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New to this forum. Think I may have the last 6.0 Avalanche to leave the line. But this post is about my 2003 4x4 Avalanche recently converted from the 5.3 to a GMPP LS376/480 and I'm wondering if this would be normal powertrain loss? Bad Dyno? or a tuning problem? I went from 480 peak at 5950rpm at the crank to 321 rwhp peak at 5350rpm and also lost about 100 lbs of torque.
wow! thats alot of horses lost, had your trans serviced lately? and did you put a new converter in while you were at it?
I put in a new converter, Transgo shift kit, Vette servos, and Kevlar Band.
Whos your tuner?
I used Hesco in Birmingham. Guys seemed to know what they were doing.
Never heard of them. BUt seems like something is wrong somewhere.
:wave: welcome, im from birmingham as well...
and ive actually had HESCO tune my old truck and my dads yukon. im now tunning my yukon myself with the help of some friends...
Jon did the tunning id assume? with my dads yukon the tune was good from what i can tell, but very very conservative FWIW.
hopefully theres something more to it than the tune, cause itll be tough to get another 100hp out of it. whos dyno did you use?
Something is obviously wrong, look into transmission slipping or if get a second dyno reading to be sure.
That power is close to what a hot 5.3L puts out.
As long as the a/f ratio is good, timing is good with no KR, the tune is probably good enough, cause like it was said, there isn't that much power left in the tune if it's close.
Did anything else change besides the engine?
Jon did do the tune and seemed to really know his stuff. It was actually a dyno tune so they also did the dyno. If I can figure out how to get the graph below 19.5 kb I'll post it and see if some of you guys can make sense of the outcome. It shows some strange things, like torque rated above HP and a 50+ HP and FtLb dip at 2500 rpm. At this point I'm thinking that something I've done on the install is the limiting factor but I can't figure out what. Either that or GMPP seriously overrated this engine. It does sound great and throttle response is awesome.
By the way, how do your tuners dyno trucks without reaching speeds beyond the tires rating?
A/F stays consistent at 12.4 up to about 5500 rpm and then drops slightly above that. Tranny is a GM Certa with about 5k on it. Convertor(2300 because its still a towing 4x4), servos and shift kit were done at the time of the engine swap. Kevlar band was added after the first dyno attempt smoked the stock band. Swap required Lingenfelter 58/24x module to work with the Gen III computer. Also, added American Racing LT 1 7/8 primaries and Efans for the swap.
Wow I would think youd be making gobes of power.
Also replaced the stock air box with the GMPP CAI and had to use the vette accessories since the truck accessories wouldn't clear the intake on the new motor.
try to upload the graph to photobucket or a site like it if the uploader on this site isnt working. it sounds like there is some weird stuff goin on.
id say Gm overrated that motor. i do believe that rating is with no accesories. Also 12.4 is leaving a some ponies to be unspoken for. that combo should do around 380-400 realistically
Ya'll I was thinking that na motors performed best 12.8-13.2 sounds a little rich but still kinda weary of that trans, what gears do you have and tire size.
BB
Sending you a PM,I am from Birmingham and I know the best tuner in the area,ive tryed to tell Mitch aka sprayeddenali about the tuner,a friends truck with almost the same mods as Mitch(friends truck only runs a 125 Zex kit) is MUCH faster on a worse track in BAD weather(Cayman Islands) and my friend tunes himself and is inexperienced.The best tuner in Birmingham street tuned my Escalade EXT(only bolt ons at the moment,I have cnc l92's to go on it and a 408 short block being built) and my OBS 454 Vortec truck(45 rwhp gain on his dyno)He does all my newer American car tunes and I try to send any local LSx/Mustang guys I can his way because he is that good!!.And I tune my stock ecm Grand National,my FAST XFI equipped Grand National,and my 2005 E55 all by myself.I am more than capable of learning to tune the LSx but the guy does such great work and is so cheap,I am not going to waste my time!Quote:
Originally Posted by Lucille
Hesco's Land and Sea dyno reads a bit low as well.They are good people and do great work albeit very costly.I have personally had them do a few jobs for me when I was younger and didnt know much about working on cars,they all turned out great.I also know the manager Jeff personally from back in the day street racing.Hell,back then he was just a tech.We do have talented people here in town,most of them being 1 man shows though!
CHECK YOUR PM's IF YOU WANT TO FIND THE HIDDEN HP!!!
Trans worries me to, but with less than 5k on it I had to take the chance. Isn't the 80 longer than the 4L60? I'm running 3.73 gears and 275/17s. Also, the 12.4 was a typo the dyno actually shows 12.14.Quote:
Originally Posted by 96/chevy/pu
3rd shot at posting dyno