Lambda period compensation?

[Mobne]

I read trough the flex fuel document. It no where states the need to compensate the lambda period with flex fuel.

With petrol the delay is tuned and it controls the lambda really good. No big fluctuations.
When going over to the alternative fuel the control delay seems off, it fluctuates a lot and have bad control.

Since I see nothing about compensation for this I guess I have missed something else.

The blend petrol was tuned is about e15-20. The blend alternative fuel reach is about e80.

I went trough the period on gas loads up to like 60. And it behaved well with petroleum.. e85 the control
Is a mess.

Alternative fuel is ethanol “100” as described.

[David Ferguson]

Assuming you are using the GPxx packages, are you sure the Engine Charge Cooling Gain Primary has the Fuel Composition Axis enabled, and is properly setup?

I would imagine the Charge Cooling Gain of E85 would be much higher, and would affect how good the calculation of a needed fuel trim turned out to be.

You need to calibrate this value so 10% change in Fuel Mixture Aim (as modified by the Alternative Fuel Mixture Aim Blend), results it hitting the target -- if not, the closed loop fueling will "chase its tail" trying to hit the target.

[Mobne]

You need to calibrate this value so 10% change in Fuel Mixture Aim (as modified by the Alternative Fuel Mixture Aim Blend), results it hitting the target -- if not, the closed loop fueling will "chase its tail" trying to hit the target.

This is for sure what is missed to check.

Yea fuel composition is activated for charge cooling.
I got my charge cooling gain to about 15.5 on petroleum (0% blend) and I set the gain to about 20 (100%blend) for alternative fuel, but I have missed to check if this value actually is correct or not for the alternative. Primary follows well.

The method will be the same as for primary fuel? Having the alternative fuel mixture aim target lambda 1 on like 2000rpm and then change lambda target for alternative to line lambda 0.90 and adjust the gain until I get it?

(Would this be accurate on idle also or do the engine need higher rpm or even load to show the effect of charge cooling gain accurate? Don’t have access to dyno atm.)

The 10% charge, that must be in the alternative fuel mixture aim map when the fuel blend is blending 100%? Is that correct? If I change the main aim with 100% blend I would expect nothing to happen?

[Mobne]

I have calibrated the charge cooling for E80 now. I got a value of 22 for E85.

Lambda 1 on idle and lambda 1 on 2500rpm no load on petroleum.
With E80 I still get lambda 1 on idle but on 2500rpm it runs like lambda 1.2

Should I compensate this with alternative fuel volume compensation? Any idea why idle is still lambda 1 on both fuels but not on higher rpm?

[David Ferguson]

Is the fuel mixture aim changing? Is the alternate fuel mixture aim the same as the main fuel mixture aim table?

Posting your package may allow more help.

[Mobne]

Yes both fuel mixture aim tables target lambda 1.0 at the points I mention.

The fuel mixture aim is lambda 1.0 it’s just running lean and not on target.

[David Ferguson]

Could be incorrect fuel properties, injector calibration, or perhaps the fuel pressure setup (Is the differential pressure correct and remain constant even as the manifold pressure changes?)

Verify that their are not any Fuel Volume trims that are active when testing this.

What RPM / Load did you use to calibrate the Charge Cooling Gain? I know you said you weren't using a dyno, but you could still try this with the car loaded (left foot brake, or going up a hill), and someone else driving while you use M1 Tune.

[Mobne]

What RPM / Load did you use to calibrate the Charge Cooling Gain? I know you said you weren't using a dyno, but you could still try this with the car loaded (left foot brake, or going up a hill), and someone else driving while you use M1 Tune.

Is it vital that the engine is on slight load? Just rising rpm is not enough?

Also there is no petrol avail able here with out ethanol. E10 is what we get. That does not matter when calibrating main fuel?

The alternative fuel volume compensation is that something you shouldn’t need to use?
I also find it kind of difficult to get it accurate because I have different fueling needs depending on my oiltemps also.

The engine runs leaner with higher oil temp (at least that’s what it feels/looks like causing it). And I see no possibility to compensate for that.
When the closed loop lambda is setup correctly it will have no problem to compensate for it but when calibrating this parameters with it off it’s still making it hard to get accurate results.

[NathanB]

Hi Mobne,

I'm going to cover off a few points here i no particular order:

Closed Loop Period:
- This value defines the transport delay of exhaust gases from the combustion chamber to the lambda sensor. This value changes with exhaust mass flow (as a result of the change in inlet mass flow). The fuel used has little to no influence on how fast the exhaust gases travel out of the engine. As a further point, in your closed loop period that you had in the file I have a copy of, it is a straight line, with the period decreasing as exhaust mass flow increases. In reality, there will be a point that the period will level off (look at almost any base map provided by MoTeC)

Calibrating Charge Cooling Gain/Any calibration completed from a lambda step test:
Yes, it is vital the engine is under some load to ensure there is enough exhaust mass flow for a consistent and accurate reading - particularly depending on exhaust length etc. It should also be pointed out that the cooling charge gain is rarely a single value - the temperature of the air will effect this as there will be a higher cooling effect when fuel mixes with hotter air rather than cold air.

E10 When Calibrating efficiency table.
To explain this once again, Volumetric efficiency is expressed as a ratio (in this case a percentage) of the engines ability to effectively fill the cylinder with its displacement of air. (Within reason) The fuel that you are using has absolutely no influence on this. Whether you have E0 or E10, it will not effect the engines ability to fill the cylinder with air. Please remember once again IT IS A VOLUMETRIC EFFICIENCY TABLE, NOT A FUEL VOLUME/PULSEWIDTH TABLE. The efficiency main table says for a given point how efficiently the cylinder is filled, which based on the displacement and some other corrections works out the engine load (and air mass) to calculate the amount of fuel needed. only times this can be drastically effected is when using fuels such as methanol (with a stoich ratio of 6.47:1) or nitro (with a stoich ratio of 1.7:1) where the amount of fuel volume introduced into the air in the port really starts to impact the volume of the port for the air to enter the engine.

Fuelling adjustments.
Typically the fuelling can be accounted for with correctly calibrated cooling charge gain for the different fuels, and often a small correction needs to be applied to the Fuel Injector Primary Flow Correction. The flow correction is to account for the different flow rate due to the difference in viscosity between the two fuels (this is typically in the range of 4-7% in a lot of applications)

Fuelling changes due to Oil Temps.
I'm really having a hard time believing this is what is influencing the fuelling dramatically. Working with the idea that oil increases in temp slower than coolant, another item that often will increase in temperature at a similar rate is fuel temperature. Is the fuel temperature value from your sensor appear to be accurate? Where is your flex fuel sensor actually mounted? Is it a good representation of the fuel temperate in the rail, or is in a surge tank line for example, where the fuel starts to get hotter than what is an accurate representation of the fuel in the rail due to frequent cycling and the density calculation starts to become inaccurate and throw out the fuelling.

I really think you should start working with your selling dealer, as it is the responsibility of the selling dealer to support you with your issues. Otherwise, there are several dealers in Sweden that may be able to assist you:

https://www.motec.com.au/dealerssection ... pe/#Sweden

[Mobne]

Thanks Nathan!

Closed Loop Period:
I don’t know why, but I had the delays measured well in my latest tune on 98 octane and it followed nice. When I went over to e85 it is a complete mess. But at that point charge cooling was not calibrated well for alternative fuel. Little low value.
I have sent you the tune when the lambda was calibrated.

“Calibrating Charge Cooling Gain/Any calibration completed from a lambda step test:
It should also be pointed out that the cooling charge gain is rarely a single value - the temperature of the air will effect this as there will be a higher cooling effect when fuel mixes with hotter air rather than cold air.”
Is there base values for this? So I don’t have to invent the wheel my self?


“E10 When Calibrating efficiency table.”
I know volumetric is the same. I was calibrating the charge cooling for 98 octane main fuel. That’s why I ask if it can be done with e10 also. Sorry I wasn’t clear with what I mean.

“Fuelling adjustments.
The flow correction is to account for the different flow rate due to the difference in viscosity between the two fuels (this is typically in the range of 4-7% in a lot of applications)”

So on my injector bench, the flow difference on 98octane and e85 is the number that should/could be entered here? If I remember correct they are 7% larger with 98octane e5 compared to e85.
If this is the value I need here i can do a new flow test with e5 and one with e85 to confirm.

“Fuelling changes due to Oil Temps.”
Sensor is mounted in the trunk between the main fuel pump and the fuel rail. So temps should be really accurate to what the rail see.
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