1slowbusa

iTrader: (8)

Thanks NicD, I will give it a shot. I appreciate the help.

joecar

+1 change stoich, and leave PE where it was; if already corrected VE/MAF will stay the same as said above.

joecar

EQR is regardless of stoich AFR, so just leave it as it was.

joecar

Avoid tricking the system unless you have no other way.

1slowbusa

iTrader: (8)

Hey guys, I took the car to the track yesterday. With changing the Stoich in the tune, it took the 13.7 and the Power Enrichment and at WOT it was commanding 12.01. (13.7/1.142=12.01) I attached a snap of the log. What do you guys think, is this correct because my understanding was that the Wide band read 14.57 stoich so no matter what, the WOT should still be reading 12.81 on the wide band??? What am i missing? Thanks

By the way, I missed 4th gear, thats why there is such a big gap in between 3rd and 4th. Haha

NicD

iTrader: (7)

It's not perfect so don't expect it to be and the commanded a/f is going to be based on the stoich setting in the PCM so ignore it for practical purposes. Also if you had the stoich set at 14.57 before but were running the typical 10% ethanol based gas that most areas have (not sure about PA) then that would throw it off as well since that technically would have been 14.1 stoich. Either way, with the stoich set properly just tune as normal and leave the PE alone and aim for your target on the wideband (12.8). Don't make it harder than it has to be, keep it simple.

joecar

See, there are now 3 stoich values to deal witth: 14.63, 13.7, 14.57.

Your wideband does not know the stoich you set in the calibration, and vice-versa.

Using the original stoich value/scale, your PCM is commanding 14.63/1.142 = 12.81

Using the same scale, your wideband is reporting 14.63/14.57*12.01 = 12.06

1slowbusa

iTrader: (8)

Thanks NicD and joecar,

I was able to do one run on Sunday in lambda and after doing more research, man it is a lot easier just doing everything in lambda. I read a post that basically said forget AFR and only worry about lambda because EQ Ratio and Lambda is inverse of each other. AFR should only be used when setting the stoich in the tune for the fuel being used. See pic attached of the run. The car spun on the launch so I basically put it in 4th so and floored it to get a reading on the wideband.

But, there is still something that confuses me about this. You always read to get PE EQ Ratio, you take the stoich of the fuel you are using divided by the desired AFR at WOT. Example 14.63/12.8=1.142.

But if I change the EQ Ratio with the new fuel 13.7/12.8=1.07. Now i know this is not correct because lambda is inverse of eq ratio and 1/1.142=.875 which is what I want at WOT on a NA tune. But I got the 1.142 by 14.63/12.8 not 13.7/12.8.

So, for example, if I wanted to change my EQ Ratio for PE to 13.0 AFR, would I use the 14.63/13.0=1.125 or would I use the actual fuel I am using 13.7/13=1.05. This is is the only way I have found to find the EQ Ratio for PE in my research.

Another example would be running a dry nitrous kit. If say I wanted to command 11.5 with this fuel, would I use 14.63/11.5=1.272 or would I use the stoich of the new fuel 13.7/11.5=1.191?

Or is there a chart that is used that has set EQ Ratios for given instances, like example of changing to 13.0 or running a dry kit with 11.5 AFR?

But, through all this, I like the idea of using only Lambda for WOT, just got to figure out how to come up with the correct EQ Ratio even if the fuel has been changed. Hope this makes sense.

NicD

iTrader: (7)

Sorry man tried to help you by telling you exactly what to do and what to ignore but here you are still trying to do conversions with lambda, EQ ratios, etc.

1slowbusa

iTrader: (8)

I get exactly what you told me. But, by using the lambda instead of having to do all kinds of conversions, for example stoich set in tune at 14.63 then the wideband reading 14.57 as stoich, then there is an error between them.

With doing it all in Lambda, everything is on the same playing field.

Trust me, the way you explained it makes sense and it can be done that way but it takes more to do it that way. Dont get me wrong, i really appreciate the help and I have learned much. Thats what this forum is for, right.

But, maybe if I cant get an answer, i just do it the way you say and go from there. Im just one of those guys that needs to understand both sides instead of relying on one side and doing it. HAHA

NicD

iTrader: (7)

Set the stoich for the fuel, leave PE alone, adjust fuel to hit 12.8 on the wideband. Nothing is going to be easier since your wideband is already on the gas (14.63) afr scale so that's what you go by, you are overthinking it.

pdxmotorhead

Just a anecdote about fuel.... Is what it is, I played around with a slightly warmed up 350 on a dyno once and tried several street fuels, the power level from various 93 octane pumps was all over the map.

I spent a couple weeks selling Sunoco fuel each year at the local road race track for several years, I got a chance to hang out with their technical chem reps that work with race teams on fuels and such..

Something the chemists said was that when you mix race gas and random pump gas the result is TOTALLY not predictable. They use different additive packages in pump gas based on whatever they get the best deal on for Oxygenation, anti knock, etc. the package changes sometimes weekly.. Race gas has a couple very unique features,

First it has none of the chemicals that help prevent the fuel from evaporating (Mandated by the EPA for street fuel) if you take a small shot of race and street fuel and pour them on the asphalt the race gas evaporates in seconds, some street fuel will lay there for hours.. So the end result is a better spray pattern or atomization level from race gas than pump, which they claimed was responsible for more power changes than most folks realize..

The other is that the additive combinations wont necessarily produce a octane you'd expect, its possible to mix 104 Sunoco with 93 Pump and get 87.. The chemicals can be additive or deductive depending on what the combination the distributor was given to add to the base fuel. (And the distributors do not know whats in the additive package the manufacturers keep that very tight.)

The chemists said tune for what your going to run and don't mix even from the same brand.. And always check the actual data from your system(AFR/EGT etc), to make sure your getting peak power and not getting a bad result.

dw456post

I sure am glad that I read this. I switched to ID850's in my E40 and had to do the double stoich method, and since I am in TX, most of our fuel is 14.1. I thought I had to change the PE to agree with that---which means that I am running lean at WOT. I was told to switch to Lambda because now since the injector change, AFR error would not read correctly in HP tuners. I have been pulling out my hair trying to figure out the changes. I got used to AFR and Lambda is hard for me. Looks to me that I need to be at .78lambda instead of .81 where I am now. (blower)

joecar

Change only the stoich (it should be 28.2 to effectively scale for the injectors), do not alter PE.

AFR error needs to account for the doubled stoich in the calibraion, so you need to multiply it by 2
( e.g. wideband reads 14.57 when calibration commands 28.2 )

When you compare AFR's you're implicitly comparing Lambda's (the stoich AFR's cancel out... if the calibration's stoich and the wideband's stoich are significantly different (as in 2x in this case) then you have to factor this in

( e.g. at stoich calibration commands 28.2 and wideband reads 14.57, so 28.2/14.57 = 1.935 )

dw456post

My stoich is 28.2. I had to change back my PE tables.
Thanks!