I've made a mpg improvement with an aftermarket chip. Surprised.

Conor_3

Browntoa wrote: »

and as pointed out, totally invalidates your insurance

Unless you tell them. Not sure what difference it'd make though especially with the alloy wheel fiasco where some will say "no problem" and others whack £50+ on the premium.

Browntoa

meant to add "in the event of a crash and you have not told them" , first thing an investigator looks at

tomstickland

Conor wrote: »

I'm sorry but a 3-4MPG difference is achievable by anyone just by modifying their driving or the driving conditions allowing them to do less slowing and accelerating. Most of these so called improvements end up being down to the driver altering their driving even though they don't realise it.

I'm perfectly aware of the possible factors that might give a misleading impression and placebo effects. This is why I've waited until a suitable opportunity to do a comparison. I've also collected data over a long period of time to give me a good picture. So don't be sorry.

For example, I know I could easily make a similar difference to mpg by varying the amount of acceleration I did, changing the average speed etc. This is why I waited for a long journey on a motorway and payed a lot of attention to the speed.

The car has an instantaneous mpg display, based on ecu injector pulse data and vehicle speed. This has shown an improvement too. I've owned the car for 3 years, so I know what to expect.

Now, the map controls ignition advance and injector pulse timing. In most cases a small performance gain can be obtained by advancing the timing, though the engine will be more sensitive to fuel octane rating. Peak power occurs for an engine at a slightly rich mixture, with a richer or leaner mix giving less peak power. Peak efficiency occurs for a slightly lean mixture. All of this is at wide open throttle though, and when travelling at 80 on a motorway that's not WOT. Hence it is possible to map in some better fuel economy by leaning the mixture slightly at partial throttle angles.
Whatever the changes are, if the original maps were quite far from optimum, there is room for improvement.

I will be doing a back to back test on a rolling road soon.

Either way, I was surprised with the results.

tomstickland

anewman wrote: »

Many of these "chips" are just resistors that wire to some of the sensors and are in fact cost a matter of pence, hence why ebay is full of them. Isn't the best way on most modern cars an ECU re-map?

Yes, this was an ECU eeprom swap, not a resistor that alters the air temperature reading.
A proper rolling road re-map is the best way of optimising the tuning, yes. A chip swap on a normally aspirated engine is usually a waste of time on mdoern cars. I've got a 20 year old BMW though and it's clear that the original map had some room for improvement. I've been quite surprised since I have a low opinion of aftermarket "one size fits all" maps.

tomstickland

Conor wrote: »

Really? A recent TV programme managed more than a 10% increase with a driving course and a 40% increase just by servicing the vehicle.

I've done an economical driving course through one of my former employers. Even though it was aimed at HGVs, I get quite high MPG out of my cars. 55-58MPG out of my Mondeo and 37MPG out of my Capri when others in my club are lucky to be getting 30MPG out of theirs.

It's not difficult.
MPG is clearly related to the amount of work that the engine does whilst the car travels a certain distance.
When travelling at a certain speed a certain amount of drag and rolling resistance needs to be overcome. Hence, roughly, mpg on a flat road is proportional to speed squared.

However, most of the work done is in accelerating the vehicle. If you can maintain momentum by planning ahead and anticipating you can manage a similar average speed with much less acceleration work being done.

I'd expect to be able to drop my mpg massively if I drove quite fast, then braked hard, then stamped on the accelerator, sped up, braked. ie: bungy along a motorway accelerating and braking as much as possible. I'd expect the mpg to drop down to at least 26mpg driving like this.

Similarly, by travelling at 75 indicated and not braking or accelerating at any point I know I can manage more than 40mpg, because I've done it.

Hence why for this comparison I use ROUGHLY SIMILAR conditions. ie: motorway at approximately constant speed around 80 indicated, some traffic, some hills, a few spurts to move out of the way of faster traffic. Considering that I sat almost stationary in traffic for 10 minutes etc and a few other fuel consuming things leads to be impressed with the results.

I really can't be bothered to do a full statistical study over several months.

tomstickland

One other thing....
anyone who rides a bike will understand this.
Most people have no idea about Newton's second law of motion. ie: you only need a force to change the momentum of something. In terms of vehicle, you need a force to get it moving, but after that, at a constant speed, you only need to overcome drag/rolling resistance/gradient weight vector.

What it boils down to is that accelerating is hard work, but cruising at a constant speed is nearly effortless (unless there's a headwind).

You can make massive progress on a bike for very little effort. In busy traffic you quickly learn to plan ahead to avoid having to waste effort.

tomstickland

I found this regarding the AFR (air fuel ratio) values measured using a lambda sensor.

I fitted this chip to my car and it did make a difference. The power increase wasn't what agreen saw with his, but was more like about 6BHP, but then mine before I did anything was already giving 141BHP! The fuel consumption was better too.

Then I Unichipped it as I had a spare chip to use. My Lambda meter went up the shute so I mapped it "blind" while doing fueling. I just mapped it for max power everywhere. The car was much better but the fuel economy dropped to around 25MPG.

When I got my lambda meter back, I found the mapping on my car to be all around 12.8:1. I reset the maps to zero and noted the AFR's with the Evolve chip, alot of the light load sites were on 18:1. Thats pretty lean to say the least, but the car was still smooth. With the Unichip, I set very light throttle loads to 15/15.5:1 making richer to 12.8:1 to full throttle.

"DONT TRY THIS AT HOME!" Before you all go out and buy FSE power valves to adjust your fueling, there were alot of sites which were over advanced at the lean areas, this is obviously done for economy. The car was not det'ing/pinking untill I added fuel, then I needed to retard the ignition on those load sites.

Basically it's been set lean at part load sites and the timing advanced.

Conor_3

Looks like you've found one that's not snake oil then. Cudos to you. However advancing the timing with a lean mix would give you pinking - my capper suffered from it at high revs until I rejetted it for the K&N.

daveyjp

I have done absloutely nothing to my car, but mpg is up around 5 mpg in the last month - now getting high 30s round town, was mid thirties. The fact it is now 20 degrees rather than 5 is one reason, the roads I commute on are also quieter as the holiday season has started so that's another. 4mpg is too small an amount to say its due to a single factor.

tomstickland

Conor wrote: »

Looks like you've found one that's not snake oil then. Cudos to you. However advancing the timing with a lean mix would give you pinking - my capper suffered from it at high revs until I rejetted it for the K&N.

Yes, in general I'd be very wary of chips and the claims made for them, especially on modern engines.
That chap in the link said that pinking was a problem if you increased the fuelling using increased fuel pressure ("power boost valve").