VE coming out way over 100

[EagleMark]

That was really a pain! Your fuel pressure gauge was wrong and you had a ECM issue... I hate when that happens!

Well your set with a sweet tuning set up now!

[EagleMark]

And this is with the BPW already bumped up from 135 to 150. The BIN I'm starting with is ARJT, which I adjusted so that the VE2 table is zeroed out - just to make the tuning easier.

One thing is that the 135 BPW seems to come from a nominal fuel pressure of 12 PSI. My fuel pressure is steady at 9-10 PSI. Just working the math, this would seem to want to push the BPW up to about 180, all else equal. The only major mod to my engine is headers, but that might push the efficiency up a little. I don't mind trying the 180, but it makes me wonder how this ever worked in the factory.

This has been bugging me since this started and I knew it was wrong to change BPW just to try and add fuel. I tested it and it failed. So I did a lot of reading and came to same conclusion I did long ago when starting a tuning project on a built engine.

1. First you have to know approx HP engine will acheive.

2. Then need to have injectors and pressure to meet that HP number.

3. BPW or BPC is specific for injector size-CID- Fuel Pressure.

If you have enough fuel to cover WOT high RPM of built engine then the BPW or BPC should stay the way you calculated it. Then work on idle and cruise VE.

Here's a link to calulaters used for BPW on 7747 and an entire thread for calculaters and information.
http://www.gearhead-efi.com/Fuel-Inj...ull=1#post2589

[Mastiff]

If the VE of the bin you start with is already at 100% in some place though, you have no room to tune. As far as I know, the only option is to increase BPC.

[EagleMark]

$42 is the only bin known to have this mistake from factory. The areas that add up to over 100 are all in PE zones as well so extra fuel is added there. Increasing BPW is not the only option and it's wrong option. Raising fuel pressure or installing bigger injectors and calculating BPW is correct way.

EDIT: Robert has corrected me and there is more then $42...

[RobertISaar]

$42 isn't the only one....

in fact, one that comes to mind is $8F, which is the turbo 3.1 code. a LOT of over 100 values when combined.

[Mastiff]

I would think if the VE values are coming over 100 the BPC must have been calculated incorrectly. A factory engine sure shouldn't be able to get there. Maybe I'm misunderstanding though.

[RobertISaar]

for some reason, there are a bunch of factory calibrations that do this. whenever i see it, i jump into the algorithm to see if it gets truncated to $FF(d255), and it does in every one i've looked at.

supposedly, the early Q4 masks allowed an over 100% value but i haven't confirmed this.

[EagleMark]

Factory messed up! To many chief engineers and not enough indians... in the end you can add the 2 up to 150 but only going to get 100 output... and that is beyond the rules of tuning keeping it under 95 VE...

But in the end it passed all tests and EPA requirements. I wonder when they noticed and who got fired?

[srobertsfsj]

Now that I am back on the road and driving the Jeep again I wanted to look at addressing my hesitation issue and I ran across this thread. I have quite a bit of hesitation off the line and noticeable lag at speed and I give it gas but once it catches up it seems to have good power and I have a good tune with my BLM numbers looking good thanks to the helpful folks here. Reading through the thread I gathered some of the major things to look for are the pressure regulator, fuel pump, O2 sensor and voltage. O2 sensor is new, voltage is good and I am ruling out the fuel pump since I switched from a frame mounted pump to an in tank pump (both new) with no change. I don't have a pressure tester and money is tight so I can't buy both a tester and a rebuild kit just yet. Anything else that I should look for while I am saving up?

[FSJ Guy]

I would continue playing with fuel tuning and timing.

IMHO, tuning areas where the MAP and TPS are changing is the hardest. If you have good WOT power, chances are that it's not a fuel pressure issue.