blow thru MAF question
Thread Starter
4th Gear Member
Joined: Apr 2008
Posts: 1,086
From: mi
blow thru MAF question
its time to mount the maf for the turbo. i called my tuner for him to get me a base tune and hes asking...
what kind of MAF am i using?
is it in its orginal case?
if not what size case is it in?
where is it located?
is it calibrated?
its going to be located on the straight pipe before the charge pipe goes into the intake and thats about all i'm sure about.
i have what i was TOLD was a pmas. i don't know if thats true or not and its in a looks like 90mm tube. should i use that? or should i go with a 05+ slot style? what should i do? and how do u get the MAF calibrated?
what kind of MAF am i using?
is it in its orginal case?
if not what size case is it in?
where is it located?
is it calibrated?
its going to be located on the straight pipe before the charge pipe goes into the intake and thats about all i'm sure about.
i have what i was TOLD was a pmas. i don't know if thats true or not and its in a looks like 90mm tube. should i use that? or should i go with a 05+ slot style? what should i do? and how do u get the MAF calibrated?
TECH SAVANT
Joined: Dec 2006
Posts: 10,937
From: Saint Augustine, FL
Does it have any markings on it, if so what are they; is it 90mm (have you measured it)?
Calibrating a MAF is an old kludgy way of making higher capacity injectors work with a stock tune, the MAF transfer function is "calibrated"¹ so that at lower air flow it lies to the PCM and tells it less air is flowing that really is--the unmodified tune then calculates a shorter injector pulse width that it normally would (the tune still thinks the stock injectors are installed) and is tricked into delivering the proper amount of fuel with the physically larger injectors. At higher airflows this deception is lessened and the PCM will deliver more fuel to account for the additional air pushed in by forced induction.
They ("calibrated" MAFs) create all sorts of problems for tuners because the actual transfer function are rarely documented or available--they also cause the PCM's load calculations to be messed up, which can lead to all sorts of other issues including destructive detonation.
So hope your MAF isn't "calibrated", also there is no need to have a MAF calibrated if you are altering the tune itself--it's only done IF the tune cannot be modified.
What you will need, if the MAF is not a well-known and unmolested unit, is the transfer function--a table that lists the output voltage of the MAF and the corresponding air flow.
Here's a graph of several Mustang MAF transfer function, show the table values as output curves mapping air flow vs. voltage.
If the MAF you have is a name brand unit that has not been messed with the tuner should be able to obtain the proper transfer function, if not you can get it mapped on a flow bench ($50 to $100), or get another that is known or has a transfer function document.
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¹ - "Calibrated" MAFs are adjusted to work with a specific tune (usually a stock tune), and specific capacity injectors (usually clearly marked on the MAF body).
Calibrating a MAF is an old kludgy way of making higher capacity injectors work with a stock tune, the MAF transfer function is "calibrated"¹ so that at lower air flow it lies to the PCM and tells it less air is flowing that really is--the unmodified tune then calculates a shorter injector pulse width that it normally would (the tune still thinks the stock injectors are installed) and is tricked into delivering the proper amount of fuel with the physically larger injectors. At higher airflows this deception is lessened and the PCM will deliver more fuel to account for the additional air pushed in by forced induction.
They ("calibrated" MAFs) create all sorts of problems for tuners because the actual transfer function are rarely documented or available--they also cause the PCM's load calculations to be messed up, which can lead to all sorts of other issues including destructive detonation.
So hope your MAF isn't "calibrated", also there is no need to have a MAF calibrated if you are altering the tune itself--it's only done IF the tune cannot be modified.
What you will need, if the MAF is not a well-known and unmolested unit, is the transfer function--a table that lists the output voltage of the MAF and the corresponding air flow.
Here's a graph of several Mustang MAF transfer function, show the table values as output curves mapping air flow vs. voltage.
If the MAF you have is a name brand unit that has not been messed with the tuner should be able to obtain the proper transfer function, if not you can get it mapped on a flow bench ($50 to $100), or get another that is known or has a transfer function document.
----------------------------------------------
¹ - "Calibrated" MAFs are adjusted to work with a specific tune (usually a stock tune), and specific capacity injectors (usually clearly marked on the MAF body).
Underboss
Joined: Jan 2006
Posts: 20,272
From: Helaware
Absolutely go with the 05+ slot style
This is the unit I run http://www.vmptuning.com/store/index...=234&parent=29
This is the unit I run http://www.vmptuning.com/store/index...=234&parent=29
TECH SAVANT
Joined: Dec 2006
Posts: 10,937
From: Saint Augustine, FL
The significant (maybe only) advantage of a slot-style MAF sensor is that the design is inherently better capable of providing accurate flow measurement, with a non-linear/turbulent flow through the MAF housing. This is certainly a good thing, however it does not automatically make point sensor MAFs obsolete.
Properly configured and plumbed a point sensor MAF can work just as well as a slot-type.
BTW and FWIW, the stock 80mm MAF can report up to 3000lb/h without pegging. At 11.5:1 AFR (f/i) that would use 260lb/h of fuel, and support 435fwHP give or take.
A typical 90mm MAF will work (without pegging) right up to the PCM's 3800lb/h limit, this is around 550fwHP at 11.5:1. After that the settings described in the sidebar on the above graph need to be scaled.
Note: The "maximum" HP values above are design calculation limits, real world results will vary.
Properly configured and plumbed a point sensor MAF can work just as well as a slot-type.
BTW and FWIW, the stock 80mm MAF can report up to 3000lb/h without pegging. At 11.5:1 AFR (f/i) that would use 260lb/h of fuel, and support 435fwHP give or take.
A typical 90mm MAF will work (without pegging) right up to the PCM's 3800lb/h limit, this is around 550fwHP at 11.5:1. After that the settings described in the sidebar on the above graph need to be scaled.
Note: The "maximum" HP values above are design calculation limits, real world results will vary.
Thread Starter
4th Gear Member
Joined: Apr 2008
Posts: 1,086
From: mi
i'l get a picture of the maf i have here in a little bit maybe we can find out what it is. but i'm going for 550-600whp and on my vortech setup i was pegging my MAF and i don't want that to happen again id rather buy the right thing now and be sure that i won't have any problems with it.