What arf are you seein on a stock gt? Mine is showing 11.6 at Wot and thats what I used to cee on my boosted 08

 

You do realize that boosted cars are optimized to run within the lower 11.4 - 11.8 A/F right ?

The GT you have now is naturally aspirated and not forced inducted as your previous 2008 was.. Therefore your optimal A/F ratio for a naturally aspirated application should be within 12.5 -12.9 at WOT !

 

That was the point I mentioned it,how would they tune the car to 11.6 on Na from factory

 

That confused me as well, as it doesn't make any sense.. On a N/A car, an 11.6 A/F would be extremely way too rich

 

Are people seeing as-advertised fuel economy?
Whats the AFR at cruise?

 

Its around 14,and gas mileage seems to be a bit lower but I have a heavy foot but at cruising at 55mph it does 35 mpg avg on a tank mostly city is around 20

 

The OP is referring to what his A/F ratio is at WOT, and not at cruise..

As I posted earlier, an 11.6 A/F ratio at WOT is way too rich on a naturally aspirated 4.6 or 5.0 !

 

Running a little rich in an NA motor with 11:1 pistons probably isn't a terrible thing. My supercharged '07 GT ran 11.6 AFR at WOT. My NA '14 GT runs low to mid 12's AFR at WOT, but that's a custom tune. Not sure what it ran stock, but a little rich wouldn't have bothered me.

 

Brian ! running just a little rich over extremely rich is a terrible thing and that does bother me..

My supercharged 06 GT has an 11.7 AFR at WOT which is normal and tuned correctly for a forced inducted application, however that's not the case when it comes to a naturally aspirated 4.6/5.0..

Just as you pointed out, your N/A 14 GT runs low to mid 12's AFR at WOT and for a custom tune, that's still considered as being somewhat on the conservative side..

At WOT, you should be looking at between 12.5 - 12.9 AFR safely with no issues whatsoever..

Now as for the 11:1 compression factor on the new 15's are concerned, perhaps that's why the AFR from the factory is 11.6 ? But that still seems really low at WOT for a naturally aspirated GT

 

Better to run a little rich than to go too lean and put a hole through a piston. Running rich is the safer of the two scenarios by far.

 

I understand what your saying Brian, but running too rich isn't really safe for your engine components either !

 

I think the OP needs to take his Mustang to his dealer and have them look at it. Maybe the gauge is off? Let us know what your dealer says about it.......

 

Maybe that's all it is David ? At least lets hope so anyhow