Driving 97 kick tach after J18A engine swap

[fixkick]

So, a little update.

I know it has been a while, but between my father being called on a repair and leaving the country and the j18 blowing a head gasket and university starting it has all been a little overwhelming for me.

My old man fixed the bearings, started it up, the thermostat had stuck closed, by the time he shut it off it had already overheated (we suppose) so it started blowing bubbles inside the coolant. My dad works as a ship mechanic, and he got called on a repair trip, so he left it for me to fix. Being my first time tearing apart an engine by myself, I was a little bit intimidated.

Anyway, I pulled the head off. Took it to a machinist and he said he had to take of 0.06mm off to make it level. It had warped between cyl 2 and 3. The black soot on the top of the cylinder liner where the head gasket should seal confirmed my suspicion that cyl2 was the culprit. After I got it back from the machinist, I put on some new valve seals and polished the valves. I managed to get it back together, with the exception of the valve cover and accessory belt which I didn't have time to install, since I had to go back to university. I hope that I can get it started this weekend.

In the meantime I started to do some research on my project car which is a MK2 Golf GTI in which I will be putting a 16V engine from a MK3 running Speeduino engine management (and turbocharging it down the road). This is off the topic, but I'll get to the point, I promise.
so this means engine swap MK2 into your J18 sport ?

I started doing research on how I'm going to drive my stock MK2 Golf tach when I get rid of the dizzy and go COP.  (the j8 has no dizzy but yes cop)
so you must  be talking about Mk2  but what harness what ECU what, parts all are from MK2 moved to J18, not sure me.
2cops or 4?
Then I came across this:  https://www.msextra.com/forums/viewtopic...31&t=40365
this MS post ignore the nasty backemf pulse from the coil (relay) that can blow up many TACHO heads, the suzuki used huge voltage divider and clamp diode to protect the TACHO and the ECU also monitors this same wire and so does the cruise module all 3 can blow up with any huge BACKUP spike and is NOT NEEDED at all to make a tach run, my guess is his problem is polarity not EFI spikes . BACK EFI is not good, to silicon, so is suppressed carefully.

ever car made uses there own tach designs , when the makers when to DIS Ignition with 4 cops,  no tach like to work with COPS. (generic tach)
The tach just  counts the spark pulses and does the math for 4 cycle and 4 cylinders.
The ECU has and out pin that is tacho, and no 2 cars made use  the same way or single here, some its serial data like my JK jeep has (CAN BUS)
if lucky the Mk2 golf service manual tells this at all. some just show a wire and say tach sig here, no format told.
for example it might send out 4 times spark pulses or with  cop  cards (shared wasted spark ) must convert that mess to normal 1 pulse per crank turn
the cluster engineer and the EFI engineer have lunch together and decide all this,  the cluster guy says we have a cluster PCB from 10 cars now all the same so tells the EFI guy here is my correct signal,  that is how this happens using internal standard parts at a car company.


From my understanding it is just a transistor switched by the PWM tach output of the ECU which then applies and cuts power to the inductor, producing the high voltage that the tach wants to see. this is true
I also read that some tachs built for reading off the coil negative also work with simple 12V square wave.

I also came across this video. The guy uses the coil inside the relay to create the high voltage kickback that the tach needs to read: https://www.youtube.com/watch?v=ySmWk_5G...immyLundin


why not just make 12vdc signal,  no coil, no back EMF.,  replace the coil with say 100 ohm resistor there and same transistors. see if that works first.
never make true HV for fun,  12vdc is LV , 400v BACK EMF is nOT NEEDEd,