dannobre

iTrader: (3)

So why doesn't Lamba ( A/F) from the CanScan and Scanalyser seem to match the outputs from a calibrated WBO2 guage??

sco

Because, apparently some sort of "correction factor" is being applied in the CZ edition of CanScan for who knows what reason. As Hymee has said he has found the stock sensor accurate enough for tuning. That's why sCANalyser outputs the sensor data as supplied by the PCM without modification (except if you select AFR are the units of measure lambda is mulitiplied by a user configurable stoichiometric ratio).

Rasputin

OK, let's agree on the following compromise :
Change in theoretical air requirment between commercial blends of gasoline are so minute that you can effectively use AFR as a parameter to tune your engine.
However, Lambda is a better parameter as it is totally independent of the fuel used. That's why Lambda is usually used by engine development engineers throughout the world.

As for the examples mentionned in a previous posts of yours showing "real" AFR/Lambda data, it's difficult to evaluate their validity as there is no indication of the measurement methods or equipment.

I have here in front of my eyes, a copy of a report I wrote in June 1999 about the 2.0L Zetec engine that powers the Ford Escape / Mazda Tribute for North American markets. That reports provides test results to demonstrate this engine complies with SFTP regulatory requirements affecting WOT power enrichment. Indeed, legally, the WOT fuel tables cannot be richer than LBT (optimal fuelling for power). Any enrichment for hardware protection MUST come from another PCM strategy module, not the WOT fuel table!

And that reports shows that even before any catalyst protection, the AFR scheduled by the PCM is as low as 11.3:1 (0.78 Lambda) at 2500 RPM, WOT and only goes above 12.0:1 AFR (0.82 Lambda) at 1000 RPM, WOT. That's f***ing actual data recorded on a steady state eddy current engine dynamometer using a properly calibrated NGK UEGO sensor and Horiba AFR meter!

If you include the catalyst protection overfuelling, the AFR goes as low as 10.7:1 AFR at 6000 RPM, WOT for an inlet temp of 25°C and 90°C coolant temperature.

So I think it is time to stop saying that it is not normal to measure AFRs under 12.0:1 especially when one considers the very high temperatures of rotary engine's exhaust gases.

Fabrice (ex-Ford UK engine engineer).

sco

Slightly off topic but related to this discussion - What is the story with oxygenated fuel in the US? Ethanol has a lower stoichiometric ratio than typical non-oxygenated gasoline so I expect it would reduce the stoich ratio. According to this http://www.epa.gov/otaq/regs/fuels/oxy-area.pdf it varies from locality to locality.

If you fill your car at a pump in the US do you know if you're putting in oxygenated fuel?

r0tor

iTrader: (1)

What part of "it doesn't matter if you tune with lambda or lambda x 14.63" don't you understand? Do you think it really makes a difference if I tune my car from .8 to .9 lambda on a guage or if I tune my car from reading a guage from .8(14.63) to .9(14.63)? Do you realize that by scaling the lambda by a constant to tune your still using lambda to tune? Hell, I can go into the code of the CANScan and remover the "*14.63" part of the code and read it in lambda - by doing that it makes my tuning "more proper"? Last time I checked, any number can be scaled up or down at will with constant factors but the true variable remains the same. This is not frikkin rocket science here.


For the rest of the argument, since you wish to make a big proclamation about me using a different type of O2 sensor as a pure demostration purposes - how about I say any info on a ZETEC engine has no bearing either especially since a rotary can withstand much higher amouts of ignition advance and a/f ratios before detonation then a traditional piston engine can.

Be my guest and find any dyno of a NA car showing a lambda/afr at or below or even close to .75/14.63. Or would you also now wish to make the argument that dyno numbers are completely wrong and shouldn't be used to tune with either?

Rasputin

I will indeed make you tuning more accurate as YOU HAVE NO WAY TO KNOW THE EXACT STOICH AIR REQUIREMENT (that is your "14.63" figure) of the fuel you're using. Now, as I just said, the difference in air requirment might be small enough to keep using AFR for tuining you engine.


I don't get it. Did I say you wre not using a proper O2 sensor? Unless you use a switching HEGO (see your figure) which is only accurate for one Lambda : stoichiometry! My remark was about the lack of info on the method of measurement and equipment used in the dyno charts I've seen on this forum, that's all.

No, but what I'd love to see is someone fit a Renesis on a proper engine dyno to get consistent performance data recorded in a controlled environment and stabilised temperatures.

And let me tell you that I don't like your tone at all. I find it unfriendly and arrogant. I'm trying to help here. But I will restrain myself doing so in the future dear Rotor.

Fabrice

Nemesis8

iTrader: (3)

Me too. The only shop that has done this so far is Racing Beat. I would love to see their datalogs, but we all know that will never happen. They ran the Renesis engine last year while we were all there for their open house at Sevenstock. If I had only glanced over Jim's shoulder to get a good look at what the gauges were reading on the control panel...

So, what a safe tune using Lambda on the sCANalyser for my CZ? .91 maybe?

r0tor

iTrader: (1)

i hope you did not come about that lambda number from deviding 13.3 (aka the number you found for tuning safe before which was given to you as lambda*14.63 from your previous scanner) by 14.63... that would be illegal

Nemesis8

iTrader: (3)

I set myself up for that one, I'm totally confused now

Actually, I have the CZ pulled at the moment till we are all singing off the same sheet of music.

dannobre

iTrader: (3)

It seems we all like arguing ...about the same thing. There are valid points on both sides of this discussion. I think most of us involved in this discussion understand the basics and beyond. The problem I see is there are a lot of people on this forum that read stuff about tuning CZ's or E-manages and take everything said as gospel...without understanding what is going on. If you use the values from some of the tools...and use that same value with a different tool...that can cause enough of a variable on the edge....to cause knock or ping that can kill an engine

sco

dannobre... I think that is the crux of the discussion on using Lambda. It can't be misinterpreted whereas AFR can be.

Nemesis 8 - I don't understand what the eManage does to the MAF signal to be able to recommend a target lambda, however I have heard of tuners targetting .91. (And just to be clear... the term used was .91 not 13 point something).

Lschiavo

OK OK Dannobre,

Repeat after me.... L A M B D A (el, ei, em, be, de, ei)

Again ..... G A U G E (gi,ei, iu,gi, e)


Hope that helps... :D

sco

Just FYI... I edited an earlier post (https://www.rx8club.com/showpost.php...4&postcount=52) to clarify my comments on differences in readings in sCANalyser vs CanScan. I was re-reading the thread and noticed I didn't say what I was thinking very well.

Lschiavo

Here is mine in 3rd gear, any suggestiions? I am using 94 octanes fuel, how do i know the stocik value of it?? Should i use 14.65 as default?

Lschiavo

How do we know which is the target or good lambda?
In the racecar we use a renesis. Our lambda can not be below 93. Target is 94, 95 is too high. Will that be the same with a turbo on it?

dannobre

iTrader: (3)

looks a bit lean up top........is it pinging at all?

Are you still running 9PSI?? Can you increase the fuel at the top end...or have you maxed out the injectors??

Lschiavo

I am around 75% at the injectors at this point. I am running 7 psi for daily driving. I will increase the fuel in top end. Look at my previous post and tell me what u think... No pinging unless i go past 9 psi

dannobre

iTrader: (3)

.94 would be OK for a NA race engine. It's about where I've been tuning my E-manage unit

It would be too lean for a turbo for sure...probably better around .85 area

Ask some of the turbo guys like MM, Fanman etc what they suggest...or ask some of your Mazda Race connections what they would tune a turbo renesis to. Maybe get us some insider info :D

Lschiavo

we dont use turbo in our racecars

r0tor

iTrader: (1)

maybe the resident lambdahumpers would wish to guess if i'm using afr or lambda to tune with

(results of a weeks worth of data on my 89 octane map... in canscan afr and lcanscan ambda... wow, it can do math )

sco

r0tor... you need to get over it.

If we look at your second table there is no ambiguity about what your real O2 readings are. If we look at the first table, it can't be used for an accurate comparison with other vehicles unless you knew the stoichiometric ratio for the fuel you were using and used that to generate the AFR table and communicated it in conjunction with the AFR information.

(For simplicity of explanation I've chosen to ignore the fact that the CZ CanScan is manipulating the data from the PCM)

r0tor

iTrader: (1)

because my first table is nothing but a software encoded x14.63 equation of lambda there is no ambiguity either... if i paint my baseball bat black its still a baseball bat.

edit-> and to elaborate further i could carless what fuel i am using or anyone else is using if we are all looking at an afr given to us as 14.63 x lambda - which we all will be because i am fairly certain nobody is going to do a chemical analysis on their fuel to adjust the constant, just like OEM's themselves don't when determining the instantaneous mpg readings for displays by taking the magical constant, maf, speedo, and o2 sensor.

zoom44

why .63 why not .65 or 14.7?

sco

That's right... there is no ambiguity what the lambda ratio is once you say you used 14.63 for stoich. My point exactly. If you just posted a table of lambdas you wouldn't need to say that.

You should care about the fuel you're using. Crap fuel will have a lower energy content and lower octane thus more likely to detonate at the same timing advance than better quality fuel. If you're tuning your car to get the most of it you need to consider what fuel you will put in it.

To give you an example we've been working with a professional tuner here that sells a box to change the fuel maps on Ford XR6 turbo cars. That box has three different fuel maps the owner of the car can pick to load into the PCM. The first is the standard factory tune, so if they want a service they can do that without the service department knowing they run a different tune normally. The second tune is for the fuel the owner likes to run (e.g. if they use premium fuel). The third tune is typically a tune for when the owner can't get the fuel they want to run normally. This still gives better than stock performance but doesn't run as much timing advance as the second tune.

I've read elsewhere on the forum that a canadian that did a road trip noticed significantly different fuel consumption in the US compared to Canada. This indicates that the quality of the fuel was less in the US.

If you want the most from your car you should care about the fuel you put in it.

dannobre

iTrader: (3)

Funny thing about that...some fuel additives will raise the octane...BUT will also lower the energy content of the fuel....the most common is ethanol. It seems that the powers that be want us to use this fuel more and more....it's crap!