spectre6000

It's already zombified, so I'll contribute.

Wow! Someone else using LOP tuning! I do this with all my carbureted piston engines, and have always loved it. As high an AFR/Lambda as I can get it to run without sputtering down low in the RPM band, then whatever it wants for max power when the pedal is in it. I've been able to get as high as 17.3:1 AFR on some engines. The result is the above mentioned fuel economy, but the engines also run very cool, and throttle response is much more crisp. I had a '74 FJ40 Land Cruiser emissions tested once (it was exempt, but I wanted to know), and it came back with something like 14 or 17 ppm HC compared to ~250 for the brand new Nissan being tested in the next bay. Note, the FJ40 had zero emissions anything, and the Nissan had all the catalytic converters, etc. Other metrics were similarly excellent. In a sniffer-only test, my emissions equipement-free Land Cruiser would have blown the test out of the water as a modern car, and it ran much better to boot.

In a rotary, I see this having even an additional benefit. Rotaries run much higher RPM than piston engines, and for those with RPM-based metrics on their emissions tests, it would be trivial to have an empty cat shell (so that there's a "cat" for the visual inspection), and still sniff clean as a whistle. Then, when you're on the track and in the throttle, the map richens back up to the power making AFR range. You could even spit flames if you wanted. I'm normally fully against emissions defeats, but I think this would be completely ethical. You're essentially using the "track only" section of the map on the track only, and everywhere else you're even cleaner than stock.

I'd love to see some meaningful numbers to know how high an AFR the Renesis can handle while still turning, and get some output figures to go with that. Power decreases at higher AFRs, but not enough to cause problems (or be noticeable) in daily driving. I've never done this with a rotary, and don't currently have one to do it with, but depending on what I end up finding if/when I ever find one worth buying, this will be high on my to-do list.

Brettus

iTrader: (2)

Doesn't work like you think on a rotary. You just lose power so the net effect is : it's leaner, but needs more throttle/airflow to achieve the same speed at that rpms . Gas consumption ends up more than if you ran it at stoich.

spectre6000

That's what everyone who's never done it says about every engine. At least those who aren't trying to claim that at any AFR above X.X:1 it'll overheat and melt down and explode and turn into a black hole and raise Cthulhu from the watery depths and end all life as we know it and bring about the immediate and instantaneous heat death of the universe. If your sole and solitary goal is maximum power, then yes, you make less power with LOP mixtures relative to whatever makes max power. No disagreement there and no one is suggesting otherwise. You don't always need every pony that's possible to be made though. Especially not cruising down the highway and other mundane daily driving situations. You can map (or jet) it to run richer and make more power at higher RPM/load conditions (and should unless you're only going for mpg or something, but this isn't the car for that). Typically, you'd try to skip right over anything right around stoich (peak, or the P in LOP) to keep the heat down, but it sounds like the cooling system on the RX8 can take it from what I see above. Still not recommended, but not quite as dangerous as on, say, an air cooled engine.

Brettus

iTrader: (2)

I have tried it.

spectre6000

Really? How? What happened? Any data to share?

Power drops LOP, and is completely expected. It's not something you do if all you're after is power. Are you saying it doesn't run cooler? Throttle response doesn't crisp up? MPG doesn't increase? etc. etc. All you said is that power drops, and if you try to drive it like you're looking for power you get all the normally expected results.

DocWalt

There's a thread about it on here somewhere. I read the entire thread cause I've always done that sort of tuning on my piston engine cars and I was curious if it was worth my time. RX-8 engine operates ideally between 0.92-0.95 lambda depending on conditions and tuning it leaner does as Brett says and consumption goes up. Even stoich isn't ideal, except for emissions purposes. MazdaManiac tested it extensively again after he made those posts and confirmed it as well.

edit: here's the thread https://www.rx8club.com/series-i-eng...timing-216087/

Brettus

iTrader: (2)

I was trying to improve fuel consumption under cruise conditions only. If you have ever done anything like this you will know how difficult it is to run an experiment like this and get all the conditions identical because even the slightest thing like ambient temp, headwinds, rain or traffic can render your results useless. So it was quite an effort to get results I was comfortable with.
I leaned it off to around 16:1 (I think i tried several afrs actually) and logged the car on the same stretch of road under identical conditions at a few different rpms, then overlayed my logs to get a picture of what was going on. It was many years ago so I'm a little sketchy but this is what happened basically:
With AFR leaner than stock setting (16:1 approx.) :
Throttle opening increased
Mass air flow increased
fuel consumption INCREASED slightly (due to higher airflow)
Engine temp : no issues
Exhaust temp : increased

I remember I even played around with timing but couldn't do anything that improved the outcome.

wcs

iTrader: (2)

@Witi here is a link to a great thread that I believe will help you out with your tuning questions or least give you some more insight.
It's long but its worth the journey. The first post has links to video tutorials. Kane is not using MazdaEdit but the principles are the same for tuning the RX8
So you want to be a tuner look no further

And here is Brettus journey on using ME. It's an epic long thread but there are some good nuggets in there ...
MazdaEdit

Witi

Thanks a lot
I will dig in (got some spare time ^^) and hopfully will learn a lot