A rare Liberty

[johnklopp]

You have a dual evaporator where are they located?

I have one evaporator in the dash and a second one in the bedroom. Keeps the bedroom area and the driver cool any time im driving.

[jack14r]

Liberty uses Cruise Airs,I understand that Frank figured out the problem with the CA condenser air flow and they now work at speed like they should.I heard that there was a vacuum created under the coach at speed and the condensing unit had very little airflow at speed,Liberty re-directed air and they got the CA to perform as it should.

[Denny]

Prevost has an upgrade for the dash air available that gives about a 50 percent increase in cooling capacity. It is a big improvement over the stock setup.

[gmcbuffalo]

Denny More info please

I wonder if a scoop was placed on the air intake to the CA unit to increase airflow into the CA while driving. One like you see on the the old MCI and GMC buses for the engine radiators. I know the exhaust hole is scooped, only to direct flow away from the intake.

The other thing and John mentioned it, is the air exhaust hole in the floor is only about a 6x6 inch area.
John what would should the optimal size of this hole be? I think I have a large intake hole but a small exhaust hole.

[jack14r]

The exhaust hole is the size of the blower exhaust,so it is as large as it needs to be.

[Denny]

Greg, the upgrade is a new system that replaces all the components. The compressor, evaporator, expansion valves, etc are all replaced. As I understand it, the original system is designed for commercial trucks which have a smaller area to cool than a bus. Therefore, on a bus the system is working overtime and wears out faster. The new compressor is replaced with a larger, heavy duty one along with all downline components. The increase goes from a 2 ton system to a 3 ton system.

[johnklopp]

Generally you want the intake and exhaust duct work to have a large cross section with a short length. Longer duct work or a smaller cross section will increases the air velocity and the pressure drop in the duct work reducing air flow.

The discharge air will be on the bottom of the coach and the blower discharge will probably be just the blower scroll passing through the bottom of the enclosure. A deflector may be used to turn the discharge air away from the patio area as well as the intake air location.

If the coach is not moving, no scoops etc. should be needed to pick up the intake air. If the coach is moving, care must be used to select the location of the intake. The coach will likely have a boundary layer present when moving that may be in a negative pressure condition creating a reduction in air flow across the condenser. The only way to optimize the intake location would be instrumentation with a magnehelic gauge to measure the air pressure at the intake location.

[Jon Wehrenberg]

I cannot speak for all Libertys or other conversion but on my coach I have a crosswise baffle beneath the coach separating the air intake from the condenser air discharge. That baffle extends almost to the ground. It's first function is I presume to separate intake air from discharge air (which is directed away from the baffle) so when at rest the CAs are not recirculating air through the condenser.

The benefit of the baffle when moving appears to be that in front of it I suspect is an area of high pressure which is a huge benefit for intake air, and directly behind it in the area of the discharge baffles is a low pressure area so it appears to supplement the work of the squirrel cage fan.

I wonder why the same concept is not employed with a transverse full height flap behind the tag axle wheels to create a low pressure area to assist flow through the engines radiator. All converters put a full width flap across behind the engine under the rear bumper which just seems counter intuitive. I removed that flap on both my buses as soon as I got them.

[JIM CHALOUPKA]

Who will be the first to buy a magnehelic gauge?

Spell check didn't like that word.

JIM

[Jon Wehrenberg]

We ain't that sophisticated. I propose we attach short lengths of yarn and then watch the air flow based on how the yarnreacts to air flow.

We probably will need ear muffs however because the person we strap beneath the bus to watch the yarn and report on the air flow is likely to be screaming. Especially when we get the bus up to highway speeds.