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Which upgraded fan is better?

I do recommend using the DMax fan, it works great. Especially over the older 6 blade fans. People with the newer 9 blade fans may not need an upgrade, but if upgrading might as well get the Dmax fan. I did not have to trim my shroud at all.
 
Crap, I can't find the the thread on modding the fan clutch, I vaguely remember shortening the bi-metalic spring.
 
shorten would't be the right word. loosen the coil would be more appropriate. make the bend closer to the end of the coil.
 
robzombie4551 said:
Of course he's right, He's trying to sell you something. If the fan doesn't matter why would he try to sell the combo.

Buddys right, and others have said the same thing, that's why I dmaxed and modded my clutch and have been trouble free since. I even had to back off a little on the clutch mod because the dmax fan was way more effecient than the stock steel one.
From what I understand the kennedy clutch comes on to soon and stays on to long.
Click to expand...

This is exactly the design limit of the viscus clutch. Let me explain it better.
Slap your foot to the floor and hold it there. Because you are on a hill with a trailer and an underpowered engine to do the job. Even a Duramax will heat up doing this but will be closer to the speed limit.

The foot on the floor is going to start to heat things up. There is a time it takes for the thermostat to open if not already and radiator to heat up. Then the big delay - the thermal spring on the fan has to heat up. After it has heated up fluid has to move in the fan clutch to the working chamber to lock the fan in.

The above outlined delays mean your temperature gauge is going to move quickly to and over the 215 mark without the fan locked in. Engine is generating maximum heating to the coolant and the fan is not on so everything stores the heat in the form of getting hotter. When the fan locks in the temperature rise will slow and hopefully stop. At full load it is not likely to go down much because everything has a bunch of stored heat to get rid of now from the time working hard without the fan being on.

To only ways to get around this spring heating delay is a Electro Viscus fan clutch where the obsolete thermal spring is replaced with a electronic control OR go with a temperature set on - off Horton type of clutch. This allows the fan to lock in "wham - now" when the engine gets hot rather than having to wait for a spring to warm up. The Elecro viscus clutch computer programming from GM follows the same MPG and less customer fan noise GM philosophy and makes me suffer in AZ due to poor AC performance. Thus, I have to reprogram the EV clutch on my Trailblazer to come on sooner if I want cold AC when it gets over 105 outside degrees. The engine will run at 230 ECT degrees out here - not good on 91 octane with 10-1 compression, gasser. Dodge on their diesels offers the EV clutch design to keep the temperature under control better than the obsolete, less complicated and cheaper spring thermal clutch design. Duramax was supposed to go to this but a Bankrupt GM eliminated the clutches from the Trailblazers in 2008 and did not equip the Duramaxes with them. Bean counters at their best. :thumbsup:

The sooner you start to bring on the fan the lower the max temperature will reach because you have the fan working at a lower temperature. Trade off is it will cool things down to it's kick off point before unlocking.

Ask Missy, there is a post on here from the last discussion on fans. The factory fan comes on too late for the head crack temperature red line of the 6.5 at 215. But because customers complained about the fan noise and I maintain for increased MPG GM raised the temperature of the fan clutch to keep it off as much as possible. Sadly the 6.5 is not an engine that likes the higher temperatures and likes to crack stuff.

My experience with the Kennedy clutch is that it tended to lock in fully and then kick out. Course this was while fully loaded. It would hit 215 max if I hit a minor hill at 65. It was usually full on before the 215 mark and kept me under it no matter what I did to it. 62 MPH flat out or 33 MPH flat out, 14 PSI boost, high altitude, dry air, extra fuel, and over 105 outside air temps.

I loved to hear the fan run because when the dead factory one did not work I got to see the crankcase through a hole in a scuffed piston after head removal due to overheating the 6.5.

The airflow through the radiator on our body style is a problem. We don't get enough due to the aerodynamics designed to get us the best unloaded MPG of the big three. To improve airflow heavily loaded you need to hear the fan run. Dodge gets the same 'poor' MPG loaded or not due to wasted airflow through the engine compartment when not needed.

So Mr. Kennedy is not so much just selling you something. He is selling you something that does what is advertised to keep your engine cool by shifting the kick on temperature lower and away from the critical 215 mark. Mainly, if you ask Missy, he has a reverse rotation 6.2 clutch with the old school set point.

I imagine Heath's system works well, but, I have not used it in the extreme dessert hot environment I have here. The balance flow issue the newest water pump solves is something to look into. Price being a factor is why I have the above experience and not with Heath...
 
I used a stock Hayden Severe Duty, and I'm going to see if I can return it. Doesn't come on fast enough. I'm really bummed. I'll probably go with the Kennedy. I'd rather have it come on too early. In Boise, the roads are flat, then some little hills, which don't engage the clutch, then, whoa nelly, an unreal monster.

White Bird pass is about 2500 feet of climb over 7 miles. It is steep, long and usually crazy hot. I really wanted to hammer on the throttle, but quickly hit the 210 without the clutch engaging, so I backed way off. I don't want to rebuild my motor again.
 
turbovanman said:
Interesting, I've modded customers before and no issues.

I emailed Kennedy and he said the fan's don't really do much, its the combo of his special clutch and fan that do the business, now I am really confused, sigh.
Click to expand...


This is the truth. The fan is not the key, it is the clutch. The Hayden clutch is nothing more than the OE clutch. Same calibration as OE. The Kennedy clutch is specially calibrated to engage a full 15°f lower than stock. The issue at hand is that the OE clutch does not engage until it is too late. When developing this clutch we had to choose one style. We chose the 1997 4 stud version because it fit anything 1990+ with serpentine belt and 4 stud hub. The threaded hub is of no benefit. Altering the spring can be done, but is merely a guess.

Blades: The subject of blades came up when developing the Kennedy clutch. The Engineer that I worked with had access to the fan blade test data and we compared and discussed. The blade chosen was teh 1997+ steel blade. The Dmax blade will bolt right on, BUT at 21" offers very little benefit in air flow, in fact the 20" steel blade outperforms the 21" plastic blade in some areas and this flips in others. Best way to put it is when you need it most the steel blade torques on through at higher static pressures where the plastic blade flexes.

P.S. The dmax calibration has been increased even further and then the LLY even further yet...
 
The threaded water pumps are also better than previous editions. If upgrading water pumps on any 6.5 I would put the 2000 (1999.5+) water pump on it.
 
Kennedy Diesel said:
This is the truth. The fan is not the key, it is the clutch. The Hayden clutch is nothing more than the OE clutch. Same calibration as OE. The Kennedy clutch is specially calibrated to engage a full 15°f lower than stock. The issue at hand is that the OE clutch does not engage until it is too late. When developing this clutch we had to choose one style. We chose the 1997 4 stud version because it fit anything 1990+ with serpentine belt and 4 stud hub. The threaded hub is of no benefit. Altering the spring can be done, but is merely a guess.

Blades: The subject of blades came up when developing the Kennedy clutch. The Engineer that I worked with had access to the fan blade test data and we compared and discussed. The blade chosen was teh 1997+ steel blade. The Dmax blade will bolt right on, BUT at 21" offers very little benefit in air flow, in fact the 20" steel blade outperforms the 21" plastic blade in some areas and this flips in others. Best way to put it is when you need it most the steel blade torques on through at higher static pressures where the plastic blade flexes.

P.S. The dmax calibration has been increased even further and then the LLY even further yet...
Click to expand...

Ok, thanks.
 
The D Max fan blade made all the difference in keeping my temp in check....and I've had, tried, installed and confirmed that the D Max fan flowed/pushed/sucked/blew more air than the old 6 blade (no brainier), the 20" 1997+ Steel 9 blade....Everyone can say what they want, tell me about engineers documentation, R and D, flex, pitch and/or any other variables, but fact of the matter is, when I put the D Max blade on my temps were under control, my A/C temp stayed cool at idle (unlike when the 20" 9 blade fan couldn't achieve this) and my temp never got over 210* after the D Max blade was installed.

Myself and many other members have all agreed that the D Max fan seems to work the best....and 95% of D Max blade "fans" do/did "NOT" have to trim the shroud for clearance.

Now I don't know about you, but I value and trust the members of this forum and when the majority is in agreement about a specific issue, 99% of the time it is the law.....Of course there are exceptions but we (the members) drive, diagnose, discuss and repair these 6.5 engines everyday and I would say that makes us (the members) the experts (collectively, of course).

2 Cents
 
turbovanman said:
Ok, thanks.
Click to expand...

Kennedy Diesel said:
This is the truth. The fan is not the key, it is the clutch. The Hayden clutch is nothing more than the OE clutch. Same calibration as OE. The Kennedy clutch is specially calibrated to engage a full 15°f lower than stock. The issue at hand is that the OE clutch does not engage until it is too late. When developing this clutch we had to choose one style. We chose the 1997 4 stud version because it fit anything 1990+ with serpentine belt and 4 stud hub. The threaded hub is of no benefit. Altering the spring can be done, but is merely a guess.

Blades: The subject of blades came up when developing the Kennedy clutch. The Engineer that I worked with had access to the fan blade test data and we compared and discussed. The blade chosen was teh 1997+ steel blade. The Dmax blade will bolt right on, BUT at 21" offers very little benefit in air flow, in fact the 20" steel blade outperforms the 21" plastic blade in some areas and this flips in others. Best way to put it is when you need it most the steel blade torques on through at higher static pressures where the plastic blade flexes.

P.S. The dmax calibration has been increased even further and then the LLY even further yet...
Click to expand...

I disagree on the Hayden SD being the same as OEM. I have it and it is definitely not the same but I do agree with you on the fan blades. I have the stock steel 9 blade and it works very well. The achilles heel of my combo is the inherent late engagement. i will do mod next time for sure.
 
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