I have a 99 silverado 2500 that came with an LQ4. I changed the engine to an LQ9 out of an 04 escalade with 40K. I got the truck dynoed yesterday just for fun and was a little dissapointed when I made 257 hp and 308 tq at the wheels. The guy showed me the air fuel ratios and how the tuning is all off for this engine because I am still using the old computer for the new engine. DO I need to get an 02 computer and then get it tuned or can the guy just tune it using my old computer?

Their tuning guy wasn't there when I went, but they claim that he is very good and uses hptuners. My truck should be making more power than this with supporting mods, don't you think?

 

you will be fine getting a tune on your stock computer. you have a high compression engine in their now but its running off a lower lq4 tune.

 

So its not necessary in any way to get the 02 computer?

 

nope..

 

I am surprised it dynoed sl low since both engines were 6.0's. I understand the LQ4 is down about a point in compression but I wouldn't think the AFR would be so off the computer couldn't compensate for most of it with the stock tune.
Anyway, a custom tune will do you wonders.

 

higher compression motor with lower compression tune. Maybe you had **** loads of kr and subsequent timing being pulled? 99's are known for stupid kr already, imagine picking up the compression.

 

Good point.

 

he has a 2500 so he's dynoing through a 4l80 and 12 or 14 bolt i dont rem. but thats why its lower too

 

i dunno bout 99 but i know later years didnt go into power enrichment at wot for 60 seconds

 

The 99 Operating system is not supposed to be that great. See if your tuner can load a 2002 Operating system and go from there.

Jeff