Fuel remapping

[Patryn999]

Now I know quite a few people have tweaked their upper quadrants in order to tune the AFR's and build a bit more power:

However I'm a little curious as to whether or not anyone's had a go at leaning out the low loads/mid rpm settings. Mainly around 2.5-3.5k rpm. Reason is I've been looking at the tables and we don't even run stoich at these speeds, so on the open road we're throwing gas out the back.

Now I assume this is to keep egt down, however I was wondering if anyone has had a play before with a probe in to see if we can save some fuel here. Also was curious about low-speed/low-load settings, as most modern cars run 16-15:1 at these settings to maximise fuel economy (IIRC, best fuel eco is 16.2:1) around town etc. Again I assume this is something to do with keeping the engine cooler but would like to hear ppls opinions. It'll be a month or 2 until I can afford wideband and egt sensor (as well as paying car off!) so I wont be able to give any personal results till a much latter date.

[AderC]

At cruise you'll be running closed loop rather than reading off the maps, so it will be running stoich (14.7 AFR).

It is possible to force the car to run open loop and read from the fuel tables by altering the Open Loop Load tables (i.e. lower the load values at which open loop is triggered). You could then raise the AFR values to 15-16 if you wanted to run lean at cruise for fuel economy (but wouldn't recommend this unless you're monitoring with a wideband!).

[Nick Mann]

3500rpm is not a value you can give an exact AFR to. It depends on the position of your right foot and the air flow at the time (boost pressure).

Cruising on the motorway/through town at 3500 I would want to have stoich AFRs if possible, but in 3rd gear at 1.0bar I would want a number beginning with 11.

You can improve economy with some kind of fuel control, but not enough to justify the cost of the fuel control itself, IMO. It can be seen as a small added bonus when combined with power and response improvements though.

[Wodjno]

As above.. Buying equipment just for bringing down fuel consumption will not make financial sense. (well maybe over 5 years or so.
Also at those rpm you posted, if your on light throttle your fueling is governed by the lambda sensor, so you will be running at stoich. The maps u are seeing lower afr's at are open loop figures and are points on the map that are crossed under accelleration. therefore differrent loads are seen compared to cruising and thus lower afr's.
If you already have the kit to control and monitor AFR's in place for playing with the power. Then u can alter crusing AFR's via a wideband controller of piggyback ecu or standalone..
Quite a few have done this via a wideband, and I have managed it via a Piggyback..

Hope this helps..

Wodj

[Patryn999]

I bought the equiptment (or am in the process of) to tune the higher up and just to learn as much as I can. Thinking if I have the equipment and the time then why not?

And Nick I do realise that, which is why the maps are 2D tables with dimensions of load and rpm. I have a programmable ECU (7202) and tactrix 2.0 cable so once I've purchased a wideband to replace the narrow (simulation out for ecu in) I'll see what I feel comfortable doing.

Thanks for your input guys

[Turbo_Steve]

Of course, the alternative is to change the stoich target (14:1) for something a little leaner. Stoich is ONLY best for emissions - at cruise engine temps should remain stable at 15:1 or even 16:1, though I'd be getting nervous at how dry that's running on a longer run: running an EGT per cylinder becomes essential at that point!!! Which means you've just spent more than you would ever save

[Wodjno]

Of course, the alternative is to change the stoich target (14:1) for something a little leaner. Stoich is ONLY best for emissions - at cruise engine temps should remain stable at 15:1 or even 16:1, though I'd be getting nervous at how dry that's running on a longer run: running an EGT per cylinder becomes essential at that point!!! Which means you've just spent more than you would ever save

What if you move it from 1 cylinder to another after collating data Thats 1/6th of the price

[Turbo_Steve]

Works great unless the hottest cylinder is the last one you try? Then it's quite expensive...........

In theory you could put one EGT in each manifold and see which bank runs hotter and then work on the basis that as long as the hotter bank is cool enough you're okay. Chances are there is one cylinder that runs hotter than the others, though, either because of marginally less fuel flow to the injector, or cavitation in the water jacket, or poorer oil-flow or whatever.

The best way to do it would be to go to a proper tuning place, and either put the engine on a bench dyno, affixing 6 EGT probes, Wideband lambdas and 4 or 5 fuel pressure monitors, feed it warm air (heat up the intercooler) at high load for 10mins, lean it out, repeat, lean it, repeat, and see which cylinder heats up.

It's worthwhile knowledge that I suppose we could club together to find out, as every engine I've ever worked on has one "hotter" cylinder.

[ninjadaniel]

You will find that our engines do run stoich above 2500 rpm at low load, you need to swap the axis on your def file. You should see a line of 14.1 almost to 100 load, across the first rpm row, if you don't then the axis aren't swapped.

Compare with stock evo map, these are all swapped axis

[lateshow]

So is it actually aiming for 14.1 ? Because my wideband shows that my car is doing a loop: 14.1-14.7 So the average must be something other than 14.7. Is this normal. I'm using the same wideband to control the ecu also.

Of course, the alternative is to change the stoich target (14:1) for something a little leaner. Stoich is ONLY best for emissions - at cruise engine temps should remain stable at 15:1 or even 16:1, though I'd be getting nervous at how dry that's running on a longer run: running an EGT per cylinder becomes essential at that point!!! Which means you've just spent more than you would ever save

[Wodjno]

Stoich Target is 14.7. I think Steve made a typo.. Aim for 15.1-2, or leaner. Depends how your car feels. Unless u have knock monitor or EGT's. Then it'll be by the seat of ur pants tuning.
15.2 would be best if you haven't any other monitoring except AFR.

[scientist]

Have any of you guys tried disabling Closed loop yet?

[Kenneth]

My car didn't start running rough until close to 20:1 AFR.

[Wodjno]

My car didn't start running rough until close to 20:1 AFR.

But was it running efficiently

[Kenneth]

Efficiently enough for me drive the short distance to work and back

Do you mean power efficiency, or cost efficiency? Not that it matters, as I didn't run that way long enough to find out.

[Shtiv]

Daniel's comments above aare correct, the axis need to be swapped, seeing as this is about fueling, has anyone found and tested the lean spool tables yet?

[phosty]

So Daniel/Shtiv, should the Hi_octane map look like the lower map in this screenshot?

Hi Octane x-y swapped.jpg

If so then it makes sense as it generally shows the mixture getting richer as the load increases for each rpm line. But anybody any idea why they lean it off slightly aove 6500rpm?

I thought that regardless of the ecu operating in open or closed loop the AFR setpoint was always taken from the Octane maps (not sure why I think this - possibly mentioned previously on this forum?). The open loop tables identified by AderC here just dictate if the ecu operates in Open or Closed loop depending on load.

If so then just raising the AFRs in the octane maps should lean you out as desired.

Or am I sorely mistaken

[Nutter_John]

The top map looks correct but the bottom looks like you need to flip the axis over as the 9.8 values are at the bottom middle like the top one

and yes it is just a case of upping the values to lean out the mixture

[Patryn999]

Phosty, at a guess I would say thats because our peak boost is around that area so the air will be hotter == more fuel to avoid det. But that'd be shear guesswork.

Current opinion seems to be that the bottom configuration is correct (esp. in OzVR4). I had a play when tuning mine and got a result where I expected it to using the swaped values (lower) and no change when altering the map in same load/rpm location when not swapped, but then I popped my intercooler hosing and lost a hose clamp; such was the end of my tuning day.

However I believe Shtiv has done some dyno work with the tables and seen specific single-cell altering results so it'd probably be best to wait for him to reply.

[AderC]

I thought that regardless of the ecu operating in open or closed loop the AFR setpoint was always taken from the Octane maps (not sure why I think this - possibly mentioned previously on this forum?). The open loop tables identified by AderC here just dictate if the ecu operates in Open or Closed loop depending on load.

I'm not going to take the credit for finding the Open Loop tables, only confirming that they were correct :-)

I've leaned my fuel map out slightly on boost:

Stock:

ECU_Stock.jpg

Leaned:

ECU_Tuned.jpg

I daren't go any further as I don't have a wideband, but this makes a very noticeable difference. I've had to tune out knock in some areas to compensate, but I'm not getting more than 1 or 2 knocksum values anywhere.