Benefits of going VVT-i? Options

[Random_Stranger]

Ok, so I just found out that VVT-i was like dual variable valve timing for HP and TQ. So anyone know how this is beneficial or worse in let's say a 3sgte engine? As I am aware there is a 4th gen engine that has this VVT-i technology (I think).

(I had made a n00b out of myself with the original posting, so I made this thread up to make up for it in another n00bish fashion, but with more to gain from it than my original thread, so my bad.)

This post has been edited by Random_Stranger: Dec 28, 2009 - 6:58 AM

[Supersprynt]

They help overall efficiency. Power, fuel economy, emissions. There's not a whole lot of power to be gained. VTEC is essentially the same thing. Both are timing controllers.

[Random_Stranger]

They help overall efficiency. Power, fuel economy, emissions. There's not a whole lot of power to be gained. VTEC is essentially the same thing. Both are timing controllers.

Oh ok, but don't all variable valve timing on engine by different make have essentially a specific design that separates them? I am certain most of you are saying "Faust! Read on it foo!" but this is just for discussion sake. Because as I said, I failed big time on the original thread and so I just put this up instead. Otherwise I would have just deleted this thread if I had the ability to.

Like, for instance, if VVT-i were included in a newer 3sgte engine, would anyone be interested in that? Just going off of what they know about the 3sgte, and what they know about VVT-i and it's properties.

This post has been edited by Random_Stranger: Dec 28, 2009 - 7:04 PM

[Hanyo]

They help overall efficiency. Power, fuel economy, emissions. There's not a whole lot of power to be gained. VTEC is essentially the same thing. Both are timing controllers.

Oh ok, but don't all variable valve timing on engine by different make have essentially a specific design that separates them? I am certain most of you are saying "Faust! Read on it foo!" but this is just for discussion sake. Because as I said, I failed big time on the original thread and so I just put this up instead. Otherwise I would have just deleted this thread if I had the ability to.

Like, for instance, if VVT-i were included in a newer 3sgte engine, would anyone be interested in that? Just going off of what they know about the 3sgte, and what they know about VVT-i and it's properties.

vvti doesn't really help with turbo charge engines because under boost the air restriction bottle neck would be lessened. VVTi was orginally created to help all motor engine breath better while maintaining torque. This is the same reason why you dont see motorcycle engines with vvti. They don't need torque so everything part of that engine can be geared towards reving up and making a ton of horse power.

Reving a turbo charge engine that high is simply not a good idea.

To really beat a dead horse, vvt was design for all motor engines to shift the power band higher into the RPM range with out the consequences of no torque, bad idle, bad fuel economy.

[Rusty]

vvti doesn't really help with turbo charge engines because under boost the air restriction bottle neck would be lessened. VVTi was orginally created to help all motor engine breath better while maintaining torque. This is the same reason why you dont see motorcycle engines with vvti. They don't need torque so everything part of that engine can be geared towards reving up and making a ton of horse power.

Reving a turbo charge engine that high is simply not a good idea.

To really beat a dead horse, vvt was design for all motor engines to shift the power band higher into the RPM range with out the consequences of no torque, bad idle, bad fuel economy.

did you hear about the tom's tuned altezza came out blacktop VVTi 3S-GE+T , only 100 where made (came out with heaps of toms stuff like ecu airfilter suspension exhaust and among other things) there is also a 3S-GZE (blitz supecharger)

or the updated 1jzgte (vvti turbo) or 2jz-gte (vvti turbo)

[Random_Stranger]

vvti doesn't really help with turbo charge engines because under boost the air restriction bottle neck would be lessened. VVTi was orginally created to help all motor engine breath better while maintaining torque. This is the same reason why you dont see motorcycle engines with vvti. They don't need torque so everything part of that engine can be geared towards reving up and making a ton of horse power.

Reving a turbo charge engine that high is simply not a good idea.

To really beat a dead horse, vvt was design for all motor engines to shift the power band higher into the RPM range with out the consequences of no torque, bad idle, bad fuel economy.

did you hear about the tom's tuned altezza came out blacktop VVTi 3S-GE+T , only 100 where made (came out with heaps of toms stuff like ecu airfilter suspension exhaust and among other things) there is also a 3S-GZE (blitz supecharger)

or the updated 1jzgte (vvti turbo) or 2jz-gte (vvti turbo)

Sweet find! Any specs?

[Rusty]

Rusty's Post

Sweet find! Any specs?

2JZ
280 ps (205.94 kw) / 5600 rpm 44.0 kg*m (431.49 N*m) / 3600 rpm
with VVTi 280 ps (205.94 kw) / 5600 rpm 46.0 kg*m (451.11 N*m) / 3600 rpm
altough you'd have to see dyno runs of both to see the real difference

will try get more info on the tom's altezza

[Edophus]

to get your head round what vvti brings its worth looking at the beams vs the previous gen 3s-ge

cam specs for the gen 3 3s-ge : Cam duration (IN/EX) - 252°/240°

for the beams : Cam duration (IN/EX) - 256°/244°

there not that different, but how does that explain the power difference, the beams cams give a little extra lift, and it has more compression, but generally these are things that would result in a higher peak power but with a loss of torque further down the revs, but because of the vvti the beams makes more power across its entire power band, which is also bigger because of the vvti, and its important to remember you dont drive around at peak power, you have to work your way across the power band in each gear as you accelerate so all that extra torque the vvti brings is beneficial to performance. The vvti means you can run less duration to acheive the same peak power, and less duration improves the low end torque even more. Tuned beams engines all show a lot more torque and power with the vvti still there, removing it just leaves holes in the powerband.

vvti alone is better than lift/vtec alone for performance, because in a hard tuned engine you will probably want to lose the lift mechanism to save valvetrain weight and just run a fixed cam to get the peak power you want, but vvti has proved its worth retaining for the performance gains. Generally the high lift, high duration cams on a 1.8 vtec engine which then produces less torque but more revs, and runs higher gearing to get more torque to the wheels, is no better than a 2 litre with just vvti, but the 2 litre will be more drivable, and probably produce more torque and power overall with greater fuel economy as it doesnt need such short gearing, as in case of the jdm b18c vs the beams, both ulitimatly offer the same level of performance. I think this is why honda were pretty much alone for the most part in there persuit of variable lift, whilst everyone else went for vvti first. Vtec may have sold cars, but ultimatly its a wonderfull engineering excersise in pointlessness

Vvti is also very beneficial for turbo engines, as you can control the gas flow through the engine so much better, you can use vvti to spool the turbo much faster, theres some official toyota documents about the revisions made to the 1jz-gte, they changed it from a non vvti twin turbo to a vvti single turbo, and gained loads of torque low down with better spool times, quite the opposite of what you'd expect to see if it werent for the vvti, the documents highlight the area of the dyno graph in which the vvti made the difference, will see if i can find it.

This post has been edited by Edophus: Jan 7, 2010 - 11:45 AM