Why & How to Cool Down Your Twin Cam Engine PART I

[DK Custom Products]

Cooling down Your Harley-Davidson Twin-Cam Engine Dyna-Softail-Touring-Trike

Why bother cooling down the engine on your bike?

1. It will last longer
2. It will be more comfortable to ride (less felt heat)
3. It will have more power (enough that you will feel the difference when you twist the throttle)
4. It will get better MPG

Twin Cam engines have always been hot, but starting in 2007 they have been much too hot for their own good.



On a warm day, and after 45 minutes of riding, It is not unusual to see oil and head temps well above 270*, and on the heavier bikes/trikes, 300+ degrees is considered “normal”, “they all do that”.

It is in the fundamental design, plus the epa requirements that continue to rain down on The Motor Company.

Whether it is the air-cooled or the Twin-Cooled (aka- wethead or waterhead), they are designed to run hot, and, for the most part, they will continue running (albeit poorly) for quite a long time.



But it is at the sacrifice of:

Rider & Passenger Comfort
Reduced (sluggish) power
Poor fuel economy
Component failure

This article addresses a little in the understanding of Why they run so hot, and More on what can be done to cool them down...Both Air-Cooled & Twin-Cooled.

Which Heat Do You Want to Get Rid Of?

Reduce Actual Heat for the engine, to help it run better, or reduce Felt Heat by the Rider and/or Passenger for comfort?

They are not necessarily the same.

I prefer to keep the heat for the engine in safe temps...what is good for the engine.

That will have a significant effect on reducing felt heat to the Rider & the Passenger. There are ways to get rid of felt heat, at the cost of increasing actual engine heat.

We will not be discussing those.

Why do Twin-Cam engines run hot?

1. The Twin-Cam squirts oil at the underside of the pistons.
   
   This is done to cool the pistons, but it transfers that heat to the oil that then circulates the heat thru the entire engine.
2. EPA compliance dictates that they run lean (too lean, which creates excessive heat and reduced power) for reduced emissions.
3. EPA compliance dictates that they are quiet. This excessive baffling works against the engine, creating more heat.
4. EPA compliance regs on emissions are partially met by a catalytic converter. This creates significant felt heat.
5. EPA compliance regs on emissions require that oxygen depleted, oil laden, hot air be pushed into the “fresh air” intake (air cleaner), resulting in less than optimum combustion, which creates even more heat.
6. EPA compliance regs on emissions are partially met by “epa cams”.
   
   
   
   These cams are designed to create even more heat, in an effort to reduce pollutants exiting the exhaust.

Unique to the Twin-Cooled (air-cooled/liquid-cooled hybrid), also known as waterheads or wetheads: The basics are the same on the Twin-Cooled as the Air-Cooled, with the addition of the following:

1. They have a higher compression, which creates more heat.
2. They have slightly “hotter cams” which create more heat.
3. The water pump is in the location where Harley normally puts the oil cooler, resulting in NO oil cooler.
   
   So the oil and all portions of the engine, except the liquid cooled heads, are even Hotter on the Twin-Cooled engines than the air-cooled.
4. The felt heat from just the top couple of inches of the engine are cooler due to the liquid cooling.

Bottom line is the Twin-Cooled has Twin Problems:

• While the heads are cooler, the rest of the engine is hotter
• The oil gets hotter with no oil cooler to dissipate the heat.

How to Cool Down the Twin Cam Engine?

We have been working on this for years.

Thousands of hours, tens of thousands of miles of testing various solutions. Up front, it is important to recognize there is No One Magic Bullet.

There are many things that each contribute varying increases in cooling.

Only when combining all, or most, of them is an acceptable level of cooling obtained.


Our target temperatures are:

Cylinder Head Temperatures, as measured at the rear cylinder by the temperature sensor that reports to the ECU: 230* F everyday riding, with no more than 250* F in extreme circumstances.

(at 270* F you will feel the sluggishness in power, and engine longevity is being reduced)

Oil temperatures, as measured in the oil tank or the sump: 230* F everyday riding, with no more than 260* F in extreme circumstances.

(at 270* F you will feel the sluggishness in power, and damage is occurring)

Steps to Cool The Twin Cam Engine Down
Outlined in Part II

Kevin

[DK Custom Products]

Cooling down Your Harley-Davidson Twin-Cam Engine Dyna-Softail-Touring-Trike Part II

Here are methods that are proven effective at cooling down the Twin Cam Engine.

They are organized by cost & effectiveness.

Inexpensive (under $100):

1. Remove the left side thigh protector. This will help the air flow very fast past the rear cylinder and out the left side...this is good for the engine, and will reduce the amount of felt hot air on the right side.

With the right side shield still in place, it acts like an air scoop pulling air into the space behind the cylinder...but with the left side removed, that air can now exit easily. With both installed, they are essentially two scoops that push air from both sides to collide and swirl, with no real good place for the air to exit.

It is not symmetrical looking, BUT, you can only see one side at a time, so it is unlikely most will notice you have a thigh protector on one side and not the other.

Doing this will cool the engine overall, so while riding & when coming to a stop you have a cooler engine than you would otherwise. However, if you are at a stop long, or in continuous stop & go, you will feel more heat on the left than the right.

2. NO fork wings or umbrella baffles when ambient temps are 70* or more. These block a substantial amount of air that should be flowing past the engine. With them installed they typically raise engine and oil temperatures by 20-25* F.

3. This next one can be No Cost or High Cost. Remove the Catalytic Converter. This will not decrease engine heat very much, but it will reduce Felt heat tremendously.

You can remove it from your stock headers, this takes a bit of work. You can purchase aftermarket headers, like the V&H Power Duals, that do not have a catalytic converter in them.

4. Install a Tank Lift with a Deluxe Option. Not only will you benefit from a 10-15* drop in engine temperature, more of your chrome will be visible, it will be easier to clean, and many experience less buffeting.

Without a tank lift the tank is covering the top of the engine, trapping in the tank channel. It is also preventing air from flowing over the engine. With a tank lift, air that previously was hitting the front of the tank and flowing over the top of the tank to hit the rider in the chest….that air is now flowing Under the tank, and across the engine, cooling it down.

5. Install Cooling Wings. These take air that previously went around the tank and over the tank and redirects that air to shoot directly onto the engine. These can be used with or without a tank lift. They provide an additional 8-10* drop in engine temperature.

They also make for less rider and passenger buffeting.

6. No matter what air cleaner you are running, make sure that it has an [B]External Breather System (EBS).[/B All DK Outlaw Air Cleaner Systems come with an EBS as part of them. But if you already have an air cleaner that you are happy with, make sure to modify it with an EBS.]

An EBS will prevent hot, oily, oxygen depleted air from flowing through your throttle body and into the combustion chambers.

Having only cool, clean, oxygen rich air going into your engine makes for a stronger & cooler running engine, plus one that does not get carbon build up on the pistons which causes more heat and pinging down the road.

7. XiED's will help the engine run more efficiently, resulting in a cooler running engine.

This is better than a Dealership download, but not as good as a flash tuner like the FP3 or Power Vision. We have many Customers running the XiED product on their Rides that are completely happy with it. The engine will definitely run cooler, stronger & last longer with them installed...I am not sure it will last any longer with an FP3 or Power Vision, but you can get extra performance out of the FP3 or Power Vision. The XiED product typically lowers engine temperature by 5-10*.

8. Free flowing exhaust slip-ons are a very important factor in cooling the engine down. The stock exhaust mufflers (slip-ons) are restrictive, resulting in the engine fighting against itself. In doing that it generates heat with no resultant forward movement.

By removing this restriction, you are allowing a free flow of exhaust exiting the engine, which plays an important role in keeping the engine cool.

The stock headers on Harley’s are very respectable, and are not restrictive.

Replacing them will not have a significant benefit in lowering engine temperature. If your Catalytic Converter is in your headers (all Touring & Trike models) you can remove it, or replace the headers for a reduction in Felt heat from the exhaust.

There are many choices in Slip-on’s. Some of them can get quite expensive. If you are not sure what you want (sound wise), it may be best to modify your stock Slip-ons by removing the baffle and installing some Thunder Torque Inserts.

Our experience has shown that this creates the most power and the coolest running Slip-on you can get, besides being the least expensive!

However, they will not be quiet. Check out some Youtube videos. If you want something more quiet, check out bike nights, figure out what sound you like. Once you have your slip-on’s, add some Thunder Torque Inserts to them. You will get more power for less gas burnt.

This will result in a cooler running engine (besides being stronger).

The above can be Low, Moderate, or High Cost


Moderate Cost (under $200)


10. A Free Flowing Air Cleaner System (with an EBS) is a very important factor in cooling the engine down.

The stock air cleaner is restrictive, resulting in the engine fighting against itself. In doing that it generates heat with no resultant forward movement.

By removing this restriction, you are allowing a free flow of cool air thru the engine, which plays an important role in keeping the engine cool. With a good free flowing air cleaner you will typically see a 8-15* drop in temperature.

11. Re-locate the oil filter. Not only will this put the oil filter out in the wind, it will let more air hit the engine, and it will make for mess-free oil changes.

This will result in an 8-10* drop in oil (and engine) temperature.

12. A Permanent High Performance Oil Filter. These give superior oil filtration, reduced drag on the oil pump (engine does not have to work as hard=less heat), and the finned billet case provides a small amount of extra cooling.

It'll be cost neutral after 10 oil changes)


Higher Cost (over $200)


13. Flash Tuner. Twin Cams run too lean from the factory. Again, this is to meet EPA guidelines. Whether you add free flow intake and exhaust, or keep the restrictive intake and exhaust, the engine will run cooler, longer, stronger, & more efficiently with a better tune.

Above, in point #7, the XiED will add more fuel, which is a big step in helping the engine run stronger and cooler, and is an excellent budget solution.

However, a full tune, which includes adjustments to timing and a host of other tables, can be achieved with a Power Vision, FP3 or a host of other tuners. You can see a complete overview of popular tuners at this LINK.

Whichever device you use, it will pay dividends in a cooler running, stronger engine. Typically you will see a 10-15* drop in engine temperature.

14. Oil Coolers. These are powerful tools to achieve a drop in oil & engine temperatures.



Below are three distinctly different situations that Twin Cams Fall into-

FIRST- Air Cooled Twin Cams that already have a factory Oil Cooler

There are two routes to go with a Twin Cam that already has a Factory Oil Cooler-

A. Add a second oil cooler. If you have lowers, use the Dual-Cool Oil Cooler, if you don’t have lowers, add a 10 Row Oil Cooler off the downtube.

This is a proven method that we see typically adds a solid 25* drop in temperature.

AND/OR

B. Replace the factory Oil Cooler with a Fan-assisted Oil Cooler. It is not just the fan that helps, but the actual oil cooler is much better at shedding heat than the, less than quality, OEM cooler.

Every time we have done this we’ve seen a solid 20* drop in temperature.


SECOND- Air Cooled Twin Cams that have no factory Oil Cooler

You can add a low mount or side mount oil cooler to any Twin Cam.

The side mount (down tube) are not as discrete as the low mount, but they are more out in the wind, resulting in a minimum of 25% better cooling than a low mount of the same size.

These typically give anywhere from a 20-40* drop in temperature (depending on size and low or side mount).


THIRD- Twin-Cooled (Wetheads) Twin Cams

Use the Dual-Cool Oil Cooler, specifically designed for the Twin-Cooled Engine.

Combined with the CnC Oil Filter Relocation you should see a 30-35* drop in temperature.


15. Cooling Fans. For decades there have been “parade” fans. A fan that mounts on the left side of the engine and blows air between the cylinders.

This is better than nothing, But they are very poor at cooling compared to the newer style fans that blow air directly across the heads and cylinders.

Wards Parts Werks & Love Juggs (Love Juggs is a Sponsor on this forum) both center at the spark plug on each head. Not only does this blow air across the fins on the heads and cylinders, it pushes air thru the channels that are in the heads. This results in an amazing amount of heat dissipation, both when sitting still and while moving.

These fans are easily good for a 50* drop in engine temperature in stop n go traffic on a hot day.



Even at highway speeds they are good for a 10-15* drop in temperature.


Summary:

On Air Cooled Twin Cams, if all, or most, of the above are used, the ideal balance of having the same oil and cylinder head temperature of no more than 230* after 45 minutes of riding on a warm day at highway speed is achievable.

On Twin-Cooled Twin Cams it is a bit different.

The heads will always be cooler, the oil and rest of the engine will always be warmer.

By using all, or most of the above, the heads should easily stay Below 230*, closer to 210-220 on a warm day. The oil temperature, and the rest of the engine is likely to be between 230-240* on a hot day after 45 minutes of highway speed travel. This is ok.



It still allows for a spike in extreme conditions, while keeping the temperature below the 270* mark, which is where sluggishness in power starts being noticed, and where engine longevity is being sacrificed.

While there are other things that can be done (swapping cams, headwork, etc.), what is listed above is relatively inexpensive, easy to do, and we’ve never seen any of it void a warranty.

These modifications are the result of years of looking for the best way to cool these down.

Thousands of hours of thought, fabrication, testing, riding, & measuring, seeing what works and what doesn’t.



We are not necessarily done. We may discover other solutions, but for now, the urgency of our quest for reduced temperatures is abated. We have found what works for engine performance, engine longevity and rider/passenger comfort.


Kevin