Techline-May09-H-D 110" CVO -Part V: Lean running motors/overcooked cylinders (cont.)

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This article concludes in the next thread.

Cylinder Design
Here are my recommendations for a redesign of the CVO 110 cylinders:
As I have written, the spiny lock construction in the CVO 110 cylinders only go to within 0.625" of the top cylinder deck. This allows heat expansion and contraction to disrupt the head gasket surface, which must be perfectly flat to function correctly. This should be changed to a minimum of 0.094" (3/8") from the cylinder deck top, as in TC 88 cylinder construction. I believe this will prevent the cylinder liner separation.

The TC 88, TC 95, TC 96, TC 103, and TC 110 all use the same cylinder stud pattern, with the same distance between each. Big-inch engines that must cope with closed-loop stoichiometric ratios should go to an equidistant five-stud system to replace the four-stud cylinders in use since 1984. S&S Cycle has done this with its innovative

X-Wedge engine, which meets emissions standards up to and including the
stringent 2010 dictates.

Finally, moving the cylinder studs out farther into the middle of the gasket surface will assist in the even and consistent application of gasket pressure. This will equalize torque pressure specifications and add the extra support needed to cope with higher engine temperatures. The 2007-08 CVO 110s still use the Twin Cam 88 cylinder studs (#16834-99A), which have been in use since 2003 when they replaced the 1999-2002 (#16834-99) cylinder studs. On Chris’ bike, I replaced the stock studs with higher tensile strength ones, like those provided by S&S (#31-2340).

As stated last month, there is a 0.028" gap between the cylinder spigot hole and the cylinder flange, which is the extension of the cylinder liner that protrudes from the base of the cylinder into the spigot hole. This extension is necessary to provide support for the piston skirt fore and aft thrust surfaces, particularly as the piston changes axis at bottom dead center. The piston must suddenly stop and change direction guided by the cylinder flange. The outer side of the flange, if it’s a plug fit in the crankcase spigot hole, will also provide some rigidity and support to the whole structure. The aluminum engine cases expand more and faster than the cast-iron cylinder liner, so a plug fit will not cause a conflict with the expansion and contraction of mating parts. It’s an easy manufacturing procedure to tighten cylinder specifications for a plug fit into the engine cases.

Make the cylinder CVO cylinder liner thicker if it makes people feel better. Extra rigidity has always assisted and never hurt an engine’s functionality. Use the same cast-iron alloy in the CVO 110 sleeve used in the TC 88.
The CVO 110" cylinder fin area is less than that of the TC 88. As a minimum requirement, restore the cooling fin area to match that of the TC 88, including the cylinder head. Preferably, the redesign would extend the fins even more.

I have already mentioned using an alloy more resistant to extreme heat than is currently utilized to resist warping. The machining of the head gasket surface needs to be addressed by quality control, especially if MLS gaskets, which require a roughness average of about 50, are used.

Oil & Air Cooling
The premium Harley-Davidson eight-core turbulated oil cooler is one of the best on the market. However, it is not enough in my opinion. In this case, more is better as long as oil restriction through the cooler is balanced. I feel a 14-core oil cooler or dual 10-core oil coolers placed into the wind will be a necessary assist in combating heat.

The oil reservoir capacity should be increased. BAKER Drivetrain leads the way on this one with its Plus One oil reservoir. I feel Harley-Davidson should duplicate this feature as a standard item on all models that must meet the EPA-mandated stoichiometric ratio. This excludes the V-Rod and the new 1125R Buell because they already cope wonderfully with excess heat due to their liquid-cooling and cylinder angle reconfigurations. Sorry to be the bearer of bad news for traditionalists like myself, but these bikes are the future of Harley-Davidson.

Fossil oil should become an oil of the past for air-cooled engines coping with EPA restrictions. The superior lubricity of synthetic oil should become the mainstay of these engines. Synthetic oil withstands much higher temperatures than fossil oil before beginning to break down because of heat-induced oxidation.

Unless there is a radical redesign of the engines, I feel a rear cylinder fan, which is now only an option, should become standard equipment.

Lean Mixtures
As I have said before, H-D has a real conundrum here. It cannot meet EPA mandates and lower the closed-loop air/fuel ratio at the same time. The factory can only resolve this issue by adapting existing water-cooling and other similar, distasteful technologies that destroy what the traditionalists love. Preferably, the Motor Company can do the redesigns mentioned, in addition to exploring new technologies that will ably cope with the heating issues that are not going away.

For us, the consumers, our options are more flexible. Our solution is to lower temperatures by lowering the air/fuel ratios below 14.7:1 during hot idle and cruising situations. The SERT (Screamin’ Eagle Race Tuner) can lower air/fuel ratios to approximately 14.2:1, which is adequate, but the Power Commander can take the air/fuel ratio down even lower if necessary. Both the SERT and PC require skilled technicians to tune them. The Terminal Velocity is self-tuning. After installation, it does all the tuning work and constantly changes tuning according to information received from the O2 sensor(s). There is some controversy over the stock, narrow band O2 sensors. I, too, have fallen victim to this, but no more.

Narrow band O2 sensors do not need replacement with wide band O2 sensors except in specific applications where response time is critical. Therefore, the stock narrow band sensors are adequate for most performance work. Supercharged or turbocharged engines need wide band O2 sensors when using higher boost. Conditions can change so fast that a narrow band sensor might not be able to react in time to counter ultra-lean circumstances. All of the above ignitions and many more in the marketplace adapt to performance changes. They are not a one-time install for specific changes like the Screamin’ Eagle burns (downloads). These become obsolete as soon as any performance parts are changed.
There are two main types of fuel/ignition modifiers with many varieties within each. Input modifiers are located between the O2 sensor(s) and the ECM. Terminal Velocity and SERT are two examples of devices that modify the information going from the O2 sensors to the ECM, which changes the air/fuel ratios dictated by the ECM. Output fuel modifiers go between the ECM and the EFI system. O2 sensor information to the ECM is unchanged by these devices.

The fuel directives from the ECM to the EFI system modify the air/fuel ratio by increasing the fuel injectors’ pulse width, which is how long they stay open. Therefore, the air/fuel ratio lowers (richens) because the output modifier lengthens the injector’s pulse width. Output modifiers can be limiting because all except the Power Commander can change only fuel, not the ignition table. This is not necessarily a putdown, since fuel modification is the primary change we are after in this particular situation. The Power Commander is special in that it has an ignition component. The result of fuel modification will be a head gasket that retains its integrity and is able to do its job.

The air/fuel ratio reaching above the ideal stoichiometric ratio is the true problem. We can lower temperatures after the fact with assists such as EITMS, cylinder-cooling fans, synthetic oil, larger-capacity oil tanks, and dual 10-core oil coolers. However, the cure will revolve around two things: using components that can withstand and function within higher operating temperatures, and lower engine temperatures. If we can keep the rear cylinder at 14.7:1, we can probably obey closed-loop emissions standards. Lowering temperatures will give increased engine longevity along with performance improvements.

Other Options
An obvious way through part of this debacle would be to lower the compression in the CVO 110, as this would lower cylinder pressure. In physics, pressure and heat are synonymous. Expanding heat from burning air and fuel is what drives the piston downward on its power stroke.

Increasing pressure during the compression stroke, via an upward-moving piston, creates heat. If this heat gets too severe, preignition and devastating detonation will occur. So, why should the factory not lower compression? The raison d’être of a 110" Harley-Davidson is power. We don’t want to decrease power by lowering compression, now do we?
There is another way: the stock CVO 110 .550"-lift cams have durations of 211 degrees on the intake and 235 degrees on the exhaust. The S&S .585G gear-drive cams that I used in Chris’ CVO 110 have a higher lift of .585", which I increased to .603" via a longer roller rocker arm ratio. The duration figures for these cams are 245 degrees on the intake and 260 degrees on the exhaust. This is not a radical departure as the stock CVO cams have some emissions controls built in by decreasing cam duration.

Increasing duration allows for higher compression. This is because compression does not start to build until later in the compression stroke because the valves are open longer at the beginning of the upward stroke.
Porting and polishing the CVO 110 will also help. The heads (front #17250-07, rear #17248-07) have big, expanding intake ports similar to a Shovelhead to accommodate bigger intake valves. The valve seats are thinner in depth and width, as the accompanying chart shows.

Another cure that I explored with Chris’ CVO 110 is getting rid of the problematic stock cylinders and replacing them with aftermarket ones. I chose a cylinder set with pistons (#200-215S) from Axtell Sales of Des Moines, Iowa. There is one wrinkle for this particular application. The Axtell cylinders and reverse dome pistons are for use with an 85cc combustion chamber. The CVO 110 combustion chamber is 95cc. Axtell is on top of its game and substituted flattop pistons for the reverse dome ones usually sent with the kit, which give Chris a 9.65:1 compression ratio.

This article concludes in the next thread. Check back issue for pix and extra information.