Vortec Black Box 5,800 limit

[Fast355]

After all these years. Stumbled across how to get one over 5,800 rpm. It works and works well now. Working with a 350 capable of doing 6,500+ this weekend. Set the last cell in the minimum dwell time table labeled 2,400 rpm from the factory 2.004 to 1.75 msec and 6,500 limiter now. The computer was commanding minimum dwell time at high rpm that exceeded the amount of time available between coil firings resulting in ignition misfire that felt like a rev-limiter. The Black Box can finally rev out over 5,800 rpm. Wish I had known this 15 years ago! The 0411 has shorter dwell as the rpm increases. 1.75 should allow for atleast 6,500. The feeling before altering the dwell time was exactly the same as the old TBIs when the injectors went static. It would lose power and misfire. What pisses me off is years ago I gave up on trying to get one over 5,800 and the problem was in plain sight. What pisses me off is years ago I gave up on trying to get one over 5,800 and the problem was in plain sight.

[ralmo94]

Thanks for sharing! I always wondered about that, cause you can set the rev limiter higher.
Good work:rockon:

[Fast355]

Thanks for sharing! I always wondered about that, cause you can set the rev limiter higher.
Good work:rockon:
People thought it was a secondary limit in the code. Turns out it was calibration right in front of us the whole time. If you figure 0.5 msec spark duration at 6,000 rpm you have 2.0msec charging time. Go much over 5,800 and you get misfire. Decrease the charging time to to 1.75 msec gets it up over 6,500 before your total exceeds 2.25 msec between firings.

[Fast355]

Just ran through the math.

6,800 rpm ÷ 60 sec =113.33 rps x 4 firings per rotation =453.3 coil firings per second. 1 second ÷ 453.33 firings is 0.002205 sec or 2.205 msec between firings. Keeping 0.0005s or 0.5 msec for firing duration that gives a value of 1.705 msec charge time at 6,800.

Given the same math there is about 1.80 msec charge time at 6,500 rpm. The 1.75 msec value I used would allow it to turn a bit higher than the fuel shut-off at 6,500 without overly decreasing spark energy from decreasing the value too much.

[ralmo94]

Makes Perfect sense
I'd give it a try, but my black box truck still has the original valve springs. I try not to run it much past 4600.
This is great news, that's one of the main reasons people swap the 0411, or so I've read.

What tuning platform do you use on black boxes?

[Fast355]

Makes Perfect sense
I'd give it a try, but my black box truck still has the original valve springs. I try not to run it much past 4600.
This is great news, that's one of the main reasons people swap the 0411, or so I've read.

What tuning platform do you use on black boxes?

TunercatsOBD2 since they are free to me to tune being VIN Unlimited.

[ralmo94]

I use HP, there seems to be a lot missing and undefined.

[Fast355]

I use HP, there seems to be a lot missing and undefined.

Several big items in the calibration like single vs dual cats. I converted a 305 file to dual cats for my 99 Tahoe.

[ralmo94]

Rolling idle perameters are not even available with HP.
Raise idle and rolling adder adds on top of it.
I also caught they labeled the input shaft pulse count as output, change that to 40 and you get a mess.

[1project2many]

Very interesting. And it makes sense. Thanks for sharing.