QR25DE Tuning

[jaf]

Hi All,

Anyone interested in tuning the QR25DE ecu?
This is not a "How To Flash your ECU" and I won't be drawn into explaining that but I am happy to share what I have learnt so far about how this engine responds to tuning.
I have an 05 X-Trail that had some annoyances like a dead-spot off the mark, over-richening when cold, over-richening when WOT plus a few others.
Looking around on the internet, there is a lot of talk about how the Consult II Nissan ECUs are almost impossible to tune so I took that as a challenge since I intended to keep the car for a little while longer.
To cut a long story short, my X-Trail is now doing 8.2l/100km without economy driving and is a bit more fun to drive. All on a very safe tune as this is my daily driver.
I will post the original ROM if Tom can tell me how to attach a file larger than 200K?
For now, here is a pic of the type of ECU (which is used across many models 04 -07) and another pic of what it took to make it flashable (sorry about pic quality).
Will update with a few maps etc. shortly.

Edit: ROM uploaded

[jaf]

The stock tune....

Note: the cam map is actually only an 8x8 map. This is "interpolated" into the 16x16 maps shown for clarity and to make comparison with other maps easier.

Stock intake cam advance map shows that from 04 onwards, the QR25DE gets a 40 degree VVT sprocket as opposed to earlier years 30 degrees.
Max power is generated at no more than 27.5 degrees advance but........
Advancing beyond this value creates an EGR situation - exhaust gas pulled back into the cylinder for another burn. This extra advance also lowers dynamic compression hence reducing pumping losses. The cam will shed this extra advance if power is demanded or the load is too light.
Now look at the NDSII log pic...... there is 5 degrees worth of hunting on the (grey) cam advance trace. This is normal stock behaviour!
Under light cruise conditions, this hunting can be felt if the cam is dropping in and out of optimum advance so the advance is kept slightly higher than necessary to hide this effect.

[jaf]

So onto the tuned map....
Be warned - Any change to the cam timing has a large impact on fuel and ignition timing requirements.
What's different?
Advance starts climbing from a lighter load point across the rpm range - better light throttle response.
Over-advance (EGR) reduced to just enough to cruise smoothly.
Advance fall off at high load reduced - stays in peak power range.
Advance extended into higher rpm range - Ahh! that's where Nissan hides all the power!!!

[jaf]

And here is what the original and modified cam maps values look like (in decimal) and these are found at address 6CB5 in my particular ROM.
I use WinOLS Demo software only as an aid to find maps, manipulate and visualise the data in text, 2D or 3D form. It is no use for its more advanced features in this case as it cannot handle Nissan ECUs.
I use freeware HXD Hexeditor to manually copy and paste modifications to create a new ROM file.

[jaf]

And a 3D view that shows the dramatic EGR region on the stock map alongside the modded map.
You really have to "interpolate" the map values to understand what the actual outcome is going to be.
For that I use a spreadsheet (see the 16x16 map pics)

[seb.racing]

I post to follow
in Australia, you use what octane fuel?

[jaf]

Australia has 91, 95 or 98 octane fuel fairly widely available and a bit of E85 in very few places.
I will be covering ignition timing next so this is a relevant question. I run 91 octane usually. There are some surprises in the stock timing but that story is coming up....

[seb.racing]

ok
in france, octane 95 and 98, octane 95 + ethanol E10, ethanol E85

good job

[jaf]

On to ignition timing....Part 1

There is no single definitive map for ignition timing. The easiest and safest way to alter timing is to edit the "low knock advance" map.
There are 3 identical consecutive maps in this ROM which are the low knock advance maps. I keep these identical when editing.

Values higher than 128 indicate an area where knock sensing is turned on aggressively. The map is too hard to interpret with the large step up in values, so step one is to rationalise it by deducting 128 from all values above 128. If you are expecting to see degrees advance, you won't!!! The values add onto another map to make up the overall timing. Each step up in value equates to around +0.6 degrees. Do not edit to make the 3D graph look pretty - edit based on what you see in your logs. A bit of guess work is involved to figure out where on the load axis to tweak, but who said it is easy? The RPM axis is accurate in this case.

[jaf]

On to the tuning (or What was Nissan thinking???) Part 2

Note on the difference graph that some significant timing has been pulled at low rpm and bucket loads added elsewhere. The dealerships often retard the base timing to 14 or even 13 degrees to solve spot knocking issues because of a whacked out factory tune. The (relatively consevative) tune shown works perfectly on 91 RON and 15 degrees base timing.
Adding a decent amount of timing here causes another problem elsewhere - there is another map added on top of this one for adding more timing when the engine is cold - a lot more!. That is for the next installment....