Autocross with models 2017+ IAM (ignition advance at 0.7)
 

I've recently learn that on the 2017+ models, each time you start the car, the IAM (ignition advance multiplier) is set to 0.7 instead of the 1.0 needed to have full HP.
The IAM is then increased toward 1.0 if there is no knocking detected. I don't know how long it take to go to 1, or if you need to drive hard.
So when you autocross with a 2017, and stop the car between each run like I used to do, you loose a lot of HP on your next run (maybe 20HP?).

If someone has more information on this, can you share?
How long does it take for the IAM to go back to 1?
If I do a hard launch, by the time I shift in second, is the IAM near 1? Or do I loose power for a significant portion of my run?
Is a complete run even enough to bring the IAM back to 1, so that at least the second run is with full power if I don't turn off the car?
How much HP are we approximatly loosing?
Without an Ecutek/OFT, is there a way to monitor the IAM (with an OBD2 reader)? If I monitor the timing advance, can I deduce the IAM from that reading?

For the next events I'll probably resort to keeping the car running between run, and open the hood to prevent heat soak... :iono:

Where did you learn this? Never had an issue autocross'ing a 2017 car for a year and a half. Mine has been tuned of course though, not stock.

This is true of all years but it's hard to say how long it takes to climb. Too many variables. Some days my car takes 4mins in my morning commute to get to 1.0 and same days I go 30mins and it still hasn't reached 1.0. My suggestion is to spend the $170 on a Tactrix cable and change the IAM to 1.0 so you don't have to wait for it to climb anymore. This also opens up possibilities of datalogging and the ability to use Techstream. Well worth the $170.

Yes, it's how the factory tune allows for lower octanes, in my experience it's about 3-4 miles of street driving to come up to 1 on my 91 gas, haven't bothered looking during autox. As far as I can tell it's to compensate for different octanes and the early cars have the same default tuning.

More aggressive tunes set it to 1 to start (typically one of the differences between a 91 & 93 octane tune) as seen in the OFT V2 vs. V4 tuning, there's a bunch of discussion about it in the thread about the latest OFT tunes:
http://www.ft86club.com/forums/showthread.php?t=126180


Realistically there's so many other ways to hang yourself in autox, the 2-3-4 ponies you're losing with a lower IAM won't matter after the first corner you miss an apex by 4 feet. As long as the car is warmed up you shouldn't be down on power (unless you're comparing tuned/modded cars)

I guarantee it isn't 20hp.

Edit: A thread from 2014 talking about the default IAM of 0.7 and how it factors into compensating for octane rating and the kind of power delta you can see as it ticks up to 1.0
http://www.ft86club.com/forums/showthread.php?t=70729

Nice, learn something new every day!

In the thread you linked about it says its around 10-15hp. I've had the unpleasant experience of doing track sessions where I the IAM would stay at 0.7 and that was making around 1s per minute on the track. I dont know how that works for autox since speeds are lower, but on track that 0.7IAM will make itself very noticeable (and makes you loose championship points!)

I saw it on that thread:
http://www.ft86club.com/forums/showthread.php?t=127898


Particularly post #10 and after. I tought it was only on the 2017, but I'm not sure anymore. Since your car is tuned, I think most tune set the IAM to 1 by default so you would not be having this problem.

I'm sure 10-15 hp can make enough difference to lose a position or two. On the track, when it goes to 1 does it happens fast, or can it take a couple of laps?

I wouldn't bet on it reaching 1.0 on a 30 - 60 second autox run and idling alone isn't enough to make it climb.

Damn, so i'm doomed to race with less than 100% power! :cry:
The idling between run was not to make it raise, but at least to prevent it from getting back to 0.7.
Even if it doesn't reach 1, at least by the 3rd run it may have increased and gained a couples of ponies...

You mentionned getting a Tactrix cable to modify the IAM to 1, but that probably means a custom tune, and technically that isn't allowed in street class.

Any way to read/know the value of the IAM with a OBD2 adapter?

That was @steve99 making up a number. Feel free to provide contradictory info but I found a bunch of dyno charts in there that didn't see a difference greater than 4 hp on an NA engine between 91 & 93 octane.

Maybe @justinco will get ambitious and do a test ;)

I guess technically it would be a tune but if all you are changing is the IAM it's hardly what I would consider a tune but it technically gives you an advantage over a completely stock car. You can get a OBD2 adapter on Amazon for $18 which is compatible with Techstream and Techstream is capable of logging any value on the ECU including IAM.

I was thinking about this, and thought it might be the reason that the first couple runs on the dyno always read ~10-12hp and torque lower than subsequent runs.

Would definitely be interesting to see if it comes into play during autox. I'll have to do some ECUtek logging at the next event. I'll also see if mine is set to 1.0 to begin with. Or, could just ask Zach with Delicious how he does things :)

I would think you could get it with your solo storm setup?