S14 SR20DET holding on to closed loop??!?!?!

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Re: S14 SR20DET holding on to closed loop??!?!?!

Post by Matt » Wed Apr 24, 2013 10:55 am

Will investigate this and get back

bmoses
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Re: S14 SR20DET holding on to closed loop??!?!?!

Post by bmoses » Sat Jun 15, 2013 3:28 am

I am battling this exact problem and will try experimenting based on this information. My tune is great everywhere except in the part throttle, low/mid rpm, high load area. The ecu just wants to hang on to stoich causing some hesitation, bucking and general not a good ramp up to boost. Once I get past this it's gravy, but until high boost, high load are achieved, it sucks. I can kinda mask this problem by always creating a large throttle transients and letting those TPS % changes provide the extra fuel for good spool up. It appears by the time that fuel wears off the ecu's reading from your high load columns.

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Re: S14 SR20DET holding on to closed loop??!?!?!

Post by bmoses » Sat Jun 15, 2013 11:59 am

OK, What diehard did and Adrian explained has worked for me!! Thank GOD! I just went ahead and added 192 to the whole map and left the O2 feedback disabled. This is ok for me because I run in open loop all the time anyway. I'm not sure what the ECU would do with these bits set what's normally the open loop area of the map.

It's weird how Nissan has done this though. Someone correct me if I'm wrong here, but with an 8 bit table value Nissan is using the msb for closed/open loop switch or alpha feedback, (we're not sure yet), then if this bit is set, the next significant bit is now a sign bit, leaving 6 bits for an actual value giving you 64 steps greater than 0 and 64 steps less than zero. Is my understanding here correct?

I've been tuning for a while, but I'm new to Nistune.

Thanks community,
Ben

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Re: S14 SR20DET holding on to closed loop??!?!?!

Post by MomentFD » Fri Mar 07, 2014 2:52 am

Is there any news on this topic? I'm not having a problem at the minute but I'm about to get into tuning my S14 SR and this topic sparked my interest.

How did you guys know it's holding onto closed loop? The near 14.7 AFRs?

Matt or PL, did you guys ever find anything in the code?

Thanks all

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Re: S14 SR20DET holding on to closed loop??!?!?!

Post by Matt » Mon Mar 10, 2014 6:25 pm

Havent seen anything in the code. I've got an S14 so going to investigate once I can get on the dyno again

So far on the bench with changes between map areas seen the ECU hold injection for 4 seconds if a large change between fuel map cell transitions

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Re: S14 SR20DET holding on to closed loop??!?!?!

Post by Matt » Mon Mar 17, 2014 9:46 am

Due to broken finger... cannot drive manual for another three weeks minimum so dyno is delayed

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Re: S14 SR20DET holding on to closed loop??!?!?!

Post by PL » Mon Mar 17, 2014 10:49 am

I did another S14 track car last week (74F00 + 1000cc inj, Z32 AFM on E85) and just left O2 sensing disabled (in the flags section) and turned all cells off in the fuel maps. Worked perfectly. I guess it's hard for it to hold closed loop when it never goes closed loop...

Wish I could say the same about the Turbosmart ext WG which completely failed to do anything good. And I thought they were the good ones! TIAL gate going back on for re-tune this week.

PL

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Re: S14 SR20DET holding on to closed loop??!?!?!

Post by bmoses » Mon Jun 02, 2014 1:27 am

So is there anything new on this front? Any address values discovered that would allow changing either TP value or RPM at which closed loop is cut?

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Re: S14 SR20DET holding on to closed loop??!?!?!

Post by unreal- » Mon Jun 02, 2014 5:37 am

Looks like the same thing is going on for us KA guys:

viewtopic.php?f=12&t=1702

And my post from that thread:
unreal- wrote:My issue is similar in that if my primary o2 is connected, the car will not only hold on to closed loop, but I get a nasty lean spike to 16-17.0afr and once the revs go past 3200 or so it clears up and holds onto closed loop if im accelerating slowly, or map values if WOT. If I accell briskly from a stop its a HUGE hesitation that makes the car buck, as if im holding the brakes at the same time.

If I disconnect the primary o2 and run open loop I get no lean spikes AT ALL, regardless of throttle position. This is with 3 different sensors ( 2 oem denso (1 wire and 3 wire) and 1 bosch 3 wire) so I know it has nothing to do with the sensor.

Weird.
So i've been running open loop for the past 6 months without issue. MPGs are identical (17-18 If im hauling ass, and 20-22 if i drive like Daisy) I would love to run an o2 sensor, but this lean issue is preventing that.

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Re: S14 SR20DET holding on to closed loop??!?!?!

Post by bmoses » Mon Jun 02, 2014 1:14 pm

Unreal, nice to see you here. :) I've been absent from the 240sxforum for a while. I have also been running in open loop for years, but every year I attempt to retune the "right" way using closed loop, O2 feedback etc, and it always ends in disapointment. This year I had a hesitation on quick throttle transient that led me to again, try to start over which led again, to the same disappointing end. I gave up today and plugged in my open loop values, disabled O2 feedback and went about my way fine tuning my tune... AGAIN. It's just kinda frustrating not knowing why we can't do it "right" I also get about 17 to 18 mpg on E85, mostly highway miles.

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Re: S14 SR20DET holding on to closed loop??!?!?!

Post by Matt » Tue Jun 03, 2014 11:41 am

It may to be with movement of TP from factory values and the need to rescale.

I've got an S14 myself and still to investigate this one further. At this point I've added another injection adjustment constant which does not move TP, leaving the O2 values at factory

I would be interested to know how far from factory K constant you are currently running

I've been adding further code disassembly for the S14 models but not go into the closed loop area too much yet

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Re: S14 SR20DET holding on to closed loop??!?!?!

Post by unreal- » Thu Jun 05, 2014 6:19 pm

bmoses wrote:Unreal, nice to see you here. :) I've been absent from the 240sxforum for a while. I have also been running in open loop for years, but every year I attempt to retune the "right" way using closed loop, O2 feedback etc, and it always ends in disapointment. This year I had a hesitation on quick throttle transient that led me to again, try to start over which led again, to the same disappointing end. I gave up today and plugged in my open loop values, disabled O2 feedback and went about my way fine tuning my tune... AGAIN. It's just kinda frustrating not knowing why we can't do it "right" I also get about 17 to 18 mpg on E85, mostly highway miles.
Mr Moses, good to see you are still kickin 8) Looks like you are having the same hesitation issue that i was having.
Matt wrote:It may to be with movement of TP from factory values and the need to rescale.

I've got an S14 myself and still to investigate this one further. At this point I've added another injection adjustment constant which does not move TP, leaving the O2 values at factory

I would be interested to know how far from factory K constant you are currently running

I've been adding further code disassembly for the S14 models but not go into the closed loop area too much yet
How will we be able to modify the new constant? or will it be explained later on once the code is complete?


In my case (KA24DE, obd1 S14 ECU), i have 440K value, and 500us injector latency with 580cc Five 0 Injectors. It is the only way i can get the car to cooperate. If i run a somewhat "normal" K value that Nistune calculates (in the 200 range), and "normal" latency of 500 us, the car will not even try to start. I have to raise the injector latency to almost 1000us in order to compensate for a normal K value, and that leads to my car acting really sluggish and weird on decel while in gear, and tuning idle is very difficult.

Funny thing is that the fuel maps barely have to be modified beside the usual expected values for a boosted setup, and the VE just needs a fair amount of trimming in the right side of the map so it doesnt flood the motor. Unfortunately, if i were to run "normal" values, there isint enough resolution in the maps to even begin to compensate.

It took a while, but i finally managed to get my maps to the point where i have the AFRs that i expect (14.5-15.0 idle, ~12.5 @ 0 psi and 10.8-11.5 WOT)

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Re: S14 SR20DET holding on to closed loop??!?!?!

Post by Matt » Thu Jun 05, 2014 8:27 pm

and the VE just needs a fair amount of trimming in the right side of the map so it doesnt flood the motor
So we are talking S14 KA42DE here... title is S14 SR20DET but same issue it seems

There is an injection adjust constant in the S14 KA24DE which may be able to be modified to leave K where it is. Doubling K can affect the O2 lookup tables (which are dependent on TP which is affected by K accordingly)

Let me look into this one next week for you once things settle down this side (been working stupid hours this week trying to keep up with things)

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Re: S14 SR20DET holding on to closed loop??!?!?!

Post by unreal- » Sun Jun 08, 2014 7:06 am

Matt wrote:
and the VE just needs a fair amount of trimming in the right side of the map so it doesnt flood the motor
So we are talking S14 KA42DE here... title is S14 SR20DET but same issue it seems

There is an injection adjust constant in the S14 KA24DE which may be able to be modified to leave K where it is. Doubling K can affect the O2 lookup tables (which are dependent on TP which is affected by K accordingly)

Let me look into this one next week for you once things settle down this side (been working stupid hours this week trying to keep up with things)
Thanks 8) This will really help out a lot of the S14 KA-T guys when the constant is available.

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Re: S14 SR20DET holding on to closed loop??!?!?!

Post by bmoses » Mon Jun 16, 2014 1:56 pm

Hi Matt,

Yes, like Unreal, I am running a KA (98 MY) with a 91 ECU. I have no VE map. My K went from 39720 to 21200. Your injector resizing and MAF adjustment functions seem to be pretty spot on. I had to increase K only slightly to get where I wanted to be. Like unreal, I didn't have to touch my fuel maps that much at all. I did generally decrease all values by a percentage, normalizing them towards 0 or 192. I did this because each "step" of increase or decrease away from 192 is a larger step than it was when K was at 39720. I have fine tuned WOT since then. I am running 850cc injectors on E85 and went back to using the stock FPR at 3 bar. I was using a Nismo FPR set at approx 4 bar, but I wanted to eliminate variables. I didn't need the extra fueling and that let me raise the K value a little bit more, getting it closer to stock. My max TP's come in at just over 100. My car is running great, my idle and low loads are stoich and with the msb set in all fuel cells and O2 disabled I am able to command richness at throttle tip which results in freakin awesome mid RPM throttle response and boost building. The thing that bugs me is that this isn't the way it should work. I'm forcing the ECU to think the whole fuel map is closed loop and then telling the ECU to disregard O2 feedback and not apply trims.

Otherwise everything else is gravy :)

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