Different AFRs at the same load point and RPM

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9c1vs
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Different AFRs at the same load point and RPM

Post by 9c1vs »

At certain load/rpm points my AFRs are different depending on the condition at the time. It is most obvious at 80-85kpa @ 2000 rpm:

Condition 1- accelerating and the trace transits through the load point: in order to get my target and actuall afr to match, i have to bump up the ve.

Condition 2 - accelerating at part throttle which holds the load point stead at this point: it runs way too rich at about 11.8:1

I have quad throttle body set up with torque power dual plane hi rise. My throttles are dual stage. I know when the secondarys engage because of the spring pressure on the throttle. When the afr goes super rich, it is when i am accelerating at part throttle just before the secondary butterflies open. Could this be screwing up my MAP sensor reading or something? The only thing i can put it down to is this. I already run a heap of AE and i can see it spike rich when it is engaged, so i think it still needs the fuel on the base map otherwise i get a big lean spike and delay in my actual afr reaching the target and on its way to 90-100 kpa.

I Can post a log if that helps.

Thanks!
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The1
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Re: Different AFRs at the same load point and RPM

Post by The1 »

yep post a log.

Fuel pressure and injectors are all known good?
9c1vs
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Re: Different AFRs at the same load point and RPM

Post by 9c1vs »

I'll post a log tonight. As for fuel pressure and injectors, I can only assume they are okay. The fuel pressure reg seems okay, the fuel pump and injectors are only a few years old. The injectors are super6 ones that i bought from fiveO motorsports a while back to replace the stock 5ltr ones.
9c1vs
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Re: Different AFRs at the same load point and RPM

Post by 9c1vs »

Crane 276 TP Dual plane.bin
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9c1vs
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Re: Different AFRs at the same load point and RPM

Post by 9c1vs »

new plugs 17.xdl
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9c1vs
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Re: Different AFRs at the same load point and RPM

Post by 9c1vs »

example screenshot.JPG
9c1vs
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Re: Different AFRs at the same load point and RPM

Post by 9c1vs »

There are some other areas where it does this as well, but if I drop the ve in the area highlighted on my screenshot, basically it causes a delay in the actual afr dropping to meet the target and causes the AFR to run lean when transiting through the area under heavy acceleration. However, it runs rich when I accelerate by holding the throttle open and steady at part throttle.

I do run a lot of AE. (It is very high in compression and the AE helps prevent pinging. But I think it makes my tune quite scrappy and the actual AFR trace jumps around a lot). But even with that I am still getting this problem of certain RPM/load points giving me different AFRs under different conditions under acceleration. ie: lean spike or on target when transiting to WOT, but running too rich when accelerating by holding part throttle steady.

I hope I have explained this enough! Any help is much appreciated. I have a much longer log if that helps, however the tune is slightly different - i made some slight adjustments.
Dylan
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Re: Different AFRs at the same load point and RPM

Post by Dylan »

Hi mate, only from viewing the screen shot.
The first red circle is under acceleration and AE will be in effect.
The second one is more steady state. They would also be in different MAP readings which play's a huge part in VE.

Given the different intake the manifold fuel part of the acceleration enrichment calculation would need altering.
That can help with the delay with AE taking effect.

Also with the different intake the coolant contribution table will need some work along with the charge temp table to help stabilise the actual AFR.

I'll have a run of the log tomorrow night.
9c1vs
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Re: Different AFRs at the same load point and RPM

Post by 9c1vs »

Dylan wrote:Hi mate, only from viewing the screen shot.
The first red circle is under acceleration and AE will be in effect.
The second one is more steady state. They would also be in different MAP readings which play's a huge part in VE.

Given the different intake the manifold fuel part of the acceleration enrichment calculation would need altering.
That can help with the delay with AE taking effect.

Also with the different intake the coolant contribution table will need some work along with the charge temp table to help stabilise the actual AFR.

I'll have a run of the log tomorrow night.
Hi Dylan, they both run through the 90kpa area i have highlighted by the red square, it will show up on the log. You gave me a hand with this tune a couple of years ago which i really appreciate. I got it to a point where it drives pretty well and lost time and interest to keep working on the tune. But I am motivated to have a play around with it again and do some work at tidying things up again now!
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vlad01
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Re: Different AFRs at the same load point and RPM

Post by vlad01 »

Most likely the charge temp and manifold heat soak looking how high your MAT reading are in general and they do change a lot from the 2 instances you point out.

I have seen a similar thing going on with the v6 too, mainly when heat soaked coupled with stock airbox as they keep the air temps high.

It can be tuned out with the items Dyan mentioned but I found just managing the air intake temps mitigated the situation in the first place.
I'm the director of VSH (Vlad's Spec Holden), because HSV were doing it ass about.
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