Gen4 3sgte into MKII na Tach signal

[PaulWoods]

Would anyone really do any of the other options if my method of bridging one resistor works though?

I could be wrong, the Gen4 3s-gte might be using some unknown tach witchcraft signal from the ECU, but i'm fairly confident it should work.

[Protok]

Would anyone really do any of the other options if my method of bridging one resistor works though?

I genuinely would not have thought so but beams have been getting converted into the AE86 for about 10 years now and I've never even seen a hint of this. People always use the MSD box, aftermarket tacho or a signal from new ecu.

[sinjen]

I did ask Prime about the resistor method as I'd heard rumours about it from other engines conversions, this is what Justin said..

"We actually do the much simpler thing and use MSD tach adapters. Takes much less time and works every time. Its the MSD 8920."

I think I got mine for £40 and it literally takes 10 minutes to wire up, it is very good. But if your method does work Paul, I think it would be preferable.
As Red says, information on the resistor method is so scarce, most just accept that the MSD or tach swap is the way to go.

[PaulWoods]

I'd have to disagree with him that the MSD is easier.... that tacho mod takes literally 1 minute to solder a wire across it, ok you have to take the clocks out but there isn't an Mr2 owner among us that can't do that in minutes.

It's also free, so no need to spend £40 on a box and wire that up, so i don't see how the MSD is better?

IF it works of course, i guess if it does work then i'm the one with the big swinging dick, if it doesn't work then the Gen4 ECU must have an odd tach signal we've not seen before.

I still think my mod will work though.

[sachadesousa]

Ok thanks Paul. Works on na mr2 Tach. Found the cut wire in the fuse box that went to the igniter (black) extended it to c27 pin on the ecu, and pulled and jumped the resistor you mentioned earlier.. just gotta do the obd2 thing to confirm its accurate. Although it does look right. Thanks again Paul!

[PaulWoods]

Paul Woods 1 the rest of the internet 0

[sinjen]

Awesome, glad it works, haven't got round to trying it myself but more reason to do so now. Gets rid of the annoying buzz from the back

[PaulWoods]

I guess Prime will need to take a long hard look at the £40 pricetag for the MSD when my mod is free.

You watch though, i guarantee this info will pop up somewhere else as somebody elses idea, we rarely get credited for our discoveries.

[sachadesousa]

Also hooked up the obd2 method which works as well thanks everyone!

[sinjen]

I've done exactly as above but mine won't work. C27 to the tach, pulled the resistor out and soldered in some wire instead, checked and rechecked and it won't work, any ideas?

[PaulWoods]

Odd.... PM sent, double check continuity from C27 to your black wire on the cluster, and check your soldered joints.

[sinjen]

Thanks Paul, PM replied to. All continuity checked good

[sinjen]

Just thought I'd update this..

So, I found that bridging the resistor with a wire blew my gauge, probably a capacitor/transistor thingamajig!
Did a bit of research on converting the signal. From what I can tell the gen2/3 3S uses a 20-40V igniter signal and the Gen4 uses a 5-12V Ecu signal, so keeping the current constant but increasing the ECU voltage to a tach recognisable voltage aka 20-40V I tried a 10k ohm resistor on a new gauge and it works, happy boy which means I can now ditch the noisy MSD unit

Thanks to Paul Woods for his help

[PaulWoods]

Well done on working it out, i use a 10k resistor in that spot on coil based V6 tach signals, but always used a link wire on ECU based signals, it seems yours has needed the former for some reason..... main thing is it works