Idle stalling TP Load limit decel

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madaxgt
Posts: 14
Joined: Mon Feb 06, 2017 7:16 pm
Location: Goteborg, Sweden

Idle stalling TP Load limit decel

Post by madaxgt » Fri May 29, 2020 3:55 am

Hi

I have been struggling with this for a few weeks. I have stalling coming down to idle from high engine speed in neutral. Also if I clutch in coming to a stop it dies. Its usually goes rich as can be seen from black smoke as it tries to catch. Its a MAF issue for sure but I cant seem to solve it so far.

Car is a bnr32 rb26 with a single maf conversion R35 GTR maf sensor in a 4" tube with a straightener. Once its idling its ok and you can load it up at idle speed (clutch against the handbrake) and its find good, afr and no stalling. It seems there is no real dashpot function for idle that bumps the AAC as you approach idle target or even a spark dashpot function. The idle stabilisation function doesnt seem to solve it or maybe I still have it calibrated wrong. Is it in the manual?

The MAF voltage climbs much higher than steady idle speed when it tries to catch it clearly false reading so I tried the Load limit decel function but this doesnt seem to function as I expected or explained. I set decel tps to 0.5v trigger
and kept lowering the load limt all the way down to 10 above and below idle speed. TP is around 2000 (7-8) at idle. But it doesnt seem to limit it to the value in the table and I see the pulswidth increasing and TP up to crazy numbers.

I have FP2 but its classed as a FP2.2 function, do i need to reflash firmware for it to work? I see nothing new in the rom packs...

Ill attach the cal file ive been using. I started from scratch to see if I could solve it but alas no.
Log of driving near stall (200rpm!) around 1m 25s
2nd log of stalling in neutral.

Can also see in the driving stall that the hot start is not great (maybe i am missing something) but i havent bothered to look at that yet. Cold start is good.
Attachments
Nistune_2020-05-24_1840_37.csv
(517.29 KiB) Downloaded 9 times
_2020-05-28_1635_23.csv
driving stall
(365.94 KiB) Downloaded 9 times
2019_Single_Idle_Stall.bin
(32 KiB) Downloaded 9 times

Matt
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Re: Idle stalling TP Load limit decel

Post by Matt » Sun May 31, 2020 12:23 pm

What is happening as per your log (and pic below) is the MAF is still sucking through airflow since the turbo is probably still spinning whilst you are decelerating

What that means is the ECU is seeing load (purple) and that increases as RPM drops (you can see it rise in the picture). We want to avoid that where possible. Use of a BOV plumpback will vent the excess airflow off boost, but having bends between the turbo and MAF also helps avoid the airflow still being sucked through

On the tuning side of things, where you see the cursor going along the bottom to the right, as it further goes accross, it adds more fuel

I'm working on firmware updates to cut the fuel past the purple line you see in the picture in the FP2.1 firmware (not yet available) for various ECUs. I've got it working on my R34 which is the good news but adding in knock reporting and getting hounded for flat shift and a few other things. I've done test code for the BNR32 but need to vehicle test it.

In the meantime, drop the values in the 800-1200 column above TP=28 to as low as possible to combat the extra fueling. Once I have the firmware done and available on the first select models (including BNR32) then we could update your board to cut the extra fuel at the purple line area
Attachments
2020-05-31 10_45_51-Nistune [BNR32 (RB26DETT) Feature Pack 2.0  (Version_ 3)].png
2020-05-31 10_45_51-Nistune [BNR32 (RB26DETT) Feature Pack 2.0 (Version_ 3)].png (49.39 KiB) Viewed 193 times

PL
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Re: Idle stalling TP Load limit decel

Post by PL » Sun May 31, 2020 12:34 pm

Does the car still have the factory BOV's? I've done quite a few GTR's and they all returned to idle nicely until I got one customer who refused to run BOV's. Spent many hours trying to make that one work. Gave up in the end.

PL

madaxgt
Posts: 14
Joined: Mon Feb 06, 2017 7:16 pm
Location: Goteborg, Sweden

Re: Idle stalling TP Load limit decel

Post by madaxgt » Sun May 31, 2020 8:21 pm

Ok will try dropping those cells until you release the new code.

Yeah there is definately something weird going on in the maf sensor at these conditions. Its a single turbo swapped rb26 with a single R35 maf in a 4" tube with straightener. Unfortunately its impossible to install a filter thats of any useful size with out a bend before the turbo and maf. I already extrapolated the lower end of the maf curve to get idle fuelling reasonable.
Pl, yes it has a compressor bypass built into the compressor cover (I am assuming its working but will double check it.) I also have a crankcase vent return just in front of the compressor, I can check this also isnt flowing excessive air...

Think i am one of the people 'hounding' you for flat shift.... :oops: :oops:

edit. I have a board programmer so I can test the new firmware if you want. You could teamview my computer if you want to verify or I could just send some logs.

Thanks for the help :)

Matt
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Re: Idle stalling TP Load limit decel

Post by Matt » Mon Jun 01, 2020 1:55 pm

Yeah I'm just trying to find time for doing the new firmware. I have to do Z31 1986 first (due to pending issue) and then Z32/BNR32 after that. Flat shift code still take another week to code/teset

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