Vtec @ 4400 Rpm?

I've read about ECU's that have the VTEC switchover set lower to 4400 RPM.

What would be the negative side of doing this?

Loss of your nice flat torque curve and more than likely loss of power. Honda techs spent a lot of time getting the crossover point just right - why mess with it? The only time a VTEC controller might be required is when you have made dramatic cam changes - and I do mean dramatic :)

you think the honda guys also had to find a balance between performance and efficiency...therefore maybe the fuel map change to accomodate lower vtec x-over lost out to mpg goals/metrics. I actually saw a chip that claimed vtec x-over @ 3800, which seems way to low - the engine would have vtec engagement almost all the time. that has to be hard on the motor over time. I thought maybe 5k would be an ok x-over if I decided to get a chip.

VTEC is meant to kick in when the right oil pressure it set. Setting it lower than it's supposed to be can screw with things. not enough oil pressure for VTEC could end up not being good and lead to problems down the road....maybe even not ever having VTEC work again or at the worst, detonation.:(

Does the oil pressure used to engage vtec happen through mechanical design/fluid dynamics, or is it electronically controlled by a valve or pump? I dont remember reading that in the vtec articles I've seen, or maybe I just passed over it.

ahh ignrance must be blisss, anybody got a home labotomy kit? :rolleyes:



ok, VTEC is controlled by the ECU through a Solonoid which opens to allow oil pressure to push a pin though the rockers, and engage the 3rd arm.
The ECU will not engage it untill the engine has warmed up, or if there is low oil pressure. This has nothing to do with VTEC not working, but the excessive wear it would place on the engine.


Now, to work out where the best engagement point is go read up on cam shafts at www.howstuffworks.com and then go post a thread in the tech forum if you really want to know spefics.

But basicly each cam design has its own power curve, get above or below it and you lose performance.
The idea of VTEC is you can have a low speed and high speed cam, to get optimum power and torque right accross a wide rev range. (since high revs are required for lots of hp, and hp at low revs is needed to make the car drivable on the street)

The ultimate change over point then is just as the low speed cam comes off its peak power curve, and high speed cam enters its power curve.

As was mentioned Honda has spent many hours and millions of dollars getting it right. Infact in the B16a it will change accross a range from about 4,800rpm to 5,200rpm depending on load, gear selection and road speed.
Lowering it may make the car feel faster, as there will be a more noticalbe change when it kicks in, but in reality you will be getting a power drop, and a slower car.
VTEC controllers on cars with stock cams are for rice boys only.
(exception being the VTEC preludes, which for some unknown reason are set a bit high.)

It was a simple question, I just asked if it was electronically controlled or not. And thats what I was getting at - that vtec kicking in too early would maybe put the engine under more stress than designed. Every time there is a question about vtec, people get so pissy like they were the ones who designed it and EVERYONE should know all of the details. I'm a mechanical engineer, and I know some shit (not everything about cars...yet) so please don't talk to me like I'm 5.

Wasn't getting pissy at you mate. you asked a valid question.
I included all basics on a cam because I had no idea as to your level of education. As it turns out, you probobly know more about it than I do. :cool:

I was also being sarcastic towards some of the people who tried to answer when they didn't know what they were talking about.

VTEC is heavily mis understood, mostly by people who dont understand how an engine works, (i.e. what a cam shaft does).
And then because Honda changed it slightly between differnt engines.

As far as I know there are about 4 differnt types of VTEC, which all do slightly differnt things. But all work on the same basic princaples.

:smoka:

Naughty mod pissing people off :finger: :D

I love you moppie :D

Originally posted by ricodemus
I love you moppie :D

:lol2: :sun: :flash: :sun: :flash: :sun: :flash: :sun: :flash: :flash:

MATE!!!

Get a room you two :apuke:

:devil:

Originally posted by Setanta
Get a room you two :apuke:



Somebodys Jelous!!!!!!!! :finger: