Based on what you think aftermarket support will be (or currently is), do you think it'll be better to get a GT L76 to 500hp or a GXP LS3 to 600hp? By "better" I mean a combination of low costs, maintaining or improving gas mileage, maintaining the super-majority of the car's life span and reliability, and leaving as much of the drivetrain stock as is reasonable.

I'm thinking the L76 just because it would only have to be pushed 139hp or 39% instead of 198hp or 50% in the GXP's case... but will the aftermarket give it near as much support or will it only have a few overpriced vendors?

L76 and a Maggie and you're done. Keep AFM, the L76 has a lower compression ratio so hopefully more boost is possible add cut outs and be done.

IMHO of course!

L76 and a Maggie and you're done.

I agree.

Stock L76 - 361HP at flywheel = 301.5Rwhp on average with 15-18% drivetrain loss due to 6-spd automatic, although the baseline numbers leaking out have been higher, this is just in principle.

500HP L76 at flywheel = 417.5Rwhp on average with 15-18% drivetrain loss due to 6-spd automatic.

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Stock LS3 - 402HP at flywheel = 353.76Rwhp on average with 12% drivetrain loss due to 6-spd manual transmission.

600HP LS3 at flywheel = 528Rwhp on average with 12% drivetrain loss due to 6-spd manual transmission.

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The L76 needs an additional 116Rwhp to reach your goal
The LS3 needs an additional 174Rwhp to reach your goal

116Rwhp in either engine is easily attainable but an additional 174Rwhp is going to be a feat for either engine considering you want to maintain stock like drive-ability, fuel economy, reliabilty, and cost effectiveness, etc. To obtain an additional 174Rwhp sacrifices will be made most likely in the fuel economy, costs, and everday driveability categories. I know a forged bottom end stroker, with a supercharger, or turbos will obtain an additional 174Rwhp but that is not what this discussion is about. Hope this helps you out.

I say L76. Not sure how the DOD system will respond to mods, but I'm thinking the L76 with APS Turbos and you will be set. I think it would also depend on what else is upgraded on the GXP from the GT (i.e. suspension, brakes, etc.).

Simple answer, whatever version is sold most will get the benefit of the largest aftermarket umbrella. Simple economics 101 of supply and demand.

L76 and a Maggie and you're done. Keep AFM

Unfortunately, I just found out today that the AFM will not be able to be retained as previously thought... :(

Simple answer, whatever version is sold most will get the benefit of the largest aftermarket umbrella. Simple economics 101 of supply and demand.
That's the target of what I'm trying to ask. Does anybody think the aftermarket is going to be all over the LS3 and only a few will mind the L76?

Although, I guess that supercharger is officially in the works so hopefully it's priced well.

i voted GXP, mainly coz big power is always better with a manual.

doesn't need to be taken to 600HP, 500 would be plenty

That's the target of what I'm trying to ask. Does anybody think the aftermarket is going to be all over the LS3 and only a few will mind the L76?

Although, I guess that supercharger is officially in the works so hopefully it's priced well.

It's hard to say, more G8 specific mods may befit the GT with the L76. However, the GXP shares the LS3 which will have benefit of two years head start on some stuff.

All in all, LSx motor architecture is LSx motor architecture (L76 is of LSx heritage), so heads, cam, internals, etc, should all be interchangable.

At this point I wouldn't worry so much about getting more hp out of either, because you know for a fact that changing all the hard work the engineers put in will screw the balance of the car up. So how about taking the money spent on parts and learning to drive the car...No offense intended. I understand we all want more power, but there are trade-offs and this is what you need to weigh.

What about gxp to 500hp vs. l76 to 500hp?

That's my goal with whatever car I go with.

Simple answer, whatever version is sold most will get the benefit of the largest aftermarket umbrella. Simple economics 101 of supply and demand.

I agree, but don't forget the ls3 is in the vette as well. So as far as internal parts (cams, heads etc.) You'll still have the vette community backing you. As far as headers, intercoolers ect. It all depends on how popular the gxp is...

At this point I wouldn't worry so much about getting more hp out of either, because you know for a fact that changing all the hard work the engineers put in will screw the balance of the car up. So how about taking the money spent on parts and learning to drive the car...No offense intended. I understand we all want more power, but there are trade-offs and this is what you need to weigh.

Plans man, plans! You must always be looking toward the future otherwise you'll never improve!:judge:

At this point I wouldn't worry so much about getting more hp out of either, because you know for a fact that changing all the hard work the engineers put in will screw the balance of the car up. So how about taking the money spent on parts and learning to drive the car...No offense intended. I understand we all want more power, but there are trade-offs and this is what you need to weigh.
Throw a supercharger in the front and a real spare tire in the back! :shiner:

Isn't it 50/50 with no gas and two people in the front seats? Maybe the S/C would help bring back ballance lost by driving your car with a full tank.

What about gxp to 500hp vs. l76 to 500hp?

Yeah, I was thinking I'd want 500hp in a GT but the GXP wouldn't be anywhere close to worth the extra cost unless I could pull 575-600hp from the LS3 via the aftermarket for the same price as pulling 500 from the L76 (distinction: "same price" as in cost of upgrades, not total vehicle cost).

I'm just saying. Lets say gxp goes for 38k; 6k over a fully loaded gt.

GT
32K Stock =360hp
add
6.5K blower/intercooler/tune ~500hp
Total ~ 38.5k

GXP
38k Stock = 402hp
add
~3k headers/tune/catback/cam ~500hp
Total 41k (with brakes to stop 500hp and a suspension to handle it)

Seems about even without dealing with the reliability issues that a blower/intercooler setup can provide.

Guys, ease up on that creamin' and dreamin' of a reliable GT with anything over the LS3's output. Why? You're forgetting the mechanical limits of the 6L80E auto backing it up. Please see the link.
http://www.pacificp.com/forum/viewtopic.php?t=5717&sid=3f2004ff16e6bd4e95167eff5dda52bd

Guys, ease up on that creamin' and dreamin' of a reliable GT with anything over the LS3's output. Why? You're forgetting the mechanical limits of the 6L80E auto backing it up. Please see the link.
http://www.pacificp.com/forum/viewtopic.php?t=5717&sid=3f2004ff16e6bd4e95167eff5dda52bd

Blowing up the 80 is a great reason to get a 90. :judge:

True, but guys need to know what they're getting into, don't you think?

True, but guys need to know what they're getting into, don't you think?

If you don't know how to do research and you start messin' with stuff....well, you learn one way or the other. :bomb:

Don't they have 500rwhp going through this trany in vettes?

2007 Hydra-Matic 6L80 Transmission ( MYC ) 52206

Maximum engine power: 469 bhp ( 349 kW )
Maximum engine torque: 439 lb-ft ( 595 Nm )


2007 Hydra-Matic 6L90 Transmission ( MYD ) 71706

Maximum engine power: 452 bhp ( 337 kW ), Diesel: 300bhp ( 223kW )
Maximum engine torque: 531 lb-ft ( 720 Nm ), Diesel: 520 lb-ft ( 705 Nm )

What am I missing. I don't understand "maximum engine power" and why the 6L90 has lest.

I'm just saying. Lets say gxp goes for 38k; 6k over a fully loaded gt.

GT
32K Stock =360hp
add
6.5K blower/intercooler/tune ~500hp
Total ~ 38.5k

GXP
38k Stock = 402hp
add
~3k headers/tune/catback/cam ~500hp
Total 41k (with brakes to stop 500hp and a suspension to handle it)

Seems about even without dealing with the reliability issues that a blower/intercooler setup can provide.

That's a pretty compelling argument. How about warranties, though? $200 will buy you a 3/36 with a blower according to JustLucky. Are the modifications that you listed for the GXP going to blow the factory warranty? I'd pay the difference for brakes, suspension, and to be N/A only IF the GXP would retain its 5/100 factory warranty. If not, well.. it would be tough. I don't want to be without some sort of warranty for at least the first few years. :dunno:

What am I missing. I don't understand "maximum engine power" and why the 6L90 has lest.
Perhaps its rated lower because they had too many overrated 6L80s blow up on the CTS-Vs. :confused:

Aren't CTS-V manual only?

Aren't CTS-V manual only?

Until 2009 MY rolls out yup :)

Aren't CTS-V manual only?
I guess you're right. I thought that the 469hp/439lb-ft was the exact specifications of some car (namely the CTS-V) but perhaps I was confusing the hp with an E55 AMG and the torque with something else.. :bomb:

CORRECTION: The 2006 STS-V has 469/439 and an 6L80.

That's a pretty compelling argument. How about warranties, though? $200 will buy you a 3/36 with a blower according to JustLucky. Are the modifications that you listed for the GXP going to blow the factory warranty? I'd pay the difference for brakes, suspension, and to be N/A only IF the GXP would retain its 5/100 factory warranty. If not, well.. it would be tough. I don't want to be without some sort of warranty for at least the first few years. :dunno:
but wait. Could you get the L76 to ~450hp for $35k with $3k for the intake/exhaust/cam/tune? Is there any way to get it to 500 with a few bucks more?

What does it take to void the Pontiac warranty?

In terms of the vehicle's life span/reliability, which are the safest upgrades?

Continued here: http://www.g8board.com/forums/showthread.php?p=20651

At this point I wouldn't worry so much about getting more hp out of either, because you know for a fact that changing all the hard work the engineers put in will screw the balance of the car up. So how about taking the money spent on parts and learning to drive the car...No offense intended. I understand we all want more power, but there are trade-offs and this is what you need to weigh.

I never screwed up the balance of any of mine! LOL! Hard work all the engineers put in. The Engineer's work on any car is a compromise of many requirements set forth by the manufacturer. Some of those are POWER (obviously), reliability, emissions, C.A.F.E. requirements, servicability, parts cost and availability, noise standards, etc, etc.

I (as well as a majority of performance enthusiasts) don't care about 90% of those "compromises" and are more focused on power and reliability. IN which case, emissions, fuel economy, servicability, and a few other of those compromises those engineers worked so hard on, get a back seat.

Guys, ease up on that creamin' and dreamin' of a reliable GT with anything over the LS3's output. Why? You're forgetting the mechanical limits of the 6L80E auto backing it up. Please see the link.
http://www.pacificp.com/forum/viewtopic.php?t=5717&sid=3f2004ff16e6bd4e95167eff5dda52bd

Anytime you modify something, you run the risk of breaking something else down the line. Fact of life man. Gotta plan for it.

I know when I did the motors on either of my cars, that the OEM clutch was toast, as was the 10 bolt (in my Camaro), and a few other things down the line, so I budgeted for that too!

What am I missing. I don't understand "maximum engine power" and why the 6L90 has lest.

It looks like the maximum power the tranny has been validated to withstand. Basically, maximum engine power is the max horsepower and the torque is self-explanatory. Both would be "input" into the tranny or basically what your engine is making at the flywheel. The 6L90 should have a new rating for 2009 since the CTS-V is using this tranny as the auto option with the LSA which makes bigger numbers than what the rating shows. It will be interesting to see if anything is changed or only the validation changes.

Chip

Aren't CTS-V manual only?

The old ones are. The new ones will have an auto available...

It looks like the maximum power the tranny has been validated to withstand. Basically, maximum engine power is the max horsepower and the torque is self-explanatory. Both would be "input" into the tranny or basically what your engine is making at the flywheel. The 6L90 should have a new rating for 2009 since the CTS-V is using this tranny as the auto option with the LSA which makes bigger numbers than what the rating shows. It will be interesting to see if anything is changed or only the validation changes.

Chip

That's what I was thinking. Only 469bhp for the 6L80 wories me. As a grandprix owner. We are always f'n up our trannies.

the LS-series of engines has a substantially large aftermarket backing already existence. Getting the GXP to 500hp is going to be quite easy: intake, headwork, exhaust and ECU of sorts would be all it needs, I would imagine.

Does the L76 indeed share bits with LS-series? If so, that is beneficial to GT buyers.

Also, the VXR8 does come with an automatic gearbox, so my first guess is that these transmissions are slightly more robust than any previous American offerings.

Neither will be low cost to get to that level of horsepower with reliability.

Does the L76 indeed share bits with LS-series? If so, that is beneficial to GT buyers.


The L76 is essentially the LS3 with a different cam, different valves, a different tune, and displacement on demand.

That's what I was thinking. Only 469bhp for the 6L80 wories me. As a grandprix owner. We are always f'n up our trannies.

Living with both gen GPs (97 and 06), I have always been sensitive to the trannys. However, I think the 6L80 is a pretty robust tranny. My point was the tranny has a higher design capacity, GM seems to only validate to the heaviest use. Even though everyone says the Tremec is stronger, you notice it is only validated for an additional 40 lb ft of torque. I fee pretty good that this is going into the SUVs that will be towing and still have a 100,000 mile warranty. In our cars, even with a nice power bump, they should survive fairly well. These are not going to be nearly as fragile as the 4T65.

Chip