Ignitech Vboost Control PSA

[redneksoldier]

I have been running the Ignitech unit with Vboost Control for several years now and have been satisfied with it. Got some cool mods working and some custom tuning. Awesome little box. I recently discovered that the Vboost Control portion was not working quite like I had assumed it was. When the key was turned on, the servo would make a full sweep from stop to stop as one would expect. Watching it on the laptop with the TCIP4 software, everything appeared normal. The feedback would go from 0mV to 5000mV during the sweep as it should. What got me digging deeper was when I was demonstrating the function to a fellow vmax owner, I set it to 5kmV (something I had never bothered to do before) at idle and it only opened a little less than halfway and showed 5kmV. Weird, right? I used the test function to open the servo further but it still only showed 5k. I thought maybe the feedback pot had gone bad, but everything tested good. I'll spare you the details of me tearing apart and testing everything under the sun and cut straight ot the fix. What I discovered was that the feedback potentiometer was wired incorrectly. It came that way. Whoever added the vboost servo harness tapped into a 12v wire for the sensor feedback instead of the 5v sensor supply wire. As a result, the servo would only travel so far (42% to be exact) before reaching the target of 5000mv and stop. Because the sensing circuit and/or the software do not have the capability to interpret or display anything above 5000mv, you do not see the issue when you turn the key on and the servo makes a full sweep. I cut the white/red wire off the 12v supply connected it to the 5v sensor reference source and it works perfectly. My advice would be to check the servo harness where it connects to the Ignitech harness. The white/red wire needs to be connected to the other white/red wire that goes to the MAP/TPS and located at pin #17 on the ignitech plug. Again, if your ignitech harness came pre-wired like mine did, you may want to check it. If you find the red/white wire spliced into the red wire, your vboost is only functioning at about 42% when it activates at the set rpm.

 

[Fire-medic]

Wow, free HP! Just from a wiring check, and deductive troubleshooting with a multimeter. One question: odes the VBoost open gradually as revs rise? Was the 42% value when it starts to open somewhere around 6K rpm? I think I've seen 5750 rpm listed as-when the VBoost starts, and then at something after 7K rpm, it's fully-open.

 

[redneksoldier]

Yes, because that is the way I have the ignitech programmed. It is pretty much exactly how the manual explains it. Opening gradually from about 5750 to 8k. I have played with the settings a lot over the years but all that was for nothing because it really wasn't working right anyway. I did the tests without the engine running using the test and programming features of the ignitech servo control, a meter, and the digital display of the feedback in the software. The 42% was due to the incorrect feedback coming back to the ignitech. The ignitech thought it was at 100% because it satisfied the 5v feedback that it should see at 100% when in reality, due to the incorrect reference voltage being applied, 12v would have been 100% 5v being 42% of 12v. So the actuator was actually only 42% open which I verified visually being less than half of its full travel and that's what caused me to dig deeper.
The ignitech can be programmed to open vboost however, whenever you want using rpm, throttle position, manifold pressure, or any combination thereof. The possibilities really are endless. I've tried a bunch of settings and I always come back to the stock program at some point because I like it best.

 

[one2dmax]

Does this view give you any info on it (older pics).

 

[Traumahawk]

Thanks for the Info Dustin, also great info.

 

[Waxonwaxoff]

I remember Sean Morley identifying a problem with one of the supplied harnesses. I got my Ignitec from Sean.
Which was supplied with harnesses for both early and later systems. It was for a project but never got fitted. I still have it. Thought it's worth keeping just in case I have an ignition box go bad.

 

[redneksoldier]

Does this view give you any info on it (older pics).

Thanks, Sean. I see the one on the far left does not have the red/white spliced into the red wire like mine did. I believe this one was one of the very first that were shipped out with the servo control. I honestly do not remember where I got it from and I may have bought it second hand, so the vboost harness may have been added after it was purchased.

 

[one2dmax]

Some of the early kits the vboost part of the harness was included but customer installed. The newer harnesses we offer have it already installed.

 

[wayne billings]

Hello sean I think I am having ignition issues. I warmed it up, hit the highway and after a mile or so it would not rev clean and lost power. I checked and found #1 cylinder lost fire.I checked from coil to plug, fine. Also the pick up coils check fine as per my factory manual (5 wire '86) . I read that you have a diagnosis kit for this. Would you please let me know the terms and availability Thanks for your help. Wayne. member

 

[one2dmax]

Quite likely the CDI box has given up. Pretty common for the 85-89's