MAF sensor or not for FI
Thread Starter
Instructor
Joined: Nov 2007
Posts: 105
Likes: 0
From: Davisburg Michigan
MAF sensor or not for FI
Hello,
I am getting in over my head on this one ,but here goes.
I am finishing up my 94 with a new 383 and a "T" trim super charger Edlebrock " E : series manifold with # 60 injectors and a custom elbow to a 1000 CFM throttle body. I have both an intercooler mounted in the front as well as Alcohol injection.
My question, Should I plumb the MAF sensor back in or tune in speed density??
I am sure that I will have lots of questions in the future so thank for you help in advance.
I am getting in over my head on this one ,but here goes.
I am finishing up my 94 with a new 383 and a "T" trim super charger Edlebrock " E : series manifold with # 60 injectors and a custom elbow to a 1000 CFM throttle body. I have both an intercooler mounted in the front as well as Alcohol injection.
My question, Should I plumb the MAF sensor back in or tune in speed density??
I am sure that I will have lots of questions in the future so thank for you help in advance.
Melting Slicks
Joined: Jun 1999
Posts: 2,949
Likes: 23
From: Bowling Green KY
Hello,
I am getting in over my head on this one ,but here goes.
I am finishing up my 94 with a new 383 and a "T" trim super charger Edlebrock " E : series manifold with # 60 injectors and a custom elbow to a 1000 CFM throttle body. I have both an intercooler mounted in the front as well as Alcohol injection.
My question, Should I plumb the MAF sensor back in or tune in speed density??
I am sure that I will have lots of questions in the future so thank for you help in advance.
I am getting in over my head on this one ,but here goes.
I am finishing up my 94 with a new 383 and a "T" trim super charger Edlebrock " E : series manifold with # 60 injectors and a custom elbow to a 1000 CFM throttle body. I have both an intercooler mounted in the front as well as Alcohol injection.
My question, Should I plumb the MAF sensor back in or tune in speed density??
I am sure that I will have lots of questions in the future so thank for you help in advance.
Though others with far more experience with this than me will probably chime in, I "think" the LT1 MAF pegs at around 500 hp or so. I KNOW my buddy's C5 was pegging his MAF at around that so I suspect the LT1 would be similar.
Thread Starter
Instructor
Joined: Nov 2007
Posts: 105
Likes: 0
From: Davisburg Michigan
Thanks Rukwkr, looks like you have a great build going on yourself.
I also have included in my blowerworks kit is an electronic devise that modulates the frequecy of the maf to 10.6 k so that the maf cannot be maxed out.
I am just not sure which method will be best and why?
who knows by the time we work through this one it could become a sticky.
I also have included in my blowerworks kit is an electronic devise that modulates the frequecy of the maf to 10.6 k so that the maf cannot be maxed out.
I am just not sure which method will be best and why?
who knows by the time we work through this one it could become a sticky.
Melting Slicks
Joined: Jun 1999
Posts: 2,949
Likes: 23
From: Bowling Green KY
Thanks Rukwkr, looks like you have a great build going on yourself.
I also have included in my blowerworks kit is an electronic devise that modulates the frequecy of the maf to 10.6 k so that the maf cannot be maxed out.
I am just not sure which method will be best and why?
who knows by the time we work through this one it could become a sticky.
I also have included in my blowerworks kit is an electronic devise that modulates the frequecy of the maf to 10.6 k so that the maf cannot be maxed out.
I am just not sure which method will be best and why?
who knows by the time we work through this one it could become a sticky.
Hmmm I'm not sure either honestly. I have seen several posts about tweaking the MAF like that but I gotta believe that's not the best way. I also have to believe that once you start reaching the higher power levels the MAF actually causes a restriction in flow as well though I don't know this for sure.
I want to do a twin turbo next year and I'll get rid of the MAF altogether.
Le Mans Master
Joined: Aug 2000
Posts: 8,838
Likes: 31
From: Australia
Longtime ongoing argument
Fact: MAF is easier to tune than MAP.
The restriction debate is unresolved.
Many claim the MAF sensor is a air flow restriction while others (Ski ?) have made good Hp with the MAF in place.
Interesting tech read on MAF fueling
http://www.thirdgen.org/techboard/di...-5000-wot.html
Fact: MAF is easier to tune than MAP.
The restriction debate is unresolved.
Many claim the MAF sensor is a air flow restriction while others (Ski ?) have made good Hp with the MAF in place.
Interesting tech read on MAF fueling
http://www.thirdgen.org/techboard/di...-5000-wot.html
Melting Slicks
Joined: Jun 1999
Posts: 2,949
Likes: 23
From: Bowling Green KY
No doubt. But very few big power forced induction cars run a MAF, but probably more to do with the ability to run piping however you want, cleanliness, etc.
Ski's car is N/A so no doubt you can make GOOD power with MAF but I haven't seen many folks making HUGE power with MAF???????
Thread Starter
Instructor
Joined: Nov 2007
Posts: 105
Likes: 0
From: Davisburg Michigan
Rodj,
Thanks for the link, that was some good reads.
Looks like the vote is unanimous, I will leave the maf out.
If anyone comes upwith a good reason why we need it, I can always fab it back in later.
Ron
Thanks for the link, that was some good reads.
Looks like the vote is unanimous, I will leave the maf out.
If anyone comes upwith a good reason why we need it, I can always fab it back in later.
Ron
Melting Slicks
Joined: Jun 1999
Posts: 2,949
Likes: 23
From: Bowling Green KY
It's actually pretty amazing the changes you can make to a MAF car and the thing still run fine (not necessarily perfect, but decent).
You may know this already but a MAF system MEASURES airflow whereas MAP is really just CALCULATING airflow, and therein lies the answer I think as to why MAF is better for adjusting to radical changes in volumetric efficiency.
BUT, with the RIGHT MAP tune, the car will run the same. I think with MAF you can get away with your volumetric efficiency tables being off, with MAP you can't so you have to get em' much closer.
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Burning Brakes
Joined: Aug 2006
Posts: 1,061
Likes: 99
From: Seattle WA
Keep in mind that the work on thirdgen is talking about TPI-based MAF systems, which are much more limited than LTx systems (I don't know the details on the LTx system, though).
I would not be concerned with the flow restriction of the LTx MAF (700+ CFM n/a), esp in a FI application.
I'll be watching this thread closely as well as the one on thirdgen as I try to decide between a speed density conversion or further developing the MAF system to extend its limits.
I would not be concerned with the flow restriction of the LTx MAF (700+ CFM n/a), esp in a FI application.
I'll be watching this thread closely as well as the one on thirdgen as I try to decide between a speed density conversion or further developing the MAF system to extend its limits.
Instructor
Joined: Aug 2007
Posts: 230
Likes: 1
From: Covington GA
There's another reason: It is hard to find a MAF capable of measuring enough air for one of these engines, and if you do find one, they often don't read very well at low flow rates for idle and cruising. With speed density, you can just pick a MAP sensor that reads more than the most boost you'll feed the engine and be done with it.
Le Mans Master
Joined: Aug 2000
Posts: 8,838
Likes: 31
From: Australia
Oldie but goodie once you get past the bruised egos.
MAF v SD
http://www.thirdgen.org/techboard/po...without-2.html
MAF v SD
http://www.thirdgen.org/techboard/po...without-2.html
Melting Slicks
Joined: Jun 1999
Posts: 2,949
Likes: 23
From: Bowling Green KY
Oldie but goodie once you get past the bruised egos.
MAF v SD
http://www.thirdgen.org/techboard/po...without-2.html
MAF v SD
http://www.thirdgen.org/techboard/po...without-2.html
LOL, yeah those guys are going at it in that post.
I found it especially interesting (if the info was correct) that every single aftermarket tuning system was MAP.
The consensus seems to be if you want to make stupid power to go with MAP, even if it is somewhat harder to tune.
Melting Slicks
Joined: Jun 1999
Posts: 2,949
Likes: 23
From: Bowling Green KY
Keep in mind that the work on thirdgen is talking about TPI-based MAF systems, which are much more limited than LTx systems (I don't know the details on the LTx system, though).
I would not be concerned with the flow restriction of the LTx MAF (700+ CFM n/a), esp in a FI application.
I'll be watching this thread closely as well as the one on thirdgen as I try to decide between a speed density conversion or further developing the MAF system to extend its limits.
I would not be concerned with the flow restriction of the LTx MAF (700+ CFM n/a), esp in a FI application.
I'll be watching this thread closely as well as the one on thirdgen as I try to decide between a speed density conversion or further developing the MAF system to extend its limits.
So in other words, whether he was making 500 hp or 600 hp the MAF TELLS you that it sees the same airflow at both levels. That is the problem for most folks I think. And this is on a C5, so I can only think the LTX is the same (or worse).
Even GM couldn't seem to make up it's mind on this issue since they were MAF at first, then they went to MAP for a short while, then back to MAF. I suspect they use MAF from the factory because there is no doubt that it is much easier to tune and responds better to a variety of driving scenarios.
Anyone know if the new ZR1 is MAF or MAP? It will be the first factory car well past this 500 hp limit that keeps popping up so I'm curious. My money says its MAP.
Burning Brakes
Joined: Aug 2006
Posts: 1,061
Likes: 99
From: Seattle WA
It's not FLOW restriction we are concerned about, I also doubt it is much of a restriction until you go with BIG power, the question is at what point can it not keep up with airflow. On my buddy's C5 the MAF pegged once he went past 500 hp, it wasn't restricting airflow, it just couldn't measure anymore air past that.
So in other words, whether he was making 500 hp or 600 hp the MAF TELLS you that it sees the same airflow at both levels. That is the problem for most folks I think. And this is on a C5, so I can only think the LTX is the same (or worse).
Even GM couldn't seem to make up it's mind on this issue since they were MAF at first, then they went to MAP for a short while, then back to MAF. I suspect they use MAF from the factory because there is no doubt that it is much easier to tune and responds better to a variety of driving scenarios.
Anyone know if the new ZR1 is MAF or MAP? It will be the first factory car well past this 500 hp limit that keeps popping up so I'm curious. My money says its MAP.
So in other words, whether he was making 500 hp or 600 hp the MAF TELLS you that it sees the same airflow at both levels. That is the problem for most folks I think. And this is on a C5, so I can only think the LTX is the same (or worse).
Even GM couldn't seem to make up it's mind on this issue since they were MAF at first, then they went to MAP for a short while, then back to MAF. I suspect they use MAF from the factory because there is no doubt that it is much easier to tune and responds better to a variety of driving scenarios.
Anyone know if the new ZR1 is MAF or MAP? It will be the first factory car well past this 500 hp limit that keeps popping up so I'm curious. My money says its MAP.
My guess is that the new ZR1 will have both, as that seems to be the direction lately, probably for emissions reasons. Technically, MAF is a little more accurate while it's within its range because it also takes into account humidity in the air (I haven't seen a SD system do that yet) while having SD logic in there, too, is inexpensive and can make up for MAF's shortcomings under certain conditions.
Le Mans Master
Joined: Aug 2000
Posts: 8,838
Likes: 31
From: Australia
Regarding MAF pegging, there are two things that can cause it to "peg", at least in the L98-type system.
1) The calibration/operating range of the sensor itself and 2) The range that the computer can understand (not a problem in LTx?). There are ways to get around both causes of MAF pegging if you want to go that route.
.
1) The calibration/operating range of the sensor itself and 2) The range that the computer can understand (not a problem in LTx?). There are ways to get around both causes of MAF pegging if you want to go that route.
.
It is not just a "physical" restriction in the airflow
( until you need massive airflow )
The MAF can "read" higher than 255 gps but its in the 8-bit ECM where the 255 limit is reached due to the fact that 255 is the highest number possible in binary code for an 8-bit (165 ECM ).
Hence the reason why LT1 owners never complain of MAF troubles....they have 16 bit computers
I wonder what 65535 gms/sec equates to in HP?!?
Melting Slicks
Joined: Jun 1999
Posts: 2,949
Likes: 23
From: Bowling Green KY
Exactly
It is not just a "physical" restriction in the airflow
( until you need massive airflow )
The MAF can "read" higher than 255 gps but its in the 8-bit ECM where the 255 limit is reached due to the fact that 255 is the highest number possible in binary code for an 8-bit (165 ECM ).
Hence the reason why LT1 owners never complain of MAF troubles....they have 16 bit computers
It is not just a "physical" restriction in the airflow
( until you need massive airflow )
The MAF can "read" higher than 255 gps but its in the 8-bit ECM where the 255 limit is reached due to the fact that 255 is the highest number possible in binary code for an 8-bit (165 ECM ).
Hence the reason why LT1 owners never complain of MAF troubles....they have 16 bit computers
I'm not at that kind of power level yet anyway but again I'll mention my buddy's C5 pegged his MAF at about 500 hp and obviously a C5 has a 16 bit (or more?) computer so I don't think the 8 bit vs 16 bit thing gives us the whole story?
Burning Brakes
Joined: Aug 2006
Posts: 1,061
Likes: 99
From: Seattle WA
But I have heard of LT1 guys complaining about it?
I'm not at that kind of power level yet anyway but again I'll mention my buddy's C5 pegged his MAF at about 500 hp and obviously a C5 has a 16 bit (or more?) computer so I don't think the 8 bit vs 16 bit thing gives us the whole story?
I'm not at that kind of power level yet anyway but again I'll mention my buddy's C5 pegged his MAF at about 500 hp and obviously a C5 has a 16 bit (or more?) computer so I don't think the 8 bit vs 16 bit thing gives us the whole story?
Melting Slicks
Joined: Jun 1999
Posts: 2,949
Likes: 23
From: Bowling Green KY
It's probably just the range the sensor was designed to operate in. You can make a sensor with a wider range, but then it's not as accurate or responsive in the range they're trying to optimize (the EPA driving cycle). You can also change out the sensor to something with a wider range. There should be a MAF scaling table in the ECM where you can input the calibration of the new sensor.
His car was definitely pegging his MAF but as you state it's the sensor itself that is the limiting factor, not the PCM.
He also verified the C5 PCM is 32 bit so obviously it isn't the problem.
He also mentioned that Diablo makes a MAF that will allow you to extend the range of the sensor, not sure if they have one for LT1 or not.
I guess I'll find out the real answer to all of this one day when I actually make enough power to worry about it!