I have a older Seat Arosa car, a car classified as super mini, like Nissan Micra, Fiat 500c,etc. They have several engines, but I have the one with the officially “biggest number”, the 1.7 SDI, which, per Auto data . net has about 1716 cc, which sounds like a lot for a car of that size, however, it reaches 0 - 60mph in around 17 seconds, while the 1.4 TDI (60hp one) reaches 0 - 60mph in about 2 seconds less, while a 1.4 16v (75hp) reaches it in just around 8 seconds.
Why is the 1.7 SDI so underpowered in comparison to the smaller TDI engines?
4400 rpm maximum, perhaps? No doubt someone with more knowledge of automotive engines will step in here shortly, but higher power (relative to displacement) engines mean more expensive parts. It looks to me like the engine in your car was designed to cost less to manufacture.
I also feel kinda smug that my Prius, infamous for being one of the slowest cars sold in America, with an anemic 100 hp engine + electric assist (net about 120 bhp), has a 0-60 time of 10.2 seconds. Practically zippy.
The 1.7 is naturally aspirated while the 1.4 I turbocharged.
Btw they seem to be listed as 60hp and 75hp respectively.
Acceleration under load is notoriously bad for NA diesel engines… Explaining why would involve teaching the entire principal of internal combistion engines which I suspect is beyond the scope of the answer you are looking for.
Naturally aspirated diesels as a characteristic have slow acceleration and may be slower to accelerate even with the same rated horsepower. Explaining why would involve teaching the whole principal of operation for internal combustion engines which is probably beyond the scope of answer you’re looking for.
To put it simply,
Turbos force in air, allowing more fuel to be burned in the same volume of cylinder…so more power.
So what’s the 1.7s advantage… reliability.
Bigger, stronger parts making less power and the lack of sensitive , high speed turbos that break down oil quickly contribute to that.
As does eliminating oil distribution lines ,the turbo itself, monitoring systems and a whole host of extra items that are necessary for the turbo to work.
Oops, didn’t realize the first one posted and thought I was editing it
SDI(suction diesel injection) produces low power numbers with the tradeoff of high reliability and good fuel economy. The type of engine is why it has high displacement but low HP. As you’ve seen there are other engine designs that will produce higher power numbers with lower displacement.
That would be because it’s gasoline.
Gasoline burns faster, releasing it’s energy quickly. Allowing for shorter strokes , lighter parts. Also making it’s power curve peak at higher rpms which allows gearing for more acceleration.
Getting effeciency from a diesel often involves different gear ratios . To take advantage of the larger amount of torque at lower rpms they often use taller gear ratios.