Speed Density
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Joined: Mar 2001
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From: Doghouse ······································ Car: 1989 Formula 350 Vert Engine: 350 L98 Transmission: 700R4 Axle/Gears: B&W 3.27
Car: 87 Formula T-Top, 87 Formula HT
Engine: 5.1L TPI, 5.0L TPI
Transmission: 700R4, M5
Axle/Gears: Sag 3.73, B&W 3.45
Speed Density, AKA MAP, (Manifold Air (atmosphereic or absolute) Pressure) is a system that meauers the amound of Vacuum in your engine, and relates it to the RPM of the engine, temp of the engine, the temp of the air coming into your engine, the O2 sensor, throttle position sensor & some other stuff, to calculate the amount of fuel needed to inject into the engine.
MAF or Mas Air Flow, works the same way EXCEPT it measures the amount of air coming into the engine by a MAF or somtimes called a MAS sensor. The MAF sensor has a wire inside of it that measures the amount of air by measuring the resistance of that wire. As the Air travels through the sensor it cools the wire and the ECM calculates the speed of the air.
Simply put:
MAP/SD - measures the pressure in the intake Manifold for injector duration.
MAF/MAS - Measures the amount of air entering the intake for injector duration.
John
------------------
87 Formula Yellow/Black
Engine & Transmission
.040 over 5.0 converted to TPI, 9.5:1 Compression, SLP Cam Dur 206/212, Lift 480/487, Cent Line 112, SLP headers, SLP cat-back exhaust, K&N Airfilter, Modified Stock cold air intake, Ported & polished Stock TPI intake, Holley Adjustable Fuel Press regulator, AC Rapidfire Spark Plugs.
Gil Younger (no yo-yo) Shift Kit, Aluminum Driveshaft, 3.73 Posi gear
Suspension & Brakes:
Baer 12" brakes 4 wheels, KYB AGX Adjustable Shocks & struts, Hotchkis strut tower brace, South side machine frame connectors, Custom reinforced control arms and pan hard bar.
Interior:
Custom Leather interior, CUSTOM Yellow Gauge Faces, Kenwood Receiver, Pioneer Speakers, Kicker Substations, Kenwood 10 Disk Changer, Pioneer Amp.
87 Formula TPI (5 Speed) Yellow/Gray STOCK
1967 Buick Riviera 430hp Turns high 14's (Not bad for 4300 lbs)
83 Camaro (Parts)
83 T/A (parts)
http://www.3rdgenformula.com
MAF or Mas Air Flow, works the same way EXCEPT it measures the amount of air coming into the engine by a MAF or somtimes called a MAS sensor. The MAF sensor has a wire inside of it that measures the amount of air by measuring the resistance of that wire. As the Air travels through the sensor it cools the wire and the ECM calculates the speed of the air.
Simply put:
MAP/SD - measures the pressure in the intake Manifold for injector duration.
MAF/MAS - Measures the amount of air entering the intake for injector duration.
John
------------------
87 Formula Yellow/Black
Engine & Transmission
.040 over 5.0 converted to TPI, 9.5:1 Compression, SLP Cam Dur 206/212, Lift 480/487, Cent Line 112, SLP headers, SLP cat-back exhaust, K&N Airfilter, Modified Stock cold air intake, Ported & polished Stock TPI intake, Holley Adjustable Fuel Press regulator, AC Rapidfire Spark Plugs.
Gil Younger (no yo-yo) Shift Kit, Aluminum Driveshaft, 3.73 Posi gear
Suspension & Brakes:
Baer 12" brakes 4 wheels, KYB AGX Adjustable Shocks & struts, Hotchkis strut tower brace, South side machine frame connectors, Custom reinforced control arms and pan hard bar.
Interior:
Custom Leather interior, CUSTOM Yellow Gauge Faces, Kenwood Receiver, Pioneer Speakers, Kicker Substations, Kenwood 10 Disk Changer, Pioneer Amp.
87 Formula TPI (5 Speed) Yellow/Gray STOCK
1967 Buick Riviera 430hp Turns high 14's (Not bad for 4300 lbs)
83 Camaro (Parts)
83 T/A (parts)
http://www.3rdgenformula.com
TGO Supporter
Joined: Jul 1999
Posts: 10,907
Likes: 5
From: The Bone Yard
Car: Death Mobile
Engine: 666 c.i.
Okfoz, gave a pretty good explanation on the difference between the two. I will add that the way the two systems calculates the incoming air is completely different and thus leads to some of the fundamental problems with each.
SD needs the MAT, the engine displacement and MAP reading (which is the inverse of Vacuum...kind of) to perform its calculation of incoming air flow. The system if virtually instantaneous can handle virtually ANY Naturally Aspirated SBC up to around 8 Liters (480+ C.I.).
MAF relies on the MAF Sensor to measure the air. It does not need to know the Engine Size or the incoming air temperature to determine the air flow...the MAF sensor does it all. MAF produces a more stable value while cruising than SD. It is limited on how large an engine you can run because the MAF system used on our cars is limited to 255 gm/sec.
Once setup, MAF does not generally have to be "tweaked" (though it is not a bad idea to do so) for engine changes, but large cams do cause a problem with MAF due to "reversion" through the intake at low RPMs.
Also, from a tuning perspective, MAF is easier to setup (MAF Scalar tables) which work like "steps" for a range of values. The disadvantage is that you may find yourself a little lean at on end of the "step boundary" and a little rich at the other end. But, in closed loop, this is not a problem for the average person as the O2 sensor makes the "final adjustment".
SD allows you to precisely set a specific value for an RPM/Load value, thus it is possible to get a "closer" reading. But, again, for the average person, they generally are not as "patient" to do all the work necessary to get those precise readings. But in reality, it is not all that hard as you just take a few LONG DRIVES and use the average INT readings to calculate them.
For a basically stock engine, stay with the system you have (except if you have a 1985, then you should consider converting to a 1989 type system...which is the preferred MAF system). Any 1986-1988 can be converted to a 1989 system by disabling the Cold Start Injector and running a 1989 Memcal.
But, if you are going to run a large cam, pull extreme rpms or increase the displacement, you should consider converting to SD. Also, if you are having problems with your MAF sensor, the cost of the conversion may be cheaper than the replacing the Sensor/Burn off relay. The MAF sensor seems to be more prone to failure than the MAP sensor used on SD....the MAP sensor is a lot cheaper too.
If you want to use a "power adder", like a supercharger, neither system adequately handles boost. The MAF gets maxed out at 255 gm/sec and the SD's MAP sensor is limited to 1 bar. You can replace the MAP sensor with a 2 bar sensor, but the internal tables are still limited to 100 kpa so you still end up "cludging" the code to make a 2 bar MAP sensor work.
Currently, converting to the 749 ecm used in the Syclones/Typhoons is the best solution for "boost" applications.
SD needs the MAT, the engine displacement and MAP reading (which is the inverse of Vacuum...kind of) to perform its calculation of incoming air flow. The system if virtually instantaneous can handle virtually ANY Naturally Aspirated SBC up to around 8 Liters (480+ C.I.).
MAF relies on the MAF Sensor to measure the air. It does not need to know the Engine Size or the incoming air temperature to determine the air flow...the MAF sensor does it all. MAF produces a more stable value while cruising than SD. It is limited on how large an engine you can run because the MAF system used on our cars is limited to 255 gm/sec.
Once setup, MAF does not generally have to be "tweaked" (though it is not a bad idea to do so) for engine changes, but large cams do cause a problem with MAF due to "reversion" through the intake at low RPMs.
Also, from a tuning perspective, MAF is easier to setup (MAF Scalar tables) which work like "steps" for a range of values. The disadvantage is that you may find yourself a little lean at on end of the "step boundary" and a little rich at the other end. But, in closed loop, this is not a problem for the average person as the O2 sensor makes the "final adjustment".
SD allows you to precisely set a specific value for an RPM/Load value, thus it is possible to get a "closer" reading. But, again, for the average person, they generally are not as "patient" to do all the work necessary to get those precise readings. But in reality, it is not all that hard as you just take a few LONG DRIVES and use the average INT readings to calculate them.
For a basically stock engine, stay with the system you have (except if you have a 1985, then you should consider converting to a 1989 type system...which is the preferred MAF system). Any 1986-1988 can be converted to a 1989 system by disabling the Cold Start Injector and running a 1989 Memcal.
But, if you are going to run a large cam, pull extreme rpms or increase the displacement, you should consider converting to SD. Also, if you are having problems with your MAF sensor, the cost of the conversion may be cheaper than the replacing the Sensor/Burn off relay. The MAF sensor seems to be more prone to failure than the MAP sensor used on SD....the MAP sensor is a lot cheaper too.
If you want to use a "power adder", like a supercharger, neither system adequately handles boost. The MAF gets maxed out at 255 gm/sec and the SD's MAP sensor is limited to 1 bar. You can replace the MAP sensor with a 2 bar sensor, but the internal tables are still limited to 100 kpa so you still end up "cludging" the code to make a 2 bar MAP sensor work.
Currently, converting to the 749 ecm used in the Syclones/Typhoons is the best solution for "boost" applications.
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