The benefits of road testing modifications

Posted on November 27th, 2005 in Opinion by Julian Edgar

Yesterday I did some serious testing. Well, ‘serious’ as in I set out to specifically test and fine tune the air/fuel ratios in my project car.

Despite frequently writing that you should always have an assistant in the car to read gauges and hold hand controllers and make tuning decisions, I must admit that circumstances often force me to do it all myself, as I am driving. (I am cognizant of the dangers involved in doing this; once many years ago while on-road tuning, I ran straight into the back of a car that had unexpectedly stopped.) So yesterday, for the fine tuning, I did in fact sit in the passenger seat. My lady drove the car and our little boy was in the back.

Despite needing to use full throttle as part of the tuning process, the performance of the car (a turbo hybrid Prius) is so slow that it can all be done on open public roads without breaking the law or posing danger to anyone.

While setting-up this car I have at times run numerous in-car instruments, but on this occasion they were limited to a  MoTeC air/fuel ratio meter running from a tail-pipe mounted probe, an LCD intake air temperature display, a LED indication of factory oxy sensor output, and an LCD hand controller connected to a Digital Fuel Adjuster kit. I also brought along a screwdriver and spanner to allow me to adjust the high and low fuel pressure regulators (this car uses a system that switches out the closed-loop oxy sensors and simultaneously switches in higher fuel pressure). A smaller screwdriver was also carried that could be used to adjust the switch-over point between fuel pressures, a change which is triggered by a Simple Voltage Switch kit monitoring airflow as measured by the airflow meter.

The first step was to check intercooler efficiency. While I had previously measured intake air temps, I’d only done so with the front bumper and number plate off the car. I’d physically felt the temperature of the plumbing after driving the car hard, but hadn’t quantified the numbers. And I must admit, watching the LCD temperature display, I was appalled. Initially, on the long trip down from the hills on which we live, the temp had stayed low – about 10 degrees C above the 20 degree ambient. But then, whenever boost was called upon, the temperature rocketed. Like, it would rise to 20 degrees C above ambient after just a few seconds of boost, and 40 degrees C above ambient after perhaps 10 seconds of boost!

When getting good fuel economy doesn’t mean driving like a tosser

Posted on November 13th, 2005 in Opinion by Julian Edgar

The stories we ran a few months ago on getting best fuel economy included one on driving techniques (see Savings on Fuel – Part Three). None of the techniques mentioned were startling or new; if you read pretty well any of the books on driving published over the last hundred-odd years, you’ll find mention of being smooth, ‘reading’ the traffic flow, rolling up to halts rather than braking at the last minute, and so on.

And while they might not be new ideas, they’re still certainly quite valid when it comes to getting best fuel economy.

Another characteristic of those habits is that they all fall into the category of ‘good driving’. It doesn’t really matter what vehicle you’re pedalling – whether it’s a huge prime mover or a tiny economy car or a turbocharged rocketship – all will respond favourably to these driving habits… habits which will cause little or no concern to other drivers. In fact, you’re much less likely to have accidents if you drive in these ways.

I kinda took that symbiotic relationship for granted – good driving, low accident rate and better economy – until I was rudely awakened by discussion of an ‘economy’ driving technique that seems custom-designed to infuriate other road users… and simply could never be described as good driving.

Thankfully, it’s currently not a widespread practice, is limited to just one type of car, and is pursued by those who can only be – quite charitably – referred to as tossers.