I switched over to using sync accel enrich rather then async (as per RBobs suggestion) and I found that the engine didnt need anywhre near as much AE as I would have thought. With all the wacky conversion factors floating around I was under the impression that the injectors where going close static during AE at times when I saw the times in the tables. Not the case. Theres almost no AE needed at all. Whats more so, the engine is very sensitive to the ammount of AE that it does have. Little too much or little and it either goes lean and pops or goes rich and bogs out. From the looks of it, my 60 (61, 65, whatever...) pph injectors can easily flood out the motor during AE.

With only a few percent duty cycle added to the sync PW at the most, I can now see why async just didnt cut it. The AE pulses are very short and can just get totally masked out by the sync pulses whenever two overlap, depriving the engine of its AE for that go around. I thought only parts of the AE pulses would be masked since the conversion factors floating around are like 61 usecs/bit rather then the actual 15.23 usecs/bit.

Heres the AE I do have. Its not very much and Im thinking of jsut going to a max of 12.5 or 6.25% DC to improve the resolution of the tables.

 

What code are you running?

 

It origionally was the $4D tbi code but most of the stock stuff is gone. I replaced it with things like cool. fan control, sync AE, MAF based fueling alg. based on the code used in the $32/$6E MAF ecms, 16 bit table look-ups, couple of 24 and 32 bit routines for the MAF, and much more. So, you might say that its *slightly* modified from its origional form

RBobs ultimate tbi code uses the sync AE as well as lots of other features. If/when the speed reader comes out, you might want to give it a try.

 

ugggggh.......reason number 505050483948348390 that I can't wait till the speed reader comes out. I need to dig up some old post on how to go romless and see if I can con Rbob out of his ultimate code early.

I recently disabled asynch at idle, and part throttle and couldn't believe how much more control I had over fueling. It did seem like the least little change would throw everything for loops. I can now run open loop with no problems, but my AE is giving me fits. It's close now, but I stll have a lean spike. Not enough to cause big problems, but it's anoying.

Edit: It just hit me, I remembered seeing a wacky PW reading from time to time while datalogging. I went back and checked and sure enough it was during a throttle stab. The pw would jump to any where from 8 to 12 ms and then go back to normal. Of course with the slow data rate I couldn't see the whole picture. It would only show up every now and then. This is probably why I can't quite get rid of my lean spike.

 

can you define synch vs asynch fueling for us 'puter illiterates/nitwits. let me guess? is it the injectors pulsing togeter as same time or at seperate times(TBI/2 injectors)?

 

In short, the injectors fire in sync with the DRP's ( Dist ref pulse)
Every other drp in some cases.
Async, is the time between DRP's.
Sync has priority so it can cut off the async pw's.
TBI is a little different, I believe it fires the injectors side to side also. And different bcc's can be different also.

 

Synch means in synch with the Distributor Reference Pulses.

Asynch means they go to a time based system, where they fire every 12.5 msec.

When the two are in use, the Async can get *covered up* by the Synch. Just driving down the road your in Synch mode. AE, adds the Asynch pulses, to the Synch pulses that are already in use.

 

Pretty much the async PW's are put out regardless of whats happening with the sync firings. The async pulses are at 80 Hz with both injectors firing together. This is also the same rate at which the fuel loop runs in the ecm. At the end of the AE routine, the computer dumps the extra pulsewidth in temperary storage where it is outputted to the injector drivers. If the injectors are already open, oh well.

With sync firings, the engine does accelerate more smoothly and evenly. Another nice thing is that the AE will now show up in the datalogged sync pulsewidth which will probably make tuning it easier.

 

This is the same that I found. Rolling into the throttle is so much smoother. I was actually quite surprised. And throttle response, killer. Good work.

As Dimented noted having the AE as sync PW allows one to know if the injectors are large enough. Mixing async and sync together and trying to figure out if the injectors are static doesn't work too well.

It's amazing that a quick pedal jab at mid RPM can run 80#'ers at 22 PSI static, and just maintain a decent AFR.

RBob.

 

RBob,

Is this why I have seen the AFR for WOT increase from 12.4 to 12.8-13? I recently made the change to eliminate ASYNCfor fueling, as per your instructions. I have not yet made the change for Async to Sync for AE. I am running a bit higher FP than before with a higher 533usec Injector Bias rather than a 396umec bias. These last 2 changes should have produced a richer mixture at WOT, but it hasn't. Inadvertently leaning the WOT mixture has proven to be a benefit as evidenced by higher MAP readings into the 54-5600rpm range.

 

how does someone change from using async pulses to sync'ed pulses? Was this info posted in another thread? Very interesting stuff, and really makes sense compared to how it runs stock.

 

An engine that is producing more power will result in a lower MAP reading. Eliminating the async for normal fueling won't affect WOT AFR. You are correct in stating the higher bias and FP should have made the AFR richer. There could be other reasons, one as mentioned is that you are seeing a higher MAP value. May need to increase the VE at that point in the table. Fuel pressure/delivery could be dropping off at WOT. Any number of things.

RBob.

 

There are two different async fueling modes being discussed in this thread. Async for AE (dimented24x7), and async for normal fueling (Dominic).

To change the async AE to sync AE code changes are required. This would mean a patch of some nature for those running a stock '747 or '8746. This has not been covered. With source code and ROMLess(tm) it is much easier to convert to sync mode AE.

The other async mode is when the normal fueling PW gets small the ECM switches from sync to async mode. I discussed this several years ago. The switch over causes major AFR changes and roughness. This is seen on trailing throttle, low speed traffic crawl and sometimes at idle (talking big injector flow rates here). To eliminate this mode set two calibration terms to the value of zero (0). They are the upper and lower hysterisis points for the sync2async and async2sync cutovers.

RBob.

 

RBob,

Sounds very reasonable. Where I was seeing 95kPA, I am now seeing 99 to 100kPA