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VE + new injectors = More VE? Big changes required in VE map after injector change.

MoTeC M1 Software Tutorial

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I recently switched from some Denso RX8 injectors (or copies of denso injectors) to ID1050x's as the RX8 injectors didn't like the E85... The caps at the end of them were melting and seemed risky to assume any of the internals would last. The injector cal was provided by Motec, but not one of the standard cals in them M1's drop down.

The ID1050x is way too big for what I need, but they have the injector cal, are plug and play, and readily available.

I recently had the car on the dyno to check everything was all good with the new injectors and after an increase to the charge air cooling factor - 26 > 28, I started on some WOT runs it was clear the car needed a lot more fuel.

We did make the lambda aim a little richer... aim for 0.8 instead of 0.82, but still, thought it was a larger than expected change. You can see there's a pretty big increase in the VE numbers which I wasn't expecting.

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A few possible reasons why

The RX8 injectors did not match the cal - there's apparently a lot of copies of these injectors on the market now and it's hard to know if you have legit ones without pulling them off and RX8.

I've forgotten something when swapping the injectors.

I installed a fuel pressure dampener, so not sure if that's having an effect, but the FP data looks as noisy, if not nosier than before it was fitted.

Anyway, anyone else seen this sort of change when changing injectors before?

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It sounds like the most likely thing was the provided injector data did not match the injectors you had installed, as the injectors were different to your supplied part number, or modified.

There is also a chance the reference flow or fuel pressure delta was entered incorrectly.

The fact you increased VE numbers would indicate the previous injectors flowed more than the injector data.

Changing the cooling charge gain would impact the fuelling regardless. The mixture change would not make a difference if the injector data matched the injectors.

Do you have a fuel pressure sensor? And what kind of fuel pressure damper have you fitted? Depending on the damper, it may be inducing a restriction.

If the fuel pump was borederline on flow, and you are commanding more fuel from it (richer mixture) you may be seeing pulsations due to fuel flow issues. When you are borderline on fuel supply, the fuel pressure is more prone to fluctuation due to the injectors opening and closing.

How has everything changed at lower regions of the map? If everything is close everywhere else, and the difference is only up top, i would suggest you have just become aware of a fuel supply issues.

Thanks for the reply.

I'm leaning towards the old injector data and injectors not matching...

I have a fuel pressure sensor and I've slowly redone the fuel system since upgrading to e85 - DW100 fuel pump, radium fuel filter, -6 lines to radium rail, FPR and dampener. The base fuel pressure is 3bar, and it has a vacuum reference to the intake manifold.

The engine is only making 160whp... so would be pretty surprised it's a fuel supply issue. The FP data was all good when I had it on the dyno, and the engine produced pretty much the same power and torque.

The engine doesn't really have a low end of the map... big cams, lots of overlap... I really need to look at doing the set up differently I think with the manifold pressure estimate... or Motec could revise the GPA package so efficiency map can select TPS or engine load normalised instead of MAP.

It is hard to comment without logging to review, but you would want to check the fuel pressure differential from logging of the old data versus the new setup. Even changing fuel pressure regulators can have an influence depending on how well they maintain pressure against the flow of the attached pump (a lot of OE regs don't work well at low pressures when attached to fuel pumps with 2x factory flow)

You would then be looking at using the multi throttle tuning method that has been in M1 for quite a while now. I have attached the tech note in regards to how this is setup and tuned for your reference. I think you will find it will serve the purpose you need. The V8 supercars and S5000 series have managed to use varants of this strategy.

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Thanks Nathan,

I hadn't seen that document - there's probably another post on here when Black Rex is telling me to use the Manifold Pressure estimate table, but I couldn't figure it out.

I miss having a development ecu with build... anyway. I'll go through it in a bit more detail at some point... It says simplified method, but I am still scratching my head.

This did prompt me to have a look at the ecu file during lunch and I saw one error - I never changed the displacement from 1.884 to 1.906 when I put in the E85 engine last year :( Pretty basic thing to over look.

The other method suggested from Black Rex is one of the earlier methods to make the model behave relevant to throttle position is via use of the estimate table to make the throttle position directly reference manifold pressure.

This method uses the in man pressure mode set to estimate, and usually I recommend setting engine load normalised to throttle position.

With the manifold estimate set to estimate, it references the estimate main table to determine you inlet manifold pressure. As this is relative to throttle position, you can set this 1:1 so 0 throttle is 0kpa, and 100% throttle is 100kpa.

This turns the manifold pressure axis into throttle position. Now as it still uses the fuel model, you end up with a relatively steep engine efficiency table, and be prepared for VE numbers of 10 or lower down the bottom. You will also want to add a fair bit of resolution, particularly down low to get any good drivability.

Both methods have their pros and cons, and it largely depends on what method you are most comfortable using.

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This turns the manifold pressure axis into throttle position. Now as it still uses the fuel model, you end up with a relatively steep engine efficiency table, and be prepared for VE numbers of 10 or lower down the bottom. You will also want to add a fair bit of resolution, particularly down low to get any good drivability.

Yeah, this was the method I tried and couldn't get it running. Probably the low ve values are why.

Thanks again for the details. If I get some time I might try one of the methods. The current way I am doing works well enough, just would be easier to tune the part throttle cells when driving on the road.