Does VTEC have....

[zerocool78]

Hi,

I just read and understand how DOUBLE VANOS works. Single Vanos only control the open of inlet valve, where double vanos control both inlet and outlet valves.

If compare to vtec, it only controls the inlet valves (am I right?). If so, when will HONDA comes out with ones that controls the opening of outlet valves. (or this already in I-VTEC)

Just wondering though... thanks..

 

[hattech-v]

u mean inlet = intake, outlet = ekzos?

 

[shiroitenshi]

the exhaust is not very important I think, because of the fact that closing the valve later during the exhaust stroke might result in a meeting of valve + piston and opening it earlier results in compression loss. SAAB even makes a block that can make good power by varying compression ratio.. but the system makes too little power increase for the cost to make it marketable.

That's why variable cam timing and lift on ferarris not implemented on other types of cars... they cost TOO MUCH to make.

I haven't seen a variable exhaust cam timing system yet, so consider the above uninformed opinion.

 

[zerocool78]

shiroitenshi,

Thanks for the explaination, as my understanding from the beemer website is that it D-Vanos do feel alot of different compate to S-Vanos. Hmm... who knows one day Honda might do that when the technology is cheaper than.. [:D]

 

[albani]

oo...i thought we oso does have different cam profile at exhaust...in fact xtually vtec only on the intake ka? huhuhu..now i know

 

[amdfaisal]

from the i've got from the net, DOHC VTEC implemented in B series engine activates on both intake and exhaust valves. If you look at the camshafts, you will see three lobes for each set of intake and exhaust valves... 2 lobes are for normal 16-valve operation while the other lobe is for the actuator that will move in unison when VTEC engage (when the solenoid is activated -> oil -> pin -> etc etc)

for SOHC VTEC, only the intake part is concerned. too complicated to implement VTEC on exhaust side i suppose.

For i-VTEC, only the K20As found in the type Rs have VTEC on both intake and exhaust.

you can refer to this web page if interested...

http://www.leecao.com/honda/vtec/index.html

correct me if i'm wrong

 

[shiroitenshi]

from the i've got from the net, DOHC VTEC implemented in B series engine activates on both intake and exhaust valves. If you look at the camshafts, you will see three lobes for each set of intake and exhaust valves... 2 lobes are for normal 16-valve operation while the other lobe is for the actuator that will move in unison when VTEC engage (when the solenoid is activated -> oil -> pin -> etc etc)

for SOHC VTEC, only the intake part is concerned. too complicated to implement VTEC on exhaust side i suppose.

For i-VTEC, only the K20As found in the type Rs have VTEC on both intake and exhaust.

you can refer to this web page if interested...

http://www.leecao.com/honda/vtec/index.html

correct me if i'm wrong

Yup.. you're right on that one.. but D-vanos plays with the timing (I think).. like you play with the adjustable cam pully.. it's also that cam timing advance thing that you see on the RB26DETT, AE111 engine (or was it 101?) It's fully variable, unlike VTEC which is an on-off system. Notice that the thing I mentioned is ONLY PRESENT on the intake side.

Remember that the OLD VTEC is not a Variable System nor has honda claimed it as such.. It switches to different cam profiles to provide more lift and duration.. that's why it's not smooth, and you can feel the kick when VTEC engages.

I'm totally clueless with i-VTEC.. so I'll refrain from commenting about that one.

 

[hattech-v]

i-vtec stand for innocent vtec actually....

 

[zerocool78]

amdfaisal,

Thank for the info. So now I can rest my case..

 

[Oderf]

from what i know, i-vtec will give smooth vtec transition....thats mean u won't really notice when the vtec kicks in.....correct me if i'm wrong

 

[amdfaisal]

smooth VTEC transition for the i-VTECs in the new civics/accords/CRV/stream i think since it's the transition from 12-valve operation to 16-valve operation as seen in D15B and also D17A. refer http://asia.vtec.net/article/k20a/index.html and http://asia.vtec.net/article/ivtec/index.html

for those high perf EP3, DC5, CL7 (not that fast), a different approach was taken. these K20A R are permanent 16-valvers with a switch of profile depending on the rpm (engine load). This profile switch occurs on both intake and exhaust.
http://asia.vtec.net/article/MME2004ET1/index1.html

if u read american forums... lots of ppl are dumping their normal K20As for the 'R' K20As... different tech altogether and of cos different power le...

and yup.. add that VTC thingy also... to improve low-end + mid-range


just my comprehension from the articles read

 

[albani]

ok....now im corrected...thats explain 3 lobes on the exhaust cam :)

 

[harpoon]

the dohc vtec system for b-series consist of vtec cam for intake and exhaust. it's operation as though you have 2 set of cam in one. it's change over point is preset by ecu, hence like on-off switch.

wherees for i-vtec, you still have the same vtec cam for intake and exhaust plus vtc function, it's as though you have adjustable cam pulley, the best part is it's adjustable on the fly.

combine both vtec and vtc, you will get better performance because there will be two performance lobe overlap. the reason you don't feel much difference when vtec kick in is because the vtec is set to engage at lower rpm, and after vtec engagement, vtc will still be adjustable.

honda is already in the stage to introduce avtec (advance i-vtec) something even better