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Some of you know by now that I just ordered a Magnacharger kit from our very own 2005SSR6speed (Joe).
Joe and I have been wondering what a properly cammed 5.3 liter LM4 might produce when supercharged. Since my 04 SSR has a true dual exhaust, Dynatech Supermaxx headers, and the cam and valvetrain from an 02 Corvette Z06, we figure it is a prime test bed.
A day or two ago, Joe brought to my attention the results that “Brian” at Magnacharger got with his own 2004 Chevy Crew Cab with the same 5.3 liter LM4 engine. Brian published both his mods and his dyno results on a performance truck website recently. Both the mods and the results really caught my attention.
The ONLY mods that Brian did were:
- Catback exhaust (single not dual, and NO headers – he has stock exhaust manifolds)
- AirAid air intake (small impact, similar to a K&N kit on our SSRs)
- Lingenfelter GT2-3 cam
- 90mm throttle body
You can pretty much ignore the catback and air intake, as their impact is not big. Focus on the cam and throttle body.
The GT2-3 cam has specs that are a bit more aggressive than the Z06 valvetrain I have in my vehicle:
Spec / Z06 / GT2-3
Intake duration / 204 / 207
Exhaust duration / 218 / 220
Lift – intake / .555 .573
Lift – exhaut / .551 / .580
Lobe separation / 117.5 / 118.5
Note the subtle differences in duration, but significant differences in lift. Apparently, the LM4, with its mild compression has a head shape that will tolerate the .573 and .580 lift of the GT2-3. (That cam was designed for the LS1 series of engines).
The 90mm throttle body is much larger than the stock one (I can’t remember the size of the stock one and don’t have the specs here with me).
The shocker is the results. Remember, Brian has really crappy exhaust yet.
Brian got 505 hp at 6000 rpm out of this setup, and 476 ft lb of torque at 4750 rpm! Apparently, the testing was repeated days later to validate it, and was consistent. Now, this was on the Magnuson in-house dyno, which runs a little on the high side as far as I can tell, but guys, this is 35 hp MORE than Joe got on his own 05 supercharged SSR with its 13% larger LS2 engine, on the same dyno. Got your attention?
Check out the attached graph that compares various supercharged SSRs to Brian’s Crew Cab. It will stun you.
Look at the shape of his power curve. It is reasonably comparable to the larger supercharged LS2s at low rpm, but takes off compared to them above about 4000 rpm, and leaves them in the dust at 6000 rpm. The torque peak is at 4750 too, which means that despite the “inferior” heads on the LM4 (compared to the LS2) AND the crappy exhaust, it is BREATHING. In fact, its torque peak is at about 1000 rpm higher than the blown LS2s. We are talking a real revver here guys.
It drops just a bit at 6500, but that’s likely the exhaust back pressure finally killing it. Make you wonder what it would do with a real exhaust – like the one on my own 04SSR.
Think about this a bit. Brian’s crew cab truck is putting about the same power to the ground, through an inefficient automatic transmission driveline, as a new stock 7 liter Corvette makes at the CRANK. Even discounting the Magnuson dyno data down say 5%, this puppy is still making more than 480 hp at the rear wheels and at LEAST 580 at the crank – maybe as much as 625 hp at the crank.
The fact that the torque peak is still about where the cam would put it in a naturally aspirated SSR (see the black graph line for my own naturally aspriated 04 SSR on the graph, with a similar cam) is very significant. It means that unlike the LS2, whose torque peak moved notably downward after supercharging, the addition of the blower to the LM4 did NOT bring about a swift encounter with a serious airflow “cork”. Why? Lots of variables could have an impact, including:
- Smaller displacement means less air sucked per individual piston intake stroke
- Smaller valves and smaller ports means higher air flow velocity
I analyzed the graph numerically. Brian’s LM4 makes ON AVERAGE more than 50% more torque and consequently 50% more power at every rpm point than my own LM4 with similar cam makes. Can you imagine how excited this gets me about what my own SSR will do, with its superior exhaust, after my supercharger is installed?
Examine closely the exact shape of Brian’s torque curve and my own naturally aspirated torque curve. See how the shape is so similar until 6000 rpm, were his starts to fall faster but mine keeps going? That says good things about the potential for my engine above 6000 rpm once it too is supercharged.
One important item: Brian attributed a LOT to that 90mm throttle body. The implication was that the stock throttle body became a cork when the engine was supercharged. So, I may need to look at a 90mm throttle body . . .
This is getting interesting.
Those of you with 03 and 04 SSRs who are thinking of trading for an 06 purely to get the power, might want to wait and see what supercharged LM4s can do. Brian’s supercharged LM4 crew cab has, to my knowledge, more power than any of the supercharged LS2s whose dyno curves have been posted on this website. I see friendly competition coming . . .
Jim G
Joe and I have been wondering what a properly cammed 5.3 liter LM4 might produce when supercharged. Since my 04 SSR has a true dual exhaust, Dynatech Supermaxx headers, and the cam and valvetrain from an 02 Corvette Z06, we figure it is a prime test bed.
A day or two ago, Joe brought to my attention the results that “Brian” at Magnacharger got with his own 2004 Chevy Crew Cab with the same 5.3 liter LM4 engine. Brian published both his mods and his dyno results on a performance truck website recently. Both the mods and the results really caught my attention.
The ONLY mods that Brian did were:
- Catback exhaust (single not dual, and NO headers – he has stock exhaust manifolds)
- AirAid air intake (small impact, similar to a K&N kit on our SSRs)
- Lingenfelter GT2-3 cam
- 90mm throttle body
You can pretty much ignore the catback and air intake, as their impact is not big. Focus on the cam and throttle body.
The GT2-3 cam has specs that are a bit more aggressive than the Z06 valvetrain I have in my vehicle:
Spec / Z06 / GT2-3
Intake duration / 204 / 207
Exhaust duration / 218 / 220
Lift – intake / .555 .573
Lift – exhaut / .551 / .580
Lobe separation / 117.5 / 118.5
Note the subtle differences in duration, but significant differences in lift. Apparently, the LM4, with its mild compression has a head shape that will tolerate the .573 and .580 lift of the GT2-3. (That cam was designed for the LS1 series of engines).
The 90mm throttle body is much larger than the stock one (I can’t remember the size of the stock one and don’t have the specs here with me).
The shocker is the results. Remember, Brian has really crappy exhaust yet.
Brian got 505 hp at 6000 rpm out of this setup, and 476 ft lb of torque at 4750 rpm! Apparently, the testing was repeated days later to validate it, and was consistent. Now, this was on the Magnuson in-house dyno, which runs a little on the high side as far as I can tell, but guys, this is 35 hp MORE than Joe got on his own 05 supercharged SSR with its 13% larger LS2 engine, on the same dyno. Got your attention?
Check out the attached graph that compares various supercharged SSRs to Brian’s Crew Cab. It will stun you.
Look at the shape of his power curve. It is reasonably comparable to the larger supercharged LS2s at low rpm, but takes off compared to them above about 4000 rpm, and leaves them in the dust at 6000 rpm. The torque peak is at 4750 too, which means that despite the “inferior” heads on the LM4 (compared to the LS2) AND the crappy exhaust, it is BREATHING. In fact, its torque peak is at about 1000 rpm higher than the blown LS2s. We are talking a real revver here guys.
It drops just a bit at 6500, but that’s likely the exhaust back pressure finally killing it. Make you wonder what it would do with a real exhaust – like the one on my own 04SSR.
Think about this a bit. Brian’s crew cab truck is putting about the same power to the ground, through an inefficient automatic transmission driveline, as a new stock 7 liter Corvette makes at the CRANK. Even discounting the Magnuson dyno data down say 5%, this puppy is still making more than 480 hp at the rear wheels and at LEAST 580 at the crank – maybe as much as 625 hp at the crank.
The fact that the torque peak is still about where the cam would put it in a naturally aspirated SSR (see the black graph line for my own naturally aspriated 04 SSR on the graph, with a similar cam) is very significant. It means that unlike the LS2, whose torque peak moved notably downward after supercharging, the addition of the blower to the LM4 did NOT bring about a swift encounter with a serious airflow “cork”. Why? Lots of variables could have an impact, including:
- Smaller displacement means less air sucked per individual piston intake stroke
- Smaller valves and smaller ports means higher air flow velocity
I analyzed the graph numerically. Brian’s LM4 makes ON AVERAGE more than 50% more torque and consequently 50% more power at every rpm point than my own LM4 with similar cam makes. Can you imagine how excited this gets me about what my own SSR will do, with its superior exhaust, after my supercharger is installed?
Examine closely the exact shape of Brian’s torque curve and my own naturally aspirated torque curve. See how the shape is so similar until 6000 rpm, were his starts to fall faster but mine keeps going? That says good things about the potential for my engine above 6000 rpm once it too is supercharged.
One important item: Brian attributed a LOT to that 90mm throttle body. The implication was that the stock throttle body became a cork when the engine was supercharged. So, I may need to look at a 90mm throttle body . . .
This is getting interesting.
Those of you with 03 and 04 SSRs who are thinking of trading for an 06 purely to get the power, might want to wait and see what supercharged LM4s can do. Brian’s supercharged LM4 crew cab has, to my knowledge, more power than any of the supercharged LS2s whose dyno curves have been posted on this website. I see friendly competition coming . . .
Jim G
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