See my build in my sig.

I recently switched to EBL and love it. The issue here was present with my old '063 ECM on the old 305 engine, the '063 on the new 406, and still there with EBL.

I attached my low VE table. It was generated by EBL with lean cruise and canister purge both disabled. It's a nice looking VE table. Very smooth from cell to cell. (RPM's up the left side, MAP across the top)

Notice the red numbers. VE's above 98%. This range of RPM/MAP readings results in a "chugging/lagging" at cruise, and a "flat spot" in mild acceleration. I wouldn't mind so much except that range is at +/-65 mph cruise and gentle around-town driving. (Yes, I actually can drive it from time to time without my foot in it!)

Feedback from software shows that the O2 sensor goes dead lean in this range. No vacuum leaks in the system. Everything (that I can think of) has been either tested or rebuilt.

It is very important to note that this does not happen when in Power Enrichment mode, open loop, or lean cruise. All is smooth and sweet.

So someone suggested I set it to be in PE mode in that range, or to be in open loop. Good idea, but then I don't get lean cruise and gas mileage goes down. So I don't really consider those as viable options.

It may be that the fuel is dropping out of suspension in this narrow range of conditions. That means the ultimate fix may be to go to multi-port injection. Of course, that means a bunch of money I don't have right now. I don't think I can modify this intake manifold to take multi-port injectors.

But-- I'm not sure it's a fuel drop-out issue. The intake is heated from engine oil on the bottom. Plus the whole build is targeted to maximize intake and exhaust velocity for throttle response and torque-- 175 cc heads, manifold rated "idle-6000," 1-5/8" header tubes, mild cam, etc-- plus it doesn't happen in lean cruise, PE, or open loop.

Another option may be to switch from "BLM" tuning to a wideband O2 sensor. But that's another chunk o' change, with no assurance of a fix.

Any ideas what is going on? Lately I'm grasping at straws.

 

SR71

What is your BPW constant is set to? What happens to fuel pressure at that RPM - engine load range?? EBL has provision to support VAFPR - is it correctly setup?

//RF

 

BPW is 98 at 80 MAP, 120 at 30 MAP (idle). All other BPW entries are linear from 0 to 80 based on those two entries. Entries were calculated with the XL spreadsheet that came with EBL. Variation is solely by fuel pressure, which is 20 psi at idle and 30 psi at WOT.

So, fuel pressure is increasing from ~21 psi at the bottom of that range, up to ~26 psi. Verified by the gauge attached to the injector side of the fuel pressure regulator. No pressure drop-off.

BobR told me the BPW entries would't change the VE table, and it seems he was right about that.

 

Best bet is to re-calculate the BPC table with a lower injector flow rating. This will increase the BPC at each point which will then increase the PW. Try reducing the basic #/hr rate by 5 #, then see how the VE table forms. If it provides enough head room on the VE table you are good. otherwise will need to bump the BPC a tad more.

I have a feeling that it is the Holley Pro-jection intake manifold. Ronny uses the same manifold and has had the same issue. My guess is that the intake is resonating in that RPM range. Which increases the VE.

> BobR told me the BPW entries would't change the VE table, and it seems he was right about that.

I think this was in regard to using a VRFPR vs a standard TBI FPR? And changing the BPC vs VAC table to match the FPR. Changing the BPC vs VAC with no other changes will directly affect the final PW. Which the VE table can be used to bring the PW back in line.

RBob.