How The Vtec System Works

This may have been talked about before (sorry if it has). But I just wanted to shine some light on how it works.

VTEC in motorcycles

Apart from the Japanese market-only Honda CBR400F Super Four HYPER VTEC>, introduced in 1983, the first worldwide implementation of VTEC technology in a motorcycle occurred with the introduction of Honda's VFR800 sportbike in 2002. At low RPM, one of the two intake valves is only allowed to open a very small amount, increasing the fuel/air atomization in the cylinder and thus allowing a leaner mixture to be used. As the engine's speed increases, both valves are needed to supply sufficient mixture. A sliding pin, which is pressured by oil, as in the regular VTEC, is used to connect both valves together and allows the full opening of the second valve, and little extra power is produced but with a smoothing-out of the torque curve.

Here is a good video that shows how VTEC works. (hope video link works, I'm new at this)

Youtube


Hope this might help someone out.

God Bless,
Travis

Well thats for the automotive type of vtec, the motorcycle is much simpler, all it does is slide a pin in and out which stops or starts one of the valves from opening. The vtec in the auto has different profiles so you can get a different set of cam profiles when the pin slides in or out.

Well thats for the automotive type of vtec, the motorcycle is much simpler, all it does is slide a pin in and out which stops or starts one of the valves from opening. The vtec in the auto has different profiles so you can get a different set of cam profiles when the pin slides in or out.

Exactly......if you notice in the video, there are two modes. The first has the outer cam lobes actuating the valves, both of which are opening, with one having a smaller opening than the other. At higher rpm rates, the sliding pin locks both valves to the center lobe, which creates a larger, equal opening on both valves. This is the more complex system used in their cars.

The VFR V-TEC runs on one intake valve per cylinder, the other staying completely closed. Above a specified rpm, there is a sliding pin that actuates the second intake valve.

We only wish they use the Real VTEC on the VFR, not that it's a problem! :fing02:

I'll bet the new VFR (if it exists) will have cage-type VTEC, which would be okay except for the complexity of valve adjustments. Personally, I'd rather see direct injection and variable intake runner length.

I know the video in not "just like" the VTEC on the VFR, I was just trying to maybe shine some light on how it works, not everyone knows what VTEC does and how it works. That is why I listed a basic description on how it works. I was not trying to insult anyone. I was just trying to help out!

No one is insulted or pissed off. They just wanted to clarify the issue.

Also... Welcome to VFRD!

Here's how the VFR VTEC works. Inside the Honda VTEC

VTEC Tech

One of the 2002 Interceptor design team's goal was simple: make more power without changing the balanced character that made the Interceptor name legendary. Adding displacement to the 781cc V-4 engine would have upset the bike's balance of size and weight. Classic power enhancement approaches would have marred that balance as well. Instead, engineers chose a more elegant solution: Honda's VTEC valve train. Basically, VTEC gives the 2002 Interceptor engine the torque of a two-valve cylinder-head design at lower engine speeds, plus the high-rpm performance of a four-valve head.

VTEC History
Honda pioneered several systems to optimize valve timing across the rev range. Though it was never sold in America, the 1983 CBR400F REV used a two-valve/four-valve system, similar in principle, but differing in detail from the new Interceptor's.

VTEC Tech

Honda also uses VTEC systems on the Acura NSX sports coupe, Integra GS-R, Prelude, del Sol, Accord and Civic automobiles.

How VTEC Works
At engine speeds below 7000 rpm, the Interceptor's camshafts open only one intake and one exhaust valve per cylinder. Above 7000 rpm, cams open both intake valves and both exhaust valves for each cylinder.

Cams always act on one intake and one exhaust valve per cylinder. Diagonally opposed in the cylinder, these direct-actuation valves use shim-under-bucket valve actuation, allowing 16,000-mile maintenance intervals. The two remaining valves, which open after 7000 rpm, use shimless buckets. Camshaft lift, timing, duration and overlap remain constant at all engine speeds; only the number of valves in use varies.

Why VTEC Works
Maximum engine performance means keeping the fuel/air charge moving between 350 and 450 feet per second.

That's easy at high rpm, but at lower engine speeds, slower-moving pistons can't fill cylinders as efficiently. Here's where VTEC comes in.

By opening only one intake valve below 7000 rpm, fuel/air charge velocity stays high, accelerating through each cylinder's smaller single-valve opening. Beyond 7000 rpm, the speed of the piston dropping in its cylinder — and high vacuum — keeps mixture speed high with both intake valves open.

Plenty of details had to be worked out before the new engine was ready for production. Honda engineers optimized ignition timing and fuel-injection mapping to smooth the two-valve-to-four-valve transition. The Interceptor also features a solenoid-actuated dual-air-intake-duct design that keeps one duct closed during low-speed operation.

Like the two-valve/four-valve system in the engine, this one duct/two-duct system keeps intake velocity speed high as well.

This latest Interceptor engine showcases the kind of elegant engineering that has exemplified Honda's V-4 from the beginning: perfectly balanced performance without compromise.

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"Stucky" Sorry if I came across upset. Just want to help. I really enjoy this forum and have learned a lot, there is a lot of talented people on here. So, thanks for all your help.

"RRW" thanks for the VTEC info. As you could tell I need the help.


Travis

"Stucky" Sorry if I came across upset. Just want to help. I really enjoy this forum and have learned a lot, there is a lot of talented people on here. So, thanks for all your help.

"RRW" thanks for the VTEC info. As you could tell I need the help.


Travis

Not a problem. Remember, if no one is picking at you it means they don't like you. If you don't have a thick skin around this bunch of yo-yos, you better get some. LOL