SD is Speed Density.
SD is Speed Density.
T-RAV99 GMC | 5.3 | Skinny White Guy Tuned
Can you give more info lolOriginally Posted by bangbangskeetskeet
OMG... lol, like what is speed density, does it have to do with higher air flow?
hahahahahaha... speed density is when the pcm uses only the volumetric efficiency table to adjust injector pulse width. The VE table is basically a table of numbers that represent the pumping effeciency of the engine. SD uses the IAT, and MAP sensors and engine rpm to reference what value of the VE table to use to adjust fueling. Stock our trucks use a combination of the MAF and the VE table. It uses the VE table at low rpm/low air flow and switches over to the MAF at higher rpm/airflow since the MAF doest get stable readings with low airflow. People run SD to be able to copletely do away with the MAF so they can route the intake without having to worry about it and several other reasons. Some will say SD is better and some say using the MAF is better. I dont really know. I like the MAF myself because it measures actual dynamic airflow and is not a "guesstimation" like the VE table. That is why when you make a change to the airflow to or from the engine (ex. headers, cam, heads, intake etc.) you need to retune the the ve and maf tables in the pcm to decrease/add fuel to compensate for the increased/decreased pumping effeciency/airflow of the engine. Thats just my .02 and understanding of the subject. I might have missed a few things or be wrong on a thing or two but anyone is welcome to correct me
2008 GMC Sierra SLE....370ci LY6 with some goodies
1995 C2500- LS1 swap with a mp112
build thread- http://www.ls1truck.com/forums/lsx-t...-ls1-swap.html
Thank you, so where would I get an SD... cause my MAF is messing up.hahahahahaha... speed density is when the pcm uses only the volumetric efficiency table to adjust injector pulse width. The VE table is basically a table of numbers that represent the pumping effeciency of the engine. SD uses the IAT, and MAP sensors and engine rpm to reference what value of the VE table to use to adjust fueling. Stock our trucks use a combination of the MAF and the VE table. It uses the VE table at low rpm/low air flow and switches over to the MAF at higher rpm/airflow since the MAF doest get stable readings with low airflow. People run SD to be able to copletely do away with the MAF so they can route the intake without having to worry about it and several other reasons. Some will say SD is better and some say using the MAF is better. I dont really know. I like the MAF myself because it measures actual dynamic airflow and is not a "guesstimation" like the VE table. That is why when you make a change to the airflow to or from the engine (ex. headers, cam, heads, intake etc.) you need to retune the the ve and maf tables in the pcm to decrease/add fuel to compensate for the increased/decreased pumping effeciency/airflow of the engine. Thats just my .02 and understanding of the subject. I might have missed a few things or be wrong on a thing or two but anyone is welcome to correct me
Any reputable person who does tunes. I don't know how hard it is to purchase a new MAF, but I know how much you're going to spend on an SD tune...
1969 Chevy RCLB C10 350/TH400 SOLD
2007 Chevy RCSB 4.8 4x4 LS SOLD
2008 Chevy RCSB 5.3 4x4 LT SOLD
2010 Chevy CCSB 6.2 4x4 LT SOLD
2005 GMC CCLB DRW 6.6 Duramax 4x4 191,000 and counting
2013 FORD CCSB F350 6.7 Powerstroke 4x4
That and is it really needed? Why not just purchase a new MAF from a dealership or parts store and take care of the issue. Hell why not even try and clean the sensor?
T-RAV99 GMC | 5.3 | Skinny White Guy Tuned
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