re-mapping and live tuning L28ET 1982/83 S130 ECCS

[stupid_fast]

I made a mistake by saying 'air flow would be consistent'.  

I'm trying to figure out the explanation as to why there's a severe drop in AFR after a certain RPM, but the fueling would remain constant with a flat AFR target above that value. 

[Gollum]

Likely because you DON'T have a "VE" table anywhere. You have an "AFR" map as your only "fuel" map (that you've posted or shown me). There's an ignition map, but that's unrelated. So once the AFM is maxed out, the ECU likely takes that reading as it's "max flow" reading and the AFR table adds fuel on top at higher RPM where necessary. This means that in WOT beyond max AFM flow you're only operating on RPM scale, like an alpha-n would at WOT.

Edited April 4, 2019 by Gollum

[bradyzq]

Yup. Your main fueling is calculated from the AFM voltage and RPM. No VE. Though there may be an as yet undiscovered WOT fuel map that is unrelated to or a further multiplier of AFM fueling.

 

@Gollum, sorry. I thought the MS logs stupid_fast was referring to were yours.

 

Also, if one is trying to figure out how this stock file works on a modified engine, you may get some weird things going on, such as going off the end of tables. You can see that a stock boost 280ZX likely would have followed a slightly leaner AFR trace, and maybe not hit the last TP column.

[stupid_fast]

I was referring to Gollum's megasquirt logs.


I've just updated the rom data translation spreadsheet with my more recent findings. 
https://github.com/eccs-reengineering/280ZX-Turbo-ECCS/blob/master/Rom Data Translation/S130T_ROM_Address_Translation.xlsx

You're welcome to look, and if you have any questions about a specific table I can test the results of changing it.  I've modified and tested almost every bit of used data while the engine is running to find out what it does.
I've verified which maps are in fact used, and which are not by checking which tables are referenced and loaded by the assembly code. 
 

The next step is to verify if in fact the AFM is hitting its limit. 
If so, the real solution would be finding a way for the ECU to measure flow past the AFMs max flow capability. 

 

 

Edit, found what appears to be the injector constant (Generally referred to as the K constant in the Nissan world) it is a DWORD at 1F44 on the stock rom.
Adjusting this dword changes fueling characteristics across the whole range. 
 

Edited April 6, 2019 by stupid_fast

[dogmeatk]

On 3/31/2019 at 9:25 PM, stupid_fast said:

 

Well this is very interesting! I am in the middle of slapping my turbo onto my l28et block with NA mechanical distributor (it's a long story) just until I finish my speeduino build. I have been concerned about the ignition timing, I have seen many here advising to lock the mechanical advance and disconnect the vacuum advance and set it to 20 BTDC. However ... I am looking at your rip of the stock ignition table and noticing that the turbo motor has a similar amount of advance, especially in the low-load condition. If AtlanticZ is correct, the stock NA Dist with vac and mech advance would be putting out 37-50 (depending on year) BTDC at 2500 RPM at full vac. At full load 2500 RPM, this would be 27 BTDC, only 5-9 degrees off of the stock turbo ignition map? Am I reading that correctly? Then At full load, full RPM, I would be at 27 BTDC, only a few degrees later than the 31 BTDC turbo target?

 

It sounds like the NA dist has a pretty close approximation to the Turbo CAS map .. why does everyone disable the mechanical features and run at 20 BTDC static advance??

 

Edit: BTW stupid_fast is a legend for ripping this ROM and hacking it so beautifully. Hex makes my brain gloss over and you are awesome for banging into this.

Edited March 31, 2021 by dogmeatk
Props

[stupid_fast]

For drivability you really want good amount of advance in the low load areas.  I never really understood why anyone would remove vacuum advance, since with the correct weights setup it runs the same at the top end anyway. 

The stock map has a lot of advance.  remember however it had 7.4:1 compression, motors with flat tops and NA motors will take a lot less ignition timing reliably especially with the stock j-pipe.

I just built some knock ears and I'm still getting light knock at around 5200rpm with only 24 degrees timing at a 12:1 AFR on the j-pipe and stock wastegate. 
My motor is around 7.9:1 compression.   I was probably saved before by the motor running very rich mid 10:1's on boost. 

These motors hit mbt around 20 degrees at 3000rpm (at 6psi), and they're prone to knock in the 4400-4800 range. 

Really the take away from this is just make sure you have some kind of audible knock detection when you start rolling into the boost for the first time, there's no real replacement for a good ECU with proper spark control. 


I was collecting some more information before doing a final update and conclusion for this thread, which is most likely going to end with my car running on a dropbear ECU. 

It was fun to go in and verify or debunk rumors on how things worked inside the factory ECUs. 

Edited March 31, 2021 by stupid_fast

[dogmeatk]

thank for the tips stupid_fast! I am actually running the 7.4:1  stock compression on the turbo block. I just so happen to have NA ignition lol! I don't plan on running anything more than 3-4 PSI boost until I finish my speeduino setup and get some bigger injectors, I am just doing some due diligence to make sure I don't blow anything up in the meantime. I actually have the knock sensor still in the block, just no way to read it  Ive been through the FSM a few times and still havent been able to determine if the NA ECU has  any electronic ignition retard or if it is timed purely off the mechanicals, any idea?

[dogmeatk]

Also, what's the deal you mentioned with the stock J-pipe? Is it doo-doo? I don't have a stocker so I am making one out of 2" aluminum tube.

[stupid_fast]

J-pipe is fine its just non-intercooled so its more prone to detonation due to the higher intake temps.
You should be able to run quite a bit of power as long as the timing is conservative and you keep it a bit rich.

The NA ECU has no ignition control, the advance curve is mechanical like a carbureted car.
I'm pretty sure there have been NA-T guys on hybridz who have run a stock dizzy without problems, you should be able to find some old topics about it. 

For the knock sensing its pretty simple, you can even use a mechanics stethoscope with a pipe bolted to the block, or an electric setup with a small headphone amp and a generic knock sensor. 
The factory sensor should probably work too but I haven't listened to it. 

This is what mine looks like with a generic headphone amp off amazon. 

 

Edited April 1, 2021 by stupid_fast

[stupid_fast]

A couple updates here.

On Rayapp2's 81 slicktop turbo, I was able to decode and map out the 1981 turbo ECUs, those definitions are now available. 

The big thing here is he swapped to 60lb injectors and I successfully recoded the stock ECU for correct fueling. 
Found the new K value and rescaled the TP load scales and its happy.
That car has further running issues that need to be solved, including the o2 swinging way more than my car does during closed loop, but the coding did its part.  
 

During this process I found a couple issues with what I was doing before, the rom chips I was using, ect. 
On my car I found the limits of fueling reliability on the stock AFM, which is about 200whp using virtual dyno to measure so probably inaccurate, but it should be within 10% of a real number.   

The boost on my car is back down to stock until I finalize a solution to make the fueling reliable.

Moates has gone out of business, so my ostrich emulator is now unsupported and all the documentation is gone which is annoying.
I was able to get Tunerpro working with emulation without offsetting the files, so everything gets a little easier there. 


Exactly how far can we go with this system?  I have an idea, but its a couple months away from being fully tested. 

 

 

Edited 5/11
With the new lower latency W27C512 45z roms and some cheaper open source rom adapters I've eliminated a lot of bugs I used to have. 

With my innovate unit logging MAP RPM & o2, I can use MegaLogViewer to show some meaningful data.

Actual O2 readings vs load, with a good Air Flow Meter I'm hitting close to the AFR table targets. 
Keep in mind MLV is displaying load as KPA from a map sensor, the load scale in the ECU is theoretical pulse width.   

Also here I'm battling boost drop with my intercooler and exhaust setup, so this is probably less than factory power output, but still demonstrates the efi working properly in these conditions. 

Edited May 11 by stupid_fast