7747 VE Adder table questions

[Dieselsj]

I cleared my VE Adder table and added the values to the main VE table when I started my tuning process. A couple things I have noted -

- zeroing the adder table didn't give me zeros...it gave me values of 5. I assume that is just a TunerPro thing.

- Adding the values to the main VE table gave me about a dozen cells with values >100. TunerPro maxed those at 99.xx

- My low VE values are in the 50's

I would assume that I could tweak the 3200 rpm line of the main VE table by subtracting 25, and adding 25 to the 3200 cell in the Adder table. Then in the Adder table I could reduce the 3600-4800 cells to compensate for lower VEs at the higher RPM to keep the engine from using the 3200 values in that higher range. However I read a post where someone said testing with a WBO2 showed that this did not work.

Question 1 - does the VE Adder able effect the VE values above the 3200 line of the main VE table?

BPW - in all of the 7.4 BINS, the value is set to 134. However when I plug my values into the spreadsheet (80lb@13psi, 4.25 bore, 4 stroke) I get 139. To get a BPW of 134 I need to set the injector size to 83@13psi. To further complicate things, the actual GM spec for the factory injectors in my 87 is 90lb@13psi. If I use 90@13psi in the spreadsheet, I get a BPW of 123.6.

Question 2 - If I drop the BPW to 124, what will the overall effect be on the operation of the engine? I'm going to assume that this is going to want to drive the BLM/INT values higher as the system will be expecting more fuel to be injected and pushing the BLM/INT higher because it isn't getting it.

Question 3 - if my assumptions are correct on #2, then that will drive my VE values higher as I try to get the BLM down near 128. This seems to be the opposite of what I want since my VE table is 50-99 and I'd really like to see it in the 30-80 range (there is no way a stock low compression peanut port 454 would have a VE in the 90's).

Question 4 - am I way off in my thinking here?

[dave w]

You are asking good questions, which require detailed answers. Some of the questions would be best answered by the GM Engineering Team that designed the 1227747 and the $42 definition.

Some $42 tuners "think" there is some kind of GM Engineering "Magic" above 3200. Some $42 Tuners think the VE value for RPM's above 3200 RPM are interpolated from the VE cell the ECM was using prior running above 3200 RPM's.

I have also noticed that TunerPro won't actually accept Zero's in the Adder VE table, so it's likely a TunerPro thing.

I've tuned several $42 TBI systems. I think TBI injectors have a "Butter Zone" vs. VE Table Values. I think the "Butter Zone" VE Tables Values work best between 40 - 90. Seemingly, low RPM values of close to 40 and high RPM VE values close to 90 work best at keeping the TBI injectors in the "Butter Zone".

I've worked with several V8 $42 .bin files and have noticed that most V8 (5.0, 5.7, & 7.4 liter) BPW values are close to 134. GM used different Injector part numbers for the 5.0, 5.7, and 7.4. liter to keep the BPW close to 134. When possible I like to keep V8 BPW values between 128 to 140 ( 134 +/- 5%). When possible I like to keep fuel pressure close to the stock fuel pressure, personal preference. I think injector parameters and offsets are GM Engineered to stock fuel pressures. I hate the "Math" required to "Fix" injector parameters and offsets, so I use stock fuel pressures and I don't need to do the math.

I look at BPW as a course tune adjustment. If all BLM cells are rich (below 128), then it makes sense to change the BPW. If all the BLM cells are lean (above 128), then it makes sense to change the BPW.

I look at VE Table tuning as a fine tune. When some BLM cells are above 128 and some BLM cells are below 128 it makes sense to adjust the VE table.

Tuning $42 is a fine balance of BPW vs. VE Table values between 40 ~ 90.

I often find injector flow rates a challenge for the following reasons: What Injector is Rated to Flow? vs. What an Injector is actually flowing? vs. the Injector Flow (BPW) programmed into a .bin file are not always the same value.

dave w

[Dieselsj]

So, what you are really saying is that I need Santa to bring me a dyno and I need to do a lot of research and testing...

OK, putting the BPW aside for now because I have my VE table very close and don't want to mess it up by changing BPW right now, let's just focus on how this thing works above 3200 RPM. With the 4.10 gears and no overdrive, freeway was often 3400-3600 RPM. Logically the VE isn't the same at those RPMs as at 3200, and logically VE values would decrease as RPMs increase. And this is what we see in the ADDER table.

This is from the VE table description in TunerPro -
The adder table (Fuel VE 2) adds to every RPM column and after 3200rpm the adder table uses the MAP cells at 3200rpm up until 6400rpm.

Since I do need to do some tuning above 3200 I guess all I can do is spin the engine up there while logging, then change the ADDER table and see if I get the desired effect. Of course I'll need to watch my PE settings as there is a good chance the throttle will be open enough and MAP values adequate to trigger it.

Thanks for the BPW insights.

[dave w]

A dyno would be nice. The next best thing to a dyno would be to upgrade to the 16194727 TBI computer (http://www.gearhead-efi.com/Fuel-Inj...out-Directions ) using WBO2 tuning (see attached pictures.

dave w

[Dieselsj]

A dyno would be nice. The next best thing to a dyno would be to upgrade to the 16194727 TBI computer (http://www.gearhead-efi.com/Fuel-Inj...out-Directions ) using WBO2 tuning (see attached pictures.

dave w

I have looked at that swap and I'm on the fence between that or going with the DynamicEFI when I'm ready to upgrade ECUs.

[dave w]

I recently helped out with a TBI conversion on a 1971 International Pickup. We were equally divided on the choice of Dynamic EFI or the factory 16197427.

The decision hinged on the future plans for replacing the Borg Warner Automatic Transmission. The 16197427 will control either a 4L60E or 4L80E. Dynamic EFI will not control either the 4L60E or 4L80E.

The Dynamic EFI will do VE learns. The 16197427 will not do VE learns. The Dynamic EFI will require a few 1227747 ECM wires to be reconfigured. The 16197427 requires all the 1227747 ECM wires to be reconfigured.

dave w