nAst1: Progress and Concepts Thread

[Mars]

So a spark cut 2 step is in the works ?

I might just have to download all these files and try it.

Anyone out there using this code on a boosted V6 with 3 bar and some big injectors ??

[LZeppelin513]

I though I would post a tip that worked well for me.
This would really only apply to someone starting a tune from scratch and able to use both $A1 and nAst1. Start your tune with $A1. Because there is MUCH less resolution in the fuel and spark tables, its quite a bit easier to get your tables close, fast. Then when you are close, switch to nAst1 for a better code and do some fine tuning.

[robertisaar]

a slight update.....

so.... the 89-93 or so 3.3 liter that's based on the 3800? it happens to use an ECM that for all of the researching i've done on it is almost identical to a 1227730(literally, the same PCB, can't even see a different set of hardware like you would comparing a 7730 to a 7749).... it also happened to use a high-frequency MAF..... so i'll be stealing some code from that to get the timer/pulse accumulator to Hertz calculation done and use a modified version of the 94-95 LT1 algorithm to create the table itself and high-frequency MAF will very soon be ready to go.

obviously, with something as important as this can be to fueling/spark, it's going to get some significant bench-testing done before i consider releasing it publicly. but all of the option bits that already exist in the XDF regarding the MAF? expect all of those to be functional within the next release or two.

[robertisaar]

maybe it's just me, but i hate the idea of sending a bunch of raw fuel right out of the engine....

but it's simple to do, so, probably one of the next things in line, along with wastegate control to hit target boost, along with more launching stuff(like max PSI vs MPH)....

and yes, the code is setup for one MAP sensor, from 1-3 BAR. when using with a boosted engine, be certain to set the max RPM to allow baro update to something lower than your boost threshold, otherwise the baro will be updated to anything between the real barometric pressure and 104.45kPa. i may add dedicated barometric sensor support, but i don't know how much it would get utilized.

[caffeine]

Well IMHO after 3-bar support a spark-cut limiter just makes sense. Oh and when running a 3-bar a 1-bar is not needed, correct?

[robertisaar]

i get the feeling i need to make some kind of polling thread(s) for nAst1 users to see what's popular and what isn't....

with the spark limiter, it seems like it would be really simple to either make the dwell time REALLY short or just not have a dwell period at all. i discussed this with somebody playing with code59 for a little while, but i'm not sure how far he got along with it.

[caffeine]

I would definitely be interested in a spark cut limiter.

[robertisaar]

yes, the 3 step does a fuel cut, useful for a bunch of stuff, especially if you like to shift without letting off the throttle or want to be able to launch at full throttle, but not necessarily at a high RPM.

could change it to a spark cut..... if it were demanded enough. could tweak the code a bit so that it could be selectable as a fuel or spark cut.

[caffeine]

Hey so the way I understand it the 3-step rev limiter uses fuel cut; is this useful for building/maintaining boost at the line and during shifts? It seems like all the aftermarket 2-steps use spark cut. Also if running meth injection a fuel cut limiter could cause the engine to run super lean. Is there a way to change the rev limiter to a spark cut limiter?

[robertisaar]

that's a single P6 design though. everything is where it's actually supposed to be compared to a reference 68HC11, since the P6 units are actually 68HC11F1 models.

the SFI 3.8 are also single P6, or at least i've never ran across a dual one. oddly enough, the 94-95 LQ1(P4) and 94-95 3800(P6) share a LOT of code between the two....

[brian89gp]

16197427 ECM
Uses 64k EEPROM, address range from $4000-$FFFF. From the picture of the board it appears to be a single 6811 proc ECM, not dual like the N*, the SFI 3.8 motors, and a couple others. Seems to have extended RAM space as well.

http://www.gearhead-efi.com/Fuel-Injection/showthread.php?303-16197427-PCM-Information-OD

$0D-Hac.zip , partway down page.

And comments about it running a MPFI 3.4 Camaro engine with a DIS

http://www.thirdgen.org/techboard/diy-prom/556287-16197427-dis-offset.html

[robertisaar]

i'm also hoping it works as-is.... i didn't have to do any soldering on the PLCC stuff to connect the PROM's A15 circuit to the 6811's A15 circuit instead of the +5V that it was connected to.

i'm trying to find other instances of the P4 specific unit using 64KB BINs, but it's hard to find.... plenty of P6(and assumed P6 in the case of some cadillac 4.5/4.9 units), but no hard data on the P4s.

[brian89gp]

Spent a little too much time researching the hardware side of the P4 ECM today... Anyways, after reading about adding SRAM and NVSRAM modules it looks like you might need to have additional hardware in order to use any part of the other 32k address space. All the chips on the 16 bit bus look to have CS/CE (chip select/chip enable) pins and OE (output enable) pins or some other similar method to select a particular chip to read/write from, I'm not sure that simply adding the A15 wire will do anything as the 68HC11 probably has the EEPROM address space hard coded as far as CE/OE goes. Either way, the CE and OE need to be drawn low in order for the EEPROM chip to output anything onto the bus.

It should be possible to either use a 64k chip and manually (through hardware) map certain address ranges or use a second PROM/NVSRAM chip and map it to those addresses. The implementation of the custom SRAM mod to the '730 which turned into the 4k NVSRAM mod goes into this somewhat.

I really hope I am wrong and that GM was lazy and it somehow works, but if it doesn't there still appears to be other ways to get the additional space.

[robertisaar]

while extremely interesting(and surprisingly easy to impliment), i don't think i would want that to happen without my inspection and approval...... that's just asking for a bad O2 sensor to take out the engine. if some significant limits were put in place(can only adjust so far up or down), i could see it being useful and relatively safe.

[brian89gp]

More so it looks like the code itself can write to the main program space, eg the VE Learn feature. Turn of INT/BLM learning and instead have it directly modify (and save) to the VE tables directly.