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Camaro V8 LS3 / L99 Engine, Exhaust, and Bolt-Ons Bolt-Ons | Intakes | Exhaust

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Old 09-23-2008, 05:20 PM   #1
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VVT on L99, or what?

I'm looking at the cut away illustrations of the LS3 and L99 on http://www.gmhightechperformance.com
Compare the timing gears/chain on the two engines. The LS3 cam gear looks like you'd expect, but the L99 looks much different. It's obviously more than just a timing chain cam sprocket. Is it part of the AFM system (don't think so), or some sort of VVT mechanism, or what?

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Old 09-23-2008, 06:54 PM   #2
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it is part of the AFM system but i cant explain it
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Old 09-23-2008, 07:37 PM   #3
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it is part of the AFM system but i cant explain it
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Old 09-23-2008, 07:41 PM   #4
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I can't explain it either. I thought the AFM was operated by solenoids and a valve body in the crotch of the cylinder bank. The cam "sprocket" looks like it could be one of those hydraulic cam phase changers that are used to vary timing, but of course without individual intake and exhaust cams, it would phase shift both intake and exhaust lobes simultaneously. Anyone know?

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Old 09-23-2008, 10:47 PM   #5
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The VVT and AFM are independent systems but probably work together for the best efficiency. AFM just has collapsible lifters and the cam phaser I THINK moves the intake and exhaust together. It seems REALLY expensive to have a 2 in 1 type of cam but I could be wrong. I would assume also the VVT is hydraulically operated as is the AFM is.
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Old 09-24-2008, 06:09 AM   #6
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It is possible to have a cam in cam system, and vary the intake and exhaust valve timing relative to each other, dodge does it for the new viper. However, from what I understand, the L99 simply varies the timing of the camshaft. Think of it as advancing or retarding the camshaft as the engine is running based on engine conditions. For the L99, VVT may have more to do with optimizing the engine for 4 cylinder vs. 8 cylinder operation than with anything else, but I am not too sure. If it made a big difference to fuel economy or increased performance, I would think you would have seen the VVT on the LS3.
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Old 09-24-2008, 08:24 AM   #7
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I checked the catalog and GM calls that cam sprocket a "camshaft position actuator." I found it on a '09 1500 hybrid with the 6.0 "LFA" motor. Thats the only thing I could find it on. It also shows a "actuator magnet" on the front of the timing cover.
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Old 09-29-2008, 01:49 PM   #8
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If this has been discussed I apologize(I didn't see it), but does anyone out there have concerns/issues with the L99 having the AFM and shutting down cylinders ? I KNOW the electronics/management is far better than it used to be(the Cadillac 4-6-8)-but I guess I'm too old school to accept technology such as this. I figure the more technical and advanced it is-there's just all that much more to break down and fix. Thanks for a great forum.
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Old 09-29-2008, 01:50 PM   #9
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Originally Posted by ohnonothimagain View Post
If this has been discussed I apologize(I didn't see it), but does anyone out there have concerns/issues with the L99 having the AFM and shutting down cylinders ? I KNOW the electronics/management is far better than it used to be(the Cadillac 4-6-8)-but I guess I'm too old school to accept technology such as this. I figure the more technical and advanced it is-there's just all that much more to break down and fix. Thanks for a great forum.
I imagine your concern is lag. That will not be a problem with the L99.
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Old 09-29-2008, 01:54 PM   #10
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I don't know how long AFM has been out...I want to say 4-5 years...but I've never read anything about it breaking down or failing. No articles, no recalls, no reviews, no posts...

I'm certainly no authority on the subject, but the only negative aspect to AFM I've heard reported is an awkward exhaust note when the system is engaged.
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Old 09-29-2008, 02:46 PM   #11
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Originally Posted by Dragoneye View Post
I don't know how long AFM has been out...I want to say 4-5 years...but I've never read anything about it breaking down or failing. No articles, no recalls, no reviews, no posts...

I'm certainly no authority on the subject, but the only negative aspect to AFM I've heard reported is an awkward exhaust note when the system is engaged.
It was first introuced on the Cadillac sixteen, it had 4,8,16, and 1000hp. The engine was just for testing upcoming tech particularly cylinder deactivation. Although it was a fully operational engine they stuffed it in a Suburban with a hell of a lot of effort. It's too bad they didn't build that caddy though, the sixteen would have put everything to shame period.
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Old 09-29-2008, 02:48 PM   #12
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Interesting that GM doesn't market the L99 as an AFM VVT engine even though if you're altering cam timing, that's what it is. Notice that the VVT in the 5.7 L hemi bumped it up form 340 hp to 375 and over 400 pounds torque. You'd think that if this system is slated to go in the L99, that GM would market it as such.
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Old 09-29-2008, 06:32 PM   #13
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RE: What Chevrolet calls AFM is NOT new-Cadillac had it during the early 1980s with a variable displacement engine, branded the L62 V8-6-4 engine. Introduced in 1981, this 6 Liter engine selectively activated and deactivated cylinders according to power demand. Cadillac hailed the engine as cutting-edge; but it proved unreliable and was scrapped. What goes around comes around-that's why I've been concerned about vehicles with cylinder deactivation. That's what I was trying to say-and I just hope that it's not too complex that if/when something goes wrong-it's not MORE expensive to fix than a car without AFM....Just my humble opinion; it could cause Camaro lovers to hate that feature.
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Old 09-29-2008, 07:04 PM   #14
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When I worked at a dealership, I was told by the GM reps that it is a totally different animal than what was in the Cadillac... The way that it is designed, IF it ever does malfunction, it just wont deactivate the cylindars and will stay in V8 mode... you don't have to worry about it getting stuck on just 4.
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Old 09-29-2008, 07:10 PM   #15
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Thats good to know-I'm still concerned about it's complexity. I've learned that the more complex an engine or transmission is the more it costs to fix it or deal with it. I apologize because I'm old school-the technology in the new cars both amazes me and confuses me. It's incredible what they've done with both engines/transmissions and engine management; but you can't seem to even open the hood of new cars without an engineering degree lol.
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Old 09-29-2008, 09:03 PM   #16
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Quote:
Originally Posted by ohnonothimagain View Post
Thats good to know-I'm still concerned about it's complexity. I've learned that the more complex an engine or transmission is the more it costs to fix it or deal with it. I apologize because I'm old school-the technology in the new cars both amazes me and confuses me. It's incredible what they've done with both engines/transmissions and engine management; but you can't seem to even open the hood of new cars without an engineering degree lol.
They days of carbs, distributors, big fans and 100 belts is truly over, huh?

Seriously, though -- THIS AFM isn't too complex. I suspect the original system that debuted in the Caddillac was mechanically activated. This one is computer controlled. The mechanical parts consist primarily of de-ac lifters (collapsable lifters), and an piece that sits in the valley (called the LOMA, or Lifter Oil Manifold Assembly) that controls oil-flow to the lifters. If it does go bad (which is very rare in this version), as somebody already mentioned - it keeps itself in V8 mode until you can get it checked out.
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Old 09-29-2008, 09:52 PM   #17
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They days of carbs, distributors, big fans and 100 belts is truly over, huh?

Seriously, though -- THIS AFM isn't too complex. I suspect the original system that debuted in the Caddillac was mechanically activated. This one is computer controlled. The mechanical parts consist primarily of de-ac lifters (collapsable lifters), and an piece that sits in the valley (called the LOMA, or Lifter Oil Manifold Assembly) that controls oil-flow to the lifters. If it does go bad (which is very rare in this version), as somebody already mentioned - it keeps itself in V8 mode until you can get it checked out.
I was gonna say, fuel injectors are way easier to play with than carbs, basically all fuel injectors are is jets that spray directly onto the back of the valves. With carbs you're always in danger of one slip that sends all the little springs clips and other parts everywhere.
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