XR265HR in a 5.3 dyno graph and thoughts
02-22-2009, 11:02 AM
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XR265HR in a 5.3 dyno graph and thoughts
I purchased my 2WD 06 Silverado with the 5.3L engine to split the daily driven miles between it and the GTO and to tow and haul my quad every once in a while. Of course since it's LS1 based and I can't leave anything alone I set to find a good camshaft for my intended purpose. It needed to idle well with the stock converter, not tank my gas mileage, and not kill the low end torque around 2000 rpm since that's where it normally cruises when towing. The biggest thing I have noticed over the years with the 5.3L engines in the trucks is how quickly they fall off up top. The cam in this thing is like the peanut cam back in the 305 tpi days, it sucks. After running the numbers I thought I had found a decent off the shelf cam from Comp for just my intentions.
54-412-11 XR265HR 265/271 advertised 212/218 @ .050 .522/.529 114° LSA
I originally just did some small things to the truck like running an off-road pipe with the factory manifolds and replaced the factory muffler with a magnaflow and tuned it just with 87 octane because I have yet to see 91 oct provide much benefit on the lower compression truck motors. Trust me, I've tried and it hardly makes a difference at 9.5:1 compression. This was my baseline in the graph to follow. I got a screaming deal on a set of pacesetter longtubes with off-road y pipe so I installed those along with Comp cam I listed above. I brought it down to the dyno yesterday to do a follow up and see what gains would be had from the longtubes and the tiny little cam and I was happy with the results. All dynos were done in 2nd gear with shitty 3.23s.
All in all I am happy with the end results as it really didn't lose anything down low around 2000 rpms and it just added up top tremendously. Optimal shift points are going to be around 6300 rpm with this setup so it doesn't have to spin to the moon to stay in it's powerband. I am running 7.40 hardened pushrods and 918s even though the valve springs are kind of overkill for such a small cam. At the peaks it gained 44 rwhp and 19 rwtq but that doesn't really tell the story. In the higher RPM areas it gained almost 60 rwhp and 55 rwtq. Now that's something you can really feel. Total timing up top was around 26 degrees and it would accept more, just didn't make any more power and it wasn't pinging so it's just limited by the combo (compression, cam, etc).
54-412-11 XR265HR 265/271 advertised 212/218 @ .050 .522/.529 114° LSA
I originally just did some small things to the truck like running an off-road pipe with the factory manifolds and replaced the factory muffler with a magnaflow and tuned it just with 87 octane because I have yet to see 91 oct provide much benefit on the lower compression truck motors. Trust me, I've tried and it hardly makes a difference at 9.5:1 compression. This was my baseline in the graph to follow. I got a screaming deal on a set of pacesetter longtubes with off-road y pipe so I installed those along with Comp cam I listed above. I brought it down to the dyno yesterday to do a follow up and see what gains would be had from the longtubes and the tiny little cam and I was happy with the results. All dynos were done in 2nd gear with shitty 3.23s.
All in all I am happy with the end results as it really didn't lose anything down low around 2000 rpms and it just added up top tremendously. Optimal shift points are going to be around 6300 rpm with this setup so it doesn't have to spin to the moon to stay in it's powerband. I am running 7.40 hardened pushrods and 918s even though the valve springs are kind of overkill for such a small cam. At the peaks it gained 44 rwhp and 19 rwtq but that doesn't really tell the story. In the higher RPM areas it gained almost 60 rwhp and 55 rwtq. Now that's something you can really feel. Total timing up top was around 26 degrees and it would accept more, just didn't make any more power and it wasn't pinging so it's just limited by the combo (compression, cam, etc).
Last edited by NicD; 08-15-2009 at 08:31 PM.
02-22-2009, 11:21 AM
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Oh yea, a little bit about the idle quality...
This thing idles at the stock RPMs nicely. Raising the idle speed just isn't necessary and neither is throwing in more idle timing. I like the little bit of lope it has at the stock values. It idles with plenty of vacuum as well, around 50 kpa. Maybe I will try to grab a sound clip later but my good mic is nowhere to be found right now and using the shitty mic built in to my video camera isn't going to sound accurate.
This thing idles at the stock RPMs nicely. Raising the idle speed just isn't necessary and neither is throwing in more idle timing. I like the little bit of lope it has at the stock values. It idles with plenty of vacuum as well, around 50 kpa. Maybe I will try to grab a sound clip later but my good mic is nowhere to be found right now and using the shitty mic built in to my video camera isn't going to sound accurate.
02-22-2009, 11:29 AM
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I purchased my 2WD 06 Silverado with the 5.3L engine to split the daily driven miles between it and the GTO and to tow and haul my quad every once in a while. Of course since it's LS1 based and I can't leave anything alone I set to find a good camshaft for my intended purpose. It needed to idle well with the stock converter, not tank my gas mileage, and not kill the low end torque around 2000 rpm since that's where it normally cruises when towing. The biggest thing I have noticed over the years with the 5.3L engines in the trucks is how quickly they fall off up top. The cam in this thing is like the peanut cam back in the 305 tpi days, it sucks. After running the numbers I thought I had found a decent off the shelf cam from Comp for just my intentions.
54-412-11 XR265HR 265/271 advertised 212/218 @ .050 .522/.529 114° LSA
I originally just did some small things to the truck like running an off-road pipe with the factory manifolds and replaced the factory muffler with a magnaflow and tuned it just with 87 octane because I have yet to see 91 oct provide much benefit on the lower compression truck motors. Trust me, I've tried and it hardly makes a difference at 9.5:1 compression. This was my baseline in the graph to follow. I got a screaming deal on a set of pacesetter longtubes with off-road y pipe so I installed those along with Comp cam I listed above. I brought it down to the dyno yesterday to do a follow up and see what gains would be had from the longtubes and the tiny little cam and I was happy with the results. All dynos were done in 2nd gear with shitty 3.23s.
All in all I am happy with the end results as it really didn't lose anything down low around 2000 rpms and it just added up top tremendously. Optimal shift points are going to be around 6300 rpm with this setup so it doesn't have to spin to the moon to stay in it's powerband. I am running 7.40 hardened pushrods and 918s even though the valve springs are kind of overkill for such a small cam. At the peaks it gained 44 rwhp and 19 rwtq but that doesn't really tell the story. In the higher RPM areas it gained almost 60 rwhp and 55 rwtq. Now that's something you can really feel. Total timing up top was around 26 degrees and it would accept more, just didn't make any more power and it wasn't pinging so it's just limited by the combo (compression, cam, etc).
54-412-11 XR265HR 265/271 advertised 212/218 @ .050 .522/.529 114° LSA
I originally just did some small things to the truck like running an off-road pipe with the factory manifolds and replaced the factory muffler with a magnaflow and tuned it just with 87 octane because I have yet to see 91 oct provide much benefit on the lower compression truck motors. Trust me, I've tried and it hardly makes a difference at 9.5:1 compression. This was my baseline in the graph to follow. I got a screaming deal on a set of pacesetter longtubes with off-road y pipe so I installed those along with Comp cam I listed above. I brought it down to the dyno yesterday to do a follow up and see what gains would be had from the longtubes and the tiny little cam and I was happy with the results. All dynos were done in 2nd gear with shitty 3.23s.
All in all I am happy with the end results as it really didn't lose anything down low around 2000 rpms and it just added up top tremendously. Optimal shift points are going to be around 6300 rpm with this setup so it doesn't have to spin to the moon to stay in it's powerband. I am running 7.40 hardened pushrods and 918s even though the valve springs are kind of overkill for such a small cam. At the peaks it gained 44 rwhp and 19 rwtq but that doesn't really tell the story. In the higher RPM areas it gained almost 60 rwhp and 55 rwtq. Now that's something you can really feel. Total timing up top was around 26 degrees and it would accept more, just didn't make any more power and it wasn't pinging so it's just limited by the combo (compression, cam, etc).
02-22-2009, 11:40 AM
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Well the peak right now is around 5700-5800 rpm so it's already below 6000 rpm. If I was going to lower the LSA a bit I would probably increase the duration a tad as well. Since the factory cam is so small even a small aftermarket camshaft like this one makes a world of difference up top. I think if you were to go any bigger it would make the bottom end suffer.
02-22-2009, 11:44 AM
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Well the peak right now is around 5700-5800 rpm so it's already below 6000 rpm. If I was going to lower the LSA a bit I would probably increase the duration a tad as well. Since the factory cam is so small even a small aftermarket camshaft like this one makes a world of difference up top. I think if you were to go any bigger it would make the bottom end suffer.
