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Traditional Fuel Map set-up


mack85n
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Is there a link or help menu to assist in setting the base fuel map from a base file? I can calculate desired engine Injection duration just looking for assistance on the values and how they are entered in relation to Manifold pressure and the effect this has on the actual duration ie. at 100Kpa 50% of master fuel is actually 50% but at 50Kpa what it 50% of master fuel duration? Is it 50% of the  master value at 100Pka and 50% of that again?

Thanks

I also have this Excel to calculate Injection duration and a VE table from another ECU company if this could assist?

Injection Time Calculator.xls

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If using the "traditional" fuel equation with the equation load source set to "MAP", then the MAP multiplication happens in the background.  The number in the fuel table is percent of the master fuel number @ a MAP of 100KPa. 

So to make that clearer, here's an example based on my simplified table shown below:

At 100KPa MAP & 1000RPM, my injector pulse width would be 100% x 8ms = 8ms.

At 50KPa MAP & 1000RPM, my injector pulse width would be 50KPa/100KPa x 100% x 8ms = 4ms

Capture.png

Note there are many other factors that come into the final pulsewidth such as all the comps/trims and open loop table, but this should give you enough info to understand how the main fuel table number works.

Edited by Adamw
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If using the "traditional" fuel equation with the equation load source set to "MAP", then the MAP multiplication happens in the background.  The number in the fuel table is percent of the master fuel number @ a MAP of 100KPa. 

So to make that clearer, here's an example based on my simplified table shown below:

At 100KPa MAP & 1000RPM, my injector pulse width would be 100% x 8ms = 8ms.

At 50KPa MAP & 1000RPM, my injector pulse width would be 50KPa/100KPa x 100% x 8ms = 4ms

Capture.png

Note there are many other factors that come into the final pulsewidth such as all the comps/trims and open loop table, but this should give you enough info to understand how the main fuel table number works.

Thanks for the Reply,

 

Sorry but just to clarify if I required an Injection duration of 4ms @ 100Kpa MAP and  my master Fuel was set at 8ms I would enter 50%. But  If I required 4ms duration @ 50Kpa what would the value be then? it would be 100% yes?

Also do you have an equation to calculate mass air flow at different given MAP load points? I'd like to check them against the calculator I have?

Thanks, I appreciate the reply.

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Sorry but just to clarify if I required an Injection duration of 4ms @ 100Kpa MAP and  my master Fuel was set at 8ms I would enter 50%. But  If I required 4ms duration @ 50Kpa what would the value be then? it would be 100% yes?

You are correct.

 

Also do you have an equation to calculate mass air flow at different given MAP load points? I'd like to check them against the calculator I have?

Engine capacity x VE = Volume air flow.  Volume air flow x air density = Mass Air Flow.  

The problem is you dont know VE so Mass air flow cant be calculated.  As a starting point, If I have ever needed to build a starting map I would typically build my basic fuel map based on VE, using say 50% at idle ramping up to 100% at peak torque and drop back to 90% at redline, that will get you something that will run the engine.  Then you have to tune it from there.  I have seen various excel based fuel map calculators around but I doubt any will give you anything much closer than my guess approach above.  With link there are also many base maps supplied you with the software so I would suggest you just copy a fuel map out of one of these that is a similar config to your engine and change the master fuel until it runs.

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.

 

Engine capacity x VE = Volume air flow.  Volume air flow x air density = Mass Air Flow.  

The problem is you dont know VE so Mass air flow cant be calculated.  As a starting point, If I have ever needed to build a starting map I would typically build my basic fuel map based on VE, using say 50% at idle ramping up to 100% at peak torque and drop back to 90% at redline, that will get you something that will run the engine.  Then you have to tune it from there.  I have seen various excel based fuel map calculators around but I doubt any will give you anything much closer than my guess approach above.  With link there are also many base maps supplied you with the software so I would suggest you just copy a fuel map out of one of these that is a similar config to your engine and change the master fuel until it runs.

Thanks,

As it is for a TB48 Nissan I can't seem to find much in the way of base fuel maps. I do have access to the Haltech map which has a VE table so I may try to use that to base my equations on.

Thanks again

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