No one knows for sure as the system is BRAND NEW and hasn't been around that long for the Evo. Time will tell but I DOUBT it will be an issue, mitsue has used Mivec for atleast 11 years, just new on the Evo.

 

there will never be an upper limit for mivec as it's not a limited or not type device. it will do what it does.

now the concern with building race cars, chances are you will not be using a mivec equipt car, because the added complexity in tuning and such may not be worth it. that said i believe aem and other standalones have provisions for controling vtech and other vvt systems so it's not gonna be any harder than that.

 

I think you misunderstood what I was saying. I was speaking of variable lift and duration, which the Evo IX's MiVEC does not have. Variable lift has little effect on helping power, even at lower RPM. Variable duration and cam-timing can both be used to help power, if not at peak, in the lower parts of the RPM band.

As we discussed before, it's theoretically possible to get as much peak power with cam gears as with MiVEC. But very few people tune their cam gears "perfectly" for power because, usually, doing so foks up the idle pretty badly. MiVEC allows you to have acceptable idle without sacrificing power up top. It's a good feature, although I think it will be some time before the tuning community as a whole accepts the full potential of MiVEC.

 

With the above being said, if you added a stroker to the MIVEC system, how much could you move the power band down & use the variable timing to assist in spooling up a larger than stock turbo?

Wouldn't this be the ideal set-up for a STREET not a race, but a street car? With the additional displacement & variable valve timing to assit in decreasing spool-time for the larger turbo.

If this set-up can kick in the turbo sooner it would allow for a larger powerband & still allow for the power not to drop off in the higher rpms.

Would it be possible for a set-up like this be able to reduce spool time by 700rpms vs a stock block 2.0?

I read in one of David's posts that his new 35R hits 20lbs of boost by 4100 on a stock 2.0 block & head:

https://www.evolutionm.net/forums/sh...&postcount=116

Using this as an example, IF the addition of a stroker and MIVEC could assist in spooling the turbo sooner (by 700rpms) you could have a powerband from 3400rpm to about 7500rpm. That would be close to if not better than stock!

I know Al from Dynoflash has tuned a car with this set-up & a 35R, but I haven't seen it compared to a Evo 8 with the same or similuar set-up.

Am I missing something or isn't something this ideal set-up?

 

see... you have the right idea. this with an exhaust cam retard and you could get a humungous turbo to spool faster.

 

This is exactly true. Except now, it can be tuned for peak power as well as all RPM points in between. Some cars will be receptive to MIVEC/AVCS changes in the higher RPM. Most have not shown much response as I've seen it.

Mitsubishi may as well have spit on everybody's mother. At least, that would be the reception we're seen on the MIVEC.

If a stroker kit necessitates an adjustment of your adjustible timing gears or your MIVEC, then simply retune them and your problem is solved. There is a good chance that, even untuned, it won't be detrimental to your performance. It is really hard to quantify the results, but the basic premise is that you will have a wider powerband with MIVEC/AVCS than you would sans MIVEC/AVCS. Just how much depends largely on the car.

-Jon

 

Camshafts Part III: Variable Valve Timing

Aug 27, 2004 | By: Abdul Rehman (UK)

There are a couple of ways by which car manufacturer's vary the valve timing. The most well known system is the VTEC which is used on some of the Honda engines. Other systems which some of you might not have heard of are:

• VarioCam/VarioCam Plus which is used on some of the Porsche engines,
• MIVEC(Mitsubishi Innovative Valve timing and lift Electronic Control) which is used on the Mitsubishi engines,
• VVT-i(Variable Valve Timing with Intelligence) and now VVTL-i (Variable Valve Timing and Lift with Intelligence) which is being used on the current Toyota and some Lexus engines,
• VVL(Variable Valve Lift) which is used on the Nissan engines and also featured in the 350Z is the CVTCS (Continuously Variable Valve Timing System)
• VANOS(Variable Onckenwellen Steuerung) which is used in the BMW engines and also the Double VANOS system on the new 3 Series and they are many more similar systems used by manufacturers such as Ford, Lamborghini and even Ferrari.

What do all these Vs have in common? Well, in case you don't already know (or haven't yet guessed despite the monster hint in the article's title), the V stands for valves or, more specifically, variable valve timing.

Before you can appreciate how important valve timing is, you have to understand how it relates to engine operation. Remember that an engine is basically a glorified air pump and, as such, the most effective way to increase horsepower and/or efficiency is to increase an engine's ability to process air. There are a number of ways to do this that range from altering the exhaust system to upgrading the fuel system to installing a less-restrictive air filter. Since an engine's valves play a major role in how air gets in and out of the combustion chamber, it makes sense to focus on them when looking to increase horsepower and efficiency.

This is exactly what Honda, Toyota and BMW and quite a number of other manufacturer's have done in recent years. By using advanced systems to alter the opening and closing of engine valves, they have created more powerful and clean burning engines that require less fuel and are relatively small in displacement.

Before we take a look at each of these variable valve-timing systems, let's rehash how valve timing normally works. Until recently, a manufacturer used one or more camshafts (plus some pushrods, lifters and rocker arms) to open and close an engine's valves. The camshaft/camshafts was turned by a timing chain that connected to the crankshaft. As engine rpm's rose and fell, the crankshaft and camshaft would turn faster or slower to keep valve timing relatively close to what was needed for engine operation.

Unfortunately, the dynamics of airflow through a combustion chamber change radically between 2,000 rpm and 6,000 rpm. Despite the manufacturer's best efforts, there was just no way to maximize valve timing for high and low rpm with a simple crankshaft-driven valve train. Instead, engineers had to develop a "compromise" system that would allow an engine to start and run when pulling out of the driveway but also allow for strong acceleration and highway cruising at 70+ mph. Obviously, they were successful. However, because of the "compromise" nature of standard valve train systems, few engines were ever in their "sweet zone," which resulted in wasted fuel and reduced performance.

Variable valve timing has changed all that. By coming up with a way to alter valve timing between high and low rpm's, Honda, Toyota and BMW and many more manufacturer's can now tune valve operation for optimum performance and efficiency throughout the entire rev range.

Honda was the first to offer what it called VTEC in its Acura-badged performance models like the Integra GS-R and NSX (it has since worked its way into the Prelude and even the lowly Civic). VTEC stands for Variable Valve Timing and Lift Electronic Control. It basically uses two sets of camshaft profiles-one for low and mid-range rpm and one for high rpm operation. An electronic switch shifts between the two profiles at a specific rpm to increase peak horsepower and improve torque. As a VTEC driver, you can both hear and feel the change when the VTEC "kicks in" at higher rpm levels to improve performance. While this system does not offer continuously variable valve timing, it can make the most of high rpm operation while still providing solid drivability at lower rpm levels. Honda is already working on a three-step VTEC system that will further improve performance and efficiency across the engine rpm range.

The camshaft in a pushrod engine is often driven by gears or a short chain. Gear-drives are generally less prone to breakage than belt drives, which are often found in overhead cam engines.

Toyota saw the success Honda was having with VTEC (from both a functional and marketing standpoint) but decided to go a different route. Instead of the on/off system that VTEC employs, Toyota decided it wanted a continuously variable system that would maximize valve timing throughout the rpm range. Dubbed VVTi for Variable Valve Timing with intelligence (Is this a dig at Honda, suggesting their system isn't intelligent?), Toyota uses a hydraulic rather than mechanical system to alter the intake cam's phasing. The main difference from VTEC is that VVTi maintains the same cam profile and alters only when the valves open and close in relation to engine speed. Also, this system works only on the intake valve while VTEC has two settings for the intake and the exhaust valves, which makes for a more dramatic gain in peak power than VVTi can claim.

Ferrari has a really neat way of doing this. The camshafts on some Ferrari engines are cut with a three-dimensional profile that varies along the length of the cam lobe. At one end of the cam lobe is the least aggressive cam profile, and at the other end is the most aggressive. The shape of the cam smoothly blends these two profiles together. A mechanism can slide the whole camshaft laterally so that the valve engages different parts of the cam. The shaft still spins just like a regular camshaft, but by gradually sliding the camshaft laterally as the engine speed and load increase, the valve timing can be optimized.

Several other manufacturers, including Ford, Lamborghini and Porsche have jumped on the cam phasing bandwagon because it is a relatively cheap method of increasing horsepower, torque and efficiency. BMW has also used a cam phasing system, called VANOS (Variable Onckenwellen Steuerung) for several years. Like the other manufacturers, this system only affected the intake cams. But, as of 1999, BMW is offering its Double VANOS system on the new 3 Series. As you might have guessed, Double VANOS manipulates both the intake and exhaust camshafts to provide efficient operation at all rpm's. This helps the new 328i, equipped with a 2.8-liter inline six, develop 193 peak horsepower and 206 pound-feet of torque. More impressive than the peak numbers, however, is the broad range of useable power that goes along with this system.

Several engine manufacturers are experimenting with systems that would allow infinite variability in valve timing. For example, imagine that each valve had a solenoid on it that could open and close the valve using computer control rather than relying on a camshaft. With this type of system, you would get maximum engine performance at every RPM. Something to look forward to in the future!

To close these series of articles on camshafts, you can see that as the benefits of variable valve timing used on cams become more apparent to both consumers and manufacturers, you can expect to see it on just about every vehicle sold in the world. I suspect that in five years, variable valve timing will be like ABS or side-impact beams: only really cheap cars won't have it.

E-mail this article
Top of page

 

What he said. I still think peak power is the same for both Evo VIII and IX using the SAME turbo.

 

The Turbo Charger and the engine work together as a system. Here is a link to

everything you need to know about Turbocharging! A very good read!

http://www.turbomustangs.com/turbotech/main.htm

 

I'm surprised there can be so many words in that article and yet it explains so very little. It basically says that companies have technologies.

-Jon

 

Jon - I too am coming from a Suby, as I had an STI. One of the things that was very apparant, was that a majority of the Suby tuners did not use the AVCS system to their advantage & most of them simply took it out.

I know part of the issue, was due to the lack of cams choices, which is changing, but I have not see any specific data to support that a properly tuned AVCS system is helping the 2.5 with lowering the powerband or decreasing spool time.

It could also be that with the amount of intercooler/piping needed for a FMIC on a suby, the lack of EMS systems available and the exhaust manifold design, could be hiding the affects on the suby motor.

It appears that with the 4g63, we may not have those same issues, as cams are arleady available and it appears that the EMS systems should be able to adapt fairly quickly.

 

Yeah why is it that Scoobys have no choice as far as cams? I mean you figure the aftermarket would JUMP on that.

 

They do now, as DPR, Cosworth & other now make AVCS cams. The thing with a suby, is that you have to pull the motor to replace the cams, which makes for a lot of work & changing four cams vs two for a 4g63.

Plus the aftermarket support was slow to respond. The STI has been around for what 3 years and the cams are just now coming out.

The MIVEC system has been out 6 months & cams are already available.....

 

Cams for the subys dont work very well due to the motor setup, it wouldnt gain as much power as we would on our motors

 

I have also heard that too, why is that?