So I guess we've all been made aware that on regular 87 octane gas, this car produces less horsepower, but the same torque value as when 93 octane gas is run, which is supposed to increase horsepower to 250. This raises a couple of questions in my mind. How can the torque value be identical? If I switch back and forth between 87 and 93, do I get a HP rating somewhere in the middle? If the torque values are the same, what is the advantage of running the higher octane? Does anyone run strictly one or the other because of experience or just preference? What could be the long-term detrimental effects of running 87 octane only? Just trying to make sense of this.
Dual Horsepower/dual octane ratings?
- Thread starter Paco CX-9
- Start date
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- 2018 Mazda CX-9 GT
My opinion is most people would not notice the difference in HP. i run my 2018 GT on 87 (bought it Feb 2018). it's just cheaper & the regular HP is just fine & does it's job
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- Mazda CX-9 Signature
We only have 87/89/91 in SoCal so I can't speak for the 93 with max HP probably peak at 5k rpm or so. But as far as using 91, I didn't notice anything. Mileage was the same, and high speed probably got a stronger pull but honestly I hardly go pass 4k RPM so higher octane is useless to me. CX-9 is all about the low end torque for real world everyday mix city/hwy driving. That said, I only use top-tier 87 octane.
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- 2018 Mazda CX-9 Grand Touring / Deep Crystal Blue / Sand leather
It would be interesting to see a dyno test of the CX-9 on regular vs. premium fuel to see how the torque/horsepower curves look. While the difference between 227 and 250 horsepower may not be much on paper, the difference in area under the curve would be more telling. The difference in the shape of the torque curves would be interesting to see in particular (at least to me).
That said, many "butt dyno" reports say that there isn't much of a difference, which is ultimately what should matter most to the individual driver whose butt is doing the dyno measurement.
That said, many "butt dyno" reports say that there isn't much of a difference, which is ultimately what should matter most to the individual driver whose butt is doing the dyno measurement.
mazdadude
ZOOOOOOOOOM ZOOOOOOOOOM
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- '16.5 Mazda CX-5 Touring
Also, do not forget that "trying out" a tank of high octane fuel when you normally use regular will not result in the motor receiving the high octane fuel, but rather a blending of octanes. Because of the large reserve capacity in the fuel tank, it honestly will take several tanks of the high octane fuel before you reach the optimum octane.
However, what if we tried something like an octane booster additive, and ran the tank down to the empty and poured in some octane boost, while at the same time we refueled with high octane fuel?
However, what if we tried something like an octane booster additive, and ran the tank down to the empty and poured in some octane boost, while at the same time we refueled with high octane fuel?
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There is no detriment to using 87 octane (US & Canada measure of the numerical average of the gasoline's research octane number and motor octane number, two related but different characteristics).
People use the term torque without understanding what it is. Torque is simply a twisting force. It is the twisting force measured with the engine connected to a dynamometer like one of these: https://www.magtrol.com/product-category/motor-test-equipment/dynamometers/
Horsepower is a measure of work performed. The HP is the mathematically calculated product of the torque measure x rpm x a constant. In our English system of measure using pounds-feet of torque the constant is 5252. A different constant is used in the metric system when newton-meters of torque are used. And, 1 hp = 746 watts. Because there are different HP definitions around the world, some engine makers express their engine power in watts. Some very large diesel engines are available up to 82,440 kw (82,4400 746 = 110,500 hp. The torque is never specified.)
So...the effective power of an engine (expressed in horsepower) is the hp actually developed at the rpms we're running at the moment. That is the power we feel and the power we need to do our daily drive. The peak horsepower is the hp developed at very high rpms many of us never run at. The peak torque is what's shown on the dynamometer read out. The torque peak is always at lower rpms than the hp peak. If the torque curve at high rpms drops off less when burning high octane gas, then the power developed will be greater at those same rpms than with low octane gas causing more drop in the underlying torque curve.
What does it all mean?...drive the way you like. If you want more high rpm, full throttle scoot, spend more money and get high octane gasoline.
People use the term torque without understanding what it is. Torque is simply a twisting force. It is the twisting force measured with the engine connected to a dynamometer like one of these: https://www.magtrol.com/product-category/motor-test-equipment/dynamometers/
Horsepower is a measure of work performed. The HP is the mathematically calculated product of the torque measure x rpm x a constant. In our English system of measure using pounds-feet of torque the constant is 5252. A different constant is used in the metric system when newton-meters of torque are used. And, 1 hp = 746 watts. Because there are different HP definitions around the world, some engine makers express their engine power in watts. Some very large diesel engines are available up to 82,440 kw (82,4400 746 = 110,500 hp. The torque is never specified.)
So...the effective power of an engine (expressed in horsepower) is the hp actually developed at the rpms we're running at the moment. That is the power we feel and the power we need to do our daily drive. The peak horsepower is the hp developed at very high rpms many of us never run at. The peak torque is what's shown on the dynamometer read out. The torque peak is always at lower rpms than the hp peak. If the torque curve at high rpms drops off less when burning high octane gas, then the power developed will be greater at those same rpms than with low octane gas causing more drop in the underlying torque curve.
What does it all mean?...drive the way you like. If you want more high rpm, full throttle scoot, spend more money and get high octane gasoline.
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as strange as it sounds, yes, the torque figure stays the same and the hp increases to 250. if your every day driving is in the city you will never notice the difference between the regular and 93 octane diff, but iit does make the difference in the upper band of the rpms. i use premium since my cx9 was new a year ago this because in my country regular gasoline sucks .
Its just a peak value that happens at a certain RPM point. That is how the max torque value can be identical between two tunes with differing peak horse power. It is possible per the math.. On the 93 tune the engine would make more torque at the RPM where peak horsepower is occurring, but it does NOT make more horsepower at the RPM where peak torque is occurring versus the 87 tune.
I've only ever used 87 because its hurts enough filling up with that. Its more than enough power.
I've only ever used 87 because its hurts enough filling up with that. Its more than enough power.
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- 2019 CX-5 Sig
Does the CX-9 tune/ecu treat any octane below 93 as 87, or does it increase horsepower incrementally? Where I live I can get gas at 87, 89, 91, and 93. So can the ecu detect 89 and increase hp to, say, 234? And at 91 increase to 242? Or is it all or nothing, 93 = 250 and anything below = 227?
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- Mazda CX-9 Signature
Don't get caught in this hp number game. Just fill up with what you prefer and drive.
Ssteigss10
Member
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- 2019 CX-9 GT Machine Grey
1st two tanks ran 87. Felt/ heard a slight pulsing, like air/ fuel isnt being fed into engine in a linear fashion under hard acceleration. Switched to 93 last 3 fill ups and its smooth with no pulsing.
Others will say no such issue with 87 but that was my experience.
Others will say no such issue with 87 but that was my experience.
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- 2019 CX-5 Sig
Well, I wouldn't bother with 89 or 91 if the CX-9 won't "use" the higher (but below 93) octane, but I was just wondering whether that's the case: Will the 2.5T engine develop more hp on 89 or 91 than 87?
peak hp @ RPM:
250 @ 5000
peak tq @ RPM:
310 @ 2000
The maps don't start to differ until after peak tq, so octane should not make any difference in acceleration until you go WOT at high rpm. Even on those occasions, imo a few less hp is fine. Like the spec sheet says, that enjoyable phat tq wave down around 2k should be the exactly same no matter what you fill up with.
250 @ 5000
peak tq @ RPM:
310 @ 2000
The maps don't start to differ until after peak tq, so octane should not make any difference in acceleration until you go WOT at high rpm. Even on those occasions, imo a few less hp is fine. Like the spec sheet says, that enjoyable phat tq wave down around 2k should be the exactly same no matter what you fill up with.
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- 2019 CX-5 Sig
I*m aware of those numbers; what I*m asking is whether the octane must be at least 93 for the motor to develop more hp or if grades between 87 and 93 will produce some additional hp. Just wondering, not trying to debate whether it is worth it.
89 & 91 octanes will indeed add horsepower somewhere in the middle of the 227 and 250 range.
To experience peak horsepower in most of today's cars require almost what can be considered "reckless driving" depending on the situation. In almost any case, you're going to be way above highway speed limits. Most people never see it and yet people shop for and prioritize HP.
The intent of my last post was to add some rpm data for the OP question. I have no idea if its progressive. I also don't know where between 2k and 5k rpm the ecm maps start diverging. Would be interesting to see it all.
I have never personally noticed any juddery power or weirdness on 87..
I have never personally noticed any juddery power or weirdness on 87..
Whats the mazda marketing engineer's name that has the youtube vid appearances? If you're serious about getting your answer, track him down. He seems pretty accessible, its a better bet he would know than anybody here. Dave Coleman, that is the guy.
The only place I NEED to go wide open is high mph freeway passing, and I do admit in that situation you can use every one of those horzpowers. Its not a reckless driving situation, and you can be at wot max hp for a while.
The only place I NEED to go wide open is high mph freeway passing, and I do admit in that situation you can use every one of those horzpowers. Its not a reckless driving situation, and you can be at wot max hp for a while.
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- Canada
I believe that it does make a very slight difference. When I got my car in Jan, I filled it up with only 91 (best I can get around here). 11,500 kms later, I switched to 87 to test something completely unrelated to peak HP. I'm now at 14,8XX kms on 87, and the only time I notice the difference is when I'm in Sport mode and I punch it to overtake someone. With 87, there's slightly less "punch". So far the only other difference I've noticed is that I get maybe 50kms more per tank with 91 compared to 87.
Don't quote me on this, but I think that the ECU determines the peak HP based on fuel combustion and engine knock. When combustion occurs and knock is detected, the ECU retards the ignition timing to compensate, which reduces peak HP. Higher octane fuel has less premature combustion, so there is less engine knock and the timing is advanced.
Spark Control
In modern conventional engines, the initiation of a spark at the tip of a spark plug is
controlled electronically by an ECM. A variety of sensors are used to determine when
to initiate the spark, including those that monitor engine load (manifold air pressure),
speed, coolant temperature, and atmospheric pressure. In addition, most new cars come
equipped with knock sensors that detect knock and signal their ECMs. To eliminate
knock, an ECM retards engine spark timing, that is, it fires each spark plug later in the
compression stroke. This reduces peak cylinder pressure and, as a result, reduces the
tendency for autoignition. The downside of timing retardation is a decrease in power.
When knock is sensed in a turbocharged engine, the ECM also decreases the amount of
boost to further reduce peak cylinder pressure. Boost reduction significantly decreases
power. Loss of power stemming from an ECM*s knock-elimination strategies can be
prevented by using a gasoline with a higher AKI or RON. Some knock sensor systems
have the capability to advance spark timing (as long as no knock occurs) to account for
gasoline with a higher AKI or RON and to provide some additional power.
https://www.chevron.com/-/media/chevron/operations/documents/motor-gas-tech-review.pdf
Page 72
The Chevron Motor Gasolines Technical Review is an amazing resource of everything that goes on inside an engine. What Chevron describes is not Mazda specific, and we don't know exactly what Mazda does that is similar or different from the description above.
ECM = engine control module
AKI = anti knock index (colloquially called octane rating)
RON = research octane number, one way of measuring the anti knock performance of gasoline. U.S. & Canadian gasoline is rated by the numerical average of the RON and the MON...motor octane rating, another way to measure antiknock performance. The label we see on the gas pump is 87 AKI, this average. Or 91 or whatever. Other nations use just RON and display a higher number for equivalent gasoline.
Th
In modern conventional engines, the initiation of a spark at the tip of a spark plug is
controlled electronically by an ECM. A variety of sensors are used to determine when
to initiate the spark, including those that monitor engine load (manifold air pressure),
speed, coolant temperature, and atmospheric pressure. In addition, most new cars come
equipped with knock sensors that detect knock and signal their ECMs. To eliminate
knock, an ECM retards engine spark timing, that is, it fires each spark plug later in the
compression stroke. This reduces peak cylinder pressure and, as a result, reduces the
tendency for autoignition. The downside of timing retardation is a decrease in power.
When knock is sensed in a turbocharged engine, the ECM also decreases the amount of
boost to further reduce peak cylinder pressure. Boost reduction significantly decreases
power. Loss of power stemming from an ECM*s knock-elimination strategies can be
prevented by using a gasoline with a higher AKI or RON. Some knock sensor systems
have the capability to advance spark timing (as long as no knock occurs) to account for
gasoline with a higher AKI or RON and to provide some additional power.
https://www.chevron.com/-/media/chevron/operations/documents/motor-gas-tech-review.pdf
Page 72
The Chevron Motor Gasolines Technical Review is an amazing resource of everything that goes on inside an engine. What Chevron describes is not Mazda specific, and we don't know exactly what Mazda does that is similar or different from the description above.
ECM = engine control module
AKI = anti knock index (colloquially called octane rating)
RON = research octane number, one way of measuring the anti knock performance of gasoline. U.S. & Canadian gasoline is rated by the numerical average of the RON and the MON...motor octane rating, another way to measure antiknock performance. The label we see on the gas pump is 87 AKI, this average. Or 91 or whatever. Other nations use just RON and display a higher number for equivalent gasoline.
Th
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