Why do so many LS3/L99 engines blow smoke? - ModernCamaro.com - 5th Generation Camaro Enthusiasts
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post #1 of 4 Old 07-04-2014, 08:47 PM Thread Starter
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Why do so many LS3/L99 engines blow smoke?

Hi all I am new to GM products and now own a 2014 Camaro 1LE myself. My question is after seeing numerous videos of LS3's and L99's on dynos that many seem to blow blue smoke when revving down? ( Not huge amounts, but enough to make me think that something may be wrong). Is this a valve seat issue or something else? As I said this seems to be somewhat common from what I have seen but if i knew my car was doing that I would be looking for mechanical issues.
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post #2 of 4 Old 07-05-2014, 06:21 AM
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You're the very first person in the five years this car had been in production that I've seen make this claim.

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post #3 of 4 Old 07-05-2014, 07:15 AM
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If you have the video, then please post it so we can see. I've never heard or seen this from the dyno videos I've watched. But now I'm curious that I may have missed something.

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post #4 of 4 Old 07-05-2014, 08:33 AM
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there is a little spurt of blueish smoke on almost all cars in dyno videos if you would notice its when the car is correcting and metering the gas flow and blowing carbon out of the exhaust also, most cars on a dyno have just had their fuel flow altered through custom mapping of their fuel flow if they were lucky enough to have a custom tune via a good tuners programming and thus if they are cammed have to have the fuel flow altered to be even richer so as to never produce a lean condition which could seriously mess up a engine. So if you notice videos or even cars getting on it going down the road most the time cars are getting there use in the low rev range doing city driving, and when they do get on it they do blow some carbon out the exhaust and the car goes hey...... here comes the gas suddenly because your going WOT......... and that means a little smoke until it adjusts to the right stoic mixture as programmed into the cars ECU......... I have not noticed them doing it when reving down particularly unless what your seeing is lag to get the gas properly metered into the engine to go down to the right level....remember the heated sensors in the exhaust also preheat to get going right and the hot exhaust can set off gas that's not burned to combust also.
MY car with its dual mode exhaust also has an occasional exhaust fart...yes mild backfires from the sudden change in going from a muffler to straight pipes and the change in the back pressure making it ignite the extra gas when it suddenly dumps more gas into a hot exhaust, and no I am not talking about the deceleration baffling.............. As a dual mode works at idle, then about 3500 rpm it starts again to go through the straight pipe when getting on it in the rpms. If I ever want to stop it from a occasional backfire I just need to install a mild to wild switch and keep it on wild..... I most likely will someday. And of the videos I have seen the cars are not making smoke when revving down its when they are getting on it above their normal operating range of low in the rpm band.

Here is a video of mine on the dyno, notice it makes smoke when under load not when revving down and the smoke is white and the car was off and cold so the car is going to make some smoke when not up to temp and I do have high flow cats with the sensors.... My car is under Marks car on the facebook page ........



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