Toyota VVT-i And the Honda V-tec

I believe there similar, are they not?

its fun hitting VVT-I its like a little rocket boost. =)

 

VVT-i (Toyota) and VTEC (Honda) have the same goal in both systems, giving an engine two intake valve timings, one for low RPM and one for high RPM. These are the basic systems but you get into all sort of fancy exhaust and lift timings with other vehicles, I'm just keeping it to our humble trucks. FYI, the new 4.0 V6 FJ Cruiser engine has Dual VVT-i meaning it has VVT-i on the intake AND exhaust.

At low RPMs you want the intake valve shut during the exhaust (4th) stroke so you don't get exhaust flowing into the intake manifold and then back into the piston in the intake (1st) stroke. At high RPMs, the valves are opening and closing so fast that due to fluid dynamics, the ideal time for the intake valve to open is during the end of the exhaust stroke, otherwise not enough air enters during the intake stroke immediately after the exhaust stroke.

The way these two technologies accomplish this are very different though. Basic VTEC is better than VVT-i IMHO.

VVT-i (Toyota) uses a modified camshaft pulley that has two settings, the low and high RPM setting. The pulley uses oil pressure controlled by the ECU to rotate the camshaft connection to the pulley by a few degrees to change the intake valve timing. This keeps the same profile for the intake valve but advances it a few degrees relative to it's low RPM timing. Below is a picture of the camshaft pulley. The oily part is the part that rotates internally in the pulley thus changing the position of the camshaft relative to the pulley by a few degrees.



VTEC (Honda) uses modified rocker arms and two sets of unique cams to accomplish the same task but more effectively. There are two completely different cams on the camshaft for each set of intake valves. The secondary set of cams is selected at high RPMs by engaging a pin in a floating rocker arm that then locks into the other rocker arm(s) and changes from the low RPM profile to the high RPM profile. Below is an excellent illustration.



The thing that makes VTEC better than VVT-i is that the profiles can be completely different with VTEC where as with VVT-i the only thing that can be changed is the timing of the profile.

Some really crazy systems exist for valve timing including a 3D cam profile that Ferrari uses where the camshaft then is moved horizontally through it's axis to change the profile. Even crazier, some vehicles have some electro-hydraulic systems that don't even have camshafts! I'm pretty sure MotoGP uses something to that effect. I'm a huge dork and love this kind of stuff but I don't want to bore you all with more rambling. If you want more info just search Ferrari 3D cams or MotoGP engines.

Where I got my pictures from.
VVT-i
VTEC

 

Sorry, couldn't resist posting info about the Ferrari 3D camshafts...

http://www.physicsforums.com/archive/index.php/t-109476.html

 

Thanks for the excellent post Xpdishun. I knew the basics but not that deeply. Now I guess that the new double vvt-i is the same thing, but applied on both camshaft. Also, I always thought that vtec was applied on both the intake and exhaust cams, I guess I was wrong.

 

Thanks, man, appreciate it!

I think you are right about VTEC for DOHC engines but for SOHC they only had it on the intake valves. VVT-i however was only ever on the intake even for DOHC until the Dual VVT-i.

 

VTEC and VVTL-i are similiar.

It's Lift technology. I have this motor in my 2005 Corolla XRS. At 6500 RPM it takes of like a rocket until it redlines at 8200 RPM.

Same motor in the Celica GT-S and Lotus Elise.

Marc M

 

Good call Marc M, VVTL-i is VVT-i plus a mechanism to engage a second set of cams. A pin of a different type slides in to engage the second camshaft also using oil pressure. Here is an illustration.



VVTL-i is one better than VTEC because it maintains the special camshaft pulleys VVT-i has. i-VTEC is Honda's answer that has their VTEC rockers plus camshaft pulleys similar to VVT-i's.

Sadly, the Tacoma only has VVT-i. The Honda "competitor", and I use that term loosely, the Ridgeline only has SOHC VTEC. They seem to reserve the high tech camshaft technology for more performance oriented applications. Fine by me though, keeps our engines more bulletproof.

Where I got the picture from.
http://www.corlutuning.com/index.php?topic=6377.0

 

@xpdishun - have you heard about upgrading VVT-i engines to double VVT-i?

in Europe we have 4.0l V6 with double vvt-i in new Land Cruiser Prado 150 - you can really tell a difference when driving it compering to old 4.0l in old Prado 120. I'm going to buy Tocoma and I'm considering different ways to increase it's performance.

 

HOLY Thread REVIVAL.

 

Thread revival or not, there is an error in xpdishun's description of VVT-i.
His claim is that VVT-i has two positions for high and low RPM. Actually, those two positions he mentions are just the two extremes. There are virtually infinite variations between those two extremes. The specific position is selected by variable oil volume pumped in to the unit.

What makes VVT-i better than VTEC is having the full range available. VTEC has only a number of fixed profiles. When driving a VTEC engine, you can feel when it changes profiles by abrupt changes in torque. With VVT-i, you can't feel the transitions since they are gradual.

 

While this is true that's exactly the reason i-Vtec was invented. My old Honda Prelude had a DOHC H22 Vtec engine. At 5000rpm the engine dyno graph shows a damn near vertical 30whp jump on the line. You could feel/hear it in the car. Vtec is a VERY effective system but it's less refined. It's a kick in the pants. The i-Vtec is a more variable system so it's less explosive at any one given point.

 

kindof a geek too. in all my thinking on this stuff i would never have thought of a 3D cam profile! i was stuck on electro/hydraulic actuator thingys for each valve.

ferrari; and to think too many of the people that have one only know that it was an expensive car.

 

Toyota had a similar system to Honda's i-VTEC in the older Corolla XRS and Celica GT-S, they just called it VVTL-i. Not quite like true i-VTEC where the low lobes on the same cam have different profiles to induce good swirl at low rpm, it was more like the VTEC system on the L15A7 Fit engine where it had one lobe to drive 2 valves and it locks both to the high lobe when engaged. I would have bought one of those XRS corollas if I'd have found one for sale, they're stupid fun to drive.

http://www.turbomagazine.com/features/0106_turp_honda_vtec_vs_toyota_vvtli/viewall.html

Yeah old thread, how did ya dig this one up anyways

I wish the 1GR was VVTL-i, that would be fun!

 

I dig it out when searching for info on upgrading VVT-i into double VVT-i.


VVTL-i never existed in 1GR, but as it exists in both VVT-i and bouble VVTi versions - maybe an upgrade from single to double is possible.

 

Actually, VVTL-i predates i-VTEC by one year.

VVTL-i is basically VVT-i + VTEC.

iroh: VVTL-i is practically identical to i-VTEC. The difference you are pointing out is only in the number of cam lobes, which varied even among different i-VTEC engine configurations. Toyota only made two engines with VVTL-i, if they had pursued this tech further, they probably would have made some different configurations.

 

Not without replacing the heads and ECUs. Possibly also some wiring.

 

You sure about that?

 

I didn't see someone posted VVTL-i ...three years ago. Oh well, we're talking about it again!

Yeah there are multiple i-vtec versions. Honda doesn't give them all their own distinct names anymore like they used to. They put the new cam gear on a vtec-e head on certain k-series engines (2nd gen Si, CR-V, etc), and called it i-vtec on the valve cover. The RSX-S, 3rd gen Si, and TSX had three lobes per cam per cylinder and got the same i-vtec name, which I suppose is ok because when it started the 'i' supposedly referred to the infinite adjustability of the cam gear and the 3D 'intelligent' timing maps it took to run it. Even the L15A7 engine which only has lift change on the intake side with only two lobes per two valves and a FIXED cam gear gets called i-vtec. At least with the L15A1 they were almost right, no 'i', but it should have said vtec-e instead of vtec.

I guess the only one they're still honest about is the J-series V6, it still runs a timing belt and they can't put the 'i' on there without being called liars.

It's all for sales...

Though I gotta say the nice torque bump on conventional 3-lobe vtec is a real blast to drive. If you want that in a relatively recent production car, get the previous-gen Si with its K20Z3 engine. The drive by wire may suck, but from 6500-8200 rpm it's a screamer.

 

Someone trying to do a Toyota mini-me?

That's in reference to people putting d16z6 or d16y8 vtec cylinder heads onto d15b7 blocks. The block was a different casting, but the bore was identical, the head bolt holes lined up, and the oil passages matched (there was a restrictor that needed to be removed but that was it). Easy 20% hp bump.

 

They did a similar thing with the H22 head on the h23.