Quote:
Originally Posted by Galvatron1
Fracked gas & diesel seems the most extremely harmful to the environment. I guess environmental consciousness and eco modding are not mutually exclusive.
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“The best diesel will never match the best petrol engine for NOx, In a modern petrol engine, just enough air is mixed with the fuel to consume both air and fuel completely and the exhaust after-treatment consists of the well-established ‘three-way’ catalytic converter. Diesel engines are ‘lean-burn’ with excess air left in the cylinder after all the fuel is burned and the high temperature burns nitrogen in the air to generate NOx. Three-way catalysts do not work with any lean-burn engines. whether petrol or diesel. Lean-burn petrol engines have been tried in the past, but they produce just as much NOx as a diesel and need the same type of exhaust after-treatment.
Getting rid of NOx
The first step is to reduce the amount of NOx leaving the engine using minute control of high-pressure direct fuel injection, plus exhaust gas recirculation to cool combustion and reduce the amount of oxygen present in the cylinder. Then to meet the latest EU6 emissions, diesels need either a lean NOx trap (LNT) in the exhaust system or more complex and bulky selective catalytic reduction catalyst (SCR). With SCR, urea fluid held in a separate tank is injected into a catalytic converter to neutralise the higher levels of NOx.
Jones says LNTs are less efficient and can only scavenge about 60% of NOx from the exhaust. SCR is much more effective when fully warmed up with a percentage clean-up rate “in the high 90s”, he adds. For small cars using LNTs, a switch to SCR to satisfy RDE may pose a problem because the SCR system is more bulky and expensive. That may force manufacturers of A and B segment cars to stick with downsized petrol engines, but dropping small diesel engines will make it harder to meet their fleet CO2 average."
https://www.autocar.co.uk/car-news/i...-diesel-engine