Mapped engine and degraded fuel economy

[watermoto]

Hello.

If an engine is mapped for more power without any other modifications, could the fuel economy get worse for a given load?

For example, two identical engines, one mapped, one factory. Both have the same load and are operating at the same RPM/gearing. Given the RPM and load is the same, then the speed is the same, so the wheel HP must be equal.

In this scenario, is it possible for the mapped engine to be using more fuel?

Just wondering what would cause the mapped engine to run less efficiently, thus use more fuel for a given load.

[stevieturbo]

If it is mapped badly any engine can use more fuel anywhere.

If it is mapped better, it may not.

[watermoto]

Ah i see. I was wondering as I've read that mapping a car often degrades fuel economy and I was not sure if it was due to the driver using more beans, or the map just degraded the engines efficiency (or both).

Probably should have said that in the first place!

[thebraketester]

Most of the time you will get worse economy because the whole point of remapping a car is to make it fast(er).... you drive it harder and there you have it, worse economy.

[Robmainstgarage]

Out of the 3 Ive had mapped the 2.4tdci 2008 transit got worse 2or3 mpg, the 1.8tdci 2007 focus improved by about 8 mpg, and the 2012 2.0tdi caddy is about the same but seems to doff regents a lot more often, which has now degraded the doff and starting to have issues. Fully intended of have my 2009 t180 RAV4 done this summer but the mobile bloke I've used previously has given up, and there's a lot of cowboy remaps I'd rather avoid!

[anonymous-user]

watermoto said:

Hello.

If an engine is mapped for more power without any other modifications, could the fuel economy get worse for a given load?

For example, two identical engines, one mapped, one factory. Both have the same load and are operating at the same RPM/gearing. Given the RPM and load is the same, then the speed is the same, so the wheel HP must be equal.

In this scenario, is it possible for the mapped engine to be using more fuel?

Just wondering what would cause the mapped engine to run less efficiently, thus use more fuel for a given load.

It depends how it's been mapped. Assuming no physical changes in spec, if the off load and cruise areas of the map haven't been touched it will make no difference to the fuel economy for most of the use of the car.