bxb40

Seing plots from other people tuning their cars using the Canzoomer units, I pulled my AFR using CANScan. I did it under driving conditions, in semiauto mode, in both 2nd and 3rd gear (I have an 4AT).
What do you experts think of my AFRs?

Thanks in advance.

Razz1

Yep sounds like normal to me. I heard it was 14.5 and your a littler higher.

Of course it is rich. Mazda made it that way. Try to bring down to 14 and then feel the difference in performance.

Vaillant

Wait a minute...I think you've got it backwards!

It's an Air:Fuel Ratio (AFR)...the higher it is, the more air you have and therefore the leaner you are! 14.6:1 is stoichiometric, so you definitely don't want it any higher than that! Then you'll be lean and you'll be risking knock and pre-combustion. I believe that at Wide Open Throttle (WOT) something around 13.5:1 is a good number to aim for.

~ Matt

bxb40

So half the time, when I am above 14.6 (which is the mean of the data), I am under detonation conditions? Not good.... But it should mean I have max power, right? How is the cat affected if it is too lean?
I guess I should go see a dealer, but what to tell them? The car runs except a small wirling noise when pressing the accelerator - which does sound like mini-detonation (I had the real one when using 87CO gas... sounded like little rocks in a can... now, this one is present even with 93CO and it is much more faint... could be a rattle from some other part - including a failed cat )

Vaillant

Well, I'd see what other AT users are seeing...maybe ask around in the Canzoomer forum or something. Were these readings done at WOT or what? I haven't used the CanScan tool, so I'm not familiar with it. If you were just cruising on the freeway, then you are doing fine.

If you see a dealer and you have the CZ installed, they could potentially void the engine part of your warranty. If you just pulled the AFR readings (and don't have a CZ installed), then you might want to tell the dealer you are having knock issues. I have a 6 speed and even running 87 octane, I don't have any knock. Your car shouldn't either, I would think.

~ Matt

ddub

Are rx8 engines that different than the rx7 engines? 14.7 is stoichiometric btw.

I know on an N/A 2nd gen rx7 you are running lean at 13.5:1 and higher, lots of people that tune their 2nd gens are seen as risky running 13.3 to 13.5 AFR's and a safe margin is 12.5 to 13.0

But maybe the rx8 is different and less prone to detonation because they don't have peripheral exhaust? I'm not sure, I don't know enough about the rx8 setup. Especially when the rx8 has 10:1 compression it seems like you'd want to run similar AFR's as 2nd gen n/a guys run, but then again maybe the rx8 is just different.

Charles R. Hill

iTrader: (7)

Many of those who are actively tuning their 8's, whether via Canzoomer or E-Manage, are reporting A/F ratios between 13.5-13.8:1 as appearing to provide the best balance of power and reliability while N/A. Every gas-burning engine runs best at 14.7:1 but the metallurgy of the engine doesn't typically allow that. Thus, we richen up the mixture a bit to cool things off. Jeff Abrams has commented on his experiences tuning his turbo set up and he has discovered just how lean the Renesis can go before trouble becomes apparent. Because of this tolerance I would suggest that when tuning the Renesis one uses only the best monitoring devices they have available to them or let a pro do it.

CRH

dannobre

iTrader: (3)

I am surprised at the tolerance to pinging in this engine. I have tuned mine to 13.5 ish and it will run 87 octane with no apparent pinging. Even with a lot of advance dialed in. I can't hear any...and I haven't logged any ignition retard. I have been running 89...seems to give good performance for the buck. For those with the CanScan...watch that you are using the correct A/F version. the regular 3.50 and 3.60 versions will be lean.....in some cases real lean....

Also any value at 12.05 on the corrected version has maxed out the value...it is richer than that........it just doesn't read any lower than that! (not relevant anyway)

ddub

Interesting.

For best tuning, though, you really can't go by AFR alone. Like if you're playing with timing you really would want to moniter everything (EGT, AFR, water temp, oil temp) for best tuning because if you advance too much some temperatures might change that you otherwise wouldn't be aware of.

I know when I did my rebuild on my 7 on the first startup and idle the timing was extremely advanced (no big deal for idling in the driveway but I couldn't change it until its initial idle/break-in was done) and there were flames bellowing out of my exhaust just at a 2k rpm idle! That's how much of a difference advanced timing can really make, it was actually kinda cool to see the blue flames just puffing out of the exhaust.

Does anyone know what kind of EGTs people tune for in the rx8 with advanced timing? Or what oil temps are in the "safe range"? This is all very interesting as I might be picking up an rx8 soon.

dannobre

iTrader: (3)

I haven't measured oil temp..would need to add a sensor. My coolant temp is fine driving...it will spike when you stop...but nothing objectionable. i think this iwas more of a problem with the FD esp...it was marginal at best with its cooling. We have much better radiator, and oil coolers on the 8

RX8-TX

Even if those numbers are under "normal driving" conditions, I would take another look at it. Next time trying to go WOT -trying to get a high load on the engine. Otherwise, the ECU is always in closed loop, adjusting the mix trying to land it near 14.7

Do you have the data in raw format with AF, Engine speed & time?
Take a look here: 6 Speed Air Fuel @ the Closed Loop chart.

Reason I am asking, I am curious to see how the AF adjusts depending on what you are actually doing. The scatter graph is good to get an idea of where you are most of the time under similar conditions but, if you were to mix a WOT run in there, it would throw all your data off. And that's were you really want to take a look at it from a performance perspective.

Oh....and yes, a lean mix, is supposed to fry your cat a little sooner. But if you haven't have a CEL, you should be alright (at least its not there yet.)

Edit: Oh yes...did you happen to take a snapshot at the rest of the sensors before & after the run? (like this: Pre & Post run conditions)

ddub

Just remember that advanced timing will increase EGT and oil temp and may not show any difference in AFR. AFR is by far not the only thing you tune for when playing with timing, EGT is most important and oil temp is just nice to monitor. Oh and I'm not even referring to the FD as I wouldn't know about that, I have an FC. And as for water temp, that's just a good thing to minitor too as you go up in power.

You definitely don't have to monitor these things, but the more you advance timing the more you really need to know your EGTs. AFR should be made slightly richer as you keep advancing the timing and there's always the possibility of wanting to run higher octane fuel but that's more for extreme advancements like 30-35º total advance.

What kind of advance are you running?

I know with everything I've done to my 7 I monitor AFR via wideband, oil temp, oil pressure, and water temp. I haven't gotten my EGT installed yet but I'm only running about 10º advance so I haven't done anything too extreme yet.

dannobre

iTrader: (3)

The car stock will run approx 28 deg advance at WOT.....I have added up to 6 deg in some spots. I have run more before...but it is really intolerant of any advance at low and partial throttle...so I dropped a lot of it. The car is very interactive with the timing maps though...depending on load and temp and probably a lot of other variables...it adjusts the timing a lot. It idles at -5deg with trailing plugs first and I've logged off throttle at up to 42.5 deg of advance....that drops to approx 10 degrees when you stomp it.

ddub

Yah the rx7 advances timing with throttle too, obviously just like any car almost. When I said 30-35º total advance, I meant advanced past what is stock. So say at 4500 rpms your stock advance is at 20º, then the 30-35º advance would put you at 50-55º advance instead of 20º. At that point is when you really need to be careful with your tuning.

6º advance or less is no big deal so yah you don't have to worry about an EGT yet. Like I said I'm running 10º advance past stock which puts me at 5º ATDC at idle (or positive 5º) and it works linearly with the revs. That's about as much as I'll push without proper monitoring equipment and standalone.

What kind of split are you running with your timing? Did you change it at all or did you leave the split stock?

Charles R. Hill

iTrader: (7)

All of what you are saying is exactly what Jeff was talking about. I, too, am wondering about optimum EGT's.

CRH

dannobre

iTrader: (3)

I've logged mine as high as 1800 deg...don't know how accurate that is though...it is a calculation based on the O2 sensor circuits I think. I suppose a pyrometer probe in the exaust would be in order to do it right. My take on it is that it will pretty much only hurt the Cat .....so I'm not worried...It's been replaced with a Random Tech unit that's supposed to take the heat

ddub

Here's a little article on peripheral exhaust 13B's:

"EGT gauges will read slightly differently for different cars EVEN WITH THE SAME
MODEL AND BRAND OF EGT GAUGE.

If you want to make absolute sure what YOUR safe temps should be, get the car
on a dyno with a wide-band. This will verify what is safe and what is not.

The EGT gauge is one of the most misunderstood tuning tools, as interpreting
it's output is not very straight-forward. Wide-bands have always been popular,
because you shoot for a target number, and reaction time is quicker (versus EGT).

EGT probe placement is also paramount in how the EGT gauge reacts and what kinda
temps it displays. Funky exhaust gas resonances can mess up readings off the
EGT gauge! I've tuned a big turbo FC running a divided turbine set-up that has a
GReddy EGT installed with the probe in the downpipe; EGT's have always read low.
Leaning cruise fuel mixtures to the verge of lean surging will only show 700C; I
could do this to my car, and my exact same EGT model would easily show 800C+!
That's a different of over 100C! This is why you should "calibrate" the EGT
gauge readings on a dyno.

Now, once you know what your safe EGT number is, we need to explain the relationship
between lean and rich. The engine has a narrow window to which the EGT is pretty
stable. We are primarily concerned with WOT (i.e. best power) EGT numbers, so
we'll concentrate on that. At "best power", the EGT number should be pretty
stable. Going leaner than best power will raise EGT - the dyno should also
show the engine LOSING POWER. This is due to inaudible detonation. If we go
leaner, EGT will start to skyrocket and detonation is pretty evident. From best
power, if with richen it up, the EGT will actually go DOWN for slightly richer
conditions. You still get almost complete combustion, but the extra fuel cools
everything down. If we richen it up substantially, it'll come to a point where
all the extra fuel will start to ignite out the exhaust port, and this will cause
the EGT to rise (this looks exactly like lean!) and sound like detonation, because
the excess fuel is igniting in the exhaust system; this is when too rich will also
raise EGT.

Now, on top of everything, there is a delay in the response of the EGT. REMEMBER
THAT! O2 sensors (narrow and wide) will react pretty quickly, but the EGT reacts
significantly slower...and you need to keep that in mind, especially when tuning
fuel controllers and stand-alones.

With that in mind, these are the SAFE numbers I target until I can verify (with a
dyno) that you can go hotter...

EGT probe in downpipe, 700°C
EGT probe in turbo exhaust manifold, 740°C"


Now I'm not sure how much temperature changes with the change in exhaust port location on the renesis, but the article is still a good read.

Oh and this is for turbo, NA's can go hotter safer, obviously.

bxb40

I am runing the CANScan v3.50. Could it be off due to some misread oxygen sensor signal? Where can I get another version for my unit for Palm VII? On their site, this is the latest.
The AFR is estimated, not a direct measure....
The data were aquired during normal driving, not a lot of WOT....
And yes, my car will ping on 87 at WOT at high RPMs - on 89 gas seems fine though.

dannobre

iTrader: (3)

If your CanScan says that your A/F is anything but 14.6ish in closed loop areas....(low TP and RPM's) then it is out....when I run 3.50 software the A/F is reading 13.8ish in these areas...out by .8...that's a lot. It seems that a few people have tuned with this and had way too lean A/F levels. I don't know if the correction tables work on the Palm version or not....e-mail Dan Harrison and ask him if he has a corrected version for the Palm

RX8-TX

Except for off-throttle up/downshifts....



And FWIW, I've always used the Lambda values, not the A/F with the CANScan.

RX8-TX

Could you post the original data file?

bxb40

OK, I transformed the Palm file into .txt so it can be imported as comma delimited in other plotting software (i.e., Excel). I guess this is the file you wanted to see....

RX8-TX

Well....I don't know much about AT's but the only difference I find between your runs and mines are that every time I lay off the gas for an up/downshft, the CANScan sees an extremely lean condition for a fraction of a second -which should be perfectly normal since you are cutting fuel supply for a second. In your case, you don't have such, since you are never off the gas....

If anything, your motor is running a little bit on the lean side compared to the plots I've seen, but I don't think it is anything to be concerned about.

You should really do a short WOT run, that'll be more representative of what the ECU is doing when you engine is more prone to detonate / ping.

Thanks for the file though!

The attachment is the way I take a look at runs. Its an excel file, just change the extension from TXT to XLS.

r0tor

iTrader: (1)

i'm running 6 degrees of advance over stock and my EGTs (at least what the OBD is picking up) say the temp went from 1670 to about 1696... or not really anything significant

rotarygod

I'm just curious why people always want to advance timing over stock which is 30 degrees at full throttle when retarding it from stock may actually make more power? If you want to play with timing advance, advance it between 4000-7000 rpm. Part throttle is totally different though as under certain loads it may get up over 40 degrees advanced.