maf vs sd tune????
Well, if you are looking for max potential and streetablility, I would go with one of the 100mm MAF sensor kits. It will allow for virtually no flow loss and still give you the ability for precise compensation for the changing conditions.
I say speed density...then you don't need to spend any money on any new sensors...properly tuned speed density compensates as well...most guys don't even realize that their MAF cars are running a speed density/maf combo below 4000 RPM anyways.
I always laugh when a professional says speed density needs to be re-tuned for changing weather...that just means it wasn't tuned correctly in the first place.
I always laugh when a professional says speed density needs to be re-tuned for changing weather...that just means it wasn't tuned correctly in the first place.
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I can name plenty of flying turbo/blower/naturally aspirated street cars that run awesome with SD.
It really does just come down to the tuner's know how.
Here's an SD turbo car tuned by Bob Kurgan. Spent more time driving his kids around the neighborhood than at the track doing this: http://www.youtube.com/watch?v=Cq4RRTGl0wY
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I guess I should have added...I don't think MAF tuning is a bad thing...if your MAF is there and isn't a restriction...it's a great tool (but using the MAF tables to tune the engine is a bad idea...use the engine tables to tune the engine...the MAF tables are the sensors calibration)...I just see it from the other side of the table though, you (in your NA car) already have the MAP sensor, GM installed it...they also installed every other sensor you need and gave your a very powerful PCM that can model airflow, temp correction and a variety of other things VERY VERY well without the MAF. So IF your existing MAF is a restriction...get it out of there, and tune without it...no need to spend money on something else.
For what it's worth, I run closed loop speed density on my NA car...and on my other car (that I'm still building) I will run closed loop speed density as well...only difference there is it will be 2 or 3 bar (not sure how much boost it will see)...so I'll have to buy a new sensor...but a 2 or 3 bar MAP costs a LOT LESS than some crazy MAF that can measure the airflow from a serious forced induction setup...and then when you get into the electronic trickery and whatnot that guys have to get into for very high airflow through MAF setups...just adds cost and adds stuff that can break...and then when you have a tune based on your MAF tables (because as I said...most people tuning with the MAF are NOT properly tuning the car)...and your expensive aftermarket MAF fails...you're screwed.
For what it's worth, I run closed loop speed density on my NA car...and on my other car (that I'm still building) I will run closed loop speed density as well...only difference there is it will be 2 or 3 bar (not sure how much boost it will see)...so I'll have to buy a new sensor...but a 2 or 3 bar MAP costs a LOT LESS than some crazy MAF that can measure the airflow from a serious forced induction setup...and then when you get into the electronic trickery and whatnot that guys have to get into for very high airflow through MAF setups...just adds cost and adds stuff that can break...and then when you have a tune based on your MAF tables (because as I said...most people tuning with the MAF are NOT properly tuning the car)...and your expensive aftermarket MAF fails...you're screwed.
I ran my 408 in SOLSD with an EFILive COS and it idled just fine with a Texas Speed "Giant" cam. I drove it on the street all of the time and it was great even in traffic. If you are running a big cam with lots of overlap, MAFless will be a little better in my opinion as far as idle and streetability...
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Joined: Aug 2005
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From: Sunny London, UK
MAF maxes out at 512g/sec so there is an inherent limitation with it and the OEM ECU which doesnt exist with Speed Density.
johnster dude, take a look at the intake charge blending tables, if it doent run right, its because its not tuned properly. 2M+ Hemi's cant be wrong.
johnster dude, take a look at the intake charge blending tables, if it doent run right, its because its not tuned properly. 2M+ Hemi's cant be wrong.
i am running a SD tune and it runs perfect all the time.I have a wideband gauge and the only thing that i dont like is if the temp outside gets down in the 40's or 50's it will run rich at WOT.Thats it though the rest of the time it is spot on and the throttle response is impressive.Dont have to worry about any maf restricting the engines breathing.If you have a good tuner who will give your car a good SD tune then do it.
i am running a SD tune and it runs perfect all the time.I have a wideband gauge and the only thing that i dont like is if the temp outside gets down in the 40's or 50's it will run rich at WOT.Thats it though the rest of the time it is spot on and the throttle response is impressive.Dont have to worry about any maf restricting the engines breathing.If you have a good tuner who will give your car a good SD tune then do it.
Last edited by Mike454SS; Feb 8, 2009 at 11:42 PM.
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Joined: Apr 2002
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From: So.Cal.
If you look at the units of the "VE" table you will see that they are: g*K/kPa
In other words, the "VE" table is normalized for intake charge temperature and pressure...
Intake charge temperature is absolute temperature computed from a blend of ECT and IAT.
Pressure is absolute pressure.
The gas law says: PV = nRT = (m/M)RT where R is the Universal Gas Constant, n is mole count (proportional to cylinder airmass), M is molar mass (constant), m is the cylinder airmass, V is cylinder volume, P is intake charge pressure, T is intake charge temperature (the steady state conditions of the air in the cylinder before it was compressed in a very short time).
If you rearrange that, you see that that "normalized" airmass mT/P = VM/R which depends only on volume (since M and R are constant).
The PCM takes pressure and temperature into account.
If SD doesn't work right, then something else is incorrect or is being modeled wrong.
In other words, the "VE" table is normalized for intake charge temperature and pressure...
Intake charge temperature is absolute temperature computed from a blend of ECT and IAT.
Pressure is absolute pressure.
The gas law says: PV = nRT = (m/M)RT where R is the Universal Gas Constant, n is mole count (proportional to cylinder airmass), M is molar mass (constant), m is the cylinder airmass, V is cylinder volume, P is intake charge pressure, T is intake charge temperature (the steady state conditions of the air in the cylinder before it was compressed in a very short time).
If you rearrange that, you see that that "normalized" airmass mT/P = VM/R which depends only on volume (since M and R are constant).
The PCM takes pressure and temperature into account.
If SD doesn't work right, then something else is incorrect or is being modeled wrong.
Last edited by joecar; Feb 9, 2009 at 08:58 PM.
