Conceptually VTEC switches sound good..........

[Sig]

As a performance mod, the idea of having the VTEC open up at lower revs sounds like a great idea. I have only read negative reviews of this device for the NSX, so I was wondering if someone could explain why VTEC switches don't help. My thought is that if this gets you into the power band at lower revs, thus increasing the time in VTEC range, you should get you better performance. So why does this not hold up?

 

[Andrie Hartanto]

My guess is they put the vtec in the high RPM because, at that range of RPM they produces power. It doesn't necessarily give better power at lower RPM that the non vtec does.

 

[Edo]

Basically all that VTEC is, is a higher lift longer duration Cam Profile. This cam profile enables the engine to breathe better at high Rpm's when much a large volume of air is needed. At lower RPM's opening up intake and exhaust valves for longer periods of time doesnt necessarily increase power due to the fact that the engine does not require that amount of air. #2, I'm sure you've all heard that Muscle car down the street that has to constantly be on the gas because it idles so horribly. That is one of the downsides of having aggresive cams(crappy idle and very poor low end performance). The reason VTEC was hailed as being so great when it was introduced was because the low RPM driveability was still there on the "Normal" cams and you could get the extra power from the High RPM range when it switched over to the more "aggresive" cams. Hence the "Jekyll and Hyde" engine persona..

Well, in any case this subject is terribly complex and I dont pretened to understand it all that well. Hopefully this helps a bit, and if anyone here is a VTEC guru, more info is ALWAYS appreciated.

 

[Lud]

Edo explained it well. They do not produce a benefit because there is no real benefit to be had on anotherwise mostly stock NSX by engaging the high-RPM cam profile at a lower RPM. Why? Because the engine has no need for the increased lift and duration at lower RPMS. That's the whole idea behind VTEC - vary the cam profile to you have optimal performance at both low and high RPMs. That is impossible with a fixed cam profile since the engines needs different things at different RPMs. VTEC makes it possible by providing a second cam profile.

The only stock Honda I know of which benefits from dropping the high-RPM cam profile earlier are some VTEC Preludes (4th gen maybe? Not sure.) They engaged the high RPM cam profile higher than optimal for max performance due to emissions concerns.

[This message has been edited by Lud (edited 23 December 2000).]

 

[Jimbo]

Here's what Honda really needs to do...

Do away with cams entirely.

There's been a number of R&D efforts that use solenoids or electronic actuators for the valves. I would love to see Honda run with this technology and make it work reliably.

Just imagine...

Infinitely adjustable intake and exhaust timing with no parasitic losses from all those valve springs and cam friction. No rotational losses from the camshafts, pulleys or belts either.

I wouldn't be surprised to see such a system offer 350 easy hp on the current V6 and god only knows what they could get on the V8...500hp?

They would probably need to adopt a higher voltage system to drive those actuators, but these systems are under development for autos now. Seems like in a few years, cars will be using a 30-50 volt system.

The ultimate VTEC engine...

Jim



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1991 NSX Blk/Blk
1974 Vette 454 4 spd
Wht/Blk

 

[smoothf1]

Renault is already trying a electronic valve system on it's 2001 formula 1 engine.

It's going to be a great 2001 F1 season!

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'91 Black NSX
'87 Jumbo Jet

 

[Edo]

Does anyone know about the electromagnetic valvetrain they had devised a while back?
I know they had some problem getting them toa ctuate reliably over 6000rpm's worth or so..but it was a great idea...are they still trying to develop it?