V6 fuel mileage

[Nd4SpdSe]

If you're using a lower octane fuel than the motor requires and the ECU has to retard the timing to compensate, than you'll lose mileage.

[MrMazda92]

The K8 and KLDE are both 9.2:1. The only one that's 9.5 is the last run of KLZE.

Motors can definitely "tolerate" lower octane, that's what knock sensors and computer-controlling timing systems are for, but doesn't mean it'll give it's best performance.

That's a reminder I shouldn't have needed

Still, my mistake changes it from 5% to a whopping 8% increase in static CR over DE/K8.
I really need to start taking more time to word my posts differently, I'm aware of how the ECU responds to knocking.

Either the 10:1 ZE should function properly, without knocking(or retarding timing) on lower octane fuel, or the lower CR engines(like the 9.5:1 G4, 9.2:1 DE/K8) should require a higher octane fuel from the factory.

If the only variable changing the CR from 9.2(or 9:5):1 CR is the piston, as is the accepted theory behind the ZE's higher CR from the factory, then it should be fairly simple to discern whether or not that 8% increase in CR really warrants that large of a bump.

Anybody want to take the time and effort to run regular fuel(AKI 87 Here, AKI 85 in Canada) and check their ignition timing? If nobody feels like doing it, I'll be the test dummy after I get my ZE running again.

[Nd4SpdSe]

Remember too that ZE's have better air intake systems and a KL31 cammed ZE's cams are more aggressive. It's hard to compare apples to apples.

That's an interesting idea, but you would need the test subject to be someone with a stockish (no megasquirt, bolt-ons only realistly) KLZE that gets 30+mpg to give you the info that you're looking for. For the last few years, the average ZE MPG seems to be mid to high 20's, which I would say aren't the right candidates. Too bad us here (locally) all moved on, cause there was several of us here that easilly fit the bill.

[MrMazda92]

Remember too that ZE's have better air intake systems and a KL31 cammed ZE's cams are more aggressive. It's hard to compare apples to apples.

That's an interesting idea, but you would need the test subject to be someone with a stockish (no megasquirt, bolt-ons only realistly) KLZE that gets 30+mpg to give you the info that you're looking for. For the last few years, the average ZE MPG seems to be mid to high 20's, which I would say aren't the right candidates. Too bad us here (locally) all moved on, cause there was several of us here that easilly fit the bill.

It's true that the intake and heads allow more airflow, it still doesn't change the assumption that throwing 10:1 ZE pistons into any other KL will require a bump to premium fuel, as has been stated repeatedly over the years. If anything, the increased airflow should help to cool the combustion temps slightly, over the DE style intake ports and runners. I agree that it likely does require higher octane fuel to reduce the likelihood of knocking(and therefor retarded timing), the part I have a hard time with is the idea that it should take a change of 50 points(AKI rating) to facilitate that relatively small bump in static CR. (8% bump)

Honestly, it's not a huge deal, but I really do want to figure this out once and for all.

I've got as stock a ZE as you can really get, KL31 Cammed milli with stock exhaust netting about that mileage. I haven't done extensive economy testing with it yet, since It's torn halfway down due to oil leaks and another issue currently. Payday is tomorrow though, so that will be sorted out finally.

I'm not trying to be a jerk to anyone, and I'm hopeful that my posts haven't come across as such. I just really want to get this resolved, so we all know for real, whether or not we actually benefit from premium fuel. Granted, it seems that we get higher octane fuel where I live than most of you elsewhere... 87 octane for regular, where Ryan and others have only 85 available? That's 40% of the bump to Premium as far as AKI goes.

[_-Night-Shade-_]

I'm running 87 octane/regular gas fine and have been for as long as I've had my ZE which is almost 2 years. It's never knocked on me, even when I race. I've tried higher octane and no difference. This is with the hotter plugs too. Our ECUs are too basic to know what kind of octane is being ran so there's not gonna be any timing differences until it senses a knock - how did this rumor start? You can't get better economy out of a 2.5 than a 1.8 unless you make some drastic changes such as changing gear ratios. The slightly higher efficiency doesn't make up for the much bigger change in displacement and injector size.

[Nd4SpdSe]

I'm not trying to be a jerk to anyone, and I'm hopeful that my posts haven't come across as such. I just really want to get this resolved, so we all know for real, whether or not we actually benefit from premium fuel. Granted, it seems that we get higher octane fuel where I live than most of you elsewhere... 87 octane for regular, where Ryan and others have only 85 available? That's 40% of the bump to Premium as far as AKI goes.

You never came across as a jerk. This (so far) has only been a critical discussion.

Octane available also depends on altitude. Those with 85 at the pumps live at significantly higher elevations.

how did this rumor start?

These "rumors" are things that have been around long before my time here, pretty much steming back to when KL swaps first started. Back in the day when this community was inundated with great minds, mechanics and car enthousiasts who all had viable knowledge and experience. Me being here is really the only thing that echos what was and how it was in the past, before most that are currently on here even owned an Mx-3. Weither you choose to believe me or not, or even if it's even relevant or not any longer. There are several of us local ex-Mx3'ers that can confirm the great fuel economy we had, but maybe it's not a coincidence that we all hung around and work together on our cars, sharring knowledge and setups, regardless that some actually went through many motors, lol.

If you want past information on fuel economy, start searching back to MPG threads as far back as 2000, but probably find some good data/threads starting in 2003-2004.

[_-Night-Shade-_]

These "rumors" are things that have been around long before my time here, pretty much steming back to when KL swaps first started. Back in the day when this community was inundated with great minds, mechanics and car enthousiasts who all had viable knowledge and experience. Me being here is really the only thing that echos what was and how it was in the past, before most that are currently on here even owned an Mx-3. Weither you choose to believe me or not, or even if it's even relevant or not any longer. There are several of us local ex-Mx3'ers that can confirm the great fuel economy we had, but maybe it's not a coincidence that we all hung around and work together on our cars, sharring knowledge and setups, regardless that some actually went through many motors, lol.

If you want past information on fuel economy, start searching back to MPG threads as far back as 2000, but probably find some good data/threads starting in 2003-2004.

I was referring to the 'timing changing based on fuel octane' theory, not the fuel economy. Nowhere in the manual does it hint that the ECU changes the timing map based on the octane number.

[Ryan]

Put 87 in my ZE today.

It didn't explode.

Smelled and sounded different though. And strangely, getting 50km before it moves off the F as opposed to the regular 20. Thats a good sign so far, but not a concrete way to judge the whole tank

[MrMazda92]

I drove my '93(ZE) back from Cali with only 2 fillups along the way... The first I filled it with regular(I believe 86?) before realizing it(I hate pumping my own gas, I left the cap at the station too... fail?) I didn't notice a lack of performance, and I had some heavy cargo in the car

[MrMazda92]

You never came across as a jerk. This (so far) has only been a critical discussion.

Octane available also depends on altitude. Those with 85 at the pumps live at significantly higher elevations.

Alright, I'm glad to hear that!

That's actually a good point, I live at a fairly low elevation... Thanks for pointing that out, I hadn't considered it before.

I forget if you'd mentioned it previously, what did you run in your ZE?

[Nd4SpdSe]

Here the lowest is 87, than 89 for mid and 91 is typical for high octane, with Pioneer with 93 octane and Sonoco with 94.

With my Mx-3, I pretty much religiously ran Sonoco 94, but never put in anything less than 91. I also drove that car like a banshee, hit redline a few times a day easy. I tried 87 once every few years, but the tank disgustingly disappeared so quick that I never bothered so never did any long term testing on mileage and performance running less than 91.

[MrMazda92]

Hmm, this is a good thread.

We have 92 octane around here, I've yet to see anywhere that pumps higher... If I do, I'll be thrilled. That will be one step closer to 12:1+ CR.

[Ryan]

C/R is only one part of the detonation story

My ZE is getting good milage on the 87, not blowing up, not pinging, and running okay. Seems a little weaker though, but she is moody on a good day.

[MrMazda92]

I know that, it's just a big chunk of the story, as you put it

Payday comes on the 1st, this last one went into attorney fees and gas for witnesses.

I'll finally get to take care of my oil and gearoil leaks in the ZE.

[_-Night-Shade-_]

I just filled up, drove 432.1km since the last fill up and it took exactly 38.575L to fill up. That's 8.927L/100km = 26.348mpg. Mixed highway and city. Would have been a 500+km tank if I kept going.

Mods related to fuel economy:
KL-ZE + a lot of bolt ons running on KL55 Probinator ECU + KL02 VAF
Stock ignition system with BKR5E-11 V-Power plugs (the hotter ones, not 6)
New front wheel bearings, but my alignment is off.
225/45/16 g-Force KDW
Basic weight reduction
87 Octane (contains 10% ethanol)

If I switched to stock tires it would probably be about 30mpg.