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Replying to Understanding the 2012 Buick LaCrosse with eAssist System

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Posted 18 April 2014 - 05:36 PM

1st, try a different dealer.
2nd, does the auto-stop work when the hvac system is powered off and the engine is at operating temp?

Posted 18 April 2014 - 07:57 AM

OK,  Every one sounds like they might be able to help me, or at least explain my problem,


I have 2012 Buick Lacrosse, 4cly eAssist, 6speed, 16,000 miles, I bought it used, 11,390 miles, everything seemed ok, Every once in awhile the check engine light came on, dealer asked if it was solid on, or blinking, it was on solid, brought car to dealer, found history in EVDR(event data recorder)  It was cleared after checking with program scanner, Reprogramed various control modules, lets get back to the problem,



The "AutoStop" feature does not function at all, since the reprogramming was done, back to the Dealer. they can't find the problem/ it didn't repeat it self,     (AHHHHH, it wasn't working) did anyone test drive the vehicle?   Nope, I give up, called GM, there are sorry for my problems, BRING IT TO THE DEALER, well, if the dealer can't find the problem, who do I bring it to?? 


Here is my night mare......NO WARRANTY on vehicle, what so ever...when I bought the car, the title was "Rebuilt" yes, I knew and accepted that, for a better price, But, I DID HAVE A DEALER,   GM, check it, and they gave it a  OK, said it appears only to be body damage, Should I kick my self in the butt, or can some one guide me as what to do?? or what could be the problem.



ONE extra Note...since the reprogamming, the Idle seems higher, the gauge on dash used to be around 500 rpms to 550, in drive, now 750 to 800??


Posted 12 December 2010 - 12:58 PM

More than likely, putting the transmission into sport mode will override the engine shut off.

Posted 12 December 2010 - 12:52 PM

i was stuck in a 28 mile long traffic jam and it took over 6 hours to get out of it. how many times can this system restart the car when you only move less than a car length each move? can it be shut off ?

Posted 07 December 2010 - 07:03 AM

thanks again.
i was thinking it didn't look right... the L and T.

Posted 07 December 2010 - 03:53 AM

thanks dwight, but the tranny isn't rated for even 180hp, unless it actually is a different design, just the same "6L40". is that 180 with the 15hp motor added? ...could the engine be 1/2 atkinson 1/2 otto, so it'd loose ~10% power?
this is what's confusing me.

(1) There is no such thing as a 6L40 to begin with and there is no way the Lacrosse will use a "6L" transmission. There is the 6L45, 6L50, 6L80 and 6L90 -- there is no 6L40 in existence. All the 6L transmissions are for Longitudinal, Rear Drive, applications. Hence, the "L".

(2) The 4-pot Lacrosse uses the 6T40 transmission -- 6 speed, Transverse, torque rating 40. This transmission is rated for 180hp / 177 lb-ft and is used in the Lacrosse, Equinox and Terrain. The V6 Lacrosse uses the 6T70 tranny with their 3.0 and 3.6 V6 engines.

(3) If you are interested, the ratings for all the aforementioned GM Hydramatic Transmissions are as follows:-

  • 6L45 -- 6-speed, Longitudinal, Up to 278 hp / 258 lb-ft / 7000 rpm
  • 6L50 -- 6-speed, Longitudinal, Up to 315 hp / 332 lb-ft / 7000 rpm
  • 6L80 -- 6-speed, Longitudinal, Up to 469 hp / 439 lb-ft / 6500 rpm
  • 6L90 -- 6-speed, Longitudinal, Up to 555 hp / 550 lb-ft / 6200 rpm
  • 6T40 -- 6-speed, Transverse, Up to 180 hp / 177 lb-ft / 7000 rpm
  • 6T70 -- 6-speed, Transverse, Up to 315 hp / 280 lb-ft / 7000 rpm
  • 6T75 -- 6-speed, Transverse, Up to 315 hp / 300 lb-ft / 7000 rpm

Note: The 6L45, 6L50 and 6L80 are also sold to BMW for use in the 3-series and 5-series. BMW buys GM trannies because their traditional supplier (ZF) did not have a suitable transmission to support the "xi" AWD models. The 6T70 model is jointly developed with Ford and is also used in the Ford Fusion, Lincoln MKZ and other Ford vehicles.

(4) The ratings have pretty conservative built-in margins. Generally, you can exceed them by a bit with absolutely no ill effects. In fact, GM routinely does that. The Equinox and Terrain for instance puts 182hp through the 6T40 even though it is rated at 180hp. The CTS-V exceeds the 6L90's ratings by 1 hp and 1 lb-ft.

(5) Yes, an engine can be a "mild" Atkinson and lose only 10% of its original power rating. It all depends on how late you close the intake valves. A typical Atkinson engine closes them about 25~30% into the intake stroke, losing a similar percentage of power. You can close it a mere 10% into it and lose 10%. But, you'll also not reap as much efficiency benefits. I don't think this is the case here though... 182 hp --> 180 hp is so trivia that it is probably from small variations in the exhaust, air box or things of that nature.

Posted 06 December 2010 - 08:51 PM

thanks dwight, but the tranny isn't rated for even 180hp, unless it actually is a different design, just the same "6L40". is that 180 with the 15hp motor added? ...could the engine be 1/2 atkinson 1/2 otto, so it'd loose ~10% power?
this is what's confusing me.

Posted 06 December 2010 - 08:11 PM

My point is that this is a full size car with, now, a ten cubic foot trunk.

deal breaker. taurus trunk. 21 c.f.

Posted 06 December 2010 - 05:28 AM

so...they're not using the "normal" 2.4L now with DI so they'd have to use the 6L45? (to handle the more power) is this weird?
i was just skimming.. is the 2.4 just going to be Atkinson cycle?

(1) At 180hp (as opposed to 182) I am pretty sure it is NOT Atkinson. An Atkinson cycle engine loses between 20~30% of the compression stroke to regurgitation through the intake valves -- they have cams that are ground to keep the intake valves open for the first 20~30% in of the compression stroke. This causes a similar 20~30% decrease in power output compared to the same engine were it to be operating with a regular Otto cycle*. If the 2.4L were to be Atkinson cycle, one will expect the output to drop from 182hp to about 127~146hp.

(2) There is a way to get the best of both worlds. You can switch between Atkinson Cycle and Otto Cycle Cam lobes if you implement a cam switching system (ala VTEC). The engine can operate on Otto mode during hard acceleration and revert to Atkinson mode during idle, cruise and light throttle situations. It's not a free lunch of course. Using same pistons and heads, there is a dramatic difference between the compression ratio of the engine in Otto and Atkinson modes. For instance, if the engine is normally 11.2:1 (Eg. GM's "LAF" DI 2.4L), an ideal Atkinson cam will drop the effective compression to 7.8:1 -- that's pretty darn low. If you want to keep the effective compression at around the Prius' 9.5:1, the compression ratio under Otto mode will have to be a staggering 13~13.5:1. Even with premium fuel, that is a bit too high. Hence, some kind of compromise has to be struck. Either the Atkinson mode is not as deep as a dedicated Atkinson engine would use, or the Otto mode compression is higher than typical calling for premium fuel usage, or a combination of both. An engine that does Otto-Atkinson switching is the Honda Civic's SOHC R18A 1.8 Liter -- it makes 140hp and uses a rather "mild" Atkinson grind during low load situations.

(3) I do not believe the GM 2.4 is using a cam switching system. The current heads are not designed to accommodate it and if they switch the head architecture to a completely new one, I am sure they'll trumpet it.

* Eg. The Toyota Prius' 1.8 liter engine (2ZR-FXE) has a geometric compression ratio of 13.0:1. It keeps the intake valves open for the first ~27% of the compression stroke. This ejects about a similar percentage of the intake air before the valves close and compression begins, resulting in an effective compression of about 9.5:1 in Atkinson mode. The Prius's engine (2ZR-FXE) makes 98hp compared to 138hp the non-Atkinson version in the Corolla (2ZR-FE). A 29% output loss to (similar) 27% compression stroke reduction.

Posted 05 December 2010 - 11:15 PM

My point is that this is a full size car with, now, a ten cubic foot trunk.

Yes, i saw that, but my question involves the fact that a car that wasn't a hybrid from the beginning doesn't really have a place to hide the battery without intruding somewhere

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