Yep the car runs just fine. I just need to do a little more fine tuning. The only thing I can't get to work so far is the shift light, which is no big deal sooner or later I'll get it to work. It runs a lot better with this 749 ecm compared to my 730 with little tuning.

 

Is this with the blower? Any times or other testing (even emissions)? What's your max duty cycle with those 30# injectors?

 

Yep I'm running my D1SC with the 4.25 pulley. Last datamaster run I hit 6.1 psi at 5200 rpm with belt slippage. I ordered a goodyear gatorback poly v belt, so I should gain 1-2 psi hopefully. I'm in Montana so your guess is as good as mine when it comes to emmissions. I took the AIR system out to clean up the engine compartment, but I still have a fully functional egr with the 749 ecm. So far the highest I've seen for the injector DC is 67%, so I have room for headers and a good exhaust and a couple more pounds of boost. As for track times the nearest track is 300 miles away, but one is supposed to be built next summer here. And I haven't hooked my Gtech up to my 91 Z yet. I can tell you that this feels more responsive with the 749 over the 730 with a fmu.

 

any runs with the fmu? (just trying to get some indication of the power level that you're running at...).

from the duty cycle, making some educated guesses (BSFC of about .55, 43Lb/hour fp...) you're only feeding it enough fuel for 292hp...

 

I took the fmu off when I intalled the 749 ecm. I'm running 44psi right now and it is vacume referenced so figure 50psi at 6psi of boost. This is a completely stock 305 and at 9psi of boost I should be making around 330 hp is what I figured, so that is how I sized the injectors. I think the formula I used had a diff. BSFC for the calculation. I remeber it was diff. for turbo versus supercharged engines. I know some of the syclone guys are running 500~600 hp area with 70+ injectors, so add more hp for 2 more cylinders and 2 more injectors. With the injector driver mod you should be able to run 90lb/hr peak&hold injectors, which should be in the 800 hp area I would think.

 

bsfc is usually higher for a boosted application then NA. Typically NA is in the .40-.50 range and boosted applications are in the .50-.60 range. I chose .55 just because it was the middle of the range and a fairly safe guess.

The problem isn't with how much HP it would support, but how much it would support and still idle well. The real problem with the injector drivers is that they can't open and close the injectors fast enough to work well on a v8 with larger then about 36# injectors (at least not that anyone has proven). I recently got an explanation about why on the prom board (do a search), but to be honest, I'm not sure that I understood it correctly.

 

Thats why you use peak&hold injectors. They can open and close quicker. Then you just need to play with some of the injector setting like minimun desired pulsewidth to get it to idle with larger injectors. I used .60 for my BSFC in the calculation to get 30lb/hr injectors for my estimated 330 horse engine at 44 psi of boost. The inherent problem with large injectors is getting the pulse width down during idle conditions. This can be masked by using peak&hold injectors which react much quicker than the saturated style. From what I have conversed a guy on syty.net has a 4.3 V6 (350-2 cylinders) with 72lb/hr peak&hold injectors and it idles quite well after playing with some constants.

 

Just moving this post TTT. I'm having a tough time getting the olds to idle at all. I get maybe 4 seconds of ugly runtime. It seems super rich so I went way up in Injector Constant to try to lean out but it didn't seem to have an affect. Still getting no codes or ses lights. Way hard to believe. Shouldn't I be a able to idle reasonably well on stock SyTy VE tables?

Stiil struggling
Steve

 

go in the other direction. go for richer. sounds like a lean missfire sort of deal a blown 455 is gonna use alot more airthen a 4.3 v6. try more fuel see what happens.