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Variable Valve Timing

PostPosted:Wed Apr 10, 2019 7:27 pm
by LPSISRL
Does our J24B engine have VVT? I've always thought it didn't but while looking at engine parts on RockAuto, I saw a part for VVT. Further searching led me to some Grand Vitara specs where it's J24B dioes have VVT. Amsoil's site specs the Kizashi with VVT. I've never had the valve covers off to check and there doesn't seem to be a point where I get a kick in the pants like my Honda V6 does when the VVT kicks in. Also, an edmonds.com guy mentions it as well. The service manual has this:

OBD SYSTEM DESCRIPTION - CAMSHAFT POSITION CONTROL (VVT: VARIABLE VALVE TIMING) MONITOR

Does our J24B have VVT?

Re: Variable Valve Timing

PostPosted:Wed Apr 10, 2019 9:13 pm
by KuroNekko
It does. I recall seeing it listed as a spec for the engine but most VVTs aren't exactly like Honda's VTEC which is apparently a bit more complicated. Not keen on the comparison details though.

Re: Variable Valve Timing

PostPosted:Wed Apr 10, 2019 10:00 pm
by Tom Kizzie
VTEC is like VVT but with variable camshaft. From a certain rpm (lets say 6000rpm) the camshaftprofile changes to a sharper one with more lift.. Resulting in more power.

Re: Variable Valve Timing

PostPosted:Thu Apr 11, 2019 10:23 am
by Woodie
There is variable valve TIMING and variable valve LIFT, two slightly different things. The Honda has both.

Like every other performance parameter, these can be tuned to act in different ways. The engineers can choose to have things act in a subtle way, or to switch on and make the boy racers proud. Intake and exhaust can be chosen in the exact same way, and the effects will feed on each other in synergy. I have a Pontiac Firefly Turbo which you would never expect was turbocharged if it didn't have a light on the dash and stickers on the doors. The turbo is tiny and comes on at very low rpms, running out of steam at higher rpm. It just feels like a torquey four cylinder instead of the one liter three cylinder that it is. All down to the design and tuning decisions that were made by the engineers.

Re: Variable Valve Timing

PostPosted:Thu Apr 11, 2019 4:04 pm
by LPSISRL
From what I understand the Honda VTEC is controlled by oil pressure as well as RPM. Think it kicks in around 3000 if the oil pressure is there. Also, it looks like the J24B VVT is only on the intake side.

The thing I find puzzling is that it's not mentioned in any of the official Suzuki promo materials. They mention the variable intake tube length for better low end torque and multi-point fuel injection, but don't say a thing about VVT. :?:

Re: Variable Valve Timing

PostPosted:Fri Jun 14, 2019 12:51 pm
by dslatsh
LPSISRL I think is right...except it does matter on the year of the car. There's vtec (which was originally out more in i think the 90s cars) and the newer civics use what they call "IVTEC" which is slightly different. The original vtec I know works off like he said oil pressure...once the RPMS hit around 3500 the vtec will "kick in." It is based off the cam lobes. The cam has two lobes for the intake one is a little smaller and the vtec one is larger and shaped slightly different. This causes the lobe during the rotation to keep the intake valve open longer causing more intake of air causing slight performance in the power stroke. It's a pretty cool concept...google it there's videos showing how the engine works. Honda was the first in their time to break history with this invention...other's have tried to copy the idea but haven't succeeded as well as Honda (guessing ya know patents etc). I-vtec I can't remember if it stands for "intelligent" vtec.....but I believe this is more computer controlled rather than RPM/oil pressure combination...the oil pressure is used to shift the lobes into position for the vtec...if i recall.

Re: Variable Valve Timing

PostPosted:Fri Jun 14, 2019 4:45 pm
by LPSISRL
I've seen the video on how the VTEC works and it is quite interesting. I think on some, VTEC works on both intake and exhaust sides On the new Civics, I think it's just intake as exhaust side is not necessary since the exhaust stroke forces the gases out under pressure. Maybe that's the "i" in "iVTEC"? Intake.

Re: Variable Valve Timing

PostPosted:Fri Jun 14, 2019 6:40 pm
by WESHOOT2
Lift, its timing, and its duration, along with appropriately timed fuel delivery and ignition.
Honda makes elegant motors.

Re: Variable Valve Timing

PostPosted:Thu Jun 20, 2019 1:06 pm
by redmed
WESHOOT2 wrote:Lift, its timing, and its duration, along with appropriately timed fuel delivery and ignition.
Honda makes elegant motors.

A little too elegant in the CRV's.

Re: Variable Valve Timing

PostPosted:Thu Jun 20, 2019 1:50 pm
by WESHOOT2
Nobody's perfect :shock: