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MG MGB GT V8 Factory Originals Technical - Road Test

Got the car out today for a few short trips, and to see what my tuning efforts have accomplished. For those not familiar with this project, it's an Olds 215 in a '71 roadster, but a bit of a special project since it has an Eaton blower and a Ford EEC-IV SEFI system along with the EDIS distributorless ignition. I'd been having driveability issues and TwEECer support for my PCM was slow to develop, so I bought a '95 Mustang PCM, swapped that in which proved to be pretty much a drop in swap, ran a datalog of the system and determined that the MAF (airflow meter) was bad. Traded that back to the junkyard for a good one, proceeded to clear up the error codes and tidy up the wiring a bit by getting rid of an extra temporary harness I had rigged to kill the transmission codes, as well as add some diodes to the dimmer circuit for my light and heater switches, and then since it was a nice day I got out and played a bit.

The car absolutely runs like a scalded dog. In the lower three it'll go sideways with very little excuse, and in the upper two it's so quick that I was probably never in to the gas all the way for more than a second or so. Man, I was lovin it! That's a fair bit more power than my hot Buick with a lumpy idle. Granted there are still some driveability issues. I get a bit of a surge in the midrange, it feels rich down low, and I have a radiator fan that the PCM would like to run all the time, but those are pretty minor things compared to what has come before. The main thing is that I can now get it out and play with it. Stopped at the gas station and filled up with premium, gonna have a little fun! Yeah!

Oh, I guess I should go ahead and finish hooking up the lights. Maybe it's a good thing they're predicting snow!

Jim
Jim Blackwood

Sounds like fun!
I'll take a ride!!!
Going tech over CI. I like it. soundslike you have really put the effort into this one. What kind of software are you using to work with that system? Since its a 95 PCM, I assume its still OBD I compatable and if so, how much reprogramming did you do to it to fit the supercharger?

-BMC.
BMC Brian McCullough

There's an add on module called the TwEECer ( tweecer.com ) that plugs into the J3 diagnostic port on the processor. It has proprietary software that allows modification of the ROM settings, direct connection to a computer via USB, and provides a way to create a data log as the vehicle is running which can be evaluated later. The module also comes with a 5 position switch which gives you 4 custom tunes that can be loaded into the module and you can switch between them on the fly. Provided you have a supported processor, (Mustang primarily) you can use a GUI interface to set a wide range of functions, scalers and tables to control the processor's operation, and recall, Ford calls this a Powertrain Control Module. As such it can control far more than just the fuel injection. Set points for turning on and off a high speed and a low speed radiator fan are an example. You can control the MAF transfer function, injector slope both high and low, rev limits, vehicle speed limits, (for valet or the kid) timing advance and retard under a wide variety of conditions, accelerator pump functions and dashpot, monitor engine parameters live, such as RPM, vehicle speed, throttle opening, airflow, HEGO, load factor, engine temp, inlet temp, open/closed loop operation, timing, and so many other things I can't begin to list them.

My modifications so far have been pretty minimal:
Tweecer Switch Position 1 ('95 Mustang GT PCM: T4M0)

EGR=2 (none)
Thermactor=0 (not present-turns off secondary air injection)
Fan temps lowered
CID=215
Cylinder ID=1 (sensor for #1 TDC. Some engines such as 5.0 don't have one)
MAFv max=4.9999 (Max recognized output voltage from the MAF)
Rev limits: 7000-->6000
Checksum Base Address =0 (Eliminates ROM error code caused by connection to J3 port)
Fan Low Speed Enabled=0 , 116 error code (This is something I'm working on. Could be a problem with the PCM)
Fuel OL time delay multiplier: 38-->0 (Eliminates lean spike on acceleration)
Fuel decel cutoff time extended: 6-->0 (Gives better response to closing the throttle)

I have another tune to try as soon as the weather clears:

Tweecer Switch Position 3

EGR=2
Thermactor=0
Fan temps lowered
CID=215
Cylinder ID=1
MAFv max=4.9999
Rev limits: 7000-->6000
Checksum Base Address =0
Fan Low Speed Enabled=0 , 116 error code
Fuel OL time delay multiplier: 38-->0
Fuel decel cutoff time extended: 6-->0
L2W MAF Transfer curve (This applies the MAF transfer curve from the processor that went with my system hardware, giving a leaner bottom end and a richer top end)

For position 2 I have a slightly modified tune for a J4J1 processor (Cobra) which is interchangeable.

Additionally, the system is adaptive. In closed loop mode it will correct for non-stoiciometric air/fuel mix up to about 20% of the base tune. This can also be turned off if desired, or the definition of stoich can be changed for greater economy, (the computer doesn't know the difference) with the limits for switching to Open Loop set so that any significant acceleration allows a richer mixture. A knock sensor can be integrated as well, and the parameters modified.

For the blower, A/F ratio can be enriched under boost conditions, and timing can be advanced, then retarded, then advanced again as you go up the rpm range, and advance can be tied to load, engine temp, inlet temp, barometric pressure, knock sensor, etc. (On some processors they even cycle the timing advance to control idle speed. Apparently mine is one of those.)

As a little side benefit, I also got the electronic cruise control. Ford does make one of the best. That's to help avoid tickets on those long drives.

Jim
Jim Blackwood

Jim,

How did you get the supercharger to fit under the bonnet? Where did you mount it? Sounds interesting. And very quick!

Frank
Frank de Groot

Umm, Jim's supercharger doesn't quite fit under the bonnet ...
Ted

No, not quite. I'll send you a jpg Frank.
Jim Blackwood

Sounds great Jim,
I have been digging deep on altering our PCMs as well for the 3.4L SFI, but there is far more support for V8s, unless going aftermarket. The thought of supercharging does linger on our side too. :-) The carbed and TBI versions of our motors are already there, but I want to see it for SFI/MPFI as well...
I would love to see some pics of this!
thank you,
-BMC.
BMC Brian McCullough

Jim congrats!!!

I was just going to mention to you, that these ECU's ARE fairly adaptive. I have a fairly "radical" cam in my new motor, and the people I have spoken with have stated that it will run poorly till I get a few long highway cruises under it's belt.

I heard good things about Tweecer, sounds like you are having fun!!!
Larry Embrey

This thread was discussed between 10/02/2003 and 12/02/2003

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