Topic: 2 BAR SD Tune w/ HP Tuners

[FlaBouy]

 Well ladies and germs... I have finally given in.... After 19 months of blissful forced induction, I have given in to the apparent need to throw away my MAF. Since about mid fall last year, I started logging airflow in excess of 1000 cfm through the beast. A stock MAF is capable of reading about 62 lbs/hr of airflow which translates to about 12,000 HZ to the PCM. The MAF failsafe is set to 12,500 hz so if the freq range exceeds that value, the PCM assumes the MAF is broke, sets a SES light, and reverts to the VE table only for fueling.

What does all this mean? Well, when you consider the fueling at WOT utilizes the MAF only to provide a reference to the injectors for bulk fuel, and the narrow band o2's have been turned off when you entered PE, it might be safe to say that you have a problem.

My truck has been logging 12,296 HZ and 63.55 lb/hr at a limited 5800 rpm for a while. This means the MAF has been exceeded and I have had to carefully watch my fueling up top. To be safe, I have tuned to the rich side under PE. To give you reference, a stock truck at WOT is only drawing 35 lb/hr or roughly 400 cfm.......

So, I have in front of me the beginning of the future for my truck. It is a 2 BAR speed density tune. It allows me to throw away my MAF and rely on the VE table for fueling. This is how EFI was run prior to the invention of the MAF, and surprisingly, according to Allen Nelson and others, the truck runs much more smoothly with the speed density tune.

Let's look at why I need the airflow. Boost, pure and simple... A NA truck runs in vacuum from about -20" of HG to 0" at WOT. Simply put, 0" Hg is atmosphere, so when you are running WOT without other means of forcing air into the cylinder, you run at atmosphere...technically.... There are some motors that will actually build a # or so of boost through backpressure and cam lift/timing, but for the most part, it is atmosphere.....

Now for the math... 1 pound of boost is equal to 6.8 kPA. Vacuum on the truck is measured from 0 kPA to 103 kPA, with 103 kPA being atmosphere. So when you add boost, you add 6.8 kPA to 103 kPA(atmosphere) for every pound of boost. This is measured by your MAP sensor located at the back of your intake manifold on the drivers side.

Now, my truck has a 2 BAR MAP wired in tandem with the stock MAP but it inputs to my HPT software not the PCM. The PCM still reads the stock MAP. I have registered 195 kPA through HP Tuners from the 2 BAR MAP; which, if we do the math, is 13.5 pounds of boost. I log both the stock MAP and the 2 BAR MAP in HP Tuners to check both the linear calibration of the 2 BAR with the stock 1 BAR MAP and the scaling to make sure in vacuum they both read the same. This is important since this Saturday I throw the MAF and the stock 1 BAR MAP away and start inputting the 2 BAR into the PCM directly.

For those still awake, this is the part where it starts getting fun. I had to do the 2 BAR 101 course for those that needed a little background before I jumped into the heavy duty tuning.

[KY_BOB]

Interesting read.  I'm looking forward to hearing how long it takes to get the 2BAR VE table in good shape.  I don't know where you would even start.  I'm also interested in seeing how much the fuel trims change with weather changes.

Good luck.

[FlaBouy]

OK, now that the basics are documented... what is a 2 BAR SD OS. Well, simply put, it is a complete rewrite of the PCM, sort of a hard drive reformat for those geeks out there.... :-*

The new OS basically extends the VE table of a stock OS from the standard 0-105 kPA range to a new 0-210 kPA table. This allows VE values to be tuned not only in vacuum, but now in boost regions up to 15# boost. A 3 BAR extends this range even further for those twin turbo freaks out there that want to build 25-30# of boost....

Power Enrichment is also recalibrated to the MAP instead of the MAF so now your WOT fueling reference is MAP input not MAF input. For those of you that are still with me, and have HP Tuners, if you go to Fuel Control->Power Enrichment, the EQ Ratio vs. RPM is now changed to reflect 14.7 AFR  for vacuum... this table will handle everything below the PE threshold you have set.
There is now a Boost enrichment table under the PE tab and it's name is EQ Ratio vs. MAP. This table handle fueling through the boosted regions and can be scaled to hit any commanded AFR you choose as boost builds. It allows 5 kPA resolution from 100 kPA through 210 kPA......

Change the Enrichment rate from 1 to 4 and you have a basic 2 bar tune.....

Copy your VE table over, extend the parameters up to 210 KPA, and rewrite the PCM..... then you go about recalibrating the VE table just like we did previously.... except now you can calibrate VE table all the way through 210 kPA.

Did I mention you get Real Time Tuning for free with 2 BAR OS? Yep... make changes on the fly... no need to log, then retune, then relog, then retune..... :thumb:

So how many are still with me... raise your hands...........

[FlaBouy]

BTW... for those that wonder about benefits of 2 BAR tuning....

Allen has taken a stock Avalanche, with 5 psi of boost and a small cam, to 13 seconds in the quarter mile, and driven home at 20 MPG.... :thumb:

[FlaBouy]

 I'm also interested in seeing how much the fuel trims change with weather changes.

No more than the stock tune...... where you were relying on VE table and MAF input down low referenced against the stock MAP; and MAF only up top under WOT, the 2 BAR is using the VE Table only referenced against the 2 BAR MAP in both vacuum and boost.

Soundengineer (HPT forum user) has indicated his 2 bar is showing less than 1-2% impact due to weather changes. Most everyone that has went 2 BAR indicate the truck performs more consistently and with less surging/idle issue than the stock tune...

Just takes time to get there.... but at this junction, I believe I have enough face time with HPT to minimze that impact.... I hope...

[FlaBouy]

My very rich guinea pig.....

[FlaBouy]

Well boys and girls..... It is done.....

2 BAR SD OS is installed and running like a clock.... Say bye, bye, MAF...... :)

Looks like I spend tomorrow dialing this puppy in............. then we can see what this thing can really do.....

[FlaBouy]

  SMOKIN!!!!!! 

2 BAR is dialed in... made a pretty hard run from idle to WOT. Trims are dead nuts, and the wideband logged AFR within .2 of commanded AFR through the pull. Pull made in 80* weather and zero KR across the board at 22* timing up top. Now for the hard part... Waiting for my intercooling means to arrive so I can start throwing some timing at the beast......

Dialed this puppy in within 4 passes after installing baseline (rich) 2 BAR OS...... I recommend this for anyone running above 10psi. The tuning was a piece of cake...Now I plan on sitting back and logging for a few days to watch fueling.

Bye, Bye, MAF.... 8)

[bluedevil]

You know?   I'd like to learn "the how to" using hpt. I just hate the thought of draggin my laptop,extension cord,hpt cord outside everytime i want to log.  

[bluedevil]

My very rich guinea pig.....

looking at the image...i have no clue what im looking at

[KY_BOB]

My very rich guinea pig.....

looking at the image...i have no clue what im looking at

That would be a VE (volumetric efficiency) table.   ;)

[FlaBouy]

I just hate the thought of draggin my laptop,extension cord,hpt cord outside everytime i want to log.  

You don't have too...... :thumb:

[KY_BOB]

I just hate the thought of draggin my laptop,extension cord,hpt cord outside everytime i want to log.  

You don't have too...... :thumb:

Not if you get the Pro version. ;)


I have to, I have the std. version  :-\

[FlaBouy]

Update......

Not quite sure why I have not got around to doing this before. Truck runs so smooth now compared to being on the MAF. I installed the intercooler this week end and played around with the tune a bit. Fueling under WOT is so much more precise. I can basically hold AFR down to a tenth of an AFR point. I can also tune the VE and Boost PE to within a tenth of any AFR anywhere in the rpm range and hold it dead nuts. I have found that IAT temps play a fairly large role in fuel trim repeatability from day to day. Hell, the difference between cold start and heat soak has been over 15% on the same day.

The aftercooler has stabilized IAT's, even with the teacup Vortech sent for a charge canister. That will get changed out shortly. I plan on adding a large storage tank in it's place so I can add Ice when I want. Aftercooler install went fine. Couple of small deviations from the instructions I downloaded for a Hummer..... :)  Seems Vortech does not have instructions for adding the aftercooler to an Avalanche since we obviously have no need for more than 6 psi of boost...

Anywho, I love the new 2 BAR OS. Easy to tune. Smooth transistions through the RPM range. No nonsense at idle. Screenshot from my log this morning. Details show the following:

Frame 6500... start of pull... From 800 rpm idle.......

Speed/MPH              Timer              Result/Seconds
 
   0                      11:00.860
  60                      11:06.000                5.14
 100                     11:12.907               12.05
 105                     11:14.141               13.28

Looks like the truck has .3 tenths reaction from throwing the hammer 


AFR was nailed at 11.3 on a commanded 11.28 AFR. Timing was 22*... I have been running 25* timing the last few days, but I pulled a few degrees to finish tuning against the aftercooler. Zero KR through this pull so it looks good that I might be able to add it back in a week or so......

Finally, looks like I lost 1 psi of boost through the aftercooler. Not a problem though. As tight as this tune is, I might spin the motor another 200 rpm up top, or at some point try a shot of the funny gas to compensate....


Next stop.... 4L65E.... FLT is building it as we speak.........

For all you HPT users, that log is available on request.....

[FlaBouy]

Testing....

http://good-times.webshots.com/slideshow/558718396zMByDq