First Experience with Det, bad gas or bad spark
 

Yesterday I had my first real experience with detonation. Ambient temp was around 85 and I had just filled up the day before so this was the first time I ran the car in 75+ weather on this gas. At first I didn't even hear it but the knocksense flashed twice. I boosted to about 6lbs a second time and definitely heard it.

I'm running the following spark map except that I've reduced spark in anything over 100kpa by 2 degrees:

http://www.boostedmiata.com/gallery2..._2010_MSii.jpg

When I got home I reduced everything in 100+ kpa by another 3 degrees and went for a spin; everything seemed fine (although by that point ambient had dropped another 10 degrees).

The reason I think that it's just a bad tank of gas is that I've been running this map for a while and we've certainly had hotter days than yesterday down here. Not to mention the relative humidity was quite low yesterday. Last week I was boosting with no problems at 90 degrees ambient and 75% humidity.

Is this something that happens often? Should I tune for lower octane just in case?

Edit: I pulled my plugs today and no signs of det, in fact they look exactly the same as they did back in February (I took pictures). Though I know that doesn't mean anything concrete it's certainly not what I expected.

(zack morris's phone)

That map has too much advance out of boost. In boost is similar to what I run.

My intercooler isn't the world's most efficient so I backed it off in boost and I ran the base DIY settings in the upper right (>5200rpm, 101kpa) as an added bit of protection. With the knocksense tuned to 5K this should be ok.

I'm certain I'm leaving power on the table now but it's worth it if I don't see white smoke on a hot day. At some point the "little bit more" mentality needs to be ignored.

What octane was it?

Sorry for the delay in response. It was 93 octane. I really feel like I lost a bit out of boost (in boost as well). So I'm going to add a degree or two in a few areas around 84kpa when we have another hot day to see if I can get it back.

I considered running a knock light unit but since it won't connect the to the MS and I have the detcans for tuning it would probably be a bit of overkill.