Synch vs Asynch fueling

[EagleMark]

That is very informative. I'd like to see a V8 TBI if you have one? Most are Sync at idle and off idle untill Async is needed or AE I believe? And Async is also used in DFCO...

[chevmasta]

As a Lurker reading this thread.

I just wanted to comment (I believe as truth) that my 7060 $85 is synch at idle and Asynch for AE (as my logs appear to show)

[POZE]

This is 1990 ASDZ Bin. First is idle. Second is power braking.
Red = Reference
Blue = EST
Green = Injector
Yellow = Injector

[EagleMark]

Nice! Looks like Sync at idle and Async during power brake? I wonder if the power brake cause AE or some Async condition? When I datalog the AE or Asycn flag hardly ever comes on, only WOT high load. Not off idle...

[POZE]

It would be interesting to see what happens when the AE and Async flag comes on. The vehicle I tested with is not road wothy or I would do the WOT road test. I have seen Inj pulse added between the DRP on S-10. Now I wonder if there are three modes of injection. Every other DRP, every DRP, and every DRP +one in between during AE - Async? When weather gets better I will check my 94 GMC on the highway. It's amazing how one question and answer leads to another question. I guess that is why we like this stuff.

[EagleMark]

I thought the AE was added to a pulsewidth? Those scope graphs clearly show Sync idle and Async off idle, right? What I was saying is now no Async flag shows up all all except VERY high load, way beyond when AE would have been enabled. There is no AE flag in $42

I'll have to compare ASDZ which is CA version of ASDU Fed version for any changes.

[Six_Shooter]

AE is added between injectors referenced to DRP. I've seen this on the '7730 for sure, possibly the '7747 as well.

POZE what are you using for a scope to get 4 traces?

[RobertISaar]

i'm certain some code adds in into the sync pulsewidth, but i forget where i saw it...

it only fires it async if it passes a certain PW threshold, otherwise added to sync PW.

[POZE]

I am starting to wonder if Async as I have seen it described by GM training manuals is some what generic. What I have seen at this point, leads me to believe Async can be different things on different engines. Or maybe Async isn't allways the correct terminology for injector to DRP corolation changes. I have seen four cylinder TBI skip an injector pulse between DRP and go to Sync above idle or under load. Other four cylinder TBIs have idled at Sync and added an extra pulse between DRP during load. As the opportunities arise I will collect more patterns from other engines and post.
Is AE a combination of PW and more injection pulses? The scope is a Pico four channel. This scope has a trigger function that is used to correct screen jitter so the patterns are easy to evaluate. It can freeze patterns and enlarge them. It also contains a small buffer to save a string of patterns. When examining injector patterns this scope picks up pintel bump during the closing of the injector caused by the metal rod moving in the magnetic field.

[EagleMark]

I don't think theres more then 2 Sync and Async, unless you include the transition? What's confusing me is your scope readings changing?

Here's some notes I been keeping in my $42 XDF when I started trying to figure it out.

TPS The delta TPS% values used to look up the TPS AE contribution table
TPS AE The amount of AE fuel from the TPS AE table (in mSec)

MAP The delta MAP value (KPa) used to look up the MAP AE contribution

MAP AE The amount of AE fuel from the MAP AE table (in mSec)

AE PW Final AE fuel that is added to the Sync PW in Sync, or added to Async if Async fueling is in effect.

INJ - Async Transition Lo
If the Sync PW is less then this value then async mode will be entered.

INJ - Async Transition Hi
If the Sync PW is greater then this value then Async mode will be exited (if in Async mode).
If Async Transition Hi/Lo are set to 0 it will disable Async fueling.

Looks that was in ASM/hack. Then another huge elaborate section if it were Async.

Here's a look at Sync to Async settings in $42 bin. Notice Sync can change to Async, but Async is just Async... I thync...

[POZE]

What part of the scope change is in question?

[EagleMark]

It's not in question, it's changing the injector firings for alternating to simultaneous.

[EagleMark]

I did a power brake today on ASDU and no Async flag. So those extra firings are AE?

[POZE]

I will try ASDU Bin to see how it reacts. Was looking at the injector pattern in micro seconds. PW changes stand out at this time base. I am hijacking with scope stuff. Maybe a thread on scope patterns.

[EagleMark]

This is a great thread for Sync Async scope patters...

I compared ASDU and ASDZ, there's nothing that would change. It's all EGR, a little spark, some O2 changes, I'm guessing all to tweak a little less emmissions for the communist republic of California.