Advantages/disadvantages of SD?
05-25-2006, 02:44 PM
#62
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Here's my take on it...
The MAF is a device made with it's sole purpose to inject a VARIABLE into the fueling equation. I don't know about you guys but the ONLY way in my world to achieve the absolute most power any engine will make in a given environment is to eliminate all variables from the equation. Variables introduce margins for error and must be taken into account in the tune.... if you tune to the ragged edge then a variable is the difference between purr and boom. Hense you will NEVER see any of my vehicles running a MAF... I like to KNOW what my engine is doing and not trust that the magic is happening.
But if winning isn't your thing then hell .... I hear Foose makes some nice wheels lol.
The MAF is a device made with it's sole purpose to inject a VARIABLE into the fueling equation. I don't know about you guys but the ONLY way in my world to achieve the absolute most power any engine will make in a given environment is to eliminate all variables from the equation. Variables introduce margins for error and must be taken into account in the tune.... if you tune to the ragged edge then a variable is the difference between purr and boom. Hense you will NEVER see any of my vehicles running a MAF... I like to KNOW what my engine is doing and not trust that the magic is happening.
But if winning isn't your thing then hell .... I hear Foose makes some nice wheels lol.
05-25-2006, 02:57 PM
#63
Originally Posted by Homeslice (tm)
Here's my take on it...
The MAF is a device made with it's sole purpose to inject a VARIABLE into the fueling equation. I don't know about you guys but the ONLY way in my world to achieve the absolute most power any engine will make in a given environment is to eliminate all variables from the equation. Variables introduce margins for error and must be taken into account in the tune.... if you tune to the ragged edge then a variable is the difference between purr and boom. Hense you will NEVER see any of my vehicles running a MAF... I like to KNOW what my engine is doing and not trust that the magic is happening.
But if winning isn't your thing then hell .... I hear Foose makes some nice wheels lol.
The MAF is a device made with it's sole purpose to inject a VARIABLE into the fueling equation. I don't know about you guys but the ONLY way in my world to achieve the absolute most power any engine will make in a given environment is to eliminate all variables from the equation. Variables introduce margins for error and must be taken into account in the tune.... if you tune to the ragged edge then a variable is the difference between purr and boom. Hense you will NEVER see any of my vehicles running a MAF... I like to KNOW what my engine is doing and not trust that the magic is happening.
But if winning isn't your thing then hell .... I hear Foose makes some nice wheels lol.
05-25-2006, 03:00 PM
#64
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Originally Posted by Homeslice (tm)
Here's my take on it...
The MAF is a device made with it's sole purpose to inject a VARIABLE into the fueling equation. I don't know about you guys but the ONLY way in my world to achieve the absolute most power any engine will make in a given environment is to eliminate all variables from the equation. Variables introduce margins for error and must be taken into account in the tune.... if you tune to the ragged edge then a variable is the difference between purr and boom. Hense you will NEVER see any of my vehicles running a MAF... I like to KNOW what my engine is doing and not trust that the magic is happening.
But if winning isn't your thing then hell .... I hear Foose makes some nice wheels lol.
The MAF is a device made with it's sole purpose to inject a VARIABLE into the fueling equation. I don't know about you guys but the ONLY way in my world to achieve the absolute most power any engine will make in a given environment is to eliminate all variables from the equation. Variables introduce margins for error and must be taken into account in the tune.... if you tune to the ragged edge then a variable is the difference between purr and boom. Hense you will NEVER see any of my vehicles running a MAF... I like to KNOW what my engine is doing and not trust that the magic is happening.
But if winning isn't your thing then hell .... I hear Foose makes some nice wheels lol.
IAT, MAP, TPS, etc?
05-25-2006, 03:09 PM
#65
Originally Posted by white2001s10
Okay well that's tricky & unexpected being molded into the duct.
Looks like they made it impossible to modify the air ducting for things like FI without ditching the MAF in the process.
I do know that GM has rolled out many models that ran SD mode without a problem.
Looks like they made it impossible to modify the air ducting for things like FI without ditching the MAF in the process.
I do know that GM has rolled out many models that ran SD mode without a problem.
05-25-2006, 03:14 PM
#66
Originally Posted by GuitsBoy
In my opinion, this could not be further from the truth. The MAF is a very accurate meter, particularly at greater airflow. Its far more accurate than the speed density calculations. If you want to talk about having too many hands in the soup, think about the speed density calculations. A giant conglomerate of RPM, IAT, ETC, MAP, VE and probbably a half dozen other filters. How could a calculation of that magnatude be simpler and more accurate than directly measuring the airflow from the MAF. Assuming youre running a MAF big enough to keep from restricting the intake, and that its calibrated properly, the MAF is simpler and more accurate.
and dont forget about the scale of accuracy.
05-25-2006, 05:48 PM
#67
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with SD the largest contributing error term is the VE table, which has no ability to change with engine variation.
Many newer vehicles still run SD tuning, some even still run Alpha-N. Ever heard the phrase "lowest cost to achieve target performance goals and emissions compliance"?
If your target performance criteria is conservative or you just plain don't care about performance so long as the customer don't complain. The emissions drive cycle tests really aren't that hard to achieve given an average closed loop fuel controller and a reasonable mechanical engine design.
Also, if you went thru mechanical engineer school being told:
"here are the 3 best ways of measuring airflow... back in the dark ages we used TPS as a reference to engine load, and a basic lookup table told us how much air was entering the engine. Then some bright spark realized that the manifold pressure was a better reference to engine load than TPS and so that was combined with the Gas laws of physics. It works out that using MAP, IAT, RPM, a user controlled efficiency table and some quite complex calculations you can more accurately determine the airflow into the engine, this was called Speed Density based estimation. Then along came the MAF which directly measures the intake airflow much like your water meter measures your water usage at home, so there is no more guesswork or human factor and i'm told it's accurate enough for all practical applications. For your homework tonight show me the measurement error introduced by all three techniques..."
and all the engineers went to the local bar and drank a toast to their new buddy the MAF.
Many newer vehicles still run SD tuning, some even still run Alpha-N. Ever heard the phrase "lowest cost to achieve target performance goals and emissions compliance"?
If your target performance criteria is conservative or you just plain don't care about performance so long as the customer don't complain. The emissions drive cycle tests really aren't that hard to achieve given an average closed loop fuel controller and a reasonable mechanical engine design.
Also, if you went thru mechanical engineer school being told:
"here are the 3 best ways of measuring airflow... back in the dark ages we used TPS as a reference to engine load, and a basic lookup table told us how much air was entering the engine. Then some bright spark realized that the manifold pressure was a better reference to engine load than TPS and so that was combined with the Gas laws of physics. It works out that using MAP, IAT, RPM, a user controlled efficiency table and some quite complex calculations you can more accurately determine the airflow into the engine, this was called Speed Density based estimation. Then along came the MAF which directly measures the intake airflow much like your water meter measures your water usage at home, so there is no more guesswork or human factor and i'm told it's accurate enough for all practical applications. For your homework tonight show me the measurement error introduced by all three techniques..."
and all the engineers went to the local bar and drank a toast to their new buddy the MAF.
05-25-2006, 06:26 PM
#68
Originally Posted by gameover
with SD the largest contributing error term is the VE table, which has no ability to change with engine variation.
Many newer vehicles still run SD tuning, some even still run Alpha-N. Ever heard the phrase "lowest cost to achieve target performance goals and emissions compliance"?
If your target performance criteria is conservative or you just plain don't care about performance so long as the customer don't complain. The emissions drive cycle tests really aren't that hard to achieve given an average closed loop fuel controller and a reasonable mechanical engine design.
Also, if you went thru mechanical engineer school being told:
"here are the 3 best ways of measuring airflow... back in the dark ages we used TPS as a reference to engine load, and a basic lookup table told us how much air was entering the engine. Then some bright spark realized that the manifold pressure was a better reference to engine load than TPS and so that was combined with the Gas laws of physics. It works out that using MAP, IAT, RPM, a user controlled efficiency table and some quite complex calculations you can more accurately determine the airflow into the engine, this was called Speed Density based estimation. Then along came the MAF which directly measures the intake airflow much like your water meter measures your water usage at home, so there is no more guesswork or human factor and i'm told it's accurate enough for all practical applications. For your homework tonight show me the measurement error introduced by all three techniques..."
and all the engineers went to the local bar and drank a toast to their new buddy the MAF.
Many newer vehicles still run SD tuning, some even still run Alpha-N. Ever heard the phrase "lowest cost to achieve target performance goals and emissions compliance"?
If your target performance criteria is conservative or you just plain don't care about performance so long as the customer don't complain. The emissions drive cycle tests really aren't that hard to achieve given an average closed loop fuel controller and a reasonable mechanical engine design.
Also, if you went thru mechanical engineer school being told:
"here are the 3 best ways of measuring airflow... back in the dark ages we used TPS as a reference to engine load, and a basic lookup table told us how much air was entering the engine. Then some bright spark realized that the manifold pressure was a better reference to engine load than TPS and so that was combined with the Gas laws of physics. It works out that using MAP, IAT, RPM, a user controlled efficiency table and some quite complex calculations you can more accurately determine the airflow into the engine, this was called Speed Density based estimation. Then along came the MAF which directly measures the intake airflow much like your water meter measures your water usage at home, so there is no more guesswork or human factor and i'm told it's accurate enough for all practical applications. For your homework tonight show me the measurement error introduced by all three techniques..."
and all the engineers went to the local bar and drank a toast to their new buddy the MAF.
cool. they all have some measurement error....do you know of any tests done to see how accurate fueling has to be to effect power output?
05-25-2006, 06:39 PM
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I will just add some of the error for the MAF system.
The MAF table is still just a predicted air-flow model, except it's only 2D, where the VE table is 3D. Even completely stock applications can use some MAF table adjustment.
Being a direct measurement device for air-flow, the MAF output is time based.
By this I mean that more air passing the element in a given time will produce a higher output from the sensor.
IMO this makes the MAF output indirectly tied to RPM.
An engine at a given TPS will pass more air past the MAF at higher engine speeds.
Where I see the problem is that charge density for each combustion event is more directly tied to manifold pressure than it is to MAF output. Luckily the MAF table is just another airflow model that can be changed around until it works about the same as the MAP.... well except for transients.
During transients the MAP and MAF outputs aren't the same at all.
Adding a sensor with a sensitive heated wire is IMO just asking for problems and inconsistencies. The integrity of the heating circuitry has to remain flawless, and the wire itself must remain clean of contaminants like filter oil or the backwash vapor from reversion or backfires in the intake manifold.
The MAF output can become un-linear with significant reversion present at lower RPM.
MAF systems are also very sensitive to small vacuum leaks, and pose at least some limitations on how certain functions such as PCV are handled.
Opting to keep an expensive sensor that is prone to problems, adds heat energy to the incoming airflow while essentially adding another point of failure to the system, and possible inconsistencies to the tune would not be my first choice in most cases.
Some people enjoy the MAF plus the feed-back (closed loop) routine as an "easy" way for the system to self-adjust to some modifications.
Others see the MAF and feed-back routine as sources of unrelenting heartache and headaches. There are certain situations where keeping the MAF and getting it to function properly with a certain combination is not impossible, but is nowhere near worth the effort.
I don't think any of the SD fans ever came out and said for everyone to toss their MAFs and switch to SD. I think it was more of a case of letting people know of another option if they would choose to try it out, and maybe posting up of both good and bad results from the switch.
The discussions almost always bring out new and usefull information, which I think is a good thing.
The MAF table is still just a predicted air-flow model, except it's only 2D, where the VE table is 3D. Even completely stock applications can use some MAF table adjustment.
Being a direct measurement device for air-flow, the MAF output is time based.
By this I mean that more air passing the element in a given time will produce a higher output from the sensor.
IMO this makes the MAF output indirectly tied to RPM.
An engine at a given TPS will pass more air past the MAF at higher engine speeds.
Where I see the problem is that charge density for each combustion event is more directly tied to manifold pressure than it is to MAF output. Luckily the MAF table is just another airflow model that can be changed around until it works about the same as the MAP.... well except for transients.
During transients the MAP and MAF outputs aren't the same at all.
Adding a sensor with a sensitive heated wire is IMO just asking for problems and inconsistencies. The integrity of the heating circuitry has to remain flawless, and the wire itself must remain clean of contaminants like filter oil or the backwash vapor from reversion or backfires in the intake manifold.
The MAF output can become un-linear with significant reversion present at lower RPM.
MAF systems are also very sensitive to small vacuum leaks, and pose at least some limitations on how certain functions such as PCV are handled.
Opting to keep an expensive sensor that is prone to problems, adds heat energy to the incoming airflow while essentially adding another point of failure to the system, and possible inconsistencies to the tune would not be my first choice in most cases.
Some people enjoy the MAF plus the feed-back (closed loop) routine as an "easy" way for the system to self-adjust to some modifications.
Others see the MAF and feed-back routine as sources of unrelenting heartache and headaches. There are certain situations where keeping the MAF and getting it to function properly with a certain combination is not impossible, but is nowhere near worth the effort.
I don't think any of the SD fans ever came out and said for everyone to toss their MAFs and switch to SD. I think it was more of a case of letting people know of another option if they would choose to try it out, and maybe posting up of both good and bad results from the switch.
The discussions almost always bring out new and usefull information, which I think is a good thing.
05-25-2006, 06:49 PM
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I'm running mafless for ONE reason.
Every time I enable my maf, my car feels significantly slower. Especially at part throttle and below 4k rpms.
I spent a month trying to calibrate it. I even posted logs and my tune. No one else could seem to figure out what was up.
So, I just disabled it, car feels faster. I'm happy.
Every time I enable my maf, my car feels significantly slower. Especially at part throttle and below 4k rpms.
I spent a month trying to calibrate it. I even posted logs and my tune. No one else could seem to figure out what was up.
So, I just disabled it, car feels faster. I'm happy.
05-25-2006, 08:04 PM
#73
Originally Posted by txhorns281
thank you dammit 
I also "felt" like I didnt gain any power after the FAST intake and correct pushrods but gained 25 hp, at times I also thought my car was down on power by the SOTP feel to my friends car, yet I made a bit more power than him. Until someone can go on the dyno and actually prove this power loss I wont believe it....yet Larry already did and showed zero loss, so there you have it
lol
05-25-2006, 08:11 PM
#74
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Originally Posted by white2001s10
I will just add some of the error for the MAF system.
The MAF table is still just a predicted air-flow model, except it's only 2D, where the VE table is 3D. Even completely stock applications can use some MAF table adjustment.
Being a direct measurement device for air-flow, the MAF output is time based.
By this I mean that more air passing the element in a given time will produce a higher output from the sensor.
IMO this makes the MAF output indirectly tied to RPM.
An engine at a given TPS will pass more air past the MAF at higher engine speeds.
Where I see the problem is that charge density for each combustion event is more directly tied to manifold pressure than it is to MAF output. Luckily the MAF table is just another airflow model that can be changed around until it works about the same as the MAP.... well except for transients.
During transients the MAP and MAF outputs aren't the same at all.
Adding a sensor with a sensitive heated wire is IMO just asking for problems and inconsistencies. The integrity of the heating circuitry has to remain flawless, and the wire itself must remain clean of contaminants like filter oil or the backwash vapor from reversion or backfires in the intake manifold.
The MAF output can become un-linear with significant reversion present at lower RPM.
MAF systems are also very sensitive to small vacuum leaks, and pose at least some limitations on how certain functions such as PCV are handled.
Opting to keep an expensive sensor that is prone to problems, adds heat energy to the incoming airflow while essentially adding another point of failure to the system, and possible inconsistencies to the tune would not be my first choice in most cases.
Some people enjoy the MAF plus the feed-back (closed loop) routine as an "easy" way for the system to self-adjust to some modifications.
Others see the MAF and feed-back routine as sources of unrelenting heartache and headaches. There are certain situations where keeping the MAF and getting it to function properly with a certain combination is not impossible, but is nowhere near worth the effort.
I don't think any of the SD fans ever came out and said for everyone to toss their MAFs and switch to SD. I think it was more of a case of letting people know of another option if they would choose to try it out, and maybe posting up of both good and bad results from the switch.
The discussions almost always bring out new and usefull information, which I think is a good thing.
The MAF table is still just a predicted air-flow model, except it's only 2D, where the VE table is 3D. Even completely stock applications can use some MAF table adjustment.
Being a direct measurement device for air-flow, the MAF output is time based.
By this I mean that more air passing the element in a given time will produce a higher output from the sensor.
IMO this makes the MAF output indirectly tied to RPM.
An engine at a given TPS will pass more air past the MAF at higher engine speeds.
Where I see the problem is that charge density for each combustion event is more directly tied to manifold pressure than it is to MAF output. Luckily the MAF table is just another airflow model that can be changed around until it works about the same as the MAP.... well except for transients.
During transients the MAP and MAF outputs aren't the same at all.
Adding a sensor with a sensitive heated wire is IMO just asking for problems and inconsistencies. The integrity of the heating circuitry has to remain flawless, and the wire itself must remain clean of contaminants like filter oil or the backwash vapor from reversion or backfires in the intake manifold.
The MAF output can become un-linear with significant reversion present at lower RPM.
MAF systems are also very sensitive to small vacuum leaks, and pose at least some limitations on how certain functions such as PCV are handled.
Opting to keep an expensive sensor that is prone to problems, adds heat energy to the incoming airflow while essentially adding another point of failure to the system, and possible inconsistencies to the tune would not be my first choice in most cases.
Some people enjoy the MAF plus the feed-back (closed loop) routine as an "easy" way for the system to self-adjust to some modifications.
Others see the MAF and feed-back routine as sources of unrelenting heartache and headaches. There are certain situations where keeping the MAF and getting it to function properly with a certain combination is not impossible, but is nowhere near worth the effort.
I don't think any of the SD fans ever came out and said for everyone to toss their MAFs and switch to SD. I think it was more of a case of letting people know of another option if they would choose to try it out, and maybe posting up of both good and bad results from the switch.
The discussions almost always bring out new and usefull information, which I think is a good thing.
I like the different viewpoints in this thread, the only thing I do not like is how some things said here are assumptive that everyone should agree to that logic. A MAF and closed loop is perfect for someone wanting to set everything up once and never look back, OLSD might be how a track enthusiast feels that their optimal performance for that type of driving is reached. Not everyone has a lead foot, not everyone is a cruisin grandpa, and most importantly, MOST everyone are not knowledgable enough to understand or distinguish these very very minor differences. What we know by theory doesn't always show in reality, and the reality is that if we have two well tuned modes of fuel injection discussed here, the variance b/w the two is marginal enough that without any highly developed understanding on how these systems were meant to work, the words "right" and "wrong" have no value. Which again, encompasses most people.
For instance, we always hear people saying how this feels faster or making claims that one or the other is "faster." Bring something concrete to the table and maybe you'll have a point. But we can't just say that SD will run faster at the track without holding EVERYTHING else as a constant (launch, traction, shifting, air quality, headwind, backwind, even straight steering) Now if we ran 10 passes on a MAF setup, and 10 passes SD, and the SD was clearly faster 75% of the time (assuming driving and conditions are as consistant is possible), then that holds merit. Or if when you took your MAF off (or put it on) and some band of rpms "feels" stronger or weaker, (assuming that both systems were well tuned to a marginal point of error swing), and some sort of log data consistantly showing acceleration increases or decreases over certain time lapses, then that would also hold merit. I suppose the merit in my statements, I've derived from test after test after test. On the street, on the dyno, on the track, from a performance standpoint, a tuning standpoint, and a racing standpoint, all have been closely matched enough to say that there is virtually no intelligible difference b/w these operating modes. Hopping back and forth b/w MAF and SD for almost 2 years shows you a lot of things about how THESE engines work off the EFI system.
I really hope that when people read this thread that they will be encouraged to attempt SD and find their own truths in their personal tolerances and likings. But don't go into it thinking you're doing something better just b/c it's SD. And it is in fact that SD "fans" are coming out of the woodwork and telling everyone to ditch their MAF (the bandwagon SD fans, not the people who purposefully choose SD as an operating mode) b/c they think SD unlocks a superior mark of performance at every level. As we've said before, this statement is not right for everyone, is not even right for most, b/c most are not at a level of knowledgability as to why SD or MAF might be better for them. WOOF! My fingers hurt..... back to
05-26-2006, 12:15 AM
#75
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my car felt fast with a tune and some pipes... then it started feeling slow... then it felt fast again with a new cam and ported heads and another tune.... and then it felt slow again.... then it felt fast again with a s/c bolted on.... and yeah it feels slow again now.... whats wrong with my car?
great post above btw
great post above btw
05-26-2006, 12:17 AM
#76
Originally Posted by gameover
my car felt fast with a tune and some pipes... then it started feeling slow... then it felt fast again with a new cam and ported heads and another tune.... and then it felt slow again.... then it felt fast again with a s/c bolted on.... and yeah it feels slow again now.... whats wrong with my car?
great post above btw
great post above btw
Nothing, you got used to it. 
Thats too funny.
05-26-2006, 01:38 AM
#77
Originally Posted by gameover
my car felt fast with a tune and some pipes... then it started feeling slow... then it felt fast again with a new cam and ported heads and another tune.... and then it felt slow again.... then it felt fast again with a s/c bolted on.... and yeah it feels slow again now.... whats wrong with my car?
great post above btw
great post above btw
I'm in the same boat. My car is constantly getting faster but yet feels slower and slower
05-26-2006, 08:56 AM
#79
lol. i could imagine pulling up to the local ford meet at a sonic drivein here.. they're all drooling over fords latest eaton M112 blown motor.. just glance at them and say "cute, but if you try to put that tiny blower on a real motor, you need two..."
05-26-2006, 10:31 AM
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Originally Posted by gameover
my car felt fast with a tune and some pipes... then it started feeling slow... then it felt fast again with a new cam and ported heads and another tune.... and then it felt slow again.... then it felt fast again with a s/c bolted on.... and yeah it feels slow again now.... whats wrong with my car?
great post above btw
great post above btw
Say what you will, but when you have the ability to go back and forth between having the MAF enabled and disabled back to back.
And you notice a significant difference in throttle response and low end torque each time........
Would it make everyone feel better if I log the exact time it takes in 3rd gear to go from 2000 rpm to 5000 rpm without the MAF, then do it WITH the maf??
