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The dynamic compression is achieved by allowing the intake valve longer time in closing. Bleeding off some of the air. The r18 still has a static compression of 10:5 to 1. It can use 87 octane because ot tuning and oil piston injectors cooling things off.

Honda is a fantastic engine manufactor and thats something we all can agree on.

 

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it doesnt release compression... the reason it leaves the intake valve open to compensate for pump lose when the TB butterfly closed during cruising. this helps the R18 be very efficient with fuel while the TB is closed. during pump loss compression is maintained not released and no inertia is lossed.

it has oil squirters "oil piston injectors/Jets" so it can run 10.5 compression pistons in this application not because of fuel porpoises directly. since the compression is still low its able to run 87 octane efficiently. the ignition and fuel delivery is tuned for this.

Technical Overview of Honda's new R18 i-VTEC Implementation

i think you read it wrong

From the link you gave me.

With the R18A SOHC i-VTEC mechanism, Honda's R&D engineers introduced the idea of controlling the amount of air entering the combustion chamber via other means instead of the throttle butterfly. This is done via a combination of both valve timing and an exploitation (ie it keeps the intake valve open longer. Honda.com has a nice video clip of this. very cool video) of the property of the 4-stroke cycle and a new Drive By Wire (DBW) system.

First, the intake valve closure timing is delayed to a very long period, way into the piston upstroke part of the cycle. The idea is to allow air to enter the cylinders freely, without using the throttle butterfly to artificially restrict air-flow. Then by opening the intake valves right through to the piston upstroke part of the cycle, the excess amount of air-fuel mixture that is in the cylinder will be expelled by the upward stroke of the pistons out through the intake valves and back into the intake manifold. When the amount of air-fuel mixture left remaining in the cylinder/combustion chamber is the desired amount, only then will the intake valves be closed. So instead of using the throttle butterly to control or limit the amount of air entering the engine, we allow the air to enter the cylinders and then push the unwanted amount out of the cylinders. So the exact amount of air we want is now controlled by the timing of the intake valve closure. In this way, the throttle valve/butterfly is not used/needed and it is allowed to remain wide open even under low-load conditions.


try Compression ratio - Wikipedia, the free encyclopedia to understand about dynamic and static compression
 

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I dont know if this has been said but the "i" in i-Vtec is a more intelligent form of the Vt part of Vtec. The difference is i-Vtec takes the Throttle load into consideration to adjust timing. Hope that helps.
 

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Excellent discourse, but I think we can all agree that while i-Vtec is different from what other manufacturers offer, it does not represent a paradigm shift. It's like how American English is different from British English, but it's not a different language, just a variant. Not the same, but not different enough for it to be in a different class.
 

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vtec = wow
others = whatevers

Ok...
vtec = wow

VVT (or whatever variable valve timing) + turbo = bye bye Si

It all comes down to torque and Hp. I dont really care how they get it. I would rather have a nice flat torque curve over a big RPM range than a burst of power at a certain rpm and above.

I like my civic. I didnt buy my civic for i-vtec, i bought it because it was a Honda.
 

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Excellent discourse, but I think we can all agree that while i-Vtec is different from what other manufacturers offer, it does not represent a paradigm shift. It's like how American English is different from British English, but it's not a different language, just a variant. Not the same, but not different enough for it to be in a different class.
are u kidding me? the ivtec in r18s and k20s are totally different and are there for different purposes.

r18 ivtec = economy/efficiency
k20 ivtec = performance

i.e. not the same AND different enough for it to be in a difference class.
 

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Ok...
vtec = wow

VVT (or whatever variable valve timing) + turbo = bye bye Si


It all comes down to torque and Hp. I dont really care how they get it. I would rather have a nice flat torque curve over a big RPM range than a burst of power at a certain rpm and above.

I like my civic. I didnt buy my civic for i-vtec, i bought it because it was a Honda.
vtec = wow

VVT (or whatever variable valve timing) + turbo = bye bye any car that is stock that is equivalent to the turbo car.

fixed it for ya:thumb:
 

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lots of false information on here. . . for starters theres alot of people here thinking VTC = VTEC. . . NO. . . VTC refers to systems like VVT, VVT-i, etc. . . VTEC is unique in the "EC", the Electronic lift Controller. . . VERY few systems function in this form

a little bit of history, Toyota came out with a VVT/VTC system first, I think it was called T-VIS. . . and from there they went into heavy VVT research and now havfe their Dual VVT-i to show for it, constantly variable valve timing on intake and exhaust valves independently. . . the first people to think and try research on a variable lift motor was GM, but their efforts proved futile and they canned the project, Hondas engineers picked up the project and in 1989 gave the world VTEC. . . their research went there and now theyve got things like the R18's i-VTEC SOHC, and their traditional DOHC i-VTECs. . . and soon enough VTEC Advanced

another little tidbit, up until 2000 TOyota didnt have a working idea of the variable lift system, then the came along with the 2ZZ-GE, their first. . . and only. . . venture into the variable lift stage, mechanically it was almost identical to VTEC. . . then later on the HOnda side the VTEC system gained it's "i". . . with the introduction of continuously variable valve timing along with the standard lift controller. . . Toyota gets the lift from Honda after its patents go out, and Honda gets continupusly variable timing when toyotas patent on it goes out. . . if it works well, and has proven itself, why not implement it yourself. . . and I will admit my brother's old Celica GT-S was awesome once that cam kicked over, but its not smooth like a Honda cam transition, which could present a problem in some circumstances

Toyota dropped out of the category in 2005 when the 2ZZ powerplant was canned due to its requirement of modification to pass euro spec emissions. . . Mitsubishi has MIVEC, and have had it for a good long while, its similar to VTEC, bit different enough that it didnt violate Hondas patents on the technology. . . and since, nissan is now running it as what they call Neo VVL on their SR20VE motor, Porsche is using it as they call it Variocam Plus. . . fact is, the technology is catching on, its more horsepower in less displacement, whats not to like

I thought 2ZZ was in the Lotus Elise
 

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im going to have say this over and over...

vtc changes the valve timing

vtec controlls higher lift on valves
Regarding i-VTEC,

VTC, or variable timing control, continuously controls intake valve timing by altering the intake camshaft phase angle which is its position relative to the crankshaft, with a total adjustment of +/- 25 degrees (advance or retard).

VTEC alters valve timing (thus duration) and lift, not just lift alone. However, it is not continuous throughout all RPM's.
 

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If you did research on future American Muscle cars, corvette for example, for the emmissions coming up. Most of those cars will be using their own Valve timing mechs to make more HP to help emmisions and better MPG.
 

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Been discussed. Honda is Unique as it was the first to come out with it! B16's OBD0 GSR motors.
Actually first production car with variable valve timing was
the nissan 300ZR on their G30DE engines.

however honda is more popular with it because they developed different
types of variable valve timing in both SOHC and DOHC
 
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