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


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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 by Gollum
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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.

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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 by stupid_fast
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  • 1 year later...
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 by dogmeatk
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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 by stupid_fast
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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 :P 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?

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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 by stupid_fast
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