2003 Chevy Silverado 1500 LT 5.3L LM7 - COMP Cams XFI Xtreme 54-450-11 upgrade...

Hello Anyone -
Just dropped a COMP Cams XFI Xtreme ( 54-450-11 ) into my very stock 2003 Chevy Silverado 1500 LT 5.3L LM7 ( along with some performance springs, lifters, push rods and rocker arms ) and things just don't feel right while driving ( sounds pretty cool though ), anyway I'm one of those fortunate ( ? ) souls that has more money than time and would be oh so willing to pay for someone to take a look at my log file and get me pointed in the right direction for getting this thing tuned at least enough to drive it 3 hours to a chassis dyno shop in Idaho... 😅

Again, everything is stock on this truck ( including the o2 sensors and torque converter ) and the current tune is totally stock as well!
Also, I just received my MPVI3 device from HP Tuners a couple of days ago along with 2 credits so not real experienced in using it just yet 😉

Kindest regards and thanks in advance - Todd Oberg

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I'm a newbie too! I have been looking at tunes for long time because of my transmission building, just never made changes. I looked at your log and only one thing came to mind. It is running slightly rich, but your LTFT are under 10% most of the time. I think I would start with VE test. It's a mild cam and probably just needs a bit more air.
I use https://www.otctools.com/ve to find the #'s. but I think HPtuners uses different 3's to claculate. I read somewhere on here about the VE testing and adjusting MAF calculations. I think it was in the Stickies where they ask you to read here first...
Also as a transmission builder I like to see MAF load on the parameters. LOL

Found it! It was in the stickies at the top of this section labeled "Read Me" but here that link.

https://forum.hptuners.com/showthrea...he-VE-table-do

You should read through all of those in that section. You don't need a chassis dyno to tune, it's just faster, because your having it done by a pro. Real world tuning with a wide band O2 is next and lastly real world testing with your stock narrow band. I have friends that tune. The 2 that are the most knowledgeable about it, said buy a tank of gas and we will have some fun doing some tuning...

Hey, just got my mpvi3 as well and doing similar work as you to my 2000... I would like to share files if you have any luck. I have been looking all over the repository and only finding stock tunes... not sure yet but I would really like to start put comparing a file to a similar truck so I can understand the diff between stock etc...

Haha, thanks for the reply Tranzman! :)
Just got home but will dig in and read deeper tomorrow...

BROWNSTONE: I was honestly surprised that there wasn't someone somewhere that had dropped a similar cam in a 5.3L LM7, like you said just stock tunes. :confused:
When I get this thing dialed I will absolutely share my tune,

Only stock tunes allowed in the repository now. I choose to blame it on the brodozer diesels for attracting all the recent negative attention. Jerks.

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Originally Posted by blindsquirrel

Only stock tunes allowed in the repository now. I choose to blame it on the brodozer diesels for attracting all the recent negative attention. Jerks.

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That sucks! ☹

Well a couple rambling thoughts about it.

Not having modified tunes in the repository isn't a big deal. The reason people whine about it is because they think that if their car has parts X, Y and Z, then they can just find a file from another car with X, Y and Z, flash that file to their PCM, and then they won't have to do any work or learn anything. Modified files are all over the forums, you just have to look for them. And by reading the threads that go with the files you see the process by which a particular file arrived at its current state - and whether that was the right way to do it and whether it worked - or not. A file from the repository had no context for how or why, and no log files to show what that tune file resulted in.

There is no free lunch. Some people will see junk mail that says 'LIMITED TIME ONLY ENTER NOW FOR A CHANCE TO COMPETE FOR AN OPPORTUNITY TO GET UP TO 10% DISCOUNT ON A FREE LUNCH!' and their brain only registers 'hey! free lunch!' Don't be one of those people.

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Originally Posted by iamtdoberg

Hello Anyone -
Just dropped a COMP Cams XFI Xtreme ( 54-450-11 ) into my very stock 2003 Chevy Silverado 1500 LT 5.3L LM7 ( along with some performance springs, lifters, push rods and rocker arms ) and things just don't feel right while driving ( sounds pretty cool though ), anyway I'm one of those fortunate ( ? ) souls that has more money than time and would be oh so willing to pay for someone to take a look at my log file and get me pointed in the right direction for getting this thing tuned at least enough to drive it 3 hours to a chassis dyno shop in Idaho... 😅

Again, everything is stock on this truck ( including the o2 sensors and torque converter ) and the current tune is totally stock as well!
Also, I just received my MPVI3 device from HP Tuners a couple of days ago along with 2 credits so not real experienced in using it just yet 😉

Kindest regards and thanks in advance - Todd Oberg

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You can try this file. I added idle rpm, base running airflow, frictional airflow delay, added spark, removed PE delays, removed the 98mph speed limiter, and brake torque management. Also removed some fuel at idle. You can drive it to the dyno on the stock tune with that cam, but it would be much better with this one. It's safe and mild. Good luck.
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Originally Posted by Matt Vardaman

removed the 98mph speed limiter

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https://en.wikipedia.org/wiki/Critical_speed

http://www.wallaceracing.com/driveshaftspeed.php

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Originally Posted by Matt Vardaman

You can try this file. I added idle rpm, base running airflow, frictional airflow delay, added spark, removed PE delays, removed the 98mph speed limiter, and brake torque management. Also removed some fuel at idle. You can drive it to the dyno on the stock tune with that cam, but it would be much better with this one. It's safe and mild. Good luck.
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Awesome, thanks Matt! 🤠

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Originally Posted by blindsquirrel

https://en.wikipedia.org/wiki/Critical_speed

http://www.wallaceracing.com/driveshaftspeed.php

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I suppose I should have asked if he has an aluminum driveshaft or the two piece steel shaft with center-support bearing. When using the Wallace calculator, does the length for critical speed only apply to each individual shaft length? I did read your post about this issue for you vehicle.

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Originally Posted by Matt Vardaman

I suppose I should have asked if he has an aluminum driveshaft or the two piece steel shaft with center-support bearing. When using the Wallace calculator, does the length for critical speed only apply to each individual shaft length? I did read your post about this issue for you vehicle.

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I am 99.95% certain, the tubes would need to be calculated independently since they are separated by a semi rigidly mounted bearing and U-joint. Each shaft will have its own critical speed, the lower of which being the critical speed for the driveshaft assembly.

I spent some time calculating this when I put 5.13s in my Van when it still had the 350 and the 9.5 14-bolt. In my case the critical RPM was calculated at 5,161 rpm. That was only ~94 mph, but I had the limiter at 98 mph and never had an issue. Now that I have the 383 and a 10.5 14-bolt with 3.73s; the calculated critical speed is just shy of 130 mph. Speed limiter is set for the 115-mph limit on the tires. OEM shaft is 79.25" long, 0.087" thick aluminum and a 5" OD. Remember this calculator is an approximation not an absolute. The biggest surprise to me was a torsional yield calculation of over 7,500 ft/lbs for the stock driveshaft.

The limiter is more for the speed rating of the tires and to appease the government NTHSA guys that don't want a ~3+ ton pickup truck moving a bed full of cargo at ~140 mph down the highway.

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Originally Posted by Fast4.7

I am 99.95% certain, the tubes would need to be calculated independently since they are separated by a semi rigidly mounted bearing and U-joint. Each shaft will have its own critical speed, the lower of which being the critical speed for the driveshaft assembly.

I spent some time calculating this when I put 5.13s in my Van when it still had the 350 and the 9.5 14-bolt. In my case the critical RPM was calculated at 5,161 rpm. That was only ~94 mph, but I had the limiter at 98 mph and never had an issue. Now that I have the 383 and a 10.5 14-bolt with 3.73s; the calculated critical speed is just shy of 130 mph. Speed limiter is set for the 115-mph limit on the tires. OEM shaft is 79.25" long, 0.087" thick aluminum and a 5" OD. Remember this calculator is an approximation not an absolute. The biggest surprise to me was a torsional yield calculation of over 7,500 ft/lbs for the stock driveshaft.

The limiter is more for the speed rating of the tires and to appease the government NTHSA guys that don't want a ~3+ ton pickup truck moving a bed full of cargo at ~140 mph down the highway.

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I'll not be hitting the critical speed limit of mine anytime soon. It was something like 10,000rpm on the front shaft (shorter) and 7200rpm on the rear shaft. 115-120mph is about the fastest I ever go. I usually just move the speed limiter out of the way, but I drive reasonably down the highway. I go to the drag strip about ten times a year. We only have 1000' tracks here, so I'm only at around 90mph.

And the stock shaft in my LWB 2WD Envoy has a (internet) critical speed of 108; with my slightly shorter tires crit is moved down to 100.8. Some trucks will have lots of safety margin, some have nearly none at all.

I've been turning off speed limiters on GM Trucks and SUVs since 2004. Probably over 10000 vehicles. I have yet to hear of anyone exploding a driveshaft. Over 50% of the time that is the first question I am asked. I always tell the customers that the speed limiter is there for driveshaft safety, not tire ratings which is what most all assume it is there for. I tell them short bursts over 100 mph are probably going to be OK but don't drive for 30 minutes at 130 mph. I also see plenty of trucks at the track running over 100 mph 1/4 mile runs and haven't seen any drive shafts letting go there either. Then again they are only exceeding 100 mph for a short time.

Ive seen several driveshafts blow. they were the crappy aluminum ones. A few of the trucks were bone stock and they come apart with the stock top speed limiter.