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Caveman Hammer Mechanic
 
ClickClickBoom's Avatar
 
Join Date: Feb 2009
Location: Boulder Creek CA
Posts: 3,005
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Quote:
Originally Posted by gr jetson View Post
In past threads concerning Clewett's serpentine fan belt innovation, several people argued that it is a solution looking for a problem to solve. I found such comments a bit unconvincing. Clewett has a well-deserved reputation for making carefully engineered products, so he doesn't need to make questionable products that serve no purpose. Further, just because Dr. Porsche's original design works well, that does not mean that it cannot be improved upon. Another of the things that confirms Dr. Porsche's genius in his design of the 356 and 911 is that so many brilliant people around the world are working to make small but significant improvements on them. No one is trying to do that with the Ford Fairlane.

It is significant that every car maker in the world has now adopted the serpentine fan belt configuration. So, perhaps this is a good time to look at the evidence for its use in the 911.

So, ClickClickBoom, even though it is above your pay grade, could you share the evidence concerning volumetric efficiency, pumping losses of oil, and cylinder head temperatures with respect to the serpentine fan belt that not only made you feel comfortable using it, but convinced you it was a genuine improvement in terms of reliability and cooling efficiency?

You might not be able to relate everything the engineer shared with you, but your insights would be helpful to us. ClickClickBoom, thank you for being so diligent on this issue!

Cordially,
Greg
Ok,
You asked for it.
Volumetric efficiency would not be impacted by a warmer cylinderhead, the air is moving too fast to be heated any measurable amount. But a cylinderhead that is warmer to a degree will lose less combustion heat due to a smaller heat delta, and thus impart more push per cylinder event. I have always have thought that the oil mayo in the oil tank was a bit troubling.

Oil viscosity is a horsepower sink in and of its self. Cooler oil has more viscosity, and as such will require more power to move a given volume.

Both Lycoming and Continental aircraft motor producers both state that their operating temperatures for both oil and cylinder head temps where colder is not necessarily better.
https://www.lycoming.com/sites/default/files/IOM-IO-390-C%20Series%20-%201-31-17.pdf
Typically cylinder head temps below 435F and oil temp between 160-235F maximum.
Aircraft typically will use cowl flaps to control cylinder head temps.
I thought that moving towards a more modern belt drive system. Since the availability of the OEM spec belt is almost impossible, a modern system couldn't hurt. For the record , I have never had a problem with the original v-belt. One might note that oil temps have been a quest of sorts in the past. My 3.2 has, for me always been uncomfortably cool on the oil temps. When I noticed an increase of the oil temps, into the typically normal operating range I was a little shocked and went on a quest for answers. Also, until someone instruments an engine with thermocouples with an eye on cylinder head temps in the spark plug gasket area, this is an uninformed academic theory/hypothetical exercise. Oil temp typically follows cylinder head temps with a delay in recording and sending the temps. Don't forget where the oil temp is sensed at, a location on the crankcase, not the oil tank, submerged in tank oil.
If you search cooling fan in the forum search function, you will get no shortage of info/results. I did find that the 3.2 fan moves the most air of the fan setups. Upwards of 1500 LPM, from the aircraft world cooler is better until you get too cool, there is a Goldielocks zone for engine cooling, finding it is the real quest, environmental, engine equipment and car install all have an effect on cooling efficiency. Oddly, having a fan that uses RPMs to transmit the cooling medium, without any thermostatic control is solid 1950s tech. The only saving grace are the engine and aux thermostatic elements in the oil system. It is a testiment to the original engineers that it works as well as it does. Look at the number of fan combinations over the years.

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1984 Carrera El Chupacabra
1974 Toyota FJ40 Turbo Diesel
"Easy, easy, this car is just the right amount of chitty"
"America is all about speed. Hot,nasty, bad ass speed."
Eleanor Roosevelt, 1936

Last edited by ClickClickBoom; 06-03-2019 at 09:03 PM..
Old 06-03-2019, 08:42 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #21 (permalink)
Caveman Hammer Mechanic
 
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Join Date: Feb 2009
Location: Boulder Creek CA
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Well,
The Central Coast of California has been in the throes of too much heat. 102f in the Santa Cruz Mountains, took the car out, and was watching the temps like a hawk. I will report a slight increase in oil/case temp never went above 210f, even with the skinny pedal closer to the floor. Did all the stuff you shouldn’t, 5th gear at 35mph, uphill, ugh, couldn’t get the temps into the stupid zone, it’s almost like as the temp goes up, the car just sends more oil to the front cooler. The higher temp delta almost seems to be more efficient in transferring heat. The engine seems a bit perkier above 5k rpms, maybe reduced cooling drag?
Wishful thinking?
Oh well, the thought that I now have a more modern fan belt, with more wrap on the pulleys, and not having the wrong sized v-belt, due to sourcing issues. I can get the Clewett belts on eBay all day long, Gates brand cheaper than the OEM Conti v-belts.
__________________
1984 Carrera El Chupacabra
1974 Toyota FJ40 Turbo Diesel
"Easy, easy, this car is just the right amount of chitty"
"America is all about speed. Hot,nasty, bad ass speed."
Eleanor Roosevelt, 1936
Old 06-13-2019, 11:19 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #22 (permalink)
Caveman Hammer Mechanic
 
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Join Date: Feb 2009
Location: Boulder Creek CA
Posts: 3,005
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Correspondence between Richard Clewett and myself:

Richard,
As per out conversation; in regards to the crank /fan ratios.
I recall my car(’84 Carerra w/28 tube fender cooler) has aprox 1” total clearance on the crank pulley, and the alternator/fan has no clearance issues.
Normal cruising oil/crankcase temps show about 195f at 65mph and OAT of 65F.
Driving through the Mojave desert near Palmdale with OAT of 104 and altitudes of 3500 msl to Grapevine altitudes, oil/cranckase temps exceeded 250f +. Various RPMs and speeds did little to reduce the temps.
Nice chatting
Eric Martin


Hi Eric,
Thank you for the feedback and data. It is very helpful. I've had a chance to take a look at the higher fan ratio and think you will be pleased with the results. The 3.2 motor mount console has the extra space required for the longer belt and larger crank pulley. The fan pulley will remain the same, but a smaller idler pulley is required. We can achieve the fan speed of 1:1.7 which is much closer to the stock fan ratio. Your current setup is 1:1.47 which is a little faster than stock for the early 2.0 - 2.4 engines.
I'll be making a few crank pulleys for stock and offer this configuration as a standard street car and turbo version for the 84-89 model years.
I'll let you know when they are done.

--
Best regards,

Richard Clewett
Clewett Engineering, The complete solution for ignition & fuel injection
richard@clewett.com

I sent my email after a full 1/2 hour of conversation about the ratios. This is crazy fast for any company. Thoughts on the new ratios?
__________________
1984 Carrera El Chupacabra
1974 Toyota FJ40 Turbo Diesel
"Easy, easy, this car is just the right amount of chitty"
"America is all about speed. Hot,nasty, bad ass speed."
Eleanor Roosevelt, 1936
Old 01-07-2020, 09:47 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #23 (permalink)
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Excellent!

Old 01-08-2020, 04:34 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #24 (permalink)
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