Swapping ECU while keeping VE and ignition tables

For a couple of years I've been wanting to swap my current ECU (ME221 Gen1) for a more modern one (Thinking about a Haltech Nexus S2 at the moment), but since I don't personally have access to a dyno and the car is already dyno tuned with the current ECU, I would like to reuse the VE and ignition tables and do some road tuning to dial everything in.

Because volumetric efficiency says something about how well an engine can move air, I would think this would stay the same as long as the engine itself is unchanged. I would also use the same base timing to make sure the ignition table would remain the same aswell.

Would I be correct in thinking this would indeed work, or are there more differences between ECUs that would not make it possible to retain these tables?

You can usually copy over a VE / Fuel Table, and only need to scale it for a different ECU as a starting point.

For example, after you get the new ECU running, and find the fuel mixture is 10% lean at idle & cruise, you just multiply the entire table by 1.10 to fix it.

You should be able to use the Ignition table unchanged, just verify with a timing light (with both the old and new ECUs) that the commanded timing is what is actually happening.

I would still take it to a dyno as the fastest way to restore what you had for the fuel tuning.

Hi David, Thanks for the quick response! This was exactly the information I was looking for.

Seems like I can continue with this plan.

Thanks again!

I did exactly what your asking on a previous car, I went from a Vems ecu to Maxxecu, before i went out for the first drive ( I should add, at the time the engine was a budget build with only forged rods & stock pistons, I was planning a properly built engine) I made sure the Map sensor scaling was identical, injector data etc, more importantly i checked & double checked the base ignition timing. There was a 4 degree difference between what the 2 ECUs wanted.

I set the lambda correction limits 25% as opposed to 10% on the old ECU, hoping that the ECU would 'catch' any differences, Lean fuel cut set super safe, lots of datalogs and slowly ventured into WOT and full boost. What i found was weird fuel swings that didnt make sense, it would add approx 15% in the lower load areas and approx 10% higher up. Timing wise all appeared to be ok, i was running fairly safe ignition on the old ECU and i couldnt hear any noticable Knock whilst running Maxxecu.

I corrected the VE table based on the lambda corrections, tidied things up a bit until it 'looked' right, I did later go onto sneak more timing in until i was happy that enough was enough! The engine went a further 4000 miles like this with no real issues.

The enrichment tables took quite a bit of work as did the idle settings - i had to basically start again.

So to answer your question it can be done, but it appears brand X & Y ECUs do they're calculations different and i would DEFINATELY take your car to a tuner/dyno to have it checked properley otherwise things may end bad! Maybe if your were switching from an older version to newer of the same brand??

Just to add, i am by no means a pro tuner although i do have around 9 years experience in standalone ECU tuning, most of which done on the road and then on a dyno to optimise the ignition and fuel.

Great addition Seb! Will definitely take this into account when I eventually make the switch. Better safe than sorry.