Generally speaking, replacing a rattly old oil burner with a petrol V8 earns you sustained applause in the PH office - but Audi's 4.0-litre twin-turbo diesel, itself a V8, was neither rattly nor old. In fact it was groundbreaking and, thanks in part to the installation of a 48V-driven electrically powered compressor, delivered forward momentum like virtually no diesel engine before or since. Aboard the SQ7 and SQ8 it did astonishing things. Bentley briefly put it in the Bentayga, where it should have stuck out like leatherette, but didn't. Porsche even did without the compressor when it sunk the V8 into the Panamera 4S - and it was still exceptional. It easily ranks among the finest oil burners ever made.
Now, having long since departed Porsche and Bentley's lineup, Audi says it will be expunged from the car it started in. The SQ7 (and SQ8, which only received the engine last year) will be sold from now on with the biturbo 4.0-litre V8 TFSI. Of course it will be splendid at its job and delivers a 72hp gain over the diesel motor, yet even with cylinder on demand tech it will not be as parsimonious (relatively speaking) as the TDI, and nor will it deliver the same in-gear tidal wave of shove - the TFSI's admittedly healthy 568lb ft of torque is still 96lb ft shy of its predecessor.
Audi says the V8 exchange is due to the increasing prevalence of petrol engines in the high performance SUV segment - without mentioning that the increasing prevalence is partly due to diesel's fall from grace in the aftermath of the emissions scandal. Far be it from us to dredge up so much spilt milk from under the bridge - but it's hard to forget that the SQ7's launch in the UK coincided with Volkswagen being ordered to pay $2.8 billion fine by a federal judge in the US. Against that backdrop, a 435hp 4.0-litre V8 was always likely to face an uphill struggle for widespread acceptance, no matter its credentials or its suitability for a large SUV.
And just as its introduction probably typified the high watermark of oil-burning achievement, so its withdrawal signals the extent of the retreat. Obviously the diesel engine is not dead (nor close to it: JLR just got through announcing a new straight-six Ingenium motor and Audi's S-badged saloons are currently TDIs) but its brief dalliance in the 'high performance' arena must now be drawing to a close. Even if people were prepared to still buy a cutting edge V8 diesel en masse, soon there will be no manufacturers left developing them. The SQ7 and SQ8's transition to petrol power was inevitable, and aside from more frequent trips to the petrol station, the models' well-heeled buyers will be no worse off. Still, it's a shame to sacrifice such a monumental device in the process. For that, we doff the PH cap.
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