ddnspider

iTrader: (26)

Shout out to joecar and Greg Banish for teaching me most of what I know

WARNING- I take no responsibility for you following this and blowing something up. Use your head, ask questions, and stay conservative and everything should work out.

I've seen a lot of questions over the years and especially lately about HAVING to remove the MAF once you start making a certain amount of hp; either because its a restriction or because it won't/can't read enough airflow. While we can argue whether or not the MAF is a restriction, very few people I see understand how to get around the max limits of the MAF and assume you must remove it. Many people dont realize that they do have options instead of ditching it and going speed density, so this is a tutorial to help others understand the option and what it takes to keep a MAF.

MAF Alternatives

Most are aware of the 85mm truck maf's, but many dont know that there is the option to put an LS7 MAF on their car very easily. The LS7 MAF is a cartridge style and there are a couple companies that make 4 inch tubes that allow the LS7 MAF to bolt on. Also, what I would consider very important is the airflow straightener, aka. the honeycomb. See below photos of the LS7 maf tube and air straightener. With how large the 4" tube is, having a honeycomb to straighten the airflow across the sensor can make a huge improvement in things like idle quality. Several companies also sell an LS7 to LS1 harness adapter so its truely plug and play. One of the photos is courtesy of Carlrx7 from the HP Tuners forum. Saxon makes the honeycombs and Spectre makes the 4" tube among others.

Why do we need to change MAF's???

The factory PCM has 2 hardcoded limits. One is the MAF frequency that is typically something like 12kHz. The other limit is the maximum airflow which is something like 64lb/min of airflow. The following posts will discuss what to actually change in the tune to scale it. As for the MAF frequency, the frequency the MAF sees is based on how much airflow is moving across it. This is because the frequency output is proportional to the amount of cooling that happens as the airflow cools the hot wire inside the MAF. By moving to an LS7 MAF in a larger tube, this allows more airflow per given step in MAF frequency Typically you can get away with the stock MAF with a scaled tune to around 600rwhp. Above that, you may need to move to a larger MAF.

ddnspider

iTrader: (26)

Too much Powwwwa
The factory LS1 PCM is hard coded to 64lb/min of airflow. There is no way around this in the tune.......EXCEPT, you make the computer THINK that there's less than 64lb/min of airflow even if there's actually more. How do we do this? The PCM needs to know 3 basic things:

1. How much airflow is being consumed
2. How much fuel is being injected.
3. What size is the engine

By telling the PCM that the engine is smaller by a certain percentage than it actually is, and is consuming less air and fuel than it actually is, you can exceed the 64lb/min hard coded limit in the PCM. For example, you have a combo that is:

• 427c.i motor
• planning on 1000fwhp
• 120lb injectors

There is no way this combo will work with a factory MAF and regular tuneup as you'll max out the MAF frequency and airflow limit super early in the RPM range. Now, if you tell the PCM that the motor is 50% smaller than it actually is, and is consuming 50% less air and the injectors being used are 50% smaller than they actually are; you will have a computer that thinks its controlling a 213c.i. motor with 60lb injectors making 500fwhp. The PCM CAN understand and control this very well. You will be able to tune a MAF exactly like a stock car. The point is to use a single scalar and scale everything by the same ratio, 50%, 75%, etc. The cool thing about this is when you log the car, things like injector duty cycle are all still accurate since everything is scaled by the same amount. If youre curious about how much airflow you're consuming, you just need to take the value in the log and divide by the same ratio to see your actual airflow.

My personal experience was:

• 383c.i
• 15psi from a T76GTS turbo
• 60lb injectors

The combo used an LS7 MAF in a 4" cartridge as outlined above and made ~900fwhp. I'm actually in the process of doing this to a friends car with a 5.3/T76 swap, so making this tutorial is timely lol. Now lets get into what you actually have to change.....

ddnspider

iTrader: (26)

Details Details
Now comes the real work. What tables do I scale and what tables do I leave alone?? For the most part, anything that references grams will need to be scaled since its either talking about grams of airflow or grams of fuel or grams per cylinder and you want the PCM to think there is less of everything going into the motor. The exception to this is I've found that the scaling of the idle tables usually needs to be less than the overall scaling of the tune. I.E. if you scale the tune by 50%, then scale the idle tables by 25% and see how it works. I believe this has to do with resolution since you do lose some resolution at low airflow by doing a scaling. ***See page 2, as Darth didn't scale his idle tables at all and it worked well for him***
Here is the list of engine tables I scaled (I'm an EFI Live guy, but will include table names for cross referencing to HPT):

Comparison summary: 10:23:29 pm, Friday Jul 14, 2017
B0101 Main VE Table
B0102 VE while Cranking- EDIT DO NOT MODIFY THE CRANKING VE. I discovered that even if the car is set to MAF only mode, it will try to use the cranking VE table for start up.
B0104 Cylinder Volume
B0503 Purge Canister Min Air Flow
B0506 Purge Canister vs Vac
B3201 Initial Fuel Prime
B3204 Non Sequential First Fuel Pulse
B3206 Non Sequential Second Fuel Pulse
B4001 Injector Flow Rate
B4107 Closed Loop Mode-This one should be confirmed after the initial OL tuning is done. I ended up back to stock on this.
B4307 Desired Airflow
B4308 Airflow Parked
B4354 A/C Airflow Ramp In
B4355 A/C Airflow Ramp Out
B4361 A/C Torque Loss Correction Ramp Out
B4303 Startup Airflow Correction
B4305 Startup Airflow Decay in Drive
B4309 Throttle Cracker Airflow in Gear
B4313 Throttle Cracker Decay Rate
B4315 Throttle Follower Airflow
B4317 Throttle Follower Decay Rate in Gear
B4319 Throttle Follower Decay Rate in Park
B4340 Startup Airflow Decay
B4343 Startup Friction Airflow in Drive
B4344 Startup Friction Airflow Decay
B4503 Filtered RPM Airflow Control Delay
B4504 Airflow Learning Control Delay
B4511 Startup Engine Underspeed Time Limit
B4512 Filtered RPM Airflow Correction
B4514 Learned Airflow Correction
B4515 Direct Airflow Correction
B4521 Maximum Idle Short Term Correction
B4317 Throttle Follower Decay Rate in Gear
B4336 Rolling Desired Idle High Correction
B4337 Rolling Desired Idle Low Correction
B5001 MAF Sensor Calibration
B5913 Spark High-Octane TableSee next post for info on main spark tables
B5914 Spark Low-Octane TableSee next post for info on main spark tables
B5932 Base Spark in Gear
B5933 Base Spark in Park/Neutral
B5910 Spark ECT Table
B5911 Spark IAT Table
B5919 Optimal Timing
B5934 Idle Flare Control

ddnspider

iTrader: (26)

Spark Tables
Most of the tables above are easy.....highlight entire table and multiply by a percentage, done. EXCEPT the spark tables. The axis on the tables are in grams/cylinder. It means you need to shift the high and low octane tables as well since grams is on an axis of the table. To do this, its best to copy it to an excel spreadsheet. Start with whatever is the largest g/cyl in your table. Let's pick 1.0g/cyl. Say you want to scale it by 30%. This is the same as multiplying it by .7. So 1 times .7=.7. You then copy the column of spark values from your 1g/cyl column and move it down to your .7 column. Rinse and repeat working your way to the left until you have no more copy/pasting. I attached a couple sample images taking an initial blower tune with no scaling to 1 that is scaled 30%. Notice how the entire spark table shifts to the LEFT. This one is important when you're boosted as you want to make sure you dont have idle/cruise timing in a g/cyl column that is WOT. It just takes a little patience, but its straightforward.

ddnspider

iTrader: (26)

Transmission
T56 need not apply For 4L60E cars, since everything that is in grams is getting scaled, anything referencing Nm or Ftlbs would also require a similar scaling/shift like the spark tables. Since injector data and airflow data is now scaled, delivered engine torque will also be scaled. For example, {D0701}Base pressure 1-2 shift is referencing delivered engine torque in ftlbs. Since our calculated engine torque will be less now given our "smaller motor with less air/fuel flow", we must shift the trans pressures down so that we still provide sufficient pressure to the transmission so it doesn't slip under power. The same would apply to the other transmission tables.

EDIT...be careful here as you may find your lower power cells end up with too much pressure and may want to drop them back down closer to stock. You don't need a bunch of pressure when you're idling and/or cruising.

ddnspider

iTrader: (26)

Glad I left 1 post left in the tutorial. Shout out to @ChopperDoc for making great Youtube videos on how to tune the MAF.

Creating MAF Baseline in Speed Density -


MAF Tuning -

truckdoug

iTrader: (25)

cool! nice work. I really wanna try a maf tune on my next turbo build

subeone

iTrader: (5)

good write up thank you for adding to this section of tech. I was beginning to lose hope

one thing to note is that IDC does not depend on engine size/airflow, just pw rpm and time!

ddnspider

iTrader: (26)

Cool man, yeah try it out and see what you think.

Thanks. I agree about the IDC. I said it was still accurate, I should have been more clear that it is the same as before the scaled tune.

As an update, I literally just did this scaling on a 5.3/turbo swapped Camaro and it runs awesome, didnt max the MAF and was between 750-800fwhp on low boost.

Darth_V8r

iTrader: (4)

OP, very nice write up, and thank you!

Also, thank you to whoever made this a sticky

G Atsma

Agreed! Good reference material!

ddnspider

iTrader: (26)

Thanks guys. Shout out to mrvedit for stickying this.

joecar

Good writeup and it mentions impact on transmission.

summary:
a. any table whose data is derived from mass (e.g. g, g/cyl, g/s, g*K/kPa) or calculated/lookedup from mass (torque, line pressure) has to be scaled (and as you found, idle tables deviate from this for other reasons).
b. any table whose axis is derived/calculated/lookedup from mass has to be shifted down (which turns out to be a non-linear process).

ddnspider

iTrader: (26)

Thanks Joe! Soon as I get to the track, I'll get that Auto tutorial going and message you.

G Atsma

You mentioned Greg Banish in the first post. I have his book and am digesting it as time allows. Not a quick read! lol BUT VERY educational! Anyone looking to get into tuning should read the book titled "Engine Management Advanced Tuning" and is available thru Amazon. It was written 10 yrs ago, but is still quite relevant.

ddnspider

iTrader: (26)

I have the same book. Honestly, his DVD's are what did it for me. I didnt grasp some of the books concepts until I watched the DVD's and then everything clicked.

G Atsma

Hmmm... might check into those! I will look, but are they available thru Amazon? If not, please advise a good source. Thanks in advance!

ddnspider

iTrader: (26)

Search for Greg banish calibrated success. His website has a link to where you can purchase.

G Atsma

Got your PM. Thanks for the heads up!

turbolx

Thanks for the kind words, guys. Hopefully, you'll find that the science doesn't age, so the lessons presented in my books and videos can still be applied today the same as they were when published. It's just the interface (HPT, EFILive) that gets updated and the control system (ECU) that may add an extra layer over and above the basics with time.

Basic MAF calibration is covered in my first "GM Tuning Beginners Guide" DVD. I also did a segment on it in the "Advanced Tuning Series" BLu-Ray too.

Scaling the MAF (and injectors) to deal with the hard coded limits on the older ECUs is covered in my second "GM Tuning Advanced Guide" DVD with a step by step walk through of the process that proves how it really works. Following these instructions will also help prevent some of the common issues with transmission controls that some people have when taking shortcuts on scaling.

I don't sell them directly to end users, but there is a link on my website to our partners at Detroit Technical Media. The discs are also in stock at Summit Racing Equipment as well.