Q: At IPS you talk about engineering superiority over the aftermarket and use a bunch of fancy terminology like harmonics and resonance when describing your product. I say bull; it’s just a bunch of fancy talk and hype. Isn’t cam design very simple? Engineers don’t need to design this stuff.

A: We are not about obscuring how our product works with fancy talk and science. IPS designs around well understood and documented natural phenomena that has been observed and taught for generations. A second year engineering student studies these phenomena in school.

One of the many problems that plague the high performance aftermarket is that there is often a lack of true engineering on the products. It’s not just camshafts but many different components as well. The high performance industry is full of smart self-taught tuners who have brains and a bunch of good common sense.

Many times it is possible to build a superior product for high performance use without an engineer’s training because stock OEM parts are often designed with many design compromises. Compromises such as lowering cost, the need to provide satisfaction for a non-performance oriented customer, meeting emissions, good fuel economy, providing six-sigma reliability for the duration of the warranty period weigh strongly in the development of OEM parts.

If cost is disregarded and the part's design intent is altered to eliminate pleasing the everyday driver, et al, it is quite possible for an intelligent non-engineer to build something that functions better in the narrow focus of the high performance world. It happens all the time. Unfortunately cam design is not one of these areas.

Q: I thought that you eliminate valve float by just upping the valve spring pressure by using a high rate spring and the only real issue with this is finding a high rate spring that won’t coil bind. What causes valve float?

A: In the OEM arena, cam design is a very complex and engineering intensive field. Things like reducing "valve float" by increasing spring pressure and eliminating "bind" seems like the intuitive thing to do and it does work, but it's often not the most effective way to reduce float and gain rpm.

The main cause of valve float is a phenomenon called spring surge, which is caused by harmonics, typically 5th order harmonics in a production-based engine. Surge happens when the reciprocating action of the valvetrain reaches a critical cyclic speed where the valvetrain’s natural frequency is reached or in the case of a valve spring, the 5th harmonic of the spring’s natural frequency is reached. This usually happens on a modified engine running at higher than stock rpm.

The spring’s natural frequency is a point in a spring’s cyclical operational range where the compressing and extending motion of the spring propagates a "wave" in the spring because the cyclic rate matches the spring’s ability to move. The forces build up to the point where the spring surges and loses contact with the valve and retainer!

If you look at high speed stroboscopic films of this phenomena taken with a spintron (valvetrain testing device), you can see the standing wave build up in the spring, like a slinky, then the spring "compresses" as the harmonic is reached and the surge forces multiply. When this happens the spring is actually floating in mid air and not even contacting the retainer anymore. This is when valve float occurs.

When designing a cam and engineering it to OEM levels, the natural frequency of the spring must be considered as well as the natural frequency and mass distribution of all valvetrain components. The instantaneous velocity of all moving parts needs to be determined and everything integrated to calculate the critical periods of the spring/valvetrain system. Usually the 5th order harmonic is dangerous because the lower order harmonics occur at lower rpm where there is not as much cyclic energy imparted on the system and the springs tension can handle the surge.

Q: What is IPS doing to prevent valve float that’s different from other aftermartket cam designers?

A: The most powerful tool in preventing valve float is to reduce the effects of spring surge. To avoid surge either the natural frequency of the valvetrain can be altered and/or the cam profile can be manipulated to accelerate the valve in a way to reduce the excitation energy of the system to a point where the spring’s tension can handle it.

The mass of the valvetrain or the spring’s natural frequency can also be altered and move the 5th order harmonic to a harmless RPM, like an RPM higher than the engine will rev. This is how high buck race teams like the ones in top levels of auto and motorcycle racing engineer cams. It’s also how OEM's with scores of real degreed engineers do it.

This sort of engineering is a much more elegant solution than the brute force and seemingly common sense method of simply upping spring tension until the float stops. High valve spring tension creates more frictional losses and greatly increases valvetrain wear. The trick is to minimize the spring tension needed to do the job.

IPS cams are also engineered to use commonly available, high quality and inexpensive off the shelf stock Honda valve springs. Custom valve springs can prove to be problematic for reliability and expense.

Q: Ok so you guys did a good job at eliminating valve float. How do you produce more power and a wider powerband than the other guys? Aren’t the only things in a cam that’s important for performance lift and duration? Your lift and duration doesn’t seem that much different from your competitors. What makes you better?

A: IPS cams are designed to have the maximum area under the lift curve within the constraints of the recommended springs. Area under the lift curve is the open dwell time and lift height of the valve when plotted against degrees of crankshaft rotation. This is more significant for power production than simple raw lift and duration data. If two cams have identical lift and duration figures, the one with more area under the curve will make more power and torque. It can also make more power with a wider powerband than a cam with more duration and lift with less area under the curve.

IPS cams also have been painstakingly dyno tested to find the optimal lobe centers and lobe separation angle. Headers, intake manifold and air intake design all affect these cam specs and IPS cams have been ground with the lobe centers and lobe separation angle that will work well with these components. For the most part, IPS-K2's will be close right out of the box. For your typical motor with the basic bolt-ons already installed, you won't need lots of expensive dyno time to dial in your cams. If you want to extract every bit of power from your combination, the addition of an adjustable exhaust cam gear and dyno time will probably produce some gains but smaller ones than typically experienced with other cams.

Q: I say bull to your area under the lift curve and fastest possible opening and closing velocity talk. I looked at your cams and you can tell that your lobes are not as aggressive as other cams by their shape.

A: You can't easily eyeball cams and "tell" which one has higher acceleration. A steeper looking ramp doesn’t mean greater valve acceleration. A “mild looking” cam with a skinny pointy lobe has higher accelerations over the nose which is bad for creating harmonics and increasing excitation energy. This “mild” shape increases wear inducing point loads versus a lobe that looks wide and "aggressive". This seems counter intuitive but when you actually plot the profile over degrees of crank rotation you can see what’s going on.

Q: What is so good about your quality? I can copy your lift and duration and have my stock cams reground for less money. Why are your billets better than others and why can you say yours are less likely to break?

A: As we stated previously, there is much more to cam design than lift and duration. If you want to try, well you are on your own. There are many subtleties with the profile and type of grinding we use. Regrinds don’t work well on rocker arm motors like the K series. By grinding on the cams base circle to get more lift and duration from a stock lobe, you really upset the rocker arm geometry which wrecks havoc with the cam spec numbers as well as potentially creating a lot of noise and wear issues. You get what you pay for.

IPS cams are ground on new half chilled iron billets. As far as we know, other quality K-series cams on the market are ground on fully chilled billets. A chill is a metal heat sink placed in the sand mold that the billets are made in. The chill speeds the hardening of the molten iron and imparts metallurgical changes that make the iron harder and wear resistant right where it needs it most, on the surface of lobe. In between the lobes cools slower and stays tough and ductile resisting breaking. Normally this is a great thing. Unfortunately on a VTEC engine there are so many lobes that the whole cam becomes over chilled and brittle. A fully chilled billet will break easily.

Other manufacturers don’t bother with chills; it’s much easier and cheaper to make a billet this way. The billet is break resistant, the lobes are much easier and cheaper to grind but the cam will wear much faster.

We use half chilled billets. This is where a small chill is placed right on the top of the lobe in the mold. That way the base circle of the lobe stays soft and the opening and closing side of the lobe gets hard. The wear resistance is where it’s needed yet the cam still resists breaking. A half chilled lobe is still difficult and time consuming to grind but it produces a cam with the best features of both worlds. To our knowledge we are the only K-series cam makers that use half chilled billets.

Our cams are ground on precision CNC cam grinding machines. We also use small diameter grinding wheels. This is much more expensive than normal because a small wheel removes material slower and must be dressed more frequently. A small wheel is necessary to create the reverse flank that roller cams need and to create the subtleties in our lobe profile. Typically other cam makers use larger wheels to cut grinding time and costs and cannot produce a reverse flank.

To reduce wear and friction and to speed break in, our lobes and journals are micropolished after grinding. Most cam makers parkerize their cams, but we have found that micropolishing actually works better. Your factory Honda cams are micropolished for a reason and we wanted to duplicate that.

Q: I was comparing published specs of various cams, both OEM and aftermarket: What is the difference between specs taken "at the valve" vs. "at the lobe?"

A: For complex valvetrains such as this which use a non-linear rocker arm ratio, there are several different methods to compare cams. One method is "at the lobe" with the cam spinning on v-blocks. These results can vary depending on what follower diameter was used for the test. So you can only compare tests which used the same follower diameter, i.e. .750". A lot of cam companies use this diameter for checking because that probe size is the same as a roller follower on an American V8 engine.

You could check the cam on v-blocks with the same follower diameter that is used in the K20A engine which is 1.122". If you did this, you would get different .050" durations and the same cam lift as measured with a .750" diameter follower. Furthermore, if you measured one of these cams with a 1.122" diameter follower and then multiplied that entire lift curve by 1.75, you wouldn't get the same lift curve that you would measure at the valve because the rocker arm ratio isn't constant through the entire valve motion. It would only be the same at full lift. To summarize, specs taken "at the lobe" using a .750" diameter follower is in effect 2 steps removed from reality.

The second method for comparing cams with this type of valvetrain is "at the valve". We compare cams "at the valve" because this is what the air flow works with and what the engine sees. When you are working with valve motion data, you can make more intelligent choices about manifolds, for instance, because you are talking about the durations that the engine is really seeing.

Specs taken "at the lobe" is only valid for getting "a difference" between 6 different cams sitting on a work bench (for example), but it is not valid for saying what "the difference" is at the valve.

Q: I see that rocker arm ratio is sometimes listed along with cam specs "taken at the lobe." One spec that I've seen, lists rocker arm ratio as 1.75:1 on the high speed lobes and 1.70:1 on the low speed lobes. I don't understand how the rocker arm ratio can be different between high speed lobe and low speed lobe? How can they be different rocker arm ratios if both rocker arms pivot on the same shaft, and must engage the valve (which is also fixed) at the same point?

A: Look at the rocker arm!!!! ... The rocker arm ratio is the same from the low speed to the high speed lobes as there are no differences in any of the lengths that determine the rocker arm ratio between the low and high speed lobes for a given side.

Q: Okay I get it now. What are the OEM cam specs taken "at the valve?"

A: This is a chart showing RSX-S (02-04) vs K20A (ITR). We've thrown in TSX for good measure.

Q: Here's a tough one. How do IPS-K2's compare against the competition, spec for spec -
    "at the valve?"

A: Here you go:

Q: Thanks for giving me all the specs, now I can go out and make my own!

A: Publishing accurate specs does present somewhat of a risk, however those are just the boundaries of the box. There's more to improving VE through camshaft profile design than just grinding cams with numbers from an excel spreadsheet.

Q: Really? What else would I need to copy your cams?

A: Well, we can't prevent unscrupulous individuals that may get their hands on a set. A camshaft is a simple mechanical device that is ineligible for a patent. It may be possible to patent the design process, but not the actual cam itself.

Q: Alright, I was just kidding. I'm genuinely interested in what makes your cams work. What can you tell us?

A: Successful cam profile design has an intrinsic relationship with the spring that controls valve motion. Here are some parameters from the battery of tests and calculations involved:

• analyze round and elliptical wire spring scenario
• perform harmonic analysis predicting when the cam profile will cause spring surge
• predict the rpms at which the springs will surge and valves will float
• find the minimum gap between the provided and required spring force curves
• determine the spring's installed height to get maximum rpms
• predict excessive cam/lifter wear from spring forces
• determine wire stresses, natural frequencies, harmonic numbers
• force vs. height for each spring
• force vs. distance compressed with all springs of set provided vs. required spring force around the cam lobe
• cam lift, velocity, acceleration and jerk
• lift, acceleration and jerk harmonics
• wire stress for each spring as the cam rotates
• Hertz contact stress at the cam/lifter interface
• cam lobe radius of curvature

Q: I have looked at the advertised specs for the other aftermarket cams that are of the same class, or target market. IPS-K2 has the highest numbers for High-Cam Intake and Exhaust duration and Intake lift, but it has the lowest Exhaust lift of the three after market cams. Looks like maybe the K2s gave up some Exhaust lift in order to maximize the other numbers while retaining VTC. The brand-X and brand-Y run different profiles on the two Low-Cam lobes, yet IPS-K2's keep the Low lumps the same for each valve. I wonder why the different approaches? Also, looking at brand-Y specs... IPS-K2 is similar, but they require valve springs and you don't. Isn't that just marketing hype for IPS-K2's? So why does brand-Y require upgraded valve springs ?

A: You're very observant. Our engineers have determined that the variance between low speed lobes contributes to swirl and emissions. For all out performance, our testing has shown that these lobes should not vary. The low speed lobes are optimized for low-midrange torque and performance. We're not the only ones that advocate the equal low-speed lobe approach. The TSX, which is a 2.4L factory torque monster (relatively speaking) is the same way right from the Honda factory!

There is an optimal Intake to Exhaust lobe ratio that makes best power with the K-series engine. This holds true for previous Honda engine families as well.

IPS-K2's do require upgraded valve train, but we've identified an OEM combo that performs well for the given application. Having valvetrain that supports 10K+ rpm is only warranted in full-race applications. So for max safe, street rpm levels - one application is specifically engineered and the other isn't. It has to be correct to run an application within a given set of parameters. Thus, the converse is true - you remove those parameters and the application does not have to be correct.

Q: I have read that if lift and duration are similar between IPS-K2's and other aftermarket cams, it seems that retainers don't matter. Is this true?

A: Retainer design, and mass, is especially crucial in that they are one mechanism by which installed height is determined. It is also a factor in calculating maximum safe rpm for a given application. Its dimensions greatly influences the effective valve spring force, open and closed. Furthermore, understating these seemingly simple constructs will get you nowhere closer to the truth. The seat duration or advertised duration numbers are usually what you get at the hot valve lash point so that would be at .014" gross valve lift with our cams. Advertising the duration at the hot lash point and the valve lift with zero lash is really the boundary of the box. We are honest about what that seat duration is but other companies will inflate or deflate the actual number to confuse the competition. For this reason, if you see two different companies with very similar seat durations for their cams, they mignt be the same thing or maybe not. In any event, you still have no idea from the advertised numbers what the aggressiveness or the design technique of the cams are. What this means is that cams with similar advertised specs could work to very different maximum rpms.

Q: What is the maximum VTC intake cam advance we can run with IPS-K2's? Are there any interference issues to be aware of in a stock K20A(2)?

A: There is no valve-valve, or piston-valve interference with IPS-K2's installed in a stock K20A(2).

Intake Valve to Piston Clearance:

• 30 degrees - .190"
• 40 degrees - .098"
• 50 degrees - .045"