nAst1: Progress and Concepts Thread

[pocket-rocket]

[robertisaar]

found out something else interesting as well....

there is a pin that allows you to use a different type of knock sensor/knock sensing setup... from what i can tell, it's for the type of sensor that uses an external module as a filter. supposedly, those units were better at filtering out false knock due to being a 4 pole design, compared to the 2 pole design of the ones used in the MEMCALs we deal with...



now, you could go really out there and make some incredibly out there design that never picks up false knock, will always pick up real knock, etc, etc.... but most of the time, you have no way of interfacing with the ECM to tell it that knock is happening. BUT from the schematics, it seems that when you ground the circuit, it will instantly cause (well, within a few cycles, but at 2.1MHz, it's essentially instant) a knock count to be registered and the ECM will start accounting for it... so, make uber-advanced knock sensing system, have it ground some output of it's own whenever knock has been determined, bam, works with our ancient computers.

[Superdave]

That's the same external setup that you need for the Holley Commander. I have a brand new harness that's already got the plug installed for the interface.


Still having my reservations about installing the 950, the whole setup is great except for the tuning software.

[Joseph Upson]

found out something else interesting as well....
there is a pin that allows you to use a different type of knock sensor/knock sensing setup... from what i can tell, it's for the type of sensor that uses an external module as a filter. supposedly, those units were better at filtering out false knock due to being a 4 pole design, compared to the 2 pole design of the ones used in the MEMCALs we deal with...

now, you could go really out there and make some incredibly out there design that never picks up false knock, will always pick up real knock, etc, etc.... but most of the time, you have no way of interfacing with the ECM to tell it that knock is happening. BUT from the schematics, it seems that when you ground the circuit, it will instantly cause (well, within a few cycles, but at 2.1MHz, it's essentially instant) a knock count to be registered and the ECM will start accounting for it... so, make uber-advanced knock sensing system, have it ground some output of it's own whenever knock has been determined, bam, works with our ancient computers.

Have you considered adding a spark table to adjust timing based on air temperature in boost, or did I miss that?
I know the VVT control is important to you, but have you investigated its overall value in a cam in block application?

I've run the 3900 with the cam fully advanced and now with the cam degreed in. The degreed camshaft has revealed just how quick the motor dropped off with the fully advanced camshaft.
Although I haven't noticed a significantly different launch intensity, (haven't gone all out since I've already crunched one F40) I have noticed a significantly different top end improvement. Perhaps the performance gain with VVT is not worth the effort since it can't produce the dynamic that separate intake and exhaust VVT motors can.

[robertisaar]

Have you considered adding a spark table to adjust timing based on air temperature in boost, or did I miss that?
I know the VVT control is important to you, but have you investigated its overall value in a cam in block application?

I've run the 3900 with the cam fully advanced and now with the cam degreed in. The degreed camshaft has revealed just how quick the motor dropped off with the fully advanced camshaft.
Although I haven't noticed a significantly different launch intensity, (haven't gone all out since I've already crunched one F40) I have noticed a significantly different top end improvement. Perhaps the performance gain with VVT is not worth the effort since it can't produce the dynamic that separate intake and exhaust VVT motors can.

spark mods based on IAT (or calculated airmass temp due to heating while passing through the TB/UIM/LIM/Head) were the second thing i completed, right after the expanded VE and main spark table. it's not a simple "subtract this much spark at this temp" table though, i have it actually setup as a multiplier table, that way the amount of spard added/subtracted is proportional to the amount of spark that would have been commanded to begin with. seems like a better option to me.

and the VVT: now try a run that has the ECM control the cam at all RPMs. in theory, it should be able to boost power at all RPMs by starting with a full advance to help low RPM, then start retarding as RPMs rise to boost power in that range.

i guess the easiest way would be to get into a vehicle with native 3500/3900 and if software can control it, log a run with the cam fully advanced, a run with the cam fully retarded, then a run with the PCM controlling it. that would show it's benefits, if they do exist.

[Joseph Upson]

spark mods based on IAT (or calculated airmass temp due to heating while passing through the TB/UIM/LIM/Head) were the second thing i completed, right after the expanded VE and main spark table. it's not a simple "subtract this much spark at this temp" table though, i have it actually setup as a multiplier table, that way the amount of spard added/subtracted is proportional to the amount of spark that would have been commanded to begin with. seems like a better option to me.

and the VVT: now try a run that has the ECM control the cam at all RPMs. in theory, it should be able to boost power at all RPMs by starting with a full advance to help low RPM, then start retarding as RPMs rise to boost power in that range.

i guess the easiest way would be to get into a vehicle with native 3500/3900 and if software can control it, log a run with the cam fully advanced, a run with the cam fully retarded, then a run with the PCM controlling it. that would show it's benefits, if they do exist.

Here is a link to a thread involving a VVT test that points out what I'm getting at, you can expect smaller results on the much smaller 3900 relative to their results with that rat motor.

http://www.hotrod.com/techarticles/engine/hrdp_1007_gms_variable_valve_timing_system_performance_test/

When a turbo is involved, you can optimize low end performance with your cam choice and use boost to do the rest, by programming the boost control table to add a little more boost pressure in the upper rpm range to make the power curve more linear at the point where power would normally be about to drop off. You will not miss 5-8 hp and torque from VVT control if you've already exceeded the 300 + mark.

[robertisaar]

not everyone will be running boost though, so those people won't be able to make up for lost torque by increasing pressure. in fact, i would assume most people would run N/A, or at least N/A for a while, compared to running forced induction.

[Joseph Upson]

not everyone will be running boost though, so those people won't be able to make up for lost torque by increasing pressure. in fact, i would assume most people would run N/A, or at least N/A for a while, compared to running forced induction.

The problem with running it naturally aspirated is that you'd still be limited to the stock power level unless you had the camshaft reground because if Desktop Dyno is any indication, the lobe design and LSA are unique to VVT and any cam changes would likely have to be dynoed to reveal the advance and retard limits for best performance, otherwise retarding it just a little will result in an immediate drop in power which I observed in Desktop Dyno when I retarded my reground cam specs with a tighter LSA as well as in real time when I retarded the cam using the VVT module during tests with the Gtech accelerometer.

There was about a 65 hp difference between full advance and full retard under 7 psi of boost so there is more range than is useful for power.

[pocket-rocket]

Well, Robert, I got my Ostrich yesterday. Give me a couple weeks and I'll be able to be your DOHC guinea pig.

Sadly, I still need to learn tuning :/

[robertisaar]

real-life guinea pig.... neat.

i actually just picked up what should be the last piece of my solid-state 9396 testbench V1.0 this morning.

so that will be nice to have finished and not need to risk an engine with new code.

i also managed to find a source of 7727/9396 style PCM terminals.... http://happautomotive.com/ they don't have them listed, but they sold me the circular wire weatherseals and terminals for $.20 each with $4 shipping. so $20 for 40 of each... not bad. i also figured out how to modify the existing PCM connectors so that the blocked cavities can be used.

[pocket-rocket]

Good deal. I was hoping to pick up a wideband in the near future and was hoping to be able to pipe it into the ECM for at least logging purposes. Is nAst1 going to use wideband input for anything other than logs?

[robertisaar]

Good deal. I was hoping to pick up a wideband in the near future and was hoping to be able to pipe it into the ECM for at least logging purposes. Is nAst1 going to use wideband input for anything other than logs?

for the moment, WB can be patched in for logging purposes only...

in the near future (and by near, i mean when i confirm that all of the 3BAR stuff is working 100%), i will have options setup to allow the wideband to be used for closed loop fueling control as well.

knowing me, i'll have another option that will allow the WB to adjust AFR in PE as well, if the read AFR isn't matching the commanded AFR.

and probably yet another option to use the F56 (open loop target AFR vs MAP vs coolant) table as a WB closed loop target AFR table. it already goes from 20-100kPa and -40 to 241*F, so i'd say it doesn't really need expanding. maybe a RPM/TPS modifier so that in situations where MAP would be similar(800RPM and 40kPa idle compared to ~1600RPM and 40kPa while coasting down from speed), a different AFR could be commanded for each situation...



oh, the possibilities.

[caffeine]

Don't know if this is where I should post this but I'm currently running a 3500 swap in a 4 speed manual Fiero on nAst1, and I'm just having a few issues. First, how do I tune the idle table? I seem to be running rich no matter how much I decrease the values in the idle table but when I'm logging the BLM is constantly at 128 but the INT stays around 95-105. Another thing I can't seem to figure out is lean cruising. When I'm cruising on the highway it still always says 14.7:1 is the target AFR. Not sure if it matters but at highway speed I'm revving at between 2400 and 2600 rpm. I have the lean cruise set to be enabled around 80 km/h at IIRC 15.6:1. Oh and one more thing. When in DFCO, I can seem to feel it when the computer switches tables; like it leaves DFCO for a second and re-enters it as it moves from the 5200 table to below (and also when it moves from the 2000>5200 to < 2000).

[robertisaar]

for idle, make sure that the idle VE table is enabled, by default i have it disabled in all factory BINs, but one flag change and it will be used when in the conditions that are adjustable for you to consider "idle".

BLM at 128 is either the BLM being purposely locked to 128 in the tune or you haven't gotten warm enough to allow the BLM to start moving.

lean cruise REQUIRES highway spark to be active, so if you've zero'd out that table or don't allow it to be activated, lean cruise is disabled as well. initially highway spark was called "cat overtemp spark" since that's what GM referred to it as, but sometimes they mislead like that. also, you would obviously need an accurate VSS signal as well and be above the MPH thresholds. and since you're a manual, make sure the requirement for TCC lock is disabled for highway spark.

when switching between tables, no fuel or spark changes beyond the normal main spark and VE calc are effected. when in DFCO, VE and spark changes will not be felt, since the engine is not in any way producing power.

also, be sure you are indeed running off the newest base BINs, since there were a few bugs i fixed that it seems you might be encountering.

[caffeine]

for idle, make sure that the idle VE table is enabled, by default i have it disabled in all factory BINs, but one flag change and it will be used when in the conditions that are adjustable for you to consider "idle".

BLM at 128 is either the BLM being purposely locked to 128 in the tune or you haven't gotten warm enough to allow the BLM to start moving.

Ok I didn't know that the idle VE needed to be enabled. It actually idles fine since I disabled single-fire altogether; with single-fire enabled it would randomly stall while idling. BLM always is at 128 when idling regardless of whether closed-loop is enabled or not. It is in cell 0 also if this matters. I don't know how it would be locked to 128 allways in the tune as to my knowlege I haven't changed anything that would cause that.

lean cruise REQUIRES highway spark to be active, so if you've zero'd out that table or don't allow it to be activated, lean cruise is disabled as well. initially highway spark was called "cat overtemp spark" since that's what GM referred to it as, but sometimes they mislead like that. also, you would obviously need an accurate VSS signal as well and be above the MPH thresholds. and since you're a manual, make sure the requirement for TCC lock is disabled for highway spark.

Ok I had no idea about highway spark tables, I simply enabled the lean cruising flag and adjusted the scalars for speed. Where will I find the requirement for TCC lock?

when switching between tables, no fuel or spark changes beyond the normal main spark and VE calc are effected. when in DFCO, VE and spark changes will not be felt, since the engine is not in any way producing power.

also, be sure you are indeed running off the newest base BINs, since there were a few bugs i fixed that it seems you might be encountering.

Ok I just thought it was weird that while decelerating it will stop revving down for a half a second or so before continuing on. I thought that switching tables would be the most logical explanation but I must be wrong. It's also difficult to tell exactly what RPMs it happens at since my tach is way off in my dash (was with the stock engine as well).

Oh and I'm running version 1.05. Is that the latest version?

Thanks for your hard work producing this code BTW. Tuning has so far been going quite well I think.