So right now my N/A SD tune is dialed at 12.6-12.8 AFR at WOT. But it seems like after every cold start, even though the truck is warmed up to operating temp, the first pull is alway rich like 12.0-12.2. Then the 2nd pull after that it's good again right back to where I had it. Has this ever happened to anyone or anyone know what it could be?

 

What injectors do you have?

 

Depending on the temp there is an adder for coolant temp to the PE table. Even though its "warmed up" it still modifies a little bit until its really warmed up.

 

I have the factory 50lb injectors that come with the ly6.

I'll look into that adder, thanks.

 

I've always noticed that whenever I go to a dyno day that most cars make more power the 2nd or 3rd pull. Has anyone noticed this also? My truck has never been on a dyno but it always seems like the 2nd pull feels better than the first. I don't have any track times with this set up yet but it would be hard to duplicate that because of how long we wait in line between runs.

 

It should be the same really...the dyno operator might make adjustments to the load rate to help the car rev faster so it seems like it makes more power, or the tuner may make adjustments in between. Lot of variables there.

 

I've always seen best power with coolant hot.. 210 or higher. I always think its funny when everyone wants to run their coolant around 180 with 160 degree thermostats. By the third pull on a dyno, coolant is hot and typically picks up horsepower

 

^Thermo wise, the hotter the air and fuel coming in the more efficient your combustion is going to be.

Problem is these engines are nearly always knock limited, meaning if the fuel/air is too hot you have to pull timing to keep the pistons alive and any increase in power you would get for the hotter air charge is now lost from the reduced timing.

 

Yes and I think the 185 degree thermo is perfect four our trucks. Coolant stays around 190-210 which is the best compromise IMO.

 

I've seen it on days where they just get 3 pulls for like 40 bucks. No tuning or anything involved.