TPS Enrichment

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md_sanci
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TPS Enrichment

Post by md_sanci » Wed Jul 03, 2019 7:26 pm

Hello all,

Today i did some testing on the car, if you are not up to date, i am trying to run rusefi on a 1.5 liter ITB setup.
I have to check, i saw that in MS they have ITB mode, but the guy that i am working for he wants to use Alpha N.

So with ITBs this getTpsEnrichment will not wok, since between two engine cycles i will never have a tps movement that bit to detect it, and if i set the delta low, it will react to the noise that is read from the sensor.

I did the following: we have tpsAccelLength that is used in the circular buffer setup (length of the buffer) and i am looking for a movement in tpsAccelLength/2. This way now with itbs i can compensate on sharp to medium tps changes and i can get the extra fuel needed.

Now with slow TPS changes, i cannot get the extra fuel, and i have noticed that MAP value will decrease and O2 will go lean.
I plan to make correction when ITBs are almost closed based on MAP value changes as well.

If somebody has more info on how do the MS ITB mode algo is working, it would be a good starting point.

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andreika
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Re: TPS Enrichment

Post by andreika » Thu Jul 04, 2019 4:37 am

md_sanci wrote:
Wed Jul 03, 2019 7:26 pm
So with ITBs this getTpsEnrichment will not wok, since between two engine cycles i will never have a tps movement that bit to detect it
rusEFI firmware works with ITBs just fine, including speed-density and TPS-TPS enrichment.
Have you tried setting "Fraction Period" and "Fraction Divisor" options?

md_sanci
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Re: TPS Enrichment

Post by md_sanci » Thu Jul 04, 2019 6:15 am

andreika wrote:
Thu Jul 04, 2019 4:37 am
md_sanci wrote:
Wed Jul 03, 2019 7:26 pm
So with ITBs this getTpsEnrichment will not wok, since between two engine cycles i will never have a tps movement that bit to detect it
rusEFI firmware works with ITBs just fine, including speed-density and TPS-TPS enrichment.
Have you tried setting "Fraction Period" and "Fraction Divisor" options?
Hello,

Yes i have played with those values and even with length.
I took a look in the code and what i understood is that it is searching max delta between two consecutive engine cycles. I can never get that delta in real life to be bigger then 0.8 at very hard tps movement.

This is why i have opened this topic to try to clarify what is going wrong on my side. Let me explain what have i understood.

At every handleFuel call we update tpsAccelEnrichment.onNewValue -> this will push a new value in cb fifo. Fifo size is TPS lenght (in cycles) from TS.
Now when we look up to get the enrichment getTpsEnrichment we look in the fifo and get the max delta. But the max delta is between two consecutive values. In my logic this means the delta is really between two engine cycles and not in the length that i would have been expected while reading the wiki on fuel control.

So what i have done is 2xTPS length is the real value of the fifo size, and looking max delta between current index and index - tps length.
This way i can see differences between debug fields 1 and 2. and the engine is really happy. I can get good throttle response, and the fuel table is not too rich (before i had to compensate to do good acceleration).

I am trying to understand and trying to help.

SPEED Density: yes i read that this is working fine, i have to test it, but it is not my car and the owner wants AlphaN so i have to make it work.

Last night i have done a bit of testing of adding extra fuel based on MAP as well, to compensate on not that sharp tps movement, but MAP movement, this is the case with ITB between 0% ~15..20% tps with light tps change.

tpsAccelFractionPeriod is used for evenly split it between several engine cycles
tpsAccelFractionDivisor is used to get a portion of the calculated value: use only a fixed fraction of the accumulated portion

OrchardPerformance
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Re: TPS Enrichment

Post by OrchardPerformance » Tue Jul 09, 2019 8:57 am

Couple of questions -
You say you have TPS noise activating the AE (or at least the risk of it), what TPS do you have and are you seeing any noise? I can say on my BMW setup there is no noise at all on the TPS signal and I was able to run quite low TPS deltas without triggering it accidentally.

Can you post a log and the tune you are using? It would be good to know what what you have in your settings for the enrichment.

The length was working last time I tried it, I found setting the length to a value that matched the number of combustion cycles in 0.5 seconds at 2000rpm worked well for me, for a 4 cylinder that is ~34 cycles and for a 6 that's 50 cycles.

Out of curiosity, what size throttles do you have on the 1.5? Past experience tells me a lot of aftermarket stuff tends to fit throttles that are much too large and this only makes things harder as throttle movements become smaller and drivability falls.

Edit - The MS method appears to be to use the MAP sensor to do the low throttle angles and switch to TPS above a certain load point. This has couple of weak points. Most throttle body setups have no MAP sensor and no way to really fit one, without complex piping your only sensing the MAP on one throttle and that fluctuates badly. MKE has a multi-MAP setup on his V12, that is multiple MAP sensors set up so that only the highest sensor value is ever sent to the ECU. (that also has some issues but it works just fine). The other big thing is Alpha-N is really only something to go for when there is no better option, its poor at dealing with barometric changes and has bad low load drivability it's real application is heavy cammed race cars and the like where you can't get a good tune with a MAP due to the manifold pulsations and a MAF is too restrictive, using the MAP value at low throttle positions does not help this situation at all.

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andreika
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Re: TPS Enrichment

Post by andreika » Tue Jul 09, 2019 6:01 pm

OrchardPerformance wrote:
Tue Jul 09, 2019 8:57 am
without complex piping your only sensing the MAP on one throttle and that fluctuates badly.
It's not that bad in rusEFI:
1) We have "MAP Sampling Start Angle" and "MAP Sampling Duration" - very powerful instrument;
2) We have nice and smooth MAP averaging (isMapAveragingEnabled=true by default);
3) We have "Measure Map Only In One Cylinder" and "Minimum MAP samples" settings - specially for ITBs and non-standard intake manifolds.

I have only 1 MAP sensor (MPX4250A) for my 4-cyl ITBs (Y-style common junction piping) and even without thorough tuning the MAP readings are rather stable:
sensor-map-itb_idle_900rpm_30_sec.JPG
sensor-map-itb_idle_900rpm_30_sec.JPG (19.94 KiB) Viewed 110 times

OrchardPerformance
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Re: TPS Enrichment

Post by OrchardPerformance » Tue Jul 09, 2019 6:50 pm

That is actually impressively stable, to the point of making the Alpha-N a little redundant. MAP windowing is a really good thing for us to have, combined with the other settings that's actually a pretty powerful toolset.

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Re: TPS Enrichment

Post by JRD McLAREN » Tue Jul 09, 2019 7:11 pm

andreika wrote:
Tue Jul 09, 2019 6:01 pm

It's not that bad in rusEFI:
1) We have "MAP Sampling Start Angle" and "MAP Sampling Duration" - very powerful instrument;
2) We have nice and smooth MAP averaging (isMapAveragingEnabled=true by default);
3) We have "Measure Map Only In One Cylinder" and "Minimum MAP samples" settings - specially for ITBs and non-standard intake manifolds.
this is the reasons, why I'm choose rusEFI ... 8-)

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