blue5.0

I was just reviewing a log I just recorded and noticed that at WOT in the mid-higher RPM range I was seeing knock readings of about -5. Does that mean the computer is adding additional timing in? My assumption would be that my tuner could safely advance the spark/timing on this tune? Timing is 27.5 at Wot FWIW.

BadCon

Yes, negative knock readings indicate the computer is adding timing. There is a preset maximum as determined by the tune, and I'd trust the tuners judgement on that.

blue5.0

Thanks for the response. I always go with what they say. I just want to understand the tuning and datalogging a little more.

BadCon

Just to ease that part of your soul that's always going to want more, you are at the upper limit of acceptable timing with pump gas on a street car. Its not a dangerous level, but is about as high as you'd want to go without E85. E85 will buy you a few degrees more timing, but 27.5 degrees is healthy on 93 pump gas. Sounds like a good tune if its showing -5 knock at WOT.

blue5.0

I definitely like to hear that and that's the info I'm looking for. This isn't my go fast tune, so not a huge concern. This is a 93 tune but I use e85 pretty frequently.

Spooled

Also, it shows that you're getting good quality fuel. Badcon is right on the money about that much timing on 93.

blue5.0

Glad to hear. Thanks for the reply. I've been nothing but happy with MPT. I'm just trying to better understand all of these PIDs that they have me log.

w00t692

I've seen the add timing up to 30 degrees letting the knock sensor add it on it's own. The difference in power between 28 and 30 degrees of timing is under 8 horsepower, so it's not a big deal either way.

blue5.0

I've read that maf flow rate x 10 is a pretty good indication of crank HP. Any truth to this?

w00t692

yeah and then multiply it by .85 to get a more realistic number for the wheel horsepower.