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Discussion Starter · #21 ·
There should be a value file for the BA5000 that will scale everything as needed. I used that when I ran that MAF in my 01 Cobra. You'll still have to work on the curve after that. You might need to tweak the load values in the spark tables.
Yes I did use the BA5000 value file so I guess the scaling is done for me.

I’ve been reading in Lasotas book about spark and I must say I am confused at the moment and a bit intimidated. I don’t have a dyno so I will be street tuning. How do I know when I’ve-realized the optimal spark? I’m assuming on a dyno you’d keep adjusting until the power stops improving and then turn it back a couple degrees for safety.

Also what exactly is load? Is it different from spark? Timing? Is it just a calculation of air flow, fuel and spark?
 

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Yes I did use the BA5000 value file so I guess the scaling is done for me.

I’ve been reading in Lasotas book about spark and I must say I am confused at the moment and a bit intimidated. I don’t have a dyno so I will be street tuning. How do I know when I’ve-realized the optimal spark? I’m assuming on a dyno you’d keep adjusting until the power stops improving and then turn it back a couple degrees for safety.

Also what exactly is load? Is it different from spark? Timing? Is it just a calculation of air flow, fuel and spark?
I've only street tuned my cars. But I generally tune on the conservative side anyway. I believe it was Lasota that came up with the rule of thumb that says you want 17 degrees of timing and 17psi max on pump gas. If you add one you subtract the other. IE if you go to 20psi you drop timing to 14 degrees. I'm currently at 18psi with 15 degrees on pump gas and I'm not getting knock. Plus I don't think you'll see max power before hitting detonation on pump gas.

Load is calculated by air flow, engine displacement, and something else that I can't remember. There's also a formula for the timing, but I don't remember it. I know, I'm a lot of help. But that's mostly at idle and part throttle. The timing table might have 30 degrees in that cell, but the ECU might figure 33 degrees is better. I've found at WOT it will stick with commanded timing unless the IAT's are high. Then it'll pull timing.
 

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Just getting started with SCT PRP. I'm currently dialing in the Transfer function. Simple question for now! When changing the transfer function do I change AD Counts and #/min together or just #/min? I've been highlighting both columns and changing them together but now I'm thinking that might be wrong.

Thanks for any help

Shawn

SCT does not necessarily do things the right way or the way the rest of the industry does, Shawn. For example tweaking your MAF transfer curve to get the engine fueling correct.

In the early days SCT (and most other MAF suppliers) would have their MAF's flowed by a firm up in New England that is called Pro-M Racing today. Pro-M had a similar, possibly the same name back then, I don't recall anymore. For reasons I am not privy to SCT no longer has them done by Pro-M and perhaps does not have them done at all relying on manufacturing consistency to duplicate flow characteristics MAF build to MAF build. Not a good model.

A MAF makes an absolute measurement of the mass of air being consumed by the engine at all times. If it is calibrated and flowed correctly it provides you with the Air component of your Air Fuel Ratio (AFR). If you, in this case the ECU, know how much air the engine is injesting, it is a simple four function math calculation to get the fuel required and the injector pulse width necessary to provide that fuel volume. This assumes your injectors are of a known flow rate and have been flow matched to confirm that flow rate.

When you fiddle with the MAF transfer curve you lie to the ECU about the amount of air being injested to get it to change the amount of fuel it is commanding be injected. The correct way to manipulate the fuel delivery for the engine at any particular engine rpm is to change the commanded AFR in the fueling table(s) at that point in the engine rpm range. Manipulating the MAF xfer function throws the engine load calculations off because you are misrepresenting actual air mass being consumed.

The correct way to fix the problem is get the MAF flowed and calibrated with a measured mass air flow table (MAF xfer curve) for the MAF that you intend to use and input that MAF xfer curve into the ECU MAF xfer function table. Pro-M will provide flow data for your MAF if you have them flow it. They will do this for some but not all MAFs. You ought to pull them up on the web, contact them and listen to what they have to say.

Th other thing you might want to do before calling them is watch these two short YouTube videos on MAF Technology and MAF signal quality. Click here => MAF Tech Review The video is 9 minutes long and gives an excellent explanation of the different MAF styles. This next video (5 mins) shows you what Chris (the narrator in the first video and President of the company) was talking about when he was referring to signal quality in the Pro-M 80, 92. and 117mm MAFs. Click here => MAF Voltage Signals

When you are done watching the MAF Voltage Signals video you will know which MAF you should be using.


Ed
 

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Discussion Starter · #24 ·
I've only street tuned my cars. But I generally tune on the conservative side anyway. I believe it was Lasota that came up with the rule of thumb that says you want 17 degrees of timing and 17psi max on pump gas. If you add one you subtract the other. IE if you go to 20psi you drop timing to 14 degrees. I'm currently at 18psi with 15 degrees on pump gas and I'm not getting knock. Plus I don't think you'll see max power before hitting detonation on pump gas.

Load is calculated by air flow, engine displacement, and something else that I can't remember. There's also a formula for the timing, but I don't remember it. I know, I'm a lot of help. But that's mostly at idle and part throttle. The timing table might have 30 degrees in that cell, but the ECU might figure 33 degrees is better. I've found at WOT it will stick with commanded timing unless the IAT's are high. Then it'll pull timing.

Good to know about Lasotas rule of thumb. I don't recall seeing that in his book but I haven't gotten all the way through it yet either. I'm reading and adjusting as I go through the book. Even re-reading at some points if I just don't understand

Thanks
 

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Discussion Starter · #25 ·
SCT does not necessarily do things the right way or the way the rest of the industry does, Shawn. For example tweaking your MAF transfer curve to get the engine fueling correct.

In the early days SCT (and most other MAF suppliers) would have their MAF's flowed by a firm up in New England that is called Pro-M Racing today. Pro-M had a similar, possibly the same name back then, I don't recall anymore. For reasons I am not privy to SCT no longer has them done by Pro-M and perhaps does not have them done at all relying on manufacturing consistency to duplicate flow characteristics MAF build to MAF build. Not a good model.

A MAF makes an absolute measurement of the mass of air being consumed by the engine at all times. If it is calibrated and flowed correctly it provides you with the Air component of your Air Fuel Ratio (AFR). If you, in this case the ECU, know how much air the engine is injesting, it is a simple four function math calculation to get the fuel required and the injector pulse width necessary to provide that fuel volume. This assumes your injectors are of a known flow rate and have been flow matched to confirm that flow rate.

When you fiddle with the MAF transfer curve you lie to the ECU about the amount of air being injested to get it to change the amount of fuel it is commanding be injected. The correct way to manipulate the fuel delivery for the engine at any particular engine rpm is to change the commanded AFR in the fueling table(s) at that point in the engine rpm range. Manipulating the MAF xfer function throws the engine load calculations off because you are misrepresenting actual air mass being consumed.

The correct way to fix the problem is get the MAF flowed and calibrated with a measured mass air flow table (MAF xfer curve) for the MAF that you intend to use and input that MAF xfer curve to the ECU MAF xfer function table. Pro-M will provide flow data for your MAF if you have them flow it. They will do this for some but not all MAFs. You ought to pull them up on the web, contact them and listen to what they have to say.

Th other thing you might want to do before calling them is watch these two short YouTube videos on MAF Technology and MAF signal quality. Click here => MAF Tech Review The video is 9 minutes long and gives an excellent explanation of the different MAF styles. This next video (5 mins) shows you what Chris (the narrator in the first video and President of the company) was talking about when he was referring to signal quality in the Pro-M 80, 92. and 117mm MAFs. Click here => MAF Voltage Signals

When you are done watching the MAF Voltage Signals video you will know which MAF you should be using.


Ed
Well thanks again Ed,

Is the x-transfer function data in the Tuning workbook pro reliable?

I've also read elsewhere about adjusting the fueling table instead of the MAF transfer function. Seems like most people fiddle with the MAF transfer function to get the fuel dialed in but adjusting the fuel table makes more sense to me.

So, does the MAF transfer function need to be spot on before fiddling with the fueling table? I've got a VMP MAF but have used the BA5000 MAF data from the workbook. Does your recommendation to have it flowed still stand even though I'm using the workbook data?

Thanks,
Shawn
 

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Discussion Starter · #26 ·
SCT does not necessarily do things the right way or the way the rest of the industry does, Shawn. For example tweaking your MAF transfer curve to get the engine fueling correct.

In the early days SCT (and most other MAF suppliers) would have their MAF's flowed by a firm up in New England that is called Pro-M Racing today. Pro-M had a similar, possibly the same name back then, I don't recall anymore. For reasons I am not privy to SCT no longer has them done by Pro-M and perhaps does not have them done at all relying on manufacturing consistency to duplicate flow characteristics MAF build to MAF build. Not a good model.

A MAF makes an absolute measurement of the mass of air being consumed by the engine at all times. If it is calibrated and flowed correctly it provides you with the Air component of your Air Fuel Ratio (AFR). If you, in this case the ECU, know how much air the engine is injesting, it is a simple four function math calculation to get the fuel required and the injector pulse width necessary to provide that fuel volume. This assumes your injectors are of a known flow rate and have been flow matched to confirm that flow rate.

When you fiddle with the MAF transfer curve you lie to the ECU about the amount of air being injested to get it to change the amount of fuel it is commanding be injected. The correct way to manipulate the fuel delivery for the engine at any particular engine rpm is to change the commanded AFR in the fueling table(s) at that point in the engine rpm range. Manipulating the MAF xfer function throws the engine load calculations off because you are misrepresenting actual air mass being consumed.

The correct way to fix the problem is get the MAF flowed and calibrated with a measured mass air flow table (MAF xfer curve) for the MAF that you intend to use and input that MAF xfer curve to the ECU MAF xfer function table. Pro-M will provide flow data for your MAF if you have them flow it. They will do this for some but not all MAFs. You ought to pull them up on the web, contact them and listen to what they have to say.

Th other thing you might want to do before calling them is watch these two short YouTube videos on MAF Technology and MAF signal quality. Click here => MAF Tech Review The video is 9 minutes long and gives an excellent explanation of the different MAF styles. This next video (5 mins) shows you what Chris (the narrator in the first video and President of the company) was talking about when he was referring to signal quality in the Pro-M 80, 92. and 117mm MAFs. Click here => MAF Voltage Signals

When you are done watching the MAF Voltage Signals video you will know which MAF you should be using.


Ed

Well I just finished watching those videos and man I wish I would have watched those when I was picking a MAF.

I originally had a BA2600 and then swapped that out for a VMP5000 slot style. What I did notice in the video is that they were testing the sensors in a draw through configuration. I am turbo so I would be a blow through configuration. That was the original reason that I had changed sensors. Don Lasota was very adamant that the slot style was the best configuration for my setup

So, although the videos were very informative, I'm still a bit confused. How different is a blow through vs draw through when it comes to signal quality? From what I've read, on this site and the web in general is that the slot style is the better choice for blow though. Chris in the pro-m video says that the slot style is not the best setup and should only be used in 05 and up cars. If running an 04 and older car then stick with a tonsil style MAF.

Thoughts?
 

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Well thanks again Ed,

Is the x-transfer function data in the Tuning workbook pro reliable?

I've also read elsewhere about adjusting the fueling table instead of the MAF transfer function. Seems like most people fiddle with the MAF transfer function to get the fuel dialed in but adjusting the fuel table makes more sense to me.

So, does the MAF transfer function need to be spot on before fiddling with the fueling table? I've got a VMP MAF but have used the BA5000 MAF data from the workbook. Does your recommendation to have it flowed still stand even though I'm using the workbook data?

Thanks,
Shawn

The Tuning Workbook MAF xfer function tables were correct for a particular MAF that was flowed (interestingly by Pro-M) years ago. MAFs manufactured today are similar but unless they have been calibrated they will be different than the data in the Workbook. This is one reason the SCT crowd got everyone pointed in the direction of fiddling with the MAF xfer function. If it was already wrong and fiddling could get a particular aspect of the problem, at a particular point in the engine operating rpm range closer why not fiddle, after all it's already wrong — we just don't know by how much.?

This is the absolute wrong way to tune the car. The approach is similar to putting injectors in the car that you don't know the flow characteristics of and then adjusting the AFR to get an injector pulse width that doesn't make the engine run too rich or too lean according to the O2 sensor(s). Will it work? Sure! Will it run as good as doing it the right way? Absolutely not! Will it create drivability problems that increase in severity the farther from the real settings required for the MAF and injectors you go — you bet.

There is always a way to fit a square peg in a round hole. The right way to assemble stuff is properly sized round pegs in round holes and properly sized square pegs in square holes. There are untold numbers of ways to do it wrong. There is only one way to do it right. Right works better.

BTW once the MAF xfer function is correct, it is stunning how quickly you can bring the fueling table around to what it is supposed to be. Your question about the VMP MAF and using the data from the Workbook has the same answer. The MAF needs to be flowed and likely calibrated. The MAF xfer table needs to be constructed from the calibrated MAF airflow performance and those will be the numbers you put into your MAF xfer function table in the tune.

Pro-M provides a standard 15 point MAF xfer table with each MAF they sell at no cost. You tell them the airflow range you require, they will build a MAF that provides that performance and provide you with a hardcopy table of the MAF performance that you can use for the MAF xfer function in your tuning software. If you don't know the range that you need your MAF to operate over then tell them the power you will targeting with the engine and they will build a MAF to support the airflow necessary and provide you with a 15 point MAF xfer table. BTW you can request them to build a MAF that mimics the air flow of a BA2600 or BA 3000 or some other known MAF. The difference is the one they sell you will actually produce that flow performance.

Most of the MAF providers, once the slot style meters came out, began the uninformed praise routine for the new style meter. As you can see from the earlier video, all the meter electronics are the same, some cost less to build and surprise, surprise when you are building hundreds of thousands of cars a year, cost of goods becomes an issue. The absolute best MAFs available anywhere are the original design Pro-M 80,92, and 117mm housings.

I use one of the original Pro-M 92 MAFs. Here are two pictures of my MAF. The first is from the side with the air cleaner on;

175676


The second (below) is looking down the throat of the meter in the direction of air flow with the air cleaner off;

175678


As you can see there is absolutely nothing that is in the air flow path. The actual sampling is done by the pitot tube at 12 o'clock. The pitot tube routes the air sample to the actual sensor for measurement and then returns it to the incoming air flow, post sensor, through an annular discharge port about an inch into the throat of the casting. The casting is machined to provide a Bernoulli effect style pressure drop right at the annular exhaust slit that is used to return the air sample to the metered air flow.

My meter is cast aluminum because it was one of the early meters. Current meters are a much nicer injection molded plastic (like in the YouTube vid) with a significantly smoother surface treatment at the entry for better airflow.


Ed
 

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Well I just finished watching those videos and man I wish I would have watched those when I was picking a MAF.

I originally had a BA2600 and then swapped that out for a VMP5000 slot style. What I did notice in the video is that they were testing the sensors in a draw through configuration. I am turbo so I would be a blow through configuration. That was the original reason that I had changed sensors. Don Lasota was very adamant that the slot style was the best configuration for my setup

So, although the videos were very informative, I'm still a bit confused. How different is a blow through vs draw through when it comes to signal quality? From what I've read, on this site and the web in general is that the slot style is the better choice for blow though. Chris in the pro-m video says that the slot style is not the best setup and should only be used in 05 and up cars. If running an 04 and older car then stick with a tonsil style MAF.

Thoughts?

In blow through mode, a given meter will allow a higher air mass to pass through. It has little to do with air flow dynamics and everything to do with the fact the MAF is located post compressor and the air density is higher because of being pressurized. When you explain your application, the Pro-M guys will ask you some questions and then make a recommendation.

The easiest MAF to implement (hook up?) is going to be a tube style MAF with a slot or tonsil sensor, although you will get a reduced signal quality because of the meter design. The more accut\rate but more difficult to implement would be the Pro-M 92 style (the size I suspect you will need/want) because you will need to fabricate a diffuser (cone style adapter) to go from the tubing size coming out of your intercooler to the flange diameter entering the Pro-M 92 meter.

With respect to signal quality, it is not determined by either blow through or pull through design. The good signal quality you see on th ePro-M 80. 90 and 117mm MAFs is solely the result of the mechanical design of the housing. A housing with an annular discharge from the meter electronics and a pitot tube style sampling port (like aircraft use) produces the signal quality you want to have for your meter.


Ed
 

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Discussion Starter · #29 ·
The Tuning Workbook MAF xfer function tables were correct for a particular MAF that was flowed (interestingly by Pro-M) years ago. MAFs manufactured today are similar but unless they have been calibrated they will be different than the data in the Workbook. This is one reason the SCT crowd got everyone pointed in the direction of fiddling with the MAF xfer function. If it was already wrong and fiddling could get a particular aspect of the problem, at a particular point in the engine operating rpm range closer why not fiddle, after all it's already wrong — we just don't know by how much.?

This is the absolute wrong way to tune the car. The approach is similar to putting injectors in the car that you don't know the flow characteristics of and then adjusting the AFR to get an injector pulse width that doesn't make the engine run too rich or too lean according to the O2 sensor(s). Will it work? Sure! Will it run as good as doing it the right way? Absolutely not! Will it create drivability problems that increase in severity the farther from the real settings required for the MAF and injectors you go — you bet.

There is always a way to fit a square peg in a round hole. The right way to assemble stuff is properly sized round pegs in round holes and properly sized square pegs in square holes. There are untold numbers of ways to do it wrong. There is only one way to do it right. Right works better.

BTW once the MAF xfer function is correct, it is stunning how quickly you can bring the fueling table around to what it is supposed to be. Your question about the VMP MAF and using the data from the Workbook has the same answer. The MAF needs to be flowed and likely calibrated. The MAF xfer table needs to be constructed from the calibrated MAF airflow performance and those will be the numbers you put into your MAF xfer function table in the tune.

Pro-M provides a standard 15 point MAF xfer table with each MAF they sell at no cost. You tell them the airflow range you require, they will build a MAF that provides that performance and provide you with a hardcopy table of the MAF performance that you can use for the MAF xfer function in your tuning software. If you don't know the range that you need your MAF to operate over then tell them the power you will targeting with the engine and they will build a MAF to support the airflow necessary and provide you with a 15 point MAF xfer table. BTW you can request them to build a MAF that mimics the air flow of a BA2600 or BA 3000 or some other known MAF. The difference is the one they sell you will actually produce that flow performance.

Most of the MAF providers, once the slot style meters came out, began the uninformed praise routine for the new style meter. As you can see from the earlier video, all the meter electronics are the same, some cost less to build and surprise, surprise when you are building hundreds of thousands of cars a year, cost of goods becomes an issue. The absolute best MAFs available anywhere are the original design Pro-M 80,92, and 117mm housings.

I use one of the original Pro-M 92 MAFs. Here are two pictures of my MAF. The first is from the side with the air cleaner on;

View attachment 175676

The second (below) is looking down the throat of the meter in the direction of air flow with the air cleaner off;

View attachment 175678

As you can see there is absolutely nothing that is in the air flow path. The actual sampling is done by the pitot tube at 12 o'clock. The pitot tube routes the air sample to the actual sensor for measurement and then returns it to the incoming air flow, post sensor, through an annular discharge port about an inch into the throat of the casting. The casting is machined to provide a Bernoulli effect style pressure drop right at the annular exhaust slit that is used to return the air sample to the metered air flow.

My meter is cast aluminum because it was one of the early meters. Current meters are a much nicer injection molded plastic (like in the YouTube vid) with a significantly smoother surface treatment at the entry for better airflow.


Ed
So the short answer to all of this is getting in touch with Pro-M to see what they recommend for my set up. I am interested in doing it the right way and thought I was. I've had an engine failure in the past so I don't want to repeat the same event again! Also I want drive ability to be spot on and I want to enjoy all of the hard work I've put into this car!

Thanks again Ed for your detailed information on this subject.
 

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Discussion Starter · #30 ·
In blow through mode, a given meter will allow a higher air mass to pass through. It has little to do with air flow dynamics and everything to do with the fact the MAF is located post compressor and the air density is higher because of being pressurized. When you explain your application, the Pro-M guys will ask you some questions and then make a recommendation.

The easiest MAF to implement (hook up?) is going to be a tube style MAF with a slot or tonsil sensor, although you will get a reduced signal quality because of the meter design. The more accut\rate but more difficult to implement would be the Pro-M 92 style (the size I suspect you will need/want) because you will need to fabricate a diffuser (cone style adapter) to go from the tubing size coming out of your intercooler to the flange diameter entering the Pro-M 92 meter.

With respect to signal quality, it is not determined by either blow through or pull through design. The good signal quality you see on th ePro-M 80. 90 and 117mm MAFs is solely the result of the mechanical design of the housing. A housing with an annular discharge from the meter electronics and a pitot tube style sampling port (like aircraft use) produces the signal quality you want to have for your meter.


Ed
The adaptor shouldn't be too difficult to fabricate. I have access to a lathe here at work and can do the work myself. I'm guessing it just needs to have a smooth transition from the tubing to the meter housing

Thanks again
 

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In general you are reading the tea leaves correctly Shawn. There might be a shortcut available to you, however. Pegasus Auto Racing offers a variety of excellent quality silicone rubber reducers to go from one size tube to another. If you make a simple flange (easy lathe work) for the MAF housing diameter then you weld a short extension onto it for the hose to be clamped to you can have your adapter relatively quickly and painlessly. Here is a link to Pegasus's silicone rubber adapters page => Pegasus Auto


Ed
 

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Discussion Starter · #32 ·
In general you are reading the tea leaves correctly Shawn. There might be a shortcut available to you, however. Pegasus Auto Racing offers a variety of excellent quality silicone rubber reducers to go from one size tube to another. If you make a simple flange (easy lathe work) for the MAF housing diameter then you weld a short extension onto it for the hose to be clamped to you can have your adapter relatively quickly and painlessly. Here is a link to Pegasus's silicone rubber adapters page => Pegasus Auto


Ed
Well if all I really need is a 3 to 4" adapter plus something made to transition / adapt it to the MAF then I'm all set. I have a 3 to 4 adapter here at home and I can fab the other piece at work! I guess there's a reason to keep parts laying around just for these moments.

Thanks!
 

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Discussion Starter · #33 ·
One more question. When adjusting the fuel table instead of the MAF transfer function,
Do I still need to lock the ECU in open loop when adjusting for AFR? Is it basically the same procedure , just not adjusting the transfer function.
 

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Open loop forces the engine to be fueled the way you commanded in the fuel table without modification for O2 sensor feedback. Closed loop will allow the ECU to recognize O2 sensor data and modify the commanded fueling to get to a stoichiometrically correct burn.

When you first start a cold engine it will be in closed loop because your tune will be commanding a rich cold start mixture until the engine comes up to temperature. Once the engine warms up the ECU will switch over to closed loop to maintain a stoichiometrically correct fueling model. This is how we simulate the presence of a choke on the old carburetors for cold start purposes on a modern day EFI system.

Ed
 
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