GM 3.6 experts... Why the disparity between different LFX engines? (Page 1/7)
Raydar AUG 30, 05:31 PM
The High Feature DI 3.6 (LFX) is/was available in several different platforms.
The lowest HP (~280) came in the Impala.
The highest HP (~320) came in the Camaro.
Various platforms had different HP ratings between those two extremes.

Other than the obvious differences (intake manifold to accommodate longitudinal or transverse configuration, and exhaust plumbing) are there any other real hardware differences (cams, etc.) ? Are any of the transverse intake manifolds better than the others?

I expect the tune would be different, but will it really make that much of a difference, with a free flowing intake manifold and exhaust?

Thanks!

------------------
Raydar
88 Formula IMSA Fastback. 4.9, NVG T550

Praise the Lowered!

cvxjet AUG 30, 05:51 PM
Stupid computer decided it could outsmart me....Luckily, I don't got no smarts!

[This message has been edited by cvxjet (edited 08-30-2016).]

cvxjet AUG 30, 05:52 PM
I don't have any facts, but the usual reason for that large a HP difference would be different cams- The family car gets a "torque heavy" cam while the Camaro gets a cam that concentrates more power up high, including a high peak for bragging rights.....Different exhaust and even more restrictive intakes usually don't make that big a difference...usually only 5-15 hp. There also may be differences due to later model improvements.

Just curious- How much do these engines weigh?
Raydar AUG 30, 06:07 PM
Found this online.

code:

Horsepower hp (kw) @ rpm
Chevrolet Camaro Coupe and Convertible:	        323 hp (241kW) @ 6800 SAE Certified
Chevrolet Caprice Police Patrol Vehicle (PPV):	301 hp (225kW) @ 6700 SAE Certified
Chevrolet Impala Police Vehicle:	        302 hp (225kW) @ 6800 SAE Certified
Chevrolet Impala:	                        300 hp (224kW) @ 6500 SAE Certified
Chevrolet Equinox:	                        301 hp (225kW) @ 6500 SAE Certified
Cadillac CTS Coupe, Sedan and Wagon:	        318 hp (237kW) @ 6800 SAE Certified
Cadillac SRX:	                                308 hp (230kW) @ 6800 SAE Certified
Cadillac XTS:	                                304 hp (226kW) @ 6800 SAE Certified
Cadillac ATS:	                                321 hp (239kW) @ 6800 SAE Certified
Buick LaCrosse:	                                303 hp (226kW) @ 6800 SAE Certified
GMC Terrain:	                                301 hp (225kW) @ 6500 SAE Certified
Torque lb.-ft. (Nm) @ rpm
Chevrolet Camaro Coupe and Convertible:	        278 lb.-ft. (377Nm) @ 4800 SAE Certified
Chevrolet Caprice Police Patrol Vehicle (PPV):	265 lb.-ft. (359Nm) @ 4800 SAE Certified
Chevrolet Impala Police Vehicle:	        262 lb.-ft. (355Nm) @ 5300 SAE Certified
Chevrolet Impala:	                        262 lb.-ft. (355Nm) @ 5300 SAE Certified
Chevrolet Equinox:	                        272 lb.-ft. (369Nm) @ 4800 SAE Certified
Cadillac CTS Coupe, Sedan and Wagon:	        275 lb.-ft. (373Nm) @ 4900 SAE Certified
Cadillac SRX:	                                265 lb.-ft. (359Nm) @ 2400 SAE Certified
Cadillac XTS:	                                264 lb.-ft. (358Nm) @ 5200 SAE Certified
Cadillac ATS:	                                275 lb.-ft. (373Nm) @ 4800 SAE Certified
Buick Lacrosse:	                                264 lb.-ft. (358Nm) @ 5300 SAE Certified
GMC Terrain:	                                272 lb.-ft. (369Nm) @ 4800 SAE Certified



The horsepower disparity seems to be less than what I believed, in my initial post. Different sources...
Perhaps it has to do with the transmissions that are utilized, too.
Longitudinal pieces seem to be able to withstand a bit more "ummmph". Maybe because they don't have the chains and sprockets.
Again, this is just speculation.

I suppose that I should mention that what really appeals to me about this engine (other than 320 HP, "out of the box") is that the exhaust manifolds are integral to the heads. There is one big oval shaped port on each head, where the downpipe bolts up. No headers are required (or even possible, for that matter.)

[This message has been edited by Raydar (edited 08-30-2016).]

cmechmann AUG 30, 06:36 PM
Weight, about 20 lbs lighter than a 3800. According to wiki.

That aside. We are seeing a few issues with the 3.6. Timing chain components. Oil leaks.
Due to some of the issues, GM has toned down the HP curves in some of the flash updates.
Some of the HP differences, have to do with the valve timing maps.
Raydar AUG 30, 07:05 PM
Interesting. I've been hearing about the timing chain stuff.
Not really an issue to me. I'm prepared to replace all of that, while the engine is out of the car.

Any other info is appreciated.
(Also been hearing about "carboned up" intake valves on the DI engines. (Everyone's. Not just GM.) The universally recommended fix seems to be a good oil catch can.
Joseph Upson AUG 30, 08:06 PM

quote
Originally posted by Raydar:

Found this online.

code:

Horsepower hp (kw) @ rpm
Chevrolet Camaro Coupe and Convertible:	        323 hp (241kW) @ 6800 SAE Certified
Chevrolet Caprice Police Patrol Vehicle (PPV):	301 hp (225kW) @ 6700 SAE Certified
Chevrolet Impala Police Vehicle:	        302 hp (225kW) @ 6800 SAE Certified
Chevrolet Impala:	                        300 hp (224kW) @ 6500 SAE Certified
Chevrolet Equinox:	                        301 hp (225kW) @ 6500 SAE Certified
Cadillac CTS Coupe, Sedan and Wagon:	        318 hp (237kW) @ 6800 SAE Certified
Cadillac SRX:	                                308 hp (230kW) @ 6800 SAE Certified
Cadillac XTS:	                                304 hp (226kW) @ 6800 SAE Certified
Cadillac ATS:	                                321 hp (239kW) @ 6800 SAE Certified
Buick LaCrosse:	                                303 hp (226kW) @ 6800 SAE Certified
GMC Terrain:	                                301 hp (225kW) @ 6500 SAE Certified
Torque lb.-ft. (Nm) @ rpm
Chevrolet Camaro Coupe and Convertible:	        278 lb.-ft. (377Nm) @ 4800 SAE Certified
Chevrolet Caprice Police Patrol Vehicle (PPV):	265 lb.-ft. (359Nm) @ 4800 SAE Certified
Chevrolet Impala Police Vehicle:	        262 lb.-ft. (355Nm) @ 5300 SAE Certified
Chevrolet Impala:	                        262 lb.-ft. (355Nm) @ 5300 SAE Certified
Chevrolet Equinox:	                        272 lb.-ft. (369Nm) @ 4800 SAE Certified
Cadillac CTS Coupe, Sedan and Wagon:	        275 lb.-ft. (373Nm) @ 4900 SAE Certified
Cadillac SRX:	                                265 lb.-ft. (359Nm) @ 2400 SAE Certified
Cadillac XTS:	                                264 lb.-ft. (358Nm) @ 5200 SAE Certified
Cadillac ATS:	                                275 lb.-ft. (373Nm) @ 4800 SAE Certified
Buick Lacrosse:	                                264 lb.-ft. (358Nm) @ 5300 SAE Certified
GMC Terrain:	                                272 lb.-ft. (369Nm) @ 4800 SAE Certified



The horsepower disparity seems to be less than what I believed, in my initial post. Different sources...
Perhaps it has to do with the transmissions that are utilized, too.
Longitudinal pieces seem to be able to withstand a bit more "ummmph". Maybe because they don't have the chains and sprockets.
Again, this is just speculation.

I suppose that I should mention that what really appeals to me about this engine (other than 320 HP, "out of the box") is that the exhaust manifolds are integral to the heads. There is one big oval shaped port on each head, where the downpipe bolts up. No headers are required (or even possible, for that matter.)



Interesting inquiry, I've been researching these specs since last week in consideration for buying an 08 or later Cadi CTS. I'm not sure what years the specs you posted cover but much of that diversity in performance output possibly addresses integral vs. traditional exhaust manifold arrangement and port vs. DI injection which apparently is still an option, along with the other differences you mentioned although I'm not sure about cam changes playing a big part from what I encountered in the past on that subject as they are usually the same throughout a particular engine nomenclature and often across. The Cadillac CTS received the first highest output 3.6L with DI and some fancy cylinder head work along with a compression ratio bump and some other stuff I don't recall and apparently the Camaro eventually received the same engine.

There is a crate 3.6L upgrade for the 2016 ATS that produces more power than any of the engines you've posted, here;

http://www.karlperformancep...Karl-Chevrolet/46462

As for the timing chain problem, I read a couple of days ago that a good bit of that problem appears to be the result of prolonged oil change intervals which an owner states a good faith recall was offered for, that would adjust the oil life monitor programming to require shorter oil change intervals. Another owner stated the real problem was not the chain but VVT module wear in conjunction with sensitive DTC programming that caused engine lights to come on and stay on, an issue that was also stated to have been addressed in the good faith recall with an adjustment to the programming to increase the required thresh-hold to trip the light, which more frequent oil changes were also alleged would help by reducing wear.

[This message has been edited by Joseph Upson (edited 08-30-2016).]

dobey AUG 30, 08:13 PM

quote
Originally posted by cmechmann:
Weight, about 20 lbs lighter than a 3800. According to wiki.

That aside. We are seeing a few issues with the 3.6. Timing chain components. Oil leaks.
Due to some of the issues, GM has toned down the HP curves in some of the flash updates.
Some of the HP differences, have to do with the valve timing maps.



Which 3.6 are you talking about exactly? The earlier 3.6 timing chain issues were corrected in later revisions (ie, the LFX which is specifically the one asked about in this thread).
dobey AUG 30, 08:19 PM

quote
Originally posted by Raydar:
The horsepower disparity seems to be less than what I believed, in my initial post. Different sources...
Perhaps it has to do with the transmissions that are utilized, too.
Longitudinal pieces seem to be able to withstand a bit more "ummmph". Maybe because they don't have the chains and sprockets.
Again, this is just speculation.



The HP ratings are crank HP, not wheel HP, so what trans comes with is mostly irrelevant. The main difference in the HP ratings is pretty much all in the ECM tune, intake, and exhaust. The transverse cars all have a Y pipe and single cat. The longitudinal cars all have dual cats prior to any Y-pipe or X-pipe. As the intake and exhaust are slightly different in the different configurations, there are some tuning differences to deal with those. Part of the difference is also marketing. There will be higher numbers on certain car classes simply as a result of marketing, but when you consider driveline losses and vehicle weight, most of the cars all come out around the same, despite the differences.
dobey AUG 30, 08:36 PM

quote
Originally posted by Joseph Upson:
There is a crate 3.6L upgrade for the 2016 ATS that produces more power than any of the engines you've posted, here;

http://www.karlperformancep...Karl-Chevrolet/46462

As for the timing chain problem, I read a couple of days ago that a good bit of that problem appears to be the result of prolonged oil change intervals which an owner states a good faith recall was offered for, that would adjust the oil life monitor programming to require shorter oil change intervals. Another owner stated the real problem was not the chain but VVT module wear in conjunction with sensitive DTC programming that caused engine lights to come on and stay on, an issue that was also stated to have been addressed in the good faith recall with an adjustment to the programming to increase the required thresh-hold to trip the light, which more frequent oil changes were also alleged would help by reducing wear.



The LGX is the Gen IV HF 3.6 engine. It's in the 2016 ATS, CTS, and Camaro (among a few others. The crossover SUVs with the engine have it at 310 HP, while the cars all have it at 335 HP. It replaces the LFX across GM's offerings.

As for the timing chain issues, my understanding is that there was a mechanical design defect in the timing system of the 3.6L, which was fixed in the LFX and subsequent Gen IV HF engine design. However, to mitigate the issue on earlier engines where the problem was more common, the ECM changes were made, for shorter oil changes and such.