V-Tec and DOHC

[Auto_newb]

I got 2 questions:

1) Does F/I go with V-tec well, I heard if I were to turbo my vtec engine, it would screw the v-tec over

2) A friend of mine wants to know if she can make her car a DOHC by swapping her current stock civic head for a b16 head.

[civickiller]

1. idk who you heard that rumor from but FI goes good with vtec and those who say it doesnt is stupid. you might have to adjust vtec engagment alittle but its nothing.

2. no you cant put a b16 head on her stock d series block

[Auto_newb]

1. Doesn't the valve lift let out all the blowing air due to valve overlap?

[Beyond Imagination]

you can use short duration high lift cams if you really wanted.

[Auto_newb]

Umm.. That wouldn't work to well would it? Wouldn't you lose power because since the valve closes early, the cylinder doesn't get filled completely?

[Beyond Imagination]

but you're talking about FORCED induction where compressed air is being used.

[Auto_newb]

That's true, but would it affect it at low RPMs?

[crzyCollegeKid]

well....unless your going with nitrous or a supercharger, your gonna have less power at lower rpms from a turbo setup considering it has to spool. and its vtec, not v-tec.

i saw some dumb mofo with a "S-ER" sticker on his sentra, lets not make such laughable mistakes

(i also saw another dumb mofo with a "DOHC VTEC" emblem on his celica)

[Auto_newb]

So it's kinda "wasting" the !!"VTEC"!! right?

[civickiller]

idk where everybody gets this idea about valve overlap. if hte valves overlap as much as you think then youd lose power. i havent seen anybody lose power from putting cams on there car. it does overlap alittle but its very small. this is a big myth being spread around by people who think they know when they dont really know.

the whole idea with FI is to get as much of the compressed air into the cylinders as you can, ie with cams, intake mani, tb, etc. so why would it be bad to put cams in so you can get more of the compressed air into the cylinders.

[Auto_newb]

So are you saying VTEC will NOT have any conflicts with any form of F/I?

[Privatebigandrew]

OK...let me put an end to this. Forced induction does not like valve overlap. Look at it this way. Compressed air is being forced into the cylinder with the intake valve open. All of a sudden the exaust valve opens while the intake vale is open too. A lot of that compressed air is going to go aout the exhaust valves due to the low pressure on the exhust side from the turbo sucking out the air. Also that air that is in the cylinder is going to want to go out the exhaust chamber even more due to the pressure from boost on the intake side. Now, contrary, a little bit of overlap (such as with VTEC) isn't going to hurt anything. it actually helps spool up the turbo faster by forcing the air out into the exhaust manifold, therby spooling up the turbo. But if you have too much overlap, too much air goes out the exhaust and boost is wasted. The ideal turbo cams would have high lift and short duration.

[YellowITR479]

My car loves the forced induction w/ vtec....wouldnt have it any other way

[Auto_newb]

So if I turbo'd or SC'd a civic, I would have to change cams to just so I don't get this problem or what?

[95TegSE]

Originally Posted by Auto_newb

So if I turbo'd or SC'd a civic, I would have to change cams to just so I don't get this problem or what?

No, the overlap of the stock cams isn't long enough to cause major problems.