Miata Turbo Forum - Boost cars, acquire cats.

Hello MT!

I've got a small problem with cranking / starting in a 1.6 NB (Euro car) with a Reverent-made MS2. I have been searching on the forums, but I don't think I've found something similar to my experience - I've seen threads with somewhat similar symptoms but on cars with numerous mods, where the problem ended up being attributed to the mods. My engine is stock for now, with only mods an air filter and the MS. In short, i apologize if this already covered in another thread! :)

Starting off of the base map provided by Rev which was fine to begin with, I've done some tuning and have made the car start and run almost like stock.

Although the engine starts every time with relative ease - some times more easily, others less so, but never with any particular difficulty - sometimes during cold starts I notice a sound which I believe is starter kickback.

To be precise, the starter starts turning the engine and at the moment when the engine catches I hear a clinking noise. Right after that the engine seems to start fine, no problems or anything - apart from a short whine sometimes, which Rev attributes to a slightly loose belt.

I've tried the following:

- Different cranking advance settings (0, 5, 10, 12, 15) - currently set to 12 degrees
- Different cranking RPM settings = currently set to 650 rpm
- Different Cranking PW for more / less fuel

I've seen how many of the settings make things better in terms of ease of starting / flooding (or avoiding that :P ) etc., however I don't think that any of the above has had any consistent / definite result as far as the clunking noise is concerned. I think cranking advance has made things better, but not what I'd call solving the problem. I've also noticed that it doesn't happen every single time (under the same conditions - e.g. cold / warm engine, weather etc), and also it's pretty much evident now that it almost doesn't happen when the engine is hot (i.e. in normal running temp)

I swapped the fuel pump a few days ago and i think it's improved things quite a lot. What I also tried doing is to "prime" the pump twice (key on - key off - key on), which also improved things a lot. I think that even a cold start is much more likely to NOT clunk if I do this.

One thing that I've noticed in the logs and I think is related to this issue is the following:
Regardless of what the cranking RPM is set to, most of the times it seems while starting, the RPM go above the cranking RPM, then momentarily dip below (so it goes into "crank" and not "run" again) and then back up. I am attaching logs to show this. I think I see it every time I hear the clunking noise.

I am attaching a logfile where the problem happened, where you can clearly see the dip (log_1), as well as another one where the engine starts perfectly and no dip exists in the logfile (log_2).

I've received advice relating this to ASE settings, which I tried altering but don't think it made it consistently better or worse - or, at least, I did not understand it if it did!

I am pretty sure one or a few of my settings are not ideal (obviously :P) and I'm not sure what I need to change - as mentioned, I've tried things that have made it better or worse (e.g. starting and dying from too much fuel or starting and running too lean).

Has anybody come across this? Any feedback that could point me to the right direction, i.e. which setting could cause this behaviour will deffo be appreciated.

Thanks!!