Why are remaps needed?
 

Hey everyone

I’m interested in learning about remapping and I feel like I’ve got a good grasp on most of the fundamentals, but there’s one thing I don’t quite get… why are remaps needed after modifications?

Like if I map the stock engine to run 12.2 AFR at WOT, why do I need to remap when I, say, do a full decat. I get that a decat will derestrict exhaust etc, but if I’ve told the engine to run at 12.2 surely it’ll still run at 12.2? Or would I need to change the AFR or injection or spark or boost or whatever to compensate?

I apologise if this has already been asked - I’ve searched a lot of forums and they all come up with the ‘do I need to remap’ questions and I can’t find anything scientific to answer the ‘why’

Thanks for the help :)

Working with the example you’ve given, swapping downpipes to a decat will cause boost spikes due the change in back pressure. This is no longer controlled by the existing actuator duty cycle settings, therefore these need to be changed and AFR’s changed to suit to prevent a lean condition. The bonus is that there is enough injector duty cycle on most cars to allow a good bump in power at the same time.

So am I understanding correctly that, in this scenario, the boost would flow easier and result in earlier/higher boost availability, so the boost map would need to be tuned to account for this?

I still don’t get why the AFR would need changing though… if I’ve already tuned somewhere on the map for that increased boost pressure wouldn’t the ECU jump to that area of higher boost in the map and find the AFR value there? Or is that the level of boost which was originally at, say, 7k rpm is now at 5k so the ECU needs a corresponding value at 5k now?

https://sites.google.com/site/asubie...gguide/ver-1-0