 Techline-May09-H-D 110" CVO -Part V: Lean running motors and overcooked cylinders
This article continues in the next thread.
This month we continue with an excerpt from Chapter 3: H-D 110" CVO from Donny’s Unauthorized Technical Guide to Harley-Davidson 1936 to Present, Volume II. (Some content has been altered to fit AIM’s style and format.)
My intention is not to demean Harley-Davidson’s and the aftermarket’s assist with the high-heat situations that we now face because of closed-loop EFIs (Electronic Fuel Injection) that seek stoichiometric air/fuel ratios. The new gaskets and upgraded parts are all necessary and welcome additions to the fight against extreme heat. However, they are not cures in themselves because the cause of the extreme heat fails to be addressed. We have already discussed parade-duty, open-loop EFI mode to combat hot-idle conditions. However, it bears repeating that the engine needs air cooling, so idling is not a good option with the new EPA demands. Ride your bike immediately and conservatively in the wind until warmed up.
The Engine Management System
Harley-Davidson has made huge strides with its engine management system, both to modernize its engines and to meet increasingly strict EPA demands. The progressively changing and improving Delphi EFI is light years ahead of the inefficient and slow Magneti-Marelli EFI systems used on the first Twin Cams. Fuel efficiency is at an all-time high with emissions at an all-time low. The ESPFI has followed the increased sophistication incorporated in the experimental 2006 Dynas, which works extremely well given its mandate and conditions of operation. The 2006 Dyna introduced the use of a new feature, an O2 sensor that makes closed-loop EFI a reality. This O2 feedback sensor is located out of the way, behind each header exhaust pipe. The sensor measures exhaust gas composition and sends signals back to the electronic control module, which signals the EFI to adjust fuel delivery for an optimal air/fuel mixture.
The bandwidth of the H-D O2 sensor is narrow, but allows changes within many naturally aspirated performance parameters. Naturally aspirated refers to carburetion and EFI where air breathing operates within the natural laws of physics, such as low pressure. However, an increased bandwidth O2 sensor used with some aftermarket, self-tuning ignitions will make this ESPFI cook in conjunction with supercharging and turbocharging. Boost from forced aspiration, also known as ram flow, can change cylinder pressures and rpm capabilities rapidly.
Wide bandwidth O2 sensors increase the system’s reaction time, so it can deal with and relay fast changes to the ECM to prevent possible injurious extreme heat situations. The previous 8-degree angle fuel injectors are now at a more proper 25 degrees. The 2006 Dyna TC 88 introduced a Delphi 46mm EFI venturi throttle body. The 2007 TC 96 models carried over the use of 46mm bodies with a 50mm Screamin’ Eagle option. The 2007 CVO 110 is also fitted with the 46mm throttle body! The Screamin’ Eagle upgrade is now a 58mm body, which, in my opinion, is a mistake. This is going from too small to too big for the CVO 110. The 58mm EFI throttle body needs at least 100 rear-wheel horsepower to come into its own. Sad to say, I don’t believe the CVO 110 fits into the rear-wheel 100-plus horsepower club. This 58mm body will not go to waste, as it will be ideal on a larger engine. Of course, this all pales in comparison with the anemic and paltry 38mm throttle body on the early Magneti-Marelli EFI systems used on 80" Evos and the first TC 88s.
H-D Assists
The EITMS, also known as idle temperature cool down, turns off the rear cylinder fuel injector at hot idle. Why would we do this when fuel is the cooling agent and air causes the villainous heat? Burning fuel, assisted by maximum air, generates heat in a too-high air-to-fuel ratio.
The 2007 EITMS offers a cooling feature for hot idle conditions. This engine calibration procedure is available for all FLHT Touring models plus police-specific FLHTP, FLHP, and FLHPE motorcycles. This is an option available for all these models, free of charge from your H-D dealer (as is a one-time deactivation if you don’t like it). EITMS meets the needs for those that ride in congested traffic on a regular basis, or who need to leave their bikes idling, as in a police situation. It also assists in a overheating situation, when the bike returns to idle. The calibration offers limited rear cylinder cooling when cylinder temperatures reach a certain level. Once EITMS activates, the rear cylinder still functions without fuel.
Air is still sucked in on the intake stroke, compressed on the compression stroke, decompressed on the power stroke, and exhaled on the exhaust stroke. The air acts to cool the engine’s rear cylinder while only running on the front cylinder. Once activated, the EITMS will only function when there is a high engine temperature, the engine is at idle speed, the bike is not moving, and the transmission is in neutral, or if it’s in gear with the clutch lever disengaged. When all of the above conditions are met, the rear cylinder will stop firing. EITMS will allow a supply of fuel to the rear cylinder if the temperature decreases, the throttle is increased, the bike moves forward, the clutch engages, or if the bike shifts out of neutral with the clutch engaged. When this happens, the rear cylinder and, therefore, the engine, will begin running normally. The potato-potato idle sound will be different, since only one cylinder is contributing a potato to the noise rhythm while there is the sound of whooshing of air from the other. This will also affect the exhaust smell. I mention this to allay fears that not all is right for those not prepared for these normal EITMS side effects.
The factory has also developed a fan (#91550-00C, chrome; #91531-00D, black) that installs on Touring FLHTs to lower engine oil tank temperatures a claimed 20 degrees Fahrenheit (measured at the oil tank) when using the fan. Harley includes its premium eight-core oil cooler on the CVO 110 to assist in combating higher oil temperatures. I believe that H-D only has a 9.15:1-9.3:1 compression ratio on the CVO 110 to combat higher cylinder temperatures by reducing compression. This is necessary for meeting EPA current and future standards, but is a step in the wrong direction for a performance engine. Further Harley-Davidson assists need to be in the redesign department so that engine components will not wither in the onslaught of high air-to-fuel ratios.
Aftermarket Assists
BAKER Drivetrain now has the Plus One oil pan, which fits 1993-2008 FL Touring models. This setup increases oil capacity a full quart for a reduction in operating temperatures and an increase in engine durability. Everything is about temperature because it doesn’t require a rocket scientist to understand that the cure is about less heat. Any method, or more correctly methods, offering an assist to a cooler operating cylinder is good. The eight-core turbulated H-D oil cooler is a great idea for any Twin Cam. It’s a stock and very necessary component on the CVO 110. As I’ve said, its addition to the CVO 110 is an attempt to control cylinder head temperatures, much the same as the rather anemic compression ratio of 9.15:1-9.3:1. Turbulation mixes the oil for superior heat dissipation.
Coolers without turbulation only cool the outside layer of oil when there’s laminar flow, an inefficiency that leaves central layers of oil leaving the cooler as hot as it was when it entered it.
However, I feel that only one oil cooler is not enough. As Bob Wood has taught me, we need more cooling to lower cylinder head temperatures to between 210-220 degrees F, even though the literature lists 225 degrees as a manageable temperature. It’s not a good idea to run two H-D oil coolers in tandem because of pressure drop. Oil restriction causes pressure drop, and we don’t want to risk starving the engine of oil.
Externally, I recommend running two 10-core Jagg oil coolers in tandem on any high-performance Twin Cam. I have them on my personal bike and the combination works well. Internally, we need to lower the air relative to fuel ratio. I have discussed bigger injectors, as more fuel will lower injurious rear cylinder temperatures. A bigger injector like that used in the 50mm throttle body for the rear cylinder will stay on for the same amount of time (pulse width), but with more fuel squirted in to effectively lower the air/fuel ratio. On Chris’ CVO, I installed the complete 50mm throttle body with the larger injectors.
Colder spark plugs are another small assist to the equation. Spark plugs come in a variety of heat ranges. Running a colder plug in the rear cylinder is desirable in the case of the CVO 110. Any yesteryear or current Shovelhead owners are well acquainted with this procedure, as H-D wrenches have been using different heat range spark plugs for a long time. Changing the exhaust can also remove more heat from the engine, or, conversely, help contain it.
Redesign The Cylinders
The CVO 110 cylinders need a redesign to cope effectively with the heat. Harley-Davidson cannot use the same techniques on the CVO 110 as used on the TC 96. The cylinder bore is just too big relative to the placement of the cylinder studs and oil return dowel. I know I have said there are no overt symptomatic problems associated with the front CVO 110 head and cylinder. But I feel they are lurking just under the surface, so to speak, since the safety margin is thin. In other words, adverse conditions may push the front cylinder over the brink, so it joins the rear one with its myriad problems. I also feel that these cylinders, front and rear, would be able to cope without redesign if the air/fuel ratios could be lowered in closed-loop mode. The Motor Company is between a rock and a hard place. It needs to use newer technology to cope with stoichiometric heat, especially when the cylinder is shrouded from the air stream. It cannot simply lower air/fuel ratios, since it will not be EPA compliant.
In any case, the component parts must cope with stoichiometric ratios that escalate well above 14.7:1 due to shrouding, with the result being heat-induced ratios approaching 16.0:1. The redesign should include the head alloy composition so it doesn’t warp under these conditions. This situation is a harbinger of the future. In a nontraditional setting where functionality rules, a water jacket and cylinder configuration redesign would easily win out as the solution to this excess heat. Currently, this is not an option, but it’s a coming necessity.
Relocating Oil Return
The rear head’s oil return passage is located next to the exhaust valve on the head gasket surface. The exhaust valves are always smaller than the intakes. The carbon texture of the exhaust valve’s outer head bakes white due to the extreme heat in the CVO 110’s combustion chamber. The larger intake valve outer head remains a dark and familiar carbon color, indicating that the heat is not injurious on that side of the combustion chamber. This may seem strange to the uninitiated, but the temperature is much higher on the exhaust side of the combustion chamber because of the super-hot exiting exhaust gases. The intake valve is cooler because the air and fuel entering the combustion chamber is at ambient temperature. The temperature change between the two valves can be well over 100 degrees F.
A partial solution to the oil leakage, but not head warping, problem would be to relocate the oil return juncture away from the hot exhaust valve and bring it closer to the cooler intake valve. This involves an easy, but more complex and do-able machining procedure. Lowering heat, which is the main culprit, is a difficult undertaking for those producing an air-cooled engine with in-line front to rear cylinders. The rear cylinder is shrouded from the cool airflow and bakes in the heat dissipated from the cylinder in front. Redesigen cylinders with more meat to accommodate the
O-ring, or a similarly effective gasketing technique, could absorb some part warping without leaking.
Article continues in next thread. Check back issue for pix and extra information. |
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