Data logger engine rpm trigger issues
 

I got a data logger(RPM out of OK) to get some info on the Camaro/IA project. I am using a DUI HEI on the motor. Run one on the 78 for years. HEI tach terminal has worked every aftermarket tach I've used. Worked on the 5 channel Innovate wide band recorder I used. That one did need a variable resistor to have it's rpm equal actual rpm.

This logger the guy felt an HEI would not work on but he said not many folks trying one. Initially tried and Autometer 9116 tach filter -no signal at all. Dropped it off and used straight tach signal. It goes from actual rpm to almost double real rpm. So all over the place. Not sure unless sampling rate is the issue why this unit has problems with the interference. Tach feed for the Autometer tach is working fine..

Options I see 1)trying Autometer tach adapter 9117(his suggestion) but it wires on coil + supply side
2)HEI remote coil setup
3)crank trigger.

Crank trigger wheel is 3/8" thick so would space out water pump and then alternator to match up, so some fabricating. I have a ATI balancer(3 bolt Chevy pattern) and I think they make crank trigger outer rings or new balancers.

Any thoughts out there?

https://www.diyautotune.com/shop/sen...rigger-wheels/
Some trigger wheels here, and sensors. I believe some members here have bolted these to the back side of their balancers. But they are only 1/8" thick, if that helps. Will your datalogger take a vr, or hall effect input?

I think it will take those inputs.
I an still using the AC pulley as a spacer for other pulleys and it probably 1/8" thick. I did pick up a wheel years ago from a guy here when I was looking at EFI. Wonder how those wheels hold up to rpm and SFI if the tech guys look hard?

Another option is to use a MSD digital-6 box( I picked up 2 new ones over the years) and convert the HEI just to a trigger.

I think as long as pulleys don't have to be sfi rated you'll be ok.(But if NHRA thinks about it, they'd probably do something silly)And the guys at DIY claimed to have tested the wheels to 18000 rpms. I don't think there's any safety concern as long as you have it bored concentric. If you have the MSD option, and you're not gonna do efi, that may be easier.

The wheel I have is a 36-1 that can bolt to the back of the balancer. Ollie here had them back about 8 years ago.

I use one of those, but between the crank pulley and the balancer. I wasn't crazy about drilling and tapping my SFI balancer. I figured that would cause issues with tech potentially, modifying the item that was certified. I will say it's the most stable timing signal I've ever had.

Since I use the A/C pulley for a spacer it might work there thickness should be close. Not sure if it has the 3 bolt Chevy pattern holes.

A good machine shop can bore it and put the bolt pattern in it where it will run true and fit right.

Randy at RPM is pretty sharp. If he thinks the Autometer 9117 tach adapter might work, I'd try that first.

Eric

Thanks Eric. An adapter would be easier than a whole redesign of pulleys and ignition system.

Here is the install sheet on the adapter I assume splicing in the large + feed to the HEI coil.
https://www.autometer.com/media/manual/2650-561X.pdf

Looks like you would splice into the red wire to the HEI coil? Picture in the link below:

https://www.crankshaftcoalition.com/...enter_term.jpg

Eric

That is what I was thinking. Just get a couple of Packard terminals and an extra section of wire.

Wired it up this weekend and worked like a champ! I don't understand why it needed it but heck it works. I was a little concerned the big 10ga factory positive lead going to probably a 16ga wire in the unit but the actual wire in the cap to the coil is pretty small also.

So for you guys trying to run an HEI with an EFI computer and getting dirty signals this might be the ticket.

surprised your not using a crank trigger -- the timing is rock steady with those things vs the jumping around you see with a dist. set up -- just fyi

That is on the list for the future! Since my ATI balancer has 3 bolt Chevy pattern MSD has a BBC one I could use. Just not sure with the choices of teeth which to use?? 32 or I think other option is 60 something. Just need to get some decent passes on the car as a baseline like when we took it off the dyno. I do have a MSD distributor just to use just as a trigger vs the HEI also.

I really think the convertor is why it is not going as fast as it should but it was not built for this motor but builder said it should work. I think it is too tight. Have some new slicks 28x10.5 also to take the DOT traction out as a variable too then tune for the DOTs.

Here is the Chevy one. 60-2 tooth.
https://www.holley.com/products/igni.../parts/556-109