MikeyCB

So with all this ongoing talk about changing gears, I had an idea.

People talk about how the one drawback to changing to an "aggresive" gearing like 4.77 is cruising on the highway with the engine in VTEC. Obviously this wouldn't change the engine speed, but has anybody put in a switch to cut power to the VTEC solenoid so you're running on the more fuel-economical (but less power-producing) cam lobes at higher RPMs? I imagine this would assist in greater fuel economy, and cut some of the noise when you're looking for a nice easy cruise.

I can't think of any drawbacks to this really. Can anyone else?

Scott64

Unless your throttle is open wide enough to allow increased airflow to the engine, you're NOT in vtec....basically unless you're accelerating, you're not in vtec so don't worry about it.

Ustemuf

you'd have to be going over 95mph in 6th gear with 4.77's before vtec engaged.

afwfjustin

If you're in VTEC on the highway with 4.77s... then you are a maniac. You'll be going nearly 100 mph. 4.77s are only 800 rpms over stock in 6th gear. Highway driving is quieter than stock if you have aftermarket exhaust because it brings the revs up above the droning range.

I've had them on my car for 4 months or so and I cannot stress how awesome they are. If I could go back in time I would have ordered the 4.77 diff BEFORE I got my S so I could immediately put them in. They'll be off the car in a few weeks ago as I'm prepping for turbo now.

Spec_Ops2087

Vtec takes into account many variables, not just engine rpm. If your cruising at 120mph (why would you be cruising at this speed?!) the engine will not engage vtec.

MikeyCB

Hmm, I'm not so sure about that.

Regardless of whether you are at full throttle or not, as long as there is enough oil pressure and you are above 6K RPM, then you are in VTEC. At part throttle you aren't using as much fuel (and air) as if you are at full throttle, but you're still utilizing the VTEC cam lobes.



Wow, didn't realize you'd have to be going that fast, why do I hear about people hating that they're cruising on the highway in VTEC after gear changes?

Scott64

If the vtec in the F20/F22 requires the same conditions to be met as the B18Cs, then what I said is correct.
In the B18Cs there are 5 conditions that must be met for vtec to engage:
Temperature: The engine must have reached normal operating temperature.

Throttle Position: The throttle must be open far enough to allow for increased airflow in VTEC.

Vehicle Speed: The car must be in motion (wheels spinning).

RPM: Engine must spin to it's target value.

Oil Pressure: The engine must be operating with normal and safe levels of oil pressure determined by the VTEC pressure switch.

(engine conditions copied and pasted from team-integra.net so I wouldn't have to type them out myself)

If vtec in the F20/F22s are different, I'd be very interested to know the differences so I don't spread misinformation in the future.

MikeyCB

Well I could be wrong, but I know that even at part throttle when I'm driving my car and it passes 6K there is a definitely changeover.

That's the only point that I'd debate from that list. In fact, I'll confirm it tomorrow on the way to the office!

-KEY!S2K-

I had 4.77s and you definatly do not have to be going that fast in 6th to be in VTEC

Scott64

Not to sound like an ass, but how about we don't go by what the butt dyno tells you. Hook up a vtec light (even just temporarily) if you really want to know for sure. I believe it's 1 wire to the vtec solenoid and 1 to ground. When you hit vtec she lights up like a Christmas Tree on the 4th of June.

And it's not that you have to be WOT, but the throttle has to be open enough to allow increased airflow. Is there no one who knows for certain how, if any differently, vtec works in the s2k?