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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
 

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Discussion Starter #3
1hot12c: Are you sure you don't mean the 05 / 06 throttle bosy is 85mm? I doubt that the 03 /04 LM4 throttle body is that large, but I don't have time to resarch it right now.

Jim G
 

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The 03-04 SSR has a 78mm while the 05-06 has the 90mm. The hard part will be figuring out how to make the SSR computer read the new throttle body. I will be working with Jim on this as we strive to get the potential out of the 5.3. I will be swapping my throttle body for a polished C6 Throttle body which is the same but will polish up nicer (all aluminum), maybe we can use my old throttle-body to see what we can get out of the change also.
 

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Discussion Starter #6
Thanks, 2205ssr6speed.

The 90 mm throttle body has 33% more cross-sectionl area than the 78mm one does, because cross-sectional area is prprotional to the SQUARE of the diameter, so you can see that this is a pretty significant upgrade in raw flow capability.

Note that the stock 05 / 06 LS2 does indeed make about 30% more power than the stock 03 /04 LM4, so the 33% increase in air flow IS needed. In fact, the stock 78mm may already be a restriction on my naturally aspirated engine, as that engine now makes about teh same peak power as a stock 05 / 06. The 90mm would probably indeed help with even more air being flowed with the supercharger.

Jim G
 

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so.... Jim....

Brian's motor has a nice cam and the large throttle body but none of the other mods yours has so...
without the other mods it wont rev as high- right?
does your top end flow better although his cam is 'radicaler'
is it a good choice? what influenced you?:flag
 

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Discussion Starter #10
mikepowell said:
Brian's motor has a nice cam and the large throttle body but none of the other mods yours has so...
without the other mods it wont rev as high- right?
does your top end flow better although his cam is 'radicaler'
is it a good choice? what influenced you?:flag
Because Brian's is already supercharged, it is hard to compare his dyno cruve to mine. I would love to have see his PRE-supercharged dynoi curve, so I can see exactly what happened after he added the supercharger, and then the 90mm throttle body (he did the throttle body separately later).

His exhaust is definitiely a cork right now, and was also one before he supercharged.

Joe has also pointed out that a "more radical" cam is not such a great idea with a supercharger - it is easy to go a bit too far to where you get too much loss of combustible mixture due to the valve overlap. He tells me that the 2002 Z06 cam I have in mine is one of the better cams for supercharging - the supercharged 02 Z06s have a great track record. Brian's cam is probably better than mine, as it is slightly more aggressive, but not that much, and as you can see from the results, not aggressive enough to have problems during the valve overlap part of the cycle.

I was not thinking supercharging when I did my cam. I had simply done a lot of detailed research and concluded that the 02 (NOT 2001) Z06 cam is a particularly good one in the Gen III engines, and Will Handzel's book confirmed that for me.

Will's book actually understates its impact because like Brian, Will used a mere catback exhaust in his dyno test. That limited his results to about 39 hp more at the crank due to the cam, which is about 32 or 33 at the rear wheels. I actually got 79 hp when I installed BOTH the cam and the exhaust. I had earlier gotten only about 10 hp at peak with the exhaust, but torque gains of 30 to 40 ft lb in the mid range, which told me the engine was gasping for air at the top end and needed a better cam than the "truck" cam. However, I was surprised at HOW effective the Z06 cam and true dual exhaust were together. This is the "synergy" I talk about in my book, that occurs when good mods are simultaneously combined.

I was picturing 430 to 450 rwhp from my engine with the supercharger on it, but Brian's results make me wonder if the reality might actually be a bit better.

Jim G
 

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JimG - I think that the 430-450 will be pretty close considering the fact that you are still running the 78mm throttle body. I would not recommend doing the throttle body and supercharger at the same time, it is easier to build the program that you will need a step at a time. I will send you my throttle body when my new 1 is ready (it will be at the polishers for a week too), so about 2 weeks.
 

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The only reason that I am changing my throttle body for the C6/GTO throttle body is that the entire outer housing is aluminum and I want to polish it to match the rest of the under-hood on my SSR. I may run into clearance issues with the shaft and the solenoid on the side of the throttle body so please don't try this at least until I figure it out. Thanks.
 

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Discussion Starter #13
2005SSR6speed: I agree that the 90mm throttle body has to be done later, for several reasons:

- Isolate its effect from the supercharger effect alone
- Make tuning the supercharger easier and more predictable
- Make diagnostics of any problems easier because fewer variables
- I am going to be in the middle of moving out of my home (it sold finally), either into a temp location or into a property we are trying to buy: cheap doublewide poorly maintained but on a beautiful view lot with great well, oversize septic, STEEL 3 car carport with lots of electrical power, and legal to have my own on-site shooting range (You have to keep your priorities straight . . .:) )

Jim G
 

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cam selection

Cam selection for supercharged applications is very important. In my experience lobe centerline is of major importance. Wide degree of lobe centerline is needed.
 

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Calcustom - You are correct, because if the lobe center-lines for the intake and exhaust are too close they will bleed off boost.

JimG - I like the 3 car port with lots of electrical, is it enclosed? The shooting range would be nice too, how many acres is it? We will keep or fingers cross that it all closes for you.
 

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Discussion Starter #17
The carport currently has 3 sides, but we plan to add a front wall with garage doors if we successfully close on the property (the sellers have issues).

The lot is 2.7 acres, and much of it is in a wooded canyon, where shooting will be quiet and safe into the canyon wall.

Jim G
 

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SSRRev - The 6 speed is definitely up to the task and so is the 14 bolt semi-floater rear axel. I can see maybe needing a clutch if you are going to do a lot of knee jerk launches at the drag strip, but that is about it.
 

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I Installed everything but the Kitchen Sink to make 500 RWHP!!!

JIM ! DID YOU FORGET ABOUT ME ......paulny????

You write about this like it is something new??/

Please pull out all our earlier correspondence and read it again! I went to hell and back to get my LM4 built to make the most RWHP and Torque! And you gave me a hard time about exhaust and lack of air.

Since I wrote the club last I worked with the CEO of K&N to prefect a really neat cold air induction system and had my SSR over to the torque convertor place that built it. Turns out I got the wrong info from the Chevy dealer, my convertor is much smaller then the stock one and they dynoed it "LOCKED UP!" and my SSR put out over 500 RWHP!!

I learn more and more everyday about my SSR and LM4, I never stop reading and writing companies.

I just get a bit upset (like you) when I ready posts like your last one about your friends truck!! You can't just stick a MagnaCharger on any engine and expect to make big HP without changing the heads, cam, a set of headers ( catbacks DO work, maybe not as good) and a long dyno secession! Forget that hand held unit that's just for the guys that only put the supercharger on with the LARGE pulley, as of now I am down to 2.5 dia and about 15 pounds boost. That's with my LM4 storked 9mm (350 cubic inches) and 9:1 compression and have no problems hitting 6800 RPMS!

I can't wait to get to New Jersey Englishtown in the spring and get my times. I can cross my heart and hope to dye my SSR will turn some really low ET's next spring.

My only problem is finding better tires (street strip) that will fit GM's stock chrome rims.

King Regards,
Paulny
 
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