I pulled a 2004 4.8 auto from HP Tuners repository that is "supposedly" stock. I'm seeing the same on VE untouched but on the idle airflow a lot of the idle airflow adaptives are either different factory numbers or the tuner was monkeying with them. The base running idle airflow (BRAF) has been adjusted but my guess is to a "canned" number and not plotted against the idle airflow histogram in the scanner (because correct idle airflow config takes a good amount of time).

For those that are unfamiliar with HP Tuners... when you compare two different tune files, the tables that show green are different between the two tunes being compared.

Stock 4.8 Idle Airflow File



Op's Tuned File



Stock 4.8 Base Running Idle Airflow (BRAF)



Op's Base Running Idle Airflow (BRAF)

 

Don't forget these guys... GM idle stability requirements actually state that these calibrations alone should be capable of producing a stable idle, spark control disabled. They can also be used in tandem with the throttle follower (stock in the OPs cal) to produce a very sharp tip-in throttle response.

 

Yes, Tri-Ys had definitely crossed my mind as something that may help make this exhaust-heavy cam happy. In particular, I’ve always understood that they help low RPM torque (as you said), and that’s exactly what I’m after. Others have thoughts/opinions on that?

Keep the input coming on the tune. I’m keeping a list to go over with whoever I find for another tuner.

 

Unrelated to your specific build, however still useful- I am looking at LS headers right now for a swap, and tri-y's seem to only be a DIY thing. I have yet to find them off the shelf for our trucks. Everything is equal length that I am seeing

 

I have been following along this thread and would just add my 2-cents, I have a 2007 4wd crew cab with a 4.8, best upgrade swapping to 4.10 gears. I also have a PCM of NC 93 tune and a cold air intake. My next step is headers down the road since I was told that would be any easy extra ponies with out cracking the motor open.

Gears woke this truck up huge IMO since these engines only move after 3,500-4,000 rpms.

 

Doug Thorley makes them from 99-2013 and they are the same ones between those years. Looks like i was wrong on the LS trucks being smog legal ones. I forget the cat location necessitates moving the cats on long tube designs on the trucks.

 

https://www.summitracing.com/parts/d...silverado-1500

I have seen people knock the tri-ys because they lack some of the top-end hp improvement of a 1-7/8" primary long tube. They fail to look at the average torque gain from say 2,000-5,000 rpm where the tri-ys smoke the standard long tubes and are far more benificial in a truck.

 

Thanks for the link! I didn't say they didn't exist, just that I hadn't seen them.

You got a dyno graph by chance showing the midrange gained by those? At $800 a set, I can almost buy 2 sets of TSP 1 7/8 equal lengths, so the DTs better come out swinging from a $/tq standpoint

 

For what vehicle exactly? These come with the y-pipe for a truck. Once you add the y-pipe to the TSPs they're very close.

 

1-7/8 headers on an engine that is only 36.75 cubic inches per cylinder that is not even turning 6,000 rpm is akin to shooting yourself in the foot and double so when that engine is over cammed. I have not seen exact charts from the LS truck crowd but i have seen them on both a 6.1L Hemi as well as a 6.2L. The 6.2L was in a G8. Both the 6.1 and 6.2 saw gains starting just over 2,000 rpm and had 25-30 ft/lbs increase across the whole powerband. The G8 still on the factory tune ran a 12.66 @ 110 on factory tires after the headers went on.