fuel consumption
Discussion
Reason I asked was the rating of the Morgan sports at 140 mg CO2 compared with the Lotus (Yota engine) at 200.
CO2 is closely related to fuel consumption and 140 implies something like 45mpg. Moggie weights between S1 and S2, has the aerodynamics of a brick privvy. Elise has reasonable aerodynamics so why the difference in fuel consumption?
Bear in mind these are official CO2 figures. The difference between 140 and 200 isnt fiddled.
Incidentally my 111R averages somewhere in the low 30s too.
CO2 is closely related to fuel consumption and 140 implies something like 45mpg. Moggie weights between S1 and S2, has the aerodynamics of a brick privvy. Elise has reasonable aerodynamics so why the difference in fuel consumption?
Bear in mind these are official CO2 figures. The difference between 140 and 200 isnt fiddled.
Incidentally my 111R averages somewhere in the low 30s too.
Official CO2 figures bear little relation to real-world emissions, otherwise they'd be a simple function of the fuel consumption and the efficiency of the engine, across the entire rev range. The government procedure, like most government procedures, is far from relevant to the real world.
Gearing and ECU maps are the name of the game, AFAIK - many cars have huge holes in the torque delivery across the rev range since the calibration engineers know which engine speed the 'official' CO2 test will be done at, and optimise the engine for low CO2 at that speed, rather than drivability, power or even economy.
Fiddling with the ECU can drop the same engine down a CO2 band, making tax cheaper - at the expense of making the engine perform below its optimum - and that's what the nasp 'chip' jobs correct...
Note that this is just my analysis from the information I've read - I'm not a professional engineer, I'm sure there'll be one along to correct me soon
Gearing and ECU maps are the name of the game, AFAIK - many cars have huge holes in the torque delivery across the rev range since the calibration engineers know which engine speed the 'official' CO2 test will be done at, and optimise the engine for low CO2 at that speed, rather than drivability, power or even economy.
Fiddling with the ECU can drop the same engine down a CO2 band, making tax cheaper - at the expense of making the engine perform below its optimum - and that's what the nasp 'chip' jobs correct...
Note that this is just my analysis from the information I've read - I'm not a professional engineer, I'm sure there'll be one along to correct me soon
bordseye said:
I'm sure you're right Cyberface, but I dont believe that fiddling with the ECU would get the Yota down to 140 or anything even near. So I'm still puzzled about the difference. And why the fuel consumption of a 900kg car is so high
I remember asking a similar question a while back-why does a 8/900kg car with a 1.8l engine have such poor C02 emmisions compared to say a K series 1.8VVC(or even a bloody Avensis).I think it was Scuffers who commented on the latest more stringent Euro IV(or was it V?)emmisions tests which produce a more accurate,consistent test.
Im sure a lot will be to do with the Lotus mapping(just take a look at an Avensis with a 1ZZ,its a 1600kg car and puts out about 177g/km).
So the choice would be crap map with low emmisions or good map with reasonable ones.Its a sports car after all so the latter obviously prevails.
Or am i talking out of my arse again?
Bandit - the Avensis figures tie in with the Lotus ones - 37 mpg and 177 mg CO2 and I've found the reason they are the same despite the weight difference. The CO2 testing is done on a dynamometer at fixed engine speed corresponding to a fixed cycle of use. The max speed for example is 75mph. So the test take no account of weight or aerodynamics or max speed of the car.
All down to the fuel efficiency of the engine and presumably the gearing.
All down to the fuel efficiency of the engine and presumably the gearing.
Edited by bordseye on Sunday 29th March 22:06
Edited by bordseye on Sunday 29th March 22:10
I don't think that's quite true. They do a one-time measurement of the car's aerodynamic efficiency and rolling resistance (coasting from a set speed to another set speed I think) as well as measuring the weight and then somehow incorporate those figures into the final fuel consumption figures don't they?
bordseye said:
I'm sure you're right Cyberface, but I dont believe that fiddling with the ECU would get the Yota down to 140 or anything even near. So I'm still puzzled about the difference. And why the fuel consumption of a 900kg car is so high
Fuel comsumption has a lot to do with driving style and journey type.I suspect many elises are used for short journeys and often with spirited driving style or if driven gentle are because of heavy traffic, again on an often short journey.
Gearing will play a factor too. And I suspect related to the abocve that on an open section of road more Elise owners will drive nearer 80mph than 50mph if given the chance.
I've not got an Elise, but I had a K-Series engined MGF, weighing in at about 1000kg, so not so different. My average mpg was 28, but I drove it like a nutter for mostly short journeys or in traffic. Touring to Wales it managed 43mpg and that was without having to drive like Miss Daisy.
Gassing Station | Elise/Exige/Europa/340R | Top of Page | What's New | My Stuff