Mazda CX‌-30 Forum banner

1 - 14 of 14 Posts

·
Registered
AWD 2020 GT CX-30 ceramic coated
Joined
·
698 Posts
Discussion Starter · #1 ·
So considering the Mazda MX-5 recommends using 91 octane fuel or better.. and has the exact same compression ratio.. what makes it different then running our non turbo 2.5 skyactiv engines on say 89 or 91 octane fuel... same compression ratio 13-1 as the mx-5 but just a smaller engine and close to the same HP .. would there be any noticeable benefit? or just waste of money... I am trying to figure out what is different in the MX-5 weather its different tuned ECM software that always runs the engine at full capability on 91 ... The cx-30 is the same compression ratio so what gives with the different fuel recommendations... Would there be any difference with the cx-30 on more octane or is the ECM tuned differently and would be a waste of $$ on anything more then 87? I have yet to try it out in my cx-30 but wanted to see if anyone had a technical answer.
 

·
Registered
Joined
·
220 Posts
An engine optimized to operate on 87 octane will not make any additional power with 91 or even 93 octane. The octane rating of a fuel isn't a measure of the fuels power potential, it is the ability of the fuel to resist detonation/preignition.
 

·
Registered
2020 Mazda CX30 SP (Sport Plus)
Joined
·
280 Posts
Interesting the differences with Mazda in different countries. In Thailand all Mazdas are flex fuel capable. We can run E85 or any grade of petrol. I think the ECU's are programed different here. I run 95 octane (93 in the US) and do see a difference in performance.
 

·
Registered
AWD 2020 GT CX-30 ceramic coated
Joined
·
698 Posts
Discussion Starter · #4 ·
An engine optimized to operate on 87 octane will not make any additional power with 91 or even 93 octane. The octane rating of a fuel isn't a measure of the fuels power potential, it is the ability of the fuel to resist detonation/preignition.
See but what makes the MX 5 different that they recommend running 91 .. it's essentially the same skyactiv g designed engine from what I know .. exact same compression ratio but is the PCM tuned different.. ?
 

·
Registered
2020 Mazda CX30 SP (Sport Plus)
Joined
·
280 Posts
See but what makes the MX 5 different that they recommend running 91 .. it's essentially the same skyactiv g designed engine from what I know .. exact same compression ratio but is the PCM tuned different.. ?
I would think the PCM is tuned different.
 

·
Registered
AWD 2020 GT CX-30 ceramic coated
Joined
·
698 Posts
Discussion Starter · #6 ·
I would think the PCM is tuned different.
I was thinking that but didn't have a deffiant answer.. I know one thing tho my next CX 30 in two years will be a turbo and yah of course I will run premium in it haha .. what's the point of holding it back 😝
 

·
Registered
2020 Mazda CX30 Soul Red Select AWD
Joined
·
133 Posts
They have completely maxed out the HP on the current 2.0 with the 7500 RPM redline and running 93 octane. It all has to do with the ECU tune. For example when the 2016 MX5 launched (ND-1) it had the same power out put as the 2.0 in the Mazda 3. However it required premium fuel unlike the Mazda 3 running on 87 octane. The reason was the tune for the MX5 was for sharper throttle response and quicker revs etc. Something to do with the timing I would assume...

Besides the fuel the 2.0 Skyactive G engine in the MX5 is drastically different than our 2.5L. It is designed and built on the same principles but has no interchangeable parts etc.

I run 91 Non ethanol... Mainly for the ethanol factor.
 

·
Registered
AWD 2020 GT CX-30 ceramic coated
Joined
·
698 Posts
Discussion Starter · #8 ·
They have completely maxed out the HP on the current 2.0 with the 7500 RPM redline and running 93 octane. It all has to do with the ECU tune. For example when the 2016 MX5 launched (ND-1) it had the same power out put as the 2.0 in the Mazda 3. However it required premium fuel unlike the Mazda 3 running on 87 octane. The reason was the tune for the MX5 was for sharper throttle response and quicker revs etc. Something to do with the timing I would assume...

Besides the fuel the 2.0 Skyactive G engine in the MX5 is drastically different than our 2.5L. It is designed and built on the same principles but has no interchangeable parts etc.

I run 91 Non ethanol... Mainly for the ethanol factor.
Wow 😁 thank you for the technical answer much appreciated! That makes sense with the ecu tune and higher rev red line and different pcm tuned software.
 

·
Registered
Joined
·
220 Posts
Which has nothing to do with the CX-30 vs CX5. The 30 & the 5 both in naturally aspirated form, are 2.5l 186 & 187hp & 186 torque. One is not maxed out over the other for a 1 hp difference, if it exists.
It was mentioned that the CX5 "recommends" 91 octane vs. 87 in the 30. It could be the 5 is more susceptible to detonation under load being a heavier vehicle thus recommending higher octane fuel.

Edit: I was mistaken that this thread was comparing the CX5 & CX-30. Apparently I looked past the 'M'

So, never-mind me...
 

·
Registered
AWD 2020 GT CX-30 ceramic coated
Joined
·
698 Posts
Discussion Starter · #10 ·
Which has nothing to do with the CX-30 vs CX5. The 30 & the 5 both in naturally aspirated form, are 2.5l 186 & 187hp & 186 torque. One is not maxed out over the other for a 1 hp difference, if it exists.
It was mentioned that the CX5 "recommends" 91 octane vs. 87 in the 30. It could be the 5 is more susceptible to detonation under load being a heavier vehicle thus recommending higher octane fuel.
I understand the turbo needing 91 for its max HP to which the CX 30 turbo il ne getting in two years il be putting premium in it.
 

·
Registered
2020 Mazda CX30 Soul Red Select AWD
Joined
·
133 Posts
Which has nothing to do with the CX-30 vs CX5. The 30 & the 5 both in naturally aspirated form, are 2.5l 186 & 187hp & 186 torque. One is not maxed out over the other for a 1 hp difference, if it exists.
It was mentioned that the CX5 "recommends" 91 octane vs. 87 in the 30. It could be the 5 is more susceptible to detonation under load being a heavier vehicle thus recommending higher octane fuel.

Edit: I was mistaken that this thread was comparing the CX5 & CX-30. Apparently I looked past the 'M'

So, never-mind me...

I still find this very interesting ... I would like to know more. Have personally sold probably 100 cx-5's and have never heard about premium in the naturally aspirated 2.5L. Where did you find this information?
 

·
Registered
2021 CX-30 2.5L AWD Pearl White
Joined
·
45 Posts
I still find this very interesting ... I would like to know more. Have personally sold probably 100 cx-5's and have never heard about premium in the naturally aspirated 2.5L. Where did you find this information?
It's a lot to study, and it's also a moving target as there are many variables in play. One of the things that the engineers do is run an octane test at every start-up. During the test at specific operating conditions they advance the timing to induce a response from the knock sensors. This does two things, one it makes sure that the sensors work, and two it allows the software to modify the spark advance curve to achieve optimum power and fuel economy. That's why there can be some difference with the higher octane fuel, provided the base software was written to allow for it. On a car that 87 is the recommended fuel, the software may have limits written into it where no benefit from a higher octane fuel is realized.
 

·
Registered
2020 CX-30 GT Polymetal Gray
Joined
·
27 Posts
It would be interesting if this could be put to the test, and see if reprogramming to increase the spark advance limit then testing on a dyno with higher octane fuel would result in more power.

The downside is that max torque would probably be at a higher RPM. For example the turbo produces 320 lb ft at 2500 RPM on 91 octane and 300 at 2000 RPM on 87.
 
1 - 14 of 14 Posts
Top