Just wondering why Vtec is not included in SI version

[Ivznds]

Hello,

A quick question, we are just wondering and want your opinion.

Best regards.

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[Xlohen]

We have vtc (valve timing control) but it’s not like vtec, vtec is pretty much not really needed with a relatively cheap turbo engine that doesn’t rev higher then 7k, type r and accord have it on the exhaust side mainly just to spool their bigger turbo up faster

 

[Austin@Wunderladen Racing]

There's really not much performance gain to VTEC on a turbocharged engine. It adds a fair amount of complexity to the valvetrain for little benefit. The purpose of VTEC on the intake is to increase mass air flow by increasing valve lift, but with a turbo mass flow can be increased by increasing boost. VTEC on the exhaust side can help with turbo spool performance but these engines are already fairly responsive. The BE and CA heads have VTEC on the exhaust side and I've not seen anyone share results that show all that much difference over a B7 head.

 

[scottgas]

VTEC, variable lift, was used in the '90s and 2000s so Honda could make big specific power from small engines and still have a nice smooth idle and pass emissions. These engines were all naturally aspirated and had high reldines, 8000+, most of them anyway. The power came on at high rpm. Spoon used to make VTEC controllers. Not sure if they still do. It allowed you to control when the VTEC switch over happened. Like the above mentioned, with a relatively low revving engine with a small turbo, variable lift isn't really needed.
Nissan used a weird version of variable lift on the 370 engine on the intake cam and VW uses variable lift on the exhaust cam of the GTI engine.
The biggest reason to use variable lift on the exhaust side is to aid in exhaust evacuation. Big long duration cams aren't very EPA friendly. With a turbo jamming air in on the intake side, the exhaust needs a little help, since it uses smaller valves, in exhaust evacuation once revs and boost climb. Modern engines are tuned to be "good" during EPA testing. the EPA doesn't do wide open throttle high RPM during testing...

 

[cryptolime]

idk but they included it in the 11th gens. just on the exhaust side.

 

[gtman]

idk but they included it in the 11th gens. just on the exhaust side.

And they're slower than the 10th, so there's that.

 

[cryptolime]

And they're slower than the 10th, so there's that.

it's pretty similar. just more linear on the 11th gens and power comes on at lower RPMs. tuned, they likely have the same potential. can't wait to get my ktuner.

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