arghx7

I think it's conventional wisdom around here that with the current flash Mazda runs the Renesis stupid rich which is costing a bunch of horsepower. But when you compare the wide open throttle AFR's of the Renesis to both low and high performance piston engines they're really not that different. Even a frickin Z06 runs richer than 12:1 AFR's.

Here is a chart of WOT fuel on a completely stock Rx-8. This was taken from a log that somebody on here gave me (more stuff is here https://www.rx8club.com/series-i-engine-tuning-forum-63/anybody-got-csv-log-n-stock-maf-scaling-184844/ ), I forgot who but I am attaching it.



Ok that's definitely richer than what people tune for in modified performance applications, but compared to other stock piston engines it's not that different. Here's the target AFR table on a nonturbo Subaru Outback (175hp?), which is of course not really a performance engine.



The Rx-8 may run a bit richer than that in some spots but not that much richer. Now here's the target wide open throttle AFR table on a 500hp 2007 C6 Z06:



So the Corvette Z06 is actually tuned richer. The Renesis WOT tune is pretty close to industry standard.

Flashwing

Oh really?



This was a 1/4 mile log taken with an MSD dashhawk reading the front O2 sensor and on Mazda's latest flash.

arghx7

looks pretty close to the Z06...

it's all relative man. You can call it rich if you compared it to the AFR people run on n/a engines when they don't care about emissions. But a typical OEM turbo car runs in the low 10's AFR.

paulmasoner

iTrader: (1)

i dont think the issue is that it runs flat out rich, though many may percieve that. the only concern is the cat-protection. in that case, it is rich.

Flashwing

Isn't that what you're using as your comparison is an N/A RX8? I agree that the aspect of "rich" vs. "lean" all changes depending on whether you're running an FI or N/A setup.

I know that you know the difference.

You are making the case that an N/A RENESIS using Mazda's flash does not run rich using a single car as evidence. What is widely known is that there are enough variations in RX8 performance and build quality (engine wise) that like a broken watch you're bound to find one car that fits any given theory.

My point was simply that using a single car to make a broad statement isn't a great idea.

bse50

The 13b-msp does not run rich, it runs pig rich!
This is the right statement.
Taking into consideration turbo cars is 100% useless and it all comes down to the life of the catalyzer. That's why we run 2 point richer than optimal, and i'm sure that WASTING fuel doesn't help with emissions.

nycgps

iTrader: (1)

I dunno why Mazda wanna run as bse50 call it, "PIG RICH" at higher rpm.

not like stock CAT last ANYWAY

HiFlite999

iTrader: (2)

For most people, running rich at WFO isn't going to have a huge effect on overall mpg's. Running rich at mid-range light throttle will, and 22 mpg highway says that's what we have.

arghx7

I've surveyed a large number of OEM calibrations across manufacturers, turbo and non turbo. In this case I used two cars, a Subaru Outback and a C6 Z06. One runs slightly leaner in a few places than the '8, and the other runs equally rich or richer in a few places. Look at almost any OEM calibration on modern port injected n/a cars and they run AFR's from the low 11's to the low 12's. The Rx-8 runs in that range.

2001 Eclipse GS, 2.4 liter 4 cylinder rated at I believe 160hp:



2005 Eclipse GT, 3.0 liter 6 cylinder rated at 200hp:



I apologize that these axis labels are messed up, the definition files for Eclipse's aren't fully fleshed out. Here's a 1990 300zx non turbo, 3 liter V6 rated around 220hp:



The cells in the left side of the map are open loop cells, which is why they have funny numbers in there. Here's the target AFR table for the C5 Z06, which is a bit leaner than the C6:



And here's the stock target AFR table for a 2001 Blazer:



How many more stock maps do you need to see? The Renesis runs richer than some cars, leaner than others (Mitsu does tend to have richer tunes), but it's well within a normal distribution. The "stupid rich" argument, that every other modern car must be tuned to something like 13:1 and Mazda just decided to dump in fuel, is a myth. Mazda has to meet cat life regulations and NOx emissions targets, and so does every other manufacturer.

Emissions is a zero-sum game. You eliminate one type of emission and you cause another. If you run rich under WOT you reduce CO2 emissions and NOx emissions, while increasing HC and CO emissions. If you run leaner you risk cat life while increasing NOx and CO2 emissions.

We'd all like it to last longer, but most of them do meet the Federal standard. That's partly why the government has increased the cat life requirements.

I'll admit I don't know all the closed loop control logic on the Renesis, but most cars have an open loop delay counter that usually keeps the ECU from richening the mixture in the conditions you have described. The problem is the engine geometry of the 13B-MSP (which Mazda is correcting with the 16X) as well as the weight and gearing of the Rx-8.

arghx7

Emissions vs AFR chart:



Between 11:1 and 12:1 you can see that NOx and CO2 are very low, with the HC and CO2 curves crossing right around 12:1. This may make that AFR range a good compromise between pollutants for WOT operation. You can see that the rich mixtures drastically reduce CO2 and NOx emission, while HC and CO are increased. Usually there is a little bit of oxygen in the cat to (stored in the Cesium) to help convert all that extra HC and CO.

robrecht

Who exactly has made this mythical argument? I think most people here are just looking for ways to optimize performance and do so with the full knowledge that leaner AFRs may shorten their cat (if they still have one) and even their engine life. I doubt people would be surprised to learn that other car makers have done the same thing. Mazda just happened to get caught overestimating final hp numbers, reportedly by failing to take into account new US cat life requirements.

MazdaManiac

iTrader: (3)

Your RX-8 samples are not nearly typical.
Most run 11:1 or richer above 5k RPM and WOT.

How many RX-8s in OEM configuration (with no mods whatsoever) have you had to opportunity to sample? For me, I'm up to well over 300.
About 1 in 10 2003 - 2005 RX-8s run leaner than 11:1 above 5k RPM. 2006 - 2008 fare slightly better.

Whether another OEM chooses to run that rich is also a spurious argument.

dannobre

iTrader: (3)

And the point of this is

That there is no more power? Or we shouldn't feel sorry for ourselves that Mazda tunes that rich??

Or........??????

Jedi54

iTrader: (7)

mine ran pig rich on the OEM map. (I'm sure I have the log around here somewhere)
Mine pegs 11.1 above 5k and pretty much used to stay there.

Flashwing

I honestly feel like this is a shell game.

First off, simply comparing fuel mapping isn't going to give you the whole story. With the wide tolerances in injector sizing, compression and other factors you're going to see some variation in fueling and performance. This is why I laugh at the notion of "reverse engineering" RX8 tunes because it simply cannot be done. There are far too many variables and inconsistency with RX8's to make any judgement. I can't speak to other platforms because I have no experience tuning anything other than my specific car.

You're missing my point. You used a single RX8 to make your case that the Renesis does not run "stupid rich". I produced data from my own car showing at WOT that it pegged the O2 sensor. Who knows the real value but it was obviously below 11:1. Unless you're FI I'd consider that pretty rich.

So, again, if you search long enough you can find a single example of an RX8 that actually makes stock advertised power or an RX8 with a motor that lasted 150,000 miles on 5w-20. The overwhelming majority of N/A RX8's on Mazda's tune run in the low 11's to below 11:1 at WOT.

Like I said, even a broken watch is right twice a day.

BigTurbo74

arghx7- where are you finding these stock injection maps if you don't mind me asking.

MazdaManiac

iTrader: (3)

Sorta.
Though the stoichiometric ratio is the usual target for cruise, you will actually get slightly better mileage a bit rich of that point (around 13.8:1 for gasoline).

paulmasoner

iTrader: (1)

I may be WAY off base here, but I think we are missing part of the argument. Isn't there a loop(modifier) in place in the PCM for the temp readings pulled from the rear O2 sensor? (ie cat gets hot = dump fuel)

For some reason I was thinking that is the case, and IF so... It may not be the base tables that would show you how rich the Renny can get anyway, but rather the modifier tables/factors.

MazdaManiac

iTrader: (3)

No. ITs just the default values in the main fuel tables and how "off" they are based on the MAF readings.

paulmasoner

iTrader: (1)

ok cool, glad i havent been blabbering that to everyone i know

learycd

iTrader: (1)

the black and brown discoloration on my white paint around my exhaust tip suggests that the mazda maps are VERY RICH

its really bad when im running the stock tune, i should get pictures

paulmasoner

iTrader: (1)

Care to make me believe that when I am looking at my OE tables in ATR and seeing a Lambda entries of .63? EDIT: (w/o opening the laptop back up, IIRC this occurs at peak load somewhere near 6000rpms in the 4-6gear fuel map)
Disclaimer, Of course there are the modifier tables(IAT/baro/coolant/etc) and also the high likely hood that not all sensors(particularly the MAF) are scaled to exactness. Still the potential is easily there, and though the cells showing .63 are very few, there is a decent sized area of that fuel map that is below 10AFR(in Lambda of course)

paulmasoner

iTrader: (1)

I have screenshots of my OE tables i am going to post tonight.... i have the direct shot of ATR, and an excel table converted to AFR so more people can follow....

interesting notes:

almost 13% of this table is <11.99, but >10.99 (most of it under 11.6)
almost 17% of this table is <10.99
for a total of ~30% of this table with AFR from 9.2 - 11.6
AFR as low as 9.2 in places
there is even a 15 cell grid entirely in the 9's


i'll also throw up a shot of my 1-3 tables... the lowest point there is .71 (10.4AFR) go figure

zoom44

re-read what jeff and a few other posts said and figure i was going to write all of that here PLUS

you mentioned the CURRENT tune. Remember that the 2004s and even early 2005s came with RICHER TUNES!!! the current stock tune is still too rich for best power and MPG in most cases but as you point out with the emissions graph tere is a reason for that. the nox.

but that original tune? simply stupid pig rich unconscionably rich. the only thing it did was perhaps get over a cat regulation. nothing else. they knew it of course and have been leaning it out in various places ever since.

its still too rich for best NA power as part of emissions strategies. truth is though if they didnt have to run the cat by law they could pass a sniffer test without it and a still leaner tune.

paulmasoner

iTrader: (1)

4-6 gear air/fuel tables in ATR in lambda


here is that same table in AFR blocked up to highlight certain area


1-3 gear air/fuel tables, these arent as bad but still not great




you may say that the rich parts are cornered in areas generally not called upon. but i spend a considerable % of my cruising time north of 6,000 rpm, and other highway time in the 6-8,000 rpm range in 4/5/6th gears


that's not rich?