I got a custom mail order chip for my 87 blazer. Did not take me long to realize I should not have even wasted my time with getting a custom mail order tune. I started dwelling into learning how to read and write new eproms in the last year or so. I feel I have a basic understanding of what I am looking on between datalogs and the current mail order chip I have in the truck currently. A big red flag for me about the mail order chip was that I was told to first set my initial timing at 8 degrees advanced. Got the chip, put it in, then I was told to set my initial at 18 degrees advanced. To be fair, it did give me good vacumn and the engine definitely liked a more initial advance on the timing. Well now that I have been able to review the bin file on the mail order chip, I see that my initial timing in the chip was never changed to 18 degrees advanced after recieving a different modified chip according to datalogs I sent in. Since that was never inputted into the bin file, my total timing was going up to around 46 degrees advanced at 3600 rpms or so, also checked this with timing light on the truck. Also seem to be getting a good bit of knock counts while I drive and reviewing the datalog I see alot of knock retard going on. Could someone confirm I am reading this right? Maybe some tips for a beginner trying to tune? I have reviewed alot of tuning links from this forum but it is an awful lot to take in and I feel I need to actually start writing my own tunes in order to understand more.

I like to think I have a good basis of understanding for tuning and I believe I need to do my own tuning to this truck. I have the 7747 ecm in the truck which is if I understand right, the mask id is $42.

 

The BIN was removed as we don't discuss mail order or aftermarket tunes here. Thread is approved.

Best bet is to start with a fresh, stock BIN and tune from there. There are many for the '7747 to pick from (yes to $42 mask).

RBob.

 

If you need any $42 stock bins gearhead efi hosts them .
seems really advanced for swirl port heads.

 

Thank you for the location of stock bins. It's my understanding that my truck came with that ecm. I am also running vortec heads on this set up.

 

Dynamic efi ebl is a good choice for replacing the 747.
already has bins for vortec as a starter. Be conservative on l31 timing