MS2 squeal on startup
 

I've got an odd noise on startup after I finished installing my Reverent built MS2 on my 2004 MSM. It sounds like a belt squeal immediately after the car starts up, it lasts for maybe 1/4 second.

Relevent info:
2004 MSM / 18,500 miles / Stock injectors / Stock 8 year old belts / Starts and idles fine on the basemap Reverent sent with the MS2.

It sounds like I'm experiencing exactly what y8s is describing in the last paragraph of this thread: https://www.miataturbo.net/megasquirt-18/nb-turbo-ms2-pnp-alright-who-has-similar-setup-has-tuned-their-start-up-61453/

"The belt squeal is a point of contention between myself and Reverent but I had the same problem and lived with it until I found a way to fix it. I believe it's the alternator running at full tilt charging during startup and cranking (system voltage is low which makes the circuit charge) and the additional load on the belt makes it squeal. He says it's a loose belt. The fact that it doesn't do it on a stock ECU startup suggests belt tightness varies with the type of ECU used. Wat."

I've swapped the stock ECU back and don't get any belt noise after start up. If I just need to swap out belts, I'm fine with that, they are due anyway. Its just curious that I have zero belt noise with the stock ECU in place.

Has anyone done anything other than change belts to solve this?

I've never had this problem on my car or on ANY of the 20+ 99-05 cars I've tuned locally. Weird.

While I don't dispute the fact that it happens on your car, maybe your belt is ever-so-slightly loose, and my ECU trying to charge from cranking causes it to squeal. So try tighten it and see if that works for you.

I have thought about making the alternatror not charge below 400rpm, but then I'm depending on the RPM signal, and if that fails for any reason (ie you accidentaly change the tacho output parameters) then you will be stranded because of the no-charge condition. So, while this is a VERY simple mod for me to do, I do hesitate to do it.

Of course, the customer is always right, and if several more people show up and request this, I'll do it.

No problem, I'll try tightening it. If that doesn't do the trick I"ll go ahead and replace it and re-tension it again.

Everything else has gone great so far. I had no issues getting the car running.

Thanks!

Its always great to hear good testimonials! Keep on sharing!

ive had to do this on two installs now after complaints, y8s had to on his as well.

Same thing here..

Alternator belt never once chirped with the stock ECU, but I got massive squealing episodes after starting, once I had the MS2 installed.
Tightened the belt, and all seems OK so far.

For what it is worth, my stock ECU was acting weird and charging at 14.9 to 15.2 volts. That may have done a number on the battery.

Our testing has shown that the stock computer targets 14.9 volts.

Interesting. I used to see as high as 15.7 on my nifty gauge setup.

Same here.

using a spare output and tip125 or something to prevent the charing cirucit from activating before 200-300RPM fixes the squealing issue.

I don't need to, since my charging circuit is a microcontroller and so I can control the charging based on anything I want (RPM, time ON, etc).

aren't you a baus?!

Just an update. I tightened the belt just a bit and it hasn't made noise since.

I too have a rev built unit (MS3) just installed it today in fact, I too have the squealing belt issue for about 30-45 seconds after the car starts, very loud! It just replaced the belt during a timing belt and water pump change. The belt is tight. Any ideas?

same thing here switching from stock ecu to one of Rev's MS2s. Belt was mildly loose, tightened it up and seems okay now. Thought it was pretty odd, glad to understand what was happening, and that I wasn't the only one...