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Tps VE and flex fuel

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Hi i am planning to run flex fueling on an s54 bmw engine which has been turbocharged. The engine still retains its ITBs and has active double vanos. I plan to tune the engine using VE based fuel tables with throttle position as the load axis, load=map as equation load source. Will this cause any issues?

What ECU are you using? What flex fuel support does it have?

Provided the ECU offers sufficient flexibility in the flex fuel strategy, this should present no issues. Assuming the VE table is accurately tuned, the ECU doesn't really care if you're using TPS or MAP as the load axis. In my experience ideally you'll want either a second VE table or a trim table that you can blend in as the E% varies. While in theory you should be able to get away with a single VE table and just define in the ECU how the fuel properties change with E%, my experience is that this rarely deals with the changing fuel characteristic completely and will leave some remaining fuelling error.

That is good to hear! I will be using a maxxecu. It has VE based fuel tables with a lambda target table. It supports flex fuel and the ethanol percentage can be used as a table axis. There are plenty of extra fuel,ignition and boost tables so i think all should be well.

Hi Andre, I know this is a pretty old thread but this is the closest topic that is related to the current situation I find myself in. I've watched the TPS+Map webinar a couple times and searched to try and find a detailed enough answer but I haven't been satisfied with them enough to be able to come up with a conclusion on my own.

Similarly to Joeymcc, I have fitted 20V blacktop throttles to a Toyota 2zz engine that was previously boosted a/ running flex fuel; ECU is a G4X. Because of this, the previous fuel model is set to "modelled-multifuel"

I've read through the link help file and it suggests the same thing you do in the TPS+Map webinar with the R32: TPS as y axis on the main fuel table, Lambda target with MAP/MGP as the Y axis. If I change to open loop, I need to also change the fuel model to traditional.

From what I've read, Alpha N is TPSvsRPM so that one isn't an issue but it leads to my first question:

1) What options do I have for the X axis for lambda target? I know RPM but is there a reason to look at any others? If so, what are the advantages and disadvantages.

Additionally, I was doing some searching, and I also so that I could do a secondary fuel table in Link. This pulls up the option to use interpolation between full e-85 (2nd table) and pump gas (main fuel table). I'm assuming for the 2nd fuel table, it's TPSvsRPM as well but with values (for a tank full of E85) to get to 1 lambda. As for the ignition tables, I suspect I need 1 for pump gas and a secondary one for E85.

2) I'm confident that this is the best option but if not, please explain an a better alternative and why my assumption is wrong.

Moving on from that, it also brings up an additional table "Fuel table ratio". In the help file it mentions a typical axis with %Ethanol, Multifuel blend ratio, or some other analog variable.

The help file says it controls the influence between ignition table 1 and 2, with values ranging from 0-100; where 0=Ignition 1 with full control, 100=Ignition 2 with full control, and 50 being split evenly. The table is also a single row. (I'm interpreting these as %Offset or something similar to that)

I'm certain that I'll need both considering I need to interpolate since ethanol allows greater timing advance but this leads to my next few questions:

2) For the ratio table, what would be the best choice for the axis? %Ethanol or Multi Fuel Blend?

3) Would my values just be different ethanol percentages ranging from 0-100? How fine should they be? Would the %Offset just follow those values equally? (please see attached snip)

Thanks in advance

Attached Files

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