I've hit an issue that has me stumped. CFI, Renegade intake, Dart 200cc SHP heads, 9.5 compression 90lb injectors Voodoo 256 cam. 28psi Vacuum adjusted fuel pressure, parallel plumbed injector towers EBL controls all of it. I'm getting a seriously lean spike right at 2000-2500 rpm. It's like the fuel just drops out. Map starts climbing over 50, which makes the VAFPR add tons more fuel, but it still pegs at 22 afr unless I give more pedal and AE kicks in. After I pass about 2500 RPM it smooths right out, MAP drops back down in the 30s and fuel pressure drops accordingly and she runs great. What am I missing? Learns end up pegging the VE at 100 in these cells. Has anyone else had this issue? And if so, how did you solve it? When it happens the car just hits a brick wall, it's really harsh. Thanks for any ideas or help you can offer.

 

With the VE topping out, increase the BPC - BPC vs VAC table by 15% (* 1.15). Then decrease the VE table(s) by the same 15% (* .85). Can use the multiply function in TunerPro with the entire table highlighted to do this.

The VE table now has more headroom.

RBob.

 

Thanks for the reply, Bob, but the spike is only at the 2000-2500 rpm area. Below that range all is well, above that range, all is well. So should I just adjust BPC only in the range affected? For example, at 1800 rpm the VE's fall around 12 at 30 map to 40 at 60 map. Then when you get to 2100 they want to spike, with it hitting 100 at 2400 rpm @55 map. Then once you get past 2600 it drops back down to around 33 @ 40 map 2800 rpm and 51 at 55 map @ 2800 rpm. It's just in that area between 2000-2600 that it wants to spike at the ultra high VE. I'm not arguing your response, and I'm definitely gonna try it, I'm just making sure we're talking about the same lean spike issue. In that RPM range the engine falls off a cliff.

 

The BPC is based on vacuum, not RPM. So can't change it only at the lean point/area.

Does the VE also go lean at WOT? Or just at part throttle?

RBob.

 

Sounds like your ignition is dropping out, if you're not burning fuel, you're not consuming oxygen.

 

At wot it just powers right thru the area. I'm gonna do a few learns and then I'll post the tables. Work is winding down this week, so I'll be free to get all that done this weekend. I expect to see a waterfall from 2500 to 3000, but we will see what happens. The low speed graph is pretty great, though.

 

I haven't forgotten, but the weather has been pretty bad all weekend. As soon as we have a decent day, I'll get it all done.

 

RBob your solution is working, no cliff although it still is adding fuel in that area every time I do a learn. I usually get 4s in that area now instead of the 12s I was getting before and the overall curve is much much better. Idle is rich now, even after dropping it way way low in the table (in the low 3 area) but I guess that is to be expected with the 90 lb injectors and the high pressure. Overall drivability is much improved, although at neighbor hood creep along speeds it can get harsh, but I think I have too much prop gain, that's next on my list to check. Just off idle creeping down the street you can watch the afr really fluctuate. Thanks for the advice!