airflow - is more or less better? - Fuelly Forums

Android Users - Coming Soon! - Migrating from aCar 4.8 to 5.0

Reply
 
Thread Tools Display Modes
 
Old 09-28-2005, 02:56 PM   #1
Driving on E
 
Matt Timion's Avatar
 
Join Date: Sep 2005
Posts: 3,110
Country: United States
airflow - is more or less better?

I've been thinking about this for a while now. I guess this goes along with the question of Horsepower and fuel economy that I raised not too long ago.

So, back to the question.

Is it better to give MORE air to your engine, or less air? Some people say that adding a good exhaust manifold and a wide exhaust pipe will give them better mpg (one guy claims a 50 miles-per-tank increase).

but if this is the case, why do all economy builds (I can only think of Hondas right now - the HF, VX, CX, etc.) have smaller than normal intake manifolds? Am I really to believe that Honda's engineers got it wrong when they build their engines? Should they have put massive intakes instead of tiny ones on these engines?

I'm totally baffled by it. Everyone keeps saying "more air, more air" to increase MPG. All that I can see from that though is more power.

So, tell me why I'm wrong, or tell me why i'm right.
__________________

Matt Timion is offline   Reply With Quote
Old 09-28-2005, 07:23 PM   #2
*shrug*
 
Join Date: Sep 2005
Posts: 6,195
Country: United States
Yo

<a href=http://community.foe.co.uk/cgi-bin/yabb/YaBB.pl/YaBB.pl?board=online_actions;action=display;num=10 60791111 target=_blank>Exhaust something</a>
This is not really about exhaust size, but reducing back pressuring (same thing bigger size does) to increase mpg.
__________________

SVOboy is offline   Reply With Quote
Old 09-29-2005, 07:03 PM   #3
Registered Member
 
Join Date: Sep 2005
Posts: 1
Country: United States
It isn't more air that is

It isn't more air that is increasing fuel economy, it is reducing pumping losses through restrictive exhaust/ intake points.
abeja is offline   Reply With Quote
Old 09-29-2005, 07:09 PM   #4
*shrug*
 
Join Date: Sep 2005
Posts: 6,195
Country: United States
Re: It isn't more air that is

Quote:
Originally Posted by abeja
It isn't more air that is increasing fuel economy, it is reducing pumping losses through restrictive exhaust/ intake points.
So then there would not be much difference between a 5 inch and 2 inch exhaust on my 92 mpg b2, since a 2 inch cat back is sufficient to reduce back pressure? And could you recommend some cheaper headers/exhaust crap that will still serve the purpose of reducing back pressure even if they aren't super race quality?
SVOboy is offline   Reply With Quote
Old 09-29-2005, 10:12 PM   #5
Registered Member
 
kickflipjr's Avatar
 
Join Date: Sep 2005
Posts: 933
Country: United States
Fro mpg the best setup would

Fro mpg the best setup would have the best wind speed velocity. Big exaust pipes slow down air velocity. It's too bad they dodn't make performance intakes in 1 3/4" or 2" size. that would be better then the standard 3"
__________________
2008 EPA adjusted:


Distance traveled by bicycle in 2007= 1,830ish miles
Average commute speed=25mph (yes, that's in a car)
kickflipjr is offline   Reply With Quote
Old 09-30-2005, 09:00 AM   #6
*shrug*
 
Join Date: Sep 2005
Posts: 6,195
Country: United States
Re: Fro mpg the best setup would

Quote:
Originally Posted by kickflipjr
Fro mpg the best setup would have the best wind speed velocity. Big exaust pipes slow down air velocity. It's too bad they dodn't make performance intakes in 1 3/4" or 2" size. that would be better then the standard 3"
Is there some way to figure out hp versus exhaust size versus speed to figure out what be would optimum?
SVOboy is offline   Reply With Quote
Old 09-30-2005, 09:23 AM   #7
Registered Member
 
kickflipjr's Avatar
 
Join Date: Sep 2005
Posts: 933
Country: United States
One side affect of free

One side affect of free flowing intakes/exaust is it might take longer to warm up. My old car (92' sl1) would never go past the 1/3 temp mark in the winter.

I think that the stock size exaust pipe is best for mpg. You might get more HP is high rpms but, you lose HP at low rpms.


http://www.spswebpage.com/tech/index.php?articleID=a5207vs5223

^
on this site they gained several HP by removing the muffler. (but they don't show the dyno sheet under 4000rpm
__________________
2008 EPA adjusted:


Distance traveled by bicycle in 2007= 1,830ish miles
Average commute speed=25mph (yes, that's in a car)
kickflipjr is offline   Reply With Quote
Old 09-30-2005, 07:02 PM   #8
Registered Member
 
Join Date: Sep 2005
Posts: 69
Country: United States
a smaller dia intake and

a smaller dia intake and exhaust will not get you power, lol
dfoxengr is offline   Reply With Quote
Old 09-30-2005, 07:12 PM   #9
*shrug*
 
Join Date: Sep 2005
Posts: 6,195
Country: United States
But!

But will a smaller intake and exhaust gain you mpg or will going larger increase both power and mpg?
SVOboy is offline   Reply With Quote
Old 09-30-2005, 07:22 PM   #10
Registered Member
 
Join Date: Sep 2005
Posts: 69
Country: United States
a 3" exhaust on a stock

a 3" exhaust on a stock civic wont help you. it's all in what your motor needs.
nor will a 1" intake on the same car help you at ALL
you need to "design" your complete engine setup to where all parts work together.
__________________

dfoxengr 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
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Audi S3 AlexC Fuelly Web Support and Community News 2 05-23-2011 03:30 AM
Suggestions needed Matt Timion Fuelly Web Support and Community News 80 03-28-2009 06:37 AM
GS FAQ/Glossary, Busted/Confirmed Mods, Archive SVOboy General Fuel Topics 79 06-09-2008 06:01 AM
Minimize Computer Power Consumption Mighty Mira General Discussion (Off-Topic) 13 12-09-2007 02:27 AM

Powered by vBadvanced CMPS v3.2.3


All times are GMT -8. The time now is 03:05 PM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.