Jump to content
Sign in to follow this  
dwightlooi

LFX 3.6 Liter DI-VVT V6 -- Official Details

  

13 members have voted

  1. 1. LFX

    • Cheers!
      12
    • Boo!
      1


Recommended Posts

I'd like to see what they could do w/ a V8 version of this engine, maybe around 5.0L..

There is no V8 version in existence or under development. However, if there is, it will displace 4752 cc (4.8 liter), sport a compact 60 degree Vee angle and probably require a balance shaft to be refined. It'll also probably make about 420~430 hp and 365~375 lb-ft on regular 87, perhaps 20 more on 91 octane.

I know, I was speculating...GM is not ambitious enough to build a modern DOHC V8. And why would be 4752cc? How can you speculate such a precise number?

Edited by Cubical-aka-Moltar

Share this post


Link to post
Share on other sites

I'd like to see what they could do w/ a V8 version of this engine, maybe around 5.0L..

There is no V8 version in existence or under development. However, if there is, it will displace 4752 cc (4.8 liter), sport a compact 60 degree Vee angle and probably require a balance shaft to be refined. It'll also probably make about 420~430 hp and 365~375 lb-ft on regular 87, perhaps 20 more on 91 octane.

I know, I was speculating...GM is not ambitious enough to build a modern DOHC V8. And why would be 4752cc? How can you speculate such a precise number?

adding 2 cylinders to the 3.6L V6 ;) easy peasy.

Share this post


Link to post
Share on other sites

While the LFX 3.6L DI-VVT V6 sounds fantastic, a V8 derivative should be simple to do. A better question is why GM should actually do that given their very good existing Vortec V8 line. In other words, does Cadillac need a spiritual successor to the Northstar V8, or is it merely to keep up with MB, BMW, Lexus et. al.?

Share this post


Link to post
Share on other sites

I know, I was speculating...GM is not ambitious enough to build a modern DOHC V8. And why would be 4752cc? How can you speculate such a precise number?

The very premise of an LFX derived V8 is that it uses the same exact valves, springs, lifters, bolts, rods, pistons, sprockets, chains, accessory drive, combustion chamber geometry, intake design and the whole nine yards. The difference being a new block casting for two more cylinders, a new crankshaft and accommodations somewhere for a balance shaft. Retaining the the 94 x 85.6 mm (bore x stroke) of the 3.6 V6 and adding two cylinders yield ((94/2)^2)*3.1416*85.6*8 = 4752 cc

  • Upvote 1

Share this post


Link to post
Share on other sites

While the LFX 3.6L DI-VVT V6 sounds fantastic, a V8 derivative should be simple to do. A better question is why GM should actually do that given their very good existing Vortec V8 line. In other words, does Cadillac need a spiritual successor to the Northstar V8, or is it merely to keep up with MB, BMW, Lexus et. al.?

Well, we know what GM is currently doing. They are do a direct injected, variable timing equipped and cylinder deactivation capable version of the LS3. From a performance, packaging, weight or fuel economy standpoint such an engine gives no ground to a DOHC V8. A 60 deg DOHC V8 however will at least be similarly narrow as a pushrod 90 deg V8 and fit in the same approximate space. This engine will be economical to engineer and produce because it shares the majority of its component, design and assembly tooling as the high volume V6. It will also match the LS3's 420~432 hp with 23% less displacement, albeit with a torque deficit of 60~70 lb-ft. This does not necessarily translate into better fuel economy because of the higher parasitic frictional losses of a DOHC design and it does incur an MPG penalty. On the flipside, because the pistons are smaller and strokes are shorter the vibrational forces are also milder while rpm limits are higher. The reduced rotational inertial also makes for a faster revving engine.

Is this a better engine for Cadillac in lieu of a advanced pushrod? That is debatable. It will however be more like what the Europeans, Japanese and Koreans are offering both in terms of displacement as well as specific output. Again, whether it is better to be like everybody else, is debatable. It will also have a tax advantage in Global Warming coolaid drinking countries with a displacement tax, however this is probably not a significant consideration for a V8, unlike more economy oriented V6 and I4 offerings.

  • Upvote 2

Share this post


Link to post
Share on other sites

So is the LS3 engine being used right now? If so, which cars? If not, how soon will it be on the road in a GM car?

Share this post


Link to post
Share on other sites

So is the LS3 engine being used right now? If so, which cars? If not, how soon will it be on the road in a GM car?

The LS3 is the engine currently in the Corvette and Camaro SS. It is a 16v Pushrod V8 without variable timing or direct injection. It displaces 6.2 liters and makes 436hp @ 5900 rpm / 428 lb-ft @ 4600 rpm in the Corvette (426hp @ 5900 rpm / 420 lb-ft in the Camaro). It is physically smaller and lighter (183 kg) than the BMW 4.0 V8 in the M3 (202 kg). Fuel economy is exemplary for its power class, delivering 16 / 26 MPG in the Corvette and 16 / 24 MPG in the rather heavy Camaro SS (3860 lbs).

The LS3 is not the highest revving or most powerful of the current small blocks -- those honors will have to fall on the 7.0 liter LS7 (505hp) or and Supercharged LS9 (638hp). Rather, it represents the middle of the road, mainstream, version of the current generation of small block V8s.

The LS family is considered the Gen IV Small Block V8. GM is currently working on its successor family -- collectively known as the Gen V Small Block V8. The Gen V engines are expected to retain the 2-valve per cylinder layout, but add direct gasoline injection, variable valve timing and cylinder deactivation as standard features. The Gen V engines, by virtue of direct injection and resultant increase in compression ratio alone is expected to make between 6~10% more power (~470 hp). Fuel economy is also expected to be slightly better, probably on the order of 1 mpg.

  • Upvote 2

Share this post


Link to post
Share on other sites

OK, thanks. When does the Gen V small block come out?

The engine will probably launch on the C7 Corvette around 2013. Versions of it will probably replace the V8s in the Cadillac Vs, the Camaro SS, as well as GM's Light Trucks and full-size SUVs.

  • Upvote 1

Share this post


Link to post
Share on other sites
Guest Rob-O

Hi All,

Does anyone know where I can get a detailed diagram of the GM 3.6 LFX measurements?

Thanks!

Share this post


Link to post
Share on other sites

Hi All,

Does anyone know where I can get a detailed diagram of the GM 3.6 LFX measurements?

Thanks!

I don't think GM publishes a "drafting grade" drawing of the LFX. But you can get the majority of the official statistics here.

http://www.gmpowertrain.com/VehicleEngines/PowertrainProducts.aspx

Share this post


Link to post
Share on other sites
Guest tom

question: doesen't the integrated 3-to-1 exhaust collector on the LFX rob HP? Now I can't put on headers.

Share this post


Link to post
Share on other sites

question: doesen't the integrated 3-to-1 exhaust collector on the LFX rob HP? Now I can't put on headers. 

 

question: doesen't the integrated 3-to-1 exhaust collector on the LFX rob HP? Now I can't put on headers. 

 

Yes, it does but not as much as you think. A properly designed, integrated collector will flow as well as ANY header placed on individual ports. No matter how fat or fancy the header, it is not going to flow any more exhaust than the size of the ports themselves dictate -- whish is why many engien builders feel a need to open up the ports by hand or through machining. The biggest thing isn't power, but the ability to tune the torque band. An integrated 3-to-1 collector is in effect the shortest possible 3-to-1 header. That is good for high RPM breathing actually but not so good for low RPM torque. Exhaust pulses travel at roughly the speed of sound. Exhaust pulses will travel from the valve to the collector where it opens up to the other two passages as well as the downpipe. This is when it is at the lowest pressure. At a particular RPM, this will happen the same amount of time it takes for the engine to open that valve again and this conincidence of a low pressure event in the exhaust and the opening of the valve(s) help with scavenging at that particular RPM. With short headers, this resonant scavenging happen at a high RPM, with long headers it happens at a lower RPM.

 

An integrated collector does not allow you to design, or put in as an aftermarket accessory, long headers for trucks and shorter ones for sports cars for instance.

Edited by dwightlooi

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Sign in to follow this  



About us

CheersandGears.com - Founded 2001

We ♥ Cars

Get in touch

Follow us

Recent tweets

facebook

×
×
  • Create New...