Fuel cut or boost cut???

[I`m Batman]

I put bacon grease in my car. The exhaust smells yummy.

I can't hear anything (ping/knock) on my bike because it's so loud... v-twins...

[RX-7 Chris]

I use 85 in my car lol.

[rmeeker13]

May i suggest colder plugs! Im about to go to 2step colder plugs but you should at least be running a 1step colder plugs...could eliminate the KR.

[~Barn~]

I agree w/ erod...we don't drive NA sport bikes. And even looking at your logs you ARE getting KR, so therefore should be running higher octane. You also have to look at the tune the motor has. Yes there's less chance of knock w/ higher octane, but that also means you can advance your timing to get more power. Mazda does that in their stock tunes for our car. More knowledgeable people with our cars have stated the highest octane is required for our cars.

Basically you're comparing apples to oranges in this scenario and it does NOT apply. But I can see where they are coming from on ur sport bike forum, but again, does not apply to our cars.

[color=dimgray]Well I have to respectfully disagree. True we are not on sportbikes and we do have forced induction engines, but the principles behind pre-detonation do not change. This isn't an apples-to-oranges scenario, because we're still talking about engines that are intended to have a spark-based ignition. And within that defined system, pre-detonation is pre-detonation is pre-detonation. It's either happening or it isn't. (?)[/color]
[color=dimgray] [/color]
[color=dimgray]So with that fundamental principle already inherent, the next question becomes: Is your vehicle experiencing symptoms of knock/pre-det or not? My vehicle is not experiencing it on any "trend-worthy" basis; and the logs you are looking at, are actually from a map that I am no longer using right now, anyway. Over the few hours of data-logging that I've done since Saturday on my new map, I've had occurrences of KR about ~10 times. And that's from (I'm guessing here) over 30,000 time-stamps.[/color]
[color=dimgray] [/color]
[color=dimgray]Again... I’m just not seeing it as either an observable trend, nor a datalogged trend. There’s not justification for changing fuel.[/color]
[color=dimgray] [/color]
But hey... Your mileage may very. I do not begrudge anyone from personal preference, I just enjoy the science behind it all.

[tbot]

It is different based on the fact of HOW the fuel is delivered and when. Read up on direct injection...it IS different.

[94R2CSprings]

I had the same problem with a stock stage 1 map. Cobb sent me a v103A map that supposedly compensates for this problem but it is only a bit better than the stage 1. If you keep on the gas above 5K you'll still hit boost cut.

[erod550]

I had the problem with a v103 map too. Stage 2 cut all the time and stage 1 didn't cut until it warmed up a little bit but it still did. Only way I got rid of the cuts even with an AP was my protune. Not sure exactly what my tuner did to get rid of them but he did. I haven't had a single cut since I got tuned even with some very warm weather.

[tbot]

could be load cap...if your absolute load stays peaked at a certain number for a bit, flat lines so too say, it is most likely load cap

[Eclipse]

running 85 octane is a sure-fire way to have ANY warranty voided on your car. Mazda is VERY specific on this topic in your warranty guide...check it out

[TheNewBlack]

I would NEVER use 85 in a car I take this good of care of. Makes no sense if right on the gas cap, it says premium fuel only. Do what you want it's your car, but IMO it's a bad move. Sorry for the thread jack.

[~Barn~]

My car was out of warranty when I bought it, so it's less of a concern for me, than it might be for others. That's a valid point though, if Mazda will put the screws to you.

As far as it "making sense", I suppose it does to the same degree that it makes sense taking blood-pressure medicine, if you don't have a blood pressure condition.

Mazda probably "says" to only service your car at their dealerships too.... And only buy genuine Mazda parts... and only clean it with genuine Mazda soap...

But at least we agree on the freedom of "personal choice". I will continue to stand behind the science, and fully support everybody's right to stand behind what they're told.

[erod550]

If you're not getting any knock with 85 octane, it's not because it's ok to run 85 in a car that's supposed to have premium. It's because your timing is retarded to the point that it's actually tuned for 85. If I were to put 85 in right now when my car is tuned for 91, I guarantee I would get KR. So while sure, if your timing is scaled back you can run 85, you're certainly not getting more power out of the car by doing so. You're leaving power on the table by not advancing the timing and running 91. You say you stand behind the science but the science goes against what you're saying.

[~Barn~]

Yeah, but speculation is only worth so much, erod. The fact of the matter is that these cars are manufactured under the provision of sea-level operation. The HP numbers that they tout are established at sea-level. Gas mileage figures are published for sea-level, Torque numbers are advertised at sea-level... I could go on.

On top of that, ECUs are calibrated by the manufacturer, to essentially perform 2 ongoing things: 1.) provide the best MPG and 2.) expel the fewest emissions. They aren't configured for performance, but they will at least re-calculate themselves based on changes in atmosphere. Again though... trying to achive those 2 main goals. Being that we are 5000+ feet higher than sea-level though, you have to understand that we are the exception to all those published items, we are not inclusive of them.

What you've done though, is essentially flipped the conversation, by saying that I'm leaving HP on the table by not manipulating values, such as timing, and then building the engine to have that "need" for more pre-detonation prevention. And while I can't disagree with that (and probably hundreds more "tuning" suggestions), this dialog wasn't really about tuning and HP. It was just a discussion about whether or not a lower-octane fuel can be properly used, despite higher-octane "recommendations". So sure.... I'm probably leaving HP on the table by not adding a NOS bottle too, and adjusting for it, but let's not dilute the topic.

Either way, I think I've said my piece. I'm not trying to make converts out of anybody, just offer up an alternative perspective. All vehicular things being equal, if you want to have the best performance (with cost savings as an added bonus), use the lowest octane you can , without experiencing pre-detonation. If your car is built to have a need for higher octane... Use it.

[I`m Batman]

I actually have to agree with Barn on this one. Most of the place I've been to at sea-level still sell 91 or 92 octane gas as premium. We are 5000+ ft. above sea level, we can use lower octane here. (less O2 = lower AFR, less O2 = less pressure = less chance of pre-detonation = can use lower octane) I probably won't do it but I'm sure it'll be fine up here... just don't take it lower. (sea level)

[LaginWagon]

Yeah, but speculation is only worth so much, erod. The fact of the matter is that these cars are manufactured under the provision of sea-level operation. The HP numbers that they tout are established at sea-level. Gas mileage figures are published for sea-level, Torque numbers are advertised at sea-level... I could go on.

On top of that, ECUs are calibrated by the manufacturer, to essentially perform 2 ongoing things: 1.) provide the best MPG and 2.) expel the fewest emissions. They aren't configured for performance, but they will at least re-calculate themselves based on changes in atmosphere. Again though... trying to achive those 2 main goals. Being that we are 5000+ feet higher than sea-level though, you have to understand that we are the exception to all those published items, we are not inclusive of them.

What you've done though, is essentially flipped the conversation, by saying that I'm leaving HP on the table by not manipulating values, such as timing, and then building the engine to have that "need" for more pre-detonation prevention. And while I can't disagree with that (and probably hundreds more "tuning" suggestions), this dialog wasn't really about tuning and HP. It was just a discussion about whether or not a lower-octane fuel can be properly used, despite higher-octane "recommendations". So sure.... I'm probably leaving HP on the table by not adding a NOS bottle too, and adjusting for it, but let's not dilute the topic.

Either way, I think I've said my piece. I'm not trying to make converts out of anybody, just offer up an alternative perspective. All vehicular things being equal, if you want to have the best performance (with cost savings as an added bonus), use the lowest octane you can , without experiencing pre-detonation. If your car is built to have a need for higher octane... Use it.

Yes, but , not true on reduced HP with higher octane. Also, the logic does not apply to anything turbo charged. Making his statement untrue for FI vehicles.

He could have reworded that to say "reduces detonation" as it's not actually reducing the fuels ability to detonate, it's just reducing the chances of it detonating before it's supposed to. That's why we have 85 octane up here and you don't see 93 many places at all.