What happens at 3400rpm?

[maximapitko]

Hello guys,
I've noticed that around 3400rpm the sound of the engine changes a bit and I can deff. feel a little kick in the power. You can reallly feel/hear it in 2nd gear(manual). I know it has something to do with the vvt-i but I was wandering if somebody here can go technical on the topic. Also, I've noticed that the fuel economy goes down quite(sp?) a bit if I go beyond 3400rpm. Thank you!

[Impresive-G]

The higher the rpm, the more power is produce. The kick you are feeling is the vvti. Look for a web site, i think its called howthingswork.com and type in vvti. To long to say. But the higher the revs are the more gas you are burning and the more longer you keep emthe revs up their the more oil you burn.

[eTiMaGo]

I think at that point there starts to be a bigger rise in the torque and power output, so it feels like a nice little kick as the engine "wakes up". You can look at this dyno graph and see the torque (dark blue line) rise a little between 3000 to 3500rpm. It's not a huge difference, but probably the reason for that feeling.



(thanks to ChinoCharles for the graph)

[spkrman]

yea, 3000+ is where the motor is when hamster #1 wakes up hamster #2 and #3, #4 only kicks in after 5502 RPM.

[YamilR]

Maybe someone could explain this video better than me

http://www.youtube.com/watch?v=9A6S1NUjg_A

[60 Somethings]

This area of "kick" is the engine's Power Band that I referred to in the "Downshift two gears at a time thread".

[07WYarisRS]

VVT-I changes the valave timing and compression according to engine rpm

Too much valve overlap makes for poor low end performance and rough idle.
But a cam with more overlap an/or longer valve duration (how long it holds the valves open) is better for top end performance.
VVT-I allows the engine to run two several cam timing settings.
Basically it's like having two intake cams. One normal and one performance cam.

The VVt-I is set to normal below such and such rpm and this allows for higher compression and less overlap for more efficient low rpm combustion giving the best low end performance and toruqe for off the line HP. But top end performance is limited by the compression and valve timing.
When that set higher rpm range is reached (3000rpm+) the VVT-I automatically changes the cam timing for better top end performance just like adding a performance cam would this also slightly lower the compression which is also better for higher rpm operation.

VVT and VVT-I are a little different because the VVT has only two set cam timing settings, normal and advanced. The VVT-I uses compters and sensors and adjust the cam timing where ever it needs to be for the best performance for the rpm range the engine is running.

With out the VVT-I and different cam timing this engine would not likely push over 75hp.

This is also what our engines do not need high octane fuel....
Cam timing plays a HUGE roll in compression levels. Our engines compression may be 10:1 at 200 rpm (cranking speeds) but at 6000 rpm with the extra cam overlap compression levels will be much lower

[Doc Zaius]

I'm definately no engine expert, but what I believe 07WYarisRS is referring to is VVTL-i, where the L stands for Lift. Our VVT-i engines in the Yaris simply change the valve timing, either advancing it or retarding it as needed... the valves stay open the same length of time regardless. With a VVTL-i engine (or Honda's VTEC), the duration that the valves stay open, as well as the time they start to open, change. Please correct me if I'm wrong. Wikipedia article on VVT-i (and VVTL-i).

But, back on thread topic, it appears that around 3,500 rpm the torque definately increases, which is why you get that "kick" feeling.

[07WYarisRS]

That's correct.
got thinking about too many different systems there..

The VVT and VVT-I are pretty much the same, the big difference being VVT is an on off kind of advance. for instance if it advances the can timing 10 degrees, once it is activated it advances to 10 degress until it is back off to normal
Where the VVT-I is verable meaning it can adjust + or - from 1 -10 degrees depending on engine rpm.

Valve lift/duration is controled with VVTL-I /Vtec systems

[Blenjar]

Originally Posted by YamilR

Maybe someone could explain this video better than me

http://www.youtube.com/watch?v=9A6S1NUjg_A

That was nice..thx dude..

-- Blen

[Jem_hadar]

Originally Posted by spkrman

yea, 3000+ is where the motor is when hamster #1 wakes up hamster #2 and #3, #4 only kicks in after 5502 RPM.

LOL

[eTiMaGo]

Originally Posted by spkrman

yea, 3000+ is where the motor is when hamster #1 wakes up hamster #2 and #3, #4 only kicks in after 5502 RPM.

Ah, so it IS a 4-hamster engine!