Super Unleaded??
Technical Article Contributor
Joined: Dec 1997
Posts: 9,417
Likes: 11
From: Windsor,Ontario,Canada
The MAF has two filaments that are exposed to the air. One is heated to about 200°C above ambient and the other is left at ambient temp. If you try to clean it when the filament is hot you will break it. First thing in the morning is best. Remove the MAF from the Sampling tube, dip the Q-tip in Windex and clean both filaments. Use the dry end to wipe. Gently is the key here.
To get to it you have to remove the air filter and look down the Air Cleaner outlet. You will notice that the Mass air flow sensor plate is snapped to the outlet. I just reach in with a long Q-tip without removing the MAF Sensor.
FYI the amount of current required to maintain 200°C over ambient is proportional to the air mass flowing. The PCM measures the current and uses that to calculate the amount of fuel required. If it is dirty.......
JMC
To get to it you have to remove the air filter and look down the Air Cleaner outlet. You will notice that the Mass air flow sensor plate is snapped to the outlet. I just reach in with a long Q-tip without removing the MAF Sensor.
FYI the amount of current required to maintain 200°C over ambient is proportional to the air mass flowing. The PCM measures the current and uses that to calculate the amount of fuel required. If it is dirty.......
JMC
Senior Member
Joined: Dec 2002
Posts: 1,558
Likes: 3
From: Eastern TN
Originally posted by dbarbee
<SNIP>... BTW: I appreciate the respectful feedback, no offense taken or intended ...<SNIP>
<SNIP>... BTW: I appreciate the respectful feedback, no offense taken or intended ...<SNIP>
I know I tend to write very "clinically" (direct quote from a co-worker) and that sometimes people take it that I am arguing, flaming, etc.
I've been making a concerted effort to improve in that area, both at work and here.
Thanks to 01 XLT Sport for the octane explanations. I learned something (again) today.
Last edited by B-Man; Sep 17, 2003 at 05:10 PM.
Senior Member
Joined: Jul 2004
Posts: 6,200
Likes: 39
From: Easton, Pa.
I am with the chem engineer on the fuel octane issue.
No one has answered what and how the knock actually comes about.
I will try to give this in three parts.
1. The specified 87 grade gas is ignited at X number of degrees before top center.
The optumin point for max combustion pressure is somewhere between 10 and 20* after top center to have max mechanical advantage on the crank conversion to rotational force.
2. Replace the fuel with 93 for example.
The fuel fires at the same point before top center, burns slower, and ends up producing max pressure later in the crank rotation. This waists power contained in the fuel.
3. Ping ( spark knock) is produced when the fuel is ignited 'to soon' producing max combustion pressure TO NEAR TOP DEAD CENTER when the piston/rod and crank pin are in near vertical aligment and CANNOT move in response to the pressure.
The results of this is the ringing of the piston ,cylinder wall, head area, crank, and block that you hear as a knocking sound called ping. Ping is a slang term for spark knock.
There are many facets to all this that must be kept seperated when discussing octane requirements for a peticular combination.
One example is the use of a blower vs octane.
Force feeding an engine raises the cylinder combustion pressure so high that it forces a fuel with a specified burn rate under normal conditions to increase it burn rate under the higher pressures mandating an increase in octane to slow the burn rate back down to that 10 to 20* after top center range as said above.
There are many other factors that can influence combustion points and burn rates.
All the replies were like throwing the bit and pieces into the air and letting the wind scatter them. Few could pick anything out of them.
There is no magic extra power in higher octane fuel. Just that min octane requirement has to be matched with the conditions the engine is set to and some internal physical conditions as well as incoming air temp.
No one has answered what and how the knock actually comes about.
I will try to give this in three parts.
1. The specified 87 grade gas is ignited at X number of degrees before top center.
The optumin point for max combustion pressure is somewhere between 10 and 20* after top center to have max mechanical advantage on the crank conversion to rotational force.
2. Replace the fuel with 93 for example.
The fuel fires at the same point before top center, burns slower, and ends up producing max pressure later in the crank rotation. This waists power contained in the fuel.
3. Ping ( spark knock) is produced when the fuel is ignited 'to soon' producing max combustion pressure TO NEAR TOP DEAD CENTER when the piston/rod and crank pin are in near vertical aligment and CANNOT move in response to the pressure.
The results of this is the ringing of the piston ,cylinder wall, head area, crank, and block that you hear as a knocking sound called ping. Ping is a slang term for spark knock.
There are many facets to all this that must be kept seperated when discussing octane requirements for a peticular combination.
One example is the use of a blower vs octane.
Force feeding an engine raises the cylinder combustion pressure so high that it forces a fuel with a specified burn rate under normal conditions to increase it burn rate under the higher pressures mandating an increase in octane to slow the burn rate back down to that 10 to 20* after top center range as said above.
There are many other factors that can influence combustion points and burn rates.
All the replies were like throwing the bit and pieces into the air and letting the wind scatter them. Few could pick anything out of them.
There is no magic extra power in higher octane fuel. Just that min octane requirement has to be matched with the conditions the engine is set to and some internal physical conditions as well as incoming air temp.