4G swap in a 3000gt?

[familyMAN]

Any ideas on how to get my tach to read correctly? AEM is correct. Do I just need to swap in a DSM tach? Anybody compare the connections before?

Bump Tach isn't playing nice with 4cyl and is only showing 2/3 rpm. 5k on tach is 7500 on AEM. If DSM tach is the same size and connections (good chance) I'll swap one in, but figured there could be some smart electronics guys in here that could help get my 3000 tach to work.

[sergechronos]

You could try sending a PM to bradrs. He does a lot of electrical stuff with DSMs, he might have some input or information.

[donniekak]

Looking at the diagrams it makes sense. The tach signal comes from both, (or all 3), power transistors. The 3s tach is missing 1/3 of the frequency it expects for any given rpm. Maybe a frequency multiplier, or swapping in a dsm tach module is the answer. Or, since you may need it anyway, an aftermarket 10k tach.

[familyMAN]

I should just find a DSM tach and start staring at it for a couple hours. That's how the engine ended up in my car.

9k is fine and my 3S tach goes to 9. Was really hoping to use it and peg it! I guess I could just remark my tach. 9k remarked to 13,500 rpm. That'll do

Picking up cam seals and galant GS timing belt from NAPA on Friday.

Can't wait to get this housing move done so I can start buying big boy parts this fall.

[bradrs]

The tach signal is generated in the PTU, 1 pulse per coil firing.And the 3S and DSM PTU are designed the same in this regard. So the 3S tach expects to see 3 pulses per rev, but the DSM only puts out 2. That is your 2/3 ratio you are seeing.

A POSSIBLE fix could involve adjusting your AEM. Normally the PTU feeds the signal to the ECU, and to the dash. So the AEM treats that as an input. But you can change that wire to an output in the AEM, and have it control the tach instead.

There are 2 issues with this. First is that I don't use an AEM and don't recall if their tach output allows to you scale the tach ratio. Second is that you will need to disconnect that wire from the PTU, so it isn't feeding additional pulses onto the wire and messing everything up.

[familyMAN]

I'm sure I have outputs available but I'll have to research to see if I can configure as a tach output.

AEM rpm displayed is correct so at least it's something to start with.

I could always go baller with a MXL digital dash! (Not likely)

[bradrs]

You aren't having to reconfigure a new output, or add wiring. You are reconfiguring the existing tach input, already wired in to the tach etc, to be an an output inside the AEM.

The ATDSM site explains it in their COP setup info. Ignore all the parts pertaining to wiring the COP, and the CDI(which is 90% of it), and just look at the EMS settings for the tach:

http://atdsm.com/pdf/COP.pdf

[james92tsi]

I don't have a DSM anymore so can't help with the physical aspects of its tach/cluster.

I do have a 3S gauge cluster taken apart on my kitchen table right now for various mods. Can get you pics of the tach connections etc if it would be helpful.

Electrical volume of the FSM for both cars would be the best way to track down if the connections are the same and determine feasibility of a tach swap. mitsubishilinks.com should have both manuals for the specific years in question.

These guys are right on about the 2/3 ratio. Your DSM PTU makes 2 pulses per rev on the white wire where the 3/S tach expects 3 per rev.

[familyMAN]

You aren't having to reconfigure a new output, or add wiring. You are reconfiguring the existing tach input, already wired in to the tach etc, to be an an output inside the AEM.

The ATDSM site explains it in their COP setup info. Ignore all the parts pertaining to wiring the COP, and the CDI(which is 90% of it), and just look at the EMS settings for the tach:

http://atdsm.com/pdf/COP.pdf

Thanks. I understand now. Only thing I don't understand is that the AEM is no longer receiving an rpm input but I guess it doesn't matter if it's calculating/generating its own.

[familyMAN]

I don't have a DSM anymore so can't help with the physical aspects of its tach/cluster.

I do have a 3S gauge cluster taken apart on my kitchen table right now for various mods. Can get you pics of the tach connections etc if it would be helpful.

Electrical volume of the FSM for both cars would be the best way to track down if the connections are the same and determine feasibility of a tach swap. mitsubishilinks.com should have both manuals for the specific years in question.

These guys are right on about the 2/3 ratio. Your DSM PTU makes 2 pulses per rev on the white wire where the 3/S tach expects 3 per rev.

Pictures couldn't hurt anything if you don't mind. Going to try beads suggestion first and then play with the settings to see if I can scale it.

I get the 2/3 reasoning. Guess I didn't state that. Pretty simple to understand that 4cyl vs 6cyl simplifies to 2/3