Join Date: Apr 2009
Location: The Great White North
Drives: 2017 AWD Sportage SX - Black / Beige
Mentioned: 17 Post(s)
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Stinger 2.0 vs Sportage 2.0
The new Stinger 2.0l Turbo provides an interesting data point for comparison to the Sportage 2.0l Turbo in the context of fuel octane required for the two engines.
KIA specifies 91 octane premium for the Stinger, rated a 255 hp at 6200 rpm vs 240 hp at 6000 rpm for the Sportage which they want you to believe only requires 87 octane regular. Both engines produce the same maximum torque value of 260 lb/ft
So lets examine the respective torque outputs of those two engines at their power peaks.
hp=torque X rpm / 5252. So to solve for torque we can re-arrange that equation to torque=hp / rpm X 5252
so for the Stinger's torque we have 255hp / 6200 X 5252 = 216 lb ft at 6200 rpm to produce that 255 hp
for the Sportage's torque we have 240hp / 6000 X 5252 = 210 lb ft at 6000 rpm to produce that 240 hp.
So the Stinger produces a mere 6 more lb/ft (albeit at 200 higher rpm) than the Sportage. That represents only a 6/210X100= 2.85% increase in output over the Sportage. Less than 3%!
Both engines have 10.0:1 compression and I would wager they are operating under the same amount of boost. The difference is almost certainly a result of slightly more efficient intake and/or exhaust tuning and maybe a little ECU timing to take advantage of it on the Stinger as that could easily pick up 3% in output.
So why do they recommend 91 octane in the Stinger over the 87 for the Sportage? i think there are a couple of reasons, mostly marketing and less so engineering.
The demographic for a Stinger purchaser would be much more inclined to accept the fact that their new sports car requires premium fuel. The demographic for a Sportage purchaser, maybe not so much. So KIA fiddles a little with the ECU tuning on the Sportage to do their best to get by tuning it to run acceptably on 87 octane to satisfy the marketing people. With the Stinger, they are under no such constraint.
Now, considering that, with only a 2.8% increase in torque to produce the Stinger's hp output they decided on 91 octane (because it would be much easier to "get away with it"), that would tend to indicate that the Sportage, producing less than 3% as much power, is likely running much closer "to the edge of detonation" on 87, so to speak, than the Stinger is on 91.
So finally, given the Sportage is closer to that edge, should you come upon regular fuel that maybe isn't quite 87 octane (has been known to happen) it might just be enough to push you into the plug cracking and potentially other problems that Stinger engines simply won't ever see.