Hi Guys & Gals!

I'm having a conversation on an motorcycle email list that I subscribe to regarding valve adjustments on VTEC engines vs non-VTEC engines. As part of this conversation, points have been mentioned about whether both intake valves open completely, one completely open with the other partially open, or one completely open with the other not open at all.

I know that my '01 Odyssey opens one intake valve completely and just cracks the other off the valve seat when running on the low speed cam profiles. I've always assumed that the S2000 opens all it's valves the same, the only difference being what the lift, duration, and actual valve timing will be depending on which cam profile the engine is running on. Now I'm not sure.

Can anyone confirm what the S2000's intake and exhaust valves are "really" doing when running on the low speed cam profiles?

Thanks & Drive Safe,
Steve R.

 

Aw, come on folks, nobody's got any idea?

Drive Safe,
Steve R.

 

I think they lift sooner when VTEC engages.

 

vtec causes the cams to change to a more agressive cam with more overlap at about 6000rpm
\it acts on all the valves as does the smaller cam
cheers
Paul

 

honda has many vtec systems.

the performance type is what we have, AKA "3-lobe" VTEC
in low speed mode, each valve is opened at a different height via low and mid lift lobes. each valve IS LIFTED BTW. The effect is to swirl air into the chamber. In high lift mode, both valves switch to the high lift lobe and are opened to the same height. Both the intake and exhaust valves have this system.

Then, there is the lower performance VTEC, AKA "2-lobe" or VTEC-E
In this system, during the low speed mode, one valve is opened via the high lobe, the other JUST BARELY via the low lobe. In high speed mode, both valves are opened by the high lobe. Cars with this system only have it on the intake side. NOT on the exhaust.

ALL SOHC hondas have either 2 or 3-LOBE vtec on the intake only. Base K motors have 2-lobe on the intake only and the cam phaser on the intake cam (the i in i-VTEC). Hot K motors have 3-lobe on both sides AND the cam phaser on the intake cam. The cam phaser has yet to be used on the exhaust cam.

 

Hi Steven975,

If I'm reading you correctly, there is a slight difference in valve lift on the intake valves when running on the low speed cam profiles for the S2000. That's what I was wondering about!

Your description of the VTEC-E sounds exactly like what the shop manual on my Odyssey describes. My limited understanding of the actual mechanics of implementing VTEC had me thinking that all of them were 3 lobe systems but I can see where a 2 lobe system would work in this case.

Thanks for the clarification!

Drive Safe,
Steve R.

 

http://auto.howstuffworks.com/question229.htm

 

I appreciate the link WhiteS2k but understanding the fundamentals of what VTEC does is not my problem. I was just wondering if anyone could clarify the finer points of what's actually going on with the valves "beyond" the fact that there are multiple cam profiles to play with. I think Steven975 got it!.

Drive Safe,
Steve R.

 

yea, the valves are opened at differing heights in low speed mode, but both are lifted nonetheless.

 

The reason the S2000 has a great idle at lower rpms is because of the mild cam, at the higher rpms the more agressive lobe of the cam kicks in and that is where the racing cam comes into play.