How do I make my stock BG astina tachometer work after swapping a BP engine?

[ElvenMishi]

Hi,

How do I make my stock BG astina tachometer work after swapping a BP engine?
I'm currently using MegaSquirt as my ECU.

Thanks,
Ebb

[DavoAust]

Bp engine was the stock one? it should work like normal?

If you're referring to the ECU swap, the bg Speedo was cable driven off the gb Speedo gear and should be fine as well?

[derb]

Originally Posted by DavoAust

Bp engine was the stock one? it should work like normal?

If you're referring to the ECU swap, the bg Speedo was cable driven off the gb Speedo gear and should be fine as well?

Agree. What's the issue? Check that the cable is installed properly or even working.

[ElvenMishi]

Davo and Derb,

Thanks for the quick reponse. I guess I've got two problems that I need help on. First, tacho is not working after I changed my tranny from an F series to a G series. Cable from the gauge and th gears from the tranny doesn't seem to match. Second, speedo doesn't seem to be compatible too.

Any work arounds?

[derb]

I did the same thing and my cable worked, although the speedo read 10k under. Not sure whats gone wrong for you.

[TheMAN]

must be a wiring issue because BP engine swaps in BGs are very straightforward... even the original mismatching tach will work!

perhaps it has something to do with your megasquirt? most people just use the stock BP ECU to run their engines, which is the easiest and cost effective

[ElvenMishi]

I was thinking of the same thing. Originally, I had a 1.6 sohc carb engine before the swap. The gears on the from my analog tach seems to be incompatible with the digital plug from the g series tranny. Should I be using a different speedo cable or some sort of adapter to be able to connect the two?

On the speedo, electrical signals from the coils doesn't seem to work with the gauge.

[DavoAust]

Ahhh so what you're asking is to get the 1.6 speedo working with the BP G tranny?

In theory you can get the cable and speedo gear from a BG BP with a g series box. I've never done it but it should work. You might even find someone on here with one.

Your issue then will be getting the speedo to match the actual speed as i'd say it'll be out a bit. Maybe theres a converter somewhere for it

[Rupewrecht]

Try using your old F-Series sensor in the G gearbox.

[TheMAN]

it won't work rupe.... the F series parts are very different and doesn't fit
keep in mind all BGs use cable speedos and not electric speedos

to make the speedo work, all one has to do is get a matching speedo cable to the gearbox... the cable connection at the back of the gauge is exactly the same, no matter the engine... only the tach differs in range and redline depending on engine

[ElvenMishi]

Originally Posted by TheMAN

it won't work rupe.... the F series parts are very different and doesn't fit
keep in mind all BGs use cable speedos and not electric speedos

to make the speedo work, all one has to do is get a matching speedo cable to the gearbox... the cable connection at the back of the gauge is exactly the same, no matter the engine... only the tach differs in range and redline depending on engine

TheMAN,

This is true. Any idea what cable should I be using? From what car model should I get it from?

Also, will fixing the cable solve both speedo and tach problems?

[TheMAN]

the cable won't solve your tach problems, but will solve your speedo issues
you just need to find a cable that's from the same car you got your engine from... all BPs came with the G series gearbox in the BG, only the smaller engines got the F series gearbox.... speaking strictly FWD of course

[ElvenMishi]

That's interesting! I will look forward to trying out that solution.

So do we have any ideas on how to resolve the tach compatibility issues?

[project.r.racing]

1.6 carb engine runs the tacho of a sensor in the dissy straight to your dash.
1.8 efi engine runs the tacho of a sensor in the dissy through the ecu, then to your dash.

if you are not using the 1.8 efi ecu, this is your issue.

try using the 1.6 carb dissy on the 1.8 efi engine.

[TheMAN]

I believe the carb disty also uses vacuum timing advance instead of electronic
really, unless you have done significant modifications to the engine internals, just use a stock ECU instead of the megasquirt! much less hassles!

[ElvenMishi]

TheMAN,

I don't have any internal mods but my bp is on turbo so I will need the MS ECU.
Is there a way to make the tach compatible? Any work around?

[project.r.racing]

install aftermarket tacho

[ElvenMishi]

Does this mean that all astina BGs that converted from sohc to bp are on aftermarket tachs? Can I swap circuits from a miata dash to my astina tach to make it work?

[Clean_Cookie]

No, derb and many others just swapped motors and boxes out and maybe you got a ba g series box?

[project.r.racing]

Originally Posted by ElvenMishi

Does this mean that all astina BGs that converted from sohc to bp are on aftermarket tachs? Can I swap circuits from a miata dash to my astina tach to make it work?

no. but most would be running the stock dohc ecu which would have the correct tachometer signals to/from the dash cluster.

Originally Posted by tc3_racer_001

No, derb and many others just swapped motors and boxes out and maybe you got a ba g series box?

gearbox has nothing to do with tachometer.