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Fuel Map all negative kPA? Is this normal? 350z


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Car: Nissan 350z, 2005

As a beginner tuner i am looking at our fuel table values and its mostly negative kPA.


Why is this?


I tried to set closed loop to be running from idle but i can't input a negative kpa value, so i assume my fuel table is incorrect?


Any help appreciated,


also we have fitted 2x wideband sensors in the exhaust port, one side is about 0.03 lambda out from the otherside, is this a normal variance on the 350z motor? is it possible to adjust one sides injectors to accommodate this or best to tune around the leaner bank?



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that's MGP not MAP - atmospheric pressure is '0' but still scaled in the KPA... - this is more for display than function. the ECU uses MAP KPA in the background.

You can very easily change the axis to display MAP by just right clicking the axis config and setting it to MAP - it will then automatically convert the existing axis to what you want.. ( where it reads -90 now it will show 10.. where it reads 0 now it will show 100. )

In other settings if the parameter expects MAP in KPA consider 0 as absolute 0 and 100 as atmospheric - I don't think you get the choice there.

When I adapted some ignition/etc maps from another ECU (Kpro) to the G4X it helped to have the MGP but once it was done I switched it to MAP which reads much nicer to me.

re: lambda difference

You can bump 3% more fuel on the leaner bank if you want - check under fuel/individual cylinder fuel correction - this is under the assumption that the sensors are reading correctly. maybe confirm it's reading correctly by swapping them over and seeing if the 0.03% lambda difference remains. I'd start by touching one injector on the lean bank at a time however as it is more likely to be one injector being lean rather than all of them. Conversely it could be the other bank is injecting too much. Or a combination. If it is the whole bank it could be a rail pressure issue. Relatives.

Your closed loop may want to run off Lambda AVG rather than each bank - but it depends on if your closed loop is configured to be aware of the banks or not - you can configure it for two... and assign each bank's lambda sensor.. there's also a two table long term trim option. maybe give that 4% leeway to enrichen and see what it does for the leaner bank over time.

0.03 lambda difference is a bit higher than I'd want - for a street car since most emissions tests have a 3% limit - 0.97-1.03 for a lambda test - and for a turbo for lean condition reasons. probably not an issue for an NA car at WOT unless it's a grenade.

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Using MGP on the axis of the fuel table will give more correct fuel with changes in altitude in comparison to using MAP on the axis.  MAP is still used either way as a multiplier in the fuel equation.  If your vehicle is not commonly used over large changes in altitude then it becomes more of a user preference in that case - either will do a similar job so you can use whatever you like.

By the way, you could start by deleting 50% of those fuel tables cells to make tuning life easier, then only add extra rows or columns if you find some area where linear interpolation doesnt cover the trend in VE/airflow.  I would generally start with 1000RPM columns and 20Kpa row increments. 

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Thanks for the replies!


I will just leave it how it is, was more just confused.

Re closed loop - if this is the case the MAP value of 0 should have closed loop running at idle, but when I modified my fuel table the lamda values changed, making me think that it's running open loop.


Are there additional things I need to check to make sure it's running in closed loop?

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If you are using the default 1366*768 or 1920*1080 layouts then you should have CLL status displayed in the tuning runtime panel on your fuel page.  

Otherwise you can hit F12 from anywhere to open the separate runtime screen and look at CLL status on the fuel tab.  


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I had the map low/high lock out both at 0, so it never turned on closed loop!


Does mixture map take into account any short/long trim fuel trimming from closed loop being on when applying the mixture map corrections?

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14 hours ago, Booki said:

Does mixture map take into account any short/long trim fuel trimming from closed loop being on when applying the mixture map corrections?

It does not at the moment, one trick people do do is to use a math block with lambda and the trims fed into it and a calculation such that the value it spits out is what the lambda would be if the trims weren't present, there are examples of this in some other threads in the forum.

I do plan to add code to take it into account at some point but you will still have issues if you have more than 1 bank of corrections for obvious reasons.

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  • 2 weeks later...

Can anybody look over this log and tune?


I smoothed out the fuel table, how ever when applying a correction based off mixture map i get some pretty decent spikes to correct it.


Does this indicate a mechanical running issue?




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