caen fred Posted October 16, 2009 Share Posted October 16, 2009 Hello, I am running a custom FI system. 2 GM injectors All wired to a GM Control Module With Map, water temp, O2, tps sensors all in place. The car is working fine but lack tuning ability. I am thinking of going Megasquirt my question is: is it a plugin into the GM harness module? Do I have to redo the harness ? That is # one of a long series of questions to come Fred Quote Link to comment Share on other sites More sharing options...
softopz Posted October 16, 2009 Share Posted October 16, 2009 no plug and play. depends are you trying to control fuel and spark? Now is your GM ecu a piggy back type ecu or is controlling fuel and spark. PLease read www.megamanual.com it will answer most of your questions just getting started/ than read it 4 other times just to let it marinate inside. Quote Link to comment Share on other sites More sharing options...
jerryb Posted October 16, 2009 Share Posted October 16, 2009 Contact Six_Shooter He also runs a GM ECM module and uses http://www.tunerpro.net/ . He has full tunability, the system has huge support and I believe very affordable..... Nothing againt MS....just an option for you to consider Quote Link to comment Share on other sites More sharing options...
Six_Shooter Posted October 16, 2009 Share Posted October 16, 2009 It's true, I run a GM ECM on my L28 turbo in my Datsun. I'm not running a TBI ECM, I'm actually running a 1227749 with $59 ( code59.org ), and it runs very well, with full tunability. I can't read the service number on your ECM, but should be of the same era as the '7749/'8063/etc. This requires a small adaptor to use a new, more commonly available EEPROM ( 28 as opposed to the original 24 pin ), a datalogging cable, to plug into the ALDL serial connection, that can be home made for a few dollars (serial) , or bought with connection options to USB. A programmer, which can be found for as little as about $40, download Tuner Pro RT for free ( small donation to get rid of the 10 second delay/nag box at start up ), and with the proper datalogging files, you're tuning for possibly less than $100. This wouldn't give real time tuning, but can be tuned without the need for real time. If you want real time tuning you'd add about $200 for the EPROM emulator and a small signal amplifier that the older GM TBI ECMs need. If it were me, I would probably use the '7747 ECM, which runs the $42 code ( FYI "$42" is actually a hex number, to identify the code that the ECM uses, not how much it costs. ), and has been hacked apart put back together modified, and just very well known in the DIY (Delco) tuning community, so there is a lot of information out there. I actually have one of these ECMs sitting on my test bench, that I had in a friends truck for a while, with a home made EEPROM adaptor. Had it running his 409 in his '67 Chev pick up, but didn't have the correct CALPAK to make the injector scheme fire right for the V8, discovered this after swapping to a different ECM, more suited to his application. There is another option for tuning the GM TBI ECM, and that is to have what is called an EBL (Embedded Lockers system) installed in the ECM, this replaces the daughter board, where the CALPAK and EPROM are installed under that small removable cover, and gives real time tuning, along with adding some other features, such as E-fan control, nitrous control, etc, through the use of additional outputs. I'm not bashing MS either, I just find that the GM ECM has more tunability, more functionality and can be emmisions compliant, even though the swapping of another manufacturer's ECM into a different vehicle is a grey area. I keep looking at the MS and there is always something that keeps me from using it. I have a fairly long list of why nots, but I won't post that here. Just pointing out that before you give up on the GM (Delco) ECM, that they are very tunable, and very affordably too. Quote Link to comment Share on other sites More sharing options...
Six_Shooter Posted October 16, 2009 Share Posted October 16, 2009 no plug and play. depends are you trying to control fuel and spark? Now is your GM ecu a piggy back type ecu or is controlling fuel and spark. PLease read www.megamanual.com it will answer most of your questions just getting started/ than read it 4 other times just to let it marinate inside. Actually there is a PnP option for the GM TBI harness to the MS: http://www.diyautotune.com/catalog/megasquirtii-tbi-746747-adapter-pcb-p-187.html?osCsid=703635eb22e3249b344f75a377258d12 It's an adaptor that goes between the MS and the GM haness connectors. This adaptor would actually work for a few more ECMs than just the '7747/'7746 that DIY Autotune lists. FYI, The GM TBI ECM is a "standalone" type system that will control both fuel and spark completly. Without knowing all the details of the OP's install it's hard to say how much of the capabilities he is using, but it is very simple to have both fuel and spark control on an L-series engine, using a GM ECM, by simply using a L28 dizzy and a GM dizzy ICM (Ignition Control Module). This GM ICM option would and is also a good way to interface easily to an MS system as well, since the GM ICM will supply the RPM reference and control spark timing with a couple simple connections to the ECM/EMS, without the need to use coil drivers built into the MS, which seem to have been a problem for some people from time to time. The GM ICM triggers the coil directly. Quote Link to comment Share on other sites More sharing options...
caen fred Posted October 16, 2009 Author Share Posted October 16, 2009 Thanks for this valuable info. Looks like I have son reading to make. Quote Link to comment Share on other sites More sharing options...
Six_Shooter Posted October 16, 2009 Share Posted October 16, 2009 If you have any specific questions, shoot me a PM, I can direct you to some links that should be of help, if you decide to keep the GM/Delco ECM. Quote Link to comment Share on other sites More sharing options...
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