Skylined
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Registered: 27th Sep 05
Location: Sideways, Surrey
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So I have an Astra GSi, which on a long run can easily get 35mpg+ cruising at 70mph.
I've been told that if I get it mapped, then overall the engine is capable of producing more power, so it will use less power than it currently does when driving normally, making it more fuel efficient.
How come then, that an Evo/Scooby with a 2l turbo engine can only manage 25mpg when cruising? Theoretically it produces a lot more power so should be more economical when you're not giving it the beans, and the turbo kicks in a lot later on these so won't be spooling much at 70mph.
Help please 
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Steve
Premium Member
Registered: 30th Mar 02
Location: Worcestershire Drives: Defender
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i think these claims of fuel saving performance increasing remaps is marketting nonsense, to produce more power the engine will need to burn more fuel, the end.
i think it was basically justified by saying things like when overtaking you wont need to drop down or cane it so much
[Edited on 02-12-2010 by Steve]
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Neo
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Registered: 20th Feb 07
Location: Essex
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You say that steve, but after my Map my MPG went up about 5/6 average per tank.
O.P. I think its more that a 2l with around 150bhp mapped to 160/170 will make it slightly more efficient. When you start talking big figures there is no way of getting round it. The engines in evo's/scoobys will have bigger injectors so the amount of fuel you will use to begin with will be more than a 2ltr mondeo for example.
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Scotty C
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Registered: 6th Nov 05
Location: Kidderminster Drives: 1.6 16v Sport
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So why don't manufactures do it as standard? Not only can they advertise the fact the engine produces more bhp, thus getting to 60mph quicker and it's better on fuel.
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Robo C20Let
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Registered: 22nd Feb 10
Location: Somewhere inside your mom !!!
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if i got 25 mpg out my evo i would be happy but i never do i have done 300 miles on £100 worth of fuel
[Edited on 02-12-2010 by Robo C20Let]
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corsa_nation
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Registered: 27th Dec 04
Location: Wiltshire
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quote:
Originally posted by Scotty C
So why don't manufactures do it as standard? Not only can they advertise the fact the engine produces more bhp, thus getting to 60mph quicker and it's better on fuel.
Maybe because the power they come out of the factory with is most suitable for the mechanical components of the car in question.
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Jamie Walby
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Registered: 15th Nov 04
User status: Offline
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I get 15.1mpg no matter how hard or gently I drive.
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Scotty C
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Registered: 6th Nov 05
Location: Kidderminster Drives: 1.6 16v Sport
User status: Offline
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quote:
Originally posted by corsa_nation
quote:
Originally posted by Scotty C
So why don't manufactures do it as standard? Not only can they advertise the fact the engine produces more bhp, thus getting to 60mph quicker and it's better on fuel.
Maybe because the power they come out of the factory with is most suitable for the mechanical components of the car in question.
True, but a mapping it for another 20bhp - 30bhp for increased mpg wont hurt the internals
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Jake
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Registered: 24th Jan 05
User status: Offline
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insurance and reliability
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Steve
Premium Member
Registered: 30th Mar 02
Location: Worcestershire Drives: Defender
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still fact remains, you cant get more power without burning more fuel, not when it comes to remaps anyway
[Edited on 02-12-2010 by Steve]
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AK
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Registered: 5th Jul 00
Location: Aberdeen City
User status: Offline
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Here's my take on diesel mapping and greater MPG.
The onboard 'puter thinks fuel is going in at a specified rate... so does its calculations based on that.
when mapped more fuel with be getting used... confusling the MPG
[Edited on 02-12-2010 by AK]
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Robin
Premium Member
Registered: 7th Jan 04
Location: Northants Drives: Clio 182 Cup
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Mine gained mpg, worked out using the pump figures, miles and a calculator, not the trip computer.
It's all to do with the most efficient use of the fuel available, with more power, my car was using more air and fuel under full load, but at cruising speed, uses slightly more fuel, which it burns better, meaning more power at the same revs, thus less revs needed and less fuel used.
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corsa_nation
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Registered: 27th Dec 04
Location: Wiltshire
User status: Offline
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quote:
Originally posted by Scotty C
quote:
Originally posted by corsa_nation
quote:
Originally posted by Scotty C
So why don't manufactures do it as standard? Not only can they advertise the fact the engine produces more bhp, thus getting to 60mph quicker and it's better on fuel.
Maybe because the power they come out of the factory with is most suitable for the mechanical components of the car in question.
True, but a mapping it for another 20bhp - 30bhp for increased mpg wont hurt the internals
Surely in the long run the internals that have been selected in said vehicle have a greater lifespan with the factory map, any extra power is going to reduce the life of certain components by 'X' amount of time whether it increases the mpg or not.
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Neo
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Registered: 20th Feb 07
Location: Essex
User status: Offline
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This might be complete crap but when my car was getting done one of the engineers was telling me about how they can get more power by remapping and why it doesnt come out like it at standard spec.
When a car is made, they don't have a seperate map for each country, just one generic map. This has to be able to withstand the cold in iceland for example as well as the heat in spain/south africa etc. Some countries have massive changes in temp and climate so the car has to be all round set up. We have neither extreme hot or extreme cold in this country, so you can afford to change the map without worrying the engine is going to overheat etc.
I'm not a grease monkey so don't quote me, just repeating what an engineer briefly explained to me.
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Matt L
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Registered: 17th Apr 06
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since mine was mapped my mpg has increased by around 5 per tank and i know a few people with evos that since they have had theirs mapped it has increased the mpg too.
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John
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Registered: 30th Jun 03
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You going by calculations or computer Matt, every vag I've had mapped throws the computer miles off.
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flybikeslee
Member
Registered: 2nd Jan 07
Location: Liverpool
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quote:
Originally posted by John
You going by calculations or computer Matt, every vag I've had mapped throws the computer miles off.
same, my computer says im doing 60mpg when worked out its more like 35
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Skylined
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Registered: 27th Sep 05
Location: Sideways, Surrey
User status: Offline
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quote:
Originally posted by Neo
The engines in evo's/scoobys will have bigger injectors so the amount of fuel you will use to begin with will be more than a 2ltr mondeo for example.
So it's to do with the overall capability of the engine?
They come with bigger injectors which are incapable of being fuel efficient? Do they give out a minimum fuel load every time?
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sand-eel
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Registered: 15th Mar 07
Location: carluke/braidwood--IRNBRULAND
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quote:
Originally posted by Steve
still fact remains, you cant get more power without burning more fuel, not when it comes to remaps anyway
[Edited on 02-12-2010 by Steve]
Advance the timing = no more fuel and more bhp 
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Steve
Premium Member
Registered: 30th Mar 02
Location: Worcestershire Drives: Defender
User status: Offline
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i was waiting for someone to bring up timing advancment, thats all well and good but generally most engines are setup with the timing pretty much as much as it can go before pre ignition, as this is the most fuel efficient setup.
you can tweak it a bit but you wont get much if any
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Neo
Member
Registered: 20th Feb 07
Location: Essex
User status: Offline
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quote:
Originally posted by Skylined
quote:
Originally posted by Neo
The engines in evo's/scoobys will have bigger injectors so the amount of fuel you will use to begin with will be more than a 2ltr mondeo for example.
So it's to do with the overall capability of the engine?
They come with bigger injectors which are incapable of being fuel efficient? Do they give out a minimum fuel load every time?
To get the amount of power out of a 2ltr subaru engine, it will be using more fuel than a 2ltr mondeo for example. Same size engine but using more fuel/air, larger injectors etc etc etc to make the power gains.
I would need to do some research to be sure about the injectors ability of being "fuel efficient" but i'm sure someone on here will know for certain.
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sand-eel
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Registered: 15th Mar 07
Location: carluke/braidwood--IRNBRULAND
User status: Offline
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quote:
Originally posted by Steve
i was waiting for someone to bring up timing advancment, thats all well and good but generally most engines are setup with the timing pretty much as much as it can go before pre ignition, as this is the most fuel efficient setup.
you can tweak it a bit but you wont get much if any
advance the injector timing on a deisel = no more fuel + more bhp
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Toby
Premium Member
Registered: 29th Nov 05
User status: Offline
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quote:
Originally posted by Scotty C
quote:
Originally posted by corsa_nation
quote:
Originally posted by Scotty C
So why don't manufactures do it as standard? Not only can they advertise the fact the engine produces more bhp, thus getting to 60mph quicker and it's better on fuel.
Maybe because the power they come out of the factory with is most suitable for the mechanical components of the car in question.
True, but a mapping it for another 20bhp - 30bhp for increased mpg wont hurt the internals
may hurt with insurance and threrfore leaving the car outside its target market hence the two CDTi vaux engines at 120bhp and 150bhp same enigne etc
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Simon_16v
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Registered: 14th Aug 06
Location: Yorkshire
User status: Offline
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A remap knocked my insurance up £20
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LeeM
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Registered: 26th Sep 05
Location: Liverpool
User status: Offline
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On petrol engines the map is the same on every engine but all the engines will be slightly different. When it's mapped on a RR it's tailored exactly to that engine.
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