Stock ECU reprogrammable?

Gigas said:

Perhaps it's a silly question (don't want to be a dick) but what's the reason to get into this trouble if a yosh box, a mak box, a teka or a Power Commander can do the same thing? :O

Click to expand...

Good question.

First the Yoshbox and the Teka were designed to tweak or fine adjust the bike on the assembly line and is very limited in its range. It only adjusts in 3 ranges. Also you can not change the rev limit, remove a top speed restriction or modify the ignition timing using them.

While the power commander (PC) offers more range and resolution it has some problems compared to reflashing the stock ECU.

• The PC is more expensive, especially if you want the ignition advance. You can reflash the ECU with a simple 232 to TTL converter ($20?) and some free software on the 32bit ECUs. The equipment for the 16bit ECUs is about $200
  
• The PC requires a lot of room, hacking up the wire harness etc. Besides what could be more reliable than the stock ECU? Like the Yoshbox you don't need to permanently install anything on the bike
  
• You still can't up the rev limit or remove a speed restriction with a PC.
  
• I don't think all the PCs offers the A/B map feature either. One map for street, one for the track or no-NOS / NOS maps at the flip of a switch.
  
• The PCs screw up the quick throttle enrichment or 'Virtual Accelerator Pump' signals to the injectors.
  
• The PCs do not allow you to change the timing or fuel by gear position.
  
• The PCs do not have individual maps for each cylinder.
  
• The PCs don't adjust for Volumetric Efficiency (VE)

I think the last one is worth explaining even if it gets a little technical...

The ECU basically calculates how much fuel is injected into the engine to maintain the desired air fuel ratio. In order to know how much fuel it needs to know how much air mass is flowing thru the engine. There are two ways to do this. One is measure it with a Mass Air Flow (MAF) sensor that physically measure the actual amount of air or calculate it using Manifold Absolute Pressure (MAP). The Denso system uses MAP

The way MAP works is they take the prototype engine, stick it on a test stand and measure how much air flows thru it at different manifold pressures, RPMs, and throttle settings. This flow map is the Volumetric Efficiency Map. Its a measure of how well the air flows under different conditions. An engine with no head on it basically has 100% efficiency. As fast as the piston goes down it fills up with air. Stick a head on it and make if flow thru valves and it obviously restricts the air flow. The design of the intake tract, Ram Air, how well the exhaust pipe scavenges, etc all effect the VE and effect it differently at different RPMs.

So guess what happens when you put an after market pipe, filters, and velocity stacks or port your head? Yes, you improve the VE but now the bikes actual VE profile no longer matches what the ECU thinks the VE should be.

Well thats what the Power Commander is for right? Well the PC maps are RPM vs Throttle and the problem is the Air mass flow is not going to be the same in 1st gear going 30mph as it is at the same RPM and throttle in a higher gear with 100mph+ of Ram Air. I think the best example of this is the Muzzy pipe problem well known on ZX-12s. The pipe has a stumble at low rpm that people find hard to adjust out with the PC.

Here is the VE map of the 12, rpm on the left, manifold absolute pressure across the top.



I've enhanced the boundary around 60 and you can see the peaks and valleys of flow as the resonance of the intake tract, exhaust and cams go in and out of phase. But for the most part if the map peaks at high pressure (right side) then it is also higher than average in the mid and low pressure (left side of map)

Look at 5000 rpm; Higher than average left, middle and right. But now look at 2000 rpm; very low flow left, average mid and peaking right. This means the stock engine configuration flowed very poorly at low MAP, at 2000 but flowed above average at higher MAP. I believe putting the Muzzy pipe on the bike fixes that dip in the map. But the ECU doesn't know that so it still runs the bike very lean at low MAP and richer than average at higher MAP at 2000 rpm.

So how do you fix that with a PC? You can richen up at low map but then it will be too rich up high or vice versa so you compromise. Something you don't have to do with reflashing the ECU.

You obviously know a whole lot more about this than I do, but I'll make an ass of myself anyway

If the stock un-modded ECU can't cope with changes to the machinery that affect the A/F ratio (ie. it's an Open Loop EFI IIUC), then how will a mapped one be any different to just adding a PC and .djm? Stock ECU is only adjusting the fuelling based on the input from more sensors, or so it seems. At least, that's how I understand it :O

Also, gotta add a few corrections for the sake of accuracy ...

• The PC requires a lot of room, hacking up the wire harness etc. Besides what could be more reliable than the stock ECU? Like the Yoshbox you don't need to permanently install anything on the bike

What else you gonna do with the space in the seat hump? Smuggle Asian families across the border? :laugh

• You still can't up the rev limit or remove a speed restriction with a PC.

Yes, you can. Ignition module & the extra downloadable software for those models that have one.

• I don't think all the PCs offers the A/B map feature either. One map for street, one for the track or no-NOS / NOS maps at the flip of a switch.

Yes, but you have to buy the $150 or so Multi-function hub that comes with a toggle switch for the bars. Or buy the LCD display for a few dollars more and have as many maps as your SD card allows. Let's see, at 5kb a map on a 512Mb SD card thats ... lots Also, the MFhub allows outputs and inputs for controlling NOS, shift lights etc :yes

• The PCs screw up the quick throttle enrichment or 'Virtual Accelerator Pump' signals to the injectors.

You don't have to install that software and can turn it off if you do.

• The PCs do not allow you to change the timing or fuel by gear position.

Yes, but again you need the multi-function hub, LCD display or another bit of hardware which was all getting too serious for me so I ignored it

• The PCs do not have individual maps for each cylinder.

PCIIIusb does :yes

Sure the PC isn't the ultimate or perfect solution, but for 90% of riders it's got to be good enough. Not saying I'm not interested in learning more or aren't interested in a fully tweakable solution though :devious