MikeyCB

Just rubbbbb it in. $$ prevent that for many of us, my friend. I'm jealous

SpitfireS

carrera4 said it first... actually.
carrera4 Posted: Jan 3 2008, 07:21 AM
I guess we're talking about the same website / webpage.
Allthough Hondata doesn't really specifically mention the S2000 / F2x ECU, well.. I could not find it.. is there a link?

Anyway...

IMO "VTEC" is more then one thing.
There is the mechanical side with the cams and rockers and locking pistons sliding over and there is the fuel and ignition side.
Lots of variables creating lots of possible situations.

Engaging VTEC, the mechanical part that is, uses little oil and only once - during actual engagement.
IMO it takes about a cubic inch in total, 2 at worst, those locking pistons are small and the stroke is not much.

So.. IMO, the OP's engine failed due to low oil level.
Period.
Changing lanes or driving over a bump may had been enough for the oil to be slushed away from the pickup point and at the revs the engine was at it means... what the OP allready knows.

Now... we need data!
Lets Bust The VTEC Engagement Myth.


Modifry's VTEC Led page

MikeyCB

I'm aware of how the little pistons engage and disengage the lobes, but are you sure they don't require constant oil pressure to remain engaged?

If you accelerate up to 9K (obviously engaging the VTEC) and remove the throttle without shifting and allow the revs to slowly fall below the disengagement point, will it remain in VTEC until you give it a some gas to raise the oil pressure again?

It's a total assumption since I've not disassembled a VTEC head, are the little pins not retracted in their natural, resting state?

RedY2KS2k

First, to ChefJ:

I wasn't trying to be difficult. You can demonstrate that my opinion is wrong and I won't consider it rude.

To everyone else:

I made this much more complicated than it has to be when I suggested an LED. Can't the basic question be answered by a test drive with the wire disconnected from the vtec solenoid? Either the car will accelerate gently to 75mph in 3rd gear (AP1) or it won't.

I'd like to have more information regarding the normal vtec engagement that can't be gotten with the solenoid disconnected, but that would answer one basic queston.

RED MX5

MikeyCB, I'm lazy at every possible opportunity, but finding time for being lazy is harder than finding time to play around with the cars. Things have been a little crazy around here, for almost a full year now, and some of the hobbies have had to be put aside for a while so I can' deal with other, presumably more important matters.

But I'll admit it; I am being lazy. Hooking up a volt meter wouldn't take five minutes and a short drive might take another 10 minutes, and rather than doing that, I'm sitting here relaxing and shoothing bulls with you guys.

RED MX5

Rather than saying that "VTEC is more than one thing," I'd say that VTEC is a complex subsystem. The system itself is the entire "engine management system," which would include the ECU, all the sensors, all the controls, and all the software.

Using those terms I'd say that your depiction of the VTEC subsystem makes sense. A valve opens allowing oil pressure to push on pins that move into a position that locks each cylinders cam followers together so that are all three ganged to the central follower, which rides on the more aggressive central cam lobe. No oil is lost, as it isn't oil that pushes on the pins; It's just oil pressure. When VTEC disengages the oil either stays in the passages (but no longer under pressure) or drains back into the oil pan. No doubt it does a little of both.

On the electrical side, it's all about the software, so the possibilities are endless. Think about a car like mine, with FI, running alongside a totally stock S2000, with both engines turning 7,000 RPM. At this speed I'm getting some substantial boost, so to maintain the constant speed, my throttle has to be closed more than the stock car that is running along beside me. I'm also pulling a slightly greater load, because I'm using some power to turn the blower, so my MAP will be different. So my ECU is seeing a smaller throttle opening and a higher load, both of which might come into play as the ECU decides which cam profiles to use.

BUT, I don't think we need to look at the software or a flowchart to figure it all out, because data logs will show us what's happening, at least at the functional level.

RedY2KS2k

I agree that the solenoid acts as a valve that opens the path between a pressurized oil gallery and the pins in the rocker arms. As long as the path is open, the pins are pushed out by oil pressure. When the signal stops, there must be a way to bleed off the pressure. Simply closing the valve and trapping the pressure on the rocker arm side of the solenoid probably wouldn't suffice.

I've never really cared much about the details before this discussion, but I do find this one interesting.

RED MX5

There are springs that push the pins back during disengagement. I suspect that some of the oil is simply pushed out past the pins, as they do not seem to be sealed in any way. Once pushed out, it mixes with the rest of the oil up in the head, and then drains back down into the oil pan. I also suspect that the path between the valve and the pins may remain full, or mostly full, of unpressurized oil, so the total oil moved when the VTEC valve opens would only be equal to the pin displacement. Eight little squirts.

I agree that these issues are somewhat moot, but they are still interesting.

LostMotion

RedY2KS2k

What you describe is what I expected, but I've never looked. I expected that the pins don't seal particularly well, and a little oil leaks past them the whole time they're pressurized. As you said, the oil just drains down to the sump, no harm done.

VTEC was a masterpiece of engineering: so simple that every person on the planet couldn't believe that they didn't think of it first, but very effective. Other systems may have surpassed VTEC (some of the continuously variable valve timing systems) but VTEC was a masterpiece of engineering in its day.