Speed density defined - Jeep Wrangler Forum
Jeep Wrangler Forum

Go Back   Jeep Wrangler Forum > JK Jeep Wrangler Forum > JK General Discussion Forum

Join Wrangler Forum Today


Reply
 
Thread Tools

Please support our sponsors and let them know you heard about them on WranglerForum.com
Old 04-14-2012, 03:17 PM   #1
Jeeper
 
jmcd's Avatar
 
Join Date: Jul 2011
Posts: 195
Images: 1
Speed density defined

Thought this might interest some 3.8rs, You know, the engine with no ticks.


Speed Density systems accept input from sensors that measure engine speed (in rpm) and load (manifold vacuum in kPa), then the computer calculates airflow requirements by referring to a much larger (in comparison to an N Alpha system) preprogrammed lookup table, a map of thousands of values that equates to the engine’s volumetric efficiency (VE) under varying conditions of throttle position and engine speed. Engine rpm is provided via a tach signal, while vacuum is transmitted via an intake manifold-mounted Manifold Air Pressure (MAP) sensor. Since air density changes with air temperature, an intake manifold-mounted sensor is also used.

Production-based Speed Density computers also utilize an oxygen (O2) sensor mounted in the exhaust tract. The computer looks at the air/fuel ratio from the O2 sensor and corrects the fuel delivery for any errors. This helps compensate for wear and tear and production variables. Other sensors on a typical Speed Density system usually include an idle-air control motor to help regulate idle speed, a throttle-position sensor that transmits the percentage of throttle opening, a coolant-temperature sensor, and a knock sensor as a final fail-safe that hears detonation so the computer can retard timing as needed.


Because a Speed Density system still has no sensors that directly measure engine airflow, all the fuel mapping points must be preprogrammed, so any significant change to the engine that alters its VE requires reprogramming the computer.



Read more: Electronic Fuel Injection Mass Flow vs. Speed Density- Car Craft Magazine

__________________
It is not the critic who counts; not the man who points out how the strong man stumbles,The credit belongs to the man who is actually in the arena,whose face is marred by dust and sweat and blood
jmcd is offline   Quote Quick Reply
Old 04-14-2012, 03:42 PM   #2
MallCrawler

WF Supporting Member
::WF Moderator::
 
kjeeper10's Avatar
 
Join Date: Feb 2011
Location: Connecticut
Posts: 35,854
Someone please translate in English please

kjeeper10 is online now   Quote Quick Reply
Old 04-14-2012, 03:44 PM   #3
Jeeper
 
Another Guy In A Jeep's Avatar
 
Join Date: Sep 2011
Location: Kenosha, WI
Posts: 2,467
I'll just pretend I understood that
__________________
17 and ignorant
Another Guy In A Jeep is offline   Quote Quick Reply
Old 04-14-2012, 04:04 PM   #4
Jeeper
 
JEEPDON's Avatar
 
Join Date: Jan 2011
Location: Over the hill
Posts: 1,432
Quote:
Originally Posted by kjeeper10 View Post
Someone please translate in English please
Ain't that what he just did??? But that is OK-- I don't understand it either
__________________
Don
Happy Jeeping
Experience= What you get right after you need it the most!!
JEEPDON is offline   Quote Quick Reply
Old 04-14-2012, 04:14 PM   #5
Jeeper
 
Casotakar1229's Avatar
 
Join Date: Mar 2012
Posts: 2,214
3.6er here...derp derp...herp derp. don't understand. oh well
Casotakar1229 is offline   Quote Quick Reply
Old 04-14-2012, 04:14 PM   #6
Jeeper
 
IP0VV3R's Avatar
 
Join Date: Aug 2011
Location: Tulsa, Oklahoma
Posts: 9,121
You lost me after the kPa thing
__________________
Zack
IP0VV3R is offline   Quote Quick Reply
Old 04-14-2012, 04:56 PM   #7
Jeeper
 
JeeperJake's Avatar
 
Join Date: Jul 2010
Posts: 2,895
....it's good being Dense.....
__________________
get in--buckle up--hang on
"soothing agricultural implement/personal servant/Walter Mitty multidimensional access utility device conveniently travels on pavement when necessary and often keeps me warm/cool/dry/soothed as needed."
JeeperJake is offline   Quote Quick Reply
Old 04-14-2012, 05:08 PM   #8
Jeeper
 
Join Date: Apr 2012
Posts: 17
I am not the most savy tech guy but it sounds like it is a pre programmed load fuel map that "learns" or changes within a set variables. Sounds like a decent idea. But I could very easily be wrong.
ivel_86 is offline   Quote Quick Reply
Old 04-14-2012, 05:24 PM   #9
Jeeper
 
jmcd's Avatar
 
Join Date: Jul 2011
Posts: 195
Images: 1
Well in laymens terms it means that it is "OVER ENGINEERED", too much computer crap that controls nearly every move of the engine making it hard to add HP without the computer saying OH NO YOU DIDN'T!
__________________
It is not the critic who counts; not the man who points out how the strong man stumbles,The credit belongs to the man who is actually in the arena,whose face is marred by dust and sweat and blood
jmcd is offline   Quote Quick Reply
Old 04-14-2012, 06:18 PM   #10
Jeeper
 
Dick Blonov's Avatar
 
Join Date: Oct 2011
Location: Montreal (the big one)
Posts: 544
Quote:
Originally Posted by jmcd View Post
Well in laymens terms it means that it is "OVER ENGINEERED", too much computer crap that controls nearly every move of the engine making it hard to add HP without the computer saying OH NO YOU DIDN'T!
Ah, I miss my manual choke. What the hell, let's go back to manual spark advance!!!




DB

Dick Blonov is offline   Quote Quick Reply
Reply

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Jeep Wrangler Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools

Posting Rules
You may post new threads
You may 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




Download our Mobile App

» Featured Product

All times are GMT -5. The time now is 04:11 PM.



Jeep®, Wrangler, Liberty, Wagoneer, Cherokee, and Grand Cherokee are copyrighted and trademarked to Chrysler Motors LLC.
Wranglerforum.com is not in any way associated with the Chrysler Motors LLC