SDI - As Pointless as a Butter Grater

Yes bloody please.

Ooh, hello there! I'm back briefly. My summer holiday wasn't meant to be this short, so after this post I shall return back to my hibernation at the wrong time of the year. So why am I posting now, you may ask? Well, quite simply, an idea popped into my head; I wasn't going to be spiteful enough to not write about it just because I am meant to be taking a break.

The name for the diesel engines from the Volkswagen group is a very recognisable one: TDI. Those three letters together have pretty much become the pinnacle for diesel itself now, and for a good reason. TDI engines were (and still are) some of the finest oil burners you could have in a car for their time. But did you know the TDI once had a brother? Welcome, ladies and gents, to the SDI engine.

TDI stands for 'Turbo Diesel Injection', whereas SDI stands for 'Suction Diesel Injection'. This gives a pretty obvious clue of how the SDI differs from the TDI: the SDI does not have any kind of forced injection (ie, a turbocharger).

Naturally, this means that SDIs produce a noticeably lower amount of power than their turbo'd brothers. For example, the 2.0L SDI in the VW Golf MK5 (the last VW SDI engine to be fitted in their cars to my knowledge) produced at best 74bhp, but the 2.0L TDI could achieve 161bhp. It shows how heavily diesels rely on a turbo; a naturally aspirated 2.0L petrol engine these days can achieve well into 200bhp.

The SDI in all its miserable glory

So you may be thinking that the trade-off for less power would be improved economy. Surprisingly though, you'd be wrong. The 2.0L SDI and TDI achieve the exact same economy figures: around 50mpg from the top of my head. Which begs the serious question: why the hell would someone have the non-turbo?

SDI may live in Golfs and Polos, but the TDI is living the high life

One of the arguments may have been that the SDI was cheaper to buy than the TDI, which was probably very true. But let me put it to you this way: TDI engines are always a good one to two grand more expensive spec-to-spec than the petrol equivalent. Assuming that the SDI was about the same price as the petrol motors, it would still not be good value. Why? Well, 74bhp and 50mpg is not an impressive number for petrol engines, let alone a diesel one. I bet the petrol engines (that produced more power) were just as frugal as the SDI. So I'm still left wondering: why did people buy the SDI?

Can your SDI do this? Huh?

I'm honestly stumped by it. The only other thing is that perhaps people didn't want the power of a TDI, but I can't help thinking that A) 74bhp is way too little for a mid-sized hatchback, and B) The SDI is vastly inferior against the similarly priced petrol engines, as I just explained above.