Go Back   EcoModder Forum > EcoModding > EcoModding Central
Register Now
 Register Now
 

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 08-11-2022, 07:42 PM   #21 (permalink)
EcoModding Lurker
 
Join Date: Jun 2022
Location: Bremerton, WA
Posts: 83

Passat TDI Wagon - '97 VW Passat Wagon TDI
90 day: 53.65 mpg (US)
Thanks: 22
Thanked 41 Times in 33 Posts
added photo- Low pressure exhaust exit

don't know why my photo did not show in my reply post above, but here it is again


Attached Thumbnails
Click image for larger version

Name:	undertray 3.jpg
Views:	88
Size:	57.9 KB
ID:	32727  
__________________
97 Passat TDI Wagon
Bosio 520 DLC nozzles, chip tune
Mufflerectomy
306k miles
Scan Gauge II
full belly pan
26 gallon tank
  Reply With Quote
The Following User Says Thank You to Caddylackn For This Useful Post:
aerohead (08-15-2022)
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 08-13-2022, 05:57 PM   #22 (permalink)
Corporate imperialist
 
oil pan 4's Avatar
 
Join Date: Jul 2011
Location: NewMexico (USA)
Posts: 10,547

Sub - '84 Chevy Diesel Suburban C10
SUV
90 day: 19.5 mpg (US)

camaro - '85 Chevy Camaro Z28

Riot - '03 Kia Rio POS
Team Hyundai
90 day: 30.21 mpg (US)

Bug - '01 VW Beetle GLSturbo
90 day: 26.43 mpg (US)

Sub2500 - '86 GMC Suburban C2500
90 day: 11.95 mpg (US)

Snow flake - '11 Nissan Leaf SL
SUV
90 day: 141.63 mpg (US)
Thanks: 253
Thanked 3,377 Times in 2,673 Posts
Someone on here pit a heater core inside their air cleaner box for consistent temperatures.
__________________
1984 chevy suburban, custom made 6.5L diesel turbocharged with a Garrett T76 and Holset HE351VE, 22:1 compression 13psi of intercooled boost.
1989 firebird mostly stock. Aside from the 6-speed manual trans, corvette gen 5 front brakes, 1LE drive shaft, 4th Gen disc brake fbody rear end.
2011 leaf SL, white, portable 240v CHAdeMO, trailer hitch, new batt as of 2014.
  Reply With Quote
Old 08-15-2022, 07:59 AM   #23 (permalink)
EcoModding Apprentice
 
Join Date: Aug 2022
Location: South Africa
Posts: 126
Thanks: 51
Thanked 44 Times in 41 Posts
Quote:
Originally Posted by aerohead View Post
The lowest pressure will occur along the sides of the vehicle, not the rear.
Exhausting to the rear requires that zero leakage occur at the trunklid (boot) seal, and seal between trunk and rear seat/cabin.
It's the reason NASCAR demands side pipes to dilute tailpipe gases which could be inhaled during 'drafting.'
(Apologies for hijacking your thread Talos, but the pics below do show the high pressure areas in front of the car too)

I'm aware of the venturi effect aerohead and that fast moving air generally means lower pressure.

But aerodynamics is a counterintuitive business and i'm confused.

Here's the intuitive idea:


And here's flow which goes with what you said:


And here's a pressure view from underneath a car where one can see a hint of orange high pressure behind the car:

(Is the high pressure just low down..?)

Here's the exhaust next to the number plate on an early Lotus Europa:
(my project car if I ever get the damn Anglia sold)


But it was moved to the more conventional spot in later models.

At a guess I'd say the rear number plate area is likely to be the most consistent low pressure area on a car at various speeds if you don't care about CO poisoning..?

Link to article where the pics come from:
(properly placed bonnet vent seems like a good idea)
https://robrobinette.com/S2000Aerodynamics.htm

Other links showing the low pressure area behind a car, where people like to put boat tails to 'fill that vacuum' (your canopy included! ):

https://www.researchgate.net/figure/...fig2_322640200

Car Aerodynamics Basics, How-To & Design Tips ~ FREE!

Last edited by Logic; 08-15-2022 at 01:51 PM..
  Reply With Quote
The Following User Says Thank You to Logic For This Useful Post:
aerohead (08-15-2022)
Old 08-15-2022, 08:02 AM   #24 (permalink)
EcoModding Apprentice
 
Join Date: Aug 2022
Location: South Africa
Posts: 126
Thanks: 51
Thanked 44 Times in 41 Posts
Quote:
Originally Posted by Caddylackn View Post
I am trying this out, making my exhaust exit at a low pressure area. Air velocity should be high here and pressure low. I should get a bump up in engine efficiency.



Seems to work well. Someday I will put on a slip on tail pipe and extend it past the bumper and do a A B A comparison in gas mileage.
Sounds interesting Caddylackn. Do give me a heads up when you post!
  Reply With Quote
Old 08-15-2022, 10:50 AM   #25 (permalink)
Moderator
 
Vman455's Avatar
 
Join Date: Feb 2012
Location: Champaign, IL
Posts: 1,919

Pope Pious the Prius - '13 Toyota Prius Two
Team Toyota
SUV
90 day: 51.62 mpg (US)

Tycho the Truck - '91 Toyota Pickup DLX 4WD
90 day: 22.22 mpg (US)
Thanks: 198
Thanked 1,764 Times in 923 Posts
Quote:
Originally Posted by Logic View Post
(Apologies for hijacking your thread Talos, but the pics below do show the high pressure areas in front of the car too)

I'm aware of the venturi effect aerohead and that fast moving air generally means lower pressure.

But aerodynamics is a counterintuitive business and i'm confused.

Here's the intuitive idea:


And here's flow which goes with what you said:
https://robrobinette.com/images/S200...ion_NASCAR.jpg

And here's a pressure view from underneath a car where one can see a hint of orange high pressure behind the car:

(Is the high pressure just low down..?)

Here's the exhaust next to the number plate on an early Lotus Europa:
(my project car if I ever get the damn Anglia sold)


But it was moved to the more conventional spot in later models.

At a guess I'd say the rear number plate area is likely to be the most consistent low pressure area on a car at various speeds if you don't care about CO poisoning..?

Link to article where the pics come from:
(properly placed bonnet vent seems like a good idea)
https://robrobinette.com/S2000Aerodynamics.htm

Other links showing the low pressure area behind a car, where people like to put boat tails to 'fill that vacuum' (your canopy included! ):

https://www.researchgate.net/figure/...fig2_322640200

Car Aerodynamics Basics, How-To & Design Tips ~ FREE!
Gee, if only there were a way to measure aerodynamic pressures on your own car instead of all this guessing and speculation.
__________________



  Reply With Quote
Old 08-15-2022, 01:30 PM   #26 (permalink)
Master EcoModder
 
aerohead's Avatar
 
Join Date: Jan 2008
Location: Sanger,Texas,U.S.A.
Posts: 14,924
Thanks: 23,056
Thanked 6,813 Times in 4,335 Posts
pressure

Quote:
Originally Posted by Logic View Post
(Apologies for hijacking your thread Talos, but the pics below do show the high pressure areas in front of the car too)

I'm aware of the venturi effect aerohead and that fast moving air generally means lower pressure.

But aerodynamics is a counterintuitive business and i'm confused.

Here's the intuitive idea:


And here's flow which goes with what you said:
https://robrobinette.com/images/S200...ion_NASCAR.jpg

And here's a pressure view from underneath a car where one can see a hint of orange high pressure behind the car:

(Is the high pressure just low down..?)

Here's the exhaust next to the number plate on an early Lotus Europa:
(my project car if I ever get the damn Anglia sold)


But it was moved to the more conventional spot in later models.

At a guess I'd say the rear number plate area is likely to be the most consistent low pressure area on a car at various speeds if you don't care about CO poisoning..?

Link to article where the pics come from:
(properly placed bonnet vent seems like a good idea)
https://robrobinette.com/S2000Aerodynamics.htm

Other links showing the low pressure area behind a car, where people like to put boat tails to 'fill that vacuum' (your canopy included! ):

https://www.researchgate.net/figure/...fig2_322640200

Car Aerodynamics Basics, How-To & Design Tips ~ FREE!
1) the highest possible pressure will be the forward stagnation point ( Cp + 0.8 on Tesla 3 ( Edgar )
2) the lowest ( but not exhaust-related region ) pressure will be just ahead of the windshield header ( Cp - 0.69 on Model 3).
3) the next lowest area will be under the car at the diffuser ( Cp- 0.37 ).
4) The base pressure of the wake will be at a higher pressure ( Cp -0.16 ).
5) The 'template' has positive pressure at its rear, all around.
------------------------------------------------------------------------------------
The rear spoiler probably allowed re-attached flow to the boot, killed separated flow upstream at a much lower pressure, allowing the attached flow to decelerate before separating at the 'new' rear of the spoiler, increasing base pressure, lowering pressure drag, and total drag.
Yes, there's 'low pressure' in the wake, but it's at a higher relative pressure than elsewhere.
It's why the aft-body is the most crucial part as far as drag goes.
__________________
Photobucket album: http://s1271.photobucket.com/albums/jj622/aerohead2/
  Reply With Quote
The Following User Says Thank You to aerohead For This Useful Post:
Logic (08-16-2022)
Old 08-16-2022, 07:52 AM   #27 (permalink)
EcoModding Apprentice
 
Join Date: Aug 2022
Location: South Africa
Posts: 126
Thanks: 51
Thanked 44 Times in 41 Posts
Quote:
Originally Posted by Vman455 View Post
Gee, if only there were a way to measure aerodynamic pressures on your own car instead of all this guessing and speculation.
Gee thx for the links.
BUT:
One does want somewhere to start your investigations before you go as far as designing and building an exhaust system.
You haven't dashed out with and angle grinder, welder, bender, some pipe and a pressure meter have you..?
  Reply With Quote
Old 08-25-2022, 11:43 AM   #28 (permalink)
Master EcoModder
 
aerohead's Avatar
 
Join Date: Jan 2008
Location: Sanger,Texas,U.S.A.
Posts: 14,924
Thanks: 23,056
Thanked 6,813 Times in 4,335 Posts
Lotus Europa

This will be an interesting project when you get to it.
It's one car that put the 'body' where most place a rear spoiler. Wolf Heinrich Hucho had mentioned in his 2nd-Edition book that, adding a rear spoiler affected drag and lift almost as good as just designing the aft-body to the same 'height.'
If it was Frank Costin who did the design, I applaud him.
At Cd 0.29, the Europa was probably a benchmark for low drag in 1968, when it debuted. It just so happens to intersect the span of the 'slow,' 2.5:1 streamline body of revolution-derived half-body contour I used for the 2007 AST-I.
I got to drive a spyder version at a party in 1969. It remains my favorite sports car. A real slot-car! Elegant. Visceral. No girly-man creature comforts. Just legs-straight-out, buns-on-the-floor, unadulterated performance!
And driven 'conservatively', no doubt, very efficient, naked, off the boat from England.
__________________
Photobucket album: http://s1271.photobucket.com/albums/jj622/aerohead2/
  Reply With Quote
Old 08-27-2022, 11:11 AM   #29 (permalink)
EcoModding Apprentice
 
Join Date: Aug 2022
Location: South Africa
Posts: 126
Thanks: 51
Thanked 44 Times in 41 Posts
Quote:
Originally Posted by aerohead View Post
This will be an interesting project when you get to it.
It's one car that put the 'body' where most place a rear spoiler. Wolf Heinrich Hucho had mentioned in his 2nd-Edition book that, adding a rear spoiler affected drag and lift almost as good as just designing the aft-body to the same 'height.'
If it was Frank Costin who did the design, I applaud him.
At Cd 0.29, the Europa was probably a benchmark for low drag in 1968, when it debuted. It just so happens to intersect the span of the 'slow,' 2.5:1 streamline body of revolution-derived half-body contour I used for the 2007 AST-I.
I got to drive a spyder version at a party in 1969. It remains my favorite sports car. A real slot-car! Elegant. Visceral. No girly-man creature comforts. Just legs-straight-out, buns-on-the-floor, unadulterated performance!
And driven 'conservatively', no doubt, very efficient, naked, off the boat from England.
Thx; yes it's a nice car to start with.
Aero and 649kg.
But some room for improvement left.

The challenge is making changes that are easily reversible so that reverting back to original is easy.
Then I want to keep the "legs-straight-out, buns-on-the-floor, unadulterated performance!" too!

I think perhaps a new thread as I/we're hijacking poor Talos' thread way off course.
  Reply With Quote
Old 08-27-2022, 08:03 PM   #30 (permalink)
Righteous Imaginarian
 
Talos Woten's Avatar
 
Join Date: Jun 2022
Location: Aliquippa PA
Posts: 101

Champrius v3.2 - '09 Toyota Prius
90 day: 58.73 mpg (US)
Thanks: 6
Thanked 93 Times in 48 Posts
Quote:
Originally Posted by Logic View Post
I think perhaps a new thread as I/we're hijacking poor Talos' thread way off course.
No worries. I've already decided not to mess with my air intake, given than my initial tests at changing things all resulting in worse fuel economy. Whatever Toyota is doing in the Prius, it's probably already been optimized.

So feel free to hijack away!

__________________
Currently building Champrius 4.0! Follow starting here:
https://www.instagram.com/p/CeeL6xyFp-k/

and ask in depth questions here:
https://ecomodder.com/forum/showthre...tml#post669277

The goal is 70 mpg this time around.

Stats from Champrius v3.2:
  Reply With Quote
Reply  Post New Thread


Thread Tools




Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2022, vBulletin Solutions Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com