ridgeracer
Pro
Posts: 1309
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posted July 26, 2008 07:18 AM
 Edited By: ridgeracer on 26 Jul 2008 08:23
"Yoshbox" for the ZX-12
Way back in Nov 2006 when I was trying to figure out how to reflash the stock ECUs (see here) I first investigated the 8 pin connector under the seat because on the shop manual schematic the lines were labeled "Input to Memory". It turned out that this plug is actually the factory fuel trim plug used at the factory to balance the cylinders and tweak the motor. You see every ECU is made exactly the same. The motors on the other hands are all slightly different due to the manufacturing tolerances of all the component parts.
These trim ports are available on most Denso ECU equipped sportbikes including the Suzukis. Yoshimura offers a box called the YAFMS commonly known as the 'Yoshbox' that lets you use this port to make fuel adjustments to the Suzukis. This is also the same port the TEKA uses.
When I finally did get the software out of the ZX-12 I looked up what the ECU expects from this port and how it works. The principle is the same as the Suzukis but the values are slightly different meaning a Yoshbox would not work on a ZX-12. Using that information I found I designed my own version of a Yoshbox for the ZX-12.
Schematic
I call it the MAD for Mixture adjustment Device. And I built one
Before I could test it I needed to find the matching plug for the one on the wire harness. I could have spliced it in but I didn't have my 12 anymore and was going to need a volunteer to test it and figured I wanted to make it as painless and error proof as possible.
That was a year and a half ago.
Since then I've found the plugs and built an engine simulator that allows me to bench run the ECUs. Some one asked me about the MAD so I dug it out to see what it would do. I bench tested the MAD and it works.
To review there is an enable or ON switch. a mixture setting, a cylinder select, a range, and a WRITE button.
I plug the box into the 'Yoshplug' and started up the ECU with a digital storage scope showing the injectors. The cylinder select worked as expected. Select cylinder 1 on the box and only the cylinder 1 injector is changed.
For the mixture I selected a very accurate 100 step potentiometer that would give me very repeatable 0.05V changes per step or 1% of 5V per step. The code shows valid mixture values are from 90% to 10% and I found my mixture worked from an indicated 90 to 11. 10 was right on the edge and the value would jump back and forth. The way it is setup 50% or 2.5V is 0 change so the working range of the mixture value is +40 to -40.
With the MAD plugged in and the ECU running I set the Mixture to 50 and turned the box ON (COS1 to ground) Nothing happened, as expected. As I increased the Mixture above 50 the injector pulse increased, below 50 it decreased. If you exceeded the max of 90 or the min of 11 it jumps back to no change. If you turn off the box the pulse returns to normal.
If you change cylinders from 1 to 2 while the box is ON, cylinder 1 returns to normal and cylinder 2 shows the change.
If you press the WRITE button (COS2 to ground) momentarily it saves the change. Turn the box off and the change persists, turn off and on the ECU and the change is still there.
After recording a bunch of data points at various throttle, RPM, and injector dwell values I figured out the following. A 5% change in mixture voltage results in a 1% change of injector duration.
Mix Percent change
90 +8%
80 +6%
70 +4%
60 +2%
50 0%
40 -2%
30 -4%
20 -6%
11 -8%
RANGE:
At first I thought the range didn't work. I started out with a setting of C which is LOW and found the you could only change the Mix between 600 and 4000 rpm as expected. But when I went to a setting of B or MED I could change nothing at any RPM or Throttle. Same with A or HIGH.
At first I checked the box but then I remembered this was all based off of reading model B1/B2 code and I was bench testing an A1 model ECU. I checked the A1 code and sure enough it only has the one range available. So for the record:
A1 21175-1069
Range LOW (COV3 = C or 2.00Volts) 600
B1/B2 21175-1089
Range
LOW (COV3= C or 2.00Volts) 600
MED (COV3= B or 1.35Volts) 4000
HIGH(COV3= A or 0.63Volts) 8000
Now outside those zones there is no change.
Also the change is to the final calculated fuel value regardless of whether its Alpha-n or Speed Density based. Warm-up enrichment, whatever.
What about D, E, and F?
I had found earlier that C and D were both LOW, B and E were MED and A and F were HIGH. So why the duplicate values?
Well these ECUs have duplicate sets of ignition and fuel maps that are jumper selectable from the wire harness. The wire that selects it is COV3, the same wire used to adjust the throttle/RPM range. Below half or 2.5V COV3 causes the ECU to use one set of maps. Above 2.5V the other set. What is going on is that settings A B C are all below 2.5V and D E F are all above.
Which group you use determines which set of maps your adjusting against. Let me be clear on this though. There is only one set of adjustment values. You may be able to pick which map set the ECU is running when you adjust it but there is not one set of adjustments for each map set.
One last thing. The amount of adjustment is a map value, one for each cylinder. Instead of +8 to -8% you could make it +20 to -20%. Of course to do that you have to cut open the ECU and reflash it in which case why not just make the changes in the real fuel maps.
On the other hand it might be nice to reflash your maps on the dyno but still have some adjustability at the track. You could also change what the zone boundaries were too.
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ZXLNT
Needs a job
Kawpuke Extraordinare
Posts: 2853
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posted July 26, 2008 11:09 AM
Way cool..
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entropy
Moderator
Posts: 8671
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posted July 26, 2008 07:58 PM
Ridgeracer,
You are in an orbit sooooooooooooooooooo far removed for my shade tree mechanic mindset, i am dumbfounded.
How in the world you do this stuff is beyond me.
i wish you lived in Houston.
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This moderator uses moderation in moderation
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VincentHill
Needs a life
Posts: 6520
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posted July 27, 2008 05:29 AM
quote:
Ridgeracer,
You are in an orbit sooooooooooooooooooo far removed for my shade tree mechanic mindset, i am dumbfounded.
How in the world you do this stuff is beyond me.
i wish you lived in Houston.
Karl, I am totally with you! How anyone can figure their Mind toknow and understand this and even make Sense to us us is beyond me!
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Made History @ Daytona and still one fast old man!!
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kaw12
Expert Class
Posts: 172
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posted July 27, 2008 06:46 AM
so is this thing like way better than a pc? other than just not having to leave it hooked to the bike? more fine tune ajustments? or is it just basically like a pc? sorry not much info on the YAFMS in google just seeing if these two units do the exact same thing!
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2000redrocket
Pro
Posts: 1662
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posted July 27, 2008 09:28 AM
this sucks my A1 only does low rpm. ohwell.
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ridgeracer
Pro
Posts: 1309
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posted July 27, 2008 12:31 PM
quote:
so is this thing like way better than a pc? other than just not having to leave it hooked to the bike? more fine tune ajustments? or is it just basically like a pc? sorry not much info on the YAFMS in google just seeing if these two units do the exact same thing!
You can read up on the TEKA which is a 'smart' version of the same thing...
http://www.factorypro.com/TEKA_SFI/TEKA_SFI_suzuki%20fi,%20fuel%20injection,ECU.html
From what I've heard on using these is that if your just adding an aftermarket street pipe and you want to make it run a little smoother and richen it up a bit they work well. But if your thinking about a big bore kit, cams, stacks or any of that kind of stuff you will still need the PCIII.
It only adds +8% after all.
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