Has anyone tried to improve mpg by tweaking ECU settings such as fuel / air ratio or other settings?

 

If so what were your results?

Every single manufacturer will have spent millions and thousands of man hours doing just that, OK they are hampered by emissions legislation, or not in the case of VAG

 

So I would suggest that other than undoing an emissions fix to go back to the emissions cheating map you would have to be Einstein and have very deep pockets to make any improvements.

 

Talk is cheap though and many people believe or want to believe the mpg figures from their Maxidot (which are already inflated) after a remap not realising that the ECU thinks the engine is getting less fuel than it is actually consuming, it can be adjusted to a true reading via VCDS but then people cannot boast of impressive MPG and increased power.

Edited 8 September, 20205 yr by J.R.

I get between 37-41mpg for an octavia II 2008 saloon, that's sounds a bit low to me, tires are at 35psi, although tires do seem to lose pressure pretty fast, either some crack or bad valves.

Smear a bit of saliva over the valves after inflating and watch for the film to bubble, if it does remove and refit the valve core.

 

Most likely you've a small puncture or the tyre changing monkey didn't clean the rim before fitting a new tyre and it's not sealing 100%.

Petrol or diesel?

13 hours ago, J.R. said:

Every single manufacturer will have spent millions and thousands of man hours doing just that,

 

I wouldn't bet that pessimistic. Car manufacturers have to create a car that fits to everyone - so it must be strong enough but meanwhile it shouldn't consume much fuel etc.

But I believe that if you need it for your certain needs than it can be tweaked that way. At least I've talked to people remapping cars and they said that some people choose the fuel saving and they do that.

Also, some of the emissions limits  that manufacturers must meet cause conflicting constraints, causing compromised fuel efficiency.

For example, modern diesel engines could be much more fuel efficient if there were no limits for NOx output.

 

Tuners are not so bound by regulation; arguably not at all, as long as the results of their tweaking don't cause MOT issues (NOx is not measured at MOT).

1 hour ago, Wino said:

 

Tuners are not so bound by regulation; arguably not at all, as long as the results of their tweaking don't cause MOT issues (NOx is not measured at MOT).

 

Neither were VAG once and they found a very good way of reducing emissions at MOT.

 

Hence my comment about removal of the E189 "fix", thats probably all the tuners are doing with their economy mapping, they could not do better than a company that applied themselves to the task regardless of cost, and it did indeed cost them dearly eventually.

34 minutes ago, J.R. said:

they found a very good way of reducing emissions at MOT

No they didn't, as MOT doesn't measure NOx.

It was Type Approval emissions testing that they gamed, in EU and US, different level of testing to MOT.  They still had to build cars that were capable of behaving themselves 'just for the testing'.

 

Tuners don't have to even bother with that.  Legally speaking, in the UK at least, it's illegal to do anything (or presumably to have anything done) to your car that makes the emissions worse than they were at type testing, but that's hard to police, to put it mildly.