Toyota Yaris Forums - Ultimate Yaris Enthusiast Site
 

 


 
Go Back   Toyota Yaris Forums - Ultimate Yaris Enthusiast Site > Second Generation Toyota Yaris Main Rooms > Fuel Economy Forum
  The Tire Rack

Reply
 
Thread Tools Display Modes
Old 05-03-2009, 01:18 AM   #19
GeneW
Banned
 
Drives: 2008 Yaris
Join Date: Oct 2008
Location: Pennsylvania
Posts: 1,034
Quote:
Originally Posted by marcus View Post
thinking of straight thru muffler but stock pipes..worried about drop in mpg. anyone???????????
I think that you'll derange your system to some degree. As I tried to point out, backpressure seems to matter in terms of chemistry through the catalytic perverter and hence in terms of how the motor runs.

I ran straight pipes on a 75 Chevy Nova for about a year. Reduced the mileage somewhat and I didn't have an ECU that had more computing power than some 1970s vintage fighter jets in it either.

Gene
GeneW is offline   Reply With Quote
Old 05-03-2009, 02:02 AM   #20
07WYarisRS
HardlyDangerous
 
07WYarisRS's Avatar
 
Drives: 09 Yaris LE, H/B, auto
Join Date: Jul 2006
Location: Ridgeway Ontario
Posts: 573
The driver affects the mileage way more then any muffler will

Its the ECu's job to control the fuel system , using the MAFS and O2 sensor readings it will comtrol the amount of fuel needed to maitain the same fuel air mixture...
If one did modify the exhaust so that the engine combustion scavenging is greatly effected and fuel is being waisted... the o2 sensor will pick up the overly rich combustion gasses leaving the cylinders and the ECU will alter the fuel and timing to help control it to maintain the factory set air fuel ratio. Sure this may cost you a MPG or two at the most but, I have found in most cases everything kept the same just freeer flowing muffler actually improved MPG. its not until you get into different intake designs, and complete exhaust systems that you see major mileage changes

Changing the exhaust will slightly alter how efficiently the engine will combust the fuel mixture but on a car with an exhaust system like the yaris (these things have what 3 cat convertors?) VVT-i, the elaborate ECU system the effects from a free flowing exhaust will be very small.

The biggest issue with an open exhaust is the driver...
As a motorcycle mechanic I'm asked this daily and deal with this everyday.
Why after changing to louder pipes and re-jetting does it use so much more fuel...
The answer... the operator.
With a quiet exhaust people tend to ride it or drove it much easier.. why because there is nothing impressive there... however with a loud exhaust people like to HEAR that exhaust and 90% of the time accelerate much harder and to much higher RPMs...
I have explained to many customers that before thier exhaust they would putt putt through town, now you can hear them honkin on it 4 blocks away...
You don't hear the guys on the Stock Hondas and Harleys flogging on it WOT through the gears like the guys with open drag pipes or fart can exhaust....

I challange anyone to drive /ride the same way with both quiet and open exhaust and you will usually find a very small change in MPG.. I understand there is no fun in that though.

I rode my GSX750F for a year with no problems, got 2 speeding tickets within a week after my new Hindle race pipe.... My mileage on the hwy actually went up slightly if I maintain a steady cruise speed, however now that i find myself shifting at red line or higher rpms a lot more fuel mileage suffers a lot when i'm accelerating like a tool...but man o man the pipe sounds sweet.
__________________
The early bird gets the worm, but the second mouse gets the cheese.
07WYarisRS is offline   Reply With Quote
Old 05-03-2009, 09:14 AM   #21
marcus
toyota
 
marcus's Avatar
 
Drives: 2007 Yaris RS Blazed
Join Date: Oct 2006
Location: toronto, canada
Posts: 3,637
anyways i got it on..i got it on and its louder than i wanted atleast on the inside..outside wise its sound wicked..but the internal drone is annoying me..*sigh* time to adda resonator.. i going for extra flow not extra loud..damn it.
marcus is offline   Reply With Quote
Old 05-03-2009, 11:16 AM   #22
WeeYari
 
WeeYari's Avatar
 
Drives: 06 Polar White 5dr, 13 Soul 4u
Join Date: Oct 2008
Location: Georgetown, Ontario, Canada
Posts: 5,739
Pics?
__________________
WeeYari is offline   Reply With Quote
Old 05-03-2009, 12:29 PM   #23
GeneW
Banned
 
Drives: 2008 Yaris
Join Date: Oct 2008
Location: Pennsylvania
Posts: 1,034
Quote:
Originally Posted by 07WYarisRS View Post
The driver affects the mileage way more then any muffler will
Within reason, yes....

I've had cars with plugged catalytic converters..... once the exhaust is sufficiently restricted things get complicated.... Mileage drops off, power is awful and the motor runs hotter.

Quote:
Originally Posted by 07WYarisRS View Post
Its the ECu's job to control the fuel system , using the MAFS and O2 sensor readings it will comtrol the amount of fuel needed to maitain the same fuel air mixture...
If one did modify the exhaust so that the engine combustion scavenging is greatly effected and fuel is being waisted... the o2 sensor will pick up the overly rich combustion gasses leaving the cylinders and the ECU will alter the fuel and timing to help control it to maintain the factory set air fuel ratio. Sure this may cost you a MPG or two at the most but, I have found in most cases everything kept the same just freeer flowing muffler actually improved MPG. its not until you get into different intake designs, and complete exhaust systems that you see major mileage changes
There isn't a set mixture ratio with narrow band O2 sensors. Usually in systems that use a narrow band O2 sensor the ECU will "switch" mixture in a cycle that centers around stoichometric so that the catalytic converter works properly. This is in part because the mixture response curve of a narrow band sensor is highly non-linear beyond a very small deviation away from stoichometric, and then if you go way too far you cannot resolve the mixture. Hence the cycling of mixture gives you an average value close to stoichometric.

Wide band sensors don't have this problem but they are pricey. The electronics is also pricey. The calibration of the wide band system is EXTREMELY pricey.

As I said in my "explanation" - the devil and salvation are in the details. You have to measure the results of changing the exhaust system.


Quote:
Originally Posted by 07WYarisRS View Post
Changing the exhaust will slightly alter how efficiently the engine will combust the fuel mixture but on a car with an exhaust system like the yaris (these things have what 3 cat convertors?) VVT-i, the elaborate ECU system the effects from a free flowing exhaust will be very small.
You've actually seen this in the real world? I would want to see such data.



Quote:
Originally Posted by 07WYarisRS View Post
The biggest issue with an open exhaust is the driver...
As a motorcycle mechanic I'm asked this daily and deal with this everyday.
Why after changing to louder pipes and re-jetting does it use so much more fuel... The answer... the operator.
If you're "rejetting" you're using carbs and probably not using a computer controlled system. I've worked on computer controlled carbs..... never mind.

Opening the jets will make the mixture richer, and MAY improve fuel efficiency if you're sufficiently close to Stoichometric on average.

Quote:
Originally Posted by 07WYarisRS View Post
With a quiet exhaust people tend to ride it or drove it much easier.. why because there is nothing impressive there... however with a loud exhaust people like to HEAR that exhaust and 90% of the time accelerate much harder and to much higher RPMs...

I have explained to many customers that before thier exhaust they would putt putt through town, now you can hear them honkin on it 4 blocks away...
You don't hear the guys on the Stock Hondas and Harleys flogging on it WOT through the gears like the guys with open drag pipes or fart can exhaust....

I challange anyone to drive /ride the same way with both quiet and open exhaust and you will usually find a very small change in MPG.. I understand there is no fun in that though.

I rode my GSX750F for a year with no problems, got 2 speeding tickets within a week after my new Hindle race pipe.... My mileage on the hwy actually went up slightly if I maintain a steady cruise speed, however now that i find myself shifting at red line or higher rpms a lot more fuel mileage suffers a lot when i'm accelerating like a tool...but man o man the pipe sounds sweet.
Yeah, some people like that "wide open" noise. I liked my straight pipes on my Nova. Sounded pretty bad assed.

Gene
GeneW is offline   Reply With Quote
Old 05-03-2009, 12:31 PM   #24
marcus
toyota
 
marcus's Avatar
 
Drives: 2007 Yaris RS Blazed
Join Date: Oct 2006
Location: toronto, canada
Posts: 3,637
here it is..

Quote:
Originally Posted by WeeYari View Post
Pics?
http://www.yarisworld.com/forums/sho...834#post305834
marcus is offline   Reply With Quote
Old 05-03-2009, 08:29 PM   #25
07WYarisRS
HardlyDangerous
 
07WYarisRS's Avatar
 
Drives: 09 Yaris LE, H/B, auto
Join Date: Jul 2006
Location: Ridgeway Ontario
Posts: 573
Quote:
Originally Posted by GeneW View Post


You've actually seen this in the real world? I would want to see such data.
yes
But again i deal with bikes on a daily basis not cars but these engines all basically work the same.
many of my race engine are dialed in using CHT and EGT as well as proper plug reading...
Simple changes like header size and diameter, header shape and length, exhaust size and silencer can and will alter how efficiently the engine runs..
Even a simple slip on/bolt on muffler often requires rejetting.
With EFI bikes the fuel maps are changed to correct any lean or rich mixtures when changing exhaust set ups
There would be no need to rejet or re-map if the efficiency of the engines combustion never changes.
An engine runs leaner when more burnt gasses are allowed to escape, when burnt gasses are kept in the combustion chamber this dilutes the mixture and the power output... Some engines respond much better then others to minor changes and require much larger changes, other it makes very little but a lot of that has to do with valve overlap etc.
__________________
The early bird gets the worm, but the second mouse gets the cheese.
07WYarisRS is offline   Reply With Quote
Old 05-03-2009, 09:23 PM   #26
GeneW
Banned
 
Drives: 2008 Yaris
Join Date: Oct 2008
Location: Pennsylvania
Posts: 1,034
Quote:
Originally Posted by 07WYarisRS View Post
yes
But again i deal with bikes on a daily basis not cars but these engines all basically work the same.
many of my race engine are dialed in using CHT and EGT as well as proper plug reading...
Simple changes like header size and diameter, header shape and length, exhaust size and silencer can and will alter how efficiently the engine runs..
Even a simple slip on/bolt on muffler often requires rejetting.
With EFI bikes the fuel maps are changed to correct any lean or rich mixtures when changing exhaust set ups
There would be no need to rejet or re-map if the efficiency of the engines combustion never changes.
An engine runs leaner when more burnt gasses are allowed to escape, when burnt gasses are kept in the combustion chamber this dilutes the mixture and the power output... Some engines respond much better then others to minor changes and require much larger changes, other it makes very little but a lot of that has to do with valve overlap etc.
The older I get the more I appreciate "real world" experience. Thanks

Gene
GeneW is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Using DFCO to increase your MPG BailOut Fuel Economy Forum 216 08-30-2018 04:15 AM
42.04 MPG straight off the lot! bnther36 General Yaris / Vitz Discussion 25 05-17-2010 06:09 PM
My progression into hypermiling BailOut General Yaris / Vitz Discussion 8 10-13-2009 06:31 PM
Help me see 55 mpg! Loren Fuel Economy Forum 76 04-02-2009 04:23 PM
To accurately measure MPG when should I fill back up. mgthompson General Yaris / Vitz Discussion 17 03-30-2007 10:07 PM


All times are GMT -4. The time now is 04:58 PM.




YarisWorld
Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.