SD vs MAF
08-30-2012, 05:28 PM
#21
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Just finished the SD tune on a customer's car Monday night. On Tuesday he drove it 60 miles to the track getting 23mpg, went 11.42 @ 119.5mph in full street trim, and drove it home. It's all in the tuning, I've seen some real half ***'d tunes where some shops/tuners get lazy...as far as altitude, for cruising closed loop usually keeps things in check...
-Dave
-Dave
08-31-2012, 10:41 AM
#25
Actually a 2 bar will read -14.7 to 14.7psi . Your car has vacuum till you go into boost. A 3 bar is from -14.7 to 29.4 psi.. like you i have a 98 PCM. 2 bar is the highest i can go. I'm running 15 to 18 pounds of boost. but i can never hold my foot into it to ever see those numbers.
And wow is this thread full of bad info.
there are no -negatives. Believe it or not, that vacuum is merely just 'less' air than ambient. (its not 'space' vacuum)
25.00inHg is still 2.41psi!
Lets look at a 2Bar sensor (0-5V)
Will read 0 - ~205 kPa (you can look at this on your MAP table)
1 kPa is 0.145 PSI. There are no negatives! Even mars has a bit of PSI.
Depending where you are elevation wise.
Where I live, the ambient is approx 89kPa.
Mean Sea Level (MSL) is 101.3kPa.
Meaning ALL vehciles have a 1 bar sensor. usually will measure up to 105 kPa = 5V. from Zero. (0 PSI - 15.2 psi)
This covers even people living slightly lower than MSL.
a 2 bar sensor means, if one is at MSL, the MAP will measure an additional ~15 PSI. Again, look at your MAP table, you will notice 205 kPa. (4.90V)
whats 205 kPa 29.7 PSI. ( this is a 2 bar BARO (MAP) Sensor) approx 1 bar of boost (there is extra due to the headroom)
Last edited by vmapper; 08-31-2012 at 10:56 AM.
08-31-2012, 10:49 AM
#26
MAF - measures the Air MASS but not pressure. (will not see the boost)
No one mentions that running SD allows you to control BE (Boost enrichment) - which is a very handy feature, since the Baro sensor measures the actual pressure, you can control the enrichment rate based on the kpa. (rather than using rpm)
SD is based on several factors and calculated to determine fueling. rpm, throttle, cyl g/sec and IAT and of course the calibrated VE table or virtual.
This will always be 'snappier' quicker throttle vs MAF
hopefully I can explain this.
During a transient change. e.g. idle to full throttle.
the air BETWEEN the MAF and the cylinder has already been measured for calculating fueling, however, that measured air will be ingested quicker due to mechanics before velocity changes on the sensor. This is simply due to the placement and the fact of measuring actual air, rather than calculating it. This slight mis-measurement due to air velocity changing is a 'short delay'.
MAFs can be larger (e.g. Hitachi slot style) or larger tubing 4" + to slow the velocity giving a larger range.
For the elevation change questions.
If you tune the car and hit all variables when near sea level, elevation change will not matter, because the air is less dense where the vehicle can travel. (up to Denver)...and the tuner will have been able to calibrate those cells.
If you tune the car a mile high... you are not able to hit cells you would otherwise at sea level thus, at sea level, you would hit cells not calibrated... therefore 'interpolation' or trends must be used. (if your tuner is decent at all)
No one mentions that running SD allows you to control BE (Boost enrichment) - which is a very handy feature, since the Baro sensor measures the actual pressure, you can control the enrichment rate based on the kpa. (rather than using rpm)
SD is based on several factors and calculated to determine fueling. rpm, throttle, cyl g/sec and IAT and of course the calibrated VE table or virtual.
This will always be 'snappier' quicker throttle vs MAF
hopefully I can explain this.
During a transient change. e.g. idle to full throttle.
the air BETWEEN the MAF and the cylinder has already been measured for calculating fueling, however, that measured air will be ingested quicker due to mechanics before velocity changes on the sensor. This is simply due to the placement and the fact of measuring actual air, rather than calculating it. This slight mis-measurement due to air velocity changing is a 'short delay'.
MAFs can be larger (e.g. Hitachi slot style) or larger tubing 4" + to slow the velocity giving a larger range.
For the elevation change questions.
If you tune the car and hit all variables when near sea level, elevation change will not matter, because the air is less dense where the vehicle can travel. (up to Denver)...and the tuner will have been able to calibrate those cells.
If you tune the car a mile high... you are not able to hit cells you would otherwise at sea level thus, at sea level, you would hit cells not calibrated... therefore 'interpolation' or trends must be used. (if your tuner is decent at all)
08-31-2012, 10:55 AM
#27
Summary - either MAF or SD will work.
I prefer SD, with proper IAT (as its critical for the calculating)
** a Soaked IAT sensor will put SD out to lunch and you wont be happy, there are also faster responding IAT sensors available.
SD and weather change affecting the tune is an internet myth. -and/or exposing bad tuners.
If your bored and want details, you can read up on the workings of each from Marcin.
http://redhardsupra.blogspot.com.au/...omparison.html
I prefer SD, with proper IAT (as its critical for the calculating)
** a Soaked IAT sensor will put SD out to lunch and you wont be happy, there are also faster responding IAT sensors available.
SD and weather change affecting the tune is an internet myth. -and/or exposing bad tuners.
If your bored and want details, you can read up on the workings of each from Marcin.
http://redhardsupra.blogspot.com.au/...omparison.html
Last edited by vmapper; 08-31-2012 at 11:00 AM.
09-30-2012, 09:33 AM
#28
Summary - either MAF or SD will work.
I prefer SD, with proper IAT (as its critical for the calculating)
** a Soaked IAT sensor will put SD out to lunch and you wont be happy, there are also faster responding IAT sensors available.
SD and weather change affecting the tune is an internet myth. -and/or exposing bad tuners.
If your bored and want details, you can read up on the workings of each from Marcin.
http://redhardsupra.blogspot.com.au/...omparison.html
I prefer SD, with proper IAT (as its critical for the calculating)
** a Soaked IAT sensor will put SD out to lunch and you wont be happy, there are also faster responding IAT sensors available.
SD and weather change affecting the tune is an internet myth. -and/or exposing bad tuners.
If your bored and want details, you can read up on the workings of each from Marcin.
http://redhardsupra.blogspot.com.au/...omparison.html
Bringing this back up top for a question with regards to IAT sensors. Who makes a compatible faster responding IAT sensor or should I try a new one first and see if it responds better. My factory sensor is slow to respond. During a 3rd gear pull, my IAT's are only going up 5-7 degrees, granted, I have a FMIC, but I don't think it's that efficient. To back up that theory, I recently added a water/methanol injection setup, and when it kicks on, I'm only seeing a 4-6 degree decrease in temperature. So I think my IAT is extremely lazy.
09-30-2012, 02:01 PM
#29
i bought an expensive *** aftermarket MAF from Pro-M to and my tuner was willing to see if it was possible to run it on a boosted setup above 600rwhp. it was pegging out at like 3500 rpm. SD is the way to go apparently....even if MAF were available alot of people would prob still go SD.
And Yes id like a link to that IAT sensor as well. Sure mine might as well be changed.
And Yes id like a link to that IAT sensor as well. Sure mine might as well be changed.
09-30-2012, 03:47 PM
#30
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Id like to know as well,im using the typhoon sensor but it gets badly heatsoaked if I shut my car off then the fueling gets whacked out untill I drive for ten minutes to get cool air blowing thru the pipes. Any one know of a plastic version of the typhoon sensor?
Bringing this back up top for a question with regards to IAT sensors. Who makes a compatible faster responding IAT sensor or should I try a new one first and see if it responds better. My factory sensor is slow to respond. During a 3rd gear pull, my IAT's are only going up 5-7 degrees, granted, I have a FMIC, but I don't think it's that efficient. To back up that theory, I recently added a water/methanol injection setup, and when it kicks on, I'm only seeing a 4-6 degree decrease in temperature. So I think my IAT is extremely lazy.
