OK, so I know what sync means, but what does async mean? This is on an Edelbrock MPFI conversion and originally programed by Howell. It looks like it is set up to run async all the time. This is on a 502HT with 16197427 ECM. I've developed a misfire, but I think my injectors are undersized. At WOT I've seen as high as 5.89 on the PW, running out to 4K rpm. the engine is supposed to be rated at 375 hp with stock exhaust, but with the addition of headers and a few other external breathing improvements, it probably exceeds 400 HP.

These are "pico" injectors. I'm not sure what that means other than it doesn't require modding the ECM to convert from TBI to MPFI. If I do upsize the injectors, where do you get "pico" injectors? Are they as reliable as regular injectors?

 

Async mode is when the injectors are fired 80 times a second (every 12.5 msec). And is asynchronous to the spark plug firing. Was probably done to get some duty cycle out of the injectors. Also note that running a MPFI set up in async mode will have it running like crap.

Pico injectors are lower mass so they open & close more quickly then other injectors. They also have a high enough resistance to not trip the PnH drivers in the PCM.

Is there an 'E' auto in the vehicle?

RBob.

 

So that explains a few things - like why my mileage calculations were erroneous.

"run like crap" - Does this explain why the engine needs a ton of advance below 3K RPM? When first installed, it seemed to run OK. An occasional misfire at idle, but otherwise gave no indication of any issues. I started dinking with the timing and discovered it likes a few extra degrees in the low end. Throttle responce was weak until around 2500 RPM. Slower speeds never improved mileage. Are those the things " run like crap" means? Or should it mean even worse?

To run sync, I assume I need a crank position sensor, is that true or does it sync off the dist? By "E" auto, I assume you mean like 4L80E. Not yet but there is future plans for one.

 

Plans for a 4L80E, explains the use of a PCM. I was going to make another suggestion, but it won't run an E tranny. Even have an HT502 calibration for it. But you would have to retain the '7427 to run the tranny.

The '7427 ECM will run sync mode via the distributor reference pulse. Now sure what was done to run async always, but it would be worth undoing it and trying it out. Usually it is done by changing the minimum injector PW calibration values. Setting them high will force async mode.

Setting them to nominal values (say 0.512 msec), will only have async coming into affect at small PW's.

The problems you are having with that engine could easily be from running async all of the time. I've done some testing with async only on TBI and it ran terrible. I've done testing on MPFI set ups with the wrong injector firing rate (6-cylinder rate on an 8 cylinder and vice-versa). Runs like crap.

Although running the TBI firing rate on the 6-cylinder MPFI was OK. It still ran funny. Running the proper MPFI rate on the 6 cylinder runs much better. I can't imagine what it would be like running async all of the time.

IIRC, if using $0D there is a way to force the proper MPFI firing rate. There is a thread here on TGO about doing it.

RBob.

 

Hmm, I just compared to the BJKW.bin, and it only runs in async mode. The BJKW bin is for heavy truck 454 w/4L80E. This $0E.

I have no idea why the OEM bin runs in Async only. Maybe this is the way a 7427 runs all V8s. I would like to see some other $0E bins to see if they are all that way.

 

I have found that MANY 2.8/3.1/4.3 and 454 calibrations run ENTIRELY in ASYNC.

 

My 90 SS with 454-TH400 and 8747 ran all asynch. My 92 SS with 454/4L80E and 16147060 also runs asynch.