Hi, I'd like to know how RPM changes when VTEC kicks in. Does it go lower or higher? By how much?

I've a SOHC VTEC so I believe I won't feel the drag as of a DOHC. I do not have any sensors to tell me whether VTEC is on or off.

Anyone has a good URL on VTEC to explain all these?

Thanks!!

 

Not quite sure what you mean by the RPM changing. The only thing I can think of is that it starts heading toward redline faster. That's how mine is. When I hit the crossover, it shoots up to redline pretty quick.

 

yea it doesnt drop it or raise it like you are shifting, it just revs faster

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by amyg12 &raquo;</TD></TR><TR><TD CLASS="quote">

it depends on what car you have.....accord, civic, 4cy, 6cy.....each vtec engages at different points

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yeah well that and it isnt the same every time you accelerate, it depends on oil pressure not just revolutions.

 

variable..hmm...wonder what that means

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by amyg12 &raquo;</TD></TR><TR><TD CLASS="quote">

http://asia.vtec.net/spfeature/vtecimpl/vtec1.html
http://www.hondarevolutions.com/html/vtec.htm

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Great info! Thanks! As I read from previous posts, I get to know that a SOHC's VTEC kicks in at variable timing, regardless of the 4k ~ 6k RPM, which DOHC's do.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Atheist &raquo;</TD></TR><TR><TD CLASS="quote">
yea it doesnt drop it or raise it like you are shifting, it just revs faster

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<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by AccordDX89 &raquo;</TD></TR><TR><TD CLASS="quote">
Not quite sure what you mean by the RPM changing. The only thing I can think of is that it starts heading toward redline faster. That's how mine is. When I hit the crossover, it shoots up to redline pretty quick.

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Well if this is the case then for my f22b1 & my driving style, VTEC kicks in 90% of the time as it revs at 3krpm and I'm only at 110km/h.

Remaining 10% of the time at 3krpm it cruises comfortably at 120km/h.

I hope my assumption is correct though.

Thanks folks for your input!!

Regards,
Chan

 

I think what you are referring to is more of a gearing situation than vtec. I would suggest doing a web search on "torque converter", which is a part of your automatic transmission. This should clear up the differences in speed at the same rpms.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by philadd &raquo;</TD></TR><TR><TD CLASS="quote">I think what you are referring to is more of a gearing situation than vtec. I would suggest doing a web search on "torque converter", which is a part of your automatic transmission. This should clear up the differences in speed at the same rpms.</TD></TR></TABLE>

Hmm...that make sense too, will do thanks bro.

 

Looks like I have some problem with the torque converter.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by www.carcarecouncil.org &raquo;</TD></TR><TR><TD CLASS="quote">

...Lock-up converters also contain a friction clutch that locks the converter impeller to the turbine, usually in higher gears. A solenoid-controlled oil passage, commanded by the car's powertain control module (PCM), locks and unlocks the converter based on driving conditions....

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So I suppose for my case it's only able to lock up "intermittently". Any idea where I should start looking into? PCM? Solenoid?

Now I'm beginning to worry!!

Regards,
Chan

 

What's led you to believe that you have a problem? Is it not driving and shifting smoothly?

While accelerating, the torque converter will remain unlocked. This means that your rpms will be a little higher, and it allows your car to accelerate just a little faster. Now when you're cruising, the torque converter should lock down, thus lowering your rpms and saving some gas. Some people think of it as being similar to an extra gear.

If you car seems to be driving smoothly and you don't have any problems accelerating, I doubt you have any problems with the torque converter, or with the transmission in general.

 

Problem is that the torque converter does not lock down the times I expect it to be, whether I'm stepping hard or accelerating normally. The lock down happens only once in a while.

In addition to this, while driving smoothly, the lock-down could suddenly disappear (felt car jerk) and revolution increases approx. 250rpm. And no matter what I do, the lock down will never occur again if I maintain the speed unless I decelerate or stop then accelerate to try to get the lock-down again.

Yup I thought it was an extra gear.

I'm still quite bothered with this. Appreciate if any of you could help.

Thanks!

Regards,
Chan

 

The torque converter should only lock down while not accelerating. If you're accelerating, even the tiniest bit, it won't lock down.

If you're cruising at a steady speed, and then the car jerks and rpms shoot up like you described, then you might have a problem. First thing I would check is your tranny fluid. How many miles are on the car, and approximately how many miles since the last time you changed the tranny fluid?

Check you tranny fluid by pulling the tranny dipstick and putting a drop of the fluid on a piece of white paper (preferably thick paper). Is it a bright pink color, or is it turning more of a brown color? (or even brown already?) Does it smell burnt? If it's turning brown or smells burnt, have your tranny fluid changed and see if that helps. If the fluid looks fine, and the problem persists or makes you uneasy, take it to a transmission shop.

If I mentioned anything that was just way too obvious, I have no intentions of insulting your intelligence. Just want to make sure I explain it well...