AAC Valve Behavior

Nistune topics related specifically to the 6303 cpu

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my1path
 

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AAC Valve Behavior

Post by my1path »

M30 ECU (for automatic trans) 5speed manual is being used
This has been a small thing that has been going on for years even before Nistune was installed. I'm just wondering if might be something in nistune that could change it.

Whenever the engine comes down to idle, especially after cruising for a while, it idles high (maybe 1200+ on a cool day, less on a hot day) for about 10 seconds before settling down to its normal setting. If I look at the AAC in nistune it will ramp up to 80% while driving and slowly go back down when the throttle is closed. Idle is usually about 20-26% when the engine is warmed up and setting target idle speed lower than the physical idle screw setting reveals that 20% is the lowest duty cycle for the AAC.

My assumption is that it comes from being an automatic ECU to keep the torque converter from bogging down the engine when the vehicle is stopped.
But since I am driving a Manual there is almost zero drive train drag on the engine at a stop so instead, I notice a rise in idle.
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Re: AAC Valve Behavior

Post by Matt »

The ECUs have some tables relating to AAC duty, which i have found in some ECUs (such as HCR32 RB20) but I don't have the definitions available for this one. I was under the impression all M30 were AT?
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Re: AAC Valve Behavior

Post by my1path »

Matt wrote: Tue Sep 17, 2019 9:44 am The ECUs have some tables relating to AAC duty, which i have found in some ECUs (such as HCR32 RB20) but I don't have the definitions available for this one. I was under the impression all M30 were AT?
You are correct, all M30 were AT.
This is a swap, MT pathfinder with an M30 ECU, z32 MAF and VG33er 344cc injectors.

The weather is getting colder and the AAC seems more responsive to cold air. Today it pulled my idle up to 1,500 (80% in consult) when I cam to a stop in front of my house. It came down to 23 over a span of about 10 seconds.

Just now I added some idle stabilization retard, tomorrow I'll find out if that band-aid works.
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Re: AAC Valve Behavior

Post by my1path »

my1path wrote: Fri Sep 20, 2019 10:47 am Just now I added some idle stabilization retard, tomorrow I'll find out if that band-aid works.
Not much, it seems ECU will not use idle stabilization retard at the same time as its holding the AAC open.
But as soon as AAC drops to 20-30% idle stabilization retard kicks in.
In summary it still high idles when I come to a stop (about 10 sec) but when it decides to come down it comes down a little faster.
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Re: AAC Valve Behavior

Post by Matt »

There is not much more that can be done unless the idle stablisation tables are identified. However the M30 VG30E code is quite different from RB20DET so that would be difficult
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Re: AAC Valve Behavior

Post by my1path »

Matt wrote: Tue Oct 01, 2019 11:39 am There is not much more that can be done unless the idle stabilization tables are identified. However the M30 VG30E code is quite different from RB20DET so that would be difficult
Today was colder AAC pulled up to 1800 RPM in the parking lot getting to work.
I don't know if this helps but the AAC responds very well to changes I make in the target Idle speed table.

Slightly off topic but with this AAC, timing, and today seeing that below a certain temp it doesn't matter what my enrichment table says my engine will warm up at 10:1 and i'm sure there's other quirks... it just seems like there are a lot of things that don't behave as ideally as they should on the M30/Nistune setup. Is there a 6 cyl ECU that works better with nistune?
I hope to be boosting by the new year and I'd like to iron out as much as I can before then (erratic timing behavior scares me). Would a 1993 USA Pathfinder MT (wd21) ECU work with nistune? That's the chassis I am working with, all my engine electrical (except the injectors and MAF) come from a 1993 pathfinder so it would stand to reason there would be less tweaking required to get it to play nice and I could spend more time on the main maps.
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Re: AAC Valve Behavior

Post by Matt »

I'm not familiar with setup, but the M30 ECU should run same as factory with the Nistune board installed, if it is a different vehicle/engine then some M30 specific operations might work differently? We don't have a board for the engine you mention

Log of warmup would be helpful
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Re: AAC Valve Behavior

Post by my1path »

Matt wrote: Thu Oct 03, 2019 11:35 am I'm not familiar with setup, but the M30 ECU should run same as factory with the Nistune board installed, if it is a different vehicle/engine then some M30 specific operations might work differently? We don't have a board for the engine you mention

Log of warmup would be helpful

I feel like not the M30 tables don't always do what they are told like there are some other unknown parameters the effect them. I know the M30 was a rare car and I understand that nistune may not be as well developed because of that. Heck, I think I'm the only one on here asking M30 ECU questions.
In america we also have the 84-89 z31 300zx, 87-88 200sx S12 SEv6 and 85-94 nissan maxima that all run similar engine equipment. Is one of those considered "best" for nistune?

I'll see about getting a warm up log posted, weather says tomorrow may not be as cold but we'll see what the log says.
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Re: AAC Valve Behavior

Post by my1path »

I think I figured something out, I believe they're used to be multiple enrichment tables for cold start and for warm start...

It wasn't very cold when I took a log yesterday but it was cold enough for me to see the fuel ratios were not following the temp enrichment table and changes made to the highlighted cell (and adjacent cells) did nothing. However, when I turned the engine off and started it again it did follow the enrichment table and also responded to real-time changes. So the enrichment table showing in nistune must be for warm start and the table accessed below a certain temperature must not be visible right now. So think a cold start Temp enrichment table needs to be come back.
Nistune_2019-10-04_0604_54.csv
(579.7 KiB) Downloaded 65 times
Engine start ambient temp was about 58-60F AFR's were in the lower 12's
On 30 sep (no log) engine start ambient temp was about 32-36F AFR's were as low as 9.8:1 but mostly low 10's. Sorry I do not recall at what temp they moved to the 12's but it was probably around 50-60F.
I'm guessing below 20c (68F) is when the ECU accesses the cold start map. (summer ambient temps here are always above 70 even at night)
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Re: AAC Valve Behavior

Post by my1path »

Quick check this morning:
-- 46F started ran 11:1, zeroe'd highlighted cell and adjacent: no change.
-- shut off engine at 72F, let ecu power down
--Restarted engine (80F) ran 13:1 per the map, zeroe'd highlighted cell and adjacent: Real-time change reflected 14.9:1~15:3 AFR
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Re: AAC Valve Behavior

Post by my1path »

I did see
#Not used

...

COLD_START_ENRICH,&H0000,0,0,0,0
WARM_START_ENRICH,&H0000,0,0,0,0
Would it be as simple as moving one of those lines to this area? or do I have to turn the zeros into some other numbers first?
#Additional maps
TEMP_ENRICH,&H7EB0,16,1,16,1
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Re: AAC Valve Behavior

Post by Matt »

Remove those two lines COLD_START_ENRICH and WARM_START_ENRICH and also the TEMP_ENRICH lines. It will use the defaults from the base file

Looks like I should have put these changes only in the FP M30 address file, since you would be using the non-FP address file
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Re: AAC Valve Behavior

Post by my1path »

I can totally see why it would have a different enrichment table for colder start. Engine may be warming up but if its still sucking in freezing ambient air a little more enrichment is necessary. I thought I saw 9.7:1 the other cold morning and richer and I think the engine will stumble. My injectors are nearly 200% larger than stock, could that be exaggerating the problem despite having dialed in the K and latency?
Last edited by my1path on Fri Oct 18, 2019 4:04 pm, edited 1 time in total.
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Re: AAC Valve Behavior

Post by my1path »

I made the changes you mentioned. The screen shot shows the stock cold enrich next to my warm enrich table. Value of 15 puts me about 12:1 and the cold enrich table is dramatically richer. Based on the temps shown I think this is exactly the behavior I'm getting on cold mornings.
Temp enrich capture.JPG
(93.09 KiB) Downloaded 1469 times
The tool tips say greater/lesser than 15c(59F) so In the morning I will plug this in and see if it allows real time changes below 15c(59F) and report back.
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Re: AAC Valve Behavior

Post by my1path »

my1path wrote: Fri Oct 18, 2019 4:03 pm The tool tips say greater/lesser than 15c(59F) so In the morning I will plug this in and see if it allows real time changes below 15c(59F) and report back.
Cold start and Warm start Maps now respond to real time changes based on startup temp.(Highlights are correct too).
Good timing on this one as our winter is approaching.
Matt wrote: Tue Sep 17, 2019 9:44 am The ECUs have some tables relating to AAC duty, which i have found in some ECUs (such as HCR32 RB20) but I don't have the definitions available for this one.
How difficult a task is this? Is it easier attempted on my end since I have ECU on hand?
Would copping the corresponding line from other ECUs into mine and until it works be an approach I could tackle?
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