Tach on an EFI engine

[greg0187]

I finished installing the Tach today from its temporary connections. I found what I believe is the best place. All the connections can be made to the harness that plugs into the instrument cluster behind the dash. Although it requires a little extra effort to get the cluster out, you don't have wires running all over the place, plus I only used 12 inches of wire from the tach. Let me know if anyone needs any specific instructions for removing the cluster. Color codes for connections are as follows.

Ignition ON - Light Green
Ground - Light Blue
Illumination - Red w/Blue stripe
Tach Signal - Red w/Yellow stripe (Same at ECU)

-Greg

[greg0187]

OK. Here's the deal. The tach says that idle speed is 1100-1200 RPM at the 3 cylinder setting. There's no way the motor is turning this at idle, I don't want to sound like a dumb *** but i've worked on enough motors to know. I've read... that some tachs have a calibration adjustment but this one doesn't have one (Accessible anyway). I'm quite sure that I connected to the correct tach signal because it goes to the instrument cluster and there's not even a contact on the circuit board. My guess is that its the inaccuaracy of the tach itself. It has a 10 switch dip switch bank to set the number of cylinders. I tried some different settings and found that the #3 dip switch and the #4 dip switch turned to the on position showed 850 RPM at idle which is what I believe is close to what it should be at. This setting is not in the documentation that came with the tach so my guess is that it could be used to calibrate it???? It didn't seem to change the full range RPM indication except for the initial 300RPM. I just though I'd let you guys (Milt) know.

-Greg

[Mighty Milt]

beneath the driver's seat decklid i found a sticker... i couldn't get a picture of it because of the glare off a metallic sticker but it has the engine specs.

one of them (keep in mind it's japanese) is 900... i'm assuming that's the idle rpm, i've seen enough of these stickers to guess what each number means. there is also a setting for the intake and exhaust valves and the air conditioning 134a and what the emissions readings should be.

thanks for the heads up greg, i'll keep that in mind when and if i get a tach. sometimes it's better not knowing. today on my ride home when the a/c died, i had a lot more power to hammer down... i had the speedo needle burried. i was somewhere between 145 & 150 and don't want to know what rpm i was turning... it sounded good though.

[greg0187]

A/C is nice to have but sometimes I'm glad that I don't have the "Rob Horspower" button on the dash. The most desirable reason to have it is for defogging the windscreen, one thing I didn't think about when I got mine. Thanks for the RPM indication. From what I've seen..the RPM changes based on the electrical load on my engine. With the headlights or parking lights on the RPM increases by 100. Thats why I figured about 850.

-Greg

[Mighty Milt]

here in arizona a/c isn't for comfort, it's for survival

[barneyrb]

I have to ask, what RPM is the tach reading at 45mph or around 70kph?
Thanks

[greg0187]

I have to ask, what RPM is the tach reading at 45mph or around 70kph?
Thanks

I assume you want the reading when the needle is @70kph. I have 25" tires so my speedo is off, but I don't think it matters, I'm just not actually traveling that speed. Someone correct me if I'm wrong??? I don't drive mine on the street here at my house but next weekend when I take her to the country I will see.

-Greg

[Mighty Milt]

you are right greg, rpm vs. speedometer is the same relationship regardless of the tire size.

[235bill]

I installed a inductive digital tach. from Northern tool it took a little fooling around to get it to work properly but display will go blank if it is in direct sunlight or some other heat source, this makes the hour meter usless as it returns to zero when readout goes blank but all I was interested in was RPM anyway, @100K it reads 3250 RPM.

[greg0187]

Cool. On my EFI engine I couldn't find a way to install an inductive tach. I tried to take some readings this weekend and at one mental note, at ~60kph it was reading ~2400RPM.

[Mighty Milt]

grreg,

in what gear adn in what range? sounds high if it's in 5th?

[greg0187]

greg,

in what gear adn in what range? sounds high if it's in 5th?

Thats High range 5th gear.

[235bill]

I was thinking, if there are individual spark coils, why not use a 1 cyl tach?

Any tach with inductive pickup will work no matter how many cyls because you only register the number of pulses (RPM) on the cylinder the pickup is on. If pickup is on coil lead it will register once for each spark on a three cyl. you will have three pulses for each rev. Just checked RPM @60K -(38mph) it is 2000 rpm

[myhijet]

Any tach with inductive pickup will work no matter how many cyls because you only register the number of pulses (RPM) on the cylinder the pickup is on. If pickup is on coil lead it will register once for each spark on a three cyl. you will have three pulses for each rev. Just checked RPM @60K -(38mph) it is 2000 rpm

With the 3 coil setup the twin cam has, there is no plug wire but the pos and neg wires are accessable on the coil. The coils set directly on top of the plug which goes through the valve cover.

[greg0187]

Just an update to this post...

I was working with another member with a newer model truck to get his tach working and he found that the tach signal wire (Red w/yellow stripe at the ECU) was actually taped into the harness behind the instument cluster rather than terminating at the connector to the cluster like mine was. Sorry for the confusion.

-Greg