Hi all, as the title says.

I’ve been very happy with his tach adapt box driving my OEM distributor from my 6 cyl corvair engine. I am now replacing my carbs with fuel injection and ‘wasted spark’ ignition. So I will now have twice as many ignition signals as at present. So I think I need to change the dip switches - or maybe the tach adapt won’t be able to step down 6 cyl x 2 firings per rev per plug = ‘effectively’ 12 cylinder driving OEM 4 cyl tach.

Any contact details for Bob, or solutions from those who have faced this issue, most appreciated.

Thanks

DaveO

AshlockTech
1218 N. Lemon St.
Fullerton, CA 92831
Bob@AshlockTech.com
1-714-651-1631

I just bought one... will check the mini- manual later today to see if it can be converted from 12.

I do think you are overthinking this, as I don't think it matters, most systems ECU's have a tach output that doesn't count the wasted spark event. If you have two coil packs (twin plug), each with it's own tach output, just use the signal from one coil pack, that said if you do have an ECU tach output that is the one I'd use. You would never use every tach output by splicing them all together.

My '67 bug with SDS efi has wasted spark and it doesn't have any issue. This system has two tach outputs one on the ECU and the other on the coilpack, I've only ever used the ECU output. I have also had this system in my 914 on 3 different engines before putting it into my bug.

On my 3.0 SC engine I'm installing EFI with twin plug wasted spark and I've seen no info re tach issues, in fact I don't expect any as the 2nd set of coils just use a simple splitter to run the 2nd coil set.
Again I will be using the tach output from the ECU, not the coils.
Note the the coils I use are the same GM coils that TEC (and CE) systems use.

I agree with Mark (although my experience is much more limited). I'm running Microsquirt with wasted spark. I did need to run my tach output from the ECU through a tach adapt (generously provided by Dion here), but it works like a champ.

What FI system are you going to use?

Was this for a problem with the tach signal or 4 to /6 conversion?

My 914 /4 with SDS and wasted spark had no tach issues.
My 914/6 conversion with a 911/6 tach and MSD CDI the tach didn't work, I had to use a Tach-adapt.

Mark, I think it's an issue with the tach signal from Microsquirt, although I can't remember the detailed "why." It wasn't a 6 conversion.

It's to do with the sine wave, kettering vs the modern type... which the name escapes me right at the brain fart moment.

Thanks everyone. Yes I was overthinking things. I have now found that the number of tach signal outputs is three per crank rev - same as my with-distributor non-wasted spark set up. So there should be no problems at all.

I am using SDS EFI 5F system.

Cheers all

Dave

I think I was thinking of my SDS EM5-F six cylinder ECU which has the ECU tach wire installed as an option, for your system use the green wire that's located on the coil pack. If you have twin plug with coil packs X2 use the green wire from just one of the coil packs.

Feel free to drop me a line if you have questions about your EM5 install.

The non-detailed why is that the output from MS is a weaker pulse than the signal you get straight off the coil.

There is a pretty easy mod you can make to the tach itself to make it compatible with modern tach signals (MS) without an adaptor but does require opening up the tach. Internally on the pulse input circuit one of the first things you encounter is a fairly large resistor. Installing a jumper across this resistor is all that is needed to make the tach compatible with the MS output. There is a secondary mod you can also do while you are in there that involves installing a capacitor (dont recall the value off the top of my head) across the tachs coil windings. This slightly dampens the tachs response and eliminates the 914 tach bounce.

I am headed the Microsquirt route, so subscribing for the tach details.

Thanks,