This is the 3A92 dyno, I live in the torque band, best way to drive in my opinion haha
This is the 3A92 dyno, I live in the torque band, best way to drive in my opinion haha
2018 mirage ES manual
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View my fuel log 2018 Mirage Es 1.2 manual: 41.6 mpg (US) ... 17.7 km/L ... 5.7 L/100 km ... 50.0 mpg (Imp)
bloodehunter (07-24-2018)
^^ Whatever ^^
I'm dredging this back up as I'm considering making a purchase. And I would like to use the vehicle I have that is equipped with a 3A92 for relocation purposes of said procurement. It's comfortable, fuel efficient, and capable enough.
I'd like to better understand the initiation of MIVEC variable valve timing. Because I would like to cruise at a speed in 5th gear that is just under the threshold of MIVEC actuation. I'm assuming activation is in the vicinity of 3,500 rpm.
But reading this thread, it seems to imply that the rpm initiation of MIVEC variable valve timing, varies. However, I'm not certain I believe that, mainly because I don't full understand the MIVEC operation, but will go back and watch the video. AND ... in my case, I'm talking about droning for hours on the interstate. So I think there would be a somewhat fixed rpm (say 3,500 rpm for argument's sake) that initiation of MIVEC variable valve timing would take place. In that case, I'd like to cruise at 3,450 rpm to maximize my fuel economy.
And if I need vast huge mountains of torque, I will slip it back into 4th gear and hit about 4,500 rpm.
What say the crowd? Does anyone KNOW at what rpm initiation of MIVEC variable valve timing would begin in close to steady state interstate droning?
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View my fuel log 2020 Mirage ES 1.2 manual: 42.4 mpg (US) ... 18.0 km/L ... 5.5 L/100 km ... 51.0 mpg (Imp)
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View my fuel log 2015 Mirage ES 1.2 automatic: 40.5 mpg (US) ... 17.2 km/L ... 5.8 L/100 km ... 48.6 mpg (Imp)
I would say that sounds right. I was just pulling through 4th gear and by 3,600 rpm or so it was pulling much harder than it was as 3,400 rpm. And, I think I could just start feeling a little something at 3,500 rpm.
So I think my best droning tow speed would be 68 mph & ~3,450 rpm. I feel safer towing slower than 70 mph anyway. And if I need MONSTER power, I'll just put it into 4th (putting the engine in the meat of its max hp/tq) and let that BIG dawg growl.
From what I could understand reading about MIVEC, it was saying / implying that current MIVEC vehicles had variable valve timing (that did not have a set rpm with the variation started), and lift. It seemed to say that the lift was activated NOT variably. Meaning that the lift would always initiate from some rpm. But did not give that set rpm. It must be 3,500 rpm or thereabouts.
Last edited by 7milesout; 07-06-2023 at 05:43 PM.
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View my fuel log 2020 Mirage ES 1.2 manual: 42.4 mpg (US) ... 18.0 km/L ... 5.5 L/100 km ... 51.0 mpg (Imp)
That dyno graph looks exactly like how it feels to drive, thanks for posting that. When I've let people borrow the car I tell them to shift no lower than 4000, and keep it over 3000 unless you have no intention of accelerating or going up a hill anytime soon. Sometimes when I have a passenger, I'll hold it against the rev limiter for a few seconds and just look at them grinning. Sometimes the reactions are funny.
Mitsu master tech since 2009, German car guy, recently bought a 14 Mirage 5spd with 145k. Youtube Channel
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View my fuel log 2014 Mirage ES 1.2 manual: 30.5 mpg (US) ... 13.0 km/L ... 7.7 L/100 km ... 36.6 mpg (Imp)
the CVT version appears to be much more fuel efficient and loves lower revs.
I rarely bring mine over 4000RPM. But I do like the sport mode which is great for a little engine braking or for a boost in RPM's when you need it.
Looking at the schematics, and watching the video, it is the Control shaft (intake rocker shaft), that controls the variation in valve timing / lift. From what I can understand, the variation, varies both the timing and the lift together. They appear to be mechanically tied together. However, it still feels when driving, like there's a threshold for the "variation" to either activate, or vary effectively. Meaning, there might be some variation before 3,500 rpm (or might not), but if there is, that variation doesn't seem to be having a significant impact on power until the 3,500 rpm range.
That said, I believe the ECU controls the "Control shaft (intake rocker shaft)." Which makes me wonder ... could that signal be defeated / manipulated? Into keeping the lift low? If my understanding of how the timing and lift are tied together mechanically, I realize the variation in valve timing would also be defeated.
The end effect would be less power above 3,500 rpm ... but may also be greater economy (in steady state high speed cruising). Since we tend to feel and believe that the timing and lift start having an effect at 3,500 rpm and greater, it might increase mpg from that 3,500 rpm and higher zone. 3,500 rpm (on 4.055 final drive geared Mirages) is ~69 mph / 111 kph.
I also wonder, if the MIVEC system was defeated and just left the lift low, is the ECU hard programmed to fuel for the expected airflow in the rpm zone that the lift is (normally) increased? Would the ECU keep slamming fuel at it even though the amount of air supplied is less than programmed for, due "tricking" it into low lift? Or would the ECU adjust fueling based on the air available? Something tells me if the Control shaft (intake rocker shaft) signal were defeated and always left in low lift, no timing change zone, the ECU would over-fuel in the expected higher lift rpm zone, the AFR would go rich, and there would be a check engine light with associated P-code error. I don't know, just speculating. And if that were the case, there would be no fuel savings.
For you savvy wiring diagram readers, can someone detect the circuit and wire color for the circuit that signals the Control shaft (intake rocker shaft) positioning?
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View my fuel log 2020 Mirage ES 1.2 manual: 42.4 mpg (US) ... 18.0 km/L ... 5.5 L/100 km ... 51.0 mpg (Imp)
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View my fuel log 2014 Mirage SE wussie cvt edition. 1.2 automatic: 37.7 mpg (US) ... 16.0 km/L ... 6.2 L/100 km ... 45.3 mpg (Imp)