aztoyman

I have done a ton of searching and have found mixed results regarding the tach mod for a 22RE. Some say it worked, others say it didn't.

I understand the V6 sends different pulses than the 4 cyl and the tach won't read. Which mine doesn't. (85 22RE SR5 Cluster) It did work before the swap.

So why do the 3.0 to 3.4 swap guys have to do the tach mod when they already have a V6?

I see they use the 10K ohm resister for the 3.0 mod. Why would I use the same resister for a 22RE? Wouldn't it need to be a different value?

Can someone that has successfully done the tach mod on an early 22RE cluster please post up what they did?

Most of the 22RE threads I found showed the later 89 up clusters with an adjustable pot.

Would I be better off selling my 85 cluster and getting one from an 88 3.0 before I start tearing into mine.

aztoyman

OK, I guess people are tired of the tach mod questions. I did search. I found two types with two different locations to solder the resister in. Neither look like my tach.

I did find my tach on a PBB thread where a 5K ohm trim pot gets soldered in instead of the resister. Unless someone knows where to solder in a resister on my style tach.

Here is my 85 SR5 cluster.



The thread on PBB had some people claim to have this style cluster and all they had to do was adjust the little white pot already on the tach and it worked on their 95 and up. I tried it and it did not work. It has a range of about 1/2 turn. All I got was the needle to move to about 200 RPM max.

Here's my tach




Here's the small pot I tried to adjust.



I put the stripped down cluster in the truck enough to plug in the connectors. I left the other gauges out so I had room to adjust the pot with a small screwdriver.



Radio Shack didn't have the trim pot I needed per the PBB thread. I will try to find one on line. The PBB thread was for a Chevy V6 so I hope it works the same.

I'll post up what I find. Anybody got any other ideas?

wyoming9

iTrader: (1)

I can understand your wanting to get this figured out I think .

I am sort of right behind you so to speak 86 22RTEC vehicle .

Now I also have the 92 4Runner 3.4 swap but have no idea if any changes were made to the tach which is the V6 SR5 cluster which works so I can`t say if just swapping clusters would work in your case.

When it got to the point I don`t know if a aftermarket tach would work I can`t see why not .

As I will be going with oil pressure and temp gauges.

wyoming9

iTrader: (1)

Are the 3.0 Clusters plug and play or does one end up repining the connectors.

I think I have the same cluster in my 86 Nope mine says 722 not 721

Ever get this figured out??

Your pictures are great now I know why I don`t take them mine are really bad!!

aztoyman

I don't know if 3.0 cluster is plug and play. I may find out if I don't get mine working.

Still waiting for a trim pot that I ordered. I will definitely post up whatever I end up doing.

Gsolo

The difference is the 3.4 doesn't use one ignition coil, it uses 3 or 6(depends on year of 3.4). The tach signal is a different waveform, which is where the added resistor changes the waveform seen in the tachometer. Your adjustable pot is to adjust setting from 4cylinder to 6cylinder. I hope that helps you understand the why...I"m sorry I'm not familiar enough with your cluster to help with the how

aztoyman

Thanks for the info Gsolo. I couldn't understand why a V6 to V6 swap needed a resistor.

I got my trim pot in the mail. I'll post up if it works once I get the time to do it.

aztoyman

OK...... It didn't work but I'm going to post up what I did anyway because this is SUPPOSED to work at least for Chevy V6 swaps. I found this info on PBB.

I couldn't find the correct trim pot locally so I ordered ONE (I thought) from Amazon for a few bucks. I got 25 of those suckers in a bag.

I needed to find a way to mount it and still be able to access the adjustment screw. Here's how I did it.

Soldered a couple wires to the trim pot and to the appropriate points on the board per the write up on PBB. Here's a link. www.mindspring.com/~jayk3/toyota/tachmod.htm





Remove this plastic bar for access and install the screws in the back to hold the tach in place.



Stick the clear plastic cover on and get a feel for where the screwdriver will go. The plastic cover and face plate held the trim pot in place. It was just soldered to wires and not secured otherwise.




Stick the faceplate and needle on, leave the speedo out for access and plug the dash in. Start the truck and adjust the screw to get your tach working. IF it's a Chevy V6!

THIS DID NOT WORK FOR MY 3.4 TOYOTA! This was on a 1985 SR5 Cluster.



Guess I'm looking for an 88 V6 cluster or paying the $90 to Dakota Digital for an adapter.

I'm done messing with it at this point and my priorities are elsewhere.

wyoming9

iTrader: (1)

i am sorry it did not fix the problem

i have not looked into after market Tachs yet but I wonder what they do to see the signal.

6840

you might try a Dakota Digital tach converter. Mine is pulling a signal from the alternator to drive the FZJ80 tach. I suspect that you could just pull the signal from one of the coils on your motor, and then use the DD to calibrate (multiply by 6) and get pretty darn close

aztoyman

Thanks 6840. The Dakota Digital adapter seems to be my only option at this point.


I tried to find a cluster from an 88 with the 3.0. Posted up on CL and got one reply. The guy wanted $150 for a damaged one.

I can get the DD adapter for about $90. Just haven't done it yet because I have been enjoying the heck out of my truck and its not a priority right now.

I would like to get it working one of these days. If anybody has a 3.0 tach for cheap let me know. Otherwise it will be the Dakota Digital.

I'll post up if I get it working.

92yota92

Found your post while researching my own issue so hopefully I'm not to late to help.

First it depends on what 3.4L you'll have twin 3 or 6 coil then you need to adjust the resistance value of your tach accordingly, what resistor was in there when you first opened it up? say it's a 10k, in a twin coil 3.4 into a 3.0l cluster you would parralel that effectivly cutting it in half the resistance and doubleing your voltage that's why that works in that situation.

If you're a 4 cyl tach (4 pulses per rev 2 revs if no waist spark) and say you're runing a 6 coil 3.4l that'll generate 1/4 the pulses (1 pulse per 2 revs on a coil per cylender setup) you can also get that signal from the injectors I belive. In this case you need to reduce you're resistor (say 10k for simplicity sake) by 4 (6 for a v6 tach) to 1.67k and 2.5k repsectivly, at this points it's simpler to jsut replace the resistor rather than try to parralel it to attain the required reduction, a potentionomiter will also achieve this but is more likely to fail over time or move out of adjustment.

If a 3 coil setup multiply accordingly.

I forgot to mention, analog tachs are basically just frequency to voltage generators so this all has to be done AFTER the conversion, a resistor or pot placed ahead of the converter will do nothing.

So a 4 cyl tach (2 pulse per rev or 2 per 4) with a 2 coil 3.4l (3/2 pulses per rev or (6/2) per 2) would need a reduction of .75 that means a 5k resistor PARRALELED with a 10k or a 7.5k resistor replacing a 10k.

I have a situation where I'm swaping a motor with a coil over plug setup in essence a 1 pulse per 4 revs signal from any 1 coil or any 1 injector and a stock 3l v6 tach, I'll reduce the resistor on board by a factor of 6 thuse multiplying the post frequency to voltage converter volage by 6 so a 10k resistor will need a 1.67k resistor.

That should do the trick.

edit*

Another thing to note, if you're 3.4L is a 6 coil and likely quite modern it's likely not running an analog tach, the tach is being fed a digital signal from the ECU that signal will not comunicate anything to your analog tach, you'll need to pull the signal from a coil or an injector (being sure not to use the high voltage wire that'll fry something) then connecting that at your body harness for the tach feed.

aztoyman

92yota92, You're not too late. I have just been running without a tach. If you can show me or tell me details how to make this work I'm all ears.


My truck and tach is originally a 4 cyl 22RE. My donor engine, ECU and wiring is from a 99 4Runner. Has a coil on each plug. I still have the gauge cluster from it. I couldn't adapt the tach into my old style dash.


I figured the Dakota Digital was my only option. Just haven't done it yet.

92yota92

If you have your tach loose then take a look at the circut board and find the resitor you're suposed to parralel or replace, it should be located after the frequency to voltage converter in the circut somwhere, get the resistance rating.

The tach is a simple frequency to voltage converter, it takes a pulse and makes a voltage value out of that frequency, the coil then tightens and loosens depending on the amount of voltage going through it moving the needle, if yours isnt moving at all with the tach wire connected to the body harness in the right spot then it's not an analog signal or it's not the right wire, hooked up you should be reading a value 1/4 of what you should be geting.

Next is the maths. in you're case a single coil on 4 cylinders = 2 pulses per rev for the cluster (a coil fires every 4 strokes so once per 2 revs/4 = 2) the coil per plug will be 1 per 2 revs so you need to reduce you're resistance by 4 in order to multiply your voltage by 4 (a 10k resister would need to be replaced by a 2.5k resistor) that should get it to read correctly provided your drawing your tach singal from the correct spot, this I can't help you with I don't know much about the 3.4l.

I imagine they were analog up in to the late 90's then witched to digital when the ignition becomes computer controlled (coil over plug). A digital tach signal is not going to help you turn that old cluster it needs to be analog.

There are some options here, I'm wokring on figuring out where I can take an analog signal from an entirely digital engine right now.

aztoyman

Damn dude, you need to change your user name to Einstein. Thanks for the info. I'm not sure if your telling me I can make this work or not.


It is wired correctly. I don't remember if the tach jumped a tiny bit when I start the engine. I haven't driven it in a while. But, the tach doesn't read at all. Not too high or too low. Even with the resister and trim pot mods attempted. I "THINK" it comes a hair off zero. I don't remember. I can't look at it right now, it's at my daughter's house while we build my sons truck.


Can you tell by the pics I posted of my tach if I can pull this off? Maybe I just need to start getting serious about finding a 3.0 cluster for my 88 and do the resister mod.


Thanks for the help!

92yota92

I can't seem to see the pics when I'm at work but I'll check when I get home, if you're getting nothing I'm guessing you're trying to hook a digital tach signal up to it. there's nothing you can do to make that work short of a DAC module but that's out of my bag of tricks, my guess is you'll need an analog signal from some other source and depending on that frequency that'll dictate the risistance rating you need.

If you rev the piss out of it and are getting a tiny bit of movement then I'll guess you've been doing it backwards somehow increasing the resistance thus lowering the voltage.

A quick electrical lesson, resistors wired in parral reduce resistance, take the resitance total average it then devide it by the number of resistors in parallel to get a resistance value so 10k + 10k parralel = 5k. resistors wired in series increase the resistance so 10k + 10k in series = 20k
10k + 20k parrlel = 15k
10k + 10k + 10k parralel = 3 & 1/3k
and so on

take 6v after a 10k resistor and reduce the resistance to 5k you'll then have 12v current being a constant, this is all simplified but that's the jist of it. That would be how an earlier model twin coil mod would work v6 to v6.

irab88

iTrader: (4)

try again

Rt = 1 / ( (1/R1) + (1/R2) + (1/R3) + ... + (1/R_) )

your statement only works if all the resistors are the same value. the total resistance is ALWAYS less than any individual resistor.

92yota92

fair enough, I'm no electrical engineer and would just replace the resistor with the corrected value required.

irab88

iTrader: (4)

ha, yep. it's all good.

honestly, i'm not even going to try to get my factory dash to work. i'm going to use the obd2 port and a cheap android tablet (with the torque app) as a dashboard.

92yota92

I've got the torque app but I don't want a dead needle staring me in the face, I would atleast turn it into a clock if I were to run an after market tach somewhere else that is.