Coach performance charts

[oldmansax]

There have been a number of threads on HP requirements, wind resistance, cooling,  and other performance issues on the board. I ran across this article on the Wanderlodge board that has a lot of good info. It pertains to Cats but the charts are generic so engine make would not be an issue.

Let the dreaming begin!   

TOM

PS: I think I want a 12V-71   

https://ohe.cat.com/cda/files/287140/7/LEGT5364.pdf

[kyle4501]

Interesting info.
Page 8 shows fan HP requirements. As much as 60 HP to drive the fan when at top speed in a gear. . .

Sheds a little more light as to why cheap electric fans will not work . . .

[HighTechRedneck]

Thanks for the link.  That is a fascinating read.

[artvonne]

Interesting info.
Page 8 shows fan HP requirements. As much as 60 HP to drive the fan when at top speed in a gear. . .

Sheds a little more light as to why cheap electric fans will not work . . .

  Does the cooling system require a 60 HP fan, or is that simply how Cat designed the fan/engine? I note the MCI's have a belt driven fan up top, and there is no way that belt could transmit 60HP. I would be surprised if it pulls much more than 5 HP. And there would be a power loss because of belt and gear transmission. A couple large electric thermostatically controlled fans might be sufficient, CFM is the key. Whether you get it with 6 HP, or 60 HP, CFM through the radiator is the main factor.

[uncle ned]

On another fan debate.   Where is two dogs when we need him.  any one ever seen a 10 hp electric motor.   big


uncle ned

[luvrbus]

Those blower fans on a MCI pull 35 to 40 hp with the single belt according to MCI then take away another 28 hp for road air another 7 hp for the alternator then add a auto transmission and power steering on the 8v71- 270hp doesn't leave much 

good luck

[kyle4501]

  Does the cooling system require a 60 HP fan, or is that simply how Cat designed the fan/engine? I note the MCI's have a belt driven fan up top, and there is no way that belt could transmit 60HP. I would be surprised if it pulls much more than 5 HP. And there would be a power loss because of belt and gear transmission. A couple large electric thermostatically controlled fans might be sufficient, CFM is the key. Whether you get it with 6 HP, or 60 HP, CFM through the radiator is the main factor.

Take a look at the charts, that 60HP was for an engine making 500HP.

MCI also had to limit the HP of the engine to avoid over heating.

Clifford is right, that belt can easilly transmit 40 HP.

[Ncbob]

Tom, I wouldn't take a Cat engine as a gift! And it's doubtful as to whether your Wanderlodge frame would be able to carry the weight of a 12V-71.

Why not look at the Series 60 Detroit? They've been proven in Prevosts for years.

Just my thinking.....

NCbob

[oldmansax]

Tom, I wouldn't take a Cat engine as a gift! And it's doubtful as to whether your Wanderlodge frame would be able to carry the weight of a 12V-71.

Why not look at the Series 60 Detroit? They've been proven in Prevosts for years.

Just my thinking.....

NCbob

Bob, I was just kidding about the 12V. I got enough problems to fix with the 'Bird  to last me a couple of years as it is now. I don't want to even THINK about an engine swap! I'll keep the 6V-92 for now.

That 12V would sound sweet with straight pipes though.............. 

TOM

[RoyJ]

Remember guys, the 60 hp is designed for the worst possible scenario: 110 degree weather, up steep hill, 1st gear, full troattle, possibly unlocked converter (huge heat dump from trans cooler), with full A/C.

In the MCI Renaissance literature, engineers stated that the fans are expected to operate at max rpm for 5% of the operation, while the other 95% in spent in the low power mode.

You also have to consider what coach is involved, instead of generalizing "electric fans don't work for buses". My bus, a 6V71 NA with Spicer 5 spd, represent the lowest heat load on the scale, while an 8V92TA automatic would represent the highest, possibly 3 times more.

My electric fans, which pulls 70 - 80 amps on 12V, does a fairly decent job. On 90 degree days, climbig 9% grades in 3rd @ 30 mph, I can get away (barely) without spraying.

[kyle4501]

It is that 5% of the operation while climbing long grades when I want/ need MORE POWER. 
- That is not the time I want to back off the throttle, that is the time I want more pedal travel & the radiator & fan to have more capacity.

BTW, I wouldn't exactly call a 80 to 90 amp load cheap either.
I'll say it straight out - I never said electric fans won't work. I have said that cheap electric fans won't. And, it ain't a simple task to replace the mechanical fan with an electric fan (while retaining the stock radiator) & get factory performance.

Another definition of a cheap electric fan is one that does not have performance curves showing the relationship between cfm & pressure drop.

Wether or not a system "works" depends on what level of performance you are willing to accept.
Personally, I don't like having insufficient cooling capacity that can lead to overheating of the engine during normal operating conditions - like driving up a grade at the right rpm.

So, yes, electric fans will work - if you can live with the 'minor' detail of reduced cooling. 

[RoyJ]

Kyle,

I don't disagree with you a single bit.

I should also clarify, while my electric fan setup may work for a hobby busnut, who genuinely has a passion for what he drives and therefore pays great attention to it, it will not work at all for the typical charter / linehaul driver.

A commercial setup needs to stand up to your typical commercial driver - who gets in, steps on it, and forgets 'bout it. A system that requires constant monitoring of EGT, water temp, boost level, etc., would be a failure in design.