Hi All,

Possibly a daft question......!!

Is it possible to get an ECU re-map to get better MPG out of MY55 STI rather than adding extra BHP?? Of course I do not want to loose any BHP either

With petrol prices so high its worth a thought!!

Cheers

ScoobyLee2000

 

After my 54 plate STI was remapped by TSL for a power increase it also became more fuel efficient.JAY

 

Hi Jay, how extra MPG do you think you get? Cheers

 

cheaper to stick a block of wood under your accelerator pedal

 

setting the ecu up correctly for the specific car rather than the generic map usually sees better mpg as well as the power increase.

Simon

 

You could fit a boost controller to limit boost, but just learn to drive more smoothly, and put some calm music on.... LOL

Works in my mini-bus, NOT in my Scoob !

DunxC

 

If a re-map costs you £500, it will take quite some time/miles to return that cost through any saving in fuel.

The laws of physics cannot be re-written by a re-map. More power means more fuel burnt.

 

As said, the money for a remap may take time to gain back.

I tried driving off the Turbo for a tank of fuel. Normally I get 20-22mpg (MY05 STI PPP) and that taking easy to work, slightly quicker on the way home again. Now, driving off the Turbo got me 27mpg. An improvement, yes, but I won't be doing it again. It was painfull accelerating soo slowly. Happy with 22mpg now.

I thought of selling the car too, but once I'd priced up what I would replace it with, the money I'd shell out on trade-in/buying etc as well as plate transfer (private plate) it meant that it would take years to get back the odd thousand pound over the fuel I use now.

 

You have definately bought the wrong car if you are worried about MPG! I know what you mean though, I only get around 220 miles out of a tank and that's driving steady. Annoying but hey...



Oh, and I'm getting mine mapped very soon so should see if its better MPG or not?!

 

not the case I am afraid..

standard fuelling often drops into the 10:1AFR.. which is well beyond best power.. so if you do nothing other than reduce the amount of fuel being injected within safe margins you gain power.. it is very easy to see if the injectors are open for less time within the compression stroke you will use less fuel.. and with the standard map being so rich.. you will gain power.

Although infact you are correct.. in that a higher percentage of the fuel injected is actually burnt and more power is produced rather than passing out of the tail pipe unburnt due to overly rich mixture but I suspect you were not looking at it in this much depth? and of course it has still left the fuel tank.

I can get around 31mpg out of my car.. which makes 450bhp.. but I can also get 16mpg.. just depends on my mood

Simon

 

The 31mpg comes in when half the journey is downhill with a following wind I presume

Does the Impreza engine inject only when required into each cylinder?

I still maintain that you cannot get extra power and cut fuel consumption - my Engineering studies tells me quite clearly that the only way to extra power is to burn more fuel ....... given that everything else remains the same.

 

I am looking into engine mapping (very basically at the moment!) but it is possible to have an engine map that is ideal for MPG which would change the AF ratio, this as said would be better than a generic map, but to keep the power, it would be best to get someone good to map the car perfectly, this way the fuel will be used in the most efficient way the engine can and therefore make the most of the fuel.
You could also invest in a switchable ECU and have both maps on, but as said, it would take a long time to see a return on fuel prices.
Maybe this is of any help at all. (and i hope it is true!)
Tom

 

you could always fit a wideband instead of the standard lambda and alter the voltage slighlty so cruise afr is more like 15:1 as apposed to the 14.7

(you may be able to adjust the standard lambda to do this - depending on the mapping software)


....remember most of the time the car is in 'cruise' mode so maybe you should look into that.
manufacturers map std cars to run a afr of 14.7 when cruising, this is for best emmissions and not best fuel economy.....you can go leaner!

 

But don't go too lean, otherwise you will cause knock! And we don't want that now do we?!

Tom

 

no 70~80mph cruise..

I guess you should have studied harder then

 

 

not on cruise.. yes if you lean it out as it comes up the load, but at cruise it will just hessitate if too lean

15~15.5:1 is usually okay

Simon

 

That's a little cheeky, but I'm sure it was all in jest!!

I get the impression that Uncle Pester doesn't realise who he is talking to, or, judging by the username, perhaps he is someone we should be looking to ignore (I hope not).

Anyway, Uncle Pester, JGM knows his stuff, check out www.jollygreenmonster.co.uk, when I've saved a few pennies I hope to utilise his skills for a few more horses and a few more mpgs!

 

was meant totally in jest and I hope he doesn't take offence, as it wasn't my intension.

you also find that a car with more power uses less fuel because to get to the speed you want to be at when driving normally it uses less throttle and less time is spent on boost etc..

Simon

 

Like JGM, my car too has suffered the strange side effect of better mpg and increased power.

 

the fuel cut is configurable and in the standard ecu it doesn't inject fuel on overrun so down hill off the throttle will not inject fuel.

the standard generic map is fairly rich.. so just be removing a little fuel it will make power

 

This explains statement that it is more fuel efficient to coast in gear rather than in neutral - I never understood it before (or believed it), I generally find it needs to be a fairly steep hill to stop the engine from actually slowing me down though, e.g. it doesn't work coastbound on M20 between Wrotham and the bottom of the hill.

Thanks for clearing that up for me - learned my new thing for the day just before time!

 

when you can smell the vpower comming out the exhaust me thinks perhaps your not getting the best fuel usage.

sort out the correct mix then your not throwing fuel away unused

 

With the Ecutek remap you can have a high/low boost toggle. If you're prone to nailing it, keep it in low.

The remap will give you better fuel economy though. Mine did, from 220 to now about 250. Of course if you gun-it, that will be the opposite.

 

Simon - providing you were disciplined and kept off the throttle, could you advance ignition globally while motorway cruising (using something like PSI3) and gain extra economy without det or risk to the engine?
Cheers, Andrew

 

You are working on the presumtion that all the fuel injected is burnt, which is not the case on boost or under load, where extra fuel is injected to help with cooling and reduce the chance of det. On the stock map, a lot of excess fuel is injected. As JGM has mentioned, removing some fuel in certain areas of the map will cause a more efficient burn, reducing fuel consuption and yielding more power while still remaining within safe limits for the engine.

 

I don't think small amounts of det are a problem at all at low loads.

I'm sure you've had old non turbo cars over the years that you can 'hear' detting/pinking (takes me back to my metro days.....sshhh) but these old things run forever without a problem!........but obviously they dont get anywhere near the load values of a turbo car.

(there a few guys in the states at the minute that are working on a map to shut down 1 cylinder on cruise (on evos), how close they are or even if they can do it I'm not sure.)