Pertronix Digital HP ignition box any good?

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Bob Hollinshead
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Pertronix Digital HP ignition box any good?

Post by Bob Hollinshead »

Anybody here have any experience with the Pertronix Digital HP ignition box? any good? It looks like it has some nice features for the price but with only a 90 day warranty I'm a little leery. https://pertronixbrands.com/products/di ... zed-finish
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Re: Pertronix Digital HP ignition box any good?

Post by Geoff2 »

Well I suppose a 90 day warranty is better than the sunset warranty.........
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Re: Pertronix Digital HP ignition box any good?

Post by novadude »

I've personally never had any luck with pertronix ignition components. I've had both a points conversion kit and a pertronix rev limiter fail after very little use. YMMV.
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Re: Pertronix Digital HP ignition box any good?

Post by Walter R. Malik »

Bob Hollinshead wrote: Tue Jun 22, 2021 10:42 pm Anybody here have any experience with the Pertronix Digital HP ignition box? any good? It looks like it has some nice features for the price but with only a 90 day warranty I'm a little leery. https://pertronixbrands.com/products/di ... zed-finish
The Pertronix 1 and 2 points eliminators work well but, their 3, which is an ignition within the distributor, doesn't last; their "second strike" box is great and their coils are OK, if they are chosen correctly for whatever brand ignition is used.
The separate ignition box is kinda new and I haven't had time to evaluate that yet.
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Re: Pertronix Digital HP ignition box any good?

Post by nabx22 »

I have one on a 511 bbc.I kept having problems with an msd 6al2 and replaced it with the digital hp 1.5 years ago.No more problems
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Re: Pertronix Digital HP ignition box any good?

Post by JohnP »

I'm pretty sure their add on rev limiter fails because the power transistor they use is way too small.

I added that function to my Vampire system and I use a TO-247 size. I've seen a photo of the Pertronix internals and think they are using a TO-126 size.

This type of rev limiter is what I call a "pulse swallower". The points or stock transistor ignition is still pulling current through the coil during dwell and trying to make the spark, but the add on rev limiter gobbles up the high voltage pulse, then it dissipates all the energy stored in the coil. You can hear the coil make noise as it's trying to fire the plug.

The conventional style of rev limiter simply never allows the coil to enter dwell, or if it's CDI, the storage cap to charge, so nothing gets hot or makes noise.
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Re: Pertronix Digital HP ignition box any good?

Post by BTZ201 »

Nabx22, what distributor are you using with your pertronix box?
I was looking to buy the pertronix 510 box also. Was planning to buy the bundle package they offer with there distributor and coil to replace my stock hei as I am planning to run a tunnel ram eventually.
Any thoughts appreciated.
Thanks,
Brent
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Re: Pertronix Digital HP ignition box any good?

Post by nabx22 »

I am still running an msd but I switched to the pertronix coil they recommend for the digital hp.The msd coil I had failed too.
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Re: Pertronix Digital HP ignition box any good?

Post by bradrs »

JohnP wrote: Fri Jun 25, 2021 9:28 am I'm pretty sure their add on rev limiter fails because the power transistor they use is way too small.

I added that function to my Vampire system and I use a TO-247 size. I've seen a photo of the Pertronix internals and think they are using a TO-126 size.

This type of rev limiter is what I call a "pulse swallower". The points or stock transistor ignition is still pulling current through the coil during dwell and trying to make the spark, but the add on rev limiter gobbles up the high voltage pulse, then it dissipates all the energy stored in the coil. You can hear the coil make noise as it's trying to fire the plug.

The conventional style of rev limiter simply never allows the coil to enter dwell, or if it's CDI, the storage cap to charge, so nothing gets hot or makes noise.
The downside of stopping the coil from dwell, is that the rev limiter isn't as responsive as the "pulse gobblers", at least not any that I have tried. You can get a nice smooth spark cut, and even have it retard slightly as it hits the limit, depending on how the clamp circuit works to stop the spark. If you try to rev limit based on the start of dwell, you're probably using rpm data that is close to a revolution old. When set up as a pulse gobbler, it can basically set a window after the last spark, and then not spark during that window. So the response can be immediate.

The Petronix was inconsistent because they clamped it wrong, and other issues. There were a few other brands that worked to clamp the spark, and didn't have the same issues.
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Re: Pertronix Digital HP ignition box any good?

Post by JohnP »

The rev limiter in my "Universal" knock retard unit is an interrupter style. It computes a running average of the period between spark events, then compares it against the period for the selected limit.

For an eight cylinder at 7500 RPM, the updated "new average period" would be 2msec old. One spark event.

Every spark event, the limit detection code checks for over rev, and if detected, software prohibits dwell start. In effect, the points don't close for that cylinder.

At the selected limit, software fires two cylinders, skips one, then repeats, resulting in a 33% drop in power. If the engine pulls 100 RPM above the selected limit, software skips as many sparks as needed.

For a six cylinder, this scheme would always misfire the same two cylinders, so it fires three, skips two. This results in a smooth 40% drop in power, while rotating the misfiring cylinders. Again, if the engine pulls 100 RPM above the selected limit, software skips as many as needed.

I have a video showing the soft touch feature on a one channel Vampire. It's a pulse gobbler but the software principle is the same. Fire two, skip one:
https://www.youtube.com/watch?v=muEu4NFFfcM

Vampire retard principle of operation:
https://www.youtube.com/watch?v=gnEFsYpKmPM

Four channel Vampire operation:
https://www.youtube.com/watch?v=5NjYMpQwaQ8

Vampire retard and rev limit waveforms:
https://www.youtube.com/watch?v=rPNx9zCzAPU
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Re: Pertronix Digital HP ignition box any good?

Post by bradrs »

JohnP wrote: Wed Jun 30, 2021 6:00 am I have a video showing the soft touch feature on a one channel Vampire. It's a pulse gobbler but the software principle is the same. Fire two, skip one:
https://www.youtube.com/watch?v=muEu4NFFfcM
A bench test of some of those other brand clamping style rev limiters would be interesting. Yours looks like it is working right, I don't think all of the others can say the same.

My previous experience designing limiters taught me that the bench test can't show you how smooth they are in operation. The signal RPM isn't affected by the limiter, and would stay smoothly at whatever RPM you set. And you can't really compare the limiting on 2 different vehicles either. Flywheel mass, # cylinders, etc, can result in some big differences in how smooth the same limiter sounds.
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Re: Pertronix Digital HP ignition box any good?

Post by JohnP »

That is a fact. All true.

A customer has a 1970 Mustang with factory rev limiter, but it's dead.

NOS are available for about $1k, so instead, guys are shoe horning the Pertronix into the stock rev limiter housing.

He's sending one to me to convert for him so I will have photos and will run it on the bench.
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Re: Pertronix Digital HP ignition box any good?

Post by BTZ201 »

Thanks for the info nabx22.
I will let you guys know how it works for me when I purchase and install.
Thanks,
Brent
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Re: Pertronix Digital HP ignition box any good?

Post by dfarr67 »

Any update?
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Re: Pertronix Digital HP ignition box any good?

Post by JohnP »

I designed this to replace the OEM rev limiter used in the Boss 429 Mustang.

https://www.youtube.com/watch?v=ErUbzVbyXhw
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