V-Tec and DOHC

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.

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

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

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

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?

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

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

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 :D

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

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

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.

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

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.

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

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?

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.

Turbo is fine with vtec. Turbo is all about flow, and vtec and vtec heads flow better.

So on a VTEC engine/head, I could just bolt on a turbo with no worries? No special modifications or tuning is required?

the majority of mods require tuning, especially a turbo.

No, you have to tune it, you have to tune it on a SOHC non vtec.

No, you have to tune it, you have to tune it on a SOHC non vtec.

wtf are you talking about, so what your saying is if you putting a turbo on your dohc vtec motor, he should tune it for a sohc non vtec, that is ridiculous.

tune it on hte motor you put the turbo on

I think he was just pointing out that any turbo application requires tuning, even on motors that have a single cam and no cam overlap or VTEC.

Alright thanks for the responses, I have no questions, yet...

wtf are you talking about, so what your saying is if you putting a turbo on your dohc vtec motor, he should tune it for a sohc non vtec, that is ridiculous.

tune it on the motor you put the turbo on
Go choke yourself.

You have to tune a turbo whether you put it on a SOHC non vtec or a DOHC vtec. Learn reading comprehension.

No, you have to tune it, you have to tune it on a SOHC non vtec.

ok so i need to learn reading comprehension huh, you didnt say you have to tune it whether you got a sohc non vtec or dohc vtec. you said you have to tune it on a sohc nonvtec, why dont you try and read what you write. maybe you need to get some reading comprehension because his post is about dohc vtec and turbos, not sohc non vtec motors, then you say you have to tune it on a sohc non vtec

your exact words, you have to tune it on a sohc non vtec. how does that in any way say that you have to tune it whether you have a dohc vtec or a sohc non vtec ? all i see you saying is that you need to tune it on a sohc non vtec and then put it on yoru other motor which would result in a blown motor.

he may have tried to imply that but he didnt say that. and guy you dont need to get all defense just because you said something wrong

I know it is complicated, but try following the conversation....he ask...
So on a VTEC engine/head, I could just bolt on a turbo with no worries? No special modifications or tuning is required?
and then I said...
No, you have to tune it, you have to tune it on a SOHC non vtec.
Having reading comprehension would allow you to see that what I said was in relation to what he asked.


Because you seem so perplexed let me rephrase what I said...

No, it doesn't matter if it's on a DOHC vtec or a SOHC non vtec, you still have to tune it.

Same thing you see, but I added the part that was infered, the part your mind can't seem to just add by reading the whole thread and considering it a whole conversation instead of seperate unrelated phrases.

you see he asked for a vtec head, and if any tuning was required

you said yes, you have to tune it on a sohc non vtec.

now if i didnt really know that much about engines and tuning by that statement i woudl think hmm i got a sohc or a dohc vtec but i have to tune it on a sohc non vtec. dont you see that ?

like i said you might have ment everything needs to be tuned no matter what engine, but you didnt say that, you said for a vtec engine you need to tune it on a sohc non vtec.

when you giving some people advice you cant infer critcal information like that, a newbie wouldnt know enough to infer that.

1.No, you have to tune it, you have to tune it on a SOHC non vtec.
2.No, it doesn't matter if it's on a DOHC vtec or a SOHC non vtec, you still have to tune it.

you said those 2 statements, now does the first one say the same thing as the second one, i dont think so.

dont talk to me about reading comprehension when you cant even see exactly what you said and that it might have led him in the wrong direction or to possibly a blown motor if he followed what you said

Since you still don't get it, and obviously aren't taking into account the whole thread you attempt to make me seem wrong is retarded.

The guy asked if he could bolt it onto a vtec head with no tuning, I said "no, you have to tune it", and then stated the you have to tune it even on a SOHC non vtec, as in if a SOHC non vtec needs it to be tuned, than a DOHC vtec will too. Are you really that dense?

jesus christ you guys argue more than kids in the 3rd grade...

on a lighter note... how noticeable is your changeover to vtec yellowitr?

this is what you said.
No, you have to tune it, you have to tune it on a SOHC non vtec.

if you had said this
no, you have to tune it, you have to tune even a sohc non vtec

then it would have made sense, but the way you stated it says he has to tune his vtec motor on a sohc non vtec.

stop looking at what you meant to say and look at what you actually did say.

now this is a good statement.
No, it doesn't matter if it's on a DOHC vtec or a SOHC non vtec, you still have to tune it.

It's sematics, now stop your whining.

your the one who told me to go choke myself, and to learn reading comprehension when you could so just said opps thats not what i meant, and could of just changed it easy. but you had to go off on it.

civickiller, shut the fuck up dude, you're arguing an utterly moot point. it's dead, move on.

at any rate the question was answered long ago, VTEC does NOT have any problem with boost.

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.

:banghead:
You are mistaken. The turbo does not "suck" air out of the exhaust. If it did, it'd be a mythical perpetual motion machine, since it is both performing work by creating vacuum and creating pressure with no outside power. If it did suck exhaust out, no one would ever buy a supercharger, because they would be FAR inferior to a turbo. Quite the opposite is the case - the turbine wheel on a turbo is a restriction in the exhaust, so there is pressure - not vacuum - in the exhaust pipes. This pressure is normally higher than the boost pressure the turbo creates, unless you have a very large exhaust turbine on your turbo, in which case you have a lot of lag! This is the reason why turbos like small overlap - the exhaust pressure is higher than the intake pressure, so if both valves are open, the exhaust is going to push into the cylinder and prevent the intake from coming in. Obviously this means less area for the intake charge to take up after the exhaust valve closes. The earlier the exhaust valve closes, the less exhaust is going to enter the chamber.
The concept of VTEC itself is not a bad thing for turbos. Just like any other stock n/a motor, its simply not cammed for best turbo power. A turbo will work fine on a vtec motor, but it'd make more power with new cams. I bet you could get better turbo performance if you increase your LSA. LSA(lobe seperation angle) is the distance(in degrees) between the peak lift of the exhaust valve and peak lift of the intake. If the LSA is increased, that means the exhaust closes earlier and intake opens later, effectively reducing overlap. Unless you know what you're doing and know how to return the cams to their original positions, don't attempt it.

Oh and by the way, if you put smaller lift/duration cams in the motor, your low end power will increase, high end power will go down.. but if you're turbocharged, that doesnt matter, the turbo will make up for the low lift.

If the LSA is increased, that means the exhaust closes earlier and intake opens later, effectively reducing overlap.
Or you could just get adjustable cam gears.

i must have got some bad info from somewhere....thanks for clearing it up. we kinda had the same concept going on. But, superchargers are inferior to turbo's when it comes to efficiency.

Or you could just get adjustable cam gears.

I assume adjustable cam gears let you adjust the timing of each cam, which is exactly what I was implying :)