You know I take that back about the MAF.. I was just looking over another file that I have and it also shows 10 g/s so I suppose that is possible.

EDIT: What brand injectors do you have and what was the fuel pressure they are rated at? I see you did set the constant higher than the injectors are rated at but you really cant tell exactly what theyd flow unless you know what the fuel pressure is they are calculated for. For instance LS1 injectors are rated at 28 lbs but this is only for LS1 since they have slightly higher fuel pressure than LT1s... throw those 28s on our cars and they arent any more effective than stock 24 lb.

 

I have Accel's, which one site siad they were rated at 37 (like SVO's?) while another site says 43.5psi? I guess fuel injector constant should be around 56.5 if they were done at 37 psi correct?

 

http://www.altech.com.pl/wbt/_specy/accel_fi.htm

@ 43.5psi it flows 48lb/hr, so i can adjust my constant a little, but I doubt it being off by that much is causing this problem.

 

If done at 37 then you should enter 48 but if done at 43.5 then you should enter something considerably less like 35+/-.

 

I just did some figuring and my math shows that with only 37lbs which is what stock is supposed to be with the engine idling, those injectors would actually only flow about 41lb/hr

 

I rechecked my fuel pressure on my car:

idle: 38
WOT: 45

As far as you were saying with the idle fuel pressure, I thought we just take into consideration the WOT numbers (like the test numbers that accel showed)? You need to have it set at 1 or the other right?

What amazes me is that out of all the guys that have tuned their own rides, only you and fred are trying to help. I appreciate it. I will try and lower the inj. constant tonight. I just dont want it to be a problem when tuning WOT.

 

I just want to re establish that my car is rich (according to the smell) and that the lean condition can be false if you are too rich correct?

 

No, the O2s are telling you its rich and so are the BLMs. The only wya you can have a false lean is with a misfire or a header leak.

As far as the fuel pressure at WOT vs idle... you tune looking at idle fuel pressure.

 

Why not just run two simple tests. 1st, kick your injector constant down by 5 or so, run the car and check results. Then kick constsnt up by 5 or so, rinse and repeat. A couple littl tests will prove an injector constant question in a heart beat. Also. make absolutely sure you have no exhaust leaks, none, not even a whisp. Air injection tubes (if you still have them) are notorious for giving problems. Leaking air in the exhaust stream would show a lean condition and the PCM will start dumping fuel like a Banshee.


Good luck

Steve

 

Thanks Steve. I did do that last weekend and got good results with 40 for the inj. const. Does that seem strange for 48lb/hr injectors? I do have an exhaust leak down by the colector on the mufflex y-pipe. The damn band clamp wouldnt crank down all the way and seal it off. I dont know if thats affecting me though.

 

If you are running a Z06 MAF on stock MAF tables then you will run leaner given everything else is correctly set. Like your injector constant, etc. You can reduce the constant like every one is suggesting but I would change the MAF tables for the new MAF.

It's all the same in the end but I like changing the values were the physical change is on the car. I have ZO6 MAF values interpolated for the LT1 table if you want to try them.

I would then set the constant to what it's suppose to be and increase the "low pulse width injector offset adder vs BPW" table. Your injectors are huge and they aren't good at flowing with a pulse width of 1-2 ms like the stockers. The adder is too low for these injectors. You need more added so the injectors really open when the car is idling. Both these changes will get the BLM back down. My .02.

 

No. You set your flow constant based on the "no vacuum" fuel pressure reading. That is what the fuel pressure regulator controls DIFFERENTIAL pressure at. The regulator does not control rail pressure, except to reflect the vacuum in the intake manifold.

Injectors are flow rated at DIFFERENTIAL pressure, not rail pressure. Differential pressure is the pressure the injector sees at its inlet (rail pressure) MINUS the pressure is sees at its discharge end.... the vacuum in the intake manifold. At WOT there is no vacuum, so you want the rail pressure to be 43.5psi (stock example) to insure the injector flows at rated capacity.

When there is vacuum on the intake manifold.... remember vacuum is a negative (-) pressure.... you need to subtract the manifold pressure from the rail pressure to get the DIFFERENTIAL pressure.... and it is the DIFFERENTIAL pressure that defines the flow through the injector, not the rail pressure alone.

Lets say you set the AFPR at 43.5psi with no vacuum compensation signal. When you attach the vacuum signal at idle, lets say you have 18.4"Hg vacuum in the intake. That means the pressure in the intake is -9.0psi. When you connect the vacuum line, the rail pressure (what you see on your pressure gauge) will drop to 34.5psi. But the differential pressure across the injector is:

(Rail pressure) minus (intake manifold pressure) =

(34.5) - (-9.0) = 34.5 + 9.0 = 43.5psi

Again, remember your math... minus a minus equals a plus....

 

Did you try and find a part # on the injectors, so you could check to see what they are really rated at?

 

I didnt pull them back off, but I looked with a flash light and dint see any numbers.

 

Can you shoot me over an email with the interpolated numbers. I'll take a look. Thanks.