Quiz on reflash tuning

hi,

Just notice that there’s a new quiz section for practical reflash tuning course, I personally like it very much and would take the quiz as review every month, however I found an interesting quiz question from “operating principles” section that confused me, it says: why MAP based ECU typically not have separate air temperature compensation table for fuel delivery?, isn’t the question should be MAF based ECU?

according to what I have learned from the EFI fundamental course, most MAP base ECU would have AIT sensor to account for air temp and ECU could base one AIT and the difference of the air density(every 10 degree 2.5%~3%) to compensate fuel delivery.

thanks

Steven Tsai

Steven,

Thank you for the heads up. I have passed this along to the team for review.

Hi,

thank you for taking time to read my question and fast response!

Steven Tsai

Hi Steven, thanks for picking this up. Its been a long time since I wrote and presented this course. You're right in so much as the module and quiz are a little poorly worded. We really need to split the ECUs into two operating principles. We can have a MAP-based ECU with an injector-time based fuel table or more commonly now (and which I refer to in this module), VE-based fuel models.

In an injection time based ECU we will definitely have an IAT comp table and as noted we tend to trim the fuel by around 2.5% per 10 deg step. In a VE-based fuel model the IAT is compensated for inside the fuel model and hence we 'usually' don't have a separate IAT comp table. Now I place 'usually' in quotes as for every rule there is an exception. I often find that the VE model can be a little aggressive with the IAT trims under certain conditions - Usually idle and light load. In these instances it can be beneficial to adjust the IAT trim being used. For example the Haltech Elite?Nexus have a tick box called 'AUto VE Air Temp Compensation' which applies the technically correct trim to fuel mass based on IAT. If you tick this box then you should have the IAT correction table set to zero. Alternatively untick the box (which I usually do), and trim the fuel the conventional way.

Apologies for the ambiguity and I hope the above helps.

Hi Andre! Big fan of your online courses, it really helps a car enthusiast like me to learn the knowledge of engine building and ECU tuning world.

Thank you for taking your precious time to explain to me the differences between MAP based ECUs(injector-time and VE), and how they deal with IAT “differently”, my though was they all use compensate table for IAT, and I just recalled, it’s actually a quiz question from EFI fundamental course under “engine management system table” section, “ how does a VE fuel model deal with IAT?”, (see attachment) so the mistake was mine :p, my apology.

thank you for correcting my misunderstanding!! Much appreciated!!

Steven Tsai