I saw two RPO codes for that engine on Wikipedia, LZ8 and LZ9. Both of them have VVT and DOD, according to that. What are the differences then?

3.9L has DoD??? since when... isnt that later?

3.9L has DoD??? since when... isnt that later?

[post="47699"]<{POST_SNAPBACK}>[/post]

Well yeah, should have made myself clearer. One said there is (LZ8) and the other one said coming (LZ9). So in a sense both of them at the end will be the same engines, so I got confused.

The 3900 in the Impala and G6 has DOD, but it's turned off because they couldn't get rid of a strange noise when it switched from 3 to 6 cylinders. It should be ready by next year at the latest.

So that means there's a hack to enable it? :D

The 3900 in the Impala and G6 has DOD, but it's turned off because they couldn't get rid of a strange noise when it switched from 3 to 6 cylinders. It should be ready by next year at the latest.

[post="47747"]<{POST_SNAPBACK}>[/post]

WOW! Did not know that!-----COOL! :)

The 3900 in the Impala and G6 has DOD, but it's turned off because they couldn't get rid of a strange noise when it switched from 3 to 6 cylinders. It should be ready by next year at the latest.

[post="47747"]<{POST_SNAPBACK}>[/post]

Damn, too bad that couldn't have been fixed before it debuted in those cars--the DoD would have helped boost the PATHETIC fuel economy figures from the 3900. Everytime I look at the numbers, I keep hearing to myself, "God, just get the V8."

Question about the 3900 V6--is it a descendant of the old 2.8L V6 that came out in the X-cars circa 1979? If so, how in the world did they punch it out to such a large displacement? :blink:

Question about the 3900 V6--is it a descendant of the old 2.8L V6 that came out in the X-cars circa 1979?  If so, how in the world did they punch it out to such a large displacement?  :blink:

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Uhm cause the 2.8L was designed with the intentions of being able to become a larger displaced engine in the future!

Question about the 3900 V6--is it a descendant of the old 2.8L V6 that came out in the X-cars circa 1979?  If so, how in the world did they punch it out to such a large displacement?  :blink:

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Increasing the diameter of the cylinders (punching it out) is not the only, nor the easiest way to increase displacement. The easier way and the way to add a great deal of displacement is to increase the stroke length by changing the crankshaft and connecting rods.

Right. I'm guessing that at some point, the castings had to be changed though because the bore AND stroke have both been increased signficantly since the 2.8L days (assuming the 3.9L is based on the old 2.8L, of course). The 2.8L started out as a very compact engine in the first place and I've seen what they looked like inside. I just can't imagine there was a lot of meat in the block for larger bores and/or lots of room for a larger crank to twirl around within... I guess I'm curious if there's someone who knows where I could find a good history of these engines...I'm not that familiar with them.

Right. I'm guessing that at some point, the castings had to be changed though because the bore AND stroke have both been increased signficantly since the 2.8L days (assuming the 3.9L is based on the old 2.8L, of course).  The 2.8L started out as a very compact engine in the first place and I've seen what they looked like inside.  I just can't imagine there was a lot of meat in the block for larger bores and/or lots of room for a larger crank to twirl around within...

I guess I'm curious if there's someone who knows where I could find a good history of these engines...I'm not that familiar with them.

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It has the same bore spacing and deck height. It is a VERY compact engine. Go pop in at the local Chevy or Pontiac dealer and take a look it is quite cool.

i heard the ole 2.8L was fine until 6500rpms even though redline was far lower than that. WHat is the new 3.9L goodtill?

The 2.8 and 3.9 are unrelated. Here is an old press release with some information.
3.9 V6

Compared to the prior 60deg OHC V6s (3100, 3400, 3500 and the smaller v6s built in China), the new 3500 and 3900 have a slightly offset bore center \V/ to enable a wider bore and longer stroke. It's not an uncommon solution, but I can't remember off the top of my head which other engines use it outside GM.

Compared to the prior 60deg OHC V6s (3100, 3400, 3500 and the smaller v6s built in China), the new 3500 and 3900 have a slightly offset bore center \V/ to enable a wider bore and longer stroke. It's not an uncommon solution, but I can't remember off the top of my head which other engines use it outside GM.

[post="54170"]<{POST_SNAPBACK}>[/post]

VW's VR series motors?

Compared to the prior 60deg OHC V6s (3100, 3400, 3500 and the smaller v6s built in China), the new 3500 and 3900 have a slightly offset bore center \V/ to enable a wider bore and longer stroke. It's not an uncommon solution, but I can't remember off the top of my head which other engines use it outside GM.

[post="54170"]<{POST_SNAPBACK}>[/post]

VW's VR series and W series.

Ahhh, so THAT'S how they did it. Very interesting. Until now, I didn't realize that the 2006 version of the 3.5L is altogether different from the 2005 and earlier versions... Thanks for all the info!

Ahhh, so THAT'S how they did it.  Very interesting. Until now, I didn't realize that the 2006 version of the 3.5L is altogether different from the 2005 and earlier versions...

Thanks for all the info!

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This is confusing to a lot of people including myself. The 3.5 LX9 in the Malibu, G6, and Minivans is not the same 3.5 that is in the Impala. The LX9 is related to the previous motors (2.8, 3.1, 3.4) but the Impala's 3.5 LZE and 3.9 LZ9 are different designs.

Damn, too bad that couldn't have been fixed before it debuted in those cars--the DoD would have helped boost the PATHETIC fuel economy figures from the 3900.  Everytime I look at the numbers, I keep hearing to myself, "God, just get the V8."

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It's interesting to note that the recently release Monte Carlo 3LT or LTZ models with the 3900 are rated at 20/28 while the same Impala models are rated at 19/27. They both use the same engine and 3.29:1 gears. Does anybody know why this is? 20/28 isn't really bad and is in fact only 1 mpg off the highway rating of the previous 3800 full size car ratings.

Strange, but could be one (or more) of many factors. Some of which being weight and aerodynamics (though I'm sure they're close to each other in both respects).

The 2.8 and 3.9 are unrelated.  Here is an old press release with some information.
3.9 V6

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That's not the 2.8L we're talking about. There's a 2.8L in the early Corsicas and Cavaliers. That one belongs to the 60 degree V6 family.

the 2.8L that I got. complete with a twin barrel carburator and 110hp to boot!

Now I'm confused again (doesn't take much). Wasn't the 2.8L in the X-cars (Citation et. al.) also a 60-degree design? My brother still has an '83 S10 Blazer with the carb'd 2.8L V6. It sure looks like a 60-degree engine.

Now I'm confused again (doesn't take much). Wasn't the 2.8L in the X-cars (Citation et. al.) also a 60-degree design?  My brother still has an '83 S10 Blazer with the carb'd 2.8L V6. It sure looks like a 60-degree engine.

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Yes the 3.9 and 2.8 V6s as well as the 3.1 and 3.4 V6s were all 60°s. The newest 3.5, the VVT one, and the 3.9 VVT use a different block with offset bore centers to achieve the best displacement per volume ratio.

Yes the 3.9 and 2.8 V6s as well as the 3.1 and 3.4 V6s were all 60°s.  The newest 3.5, the VVT one, and the 3.9 VVT use a different block with offset bore centers to achieve the best displacement per volume ratio.

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Cool! As always, I appreciate your informative replies.

Edited to correct grievous spelling error.

Edited January 11, 200619 yr by NeonLX