Since upgrading to high res, I am experiencing the random "hiccup" on my MSPNP9495 (tach drops out randomly for a split second under load).

I am about to do the JS8 to Ground, 0.1uF capacitor mod which should fix this issue. I've seen diagrams/photos for the 3.0 PCB but not the 3.57M which MSPNP uses.

Can you guys take a look at the photo below and tell me if this is correct? Thanks.

 

looks correct to me.

 

Thanks. I installed the cap yesterday. Took the car for a quick spin. Haven't tested thoroughly but so far so good.

 

What is JS8 anyway?

 

input for tach from the CAS, IIRC.

 

Yup. JS8 is just one of many "spare" I/O pins of the CPU brought out to a via on the board. When one is using the second trigger input, the MS is hard-coded to look at JS8 for that input signal. For those following DIY's How To... writeup, JS8 winds up getting wired out to the IAC1A pin of the DB37, with a pullup resistor.

 

So you're putting this CAP between the tach input and ground?

Reason I'm asking is because some AEM ECU's do the same thing.

 

Schematically, this is what it works out to:



CMP is the open-collector input from the sensor, JS8 is the CPU pin. The original design (and the one still currently posted at the DIY howto) omits the capacitor.

 

We added it to the text of the how to article a while ago, but need to update the pictures.

 

Go a picture of mine here if it's any use to you?

Also pics for the TPS mod...


http://www.mx5nutz.com/forum/index.p...12887&hl=*pnp*

 

Just to make sure I'm doing this right.

On a MS2, I would need to do this to JS10, not JS8, right?
Or are the CMP/CKP pullups not needed for the '99 sensors?

 

Don't confuse this with a pullup. A pullup is a resistor that biases the pin in question towards +5, expecting an external pull to ground. So yes, the NB sensors need pullups too.

This mod is just a filter to try and combat noise on the input in question. I've not heard of people having this issue with MS2, but if you were to need it, then yes, it would be on JS10.

 

Thx for explaining that Joe. I'll be building similar input circuits as Abe's, so I assume these completely replace the CMP circuit posted above (and the corresponding CKP circuit), right?

 

Yup. They go from the CAS directly to the CPU, bypassing all the on-board circuits. Make sure that you have no jumpers installed on the MS PCA in either TSel or TachSelect.