Great read on what to know before tuning your car

by Shelby10' 4/24/2011, 5:04 pm

Stole this from another forum and thought it was a great read:
Here us the link to the forum Thread: http://stangsunited.com/showthread.php?3803-Warning-!!-Before-you-change-that-tune-read-this!

"Due to the fact that many Mustang owners are modifying their cars today to the point of taking the HP, fuel and timing demands well past the stock calibrations many of these cars now require professional tuning.

The problem the Mustang community is facing is finding a tuner who knows and understands how to tune a mass air car properly and does it the way FMCO does it.

Unfortunately for the community today outside of Ford Racing and those who work closely with Ford Racing there are very few tuners if any out there that do tune correctly which is why I felt it necessary to post this warning to all!

Great read on what to know before tuning your car 127cai

Great read on what to know before tuning your car 127cai

MAF basics By Jim LaRocca

Some basic info about MAF and MAF transfer curves.

Understanding a mass air meter and why it so critical to have the correct meter curve in a tune.

This is where 99 percent of the tuners get themselves in trouble and it all starts from step one.(The Mass Air Meter and Meter Curve) Lets not even worry about the rest of the tune (that's a completely different story)the first and most important step all starts here.

The MAF meter is the first point where air enters the motor and every calculation and I mean every calculation the computer does will depend on that being a actual and real measurement. (Load, Idle,part throttle, WOT, A/F, timing, torque calculations ,etc. all depend on it)

The main purpose of a Mass air meter is to measure airflow.
The Meter operates in a range from 0-5volts
5 volts being the highest it could read

Every voltage point from 0-5volts for a given mass air meter and sensor represents an actual air flow measurement.

So if you put a MAF meter housing with a sensor on a flow bench you can obtain a mass air transfer function for that given meter sensor combo.(A mass air meter will only work correctly/measure correctly if these values are accurate)
So lets say this is the data you obtained after flowing the meter on a flow bench.(And by the way this is exactly how Ford does their mass air meters and curves)

example
0 volts = 0 airflow
1 volt = 500 CFM
2 volts =800CFm
3 Volts =1200 cfm
4 volts = 1500 cfm
5 volts =1800CFM
every voltage point in-between those valves will also equal a CFM valve somewhere between them .(Just using whole numbers for this example.)

If you needed A MAF meter to measure more CFM, there is two ways to do it correctly.
One use a different sensor that has a different range in the same housing.
Two use the same sensor but increase the size of the housing

Another note since CFM is a direct relation to HP this is how a computer can/will calculate the torque the motor is making at a given RPM.(one way how torque management works/is calculated)

It takes 1.5 CFM to make 1 hp

Knowing this, you can take a mass air voltage/reading from your MAF and calculate how much HP your engine is making.(But again only if you know the meter and meter curve is accurate)
Believe it or not this is how top fuel teams figure out how much HP their engines make(Hard to dyno an engine making 5000hp plus HP, no dyno can really read that high, until maybe the last couple of years) They measure how much CFM the engine is moving and then calculated that into HP

Now going back to one of my first statement's that 99 percent of the tuners get themselves in trouble here and cause all kinds of issues ranging from bad startups, pinging, driveabilty issues, idle issues etc.
Here is why

Most tuners out there were TAUGHT.... to adjust the A/F ratio by moving the transfer curve in the tune. (Will it change an A/F ratio it sure will...........) They really don't understand how a mass air system works. (If they did they would NEVER do this) Its really a shame because most tuners feel this is the correct way to tune.(they really believe they are tuning correctly)
Why ... again because this is the way they were shown. Since they were shown that, it has to be correct way. They were never actually shown or understand what that mass air meter is doing or suppose to do.

They were also taught to create a mass air curve from scratch or adjust a curve by datalogging short terms or using an A/F gauge to tweak or enter a value in the curve depending on the short term voltage or the a/f ratio measured coming out the tailpipe.
They will move a curve up or down until they get the a/f ratio they are looking to obtain.

So lets see why this is the wrong way of doing things
Lets look at the example data above created from a MAF metering using a flow bench.

Lets take the 2 volt measurement which equals 800 CFM (which we know is a real and actual air flow measurement for this example)

We are driving our car and the mass air meter is at 2 volts.
OK the computer will take that 2 volts reading and start calculating how much to open the injector to hit a target A/F, referencing the air fuel ratio target map. (If the injector slopes and all are correct in the tune and depending on your fuel pumps/system etc. whatever you have in your target a/f will be what you will obtain out the tailpipe)

It will also look/calculate load, timing maps etc. from this measurement but lets just look at the A/F ratio here.

If for some reason (and can be many) the target a/f is suppose to be 12 to1 and 10 to 1 is coming out the tailpipe.

What the tuner will do instead of adjusting the correct parameters is they will take the 800 CFM value at 2 volts and make it a smaller CFM value/ number in the maf curve to trick the engine in thinking its moving less air.
If the engine thinks its moving less air it will calculate the injector not to open as much delivering less fuel, which will cause that 10.1 A/F to hit the 12.1 A/f that is targeted.

So what they do and how they tune, is by looking at or only caring only about the A/F ratio.
Every other calculation done at that point by the computer will be wrong..... why ....................because it is thinking it is moving less air than it really is now!!!! This could potentially be very detrimental to the engine and even lead to catastrophic engine failure especially on highly modified engines.

This is a real basic and simple example.
I hope this helps your understanding of why and how important it is to really know what that mass air meter is measuring and what the MAF curve does in the tune.

A few years ago it was more forgiving when the drive by wire didn't exist to tune by moving or creating a MAF curve the wrong way.

Drive by wire and or highly modified cars will only amplify issues when a car is tuned with an inaccurate MAF or MAF curve.

There are many more other unintended negative affects that will occur as a result of a tuner who changes a known MAF curve that has been established on a professional flow bench,( like the one Ford uses) for the purpose of adjusting air/fuel but I’ll leave that for another day.

Some interesting reading here about tuning and Maf calibration.
Ford Racing parts catalog ….Read page 154 bottom paragraph

page 220 explains a little about the maf and its calibration"
http://www.fordracingparts.com/2011-catalog/

Some interesting quotes and discussion question and answers from the forum I got this from.

ok....lets tackle this from a pragmatic view.......starting with the presumption that you want to tune correctly per the above......

1. do any of the MAF/CAI manufacturers/sellers have and provide a meter curve? How can a consumer find out if this info is public for any particular unit system. (I am assuming here that curve is developed using filter and housing/maf/sensor/tube into TB)

2. If this info is not public, how do you get a curve...it appears that many if not most tuners are not obtaining this curve. Do we know of any tuners that will do this for a consumer? What kind of cost? Do you have to send them your unit to have them flow?

3. What tuners out there subscribe to the use of a curve as the essential foundation? Other than learning how to tune yourself, a typical consumer has to come up with someone to do this.....even if a good tuner believes you must use this process, go back to #1 and #2 above....lots of MAF/CAI combos out there......do we have to find a tuner and then purchase the sole unit that they have curve data for? If no one is in your area, do you have to drive your car to them (eg TASCA)?

My educational foundation is chemical engineering, which includes fluid flow courses, and I have no problem accepting the technical need for a maf/cai curve as a essential foundation of a perfect tune....but the devil is in the details, and figuring out when a maf/cai does not present a typical curve and requires its own flow testing is not something most are prepared to deal with. So for most of us the issue really comes down to "I have an existing maf/cai system and tune, now what the heck do I do?" Not trying to beat on anyone or stir things up, but for most this is useful information on an academic basis, but not useful for implementation. What we really need to do is now bridge the issue so that owners can actually take actions that will lead to accurate tuning.

I would be most interested to see if others have the same feelings, and most importantly, if any of the members with technical expertise have more specific ideas for action for the typical owner.....thanks in advance...John
1) ...only the MAF tube with the sensor inserted needs to be flowed. Anything upstream (e.g. filter) only affects *how much* flow the engine sees but does not affect the accuracy of a properly flowed MAF across it's flow range.. The CJ MAFs are flowed for sure. Unfortunately most tuners use exsting curve functions (possibly with other sensors) and then scale/adjust them for different sensors/MAFs based on target A/Fs ...that's where the problems start since everything downstream in the tune is then effectively 'currupted' ...garbage-in/garbage-out.

2) ...companys like PMAS (Professional Mass Air systems) have the ability to natively flow (no scaling) anthing these engines can handle -- they do it for pro racers al lthe time. Only the meter-in-tube needs to be flowed. Then the [mathematical] curve that relates that flow range to the 0-5v ECU voltage range can be created. That accurate mapping offlow-voltage is the key and is what's called the Mass Air transfer curve/function -- it's a tiny piece of the overall calibration but affects so much because nearly *everything* in a mass air managed engine depends on that curve being 100% accurage to determine when and where it dynamically pops into/out-of many, many control-calibration tables (and the paths it takes through them) as you run our engine.

3) Only the MAF gets calibrated -- every tuner subscribes to using the mass-air transfer function because the engine simply won't run (at all) without it and will run poorly if it's just off a bit off from true/accurate flow. The problem is *how* they use it. The *only* correct/proper factory-engineered way is to base the curve's calibaraion on dead-nuts accurate flow -- and then it *never* gets changed for that MAF sensor and MAF tube combination (i.e. the MAF). The improper way is to get it close enough (sometimes through trial and error and sometimes based on scaling/estimating working off an existing curve/sensor -- yikes!! -- really!) to get the engine to run and then tweak the short-terms to fake it out to hit 'target' A/Fs, with the result of inducing inacurrate 'pathing' through those many many tables that are especially critical at WOT (where being off a couple % on a table-pop can be the diff between nice-engine and scrap-metal), but also affect closed-loop cruise, idle, etc. ...and to address MILs, you can turn off most all the safetys that produce them, etc -yikes!- ...'nough said.

This dangerous tweaking practice grew out of a long legacy of 'approximate' tuning with it's roots back in the days of Speed-density engine management (an widely-used but inferior pre-cursor of Ford's Mass-air engine management) back when Ford's calibration methods were still being decifered/hacked by many racers (blackshelby was one of those who was at the forefront of deciphering Ford's methods 20+ years ago ...which is why he knows how it goes -lol). While those days are mostly gone, the 'addiction' of tweaking has lived on -- I must conclude at this point it's 10% history and 90% interlock of the customer to the tuner. Why? When the MAF is flow-accurate, many mods can be swapped and none of them will affect the MAF so long as it still has meter capacity. When the MAF curve is 'tweaked' to given set-up virtually any change requires re-tweaking (just to get back to a running, but innacurate, calibration) ...if you were a tuner competing for customers and repeat business, you might be inclined to 'play' the characteristics of the latter -- ya think?

John, I only have a 'book' understanding of this since I've never tuned a mass-air car myself, but the principles are indisputable -- the MAF is the heart of engine management. If it's off you're at risk. Of course, there's other ways to hurt an engine (excessive timing on the edge of octane, fake-out devices, etc) but the potentially damaging implications of those just get worse magnified through the distorted lens of a corrupt MAF transfer curve. As a general rule, the further you push to the limits of the engine's combustion engineering, the more critical accurate combustion management becomes, and the greater and more sudden the consequences of it being other than 100% accurate -- and there is *nothing* that affects this more deeply and broadly than an accurate MAF function.

I know I didn't answer all your questions (who has what and how to get it) but the above is trying to explain why/how things are the way they are so you can see why things have lived in the gray shadows for so long. As I've said before, any manufacturer of a MAF tube should be publishing the flow data with the product for the factory sensor and maybe a tested higher-range sensors (e.g the HPX) since they're not all identical in shape so really have to be flow calibrated as part of the tube (MAF) assembly. Tuners can then use that information (and customers should demand that only that flowed data is used in any tune they buy) and even savvy owners who might have Sniper or other software that would let them map the flow to the voltage range, etc. Better still, the MAF tube maker could provide those transfer function curves/maps as well ...but don't hold your breath. Remember, folks can hurt themselves very easily and parts-makers are much happier letting a tuner take that risk for you, etc. That last part is jmo, but seems pretty clear to me it might not be wise having the average owner trying to set-up their own tunes unless they know what they're doing. That's why I say the info should at least be made available to tuners, and the customer should deamnd it's used (vs tweaking) in their tune.

Just some thoughts...

by Shelby10' 4/24/2011, 5:10 pm

*INFO TAKEN FROM 2008 FRPP CATALOG

DYNAMOMETER TESTING AND FORD RACING CALIBRATIONS
“Why do certain companies claim to make more power with their power upgrade kits than Ford Racing
does with their kits?” To address that question properly, it is necessary to understand some of the
intricacies of chassis dynamometer testing as well as some of the compromises that must be made in
order to simultaneously meet performance, emissions, durability and safety objectives.
Chassis Dynamometer testing
There are two types of chassis dynamometer (dyno) in widespread
use today.
• An inertia dyno uses a large spinning drum that is accelerated by the
drive wheels of the test vehicle. Power is then computed by knowing
the inertia of the drum and how quickly it was accelerated. Torque can
then be calculated by knowing the speed of the drum.
• An eddy-current dyno absorbs and measures power by rotating a
metallic disc through a magnetic field.
Without getting into which dyno is more “correct” under what conditions,
and why, we will simply say that these two types of dyno typically do not
always give the same result even with all else being equal. It is generally not possible to accurately
compare numbers from one type of dyno with those from the other type of dyno. Each type of dyno has
its own advantages and disadvantages, but as long as all the tuning work is done on the same type of
dyno, it doesn’t really matter which one is used.
With any dyno testing there is a need for correction factors that are applied to the raw numbers the dyno
actually measures. These correction factors are an attempt to correct for varying atmospheric conditions
such as humidity, barometric pressure and air temperature. The two most common standards are SAE
J1349 and SAE J607 (sometimes known as “STD” on some dynos). How correction factors are calculated
is given in the “Crate Engine” section of this catalog. For this article, understand that these correction
factors will give results that are different from each other with SAE J1349 typically about 4% lower than
SAE J607. OEMs will almost always quote J1349 corrected numbers when advertising horsepower
and torque.
Whenever comparing dyno results, always be sure that the numbers are corrected to the same standard.
Despite these correction factors, atmospheric conditions can play an additional role in terms of ignition
timing. The correction factors account only for the change in the density of the air due to atmospheric
conditions and cannot account for things like engine borderline spark sensitivity. As inlet air temperature
increases, the PCM will generally retard spark to prevent detonation using the particular octane of fuel for
which it was calibrated. Correction factors cannot account for this because different engine designs can
have different spark sensitivity and different sensitivity of torque relative to ignition timing. Basically this
means that the closer the actual conditions are to the SAE J1349 standard (77 deg F inlet air, 29.31 inHg
barometric pressure) the more comparable the results are to those quoted by the manufacturer.
Most horsepower numbers in the Ford Racing catalog have been determined by using the
SAE J1349 standard.
When testing a particular calibration or performance enhancing part by performing back to back dyno
runs, it is critical to keep test conditions as similar as possible between the runs. This sounds obvious,
but is very commonly overlooked by many aftermarket companies who frequently publish dyno charts
depicting large gains, but fail to give all the necessary data to show the tests were run under similar
conditions. In order to be certain that the test conditions are as similar as possible, the following data is
mandatory and needs to be collected for each run:
• Ambient air temperature
• Barometric pressure
• Inlet air temperature (on a forced induction car, this is usually downstream of the power adder)
• Air/fuel (A/F) ratio (preferably upstream of any catalyst)
Truly meaningful power numbers cannot be collected without this data!

It is also a good idea to make sure the A/F ratio sensor in use on the dyno has not been exposed
to leaded fuel and has not been in service for an excessive period of time (greater than six months,
depending on frequency of use). A/F ratio is the single most important parameter to measure accurately
when doing any sort of dyno tuning, so it is critical the sensor is providing accurate information. When
doing any PCM calibration on a dyno, the resulting calibration will only be as good as the A/F sensor.
These additional inputs should be used for ideal dyno testing and calibration.
• Air/fuel ratio and spark advance commanded by the PCM
• Fuel injector pulsewidth
• Fuel pump duty cycle (in the case of ERFS)
• MAF sensor voltage
• Fuel pressure
• Engine oil temperature
• Differential oil temperature
For Ford Racing calibrations we use all of the data inputs listed both as mandatory and ideal.
How drivetrain affects wheel horsepower:
Most chassis dyno tests are performed using the “roll-on” method, where the vehicle’s drive wheels are
accelerated in a particular gear from a low speed to a high speed (generally to the rev limit of the engine)
in one continuous sweep. Because of this constant acceleration, engine and transmission inertia, drive
wheel inertia, gear ratio, and axle ratio can all affect the final measured horsepower. Generally a heavier
wheel will take more torque to accelerate at the same rate as a lighter wheel, so heavier wheels will tend
to reduce the measured wheel horsepower. Gear ratio comes into play because as the gear ratio strays
from a 1:1, the efficiency drops and therefore the measured horsepower at the wheels also drops. This is
why most dyno runs are run in the 1:1 gear (i.e., 4th gear in a 5 speed overdrive transmission) whenever
possible. The same logic applies to axle ratio as well, which means that changing nothing but axle ratio
can have an effect on measured wheel horsepower. Remember, this does NOT change brake (flywheel)
horsepower, only the delivered wheel horsepower due to the change in drivetrain efficiency.
How calibration can cause misleading dyno results:
Production calibrations have an inferred catalyst temperature protection model which constantly calculates
the temperature in the hottest part of the hottest catalyst. This calculated temperature is based on many
PCM parameters, such as engine speed, load, ingested air mass, time, inlet air temperature, EGR flow rate
and many others.
When the catalyst model calculates that the catalyst temperature is about to exceed a level that is safe for
the catalyst (generally around 1650 deg F), the PCM will richen the A/F mixture as necessary to lower the
exhaust gas temperature and cool the catalyst. This richened A/F ratio will decrease power output, but is
absolutely necessary to keep the catalyst from being permanently damaged. Unless A/F ratio is monitored
during a dyno pull, the dyno operator will have no idea when catalyst temperature protection has been
invoked and can make erroneous conclusions with regard to power output.
As a trivial example of how this can affect dyno testing, consider a supercharged production vehicle with
production calibration performing back to back runs under identical conditions except as noted. The car
is driven to a dyno facility and immediately put on the dyno and a run is performed, yielding a result of
420 hp. In this example, A/F ratio is not monitored. A part is swapped for another “high-performance”
part and another dyno run is performed, resulting in 430 hp. The dyno operator concludes the “high-
performance” part is worth 10 hp. This is not accurate because when the car was first dyno tested,
its catalysts were sufficiently hot that catalyst temperature protection was invoked during the dyno pull
which reduced power output by richening the A/F ratio. While the car was having the parts swapped,
the catalysts cooled down enough that during the next dyno pull catalyst temperature protection was not
invoked. The engine made more power on the second pull because it was running a leaner A/F ratio
closer to optimal and not necessarily because of the “high-performance” part. If the dyno operator was
monitoring A/F ratio, this would have been readily apparent.

If the operator was monitoring the A/F ratio commanded by the PCM, the invocation of catalyst
temperature protection would become self evident. In this example, the erroneous conclusion that was
reached suggested the “high-performance” part was worth 10 hp when it really wasn’t, but the opposite
can also occur quite easily. Without covering every possible scenario, it will suffice to say that dyno
numbers are ONLY meaningful when supporting data such as A/F ratio, inlet air temperature and the
others listed above are also provided.
There is also a model for oxygen sensor protection and exhaust valve protection that when not taken into
account can cause misleading dyno data. In general, exhaust temperatures greater than about 1650
deg F can damage exhaust valves, and extreme care is taken in production calibrations to ensure that
sustained engine operation beyond that temperature does not occur. This is rarely an instantaneous
failure but rather one that over time “tulips” the exhaust valves and ultimately will fail the engine.
Cold-air kits that claim to work without the need of a PCM recalibration are a common source of
misleading dyno power claims. Some of these kits claim enormous power gains using nothing but their kit
and a production calibration. Most of these claims are not supported with A/F, inlet temperature or spark
advance traces during the dyno pulls that are shown in their advertising. In some cases, the apparent
increase in power is due to differing dyno test conditions as mentioned previously, while in other cases
they can be due to the fact that the MAF sensor transfer function in the PCM is left stock. If the cold-air
kit flows more air, and the MAF transfer function in the PCM is stock it will not “know” about the extra air
that’s entering the engine. This will result in the engine running an A/F ratio that is leaner than it should
be for engine durability. While this has the potential to produce more power, it can also be potentially
damaging to catalysts, exhaust valves, piston rings and other engine components. The commanded spark
advance can also be incorrect and result in detonation or pre-ignition with potentially catastrophic results.
Air inlet restrictions generally only become significant at higher airflows, so if a claim is made that a cold-
air kit increases torque at 2000 rpm without the aid of a calibration, you can be sure that varying dyno
test conditions or a significant change in A/F ratio are the cause. Ask for more supporting data!
Similar misleading results can be caused by a failure to keep inlet air temperature constant between runs.
The PCM will retard spark timing to prevent detonation as inlet air temperature increases, lowering power
output. On a forced induction car, the inlet air temperature is generally measured after the power adder
(and after the intercooler, if applicable) and can be MUCH greater than ambient temperature. Careful
monitoring of A/F ratio, and inlet air temperature, are critical to making accurate conclusions regarding
the effectiveness of various high-performance parts.
Secondary factors that also affect measured wheel horsepower are engine oil temperature, differential oil
temperature, humidity, etc. It cannot be overstated that all conditions need to be as similar as possible
between dyno runs in order to have a meaningful scientific conclusion, which requires the supporting data
previously discussed.
Ford Racing Calibrations
The calibrations that Ford Racing provides for our cold-air and supercharger kits are done by Ford
engineers who, in many cases, worked on the actual production vehicles. No one is more familiar with
Ford engines and Ford control systems than Ford engineers. Extreme care is taken to provide as much
power and torque as can be safely delivered, but also to deliver high durability and exceptional drivability.
Most of our kits are also 50-State emissions legal and many are now even offered with a Ford Racing
limited warranty.

Here are a couple of aftermarket tuners practices that we do NOT recommend:
• Turning off the inferred catalyst, oxygen sensor and exhaust valve temperature protection logic
discussed in the previous section. This prevents the PCM from richening the A/F ratio to protect
these components which can result in more power under certain conditions. The downside is
drastically decreased durability of these expensive components. Ford Racing does not compromise
durability by turning off this calibration logic.

• They often advance spark timing to potentially unsafe levels. We test our calibrations in a wind tunnel
and in hot dry weather to verify that potentially damaging spark knock or catastrophic pre-ignition does
not occur. We also do cold weather and altitude testing as well as extensive emissions and durability
testing on several vehicles before we release a calibration to the customer. Some companies do not
realize that they need to perform this type of testing in the first place!
Automatic transmission calibration is an area that Ford Racing sets itself apart from other “tuners”. We
generally make extensive calibration changes to not only improve shift quality and give the transmission a
more performance oriented feel, but take great care to ensure that durability is not compromised to levels
we feel would be unacceptable to a customer. In development we monitor things like clutch slip times,
slip energies, band temperatures and other variables to make calibration changes as appropriate so that
the customer can be sure of a quality product that will continue to deliver improved performance in the
long term. As mentioned before, these changes are performed by the same engineers who designed and
developed the vehicles in the first place, and who are more familiar than anyone with their performance
and durability envelopes.
Some aftermarket tuners develop their calibrations exclusively on a chassis dyno and go straight to
the end customer. While dyno work is a critical part of the development process, it is only one piece
of a complex puzzle. Calibrating for wide open throttle (WOT) is generally simple, but the bulk of the
calibration effort is getting the part (and closed) throttle drivability correct. Our calibrations are developed
not only on the dyno, but also on the street for production (or better) quality drivability, and across many
vehicles to allow for manufacturing tolerances. Varied driving conditions, constant data monitoring, and
long-term testing ensure consistent drivability.
In recent years, cars and trucks have shifted toward electronic throttle control (ETC) or “drive-by-wire”
systems for packaging, cost and enhanced calibration functions. Ford Racing calibrations for ETC
vehicles take advantage of some of the increased functionality offered by these systems by changing the
relationship between the pedal and the throttle for improved “performance feel”. This allows us to provide
substantial improvements in “performance feel” even on the kits where the peak horsepower increase
might be considered modest by some. The peak power numbers do not always tell the whole story.
Why some companies claim to make more power:
Some claims are due to poor and misleading dynamometer test practices. Others are genuine but at the
expense of engine, catalyst or drivetrain durability.
Hopefully this article gives you the tools necessary to determine what is real dyno horsepower,
manipulated false horsepower and temporary horsepower waiting to cause a failure. We are confident
that as a potential customer you will agree that no one knows your car or truck better than the Ford
engineers who designed it in the first place. Our kits offer the best blend of performance, durability and
drivability that exists on the market today.