This is a carry over from another forum.. I hope someone can answer this here.
I'm using ms-1 v.3 internal vb921 on a dodge neon
Steve wrote:
Tainted wrote:
Steve wrote:
I wouldn't suspect dwell if it's breaking up that low in the rpm range.
I'd be careful with dwell that high. One of my ignition modules failed after about 3000 miles set at 4.2.
There is the possibility that the thermal interface material I was using between the VB921 module and the case was inadequate though. But still I'd be careful.
Steve
OK now I'm confused. When I had dwell set at 4.0, I was informed that it was too low.... Breaking up at high rpms + 8k.
Now I see that 4.2 is considered high, 4.1 gave the same high rpm break up. Can someone explain this
Yeah, this is new information. But like I said, my heatsink solution may have been inadequate.
This has just brought up a good point. Boost Junkie mentioned that dwell with the Mitsubishi ignitor was only 3.5ms and worked fine. So why are we having to run such high dwell with these VB921 modules. Dwell is a function of the coil, not the ignition module.
I have a scope but not time. As soon as I free up some time I'll try to figure out what the dwell is on a factory setup. Although I'd imagine it's variable depending on RPM.
Steve
I'm also using a MSD coilpack
Last edited by big mike on Wed Aug 02, 2006 2:59 pm, edited 1 time in total.
* Do not use misfiring and high engine speeds and loads to set the dwell - misfires under those conditions will likely be caused by other factors, and will lead to you setting very long and damaging dwell periods. Recall that the dwell is shortened with higher rpm in any cases, so increasing the maximum dwell setting doesn't help at higher rpms. For example, with a 3.5 millisecond dwell time, and a 2.0 maximum spark duration, the rpm at which the dwell begins to be reduced is just 2727 rpm on a V8.
* Do not increase the dwell to create a 'hotter' spark. Increasing the dwell above the 'saturation point' does not make a hotter spark, it only makes a hotter coil. For example, for a 2.5 millisecond saturation time, the current is increasing to it's maximum for 2.5 milliseconds. If this is 6 Amps, then the average current during this time is about 3 Amps. During this time, much of the energy being supplied is building the magnetic field. However, after 2.5 milliseconds (once saturation of the magnetic field is achieved), the current is a constant 6 Amps, all of which is heating the coil, so it presents a much larger load on the coil. So leaving the dwell too long is a problem. As well, the VB921 goes into current limiting mode if the current gets high (6.5 to 7.5 Amps). If the current is kept below the current limit, the VB921 should not heat up much at all. However, if run with a significant amount of current limiting, it heats up pretty fast (which can ruin it). That's why you should lower it as much as possible without misfires under normal operating conditions. If you need a hotter spark, you need another coil.
How do I fix the high rpm misfiring? It's not a hotter spark i'm trying to get, it's the unit not acting like in spark cut a rpms above 8k
Lance, the issue is if we let the stock computer run the ignition then there's no high rpm miss problems even with the stock coil. There is definately something funky with either the hardware or software. We just don't know what it is yet.
This is a dodge neon wasted spark coil pack on MS1 v2.2 and v3.0 boards with VB921 ignitors. Firmware is 029q2. From what I've experienced, it's not nearly as much of an issue using an external ignitor from a 4G63 turbo mitsubishi.