VTEC...i-VTEC??

[El Sì]

Originally Posted by udumkid

Also, at moderate speeds the I-vtec advances the cam timing for increase valve over lap, creating an internal Exhaust Gas Recirculating(EGR) affect. At the same time, the lift of the intake valve is reduce to achieve a strong swirl effect in the combustion chamber the combine swirl effect an internal EGR effect provides for a highly efficient combustion process, which eliminates the EGR system.

Maybe this is where that difference in sound was coming from that they were talking about. But it wasn't from a cam switch at 3500. YouTube - How VTEC works here's a honda marine vid talking displaying vtec

[udumkid]

Originally Posted by El Sì

Maybe this is where that difference in sound was coming from that they were talking about. But it wasn't from a cam switch at 3500. YouTube - How VTEC works here's a honda marine vid talking displaying vtec

[mitsukaiSI]

ok think along with me . . . there are THREE LOBES per camshaft per cylendar . . . that equals SIX LOBES PER CYLENDAR (on DOHC obviously) so if there is PRIMARY lobe (TWO) and VTEC lobe (TWO) only that only equals FOUR lobes per cylendar . . . im telling you there is a primary secondary and vtec lobe

[lightlypurified]

go on the enclyclopedia and type in vtec it will tell u everything.

[Firestrife]

Jesus.
i-VTEC has variable Valve Timing.
There is just two camshaft lobes and one regular one performance and the computer can constantly adjust the timing of the intake valve.

[Jardiniboy]

Me and my friend say this for fun. He has the 2000 Si and I have the 2007 SI.

vtec =stupid vtec
I-vtec = smart vtec.

Haha

[BigT]

Originally Posted by mitsukaiSI

ok think along with me . . . there are THREE LOBES per camshaft per cylendar . . . that equals SIX LOBES PER CYLENDAR (on DOHC obviously) so if there is PRIMARY lobe (TWO) and VTEC lobe (TWO) only that only equals FOUR lobes per cylendar . . . im telling you there is a primary secondary and vtec lobe

^That is not correct.

By the way, on DOHC one cam operates the exhaust valves and one cam operates the intake valves (4 valves per cylinder).

There are three lobes per cylinder in the intake cam. The two non v-tec lobes are slightly different sizes and open the two intake valves slightly different amounts to create a swirl effect. But both of these lobes are being used at all times out of v-tec. One is being used for each valve.

Once the engine crosses over to v-tec the single, larger cam lobe in the center takes over and operates both intake valves. This lobe opens them farther than the non v-tec lobes as well as opening them the same amount. This cam is wider to account for the increased pressure because it is working both valves. There is only one v-tec switchover point. Only two profiles (not three).

That is why there are three lobes, but only one v-tec engagement point.

[Solo2EG]

Originally Posted by mitsukaiSI

yes there is . . . 0-3500 rpms is on primary lobe 3500 to 5800 is secondary lobe 5800 to redline is vtec lobe . . . have you ever messed with vtec cames befor? if you had you would know that

I just hate to see people who clearly have no idea what they're talking about spreading misinformation on these forums (seems to happen on a lot of threads around here) and as a matter of fact I'm only the crew chief for a team that runs two 8th gen touring cars in the Canadian Touring Car Championship as well as select Speed World Challenge races. I'm pretty sure I've had more K20's and K24's apart than you have!

And yes, on the small cam not all of the valve profiles are the same (some open earlier than others to promote a swirling effect for better combustion) but this is in no way a VTEC changeover to the big cam.

[mischief316]

Ok i'm no expert but how does VTEC or I-VTEC compare to the rest who try to be like it (or are like it)? Like how does it compare to the MIVEC? I know that Honda was the first to introduce this, but can it be better? I was reading up on the new EVO with the MIVEC engine and damn . . . 2.0L, turbocharge, 291 hp 300lb ft of tourque in that baby! This can be done with our k20 engine right?

PS: If the Mugen Si had that kind power . . . so worth it! Sorry if i went of topic.

[Firestrife]

First off everyone is missing the point about VTEC in general if i was you guys I would go read up on what VTEC is using the various links posted. Then come back and see what the main aim of VTEC was. it wasnt too produce massive amounts of power it was made to produce and maintain power but be able to be economical at the same time. Comparing to MIVEC and turbos and etc. is a different story with different aims in mind, and they are two completely different engines.

[Slow_si]

Good thread. I always thought (probably wrongly) that vtec was just another lobe that opened up.

[Civic4u]

VTEC (Variable Valve Timing and Lift Electronic Control) is a valvetrain system developed by Honda to improve the volumetric efficiency of a four-stroke internal combustion engine. This system uses two camshaft profiles and electronically selects between the profiles. This was the first system of its kind. Different types of variable valve timing and lift control systems have also been produced by other manufacturers (MIVEC from Mitsubishi, VVTL-i from Toyota, VarioCam Plus from Porsche, VVL from Nissan, etc). It was invented by Honda R&D engineer Ikuo Kajitani.[1] It can be said that VTEC, the original Honda variable valve control system, originated from REV (Revolution-modulated valve control) introduced on the CBR400 in 1983 known as HYPER VTEC.

In the regular four-stroke automobile engine, the intake and exhaust valves are actuated by lobes on a camshaft. The shape of the lobes determines the timing, lift and duration of each valve. Timing refers to an angle measurement of when a valve is opened or closed with respect to the piston position (TDC or BDC). Lift refers to how much the valve is opened. Duration refers to how long the valve is kept open. Due to the behavior of the working fluid (air and fuel mixture) before and after combustion, which have physical limitations on their flow, as well as their interaction with the ignition spark, the optimal valve timing, lift and duration settings under low RPM engine operations are very different from those under high RPM. Optimal low RPM valve timing, lift and duration settings would result in insufficient filling of the cylinder with fuel and air at high RPM, thus greatly limiting engine power output. Conversely, optimal high RPM valve timing, lift and duration settings would result in very rough low RPM operation and difficult idling. The ideal engine would have fully variable valve timing, lift and duration, in which the valves would always open at exactly the right point, lift high enough and stay open just the right amount of time for the engine speed in use.

VTEC was initially designed to increase the power output of an engine to 100 ps/liter or more while maintaining practicality for use in mass production vehicles. Some later variations of the system were designed solely to provide improvements in fuel efficiency, or increased power output as well as improved fuel efficiency.

In practice, a fully variable valve timing engine is difficult to design and implement.

The opposite approach to variable timing is to produce a camshaft which is better suited to high RPM operation. This approach means that the vehicle will run very poorly at low RPM (where most automobiles spend much of their time) and much better at high RPM. VTEC is the result of an effort to marry high RPM performance with low RPM stability.

Additionally, Japan has a tax on engine displacement, requiring Japanese auto manufacturers to make higher-performing engines with lower displacement. In cars such as the Toyota Supra and Nissan 300ZX, this was accomplished with a turbocharger. In the case of the Mazda RX-7 and RX-8, a rotary engine was used. VTEC serves as yet another method to derive very high specific output from lower displacement motors.

i-VTEC (intelligent-VTEC [4]) introduced continuously variable camshaft phasing on the intake cam of DOHC VTEC engines. The technology first appeared on Honda's K-series four cylinder engine family in 2001 (2002 in the U.S.). Valve lift and duration are still limited to distinct low- and high-RPM profiles, but the intake camshaft is now capable of advancing between 25 and 50 degrees (depending upon engine configuration) during operation. Phase changes are implemented by a computer controlled, oil driven adjustable cam gear. Phasing is determined by a combination of engine load and rpm, ranging from fully retarded at idle to maximum advance at full throttle and low rpm. The effect is further optimization of torque output, especially at low and midrange RPM.

For the K-Series motors there are two different types of i-VTEC systems implemented. The first is for the performance motors like in the RSX Type S or the TSX and the other is for economy motors found in the CR-V or Accord. The performance i-VTEC system is basically the same as the DOHC VTEC system of the B16A's, both intake and exhaust have 3 cam lobes per cylinder. However the valvetrain has the added benefit of roller rockers and continuously variable intake cam timing. The economy i-VTEC is more like the SOHC VTEC-E in that the intake cam has only two lobes, one very small and one larger, as well as no VTEC on the exhaust cam. The two types of motor are easily distinguishable by the factory rated power output: the performance motors make around 200 hp or more in stock form and the economy motors do not make much more than 160 hp from the factory.

In 2004, Honda introduced an i-VTEC V6 (an update of the venerable J-series), but in this case, i-VTEC had nothing to do with cam phasing. Instead, i-VTEC referred to Honda's cylinder deactivation technology which closes the valves on one bank of (3) cylinders during light load and low speed (below 80 mph) operation. The technology was originally introduced to the US on the Honda Odyssey minivan, and can now be found on the Honda Accord Hybrid and the 2006 Honda Pilot.

An additional version of i-VTEC was introduced on the 2006 Honda Civic's R-series four cylinder SOHC engines. This implementation uses the so-called "economy cams" on one of the two intake valves of each cylinder. The "economy cams" are designed to delay the closure of the intake valve they act upon, and are activated at low rpms and under light loads. When the "economy cams" are activated, one of the two intake valves in each cylinder closes well after the piston has started moving upwards in the compression stroke. That way, a part of the mixture that has entered the combustion chamber is forced out again, into the intake manifold. That way, the engine "emulates" a lower displacement than its actual one (its operation is also similar to an Atkinson cycle engine, with uneven compression and combustion strokes), which reduces fuel consumption and increases its efficiency. During the operation with the "economy cams", the (by-wire) throttle butterfly is kept fully open, in order to reduce pumping losses. According to Honda, this measure alone can reduce pumping losses by 16%. In higher rpms and under heavier loads, the engine switches back into its "normal cams", and it operates like a regular 4 stroke Otto cycle engine. This implementation of i-VTEC was initially introduced in the R18A1 engine found under the bonnet of the 8th generation Civic, with a displacement of 1.8 L and an output of 140PS. Recently, another variant was released, the 2.0 L R20A2 with an output of 150PS, which powers the EUDM version of the all-new CRV

With the continued introduction of vastly different i-VTEC systems, one may assume that the term is now a catch-all for creative valve control technologies from Honda.

Honda’s i-VTEC I Engine is a variant of the K-series DOHC engine family featuring gasoline direct injection. It made its debut in the previous generation 2004 Honda Stream 7-seater MPV in Japan, but the current Stream does not use this engine anymore, instead using a 2.0 liter version of the R-series i-VTEC SOHC engine.

The engine featured the ability to use ultra-lean air-fuel mixtures of about 65:1, much leaner compared to the usual direct injection engine 40:1 ratio, and of course so much more leaner than the stoichiometric air-fuel mixture of 14.7:1 - this saves fuel. Fuel consumption dropped to 15km per liter. Power ratings remain the same at about 155 horsepower.

[Civic4u]

I
I hope that help....:cheerleader :

[mischief316]

Originally Posted by Firestrife

First off everyone is missing the point about VTEC in general if i was you guys I would go read up on what VTEC is using the various links posted. Then come back and see what the main aim of VTEC was. it wasnt too produce massive amounts of power it was made to produce and maintain power but be able to be economical at the same time. Comparing to MIVEC and turbos and etc. is a different story with different aims in mind, and they are two completely different engines.

Yes i do understand that they are two different engines. And i guess i misunderstood that VTEC was meant only for power, now i know power and economical use is the main aim. But i just want to know how (in comparison) VTEC would be different than MIVEC. And can the VTEC k20 engine handle what a MIVEC engine (MB11 i believe). Just wondering.

[Tronixx]

This has nothing to do with anything, but I think the decal on the side of the Si looked better when it just said "DOHC VTEC" instead of the current "DOHC i-VTEC". VTEC is VTEC, even if the technology was upgraded they should have just left it the same name, too confusing, and I think the "i-VTEC" looks too gimmicky if you asked me. I just have a fonder memory of the side decal on the 99-00 Si's than I do with the current ones.

I've even thought about shaving off the "i" on the decal just to be different from everyone.

[oj88]

Here is probably the best explanation I've read. I hope it's accurate to a T.

From: Club RSX Message Board - View Single Post - v-tec vs i v-tec?

There have been SO many threads lately about vtec I'm starting to think that this is some sort of joke, but just in case it isn't and you are new to forums and unsure how to use the search feature I will repost this, enjoy
-Originally posted by honda tech user Targa250R-

The K20A3 does not have a standard DOHC VTEC valvetrain as we know it from the B-series engines - the K20A3 should actually be called a "DOHC i-VTEC-E" engine, because it uses a VTEC-E cam setup. The K20A2 is the "real" DOHC i-VTEC engine, utilizing the standard DOHC VTEC cam setup we're all familiar with. To help you understand the differences between the K20A2 and K20A3 engines, I've included the following information from a post I made elsewhere:

Allow me to evaluate. Let's start out by defining some terms:

VTEC - Variable valve Timing and lift Electronic Control. At low RPM, a VTEC engine uses a normal cam profile to retain a smooth idle, good fuel economy, and good low-end power delivery. The VTEC mechanism engages a high-lift, long-duration "race" cam profile at a set RPM value (i.e., ~5500RPM on the B16A) to increase high-end power delivery.

VTEC-E - Variable valve Timing and lift Electronic Control for Efficiency. This system isn't really VTEC as we know it. At low RPM, the VTEC-E mechanism effectively forces the engine to operate as a 12-valve engine - one of the intake valves does not open fully, thus decreasing fuel consumption. At a set RPM value (i.e., ~2500RPM in the D16Y5), the VTEC-E mechanism engages the 2nd intake valve, effectively resuming operation as a normal 16-valve engine. Note: in a VTEC-E engine, there are no high-RPM performance cam profiles; this engine is supposed to be tuned for fuel economy, right?

VTC - Variable Timing Control. This is a mechanism attached to the end of the intake camshaft only which acts as a continuously variable cam gear - it automatically adjusts the overlap between the intake and exhaust cams, effectively allowing the engine to have the most ideal amount of valve overlap in all RPM ranges. VTC is active at all RPMs.

i-VTEC - intelligent Variable valve Timing and lift Electronic Control. This is a combination of both the VTEC and the VTC technologies - in other words, i-VTEC = VTEC + VTC. Currently, the only engines that use the i-VTEC system are the DOHC K-series engines.

Now this is where things get tricky - Honda uses the term "DOHC i-VTEC" for two different systems: The first system is used in the K20A2 engine of the RSX Type-S. The second system is used in the K20A3 engine of the Civic Si.

The First System (K20A2):

This system is pretty close to the older DOHC VTEC engines. At low RPM, the K20A2 uses a normal cam profile to retain a smooth idle, good fuel economy, and good low-end power delivery. At 5800RPM, its VTEC mechanism engages a high-lift, long-duration "race" cam profile to increase high-end power delivery. The only difference between this i-VTEC engine and the older VTEC engines is the addition of the VTC system. The intake camshaft has the automatic self-adjusting cam gear which continuously optimizes valve overlap for all RPM ranges.

Here we see an image of the intake cam lobes of the K20A2. Notice there are 3 lobes; the two side lobes are the low-RPM profiles, and the center lobe is the high-lift, long-duration profile which engages at 5800RPM. Basically the same setup as the old VTEC engines we are familiar with.

Now here we see the VTC mechanism - the gear on the end of the intake cam that adjusts valve timing (overlap) automatically on the fly.

This system is used in engines powering the JDM Honda Integra Type-R, Civic Type-R, Accord Euro-R, and the USDM Acura RSX Type-S and TSX.

The Second System (K20A3):

This system does not really conform to the "DOHC i-VTEC" nomenclature, as Honda would like us to believe. As I mentioned in my previous post, it actually should be called "i-VTEC-E," because it uses a VTEC-E mechanism rather than a standard VTEC mechanism. At low RPM, the VTEC-E system effectively forces the engine to operate as a 12-valve engine - one of the intake valves does not open fully, thus decreasing fuel consumption. At 2200RPM, the VTEC-E system engages the 2nd intake valve, effectively resuming operation as a normal 16-valve engine. There are no high-RPM performance cam profiles; this engine is tuned to balance fuel economy and power, rather than provide pure performance. On the intake cam, there is the VTC mechanism which basically is an automatic self-adjusting cam gear used to continuously optimize the valve overlap for all RPM ranges. This being a VTEC-E system - and not a true DOHC VTEC system - is the reason the K20A3 redlines at a measly 6800RPM, while the K20A2 is able to rev all the way to 7900RPM.

Here we see an image of the intake cam lobes of the K20A3. Notice there are only 2 lobes - there is a nearly round one used only for the low-RPM disabled intake valve, and then there is the regular lobe used by the other valve at low-RPM and by both valves at high-RPM:

This system is used in engines powering the USDM Acura RSX base, Honda Civic Si, Accord 4-cylinder, CRV, and Element.

Special note: The K20A3 engine used in the Acura RSX base has a slightly different intake manifold design from the K20A3 engine used in the Civic Si. The RSX engine uses a dual-stage manifold, similar in concept to the manifold of the B18C1 in the old Integra GSR. It uses long intake runners at low-RPM to retain low end power, and switches at 4700RPM to a set of shorter intake runners to enhance high-end torque. This accounts for the extra 9 ft-lb of torque in the RSX (141 ft-lb, vs. 132 ft-lb in the Civic Si).

Here is an image showing just how this dual-stage manifold works. On the top, you can see the low-RPM (long) runners are in use, and on the bottom, you can see the high-RPM (short) runners in use.

Myths:

1. The i-VTEC engine engages VTEC gradually, and not suddenly like in the old VTEC engines.

Wrong. The i-VTEC engine "engages VTEC" at a single set RPM, like always. Whoever started this rumor is a fucktard. Read the definitions above.

2. VTC engages at a set RPM.

Wrong. VTC is always activated. Read under "VTC" above.

3. The K20A3 engages VTEC at 5000+ RPM.

Wrong. Technically, there is no "VTEC" (as we think of it) in the K20A3 engine - it uses a VTEC-E technology, which engages at 2200RPM. Read under "The Second Sytem" above.

[Firestrife]

Originally Posted by mischief316

Yes i do understand that they are two different engines. And i guess i misunderstood that VTEC was meant only for power, now i know power and economical use is the main aim. But i just want to know how (in comparison) VTEC would be different than MIVEC. And can the VTEC k20 engine handle what a MIVEC engine (MB11 i believe). Just wondering.

Well VTEC has nothing to do with what the engine can and cannot handle that would fall under what the block, piston, and etc. are made out of, what compression ratio your gonna run, the tuning system. Now that is what determines what the engine can handle in terms of comparing it to the Mitsubishi (evo engines i believe your comparing it too).

Which brings me back to why your not understanding what VTEC is or boost for that matter. I'm not trying to sound like a jerk but im just telling ya read up on it and it will all come clear.

[mitsukaiSI]

Originally Posted by BigT

^

By the way, on DOHC one cam operates the exhaust valves and one cam operates the intake valves (4 valves per cylinder). And I believe the system in the Si only has v-tec on the intake cam.

\.

vtec only on the intake came is for the ep3 thats a large part of why it sucked so much ass i dont think our vtec is only on intake cam

[Leonard1818]

If they're asking "which is better", you don't need to know the exact science of each system... just use a little logic.

Which is newer technology? Honda wouldnt "downgrade" to i-VTEC from standard VTEC...

[Mitch]

Originally Posted by oj88

Here is probably the best explanation I've read. I hope it's accurate to a T.

From: Club RSX Message Board - View Single Post - v-tec vs i v-tec?

That information is correct, but outdated. When that document refers to "The Civic Si" it is referring to the EP3. The k20z3 is not the same motor as the k20a3, and I think that may cause some confusion. The k20z3 is an evolution of the k20z1 found in the updated RSX-S. It makes less power due to emissions controls and the updated balancing shaft configuration which improved smoothness. It is a common misconception that the k20z3 is an evolution of the previous generation Si's k20a3 which had v-tec intake cam but non-v-tec exhaust cam.

For reference: K20Z3 2006 Civic Si
Notice the that both cams have three lobes per cylinder.