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

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 05-08-2010, 09:02 PM   #21 (permalink)
Master EcoModder
 
Join Date: Apr 2010
Location: belgium, wi
Posts: 262

Bus - '94 Ford School Bus huge

Stupid - '01 Chevy Blazer LS
90 day: 21.38 mpg (US)

hawk - '00 Honda Superhawk
Thanks: 2
Thanked 24 Times in 19 Posts
Well, there is definitely a problem with people thinking that making it bigger will make it better. A lot has to go into the calcs, including the VE of the engine, the rpms where you want the power, camshafts, intake length, etc etc. All this goes into designing a good performance exhaust. Some aftermarket companies just make everything bigger, which if coupled with 0 changes to the engine usually net a decrease in total power. Turbo engines do operate under different principles. The critical portions are the header/manifold up to the turbo, which people typically leave alone, and the pressure difference between either side of the exhaust turbine, which dictates lift on the blades, which effects rpm-boost-power, and so on. There are points of diminishing returns, where the bigger pipes net no increase in power.

  Reply With Quote
The Following User Says Thank You to autoteach For This Useful Post:
Phantom (05-08-2010)
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 05-19-2010, 11:52 AM   #22 (permalink)
EcoModding Lurker
 
Join Date: May 2010
Location: Minneapolis MN
Posts: 4
Thanks: 0
Thanked 0 Times in 0 Posts
Quote:
Originally Posted by ted frater View Post
Can I call on the collective wisdom for help. What difference does it make to throw away the makers exhaust system and fit a larger bore burgess type straight thru silencer. the initial pipe dia out of the turbo is 2,3/4in then it finally comes down to 1,3/4 at the tail pipe.
This would be into to my 97 , mazda RF turbo diesel intercooled vitara?
Theres no point in doing this if the difference is likely to be minmal.
You can do a thorough research on that one to further lighten your decision on what to do with it. Also suggestions here can also help you decide.
  Reply With Quote
Old 05-19-2010, 07:28 PM   #23 (permalink)
slave to the grind
 
TOOQIKK's Avatar
 
Join Date: May 2010
Location: NKY
Posts: 73

Sippy The Slow Sentra - '94 NISSAN SENTRA EX
Team Nissan
90 day: 45.73 mpg (US)
Thanks: 89
Thanked 5 Times in 5 Posts
Send a message via AIM to TOOQIKK
Talking

Quote:
Originally Posted by COcyclist View Post
I don't know about your particular Mazda diesel but I cut off the muffler on my VW diesel and replaced it with a straight pipe, with no real increase in noise. The cat-converter and the turbo quiets the exhaust noise nicely. It may make the turbo more efficient but I didn't see any significant gains in mpg or power. I think the upgraded exhaust may be more of an issue if you are boosting the power on your diesel than it is for high mpg at light engine loads. I deleted the muffler primarily to make more room for a belly pan install.
if it makes the turbo more efficient then you dont have to step on the gas pedal as hard or as long to get to speed that will increase your mpg.
exhaust mods help your top end power and efficiency
intake mods help your lower end power and efficiency

i would recommend a 3" exhaust for a turboed vehicle.
__________________
  Reply With Quote
Old 05-21-2010, 09:52 AM   #24 (permalink)
Aero Wannabe
 
COcyclist's Avatar
 
Join Date: Dec 2007
Location: NW Colo
Posts: 738

TDi - '04 VW Golf
TEAM VW AUDI Group
90 day: 53.2 mpg (US)
Thanks: 705
Thanked 218 Times in 169 Posts
Quote:
Originally Posted by autoteach View Post
Turbo engines do operate under different principles. The critical portions are the header/manifold up to the turbo, which people typically leave alone, and the pressure difference between either side of the exhaust turbine, which dictates lift on the blades, which effects rpm-boost-power, and so on. There are points of diminishing returns, where the bigger pipes net no increase in power.
So Autoteach, I read the Exhaust Theory 101 and I get the exhaust scavenging concept. But in a turbo car, does this mean that the whirring turbine blades eliminate the pulses at the turbo and therefore from that point on bigger is better, even for ecodriving? A 3" exhaust on a 1.9 TDI could increase mpg at light engine loads?
__________________
60 mpg hwy highest, 50+mpg lifetime
TDi=fast frugal fun
https://ecomodder.com/forum/showthre...tml#post621801


Quote:
Originally Posted by freebeard View Post
The power needed to push an object through a fluid increases as the cube of the velocity. Mechanical friction increases as the square, so increasing speed requires progressively more power.
  Reply With Quote
Old 05-21-2010, 04:57 PM   #25 (permalink)
Master EcoModder
 
aerohead's Avatar
 
Join Date: Jan 2008
Location: Sanger,Texas,U.S.A.
Posts: 15,877
Thanks: 23,951
Thanked 7,219 Times in 4,646 Posts
science?

Quote:
Originally Posted by ted frater View Post
Can I call on the collective wisdom for help. What difference does it make to throw away the makers exhaust system and fit a larger bore burgess type straight thru silencer. the initial pipe dia out of the turbo is 2,3/4in then it finally comes down to 1,3/4 at the tail pipe.
This would be into to my 97 , mazda RF turbo diesel intercooled vitara?
Theres no point in doing this if the difference is likely to be minmal.
So far,to my knowledge,no one has done a scientific investigation on exhaust systems modification.
If you would like to be the first it would be great.
You would first need to drill and install pressure taps along the entire length of the exhaust system,at every transition,in every component,stem to stern.
Secondly,you would need to operate your car on a chassis dynamometer under all transient load and steady load conditions,constructing a complete manometer histogram of the exhaust system,normalized to standard temperature and barometric pressure,while simultaneously recording horsepower.
After which,you would repeat the process with the modified exhaust system,and after data reduction,compare the two sets of data to ascertain at which point the modification yielded a beneficial performance enhancement.
Short of all this,it would be very difficult to know any specifics.
  Reply With Quote
Old 05-22-2010, 02:18 AM   #26 (permalink)
Master EcoModder
 
Join Date: Apr 2010
Location: belgium, wi
Posts: 262

Bus - '94 Ford School Bus huge

Stupid - '01 Chevy Blazer LS
90 day: 21.38 mpg (US)

hawk - '00 Honda Superhawk
Thanks: 2
Thanked 24 Times in 19 Posts
Quote:
Originally Posted by COcyclist View Post
So Autoteach, I read the Exhaust Theory 101 and I get the exhaust scavenging concept. But in a turbo car, does this mean that the whirring turbine blades eliminate the pulses at the turbo and therefore from that point on bigger is better, even for ecodriving? A 3" exhaust on a 1.9 TDI could increase mpg at light engine loads?
Sorry it took so long for me to reply...
Pressure waves, for the most part, would be reflected at the turbo and back towards the cylinders. The critical aspect that is occurring before and after the turbo (remember that each vane is a wing, and lift has to do with the pressure difference above and below, along with SA), so less restriction after the turbo will definitely increase turbo pressure and spooling at all rpms. To understand why this is good for all driving, including ecodriving, you need to look at engine efficiency:


http://www.rm-indy.com/compression_vs_boost.htm

By increasing boost, you increase thermal efficiency, or power output, which requires less throttle, and less fuel (see thermal efficiency). Turbo vehicles see gains after the turbo in both low/top end power and mpg.
  Reply With Quote
The Following User Says Thank You to autoteach For This Useful Post:
COcyclist (05-24-2010)
Old 05-24-2010, 12:48 PM   #27 (permalink)
Aero Wannabe
 
COcyclist's Avatar
 
Join Date: Dec 2007
Location: NW Colo
Posts: 738

TDi - '04 VW Golf
TEAM VW AUDI Group
90 day: 53.2 mpg (US)
Thanks: 705
Thanked 218 Times in 169 Posts
In that case I would recommend TDI owners ditch the 14 lb. muffler for a straight pipe. When my factory exhaust rusts out I'll go oversize from the turbo back. This sounds like one of those rare cases where you get both more power and better economy at the same time.
__________________
60 mpg hwy highest, 50+mpg lifetime
TDi=fast frugal fun
https://ecomodder.com/forum/showthre...tml#post621801


Quote:
Originally Posted by freebeard View Post
The power needed to push an object through a fluid increases as the cube of the velocity. Mechanical friction increases as the square, so increasing speed requires progressively more power.
  Reply With Quote
Old 05-26-2010, 02:10 PM   #28 (permalink)
Potential EcoModder
 
Join Date: May 2010
Location: Iowa City
Posts: 11

Trumpet - '09 Triumph Daytona 675
Thanks: 0
Thanked 0 Times in 0 Posts
I'm not sure if it has been mentioned, but turbos do like to have back-pressure from the exhaust.
  Reply With Quote
Old 05-26-2010, 05:16 PM   #29 (permalink)
Aero Wannabe
 
COcyclist's Avatar
 
Join Date: Dec 2007
Location: NW Colo
Posts: 738

TDi - '04 VW Golf
TEAM VW AUDI Group
90 day: 53.2 mpg (US)
Thanks: 705
Thanked 218 Times in 169 Posts
Quote:
Originally Posted by JRobbins View Post
I'm not sure if it has been mentioned, but turbos do like to have back-pressure from the exhaust.
Please include links to documents or tests supporting your claim.
__________________
60 mpg hwy highest, 50+mpg lifetime
TDi=fast frugal fun
https://ecomodder.com/forum/showthre...tml#post621801


Quote:
Originally Posted by freebeard View Post
The power needed to push an object through a fluid increases as the cube of the velocity. Mechanical friction increases as the square, so increasing speed requires progressively more power.
  Reply With Quote
Old 05-26-2010, 06:05 PM   #30 (permalink)
EcoModding Apprentice
 
micondie's Avatar
 
Join Date: Mar 2009
Location: Western Mass
Posts: 104

moby van - '03 Dodge Caravan SE
90 day: 19.74 mpg (US)
Thanks: 0
Thanked 5 Times in 5 Posts
try this site for basics:Turbo Vs. Supercharger Power Consumption | eHow.com

  Reply With Quote
Reply  Post New Thread


Thread Tools


Similar Threads
Thread Thread Starter Forum Replies Last Post
New CVT transmission electric-assist with electric assist Ptero Fossil Fuel Free 2 09-23-2010 10:41 PM
exhaust system: resonator bgd73 General Efficiency Discussion 3 08-05-2009 09:46 AM
Exhaust system question saunders1313 Hypermiling / EcoDriver's Ed 23 03-01-2009 02:19 AM
2006 in review: mods vs. technique. And the winner is... MetroMPG Hypermiling / EcoDriver's Ed 16 12-10-2007 07:46 AM



Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com