: Does the LSA have variable valve timing?



pmsteinm
02-24-09, 12:26 AM
I've noticed that some places on Cadillac's site, and the order sheet for my V, list the engine as "6.2L V8 VVT". However, the long media brief on GM Powertrain's website makes no mention of this. Anyone know the real answer? The torque and HP curves on that site don't look like there's variable timing.

Caddyscat
02-24-09, 01:31 AM
I read the same things and decided to have a look

I have the exploded pics of the engine - and aside from the oil squirters it looks like a typical LSX block, no vvt solenoids.

Have a look here -

http://gm.wieck.com/forms/gm/*query?09lsaExploded&sort=&source=all

in fact, i looked at it closely and didn't even know it had roller lifters and roller rockers. I see a cam directly connected to the crank.
Hope this helps a bit.

irvvvine
02-24-09, 02:26 AM
neat picture.

tedcmiller
02-24-09, 01:35 PM
No, the LSA engine does not have VVT. In fact, the presence of rollers on the lifters and rockers is quite a step forward for the old L series V-8 technology. The L-series of GM V-8s rely primarily on large displacement and pressure (ala superchargers) to get horsepower. Other high tech engines (e.g., Northstar) achieve higher horse power via high tech improvements such as VVT, four valves per cylinder, overhead cams, separate exhaust and intake cams, direct injection, individual ignition coils to eliminate the distributor, etc. and, occasionally, pressure (e.g., the STS-V). The latest, employed by some foreign manufacturers, is variable valve lift (i.e., changing the amount that the valve opens) to totally eliminate control of air input to the cylinders via a butterfly valve (or valves). Then there is the Ducati valve system called Desmodromic where the valve springs are eliminated by using a cam to open and close the valves (no valve float at high RPM.)

pmsteinm
02-24-09, 01:47 PM
Thanks for the replies. I don't mind not having VVT, one less thing to break/wear out. I'd really rather not even have a supercharger (no replacement for displacement), but in today's political environment its probably the only way to get good power #'s. Given a choice between 400hp and N/A or 556hp and S/C, I'll take the supercharger (and the nicer interior, stronger diff, etc, etc)

tedcmiller
02-24-09, 01:55 PM
It should be noted that the only references I can find to VVT in connection with a 6.2 liter V-8 on the Cadillac website is for the Vortex V-8 in the Escalade and EXT.

pmsteinm
02-24-09, 02:07 PM
They probably had a typo in the system when I ordered in November. My print out from GlobalConnect has this under options:

LSA: Engine, 6.2L V8 VVT


Hopefully they put the right engine in it ;)

JEM
02-24-09, 07:11 PM
The L-series of GM V-8s rely primarily on large displacement and pressure (ala superchargers) to get horsepower. Other high tech engines (e.g., Northstar) achieve higher horse power via high tech improvements such as VVT, four valves per cylinder, overhead cams, separate exhaust and intake cams, direct injection, individual ignition coils to eliminate the distributor, etc. and, occasionally, pressure (e.g., the STS-V).

Actually, the LS-family motors get horsepower through a whole lot of work on computer-modeling of cylinder head airflow and minimizing internal friction and windage losses. And, of course, blowers. The fact that compact pushrod heads and tight packaging of the accessory drive allows greater engine piston displacement for a given external package size and weight helps too.

Electrohydraulic VVT is recent tech, and in the pushrod world is used on the Escalade motors (moving the entire cam) - the Viper's pushrod V10 uses CamInCam (the system could handle variable intake and exhaust timing, but the Viper installation only varies exhaust events):
http://www.youtube.com/watch?v=0uiDmcPEekc

Four valves per cylinder and overhead cams was high tech in 1914: http://www.ddavid.com/formula1/peug1914.htm


The latest, employed by some foreign manufacturers, is variable valve lift (i.e., changing the amount that the valve opens) to totally eliminate control of air input to the cylinders via a butterfly valve (or valves).

There's BMW's Valvetronic, which uses followers on an eccentric shaft to vary valve lift, and it can be (but isn't exclusively) used for throttling. There's other variable-lift systems that don't (or at least aren't used to) replace the throttle - Honda VTEC, later Porsche Variocam setups IIRC. Is the extra valvetrain complexity worth the benefit?



Then there is the Ducati valve system called Desmodromic where the valve springs are eliminated by using a cam to open and close the valves (no valve float at high RPM.)

Desmodromic valve operation also dates to the 19-teens, the '50s Merc 300SL/SLR used it too.

JFJr
02-24-09, 09:57 PM
So we should remember when encountered by European and Asian car snobs that look down upon the pushrod technology of the LS series engines, to remind them that 4-valve-per-cylinder engine technology dates back to the early 1900's, and mention that the LS series engines are extremely compact and powerful, weigh less and have fewer moving parts than 4-valve-per-cylinder engines. GM engineers are among the best in the world, and we "V" owners are the beneficiaries.

JEM
02-24-09, 11:22 PM
So we should remember when encountered by European and Asian car snobs that look down upon the pushrod technology of the LS series engines, to remind them that 4-valve-per-cylinder engine technology dates back to the early 1900's, and mention that the LS series engines are extremely compact and powerful, weigh less and have fewer moving parts than 4-valve-per-cylinder engines. GM engineers are among the best in the world, and we "V" owners are the beneficiaries.

There's a few key 'advanced technologies' - but they're almost all in either design and modeling, manufacturing, or engine controls and sensors. By and large these are applicable no matter what the valvetrain configuration. I doubt anyone's going to run out and try to wring modern-era capabilities out of, say, a flathead V12, but I'd imagine somewhere at GM someone has a direct-injection LS3 derivative somewhere.

GMX322V S/C
02-24-09, 11:44 PM
Perhaps early V2 concepts incorporated the Escalade/EXT motor, but then they had a change of heart and went with the LSA, but forgot nomenclature already in the pipeline.

tedcmiller
02-25-09, 12:38 AM
JEM implies that there is something incorrect about the information in my post about the power developed by the GM LS V-8 engines. Perhaps JEM would like to identify what specifically was in error.

wait4me
02-25-09, 01:15 PM
The typo was just because they are using the 6.2L displacement of the truck and the person typing up the options just didnt notice that it brought that up. Most of the people in charge of that stuff dont have a clue.