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Old Thu, Apr-26-2018, 01:52:49 AM   #1
rjskalet
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Default Running Lean at 2000rpm partial throttle (tables inside)

I need some help understand what is going on with the tables, I am running an AlphaN (MAFless) for a supercharged setup. I want to make sense of what is going on in these tables. I understand how the partial and wot tables work but do they get used since MAF sensor is deleted? Is it possible to convert these tables to see a target afr? I included pictures of the tables below and any help would be appreciated, conversions and calculations is primarily what I am looking for. I see how the lambas convert to a general afr but I really dont get the AlphaN map. For me to add fuel at the 2000rpm markup at minimal throttle do I need to only change it in the AlphaN table or do I change it in the partial load table?

a little information for helping interpret the tables. This car is running e85 and the global fuel multiplier is at .84

Alpha N Table.jpg

WOT Fuel Table.jpg

Partial Fuel Table.jpg

-RJ
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Old Thu, Apr-26-2018, 07:25:39 AM   #2
Bert ///M3
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Default Re: Running Lean at 2000rpm partial throttle (tables inside)

As far as I remember.

The alpha N base table is throttle opening x RPM and the cell values are relative filling.

Part load is relative filling x RPM with fuel in the cells.

So best way tuning wise IMHO would be leave the fuel table alone and alter RF in the Alpha N table, ie set slightly higher figures (you’re running lean so there is more air going in then the engine expects.)

However, the thing I wonder about, is that your O2 sensors should automatically add fuel and adjust fueltrims to suit, unless this is disabled my removing MAF?
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Old Thu, Apr-26-2018, 12:12:13 PM   #3
rjskalet
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Default Running Lean at 2000rpm partial throttle (tables inside)

Can somebody then explain what relative fuel truly means then. How does it relate to the engine or how it's calculated so I can understand it better and make adjustments based on that because I think that's what's throwing me off when I make adjustments

Edit: is %rf related to the Volumetric efficiency hence why i can achieve 120% at wide open throttle because of me being supercharged?

Edit2: am I better off adjusting the fuel table or alphaN table. I have a wideband so I see when and where I am running lean and I would prefer to hit a target afr and just to make sure I am reading it correct. The lambda value in the fuel table gets multiplied by the global fuel multiplier in order to get the target afr?

Last edited by rjskalet; Thu, Apr-26-2018 at 12:51:27 PM.
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Old Thu, Apr-26-2018, 03:22:48 PM   #4
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Default Re: Running Lean at 2000rpm partial throttle (tables inside)

What AFR figures are you seeing at part throttle?

The O2s adapts should pull you pretty close to 14.7 unless they've been disabled. Have you checked your short term trims to see if the car is pulling fuel?
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Old Thu, Apr-26-2018, 04:27:36 PM   #5
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Default Re: Running Lean at 2000rpm partial throttle (tables inside)

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Originally Posted by MartynT View Post
What AFR figures are you seeing at part throttle?

The O2s adapts should pull you pretty close to 14.7 unless they've been disabled. Have you checked your short term trims to see if the car is pulling fuel?


I haven't checked trims yet but at part throttle from 2000-2500 it's off the wideband so greater than 17. But it's only at that point. And it doesn't do it if I give it 20% or more throttle


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Old Fri, Apr-27-2018, 12:43:36 PM   #6
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Default Re: Running Lean at 2000rpm partial throttle (tables inside)

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Originally Posted by rjskalet View Post
Can somebody then explain what relative fuel truly means then. How does it relate to the engine or how it's calculated so I can understand it better and make adjustments based on that because I think that's what's throwing me off when I make adjustments

Edit: is %rf related to the Volumetric efficiency hence why i can achieve 120% at wide open throttle because of me being supercharged?

Edit2: am I better off adjusting the fuel table or alphaN table. I have a wideband so I see when and where I am running lean and I would prefer to hit a target afr and just to make sure I am reading it correct. The lambda value in the fuel table gets multiplied by the global fuel multiplier in order to get the target afr?
Yes, you are essentially dealing with volumetric efficiency. The first step to properly calibrating an engine is knowing how much air is getting into the cylinders. In the production world we would do this with wideband O2 sensors on each exhaust runner. Say you set your target to .9 lambda, you then tweak your VE table until your exhaust AFR is .9. Most likely there will be some cylinder to cylinder variation, so you will have to calibrate some cylinder to cylinder trims. In the aftermarket no one really tunes with O2s on each runner, so I suppose the general rule is probably to err slightly rich for safety. I haven't dug this deep into the MSS54 yet, but pretty much any ECU will have this capability, so I'm pretty sure it does.

Editing your target lambda table to compensate for incorrect volumetric efficiency calibration will almost certainly have unintended consequences. That being said, if you are moving from an NA to a supercharged calibration, you may need to adjust your lambda targets as well. Richer lambdas provide some knock relief and keep exhaust gas temps down.
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Old Fri, Apr-27-2018, 01:08:16 PM   #7
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Default Running Lean at 2000rpm partial throttle (tables inside)

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Originally Posted by ctres View Post
Yes, you are essentially dealing with volumetric efficiency. The first step to properly calibrating an engine is knowing how much air is getting into the cylinders. In the production world we would do this with wideband O2 sensors on each exhaust runner. Say you set your target to .9 lambda, you then tweak your VE table until your exhaust AFR is .9. Most likely there will be some cylinder to cylinder variation, so you will have to calibrate some cylinder to cylinder trims. In the aftermarket no one really tunes with O2s on each runner, so I suppose the general rule is probably to err slightly rich for safety. I haven't dug this deep into the MSS54 yet, but pretty much any ECU will have this capability, so I'm pretty sure it does.



Editing your target lambda table to compensate for incorrect volumetric efficiency calibration will almost certainly have unintended consequences. That being said, if you are moving from an NA to a supercharged calibration, you may need to adjust your lambda targets as well. Richer lambdas provide some knock relief and keep exhaust gas temps down.


I am already supercharged but is it safe to say it is ideal to find out the VE through the rpm range adjust to hit an AFR and then adjust then adjust the lambda tables to fine tune?

Here is the issue. I am running really lean around 2000-2500rpm. Pretty much interstate cruising speed. If I want to target say 1.05 lambda i would adjust VE. But at what point to you really need to adjust the lambda tables?

Edit: I like knowing how stuff works so I'm just intrigued at this point and trying to learn haha

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Old Fri, Apr-27-2018, 01:28:51 PM   #8
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Default Re: Running Lean at 2000rpm partial throttle (tables inside)

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Originally Posted by rjskalet View Post
I am already supercharged but is it safe to say it is ideal to find out the VE through the rpm range adjust to hit an AFR and then adjust then adjust the lambda tables to fine tune?

Here is the issue. I am running really lean around 2000-2500rpm. Pretty much interstate cruising speed. If I want to target say 1.05 lambda i would adjust VE. But at what point to you really need to adjust the lambda tables?

Edit: I like knowing how stuff works so I'm just intrigued at this point and trying to learn haha

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What supercharger and tune are you running?

Generally speaking you never want to adjust your target lambda for errors in your VE table. In the real world though, you battle all sorts of airflow dynamics in the engine and air inlet system and exhaust, so every cylinder will not get the exact same airflow at every speed load point. This is why fuel trims exist, to make up for small errors in air/fuel calculations. Some engines are worse than others, and typically you will see these errors come and go at different speed/load points due to resonances in the the system. Each OEM has their own way for how fuel trims are applied in their control code, and I really don't understand the MSS54 very well to speak on that. I suspect you will have a tough time getting that answer out of anyone because the reality is that unless you have the source code, you can't really fully understand how the control system works. The A2L, only gives you the labels locations of maps, and from there you can experiment and deduce how it functions. I'm sure most tuners have some understanding of this, but I think they mostly leave it alone.

In your example if you want to run 1.05 lambda at 2000-2500 rpm light load, then you should set your lambda target to 1.05. If you are confident that your fuel system is functioning correctly and delivering the requested fuel, and yet you are still running lean, then you should adjust your VE table until you are seeing 1.05 (or close) in the exhaust. The only time you should change your lambda target, is if you actually want to run a different lambda. So if you decide you want to run .95 lambda, then change your lambda table to .95. If your VE table is correct, you should see .95 in the exhaust.

Oh, and one other very important thing I forgot to mention, you generally want to make sure you have any fuel trims/adaptives turned OFF while you are calibrating VE. Once you are happy with your VE calibration, turn trims/adaptives back on and let them clean up the small errors (this is the beauty of closed loop controls).

Last edited by ctres; Fri, Apr-27-2018 at 01:33:53 PM.
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Old Fri, Apr-27-2018, 01:37:01 PM   #9
rjskalet
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Default Re: Running Lean at 2000rpm partial throttle (tables inside)

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Originally Posted by ctres View Post
What supercharger and tune are you running?

Generally speaking you never want to adjust your target lambda for errors in your VE table. In the real world though, you battle all sorts of airflow dynamics in the engine and air inlet system and exhaust, so every cylinder will not get the exact same airflow at every speed load point. This is why fuel trims exist, to make up for small errors in air/fuel calculations. Some engines are worse than others, and typically you will see these errors come and go at different speed/load points due to resonances in the the system. Each OEM has their own way for how fuel trims are applied in their control code, and I really don't understand the MSS54 very well to speak on that. I suspect you will have a tough time getting that answer out of anyone because the reality is that unless you have the source code, you can't really fully understand how the control system works. The A2L, only gives you the labels locations of maps, and from there you can experiment and deduce how it functions. I'm sure most tuners have some understanding of this, but I think they mostly leave it alone.

In your example if you want to run 1.05 lambda at 2000-2500 rpm light load, then you should set your lambda target to 1.05. If you are confident that your fuel system is functioning correctly and delivering the requested fuel, and yet you are still running lean, then you should adjust your VE table until you are seeing 1.05 (or close) in the exhaust. The only time you should change your lambda target, is if you actually want to run a different lambda. So if you decide you want to run .95 lambda, then change your lambda table to .95. If your VE table is correct, you should see .95 in the exhaust.


Ttfs tuned, AA Stage 2 @ 18psi


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Old Fri, Apr-27-2018, 01:48:06 PM   #10
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Default Re: Running Lean at 2000rpm partial throttle (tables inside)

Before you go making any changes to your tune you might want to get in touch with TTFS.

It would be helpful to provide more details or a log showing lambdas vs. speed and load to help determine if you have a hardware or tuning issue.
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