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I'm guessing it's cams and accompanying tuning, but what's the difference between the two 3.6L's that account for the different outputs?

I want to hear it's just tuning, but it can't be that easy to get 20 more hp.

Or can it?
 

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As far as I know, the engine and internals are the same throughout the LFX line up. What makes the difference is the fact that the impala engines are mounted transversely(front wheel drive mostly) which means that GM has to use different upper intake manifolds and especially a different exhaust route. You'll find out soon that the 2012 and up impalas have a "horseshoe" bend in the exhaust i believe to keep the pipes of equal length but nevertheless restricts exhaust flow and restricts power output. Tune might be mainly for throttle feel but the engine and internals should be the same throughout. Hope this helps.
 

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For what its worth, every time I chop a little more of my exhaust off, I feel a power bump. I don't know if its just me driving different, but after I got the full overkill kit + 91 octane tune. I dropped and additional half a second to sixty when I went to my side exit exhaust. That included a cat delete, resonator delete and replacement with a 12in dynomax race bullet. I cut the exhaust in the middle of the bend right before the rear wheel and dropped a 90 degree bend plus tip there. I definitely think the impalas have a massive restriction in their exhaust, possibly for NVH reasons.
 

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I'm guessing it's cams and accompanying tuning, but what's the difference between the two 3.6L's that account for the different outputs?

I want to hear it's just tuning, but it can't be that easy to get 20 more hp.

Or can it?
Henry, the main difference are the FWD vs RWD, the exhaust system and the upper manifold intake.


Not much you can do with the engine/transmission position, but, you can definitely increase your intake manifold volume by adding the 3/4" spacer from Jacfab and bolting on a 80mm TB with is included aluminum spacer.


Now, no disrespect for Kniptastic, but I would encourage you to install (if not done yet) a complete Magnaflow exhaust and if you really serious about performance, a set of downpipes cats (200 CPSI metallic) from hotexhaust.com.


Please return to my dyno sharing info's regarding all the mods. The Impala (especially the 8th gen) is mods are done right, it's a pure sleeper car.


Cams are the same lifts and duration


But, the horseshoe is definitely a problem that I'm looking to get fix this winter (and maybe use my own set to make other sets and sell them to exclusive Impala owners).


But (if not done yet) you definitely need a tune, the stock tune just has a crazy amount of KR and other performance restrictions.
 

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The absolute worst LS V8 intake was the one on the FWD applications, best ultimately on the later trucks with their practically unlimited space.
Cramming an engine and tranny under the hood causes compromises.

Is the octane recommendation the same? Octane does NOT make HP but can be used with a more aggressive tune to make more power.
 

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The absolute worst LS V8 intake was the one on the FWD applications, best ultimately on the later trucks with their practically unlimited space.
Cramming an engine and tranny under the hood causes compromises.

Is the octane recommendation the same? Octane does NOT make HP but can be used with a more aggressive tune to make more power.
Dwayne,


don't want to start a huge discussion with the octane, but, the LFX 3.6L are equip with a Delphi MT88 ECMS that self adjust to 87 to 98 and E30 to E85.


I do agree that, if you data-log with 91, you will get better performance vs. a non data log tune.


Also, please do not forget, the 3.6 engine is equip with a direct injection fuel system, the engine runs better on 91 vs. 87
 

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I hadn't considered the flex fuel aspect but even at that if the Camaro base tune is based on 91 octane(asking I don't know) and the Impala 87 then the timing tables would still be different since the flex fuel sensor measures alcohol content not octane. GM has been known to underrate one application vs another, and to just be more aggressive with tuning too.
GM has had a history of using the same engine as the Vette in other vehicles and just shaving a few HP off the rating so the Vette or other performance vehicle is rated higher. The LT1 and LS1 Vettes were the same exact engine other than the extra main bolts in the LT1, similar weights and 10-15hp different rating in the literature but a lot closer in real life. The LS3 in my SS is the same as the Vette but rated at 415hp where the highest it was rated in the Vette was 436 and the Vette dual mode exhaust was not worth 21 HP

I really am not up on the V6 and/or direct injected stuff, the Impala is my wife's car, I am a dinosaur and my interest lay in pushrod V8 RWD so I am speaking in generalities of what I have seen over my 20 years of automotive enthusiasm, no real specific knowledge about the 2014 Impala sitting in my driveway.

Actually I had another thought that goes to how ratings are derived that many people might not understand. A different accessory package on the engine could change the ratings since the ratings are as installed in the car.
 

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The ONLY reason that you get better performance with higher octane fuels is because the higher the octane content, the more resistant it is to to knock, which will degrade performance. Like Dwayne said, octane itself does NOT produce more power.

The way that these tunes work is that they start off with a "high octane" tming value - and will continue to use the "high octane" timing table UNLESS it detects knock. If the ECM detects knock, it will gradually reduce the timing *towards* the value in the "low octane" table until the knock stops.

So the ECM doesn't actually "detect" the octane level of the gas at all - it simply lowers the timing if it detects knock (which is increased with lower octane fuels).

So higher octane = more power simply because the engine will knock less - which means that the ECM won't reduce timing.

Really, it's not as complicated as you may think - it's all pretty straight forward really. Just as a 'for example' - with the 2012 Impala stock tune, the tune uses a timing value of 25 degrees at 2000rpm/.40g aimass (the "high octane" value). However, if the ECM detects knock at that RPM/airmass combination, it will slowly reduce the timing, down towards 13 degrees (the "low octane" value) - unless the knock stops before then. As you can see, that is a pretty big difference in timing (27 vs 13) - which means the octane rating of the fuel you use can have a significant impact on the amount of power you get. This is why these engines run s much better on higher octane fuel - because they'll knock less and stay closer to the "high octane" timing values.

The ECM doesn't use any actual octane values for any of it's calculations (it has no idea what the octane level is) - it simply starts with the "high octane" timing value and only reduces timing towards the "low octane" value if it detects knock. The ECM also uses a "knock learn" system, where it wil "preemptively" pull timing in certain RPM/airmass areas where in previously detected knock - at least until it determines that the specific RPM/airmass "cell" has been knock-free for a certain amount of time (it slowly reduces the "knock learn" value in the absence of knock). So even if you aren't currently getting any knock, the timing can still be reduced if there was knock in that "cell" earlier.

These 3.6L LFX engines actually have a knock sensor for each cylinder too (instead of one per bank) - and the stock tune is setup so that they are VERY sensitive - so you'd be surprised how my KR you actually get during normal, everyday driving - *especially* with lower octane fuels. If you want to squeeze every last bit of power out of these engines, it's very important to use a high-octane fuel. I've done tons of data logging and it's so easy to see how this all works, simply by logging (and graphing) the knock-retard, knock learn and various timing-related PIDs.

Sent from my HP SlateBook 10 x2 PC using Tapatalk
 

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Thing is maximum performance isn't necessarily had with maximum timing. Timing advance is a compromise, in a perfect world the spark would be at TDC not before, when it is before pressure from the flame is building while the piston is still compressing which is wasted energy. It is necessary waste though because the flame takes time to travel. If we light at TDC the burn isn't complete at the end of the power stroke and exhaust is still burning as it leaves the cylinder.
 

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Thing is maximum performance isn't necessarily had with maximum timing.
Understood. But the goal is to have the "high octane" table set to "optimal" timing values in order to get the most power for each RPM/airmass combination. Assuming that the high octane table is set correctly, any knock will reduce the timing from those "optimal" values - and the increased octane will help avoid the knock.

It's not like the high octane table is set to 40 degrees of timing across the board. It's set to what the manufacturer deems the optimal timing for each RPM/airmass combination.

Generally speaking, higher timing=more power (again, until you go past the "optimal" timing). So my point was just that higher octane resists knock - and you want to avoid knock as much as possible. These higher compression engines really seem to benefit from higher octane more than lower compression engines (don't know the technical reasons why, but that is my understanding).

I was really surprised how much KR my 2012 Impala has - even with 93 octane gas. And the KR is only going to get worse with lower octanes.

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Understood. But the goal is to have the "high octane" table set to "optimal" timing values in order to get the most power for each RPM/airmass combination. Assuming that the high octane table is set correctly, any knock will reduce the timing from those "optimal" values - and the increased octane will help avoid the knock.

It's not like the high octane table is set to 40 degrees of timing across the board. It's set to what the manufacturer deems the optimal timing for each RPM/airmass combination.

Generally speaking, higher timing=more power (again, until you go past the "optimal" timing). So my point was just that higher octane resists knock - and you want to avoid knock as much as possible. These higher compression engines really seem to benefit from higher octane more than lower compression engines (don't know the technical reasons why, but that is my understanding).

I was really surprised how much KR my 2012 Impala has - even with 93 octane gas. And the KR is only going to get worse with lower octanes.

Sent from my HP SlateBook 10 x2 PC using Tapatalk
Quick question for you, i have a 2015 V6 Impala and I was wanting to tune it (dyno or anything), would a V6 Camaro tuner be able to tune my car? Or is the computer set up different?
 
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