I had time this AM so I did the write up on what I have recently done to try to reduce the engine temperatures when I am running at high outside ambient and higher elevations.

I know, I know, slow down Ed--can't--

So here is what I did, I will know if there was any improvement next week during my travel to virginia City NV and then further to Wendover NV (Bonneville)

This is a fairly big .PDF file so dialups beware!

Air flow improvement

they have an additive to add to your antifreeze its at most parts stores . cant rember the name but its used alot in race cars might be a simpler fix..

I think you are referring to "water wetter". Tried it, doesn't make any difference.

One of the main reasons they use it in race cars is that if they get into an altercation with another car or wall, getting antifreeze on the race track it very bad news, track will absorb it and remain slippery for a long time.

Water and antifreeze mixture or water +"water wetter" cools better then water alone.

Ed, great .pdf. Have you considered an auxiliary radiator placed in one of the grilles? I would think a large heater core or oil cooler tapped into the heater hoses could move more heat...

BTW, I was having some overly warm temps, fixed by the new transmission (and expecially the TC). I mention this only because if your tranny is cooled by the radiator (mine is), a supplemental cooler mighht help. Ith tranny place thought an auxiliary cooler might be in order, but coming back from GA in 102° temps, the tranny stayed at its normal 160°. The Mag Hy-Tec pan does contribute significantly to tranny cooling (~15-20°)

Thanks Rusty!

Yes I have toyed with the idea of tapping into the heater line at the front with a radiator. I have several of these heater core radiators that were used in school busses and are quite large. I may do this after this trial if what I have done so far is ineffective. I already have the thermostat/bypass built up for the heater lines so that the temperature would be regulated and I wouldn't over cool the engine thru the heater system.

My trans has a separate cooler from the radiator although it is ahead of the radiator. The radiator package from the fan is:
1. turbo intercooler
2. Allison trans cooler
3. radiator

So the water radiator does see preheated air from the other coolers except the bottom 1/3 where the other coolers do not cover it.

One of the reasons that the airflow thru the radiator is so high at the bottom of the package is because the turbo intercooler and the trans cooler so not cover the entire water radiator so the bottom has a much better air flow. That is one of the reasons I have concentrated on that area, I can't change the other areas.

I also have a turbo blanket coming that will wrap around the turbo hot section, that will go a long way to reduce the heat pickup as the air passes thru the engine compartment. I will have that on for the next rip in late July. The exhaust wrap really help a lot.

Is it possible that the rear radiator design is inherently flawed due to changing aerodynamics when at speed? Although you can see air flow when static, does a vacuum occur that pushes back at the radiator reducing flow the faster you go? Might this be one of the reasons side radiators came into play on pushers?

Two things make me think this is a possibility.

1) Being a motorcyclist I have experienced the dead air space behind DP RVs (sometimes on purpose to stay warm). It's much better than a tractor trailer because it is lower to the road surface and is creating warm air on pushers. If you get close enough, there is a warm dead air pocket back there that can make you feel like your not even moving as you tool along at 70MPH.

2) I owned an MCI bus which had the notoriously hot DD 2 stroke. They had an ingenious cooling system that pulled air from the top side area down over the top of the motor and out the bottom. They use bird-cage fans to guarantee air displacement. The rear of the coach has NO air exit even though it easily could. In fact, the solid doors were sealed.

I realize there is no easy fix if I were correct, but if your actually thinking of putting a radiator up front, might you look into what a relocation to the side would look like? Could it be as easy as turning the fans around to blow in?

I'm just theorizing, of course. It sounds like Rusty has found a solution, but I wonder if you average higher speeds which would compound the issue of heat and the vacuum effect if I were correct.

What kind of shape is your radiator in? Might just need a good flushing or it might need to be rodded out. Worst case it might need to be replaced.

You might also want to put in new thermostats first and see if that makes any difference.

The radiator is new, the thermostat is new and I have tried various designs of "high flow" stats, nothing changes.Water pump is new. All hoses in the cooling system are new.

There is a theory that the high vacuum behind the coach will draw the air or promote air flow thru the rear radiator, while I generally agree that this is possible, I have seen all kinds of turbulence in the back up camera when I did the tuft test while driving. Airflow is OK according to the way the tufts show BUT, I have no way of knowing what is happening under the coach and the lower part of the radiator that I am addressing with this change.

I think the side mounted radiators are more of a maintenance convenience (I would love to be able to get at the front of the engine--) then cooling improvement, but obviously, cool air drawn in from the outside would be better then blowing air from a hot engine compartment.

I have looked at side mounting 1 or 2 (1 on each side) and it would be a major chassis cut up. The proposed radiator up front would be a small one designed for interior heating and be easy to plumb in. It must be thermostatically controlled to go in and out of the cooling circuit. As mentioned, that is already built but I am doing 1-2 things at a time to keep it simple and easy to say what works and what doesn't.

Hey Ed, How about adding an engine oil cooler.
Bennie Burgman (not sure on spelling) used to advertise in "hot vw's" and oil cooler system for the air cools. He had a oil cooler with elctric fan and thermostat. This set-up could be placed to draw cool outside air to cool your oil and help your water system.

Just an idea,
Scotty

Do you remember these old Flxible buses? Not a bad idea to keep from running 50+ feet of hose. Would work with oil or coolant too.

Do you have mud flaps behind your rear wheels? On the bus boards people have talked about the airflow under the buses and how mudflaps help and how a solid full width flap under the bumper may actually impede air flow.

Have a good report about my rear mod around the radiator!

On I80 flat, 95 degrees,75 MPH, 190 was as high as I saw on the engine temp gauge. I have never been able to drive that same stretch of road in temperatures over 90 at speeds above 65 without going to 200(@70 MPH) -220(@75 MPH), At low speeds the improvement was less dramatic and that kinda confirms the air turbulence theory around the bumper/radiator area.

I completed the entire 2000 mile trip and the engine temperature never went above 200 degrees, one time was on a long climb on I50 between Carson City and Lake Tahoe outside ambient 97 degrees, speed 45 MPH but had to throttle back because of EGT limits.

I will add more metal under the engine to improve the airflow toward the rear of the coach later.

I now can drive using only the EGT as a limiting factor in my driving speeds. Engine cooling has little effect on that.

My rig used to run hot 220 on hills in warm weather. I cleaned the radiator inside and out with simple green and a power washer and now runs 170 to 190. sometimes it gets to 200 on really long hills pulling the trailer, but I drive with my foot in it all the time. The EGT is the only thing limiting me now... maybe intake and exhaust will help this. I think the stock airbox/filter is too restrictive also. I've toyed with the idea of putting a 6000cfm electric cooling fan behind the radiator and remove the engine mounted fan altogether so when my intake/exhaust mods lower my egt temp I won't be limited by water temp. what do you think?

quote:

Originally posted by apoccia:
I cleaned the radiator inside and out with simple green and a power washer...

NEVER use a POWER WASHER on your radiator. Use a garden hose instead, radiators are very expensive when you blow one apart from using a pressure washer.

Consider yourself very lucky apoccia