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‘05 749R, ‘89 851/926, 749R/999RS project
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435 Posts
Discussion Starter · #1 · (Edited)
So I've got my 851/926 race project up and running and sorted the Power Commander missing part/wiring issue I had here: http://www.ducati.ms/forums/56-superbikes/701658-pciii-info-part-required-851-926-racer.html

I've just a few little things to tidy up while I've got it apart to install the PClll USB and head for the dyno session booked for Thursday.

The Corsa-style 1 piece air-box may be good in the long term but right now it is an absolute ball-ache: to get at the injector wiring I've basically got to pull the front engine mount bolt and swivel the engine down to squeeeeeze it out over the TB's, all the while bending, flexing,wriggling, shuffling and holding your tongue just right while turning the air blue with all manner of cursing.

Then it's time to run the wiring, and shuffle, squeeze, flex and swear the air-box back into position, once in place jack the engine back up which pivots the engine back juuuuuust enough room to clear the throttle body indent in the base of the airbox and plug in the rear injector. Just painful.....but it's done, and once installed looks like this:



I've been wondering about filtration for the ol' girl and eventually came up with this in time for the dyno tune:



So all good, with PClll installed just above the battery, with a Shorai LiPo giving a bit more room.

All good that is, until I go to fire it up: no go, not even the slightest cough, with no lights showing on the PC. Awww shit! A bit of fault finding later and I can't see any option but to start from scratch and reverse the process as it hasn't been run for a month or so, and I've changed eprom's while I waited on the PC and went away for work. So I pull it apart again, unplug the PC and reinstate the original basic wiring....

....only to finally press the button and hear the flat drone of it only firing on one cylinder. Sure enough the rear pipe is cold. Check for spark and all is good, so out comes the P8 ECU to replace the original eprom (why oh why don't they position the ECU so the eprom is on top rather than underneath?!).......only to hear the exact same thing. WTF? With spark confirmed I started looking at the fuel system, swapping injectors to no avail, then swapping out the ECU for the old P7. Still no good. Injectors good, spark good, ECU good...there must be a break in the wiring loom......and sure enough cunningly hidden under the boot of the injector plug:





Cee U Next Tuesday!!! But at least I've found it. It's another PIA sorting the plug terminal with 50 year old eyes but eventually I make everything workable, without the airbox in-situ, and it fires up nicely, sounding even better now thanks to Brad's suggestion of bumping up the fuel pressure. It used to occasionally give a "too lean" spit back into the airbox but that seems gone, and it just sounds that little bit "fatter".

So after a full day of arsing about I'm worse off than when I started, bike in bits and no PC installed, but at least I've established the basics before I have another crack at the PC. Time for a well earned reward for accomplishing so little:



Now this is where my head goes into meltdown: for the life of me I can't get the PC to power up without the external battery supply connected. The external 9v battery connection is only to enable map installation or interrogation without the bike running, or unit disconnected from a bike. But if I wire the PC as per normal it will not power up. So I have the PC plugged into the injector wiring, earth earthed, and I've tried the grey wire which supposedly goes to the TPS directly into the TPS plug (disconnected from the TPS) and also direct to 12v but it's just dead in the water.

I have 2 functioning PClll's (1098R and 998 units) and neither will fire up....unless the external battery is connected.

Can anyone give me any idea what I'm missing? I've absolutely run out of ideas (and worse nearly run out of beer!).

So this is where I now stand:



And with all the tank on-off-on-off-on-off-on-off- malarkey one of the fuel quick connectors is now leaking so I'm sorely tempted to use the leak to my advantage and just throw a match at the thing!

EDIT 1: I know of another 851/888 with a 998 PClll installed so the PC type should not be an issue.

EDIT 2: I'm thinking I need to plug in the TPS and splice into the variable wire but I can't see how this would actually stop it firing up as even with 12v on this lead it doesn't come to life.
 

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Mayor of Simpleton
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4,882 Posts
Where did you get your 1 piece airbox? Mine (Sebimoto) isn't tough to swap in/out.

Btw, I'm starting a new 888 project. Probably ST4 cases and 955 kit to remain NG1 legal. ST throttle bodies since shower injectors aren't allowed, and a modified 1198 harness to use a quickshifter and the 5.9 ECU and avoid all the tuning nightmares.
 

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Registered
‘05 749R, ‘89 851/926, 749R/999RS project
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435 Posts
Discussion Starter · #3 ·
Where did you get your 1 piece airbox? Mine (Sebimoto) isn't tough to swap in/out.

Btw, I'm starting a new 888 project. Probably ST4 cases and 955 kit to remain NG1 legal. ST throttle bodies since shower injectors aren't allowed, and a modified 1198 harness to use a quickshifter and the 5.9 ECU and avoid all the tuning nightmares.
My airbox is from Oronero. He did me a great price on the airbox and intake bits and bobs as they aren't quite show-bike perfect but still well good enough for a race bike that will inevitably get knocked about. Plus the old bikes from back in the day were a bit rough around the edges so I figure they are period correct, lol.

I'll have to have a look at the ST throttle body arrangement compared to the 851. Squeezing the airbox over the top of the 851 throttle body/fuel pressure regulator pipes and hoses and still getting through the steering head framework is the tricky part, and then the front cylinder injector plug is jammed right up against the base of the airbox.

Your new project sounds good, something more to be insanely jealous of!
 

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‘05 749R, ‘89 851/926, 749R/999RS project
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435 Posts
Discussion Starter · #4 ·
Hindsight is a terrible thing

Aaaaargh! Why are things always so crystal clear in hindsight?

I initially thought the "stray" wire to the TPS was simply using the TPS as a convenient place to pick up a 12v power supply to power the PC. But even a direct connection wouldn't power up the PC. Then I measured a permanent 12v supply at the injector plugs and realised the PC was powered from the injector plugs, with the ECU switching the injector circuits to ground to fire the injectors. But it still wouldn't power up.....

......so why did it take me so long to take one itty bitty step and confirm the polarity of the injector plugs vs the PC plugs?

Yep, somewhere along the way Ducati have reversed the polarity of the injector plug wiring. Simply swap the orientation of the wires in the PC plugs that connect to the original injector plugs and there you have it.

I should be well used to it after all these years but sometimes my stupidity even amazes me....
 

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Mayor of Simpleton
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4,882 Posts
Your new project sounds good, something more to be insanely jealous of!

The hope is that this one won't spiral out of control, but we'll see what really happens.
 
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