Dual vvt-i similar to vtec??

[troopa4life]

I have a 2016 sr5 4runner with about 5k miles on it. Today when I applied full throttle from a stop I noticed an extra "boost" of power between the 3-4k rpm range similar to what I have felt in my old 2000 prelude. Is this normal due to the dual vvt-i? I would love to hear anyones thoughts.

Thanks

 

[wfo9]

It's a similar concept with a different implementation. Both increase Volumetric efficiency at high output without sacrificing low output driveability and economy...

You know that lope you hear on a good old v8 muscle car... Well, that is usually caused by overlap in the cam profile. It's very inefficient and bad for emissions, but once the throttle opens up, the valve timing is much more efficient for high output and the motor will scream and put out quite a bit more HP. Plus it just sounds like music to my ears.... LOL It's usually a balancing act trying to get the max HP output, without sacrificing low end driveability with a static cam and valve timing system.

Anyway, both VVTI and VTEC adjust valve timing electromechanically (in a limited way) in a attempt to get the best of both worlds from idle to redline. Pretty sure Toyota uses a traditional cam profile, but the cam gears have an oil controlled phaser which allows for advancing/retarding the valve timing at different engine loads. Honda uses more of a stepped cam that slides and allows for changes in both lift and duration...

One is not really better than the other...and both have evolved over the years. Pros and cons like most things. Most mfgs include some type of VVT these days.

And yes... you can feel it kick in on the 1grfe.

 

[troopa4life]

Wow, great explanation, thank you sir.

 

[wfo9]

Also... (this is a bit of conjecture, so take it as that)

The 1GRFE in the 5th gens has that nice hard pull/tq (as you stated) between 4-5k.... You think to yourself....humm, this thing does have some guts.... but then when it shifts, it feels like it falls on it's face.. Part of that is just the gear spacing and the natural tq curve, but there is most likely more at play...

The ECU typically pulls timing (spark timing... not valve timing) during shifts to limit tq and protect the trans and drive-line. It can also pull the throttle blade back since the system is 100% drive by wire. Overall, this is generally a good thing, but it is often very conservative.. and with Toyota's history of reliability over performance... I'm pretty sure they went way overboard with the tq management. Just like they did with the throttle mapping.

 

[troopa4life]

This forum probably has the smartest most eloquent individuals I have encountered. Thanks again for the response sir.

 

[96r50]

Most importantly don't forget that VVTi is like 4WD. You have to use it for 10 miles each month otherwise it'll seize up and won't work when you need it.






























































:biggrin2:

 

[Antman]

This forum probably has the smartest most eloquent individuals I have encountered. Thanks again for the response sir.

LOL- Most of the newer guys think we are a$$holes.:couch2:




Impotence and vulvas. This is entertaining.

 

[Breadman03]

:drummer:

Most importantly don't forget that VVTi is like 4WD. You have to use it for 10 miles each month otherwise it'll seize up and won't work when you need it.






























































:biggrin2:

 

[77Bronc]

I too am impressed with the performance between 4 and 5K. I just rolled 10K on my 15 TP, 11 months old. I purchased the truck after a very short, 1.5 mile test drive, over 6 months before I made the final buy, I was that confident. Every day I drive it, I like it more and more.

Coming off of a F150 with the 5.4L, it did take some getting used to, but I am good now.

77

 

[BlackWorksInc]

As [MENTION=106176]wfo9[/MENTION] stated, they are similar in principle, but have different approaches.

VVTi (Variable Valve Timing Intelligent) physically alters the valve timing by moving the camshaft sprocket, thus advancing or retarding the entire camshaft X amount of degrees as determined by the ECM.

Where as VTEC actually changes the camshaft profile (changing timing and lift), The way most VTEC systems work is that the ECM locks the rockers to a 3rd more aggressive cam lobe.

(I have no idea why they call this Toyota VVTi because this is Honda VTEC...)

Toyota has recently taken a page from BMW (unfortunately) and started implementing on some engines "ValveMatic" (sounds very similar to BMW's ValveTronic...) that uses both VVTi and a 3rd camshaft to increase the lift and duration of the valves opening while also adjusting timing.

I'm not entirely sold on the new ValveMatic system as it seems to be heavily borrowed from BMW's shelf and the issues they have/had with them have made me wary. The concept is sound though.

And for shits and giggles, here's the "future" :

Because THAT isn't gonna have problems with how often solenoid failures seem to happen in modern vehicles. :bored:

 

[Danimal]

Ford played with soleniod actuated valves in the 80s on the Mustang SVO 2.3L turbo motor. As I recall, the power required to actuate them combined with the number of cycles required (as you mentioned) were issues.

Dan

 

[troopa4life]

Haha you guys aren't a$$holes... just old and grumpy .

LOL- Most of the newer guys think we are a$$holes.:couch2:




Impotence and vulvas. This is entertaining.