Timing issue from open to Close loop?

[93LT1]

Hi Guys First off Happy Holidays If you don't mind, I can use some help. I have a 396 LT1 Vette. Stock injectors, O2 sensors and ignition. The chip I have was programend for a 350 with top end work and not a 396. I've noticed every time I quickly accelerate from a sustained speed of oh say 42-45 mph I get a nasty pinging sound, then the tranny kicks down a gear and the motor rev's normal. But the pinging is really nasty and occurs every time I accelerate from a roll. But all is fine when accelerating from a stand still all the way up the rpm band. I’m concerned the pinging will ruin the engine. I have the Diacom Plus system. My plans are to monitor a few runs. But what should I be monitoring? If memory serves me right, I'm only able to monitor three long term elements at a time. I was thinking perhaps a set of MAP/timing/rpm elements and review the BLM/integrator values. I'm speculating there's a timing issue. More so when transitioning from open to close loop (WOT). Any thoughts? As always thank you Hank

[DOCTOR J]

If your chip has not been re-done for the correct displacement, you are probably running lean/too
much part-throttle timing. That is a really bad combination for long-term engine health.


1. Diacom records ALL the ALDL parameters in real time. It will only GRAPH a total of 3 variables
at once.

2. The trick answer to the Diacom display problem is to download the DataMaster s/w for your car.
DataMaster will play-back Diacom files, and has a much better GUI - it will graph 4 variables at once,
has a zoom feature, and generally is much more user-firendly for data display. As long as you are just
using it to display Diacom files, it need not be registered.

3. The alternate is to export the Diacom data in a DB format, and use Excel or something else to graph
the required data fields.


You would want to see RPM, MAP, Spark Advance, and Knock counts to get a handle on the timing
issue; RPM, MAP, TPS and BLM to resolve the fueling (VE) problems.


If it were mine, I wouldn't be driving the car much until the ECM program was sorted out - and I
absolutely would NOT be doing WOT pulls in traffic, unless I planned another engine re-build soon.

YMMV, HTH, etc.

[93LT1]

Hi DoctorJ
Thank you for your recommendations. I just logged a few partial throttle runs and viewed it via Datamaster. Datamaster looks like a great program.
Your right. I'm running on the lean side during Open-loop. Doesn't seem citical since the BLM did peak @ 140-150.
I should be ok at WOT. I took the car for a dyno last year and made proper adjusments to the AFR during some runs while monitoring it with there Wideband O2 sensor.

I know I need to make changes to the chip. I'm planning on diving in with the help of the forum.
Should I invest in wideband O2 sensors? If so which one is recommended?

Also is anyone selling chip burners?

Thanks
Hank

[DOCTOR J]

Originally Posted by 93LT1

I'm running on the lean side during Open-loop. Doesn't seem citical since the BLM did peak @ 140-150.
I should be ok at WOT. I took the car for a dyno last year and made proper adjusments to the AFR during some runs while monitoring it with there Wideband O2 sensor.

I know I need to make changes to the chip. I'm planning on diving in with the help of the forum.
Should I invest in wideband O2 sensors? If so which one is recommended?

Also is anyone selling chip burners?

1. Adjusting the fuel pressure does NOT take into account changes in atmospheric conditions.
A fuel rate that was adequate in the summer can be 5-10% lean in winter air if the ECM was not
properly programmed.

2. Good luck to you with your tuning. While waiting for answers from the Forum, you might note
that the GM ECM's are now more than 20 years old. There exists a considerable body of information
that has already been compiled. References to it can be found in the "FAQ" section above.

That would include references to editing s/w, PROM programmers, and such.

3. With respect to WB units, I prefer to build my own (info on my web pages). I have also seen the
output of a Zeitronix commercial unit. While it lacks the bandwidth that I like, it seemed to do an
acceptable job.

http://www.zeitronix.com/

Also, Bowling & Grippo are planning a new reference unit - though I haven't seen the parts kit offered
yet:

http://www.megasquirt2.com/PWC/