Beretta.net

So...

I have my 1988 Beretta GT. Its been upgraded to the 3.1L v6 from the 2.8L
Its also a 5 SPD.

I have reason to believe the tachometer is reading incorrectly.

Example: I hold engine at 4K RPM, the tach reads higher like 4.6K, I hold engine at 5K RPM it reads like 7K.
(Using the ECM reader on the OBD 1 Port)
Before the conversion to the larger engine, the OBD1 reader showed the analog tach was the same.

Does anyone know of any aftermarket Tach's that read correctly?

I'm building this thing for racing on top of regular driving, and I'd like to have a good tachometer because I want to know how high I can rev it...
I've tried finding the correct cluster, but There are no Beretta's in the junk yards anymore, and the aftermarket tach would just be easier...

EDIT:
I also want to put it in front of the old tach, mounted on the steering column like the INDY pace car has in the photos

Any aftermarket tach will read correctly if you have it set for 6 cylinder... If you don't have it set on the proper cylinders then no it wont read right.

There should be absolutely no difference with the engine size change... the 2.8 and 3.1 are IDENTICAL in every way except for the crank, the stroke is longer. But all the electronics including the ignition are all the same so something happened during your swap to screw up the tach in some way.

3X00-Modified wrote:Any aftermarket tach will read correctly if you have it set for 6 cylinder... If you don't have it set on the proper cylinders then no it wont read right.

There should be absolutely no difference with the engine size change... the 2.8 and 3.1 are IDENTICAL in every way except for the crank, the stroke is longer. But all the electronics including the ignition are all the same so something happened during your swap to screw up the tach in some way.

All I did was install the 3.1L v6 and use the 3.1Lv6 sensors it already had.
Then install the stage 2 racing chip.
Aside from exhaust and intake mods, thats all I really touched.
Oh and I did the clutch.

I figured I'd ask because its not synced up and it used to be fine.

Does the tach get it's signal from the alternator by chance?

I'm pretty sure you gasser guys don't, but the 6.2/6.5 diesels get their tach signal from the alternator and pulley size can cause the tachometer to read off slightly.

The older clusters to my knowledge should receive a tach signal from the ICM just as the pre 96 cars do... Only the OBDII ones get the tach signal from the ECM.

3X00-Modified wrote:The older clusters to my knowledge should receive a tach signal from the ICM

ja.

it really wouldn't surprise me if the tach is out of calibration. the 89-93 grand prix UB3 clusters are notoriously bad for having both the tach and speedometer calibration resistors fail in every way possible. display too high, too low, nothing at all.... all kinds of fun. i even had one in my hands that seemed to have some kind of unintended low-pass filter on it's speedo circuit..... displayed speeds up to ~51MPH perfectly, then from about 51-55, it stuck at 51, then at speeds above that, it just dopped to 0.

if i had to guess, i'd say the beretta clusters use a similar circuit and could be recalibrated much in the same way, but i would need pics/a unit in my hands to be certain. generally, they'll be off by a consistent percentage throughout their entire range. if the error % changes throughout the range, then there isn't much that can be done..... the drive circuits on the GP clusters are quite weak(low current) and are effected by gravity to a pretty extreme degree. tilt a functioning cluster backwards 30* and the speedometer may jump 5MPH from where it was. considering the era, it wouldn't surprise me if the circuits are setup nearly identical to the clusters i'm referencing.

You could have the cluster rebuilt if its in need of a recali and some bulbs. Last one I sent out was about 100 shipped to and back.

1988GTU wrote:You could have the cluster rebuilt if its in need of a recali and some bulbs. Last one I sent out was about 100 shipped to and back.

But that's not as cool as having an aftermarket Tach on your column with a huge hose clamp...

LOL Sorry I had to.

You don't have to use a huge hose clamp... you can use duct tape. And duct tape comes in multiple colors now too.

3X00-Modified wrote:

1988GTU wrote:You could have the cluster rebuilt if its in need of a recali and some bulbs. Last one I sent out was about 100 shipped to and back.

But that's not as cool as having an aftermarket Tach on your column with a huge hose clamp...

LOL Sorry I had to.

heavywoody wrote:You don't have to use a huge hose clamp... you can use duct tape. And duct tape comes in multiple colors now too.

lol fail.

I was actually considering running a mounting bracket from behind the cosmetic cover and up forward. Then bend it to come out at the right spot.
This way I won't need any duct tape or hose clamps.
Like a length of stainless steel mounted behind the plastic covers, then bent properly to pop out between the cover and the column and then hold the tachometer.

But its nice to know that any aftermarket tachometer will work as long as its set to 6 cylinders.
Does anyone have any suggestions as to which brand/style would look good?
I've seen some different brands, but idk which one would look good without making it look cheap.

I have to admit... I had an Autometer 5" tach in my red car before I got a full cluster and it was an auto.... LOL FAIL!!

Right around the same time I did this...



Vinly racing stripes FTW YO!

To answer your question though... SunPro Tach's work pretty good and would probably offer you a decent sized one that would fit and not look completely out of place.

heavywoody wrote:You don't have to use a huge hose clamp... you can use duct tape. And duct tape comes in multiple colors now too.

Duct tape sucks. Black gorilla tape ownz.

JB Weld makes it like a factory install mannn, c'mon people! use your heads!

Watch out if you are buying an old used tach, or buying a cheap one. Some of them are NOT compatible with DIS (distributorless, direct ignition systems). Even setting the number of cylinders correctly, it won't read right. Most decent quality newer tachs should be fine though.