Stock 5.3, where are your shift points?

badfnz · December 4, 2011

I'm messing around in HP Tuners and looking at the stock shift points, they're pretty low. You guys with stockish 5.3s, where are your shift points? Any of you BB tuned guys know where your shift points are? Anyone have a dyno graph of a stock 5.3 to see where the HP peak is?

uchi · December 4, 2011

what year is your truck and what tranny do you have? when i put my tune into my truck we left the tranny shift points alone. it works well enough around town for my liking and thats with a 6 speed.

music · December 4, 2011

2010 5.3 Torque Curve: http://archives.media.gm.com/us/powertrain/en/product_services/2010/gmna/HPT%20Library/Gen%20IV/Gen%20IV%20Truck/2010_Vortec_53L_LC9_Silverado_Combo.pdf

badfnz · December 4, 2011

2011, 6L80E.

It looks like this engine peaks around 5200 rpm. That's low! Especially with the 243 heads. I can't imagine how much a cam and intake wakes these things up.

vettelovralexand · December 4, 2011

In drive, my logs show the maximum rpm to be about 6200 but I think the shift is actually set to 6k. My dyno plots show peak power at about 4750 rpm.

wavery · December 4, 2011

2011, 6L80E.

It looks like this engine peaks around 5200 rpm. That's low! Especially with the 243 heads. I can't imagine how much a cam and intake wakes these things up.

That depends on what you use the vehicle for. If you want to drag race your "TRUCK", the peak is low. If you want to work your "TRUCK", like in towing and hauling, that peak is a little high........ Sorta looks to me that the design was a compromise to satisfy the broader market.

I use my truck exclusively for towing and have never engaged in a drag race with it. I would love to have the torque peak @ ~ 2800RPM.

vettelovralexand · December 5, 2011

2011, 6L80E.

It looks like this engine peaks around 5200 rpm. That's low! Especially with the 243 heads. I can't imagine how much a cam and intake wakes these things up.

That depends on what you use the vehicle for. If you want to drag race your "TRUCK", the peak is low. If you want to work your "TRUCK", like in towing and hauling, that peak is a little high........ Sorta looks to me that the design was a compromise to satisfy the broader market.

I use my truck exclusively for towing and have never engaged in a drag race with it. I would love to have the torque peak @ ~ 2800RPM.

You must want either forced induction or very low horsepower then. Having a torque peak that low (naturally aspirated) would require a cam that would run out of steam very fast on the top end. I mean, even the 8.1L had a torque peak a little over 3k and that had peak horsepower at barely over 4k. There is a reason that engine only made 20-30 more horsepower than the current 5.3L.

wavery · December 6, 2011

You must want either forced induction or very low horsepower then. Having a torque peak that low (naturally aspirated) would require a cam that would run out of steam very fast on the top end. I mean, even the 8.1L had a torque peak a little over 3k and that had peak horsepower at barely over 4k. There is a reason that engine only made 20-30 more horsepower than the current 5.3L.

Not sure how you figure that. RPM (by itself) doesn't necessarily relate to max HP. I know of engines that achieve 10K HP @ 500RPM (not automotive engines of course).

It's easy to come up with a cam and valve configuration that will give peak torque at 2800RPM and maintain that torque through most of the maximum RPM of the engine. The maximum torque would be slightly lower than an engine that achieves max at a higher RPM. Although when towing or carrying a heavy load, achieving max torque at a lower RPM allows the ability to keep an engine at a lower RPM for longer periods of time while achieving more pulling power at that lower RPM.

There's nothing worse than having to drop the trans into a lower gear in order to achieve 4000-4500RPM to have enough torque to climb a steep grade. The engine would not be able to stay at that RPM (comfortably) for a long period of time (at least not in my truck). If the same rig were able to achieve max torque @ 2800RPM the same rig might be able to climb the same grade @ a higher speed @ a lower RPM in a higher gear and maintain that RPM for a longer period of time (more comfortably).

vettelovralexand · December 6, 2011

You must want either forced induction or very low horsepower then. Having a torque peak that low (naturally aspirated) would require a cam that would run out of steam very fast on the top end. I mean, even the 8.1L had a torque peak a little over 3k and that had peak horsepower at barely over 4k. There is a reason that engine only made 20-30 more horsepower than the current 5.3L.

Not sure how you figure that. RPM (by itself) doesn't necessarily relate to max HP. I know of engines that achieve 10K HP @ 500RPM (not automotive engines of course).

It's easy to come up with a cam and valve configuration that will give peak torque at 2800RPM and maintain that torque through most of the maximum RPM of the engine. The maximum torque would be slightly lower than an engine that achieves max at a higher RPM. Although when towing or carrying a heavy load, achieving max torque at a lower RPM allows the ability to keep an engine at a lower RPM for longer periods of time while achieving more pulling power at that lower RPM.

There's nothing worse than having to drop the trans into a lower gear in order to achieve 4000-4500RPM to have enough torque to climb a steep grade. The engine would not be able to stay at that RPM (comfortably) for a long period of time (at least not in my truck). If the same rig were able to achieve max torque @ 2800RPM the same rig might be able to climb the same grade @ a higher speed @ a lower RPM in a higher gear and maintain that RPM for a longer period of time (more comfortably).

It is relatively easy to come up with the proper cam to have a peak torque around 2800 rpm, but relatively difficult to have that same cam make good torque out past 5000 RPM without VVT(really needs to be VVT for intake and exhaust separately to be really effective, although cam advance and retard helps some) or forced induction. The closest modern day engine to what you are asking for is the Ford 4.6 and 5.4 modular truck motors. They had peak torques which were low in the RPM band (2650), but were dogs because they ran out of steam at 5k. I really don't think that the Vortec engines and transmissions are ideal for towing either, but they are certainly adequate for the person who tows 3-5k a few times a year (which I would say is more than what the average truck owner does) while still providing a quick and fuel efficient engine for those who "drag race" back and forth to work with an empty truck.