What is remapping? Is it really beneficial?

[Mcardp01]

I have an e320cdi.....just curious as to this remapping and software update on the ECU I think......

 

[evdok]

Is this good enough?

Convinced?

 

[Rashman]

lol, is this "confuse the hell out of members" night?!

 

[evdok]

Possibly

 

[normanh]

Convinced?

Can you explain what we're looking at

 

[BigSilverEstate]

I think they are before and after pictures - not much impact on fuel economy from the remap but it was responsible for a 3.5 degree increase in outside temperatures

 

[evdok]

Can you explain what we're looking at

I am highlighting MPG.

 

[Lord-WYBMAnE220]

You really need to do a litreage/receipt analysis of economy.
Indicated economy can be pretty wide of the mark after a remap, since the ECU thinks injectors are still passing the same quantities of fuel.

It's easy to shorten engine life with a remap - since mapping is an exquisitely complex proposition that even for manufacturers is as empirical (suck it and see) as it is scientific.
The dynamic interplay of so many parameters makes it a very dark art.
Remap at your engine-longevity's peril.

 

[Deleted member 37751]

it was responsible for a 3.5 degree increase in outside temperatures

So remapping your car causes global warming?

 

[b1g1an]

Driving style can give the biggest improvements or vice versa... I had 25.6 mpg showing after 150 miles of a recent journey and just two nearly WOT runs up to only 80 off a couple of roundabouts immediately knocked the average down to 23.2, which is approx 10% difference, and it only made it back to 23.5 over the final 50 driven as I did originally.

Remapping is most successful at improving drivability as well as increasing power to a lesser or greater extent and that then encourages you to stand on the throttle a bit more often so real economy is often worse.

 

[Somebody]

Basic description of re-mapping.

The ECU has a lot of data in it on how to control fuel input according to different conditions. It measures ambient temperature, engine temperature, air inlet temperature, air inlet volume, manifold/boost pressure, the composition of exhaust gases, engine knock level, speed, throttle position, etc etc (depending on system).

It has a giant table/database type thing which basically tells it how much fuel to give under each of these conditions. This is known as the 'map'.

So, a very simplified way to explain it, every tiny fraction of a second, the ecu thinks ''boost pressure is 0.5, air flow is 2.1, throttle position is 43%'' and then it looks up in it's giant database thing to tell it the correct fuel level for those parameters. It does that hundreds of times every second.

Manufacturers spend millions developing the correct map for any given engine, however then other 3rd party companies come along and develop new maps, this is called re-mapping.

Re-mapping has two uses:

One use is to change the engine's operating parameters to suite other modifications. For example, if you fit a high performance exhaust, high performance air cleaner, port the head, use bigger valves and fit a bigger turbo, the stock map will not apply enough fuel, since the engine will have more breathing capacity than the ECU is programmed for. Similarly, if you increase injector size, it will over-fuel, since the stock ECU will think it's using stock injectors, and bigger injectors flow more fuel for a given pulse.

Another much more common use for remapping is trying to squeeze more power out of a stock engine without changing anything apart from the map. This is done all the time by almost everybody, but comes with downsides.

Engine manufacturers spend a loooot of money developing maps, and the maps they come up with is usually a perfect compromise between drivability, economy performance and reliability. With any kind of car tuning, you can only pick two out of the three: Economy, power, reliability. You can never have all 3. So usually remapping a stock engine increases something but decreases something else. So the chances are, when you increase power output, you will defiantly hurt economy or reliability, since there is no such thing as free stuff.

You can have big power gains from remaps, but the engine will drink fuel and wear out much quicker.

The only exception is cars which got released after a really rushed production run, and there was so much pressure to bring the car to the sales floor that the manufacturer havn't finished developing decent maps for it. In those cases, re-mapping can genuinely improve everything.

But, unfortunately, car manufacturers aint stupid usually, its pretty rare for them to be stupid, and also there is no such thing as a free lunch.

 

[Mcardp01]

Basic description of re-mapping.

The ECU has a lot of data in it on how to control fuel input according to different conditions. It measures ambient temperature, engine temperature, air inlet temperature, air inlet volume, manifold/boost pressure, the composition of exhaust gases, engine knock level, speed, throttle position, etc etc (depending on system).

It has a giant table/database type thing which basically tells it how much fuel to give under each of these conditions. This is known as the 'map'.

So, a very simplified way to explain it, every tiny fraction of a second, the ecu thinks ''boost pressure is 0.5, air flow is 2.1, throttle position is 43%'' and then it looks up in it's giant database thing to tell it the correct fuel level for those parameters. It does that hundreds of times every second.

Manufacturers spend millions developing the correct map for any given engine, however then other 3rd party companies come along and develop new maps, this is called re-mapping.

Re-mapping has two uses:

One use is to change the engine's operating parameters to suite other modifications. For example, if you fit a high performance exhaust, high performance air cleaner, port the head, use bigger valves and fit a bigger turbo, the stock map will not apply enough fuel, since the engine will have more breathing capacity than the ECU is programmed for. Similarly, if you increase injector size, it will over-fuel, since the stock ECU will think it's using stock injectors, and bigger injectors flow more fuel for a given pulse.

Another much more common use for remapping is trying to squeeze more power out of a stock engine without changing anything apart from the map. This is done all the time by almost everybody, but comes with downsides.

Engine manufacturers spend a loooot of money developing maps, and the maps they come up with is usually a perfect compromise between drivability, economy performance and reliability. With any kind of car tuning, you can only pick two out of the three: Economy, power, reliability. You can never have all 3. So usually remapping a stock engine increases something but decreases something else. So the chances are, when you increase power output, you will defiantly hurt economy or reliability, since there is no such thing as free stuff.

You can have big power gains from remaps, but the engine will drink fuel and wear out much quicker.

The only exception is cars which got released after a really rushed production run, and there was so much pressure to bring the car to the sales floor that the manufacturer havn't finished developing decent maps for it. In those cases, re-mapping can genuinely improve everything.

But, unfortunately, car manufacturers aint stupid usually, its pretty rare for them to be stupid, and also there is no such thing as a free lunch.

Ok I think I understand the mapping. Now I have read in lots of articles about updating ECU software or is this the same as remapping?

 

[Somebody]

It can mean the same thing, but usually means generally updating it to current spec, kinda like updating your phone, just installs the latest software on it, which has small tweaks and fixes and stuff. Sometimes it involves new maps sometimes it doesn't.

 

[HumberMart]

Fair summary, Somebody.

The only issue I'd like to add a little to is question the assumption that the OEM maps are generally optimum.

They are of course a 'one size fits all' map and this will not be optimum for every user.

However the main problem is that the maps are not optimum, but are designed to get max mpg and less CO2 readings on the official tests.

This does not mean a perfect compromise as suggested. The truth is that OEM maps are not the best balance between power, economy, and reliability in real world use.

 

[V12]

Fair summary, Somebody.

The only issue I'd like to add a little to is question the assumption that the OEM maps are generally optimum.

They are of course a 'one size fits all' map and this will not be optimum for every user.

However the main problem is that the maps are not optimum, but are designed to get max mpg and less CO2 readings on the official tests.

This does not mean a perfect compromise as suggested. The truth is that OEM maps are not the best balance between power, economy, and reliability in real world use.

I disagree.

 

[Lord-WYBMAnE220]

Fair summary, Somebody.

The only issue I'd like to add a little to is question the assumption that the OEM maps are generally optimum.

They are of course a 'one size fits all' map and this will not be optimum for every user.

However the main problem is that the maps are not optimum, but are designed to get max mpg and less CO2 readings on the official tests.

A shot in the dark here - but I'm guessing you've had yours remapped.
The only way to reduce CO2 output is to reduce engine size.

Reducing CO2 output means increasing C (or soot) and CO output - the undesirable and polluting products of incomplete combustion.

You really need to get up to speed on the basics of ICE chemistry here.

 

[moff]

I disagree.

Why?

 

[V12]

The Idea that MB or any other manufacturer is sacrificing performance or reliability for the sake of MPG is rubbish.
Admittedly there are some eco boxes around now that are solely designed for mpg with no consideration of performance, these are extremely rare and probably account for a tiny (yet growing) portion of the market.
If someone purchases the eco model, they're not worried about performance, if they purchase the "hot" version, they're probably not too concerned with mpg. 99% of users and cars on the road sit between any extremes and are a perfect balance.

It's just my opinion. I've never believed that some guy with a laptop can create a more balanced map than the manufacturer who understands all of the workings of every system.

Most mapping shortens engine life and decreases MPG in the real world.

People like to feel good about wasting hundreds of £££s, so they come onto internet forums to tell us all about how good the car now feels. No one ever substantiates their claims. That is worrying.

When someone comes on here wanting to remap their 2.0 diesel because they're dissatisfied with the performance, they have purchased the wrong car to begin with.

All in my opinion of course.

 

[Spinal]

From what I know of CO2/MPG tests, most producers carry them out with custom maps - not the production maps used for the cars on sale...

That said - I do believe manufacturers will operate within a safe margin; so you may be able to eek out a little more performance out of the engine... at the risk of compromising the reliability...

 

[Lord-WYBMAnE220]

From what I know of CO2/MPG tests, most producers carry them out with custom maps - not the production maps used for the cars on sale...

Are CO2 emissions independently tested for every model-type ?
I'm guessing they must be, for taxation purposes.
But they're hardly critical to sales figures - unlike MPG claims.