Hi, I'm kinda new to the efi game and looking for some help. Got a 77 firebird with pretty nasty 327 chev in it and a really cool looking Holley twin tbi pro dominator injection set up that doesn't work worth a darn. Hoping to find some help on here on a better way to control it. Thanks for having me guys!
Welcome to the forum. What isn't working correctly?
Square body stepsides forever!!!
Well, it seems to run rich, a lot! We have tried all kinds of different setting on the contoller and nothing seems to work good. Of course running rich is only a speculation as I don't have any kind of an afr monitor on the car. We tried going e85 for a while and that didn't seem to help either. This engine definitely made significantly more power when it was running a carb. I also just really don't like the fact that there is no o2 or map control of the system. It was great technology in it's day, but that day has passed. So I was wondering if there might be a way to control the 2 tbi's for a total of 4 injectors with a gm pcm? I'm hoping that there is and that I can gain far more accurate and reliable control of the system. I'm not afraid of wiring or any of the mechanical stuff. I was and auto tech for 13 years and a heavy indutrial mechanic for 3 years. So I'm no stranger to working on things, but modifying any kind of efi system is a whole new game for me. Holley can sell me controler and harness that should work but with a lovely pricetag of over $1600 I'm not real interested in going that direction. I've heard for years now that the gm pcm's are extremely versatile and a great way to go. Do you have any thoughts. Just a little run down on the engine, it's a 69 327 block, steel crank, double hump heads, pink rods, 12.5:1 compression, ultradyne cam that I can't remember the lift on but it's huge, roller rockers, studded and girdled. Projected horsepower for the engine is around 550+. I look forward to hearing anyones input.Originally Posted by jim_in_dorris
Yes, 2 throttle bodies and 4 injectors have been done on a GM ecm. I believe gregs79 on this forum has done it, I know for sure a guy on fullsizechevy did it. O2 sensors, map, vss, tps, iac and computer controlled timing are really important, but all that is simple to add. Also the choice of which ECM for tuning will matter. With a big cam, it can be challenging to get idle working, but several guys on here can also help with that.
Square body stepsides forever!!!
Well that is very encouraging. I'll try to find those guys. Thank you very much.
I have had a hand in getting two Olds powered cars with custom 4bbl TBIs running well, which are street cars that get abused. One is making near your projected HP level, if it isn't there now.
One has a pretty large cam as well, it idles at 55 to 60 kpa (7 to 8ish in/hg). It was a bit of a challenge to get it to idle well, but it starts within about about a turn of the crank, when cold or warm. To do this, I had to ignore some of the numbers that I was seeing put out by the ECM/WBO2 and go by feel, and it's worked well for a couple years now in this configuration. :D
The man who says something is impossible, is usually interrupted by the man doing it.
Awesome! What PCM, throttle body, injector size, iac motor, map sensor and o2 sensor did you use? That's awesome that you did it on an olds, I've been considering doing my 455 that is in my 70 cutlass in the future as well. I'd love to hear all that you can offer about your experience with it. When you say you had to ignore some of the numbers was that mostly just letting it run rich at idle or more to it than that? I'm dying to find a cost effective reasonable solution to this problem.
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