does anyone know what the rpm's are when the VVT kicks in on the 2.4? i cant tell from exhaust or anything im guessing 3500-4500?

 

Its constantly variable timing. It depends on engine speed and throttle position (engine load/air flow).

 

This isn't VTEC, you won't hear it. And for that fact, a properly tuned VTEC shouldn't be heard anyways, thats a ricer mod.

 

^^ beat me too it...!!


Yu must be confused with VEEEETEECCHHH..!! VVT is "on" all the time..

 

can anyone explain how its constantly on cause im pretty sure i understand vtec, and is vvt the same as mivec or is that totally seperate?

 

Here ya go...


http://en.wikipedia.org/wiki/Variable_valve_timing

"Varies valve timing continuously throughout the RPM range for both intake and exhaust for improved performance in both overhead valve and overhead cam engine applications"

 

i fell mine kick in right at 4 grand

 

The cams constantly change position from centerline in relation to each cylinder event (cam timing). At some speeds and throttle positions it may be only a degree or two from centerline, at others it may be more drastic.

The ECM has a matrix preloaded of commanded cam angles depending on engine speed and engine load.

There is no crossover point nor a separate set of cam lobes like vtec. VVT simply changes cam angle on the fly. Think of it as computer controlled adjustable cam gears.

 

sounds good to me

 

i dunno about all this cam timing n crap, because i swear the sec i hit 4 grand, its like a boost of power all of a sudden.

 

it might just be more "noticeable" in higher RPMS but it is always "there" per say...

 

well i read that link you posted and it stated that to reduce over flow of gas that vvt is set to kick in at higher rpms. if you let vvt stay in affect all the time, too much gas and air will be brought into the engine and wont be burned fasted enough, meaning its set at a higher rpm, like 4 thousand.

 

thats a valid point.. then like you maybe im confused as well, where are the smart tech guys when ya need them.... lol ill keep looking for info tho

 

yea thats why im going to college soon to become a machanic hahah

 

2.4L Ecotec

GM will also introduce variable valve timing to the Ecotec four-cylinder engine family. A 2.4L Ecotec will be an optional powerplant in the 2005 Chevrolet Cobalt.

Starting with the 2.2L variation, GM engineers increased both cylinder bore and stroke by 88mm and 98ram respectively. The engine is expected to deliver 170 hp at 6000 rpm and 170 lb.-ft, of torque over a 2400 to 5600 rpm range thanks to VVT.

The VVT system uses the same hydraulic cam phasers found on the V-6 but can alter the relationship of the intake and exhaust camshafts by as much as 50 degrees relative to the crankshaft.

The new four-banger is also equipped with electronic throttle control and shares the V-6's E67 engine control module.

All analog engine sensors have been replaced with more accurate digital sensors and individual coil-on-plug ignition modules improve upon the two-coil "cassette" found on the original Ecotec. Twin counter-rotating balance shafts are driven by a zero-maintenance chain that also drives the camshafts and water pump.

Leveraging the experience from its NHRA front-drive drag racing programs, GM has fitted the 2.4L Ecotec with several heavy-duty components and systems.

A redesigned cylinder head is improved structurally and has a multi-layer steel gasket. There's also a smaller, more efficient external oil cooler, new camshafts, piston-cooling oil jets that spray a continuous bath of oil on the underside of the piston reducing engine operation temperatures and an enhanced lubrication system that provides for the extra requirements of the VVT and piston-cooling jets, plus a deeper oil sump to handle the potential higher cornering forces.

The Ecotec 2.4L will be built at GM's Spring Hill, Tenn., assembly facility.

 

well you brought me the facts, but i brought the facts to gm when they stated there lil 2.4 makes 170hp but it really makes 150hp so..........who knows that bs they truley have.
but in the other hand im gonna still hold strong on my belief.

 

at the crank and to the wheels are very different things

 

The VVT in the 2.4 is not an "on" and "off" system. The intake and exhaust VVT solenoids control the amount of oil pressure and movement of the cams so the cams move when the ECM senses the need -- can be a few degrees or maxed out (via set parameters in the engine management programming).

 

its actually continous variable vavle timing (CVVT) at least thats what i got outa wiki, and the other reading

 

i like how the title of this thread says (simple) yet there's been many different responses on the subject

 

I believe the "kick" at 4kish that you are feeling is the power enrichment mode.

 

A soilnoid controls the amount of oil pressure going up to the cam "gear". The amount of pressure and flow the soilnoid allows is how much the cam advances. It may feel like a kick at 4K, but that could be because of the cams making a more rapid change to keep the torque curve flat. MIVEC and VVT and VVT-i are all the same idea/princple. VTEC also has variable valve timing but it also another cam lobe to change the lift and I believe duration. The way VTEC should work, when properly tuned is that the HP/TQ curve at the crossover point aren't noticble. They should look like a smooth curve. This creates power.

 

Normal VTEC is noticable no matter what "tuning" is done. Its a completely different cam lobe thats engaged therefor when the crossover point is reached lift and duration is abrubtly increased.

New versions like iVtec aren't as noticable because they now incorporate cam phasers like VVT which can alter the torque output into a more linear curve.

 

Just like simple answers for why life exists and how to attain world peace

 

so let me get this right, you guys are saying vvt can hit anytime because of the senors and pressure n what not, so i would be in vvt at idle and the next day hit it at 6 grand? and actually i took off my muffler and i could tell it pushing more air out around 2500 rpm range, that might be when it starts