Why 2 V8s just 22hp apart?

Doesnt make any sense to me.

Two thoughts (no direct knowledge):

1) Slightly more fuel efficiency with the 400 HP motor so that when combined with the auto, it doesn't get hit with the gas guzzler tax.

2) Slightly lower powerband (ie...better low-mid range power/torque) with the 400 HP motor, improving the "feel" of the car with the automatic.

Both of those goals could be accomplished with the same basic motor, but with a slightly longer intake runner package and different cam profile on the 400 HP motor - though I have no idea what they actually did.

They wanted a V8 with active fuel management (AFM), but for some reason AFM will only work with an auto.

Therefore the manual will come with the LS3, and the auto will come with the L99 - basically an LS3 with AFM.

Also, for what ever reason the L99 has slightly less power than the LS3.

That makes perfect sense (come to think of it, seems I read that somewhere), and youl almost certainly know a lot more about it than I do.

Bob

could it just be a rating and the actually hp numbers are close? GM has underated motors before when in reality they are the same power

If GM had the ability to fudge numbers like they used to they would have most likely put them at the same rating. However because of SAE certified ratings, they came up with those different hp numbers for the LS3 and L99.

Automatics generally have more drivetrain loss too. I wonder if that had anything to do with the ratings.

i think the engines are rated on engine dynos so its measuring actual crank losses and trans effects are not seen there

right, they are rated at the engine, not at the wheels.

I betcha it has something to do with AFM limiting the RPM.

Regular fuel vs premium would make a difference also. Reminds me of my 96 LT4 Collector Edition Vette where you could only get the 6 speed with the 330hp LT4. So the L99 with AFM is only available with the auto and the LS3 is only available with the stick.

Two thoughts (no direct knowledge):

1) Slightly more fuel efficiency with the 400 HP motor so that when combined with the auto, it doesn't get hit with the gas guzzler tax.

2) Slightly lower powerband (ie...better low-mid range power/torque) with the 400 HP motor, improving the "feel" of the car with the automatic.

Both of those goals could be accomplished with the same basic motor, but with a slightly longer intake runner package and different cam profile on the 400 HP motor - though I have no idea what they actually did.

ya i dont think the intake is going to be any different. The L76 in the G8 has AFM and its pretty much the same engine other than being a 6.0 vs a 6.2 and it too has the same intake as the LS3. A major difference besides having SLIGHTLY lower compression giving it the ability to use lower octane fuel, though, is that the L76 has vs. the LS3 is GM cut corners and put solid (heavy) valves in the L76, which reduced it's ability to rev (which the afm probably hindered anyways). The L99 im thinkin has the solid valves as well, which could be a factor in changing out the cam and longevity of the springs.

What I have been told, not by a GM engineer though, is that with AFM the special lifters limit both revs and valve lift. If that is true then they probably had to limit engine speed and cam profile and found out that they could save a few dollars per motor with solid valves in the L99 and not loose any performance.

Or since this is all speculation anyway, maybe they use the hollow valves anyway but just limit the cam lift and or ramps and the engine speed. Who knows. But it is probably not the case that it is simply engine speed that accounts for the 20 HP since they are rated at the same RPM anyway.

Heck during the 3rd gen days Chevy had 2 different power outputs for the auto and the manual with the 5.0 motor.

It is all about making sure that the Camaro does not have a Gas Guzzler tax which would kill sales. I am sure if the GG tax was not a factor they would only offer the LS3. My guess is with a computer tune you can get the same performance with the auto and L99 as with the manual LS3

It is all about making sure that the Camaro does not have a Gas Guzzler tax which would kill sales. I am sure if the GG tax was not a factor they would only offer the LS3. My guess is with a computer tune you can get the same performance with the auto and L99 as with the manual LS3

maybe. but im sure mod vs. mod the LS3 > L99.

maybe. but im sure mod vs. mod the LS3 > L99.

That's what I'm thinking as well. With all of the special AFM parts, it would probably be more costly to upgrade the internals of a L99 as well. (cam, RR, etc.) That will be a long debate I'll have with myself about which motor to get. I'm pretty much set on the L99, but will have to see what the aftermarket provides. My current camaro is already faster than either, so which is fastest probably won't be a concern.

That's what I'm thinking as well. With all of the special AFM parts, it would probably be more costly to upgrade the internals of a L99 as well. (cam, RR, etc.) That will be a long debate I'll have with myself about which motor to get. I'm pretty much set on the L99, but will have to see what the aftermarket provides. My current camaro is already faster than either, so which is fastest probably won't be a concern.

Perhaps the aftermarket can make extra HP and torque by tweaking the L99's VVT?

Perhaps the aftermarket can make extra HP and torque by tweaking the L99's VVT?

the L99 doesn't have VVT.

EDIT: it does have VVT.

the L99 doesn't have VVT.

And single cam VVT is pretty worthless anyway.

if you are going to upgrade the cam and valvetrain on the l99 engine you will need to eliminate the AFM/DOD by replacing the l99 lifters with LS1,2,3 lifters

the L99 lifters and valvetrain are very limited, that is why the L99 only has a 6000 rpm rev limiter and the LS3 camaro will have a 6600 rpm rev limiter from the factory

if you are going to upgrade the cam and valvetrain on the l99 engine you will need to eliminate the AFM/DOD by replacing the l99 lifters with LS1,2,3 lifters

the L99 lifters and valvetrain are very limited, that is why the L99 only has a 6000 rpm rev limiter and the LS3 camaro will have a 6600 rpm rev limiter from the factory

It may be like the L76 and be limited to 6000 rpm because of the AFM/DOD hardware AND because it has the solid valves vs. the hollow sodium filled valves found on the LS3.

if you are going to upgrade the cam and valvetrain on the l99 engine you will need to eliminate the AFM/DOD by replacing the l99 lifters with LS1,2,3 lifters

the L99 lifters and valvetrain are very limited, that is why the L99 only has a 6000 rpm rev limiter and the LS3 camaro will have a 6600 rpm rev limiter from the factory

I'm wondering who is going to be the first to pull the AFM stuff and step WAY up with a solid roller setup backed by a 4500-5000 stall converter.

I'm wondering who is going to be the first to pull the AFM stuff and step WAY up with a solid roller setup backed by a 4500-5000 stall converter.


im building a 415 stroker LS3 to take the place of my L99 camaro engine

VVT in 3v ford is mostly for helping pumping losses cruising(cams are retarded) and emissions. no EGR. wide lobe seperation.

programmer only get 7hp by fooling with it on a 345rwhp n/a 4.6 in my car club.

RWTD did the tuning. he added 7 lb-ft throughout the rpm band. i guess it's free power, but not really much.

I'm wondering who is going to be the first to pull the AFM stuff and step WAY up with a solid roller setup backed by a 4500-5000 stall converter.

check out the G8 guys with the L76. basically the same engine except its a 6.0 vs. the 6.2 on the L99, other than that, it shoud be a just about identical engine.

I haven't decided yet if I will go LS3 or L99 in my '93 but I want the 6 speed auto tranny for sure.

Others have suggested bits and pieces of the reasons -- I'll put it all together and confirm:

1. GM doesn't like to put AFM with manual transmissions. There's a shock that goes through the drivetrain when an AFM-enabled V8 switches from 4-cylinder to 8-cylinder mode. With a manual trans, they feel that too much of the NVH from that shock enters the passenger compartment. So, no AFM with a manual.

2. The AFM-enabled version of the LS3 is the L99. The valve opening events on the standard LS3 cam are too agressive for the special lifters used with AFM, so the L99 necessarily has a less agressive cam (and therefore less horsepower). The only other differences I'm aware of are the AFM-specific hardware and related programming changes.

I haven't decided yet if I will go LS3 or L99 in my '93 but I want the 6 speed auto tranny for sure.

if your going to put it in your 93, it would be no question in my mind to go with the LS3. The L99 will probably only get 1 - 2 mpg better than the LS3, with both being auto. The LS3 would have less hassles.

Others have suggested bits and pieces of the reasons -- I'll put it all together and confirm:

1. GM doesn't like to put AFM with manual transmissions. There's a shock that goes through the drivetrain when an AFM-enabled V8 switches from 4-cylinder to 8-cylinder mode. With a manual trans, they feel that too much of the NVH from that shock enters the passenger compartment. So, no AFM with a manual.

2. The AFM-enabled version of the LS3 is the L99. The valve opening events on the standard LS3 cam are too agressive for the special lifters used with AFM, so the L99 necessarily has a less agressive cam (and therefore less horsepower). The only other differences I'm aware of are the AFM-specific hardware and related programming changes.

1. I don't know of any manufacturer that offers AFM (or whatever they call it) with a stick.

I agree with you on the NVH, especially since (I’ve read that) the deactivation happens on the compression stroke (so it can reactivate on a compression stroke and improve throttle response) and that the ECM will occasionally reactivate each cylinder for a single (2 revolution) cycle to keep that cylinder’s charge ready for sudden acceleration.

2. I’ve read that in the L76 the issue was that the AFM lifters could not collapse far enough to soak up all of the LS2 cam’s lift so the cam profile had to get a haircut for the L76. I suspect that the LS3/L99 had the same issue.

I don't know of any manufacturer that offers AFM (or whatever they call it) with a stick.

Yeah, I don't either. I didn't mean to imply that GM was the only manufacturer that felt this way... but GM is the only manufacturer whose opinion on the matter counts when we're talking about Camaro's engine options. :)

right, they are rated at the engine, not at the wheels.

I thought HP measurements have been SAE since the early 70's which meant the dyno readings were taken at the rear wheels.

The SAE has put in new regulations that require that all engine manufacturers do their ratings while under the same conditions. So there's no chance of someone testing under conditions suitable to make more power. They must also report the exact hp/tq they get. So no rounding or under/over rating.

BTW, just to make sure you're clear. SAE stands for Society of Automotive Engineers. Its not just a name for a rating or requirement.

The SAE has put in new regulations that require that all engine manufacturers do their ratings while under the same conditions.

So what are the conditions that SAE requires? I always figured it's been the same all this time, at the drive wheels. That's one reason I was always amazed at the HP ratings of today's cars.

If the new engines are rated at a higher HP than the gross HP ratings of the 60's AND they are supposedly net (SAE as I called it) HP, then they must be extremely powerful compared to the old engines.

See here for definitions of gross, net, and SAE certified (about 3/4 down):
http://en.wikipedia.org/wiki/Horsepower#SAE_horsepower

All are measured at the crank. Not sure what the conditions are exactly for SAE certification.

GM has a long history of using milder, more fuel efficient versions of the same basic engine when teamed with automatic transmissions in the F-body. The thinking is basically, the people who buy automatics aren't the "hard core" crowd. If they can trim a few HP that the non-hard-core buyers won't miss and pick up some fuel economy, that helps them with CAFE standards. They sell a LOT more automatic trans cars than they do manual trans cars, so it makes a difference when you're selling tens of thousands of them.

I can buy the technical explanation that cylinder deactivation technology isn't a good match for a manual trans. Makes perfect sense to me. But you know that whiz-bang valvetrain technology can't be cheap. And there is only one reason it exists in the first place- fuel economy. If that wasn't on the table and that technology didn't even exist, I can imagine an alternative scenario where you'd be seeing the automatic trans cars getting the 6.0L engine and the manual trans cars getting the 6.2L. Fuel economy is a big consideration for GM on a car like this that they intend to sell a lot of.

So what are the conditions that SAE requires? I always figured it's been the same all this time, at the drive wheels. That's one reason I was always amazed at the HP ratings of today's cars.

If the new engines are rated at a higher HP than the gross HP ratings of the 60's AND they are supposedly net (SAE as I called it) HP, then they must be extremely powerful compared to the old engines.

HP has never been rated at the wheels. The only time you get that is when they're put on a dyno by individuals.

Net ratings started in 1971 and were universal in 1972. Differences in ratings varied widely. A big contributor was intake and exhaust. A big 455 with a single exhaust could lose 100hp or more from gross to net, but with a dual exhaust and non-restrictive intake, maybe only 50hp.

Then some engines were underrated and others were overrated.

Still, the top engines from 1970 would probably be around 375hp under today's system. But there were very few of those sold. A 440/4 barrel in 1970, which was the highest performance Mopar engine sold in high volume, produced around 310 net hp.

Doesn't make Sense yet.

Doesn't make Sense yet.

You mean you don't understand why 2 v8s?

Simple. They don't want a guzzler tax on the Camaro. With the 6 speed, you can activate the 1-4 skip shift to avoid that. On the auto, you can use AFM.

No one has gotten AFM to work smoothly with a manual, so you won't see that one offered there. They won't offer the non-AFM on the auto, because who'd want to pay a $2000 gas guzzler tax for 22 more hp? But maybe Chevy will offer that in the future as a special edition.

maybe. but im sure mod vs. mod the LS3 > L99.

Not sure if this is going to be the case , I guess time will tell . I think mod vs. mod , the L99 will make more power because it has VVT , so as you mod it , you can control the VVT with tuning and we should be able to make more power ultimately with this platform as you start modding becasue of this . I have done all the testing with the G8GT in development for AFM camshafts and what needs to be done to make them work still utilizing the AFM , even though the G8GT does not have VVT , I have seen how beneficial this can be , the L99 is going to be very similar and I can't wait to get into it .

Mike

Not sure if they still do this, but in the late 70's(last hp rating I looked up that had it explained) they had dyno'd the engine and the rating was at the tail shaft of the transmission with all accessories installed. This was on a 79' Formula with the 403 Olds that was rated at like 175 hp or something rediculous.

They're all rated at the flywheel- even in 1973. They switched from SAE Gross to SAE Net ratings, but both were always at the flywheel. Gross was with open exhaust & intake, no accessories and (often) optimized tuning. Net was a lot closer to "as installed" with air cleaner, full exhaust, spinning all accessories, factory tuning, etc. But they were always rated at the flywheel. Doesn't mean they didn't cheat in other ways (picking specific RPMs for the published numbers, rather than listing the peak numbers, for example).

In recent years they tightened the specs even further (plus some other changes to how HP was measured and under what conditions) because certain "foreign" competitors were using setups for testing that were fairly far from "as installed," but still within the old rules. Quite a few "foreign" engines lost 10-15HP from their ratings while the Z06 Corvette actually benefited from them, getting a small bump from 500HP to 505HP.

Not sure if they still do this, but in the late 70's(last hp rating I looked up that had it explained) they had dyno'd the engine and the rating was at the tail shaft of the transmission with all accessories installed. This was on a 79' Formula with the 403 Olds that was rated at like 175 hp or something rediculous.

185! Zoom!

If you lived in a low altitude state that wasn't California, you could get a Pontiac 400 with 220hp.

Emission controls strangled those engines, in spite of what the sticky topic in this forum might say.

I'll probably get the 400hp motor w/ auto tranny just for gas reasons. We never know when the gas prices will go up again, so having that AFM will be nice to have while at the same time having a 400hp motor to stomp on.

so are they callin the auto a l99 or ls3 n do u think insurance will be diff if u have a l99 compared 2 the ls3

so are they callin the auto a l99 or ls3 n do u think insurance will be diff if u have a l99 compared 2 the ls3

si, d auto s l99 n stk s ls3

I just ran into this today while reading around.... it explains much of what I wanted to know about the AFM and VVT.
http://www.gmhightechperformance.com/tech/0902gmhtp_2010_chevy_camaro_engine_options/index.html