     Remind Me!  Send Private Message   Edit Post      
Would the 2 pipes together meet the "magical threshold" of 3 inches that everyone these days is seeking for an e316g?

If so, I am content.

Thanks


Edited by blkchr91 (05/09/13 02:28 AM)

| | | IP: (71.63.107.192) | Report this post to a Moderator

91_427
Member
427/2000
490/2000


Galant VR-4 org Post #: 1122467 posted 05/09/13 04:44 AM     Remind Me!  Send Private Message   Edit Post      
Try using basic math. Compare the area of the 2.5 inch pipe plus the area of the 1.5 inch pipe against the area of the 3 inch pipe. If you don't remember the formula for the area of a circle it is 3.14 times radius squared.

EDIT:SPELLING



427/2000-Designated Donor
490/2000-Newest Project Pending EAS


Edited by 91_427 (05/09/13 04:45 AM)

Posts: 101 | From: South Jersey | Member Since: 04/02/12 | IP: (214.15.218.74) | Report this post to a Moderator

Barnes
Firechicken
908/1000
237/2000


Galant VR-4 org Post #: 1122507 posted 05/09/13 10:32 AM     Remind Me!  Send Private Message   Edit Post      
Area of the following pipes:

1.5" = 1.77 sq-inches
2.5" = 4.91 sq-inches
Combined = 6.68 sq-inches
3" = 7.07 sq-inches
4" = 12.57 sq-inches

Rule of thumb: As diameter doubles, area quadruples.

So technically you will have less flow area than one single 3" pipe. However, area is not the only factor related to flow. A dumped 1.5" pipe that is very short has little resistance compared to a pipe that has to go all the way back to the rear of the car. Without doing any math I would submit that a 2.5" exhaust with a 1.5" external dump would flow as well, or better than a full 3" exhaust carrying all the exhaust.



-Jon Barnes
#580/2000 (Long Gone)
#908/1000 Black (Sold)
#237/2000 White

Posts: 6249 | From: Richland, WA | Member Since: 02/09/03 | IP: (96.41.192.140) | Report this post to a Moderator

blkchr91
Unregistered


Galant VR-4 org Post #: 1122517 posted 05/09/13 11:19 AM     Remind Me!  Send Private Message   Edit Post      
Not good at math, but probably better at most things than you will ever be. Thanks for the help.

Quoting 91_427:

Try using basic math. Compare the area of the 2.5 inch pipe plus the area of the 1.5 inch pipe against the area of the 3 inch pipe. If you don't remember the formula for the area of a circle it is 3.14 times radius squared.

EDIT:SPELLING



| | | IP: (71.63.107.192) | Report this post to a Moderator

blkchr91
Unregistered


Galant VR-4 org Post #: 1122530 posted 05/09/13 11:50 AM     Remind Me!  Send Private Message   Edit Post      
Thank you, I wish that I had something definitive to go on. I used to be great at math but have lost it. If you really think so, then I don't see why not.

Quoting Barnes:

Area of the following pipes:

1.5" = 1.77 sq-inches
2.5" = 4.91 sq-inches
Combined = 6.68 sq-inches
3" = 7.07 sq-inches
4" = 12.57 sq-inches

Rule of thumb: As diameter doubles, area quadruples.

So technically you will have less flow area than one single 3" pipe. However, area is not the only factor related to flow. A dumped 1.5" pipe that is very short has little resistance compared to a pipe that has to go all the way back to the rear of the car. Without doing any math I would submit that a 2.5" exhaust with a 1.5" external dump would flow as well, or better than a full 3" exhaust carrying all the exhaust.



| | | IP: (71.63.107.192) | Report this post to a Moderator

Barnes
Firechicken
908/1000
237/2000


Galant VR-4 org Post #: 1122537 posted 05/09/13 12:12 PM     Remind Me!  Send Private Message   Edit Post      
Another way to think of how equal flow area does not mean equal resistance to flow imagine the following:

A 3" exhaust

A 3" exhaust which is stuffed with little smaller pipes, like straws.

The flow area is the same as just the 3" pipe. (Neglecting the material thickness of the straw sized pipes of course.) But due to the increased surface area, and other possible flow effects, the resistance to flow will be GREATER than just a single 3" pipe.



-Jon Barnes
#580/2000 (Long Gone)
#908/1000 Black (Sold)
#237/2000 White

Posts: 6249 | From: Richland, WA | Member Since: 02/09/03 | IP: (198.232.211.130) | Report this post to a Moderator

blkchr91
Unregistered


Galant VR-4 org Post #: 1122538 posted 05/09/13 12:18 PM     Remind Me!  Send Private Message   Edit Post      
Pondering what you are saying and that analogy makes complete sense, but are you now thinking that the overall resistance of this combination may actually be greater than having a 3 inch exhaust? I ask because "the little straw" would be outside of the 2.5 inch exhaust. Really want to know if you have changed your mind on it or if you still think that 2.5 inch exhaust plus that 1.5 inch dump would still exceed the overall flow of just a 3 inch exhaust. I assume that resistance is the inverse of flow PERIOD? Just like in electronics where resistance is directly inverse to current PERIOD?

Thanks


Edited by blkchr91 (05/09/13 12:19 PM)

| | | IP: (71.63.107.192) | Report this post to a Moderator

Barnes
Firechicken
908/1000
237/2000


Galant VR-4 org Post #: 1122539 posted 05/09/13 12:28 PM     Remind Me!  Send Private Message   Edit Post      
That analogy only applies if the pipes are the same length. I.E. If you had a 2.5" pipe from your turbo outlet all the way to the tail of the car, AND a 1.5" pipe from the waste gate all the way to the tail of the car.

So in your case the analogy does not apply because your 1.5" pipe is very short.



-Jon Barnes
#580/2000 (Long Gone)
#908/1000 Black (Sold)
#237/2000 White

Posts: 6249 | From: Richland, WA | Member Since: 02/09/03 | IP: (198.232.211.130) | Report this post to a Moderator

blkchr91
Unregistered


Galant VR-4 org Post #: 1122551 posted 05/09/13 01:16 PM     Remind Me!  Send Private Message   Edit Post      
Gotcha, that clears it up. Thanks again.

| | | IP: (71.63.107.192) | Report this post to a Moderator

91_427
Member
427/2000
490/2000


Galant VR-4 org Post #: 1122712 posted 05/09/13 07:49 PM     Remind Me!  Send Private Message   Edit Post      
Quoting blkchr91:

Not good at math, but probably better at most things than you will ever be. Thanks for the help.

Quoting 91_427:

Try using basic math. Compare the area of the 2.5 inch pipe plus the area of the 1.5 inch pipe against the area of the 3 inch pipe. If you don't remember the formula for the area of a circle it is 3.14 times radius squared.

EDIT:SPELLING







Clean the sand out of your vagina dude.



427/2000-Designated Donor
490/2000-Newest Project Pending EAS

Posts: 101 | From: South Jersey | Member Since: 04/02/12 | IP: (214.15.218.74) | Report this post to a Moderator

CutlassJim
poop load of room
1799/2000
1788/2000
935/1000
912/1000


Galant VR-4 org Post #: 1122717 posted 05/09/13 08:19 PM     Remind Me!  Send Private Message   Edit Post   
Does external wastegate dump increase effective exhaust size under boost?

Yes


/End thread



ALL DSM's are advanced and ALL Evo's retarded
I love my crazy mother!!!

Posts: 1586 | From: Manchester, NH | Member Since: 07/17/06 | IP: (75.69.152.105) | Report this post to a Moderator


Pages: 1
Previous thread Next thread

Extra information
0 registered and 8 anonymous users are browsing this forum.

Galant VR4.org Moderator:  curtis, steve, atc250r, jcgalntvr4-244, cheekychimp, jepherz, Rausch, toybreaker, iceman69510, pot, FlyingEagle 

Print Thread

Forum Permissions
      You cannot start new topics
      You cannot reply to topics
      HTML is disabled
      UBBCode is enabled

Rating:
Thread views: 2565

Rate this thread


News & Events: News | Events
Galant VR-4: Newbies | General VR4 Discussions | Technical Discussions | How To and Info Archive
Marketplace: Parts For Sale | Cars For Sale | Good Guys | Bad Guys
Community: Members' Showcase

Contact Us | Privacy statement GalantVR-4.org

Generated in 0.114 seconds in which 0.067 seconds were spent on a total of 14 queries. Turbo powered.


Hertz's Galant VR-4 Page