Author Topic: How Tesla saved Honda  (Read 3899 times)

ColinB

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Re: How Tesla saved Honda
« Reply #15 on: July 02, 2022, 07:30:11 AM »
If you use Spritmonitor, each time you enter fuelling it works out your actual CO2 wh8ch is useful.

I doubt that. The only way to get actual CO2 emissions is by a sensor in the exhaust pipe, as they do for an MOT test.

CO2 and mpg are directly related by a simple formula ...
https://www.eta.co.uk/2010/02/22/calculating-a-cars-co2-emissions-from-its-mpg/
... so spritmonitor is probably using that or something similar. The formula also reveals that in order to get the magic 100 g/km mentioned by John a car needs to average around 67 mpg.

Kremmen

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Re: How Tesla saved Honda
« Reply #16 on: July 02, 2022, 08:12:55 AM »
Spritmonitor must be using some calculation as it does vary.

I'm currently showing 107g/km based on 61mpg.

I may top up next week and as I'm currently showing 69mpg my average should rise, so let's see ......
Let's be careful out there !

embee

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Re: How Tesla saved Honda
« Reply #17 on: July 02, 2022, 11:39:34 AM »
Of course the CO2 is directly related to the fuel used, that's where the carbon comes from. The amount of C emitted in any form other than CO2 is absolutely minimal (HC and CO are strictly controlled and are very small compared to CO2).
Due to the way official calculations are done (rounding etc) there can be a small range of proportionality in quoted figures, but essentially CO2 produced is proportional to fuel mass used.

The ratios given in the link by Colin are different for petrol and diesel because the carbon/hydrogen ratio is different for the two fuels, thus the ratio of H2O/CO2/N in the exhaust is different, the amount of CO2 produced per kg fuel used is different. This will also apply to different ethanol (E10/E5 etc) content in petrol since it also carries some oxygen as well as the H and C, but the numbers are still pretty close for most everyday purposes, the effect of E5 or E10 is only a couple of percent or so.

The big issue with diesel engines is the NOx and particulates, and that's a whole different discussion.

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