L99 vs LS3 Question

[Marotrent]

Hey guys quick question I’m getting ready to purchase my headers and CAI so I was YouTubing some videos of cars that have already done these mods. From what I found it looks like with headers, CAI, and a tune L99’s are make around 360-370hp and LS3’s are making 410-420🤨. I have a L99, so my question is are these #’s accurate? I should have my TSP long tubes and CAI what kind of improvement should I be getting?

[Rob Russell]

The numbers are pretty accurate. But don’t let the number deceive you. I have a L99 with long tubes, exhaust, cai, and tune. I raced my buddy with the same set up and he had a LS3 and my car ran nearly .1 of a second faster in the quarter mile not once, but twice. While the LS3 makes more power, the L99 still has its advantages with VVT and being auto.


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[pyroguy]

There's a few reasons why the L99 makes less horsepower to the wheels than the LS3. First of all, we start with 26 less bhp. This is due to the way the L99's are built. The L99 has a different cam that is more AFM/DOD friendly which produces less horsepower. Secondly, L99's are mated to an automatic transmission. Powertrain loss from a manual car is about 13% in these cars while the automatic is somewhere around 20% +/- a couple %. So a car making 365 rwhp in an automatic is making about 455 bhp. My L99 car has a rotofab intake, ported throttle body, long tube headers with cats, and a catback exhaust for performance mods and made 365rwhp and 390rwtq. My car performs comparably with my friend's LS3 car has almost identical mods and made 427rwhp and 430 rwtq. Yes it is nice to be able to say I have XXX horsepower and have it be high, but at the end of the day the only numbers that count are lap times and ET's.

[Royal Tiger]

Pyro did a good job explaining.

L99 has its issues as does the LS3, but I wish we had just gotten an auto LS3 like in the Corvette. I’ll be doing a cam at some point and getting rid of all the weaknesses in the L99.

[Marotrent]

Originally Posted by Rob Russell

The numbers are pretty accurate. But don’t let the number deceive you. I have a L99 with long tubes, exhaust, cai, and tune. I raced my buddy with the same set up and he had a LS3 and my car ran nearly .1 of a second faster in the quarter mile not once, but twice. While the LS3 makes more power, the L99 still has its advantages with VVT and being auto.


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Ok cool thanks, I was starting to think I purchased the wrong car lol. Last question what’s vvt?

[Marotrent]

Originally Posted by pyroguy

There's a few reasons why the L99 makes less horsepower to the wheels than the LS3. First of all, we start with 26 less bhp. This is due to the way the L99's are built. The L99 has a different cam that is more AFM/DOD friendly which produces less horsepower. Secondly, L99's are mated to an automatic transmission. Powertrain loss from a manual car is about 13% in these cars while the automatic is somewhere around 20% +/- a couple %. So a car making 365 rwhp in an automatic is making about 455 bhp. My L99 car has a rotofab intake, ported throttle body, long tube headers with cats, and a catback exhaust for performance mods and made 365rwhp and 390rwtq. My car performs comparably with my friend's LS3 car has almost identical mods and made 427rwhp and 430 rwtq. Yes it is nice to be able to say I have XXX horsepower and have it be high, but at the end of the day the only numbers that count are lap times and ET's.

Thanks you summed that up well

[Rob Russell]

Originally Posted by Marotrent

Ok cool thanks, I was starting to think I purchased the wrong car lol. Last question what’s vvt?

VVT= Variable Valve Timing. Has to do with fuel economy and emission stuff. I was going to get a LS3, but did some research to only find that L99’s were beating the LS3’s so I went the auto route.


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[shaggy2002]

Pretty sure it is the autos are faster than manuals more than the L99 is faster than the LS3. If both motors had autos, the LS3 would be faster. my 2 cents.

[sdynak]

This is not mine.. borrowed from the Corvette forum as also wanted to point out the compression differences.

The L99 and LS3 engines are both built on the same platform, featuring 6.2L of displacement and eight cylinders. The camshaft of the L99 engine has slightly less duration than the one found in the LS3, giving the Camaro SS paired with this motor a smoother ride. The compression ratio of the L99 motor is 10.4:1, as the pistons have valve reliefs machined in the top halves of the pieces. The LS3’s compression ratio is 10.7:1.

Some Additional Differences w/ LS3 Engine
•L99 camshaft is different — having a little less duration and a little less lift, both of which give the engine a smoother idle.
•L99 has a cam phaser and, to get the additional piston-to-valve clearance required when cam phasing changes, the pistons are different parts having valve reliefs machined into their tops. The reliefs lower the compression ratio to 10.4:1.
•L99 PCV system is different having its oil separators in the valve covers rather than down in the valley like the LS3.

https://www.corvetteforum.com/forums...fferences.html