Having recently installed a new intercooler i'm now seeing IAT temps of 25-30 deg c which is great compared to previous. The problem i'm encountering now seems to be the MSLog Viewer VE Analyse wants to throw loads of fuel in compared to the previous setup. Having searched around I can't seem to see anyones VE table this high and am wondering if this is likely to be an issue rather than a correct result from autotune.

I've attached the current VE Table and AFR table used for autotune for information.

 

How lean was it before you ran autotune?

 

This was the VE Table before running autotune with the new intercooler and low IAT temps.

 

The results are correct.

What you have done with the IC is allowed the engine to gulp more air (cooler air is denser assuming the pressure is the same). With more air, you need more fuel.

The numbers in the VE table are dimensionless. Basically, the fuel injector pulse ends up being (VE Table x Req. Fuel. x Various Corrections). The maximum value allowed in a VE Table cell is 255 (8 bits), and you are far away from that, so no worries.

A little Megasquirt secret is that you actually want to lower Req. Fuel to increase the numbers in the VE Table so they are nice and high while also comfortably below 255. By doing this, you essentially increase your fueling resolution. You can "think" of Req. Fuel as your minimum pulse width, and you would like the minimum to be as small as possible for best control.

So, you went up from ~117 to 150. That's a nice power gain.

 

If you went lean you're making more power.

 

Thanks for that it makes sense, however what happens when it gets warmer here and as such my IAT's will increase taking into account the ambient temperature. Surely i don't have to get it re-tuned at this time? Is this when the hard coded gas law settings will come into effect? Or will i need to go closed loop and allow EGO correction to adjust for variable IAT temps?

Cheers

 

Once i had installed the intercooler i did several runs and noticed that the AFR's under boost using the existing old VE table. Once i got home i plugged the log into VEAL and it generated the higher VE table which i assume will richen up the AFR's on the next run.

Do you reckon i should disable the MAT correction whilst doing the log runs or not?

Cheers

Iain

 

Why would you disable mat?

 

Just to try and take a variable out of the equation...although looking at the setting for MAT correction it stops at 3k rpm so it should not have any effect in boost so i guess it can stay on.

Looks like it a trip back to Nick to get a re-tune having now installed the intercooler and the IAT being so much lower than when it was originally tuned.