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Old 03-26-2010, 11:20 PM   #1
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Default ECU pulling timing

I've got a '99 hotside intercooled MP62 running 9psi. Had it dyno'd yesterday and AFR looks safe at 11-11.5 throughout the rev range.

The thing that concerns me is that the ECU pulls quite a bit of timing from 4500-5500 under wot. I assume it's detecting knock, but it seems strange that it then gives it back from 5500 to redline.

I have a scangauge showing ignition timing if 17 or 19 during these events. Anybody out there experienced this or know what the cause might be?
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Old 03-27-2010, 12:58 AM   #2
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What are you using for engine management? It could be any number of corrections in the tune (coolant temp, air temp, etc) or possibly even knock depending on the knock profile you're running. So many different variables it's hard to say without seeing the tune and a log.
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Old 03-27-2010, 01:06 AM   #3
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Quote:
Originally Posted by black99 View Post
I've got a '99 hotside intercooled MP62 running 9psi. Had it dyno'd yesterday and AFR looks safe at 11-11.5 throughout the rev range.

The thing that concerns me is that the ECU pulls quite a bit of timing from 4500-5500 under wot. I assume it's detecting knock, but it seems strange that it then gives it back from 5500 to redline.

I have a scangauge showing ignition timing if 17 or 19 during these events. Anybody out there experienced this or know what the cause might be?

From the factory, the stock miata ECU will pull quite a bit of timing around peak torque to reduce the likelihood of detonation. There is a very noticeable 'dip' if you look at a wot timing curve. Also, it is possible that the stock ecu uses rpm dependant knock detection, which only compensates for perceived knock in a given rev range and ignores it above and below.
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Old 03-27-2010, 01:48 AM   #4
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I've got the PCPro/Timing Card setup, so not a whole lot of options for me.

My timing card is currently set up to pull about a deg per pound of boost.
I'll probably just bump that up to see if it changes anything. Between my knocklite & scangauge , I should be able to tell if it's making a difference.

I hate to pull timing if it's just phantom knock, but better safe than sorry.
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Old 03-27-2010, 12:17 PM   #5
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Pulling more timing will probably do it. If you decide you are tired of leaving power on the table and also want more safety, it would be worthwhile to invest in solid engine management at some point in the future. Good luck with it.
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Old 03-27-2010, 02:31 PM   #6
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Thanks for the feedback. I set my timing card to retard another 2 deg at 9psi (was pulling about 6, now about 8). The ECU seems happier with this. Scangauge shows 22-23 ign during wot pulls to redline. Hope to go standalone engine management someday, but till then I'll make do.

That's one crazy build you've got JayL. Must be a handful on the road course. Maybe I'll see you out there sometime.
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Old 03-27-2010, 02:51 PM   #7
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Thanks, I had no idea that you were local. It's good to see more forced induction folks in the northwest.
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