Rocky Mountain Club B5

Discussion Forums => Modifications => Topic started by: Rusty on May 11, 2005, 07:56:08 AM

Title: "Standalone" Fuel Management Install - DynoJet PC
Post by: Rusty on May 11, 2005, 07:56:08 AM
Well, I finally did it and installed the DynoJet PowerCommander PCIIIusb. Complete fuel mapping vs. boost, in 250 RPM increments. For those of you that haven't been following this, it's a "poor man's" way of precisely controlling fuel to our engines.  Many Thanks to Shawn Fogg for his pioneering Internet writeup that got me started.  If any of you are interested in doing this mod, you need to read his writeup:  I read it two years ago, but was young with my car and scared of splicing critical wires.  Two years of fighting my ECU for every last drop of fuel gave me enough courage to finally forge ahead and just DO IT.

Briefly, the PCIII sits between the ECU and the fuel injectors.  The ECU still controls when the injectors fire, but  the PCIII controls how long the injectors fire, on a +/- percentage basis vs. the ECU's fuel pulse.  The PCIII uses the TPS (Throttle Position Sensor) signal to trigger the extra fuel, but I connected a MAP sensor to the PCIII's throttle inputs to get fueling based on boost.  It would not be a good idea to use TPS on our turbo cars - too much variability of boost vs. TPS.  Note that this does NOT constitute MAP-based fueling.  The base fuel pulse is still determined by the ECU as a function of MAF - the PCIII just modifies this pulse based on the additional boost.  The astute reader will instantly realize that this is the only "add-on" way to defeat the 16.32 msec duty-cycle limit on the AEB engine.  Piggy-Back units can't do this, at least not the ones I've researched (SMT, Split-Second).  Chip tuners can't do this, either - the 16.32 ceiling is in ROM where they can't (or won't) get to it.

NOTE: the PCIII requires high-impedance injectors, which all B5's and B5.5's have. If you try this mod on a different car, be sure that your injectors are high-impedance a.k.a. "saturation" injectors, between 12 and 15 Ohms.  Low-impedance a.k.a. "peak-and-hold" injectors will have values around 4 Ohms.

Shawn used some resistors to make sure he didn't throw fuel injector fault codes.  I contacted the mfr, who strongly hinted that with the newer model I was using, I should try it first w/o resistors.  When I first fired it up, I got one "intermittent ground" code on each injector, with no CEL, and after clearing codes, they have not come back.  These codes were no doubt due to initially wiring the PCIII to a "run-only" power source, instead of "run/start."

The total cost was $250 plus shipping and some chump change for things like the rubber firewall grommet.  I got the MAP sensor and Molex connectors as free samples straight from their websites.

Overall schematic:


Here is a full-resolution, full-sized JPEG:
And the original Visio file:

Parts list:

DynoJet PowerCommander III USB model 315-411 (for Suzuki GSXR-1100)
$250 from Illinois Dyno Center

Motorola MAP sensor MPX4250AP
free samples from

Molex connector housing 52213-0311
Molex crimp connectors 50148-8000
free samples from

Rubber Grommet, 3/4" OD,  7/16" ID
NAPA part no. 784632

Assorted wiring, connectors, wiring tools, and wire nuts.  I was lucky that I could borrow the correct Molex crimping tool from work.

For the connectors used in the Barometric Pressure Circuit, see:
Barometric Pressure Mod yields 10% HP/TQ gain ( and Adjust Timing using Barometric Pressure Circuit (

Original PCIII connector, designed to plug-and-play with the Suzuki GSXR wiring harness:


The PCIII after removing the Suzuki connectors and all un-needed wiring:


Here's what I had planned to do - have small Molex connectors on the PCIII and the FI harness, so I could just "plug-and-play" and have it easily removable for troubleshooting or "back-to-stock" purposes.  Great idea except when I got ready to do the FI harness - the wiring gauge was slightly too big for the Molex pins.  Using a bigger connector was not an option for me because it would have required a huge hole in the firewall:


Here's my workspace including the orange-handled Molex crimper.  I was still able to use it because the MAP sensor pins perfectly matched one of the Molex connectors.  You will note AA's writeup on how to add a fused, switched wiring link to your car (Adding fuses to your fusebox and relay plate ( Unfortunately, the terminal 75X used for a power source in that writeup only works in the "RUN" position, and I realized this only after I tried to start it.  I had a few anxious moments and a couple of emails to Shawn until I figured out the issue.  The PCIII needs power during "START", too.  Doh!  He even said so in his writeup.  Doh!  RTFM... :)


The FI harness splice.  You may think I'm nuts to use wirenuts, but I wanted easy uninstall and troubleshooting, and soldered joints don't do that.  I may solder them someday, but not today:


The best location I found for the PCIII was the backside of the ECU inside the ECU's protective box.  You can also see the MAP sensor location in this pic, as well as the infamous BPM (Barometric Pressure Mod).  The BPM gave me pre-made connections for MAP-sensor power and ground.  Without the BPM, you'll have to splice into the BP wires directly - either that or the TPS wiring - the MAP sensor needs a 5V reference and ground.  You can also spot the USB interface cable from the PCIII, which runs through ECU access hole, where it spools nicely under the dash with its little head sticking out the unused rectangular hole behind the OBDII port.  It extends all the way across to the pax seat.  Very nice.


Here are the final views, everything buttoned back up:



The most time-consuming part of this mod was the under-dash wiring, installing Kathy's great mod that I didn't use. Oh, well - I left it in there, maybe I'll use it for a radar detector or something. While I was under the dash, I re-did all the grounds and re-routed and cleaned up my gauge wiring.  Since the power source for my gauges was START/RUN and has proven reliable, I just tapped into it for PCIII power (wirenuts again!). I had wired my gauge ground direct to battery, one common wire wire-nutted to the four ground wires for the gauges - so I just added the PCIII ground to that.  Overall it was pretty simple.

Calibrating the MAP sensor to PCIII throttle position was easy and fun.  The MAP sensor is good to 25-30 psi.  I'll never run more than 20, so that's what I calibrated to.  Set the zero position with car not running - atmospheric.  Disconnect the boost line from the manifold and stick it in a bike pump.  Pump to 20 psi by the boost gauge, set 100% throttle position.  I like this scale because it is easy to correlate to boost, just multiply by two and drop a zero, e.g. 10% TPS = 2 lbs, 40% = 8 lbs, 100% = 20 lbs.

Note that the PCIII power ground is different than the PCIII TPS ground.  Be sure not to get them confused.  The power ground has two silver bars, the sensor ground has one.  Note also that this install did not require any intrusion into the ECU's wiring harness - I really like that. :)

First impressions?  FABULOUS!  I'm already on my second-iteration fuel map.  I'm running stock boost right now, but even at that I was getting double-digit knock retard at WOT.  With the PCIII I've added over 20% fuel to the knock-retarding RPM ranges w/o affecting LTFT (Long Term Fuel Trim).  I plan to completely dial-in the stock-boost fuel map before I put my MBC back in and add extra boost.  This is so Awesome.  I'm so happy - this is much better than the ham-fisted Cartech approach, although the things I learned with the Cartech have enabled me to use the PCIII to full advantage, quickly.

Thank You, Shawn, for your write up, and thank you, DynoJet, for a great and useful product.  :thumbup:  :thumbup:  :salute:

*DISCLAIMER - this post is provided for information only.  Any information used in this post is done at your own risk.  Verify everything before proceeding.  DynoJet does not design the PCIII to be used on automobiles and discourages such use.  Using the PCIII as per this writeup will VOID the PCIII warranty and your car warranty.*
Title: "Standalone" Fuel Management Install - DynoJet PC
Post by: jayryan on May 11, 2005, 10:09:03 AM
Title: "Standalone" Fuel Management Install - DynoJet PC
Post by: tweakeDub on May 11, 2005, 11:47:47 AM
Thank you for the greatly detailed write-up, very informative. I just wish i had the balls to do something like that to my car.  Not only that but I dont think I have the patience for that right now.
Title: "Standalone" Fuel Management Install - DynoJet PC
Post by: Rusty on May 11, 2005, 12:17:25 PM
Quote from: "jayryan"

AHAHAHAHAHARHAR... that's funny! Thanks, JR - look what I did to my avatar! :lol:
Title: "Standalone" Fuel Management Install - DynoJet PC
Post by: ColoradoB5 on May 11, 2005, 09:08:22 PM
Rusty, that avatar is perfect for you!

It sounds like you really need to get into the tuning business as a side job.  With your background, I would think the next step after getting these skills down would be to become your own chip or tuning manufacturer.  

How about being able to hook your car up to a wireless card and you can tune other people's cars over the internet?

You continue to inspire us!  

Title: "Standalone" Fuel Management Install - DynoJet PC
Post by: BHase on May 12, 2005, 09:02:13 PM
Incredible write-up. Makes me want to be creative.

Title: "Standalone" Fuel Management Install - DynoJet PC
Post by: Rusty on May 13, 2005, 07:12:37 AM
Quote from: "ColoradoB5"
...How about being able to hook your car up to a wireless card and you can tune other people's cars over the internet?...
OMG, that's a helluvanidea!

If I were a hacker and could crack the code on these ECU's, I might try the tuning business.
Title: "Standalone" Fuel Management Install - DynoJet PC
Post by: jayryan on May 13, 2005, 08:21:50 AM
I'll pay you to set my car up like you did yours :wink:  :lol: