Fuel Economy Improvements.

[Wodjno]

If you assume on a general run you want to maintain a 14.7 compression ratio on cruise, then I fail to see how boosting will improve anything as more air = more fuel.

I think you mean a 14.7 air fuel ratio..

Thing is you can accelerate and still maintain 14.7 AFR..

Boost will not help efficiency unless the car is at a point that it's labouring.. So either an increase in throttle or an change of gear will increase efficiency..


PS.. You cheeky little editor

[orionn2o]

haha to be fair I noticed my own error before you pointed it out !

[Dom B]

If you assume on a general run you want to maintain a 14.7 air/fuel ratio on cruise, then I fail to see how boosting will improve anything as more air = more fuel.

I don't actually mean boost the engine, in fact the last thing i want to do is to force more air and fuel in. What i mean is generate just enough airflow to remove the vacuum and curise at 0psi, thereby removing the pumping losses which are one of the biggest inefficiencies in a petrol engine. In theory the energy to do this is coming from the almost free exhaust energy so you are recovering energy. As long as the waste gate is not opening at this point then the gasses going through the turbine haven't yet reached a high back pressure or al least not high enough to impede the efficiency. Turbos do use bhp to work but no where near as much as a supercharger, but at part throttle they can scavenge lots of useful energy that would normally be sent out the back as heat. Turbo compound engines recover this as mechanical energy we choose to make use of it as boost at higher power/load, however at cruise conditions the vacuum alleviation can help economy too.

[AlanDITD]

Ok dude you seriously have some interesting theories but, whats wrong with just enjoying the car for what it is. And thats a mean fuel guzzling slag of a car.

[Turbo_Steve]

But with reference to economy when cruising you are no where near that knock area so on any petrol the car should be as efficient and running at 100%, remember at cruise is low load.

Pretty much, yes. In fact, what we're talking about here is optimal ignition. As modern engines have "adaprtive"ignition curves, the issue with octane is that and engine mapped for 100RON fuel will have to retard the ignition on any lower octane rating. Thus more throttle will be used, and the car will tend to feel "boggy".

Driving at 0Bar. Again, 100% correct, and most people generally drive at the point where the car is just off boost. Subconciously, they want to feel the power is "just there".
Now, what Wodj describes, whereby you can vary the loading of the engine without a change in acceleration.......this is USUALLY a poor ignition curve, or TPD delta. This is a typical problem running speed density (i.e. MAP based rather than MAF) this can sometimes relate to load translation at the ECU end. Or it can simply be a mapping error: a turbo'd car will usually have a lump in the map in the spooling area, which encourages it into boost asap. Some manufacturers don't do this, as it's also extremely likely to encourage detonation.

Which brings us back to the adaptive ignition: even off boost, the ECU should be seeking to run as much advance as possible to ensure good throttle response, torque and driveability. This means that a lower octane fuel will still record knock, even at partial throttle, off boost.
The VR-4s seem to be quite aggressive at this: varying the fuel octane and staying in closed loop mode still seems to have a significant impact on the economy.

The worstest worst part of all seems to be the throttle change....if you keep varying the throttle position (even in an attempt to maintain constant load) on the standard ECU, the compensation fuelling seems to be stupendously rich.

[Dom B]

Ok dude you seriously have some interesting theories but, whats wrong with just enjoying the car for what it is. And thats a mean fuel guzzling slag of a car.

LOL well i am just the sort of person that just loves to understand everything and try to make everything better. I cannot rest with anything until it makes me happy that it is as good as it can be within the limits of what it is lol. I should probably see a doctor. I love cars and all things automotive. I am actually an automotive engineer and run an engineering business too so i am the insatiable tinkerer. The legnum is pretty new to me so i am learning learning learning then i want to apply what i learn alongside my own theory and general known data to make lots of shiny bits for our lovely cars.

As for richness on any throttle movement. The car seems to bump to 11:1 afr as soon as you sneeze on the loud pedal. Just moving the car around here i get gassed by the petrol coming out of the exhaust. I was going to put a bucket on the end of the exhaust so i could pour it back in

[vr4-fan]

well , my car defintly , dont give me more than 10 MPG , I dont understand , I am very mad with this shi.t , I going to reset the ecu , I remove the baterry for see waht happen

[Turbo_Steve]

vr4-fan, as discussed, you need to do more diagnostics:

1) Wideband lamda - get a probe up the tailpipe and see if it's running rich at idle. If it is, you need to look for exhaust leaks, vacuum leakes and perhaps a faulty lambda sensor.

2) EvoScan. You need to either get a Mitsubishi Dealer to look at the ECU output, or to buy and plug in "EvoScan" on your laptop. This will let you monitor what the engine is doing in realtime.

3) Become a member of Clubvr4. It's not expensive, you get a discount on Amsoil and there are lots of helpful articles in the club section that you could read for more advice on things like EvoScan.

[vr4-fan]

vr4-fan, as discussed, you need to do more diagnostics:

1) Wideband lamda - get a probe up the tailpipe and see if it's running rich at idle. If it is, you need to look for exhaust leaks, vacuum leakes and perhaps a faulty lambda sensor.

2) EvoScan. You need to either get a Mitsubishi Dealer to look at the ECU output, or to buy and plug in "EvoScan" on your laptop. This will let you monitor what the engine is doing in realtime.

3) Become a member of Clubvr4. It's not expensive, you get a discount on Amsoil and there are lots of helpful articles in the club section that you could read for more advice on things like EvoScan.

[AlanDITD]

Mate if your getting 10mpg, the cost of all those things steve mentioned would be rcouped pretty quickly if you started getting 25mpg.

Personally i would get the wideband first. Well after you have become a full member.

[vr4-fan]

Mate if your getting 10mpg, the cost of all those things steve mentioned would be rcouped pretty quickly if you started getting 25mpg.

Personally i would get the wideband first. Well after you have become a full member.

all you , thnks , that my car is overfuel?

[fluffnik]

Ok dude you seriously have some interesting theories but, whats wrong with just enjoying the car for what it is. And thats a mean fuel guzzling slag of a car.

The less fuel you use cruising, the more you have left for blatting...

[Wodjno]

The less fuel you use cruising, the more you have left for blatting...

So to Live at the top of Pikes Peak and Work at the bottom what be perfect then

[Turbo_Steve]

all you , thnks , that my car is overfuel?

At 10mpg below 2400rpms, we think you might have a hole in your petrol tank!

[AlanDITD]

Dom i did a check today, at 90mph on a private track, i was stting at 10ihmg

That was just cruising, could have got it to a bout 12. Any more was accelerating and any less droppping in speed.

[statham234]

when i bought mine someone said to me" whats it like on fuel" reply when its empty i fill her up not even interested on mpg

[PaddyB]

10 MPG strongly suggests that something is snafu. FYI: When I drive like an old lady the COTY will just sneak >30MPG - this goes down to <14MPG when I go a bit mental for a tank .

[vr4-fan]

: I want to check in winband , because all you take more than 20 mpg

[Subaru ETA]

well , my car defintly , dont give me more than 10 MPG , I dont understand , I am very mad with this shi.t , I going to reset the ecu , I remove the baterry for see waht happen

you keep asking for advise, but you dont listen to it!! you just keep complaining but not listening!!! (is vr4-fan pitslayer using a different user name? )

[elnevio]

when i bought mine someone said to me" whats it like on fuel" reply when its empty i fill her up not even interested on mpg