BBR Turbo problem
 

I have a problem!

Background info...
The car is a 1990 Mazda MX-5 (miata). It is a limited edition BBR Turbo.
The BBR Turbo has a piggyback ECU in addition to the Mazda one to adjust fueling and timing as required.

With the Megasquirt plugged in (only the inputs, not controlling injection or timing) as soon as I rev over 2500rpm the engine cuts temporarily until it falls below 2500 again.

I assume that the BBR ECU takes over the timing and fueling above this 2500rpm mark. To me this seems like the piggy back BBR ECU doesn't like sharing the CMP or CKP sensors.

Download datalog200701261509.xls

Maybe I'm dumb, but what is a BBR Turbo?

BBR Turbo was a turbo kit installed aftermarket from that factory by some British company I believe. Maybe 400-800 were built.

http://www.mx5-3rdgenerationlimited.com/bbrturbo.htm

See there

Very cool car, sorry I can't offer any help.

My knowledge is not every good but here's my ideas....

To prevent the engine running wither the fuelling must be cut or the spark must be cut.

If the fuelling was in the log viewer the mixture would be very lean
If the spark was cut the mixture would be very rich.
Looking at 140seconds where the problem starts. I come off the throttle at 143 seconds after its bounced a couple of times. The o2 level remains high up until 144 seconds.

Basicly does this mean as its running rich the problem is with the spark?

Just a quick check, have you done the CAS mods?

my guess would also be that the cas mod hasnt been done correctly.

Here's a photo of the underside of my board. The other wires on there are for the USB communication.
http://i100.photobucket.com/albums/m.../CasWiring.jpg
I've use 1W resistors instead of 1/4W ones does that matter?

Is your CAS wiring the Blue and the Red wires that go from the middle of the pic to the left where they are both covered by the black tape?

In the pic it looks like those two wires join. Is that the case?

The CAS wiring mods are supposed to connect to two wires from the CAS, so there should be two inputs from the DB37 connector (ie there should be two seperate wires going into the DB37 connector on the board).

Is it possible that I've wired the CMP and CKP to opposite pins?

On this page they both go to the IAC1A?
http://www.diyautotune.com/images/ca...input_mods.jpg

Ooooops I stuffed up!!!!

Check your Connections to pin 24 and pin 25 on the DB37 connector.

Is this clearer?
http://i100.photobucket.com/albums/m...CasWiring2.jpg

Can you show me how yours is modified pelase?

I don't have a pic of the underside of my board handy and I'm not keen to go out to my gar in the rain and remove the hardtop to then remove the side of my roll cage to then access the Megasquirt in the footwell and then pull it apart to get a picture.

Go back to the diyautotune page and follow the written instructions.

"Getting the Tach Input Signal:

Run MSnS-E and the "2nd Trigger" Wheel Decoder option (where the missing tooth on the wheel decoder comes from a second sensor, usually cam position). The CAS has a CMP and CKP signal, so you take the outputs of each and run them into the MegaSquirt. Take the CKP signal (4 holes in the Optical sensor wheel, the "outer" ring of the CAS), and run it to the primary tach input on the MS with a 12v pullup resistor - then you take the inner ring of the CAS (1 hole in the sensor wheel) and run it to the secondary tach input on MS (it's pin 11 on the MS-I cpu) with a 5v pullup resistor.

If you follow my documentation for the mods below you'll externally wire the tach inputs like this:

The Primary tach input (CKP) (Reported to be White on Miatas) is connected to pin 24 on the MegaSquirt's DB37

The Secondary tach input (CMP) (Reported to be Yellow on Miatas) is connected to pin 25 on the MegaSquirt's DB37"

quoted from http://www.diyautotune.com/tech_arti...azda_miata.htm

http://www.asbi52.dsl.pipex.com/megasquirt/MS30.jpg
That photo has some extra wires but are you saying that this one isn't right too?

I've wired the ckp and cmp to the correct pins. I dont understand what else needs to be done? The 12V and 5V pull up resistors are one the board. I dont understand what else needs to be done? I'm sure mine is right.

yeah Rich, that's mine...... those extra wires are part of the mods for spark control, they need doing on yours too......

I was planning on not doing the spark until later. It is likely that's causing my problem?

is it easy to unplug the piggy back you've got on there to make sure it it not contributing to the problem?