nAst1: Progress and Concepts Thread

[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.

[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]

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]

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 :/

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.

[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.

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]

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.

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.

[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.

[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.

[pocket-rocket]

[robertisaar]

boost is always on the mind....

MAF's can read boost as well, just can't measure it obviously. i need to get that code tested as well....

also, anybody who's planning on running MAF and speed-density, does the concept of being able to skew the fueling towards one or the other sound interesting?

currently, if the MAF option is set, it will blend the two BPW calculations together with no bias(meaning real BPW will be the average of the two), however, i may be able to setup a scalar to adjust one way or the other, depending on which you like more.

[19Cutlass94]

So now the possibility of boosting the car comes to mind... Damn you Robert!

[robertisaar]

3BAR code is finished, or at least the first version of it is. when i determine if the 9396 can run a 64KB BIN after some mods, then V2 of the boost code will be patched in, making 4 17X17 VE and main spark tables each(2 for boost, 2 for non-boost). there will be 400-2000 in 100 RPM increments, then 2000-8400 in 400RPM increments. MAP will be in 5kPa increments up to 100kPa. after 100, a 12.5 kPa increment will be present.

tl;dr version:

http://i.imgur.com/TI8uT.png

essentially, in non-boosted applications, you'll drop down to 2 spark and 2 VE tables, while boosted will have 4 of each.



but, that's the furure, assuming i can open up some more space by jumping to a 64KB PROM. as-is, there's a boost BPW multiplier table (quite similar to 8F), and a boost spark retard table (my own design). the new version will still have the BPW mult table(in fact, it's a requirement due to all other things being equal, more pressure = more air), but it won't be changed much, since VE will be the primary way of changing fueling. the spark retard table will obviously no longer be necessary at that point and it will be removed from the XDF and it will clear up a few bytes for me to use elsewhere.



anyways, to run boost, a 9396 is required(or mod a 7730), since some of the variables are stored in the SRAM, but no internal mods are needed...

speaking of internal mods, you can open up at least 3 more A/D channels that way just by moving a couple of resistors around on the board.



code will be tested as soon as i have the bench completely built(like ~90% there right now), afterwards, a real-world test with a turbo LQ1/284 is NOT far behind.