Cam Timing "Limiter"?

[mxatunerjg]

Last week I was tuning a 2011 Challenger SRT8 6 speed and currently doing a 2015 Challenger SRT8 6 speed. Both cars are giving an issue when advancing cam timing. Let's say I run a flat advance curve of 130 degrees for WOT (exhaust cam). Both cars will dip aircharge by about 12% at 5500 rpm. They will stay like this until about 6300 and then come back up to normal aircharge for about 200 rpm and then drop back off. If I drop the cam timing to 126 degrees at 5500 rpm and keep it there until 6800 it will move the point that it drops the aircharge to about 6500 rpm. If I set it to 125 at 5500 and then 123 at 6500 and 120 at 6800 the pull is smooth without issue right to redline (6800). The issue is when the aircharge drops so does the fuel demand which causes the car to lean out. It also causes timing to increase due to the difference in load. I've used setting like this before on other cars without issue, but for some reason these 2 cars don't like it. Actually I've done other 2015 6 speeds and even went to the point of overlaying the tunes and making sure all settings were the same, and still have the same problem with this 2015. The problem here is that we are leaving top end power on the table by not being able to run the cam timing where we want to.

Just some thoughts I had on this. The map reading does not change when this happens so manifold pressure is not changing. While the car does lean out, it is going lean by 12%, so in this case it is around 12.0 afr which puts it at about 13.2 - 13.5 afr. Timing increases at the same time by a degree or two. This would generally lead to a slight gain in power, but in the curve I'm looking at currently at 5700 rpm is shows 456 hp and at 5965 is shows 434. At 6165 is is 431 and then at 6365 it is 470. It doesn't misfire or get rough around this area either. The dyno readings look identical to the aircharge, fuel mass, and injector pulsewidth curves.

Has anyone else seen an issue like this?

[mxatunerjg]

So upon further testing (and some thinking about what was happening), I found that the Short Runner Valve is switching when the cam timing is advanced beyond certain points at certain RPM points. How to fix it I'm not sure, so open to suggestions. Basically the SRV switches at the normal 4700 rpm then switches back to it's low rpm state when the cam timing is advanced beyond this hidden value.