nAst1: Progress and Concepts Thread

[neophile_17]

If you don't find an easier solution you could convert a square wave to a sine with a Low Pass Filter. I'd try setting it up to cut out frequencies 25% higher than you're max frequency (top speed *PPM / 60min. /60sec.=Hz). Not an expert but I guess I was awake in signals class that day... HTH

~sam

[robertisaar]

^ that may be useful for some of my home projects as well.... much appreciated.

another thought: adaptive spark control

in OBD2 GM V6 applications, every time the PCM sees a knock event, it retard timing temporarily and filters it back in like what we have. however, their's doesn't return to 100% spark very quickly, instead it gets biased towards a "bad fuel" table and eventually gets filtered back towards their main table after so long without knock events.

i would like to impliment something similar if anyone is interested in it... the idea would be that after so many seconds of runtime(to elimnate starter induced or unpumped valvetrain induced knock counts), every time a knock count occurs, the ECM will decide to permanately(until a key-off event or a stall) retard maximum spark advance based on how many knock counts have occured, each count(or maybe multiple knocks must happen? i'll have to decide about allowing a different threshold there) will cause just a LITTLE bit more retard, until knock quits happening, and at that point the ECM WILL NOT add spark back in just to have knock occur and filter in and out again....


sound interesting?

[Superdave]

sounds like a problem waiting to happen.. lol


Autozone has my correct VSS for $50, going to pick it up this weekend and just wire it in to the stock magnetic inputs. the PPM will be fun to figure out though.

[robertisaar]

sounds like a problem waiting to happen.. lol


Autozone has my correct VSS for $50, going to pick it up this weekend and just wire it in to the stock magnetic inputs. the PPM will be fun to figure out though.

problem, as in, whole bunch of false knock making spark advance run down to 0*? i could setup an adjustable limit as to how far spark can be "permanately" retarded.

also: random and unrelated fact of the day: the 94-95 3100/3.4RWD code stores/updates up to 64 BLM cells.

[robertisaar]

who lives near sea level elevation and has a 3BAR MAP laying around?

getting around to dealing with boost code, need to know the A/D result of 1 atmosphere to setup the boost BPW multiplier and boost spark retard tables.

EDIT: and just for fun, here's an overview of the process i use to write code for something like this:



just before BPW is stored to injector register, jump to new code.

new code checks for option bit of using 3BAR MAP. if using, continue, if not, return and store BPW.

test to see if 1BAR MAP is maxing out, if so, do A/D read and continue, if not, return and store BPW.

when A/D read finishes, take result and do 2D lookup of multiplier table for boost BPW.

take 2D lookup result, multiply 8 X 16(should be enough resolution?) value, then return to normal code and store BPW to register.



i'm not going to post the assembly code due to it likely confusing the hell out of anyone who isn't themselves capable of all of the code mods i've done thus far already.

[pocket-rocket]

i'm not going to post the assembly code due to it likely confusing the hell out of anyone who isn't themselves capable of all of the code mods i've done thus far already.

You are already beyond that with me, I still haven't even learned tuning yet...

(I still look in on this thread though )

[pocket-rocket]

EDIT: as a quick(LOLOL) project, are there any non A1 calibrations that anyone would like to see ported to the nAst1 code? i'm thinking of the latest 91-93 3.4 calibrations would be a good bet....!

I looked through a few updates on here and haven't found one with any 3.4 ports in them so far. I've got the 92 in the garage right now and plan on starting to tinker with it in the coming weeks. Has the 2 step been integrated in nAst1 yet?

[robertisaar]

i'm actually working on the BCFA port now, started on it in may, forgot about it until now. after that, BHAK.

no 2-step yet, i'd like to have a bench running for that since it's fuel cut related and would be much safer to test on a virtual engine rather than a real one.

[pocket-rocket]

I assume it's not as easy as making 2 tables for rev limit and have which table is used selected by the switch being on or off?

[robertisaar]

ehh, somewhat...


basic overview:

checking if 2-step option is selected
checking max MPH to allow 2-step limit(wouldn't want a fuel cut happening during a shift )
checking the clutch/brake switch status
checking the override switch status(burnouts)
then determining the rev limiter to check against

if need to limit, go do the code that cuts BPW to 0
if not, continue on as normal.

[pocket-rocket]

checking max MPH to allow 2-step limit(wouldn't want a fuel cut happening during a shift )

What about using it for WOT shifting? WOT shifting ability is an awesome option for boosted cars (keeps the turbo spooled into the next shift). What's the mechanical risk in fuel cut in a shift besides slight residual fuel in the runner causing an extreme lean condition, but not lean in the sense where it does damage from the lack of enough fuel to get an actual "bang"? I'm not trying to give you a hard time here, just trying to understand things better.

[robertisaar]

"no lift shift" ?

i would think you could use the normal rev limiter for that since it would still be in effect whenever the 2-step limiter isn't being used.

[pocket-rocket]

"no lift shift" ?

i would think you could use the normal rev limiter for that since it would still be in effect whenever the 2-step limiter isn't being used.

Well, yes and no. If I'm burning down the strip using a "no lift shift" I don't exactly like the thought of my engine free reving to 7,200 rpms while I shift. ~3500-4000 seems like a safer bet to me, and brings me right back into gear at the bottom of my power band, not to mention would be easier on synchros.

[robertisaar]

hmm..... so while WOT(or near it at least), whenever you have the clutch pushed in(and for sake of the 2-step, above a certain MPH), you would want another rev limit?

i see what you mean now.... definitely something i'll have to integrate at the same time as the 2-step.

getting all kinds of track goodies added lately.

[pocket-rocket]

getting all kinds of track goodies added lately.

And versatility All of this stuff should certainly make this an attractive mask to use by all sorts of people. I mean, if it's going to be a project for something other than stock cars, it may as well get features that non-stock cars would like to have I guess I didn't know (by definition) that a 2 step and WOT shift limiters were not the same.