Changing a 4 cylinder tacho

[V8Celica]

Does anyone know how to get a 4 cylinder tacho to read properly when its being feed from a V8. I'm only using one coil now.

 

[sideshow]

a 1uz reads accurately on a 4cyl tacho

the pulse comes out from one ignitor only so its a 4cyl signal

but i sell devices to adjust the signal needed

is the tacho reading twice as fast or half speed

 

[V8Celica]

I haven't hooked my tacho up yet but as I'm now running only one coil and one dizzy I assume it will read double actual revs.
How much is your signal adjuster

 

[hi-lex]

hey sideshow do you do one to make a diesel tach work on a 1uz?

 

[sideshow]

yer i have the device but u have to adjust it yrself

unless u can tell me what signal the diesel tacho reads eg at 1000 engine rpm what does the tacho read

these devices just alter the pulses they do not make the signal stronger or weaker

 

[svpmx83]

http://www.mindspring.com/~jayk3/toyota/tachmod.htm

and if you are lucky youre tach may already be adjustable from factory


As it turned out the Toyota Tach from about 1990 onwards is adjustable. Remove the temp guage and reinstall the instrument cluster while having an accurate tach connected to the ig point in the check connector. A simple twiddle of the white trimpot circled in green on the second picture at several different rev points will get your tach reading correctly again

 

[Peewee]

My 1986 Cressida was identical to the above.

I tried adjusting it myself, but I couldn't get it accurate enough.

Its not easy to hold a motor at 4000rpm, looking at the laptop display, holding the dash in one hand, and adjusting the screw with the other. Especially since a 1/4 turn is enough to change from 4cyl input to 8cyl input.

Ended up getting it professionally calibrated, cost me $30.

 

[hi-lex]

the adjustment on hilux dash only fine tunes it, it doesnt vary it that much