techathy's Forum Comments
Showing all comments by techathy.
Suggestion: Show Mileage
Unfortunately in my experience mileage has little effect on economy it's actually engine care. When driving in a group/convoy, ie same driving conditions, you often find that the most economical cars range from almost new to well over 100'000 miles on the clock. Talk to the owners however & most of the big mpg cars are home serviced.
posted by techathy November 6, 2009 at 1:32 AM
Is all diesel gas created equal?
The quality of the additives in the fuel has a strong effect on the quality of the fuel. What you tend to pay for with the premium brands is less of more expensive additives & some/better detergents. So yes while Tesco's 99 RON fuel is higher octane than Shell 98 RON, however the Shell fuel gives you more energy for the same volume (it's up to the ECU to work out if you can take advantage of that however) & the same applies to diesel.
posted by techathy October 21, 2009 at 7:20 AM
Correction for tire/rim sizes?
It's easy enough to approximate the difference (your trip & odometer are hardly precision instruments them selves!). You need to know the % difference between the tyre profiles then apply that to the mileage. A quick n' dirty way is to use the tyre profiles, tread width is divided by the profile as a % then doubled & applied to the wheel diameter. If we take 195/45R15 then we get:
195*0.45*2/25.4+15=21.91" Ø
(the 25.4 is covering millimetres into inches)
Say I'm going to move to 195/40R16 tyres I have the result 22.14"
You then use the two numbers you got to get the difference in %, 1.05% in this case. So I'd add 1.05% to my mileage total.
posted by techathy October 10, 2009 at 4:35 AM
Octane rating on Fillup?
Other thing is doesn't the US use MON at the pumps & the EU RON octane? That means my usual 98RON is the equivalent of 90MON fuel in the US.
posted by techathy October 7, 2009 at 10:02 AM
Engine size + RPM + MPH = Best MPG?
The thing you're also neglecting in your theorising lower rpm at the same speed = better economy is relative engine load. Also you're almost never on a perfectly flat, perfectly straight road, well in the UK anyway. Then you have to quantify when the ECU goes from closed loop cruising mode to open loop acceleration mode & that throws a spanner in the works too.
If you ignore the fiat figures for the latter 1.1 Seicentos & look at actual mpg on the road you find the LOWER geared Sporting at 60mph returns slightly better fuel economy than the non-sporting (same engine different 'box) models. Why? When laden or going up noticeable gradients the throttle is opened much further on the non-sportings as simply put the gearing is to high. More than that the most economical way to get up a 1:5 or steeper hill is to spin the engine to around 5000rpm! Driving at 60 in 5th & revving when going up a 20% or steeper incline was delivering high 50mpg to low 60mpg, but I'm talking about a free-revving 1108cc in a 800kg car that'd happily red-line with 50% throttle in 2nd.
If we look at my Panda, 1.4 16v turbo unit (home brew turbo conversion) in a 1000kg car, the best way to make progress under high load conditions, this also means accelerating, is to keep it at an rpm as low as possible with the turbo producing 0bar (relative) pressure. With loads of torque low in the rev-range for the chassis weight & a very nice piece of boost control you can use this torque to push you on with little effort.
On the Fiat 500 Abarth, the official 1.4 16v turbo, that doesn't have anywhere near as good a boost control system you're better off trying to keep the turbo off-boost until the engine can't cope then letting the turbo supply some boost but not a lot.
3 cars & 3 different ways to get the best economy out of them. In short is there are no hard & fast rules for every car, you have to work it out per-car. Personally I've seen that keeping an petrol engine much bellow 2000 rpm in high gears is a way to increase fuel usage latter in life & all fuel usage gains wiped out by premature big end failure (engine rebuild or new car time). Diesels rev lower & have different bottom end tolerances to cope with this, but I've not looked into oil burners.
posted by techathy September 16, 2009 at 2:49 PM
Premium gas for 2010 Honda Insight
If you want to spend more money on your fuel go for a high quality brand at the octane given in your owners manual.
Higher octane fuel can be of benefit to deliver a higher degree of spark advance without detonation which may increase performance & also may allow the engine to be run leaner on cruise before detonation occurs. Typically a factory mapped ECU won't take advantage of this, which means you're just wasting money on fuel you can't take advantage of. I have, however, seen cars gain performance & economy from running higher octane fuel after being remapped.
posted by techathy September 9, 2009 at 10:47 AM
Location filter?
From my understand H4 (aka F4) are horizontally have opposed banks of cylinders. L4 (or I4) engine are in-line 4 cylinder engines which are exactly as described really, all the cylinders are in a line.
posted by techathy September 5, 2009 at 9:16 AM
It's your call but I wasn't talking about people from a Japan on the site I'm talking about personal imports 2nd hand from Japan, 5 out of 7 cars I've owned were built for the Japanese market. Due to the Japanese vehicle testing system a large number of common Jap spec cars make their way into the UK because it's simply better to sell & export a perfectly road worthy than do the required maintenance work (things like replacing the entire brake system from the ground up with new parts). The Jap' spec machinery can be radically different for the same model compared to the European version.
posted by techathy August 26, 2009 at 5:19 AM
There is a certain amount of target geographical market tailoring for a model of car & what messes things up even more is importing. Afaik there's a fair number of Jap market cars in the UK which are made to different specs than their equivalent officially imported UK counterpart, these cars can't be compared to US or European models directly. So maybe a country of origin field would be good idea for now?
posted by techathy August 25, 2009 at 10:33 AM
Tell us about your 'Cash for Clunkers' experience.
Scrappage is working because it's also physiological & people are spending more on a new car to get the 2 grand discount. It's a bone to people who buy a nearly-new car & then run it into the ground, the scrappage is an incentive to buy a new car now while they get money for their otherwise worthless car regardless of spending more. I know of several people who kept right dogs of cars going for a few months when rumours of this scheme started so they could get a new car instead of a 6 month old demo car.
posted by techathy August 17, 2009 at 11:44 AM
What is the most efficient DRIVING SPEED? I have a Toyota Aygo ( and a Citroen Xsara Picasso)
Typically found that the Panda used to like about 2300rpm in any gear, where it got a nice torque spike, great for 50mph limits but was dangerously slow on dual carriage ways (if lorries want to over take you, you're driving dangerously!). The other rpm the engine liked to be around was the 3300 maker, a bit under 70mph, at that rpm the throttle input to keep the speed up hill was small, meaning the ECU didn't drop to open loop mode (meaning the ECU is primed for acceleration & runs the ARF rich rather than slightly lean, reduced fuel economy), while keeping the injector duty cycle low (low duty cycle = low fuel usage).
For cruising now I've turboed the Panda I'm finding 2800~3400 rpm is optimal, the turbo is giving some boost to giving the engine load of torque, so again the ECU doesn't drop to open loop mode for gentle acceleration or inclines, but it's not positive pressure so the injectors aren't being pushed hard. I've been finding that driving in 3rd rather than 5th at 30mph is giving an almost identical fuel usage but I have power to dart across the road without being T-boned by the guy coming the opposite way when someone starts crossing the road without looking.
With the techniques above I'm getting economy results to similar to book economy for the car, which is producing far more power & torque.
posted by techathy August 16, 2009 at 11:22 AM