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Old December 20th, 2011, 10:25 AM   #37
hoo dat. wat.
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Join Date: 11-09-05
Location: Howell
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So, I saw Derek's post in general tech about what heads and cam would be good for a TBI motor - said he had it at a garage and they told him he needed to change those two things before it would ever run right. I think it's the same folk that sold him that janked D60...

Somehow, I talked Derek into bringing this down to me to fix, so I've had it for - what- damn-near a month now (damn day job!). So here's a rundown of the problems he had & why it wouldn't run:

1. Someone sold him a TBI computer for a 350; in reality, it was for a 4.3L V6...
2. Repair shop never adjusted the throttle setscrew & TPS voltage correctly;
3. Someone forgot to hook up a stray vacuum line...
4. The cam is inappropriate for a stock TBI computer;
5. Derek has some bad mf'in luck sometimes.

After getting the right base calibration for his computer, I set to changing the VE tables for fuel. This thing has a lumpy cam in it - nothing serious as far as duration and lift, but the lobe separation angle is somewhere around 105 degrees. Lots and lots of valve overlap to mess with the MAP signal -AND- there's so much internal EGR from the narrow LSA, the damn thing just plain don't like to idle for the TBI setup.
Nobody knew the specifics, so I threw a dial indicator on the rocker arms and figured out the cam's basics.

I got most of it straightened out, but the (old) age of the computer didn't let me read the ECU data fast enough (one sample, roughly every 2 seconds SUCKS!). I grabbed a newer computer, disassembled an old unit for the sockets - and built a translation harness so I could hook up the newer computer to the older harness. The newer computer uses better software and has a much higher bus speed - it lets me take data at 10hz.

Now, here's where the problems began.
I'm using a hardware setup that lets me emulate the calibrations on the processor and make real-time calibration changes. Well, turns out, mine slowly died in the process of converting over to the new computer, so I spent a week diagnosing problems that don't exist. I'm waiting to send it back for repair, but for now, it's the only way I can take data & post-process it. From there, I burn the new calibration to a chip and got back outside and test. Having the emulator malfunctioning creates about 10x the work needed just to get a functioning calibration.

Anyway, I'm back out in the truck and calibrating daily after work and getting it zeroed in - biggest hurdle left is to pull all of the wires out of his harness connectors and repin them to the connectors in the new ECU. LOL - it wouldn't be so bad, except this damn Jimmy is TALL! I have a permanent bruise on the back of my left leg from hopping in and out.

Things look well for being done by Friday - just remember - I want to get back out in it at the mounds or somewhere offroad so I can verify everything runs as it should.
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