Coach Cooling System Modification

[skipn]

Ok so now my curiosity is peaked.
1. When you lengthen the bus are you going to maintain the monico design or are you going with a modified monico with a beam structure?
         In the 70's we were used to adding a H frame to unibodies some times they didn't work out. No biggy for we weren't out a ton of money.
          we usually had more money in the engine than the cars we were putting them in.
2. Cooling efficiencies are gained by increased air flow, increased surface area, increased pressure, and/or increased volume. If you change the air flow
     what else are you willing to change? Increased pressure doesn't always increase efficiency.
3. It would take a very secure person to admit they have a 30k storage shed. Mine is only a 20k shed and I am trying to keep things as stock as I can.
     Another week or so and I might be road worthy again but until then realistically it is only my workshop and shed. ok so I lied about the 20k but I won't admit 30.

   I wish you luck.
  Skip

[Tim Strommen]

One of the wackos (kindred spirits?) is now present...

Don't do the electric fan.  Not worth it...  The hydraulic fan I attempted to replace with electric ended up going back in after only three months.  I spec'd out everything from the 15HP electric motor to the custom PWM controller (which I designed and built myself).  After about $4K in parts, it still didn't work as well as the original fan.  I found that some of the other modifications that I made in the course of swapping in the electric improved the over-all system performance - but had nothing to do with the electric motor...

The first thing I did to improve the cooling was to separate the transmission cooler from the radiator, giving it a separate intake, and a 24VDC fan that kicks on above 150 degrees (which is ducted out the back away from the engine radiator intake).

Then I added a high-temp "blow-off" above the engine access door in the rear, which has several louvers and three 24VDC pancake fans to blow out that high-heat pocket that builds in the engine space around my exhaust (this pops open and turns on at 200 deg F - as a good portion of the heat the block rejects is done directly out of the side of the block and the headers).  This is coupled with a deflector below the radiator which ensures the exhaust air from the radiator fan (which blows into the engine space) does not wrap hot air back around to the radiator intake (which would increase the ambient radiator temp and reduce it's effectiveness).  I also added a set of electrically actuated louvers to replace the stretch mesh grille on the radiator intake door, which open at 150 degrees and act like small wings (with incremental depth) thus re-directing passing air into the radiator opening (not a single giant scoop - I'm too afraid to cut down pedestrians with one of those ) they also keep the radiator warm in the winter if it's running cold by staying closed.

Finally, I have a few pieces of 1" L-channel welded to the side of the bus to break up the laminar air flow (air that aligns to the side of the bus as a high pressure-straigtened "surface") so that the radiator intake louvers had a better chance of pealing off some of the passing air.

What I ended up doing with the fan, was changing the way the valve worked.  The factory valve was a "dumb" thermostatic proportioning valve that couldn't be adjusted very finely.  I ended up putting a tach on the fan shaft, intake and outlet temperature sensors, and building a servo control for the proportioning valve so that I could re-program it (on the "fly" even if needed).  This coupled with my exhaust pyros, fuel flow/consumption sensors, and the instrument display software I wrote (for data fusion) - give me a better picture of how efficient my engine is running (or if I'm over-doing it...).  This is all on an '84 6V92TA MUI engine (no DDEC).


Try to remember that these older engines were planned as more of a system.  Newer Engineering methodology is to have discreet components doing individual jobs (so they can be individually tuned and accountable for specific design variables).  The task of adding any efficiency will be best served by looking at where some of the wastes are.  For example - do you need hot water?  Put in a heat exchanger so that you don't have to burn more fuel to heat a tank.  If you're not using all of the power the prime-mover is producing, flip on a secondary alternator to charge your house batteries.  By converting much of this "waste" into useful work - you are in fact (by definition) improving the over-all efficiency, and you may not need to modify the actual engine to do so.

With all due respect to current engineering practices (as I am an EE) - I believe a return to some of the "neat and tidy" Engineering of the 50's and 60's wouldn't hurt - too much.

Cheers!

-Tim

Edit #1: I though I should add - I've owned my bus for 3+ years already - and I've still done limited sawsalling.  It's basically a transit with a few minor adjustments so far.  I haven't had the balls to cut the window rails yet as I've looked deeper and deeper into the construction and have found basic structural things I wanted to change first (I found in the Gillig Phantoms, that the wall-base to frame connection is the biggest weakpoint...).  Oh and I'm 27 years old now, so I've given myself some time to finish this project  -Tim

Edit #2: I forgot to mention, I kept the old Carrier heater core as a secondary radiator.  The concern was driving it through hot/arid locations (I'm in CA and I wan't to go to Las Vegas - right by the Mohave desert...).  My feeling is that If I can't cool the rig down with almost 1/3 more heat-exchanger surface area and twice the air flow - I should park it until sunset...  -Tim

[WorkingOnWise]

Ok, now we're talkin prozac!
skipn-
1) I intend on doing a modified monoque -  box rail lower, monoqueish roof section, slides in between. The box rail section will basically go from just aft of the front tires to just fore of the rear wheels, and will not be so rigid as to be able to support the ends on it's own. The help will come from the roof rails and skin (the monoque-ish part) The model and simulations will decide the details.
2)Actually, the efficiency I am after is engine efficiency. The reason for the added pressure is to allow higher temp without the steam pockets, to help avoid the cascading meltdown that happens with a low pressure system that overheats. That way, I can run at 200f normal temp, and if the temp rides to 220, while not good, is not a death sentence either. The operating temp increase is the goal, without  adding any problems.
The desire to loose the fan/clutch assembly is for weight distribution reasons. Weight is more harmful to vehicle dynamics in some places more that others.
3)20k shed huh? Cool. If it isn't on the frame rails, it don't count, sorry! lol  =)

Tim Strommen- You did this high tech work on a transit? I'd love to see some pics, maybe schematics too, of your work. Sounds like something I want to look into.
Your cooling system mods sound like a perfect example of what I said earlier- these engineered did great with what they had...we have better now.

I have entertained the idea of fitting an engine management system from a 1996 or newer v6 gas car to the engine, as a way of monitoring the engine/trans and related systems. Then I could plug in my modis into it ans see exactly whats going on. It would have no control capabilities, so if there were a sensor failure, I'd get a code, but not effect on the vehicle. I'd just have to learn what codes to ignore (O2, Torque converter, etc) and which to heed.
The old-timer engineers had the right methods and practices, we just have better information to draw from now.

[Tim Strommen]

I'll have to dig the bus out of winter storage...

I think I still have board layouts and schematics...  I'll see about posting those to this thread.  As for the 1996 ECU - it's easier/cheaper to build an application specific one from scratch these days.  I'm about ready to do the final revision on the controller for my rig which has the anti-theft stuff built in and the new engine supervisory and maintenance monitor logic (got rid of about 200lbs of control/instrumentation wires going between the front an rear - replaced them with one Cat-5 UTP cable with serial RS-485 signalling).  This system will also tie into the interior energy management system and climate control I'm building, along with the DC power plant (which has a couple refridgeration compressors and an aux-air compressor to maximize the system efficiency).

Many will say it's too complex, but I think that's why I'm doing it (it's a mental excersise AND a hobby ).

Cheers!

-Tim


P.S. My bus is a mass-transit, El-Cheapo, cookie-cutter... (your moniker here...) - rig.  I think they did what fit the design price-point for the majority of their intended customer base on that model (super customization is really expensive and not something that most transit districts will pay to do - that's more "limo" like what we do ). Something to keep in mind is that I've taken my bus out of its original design envelope - so some modifications are required to retain its original reliability.  This doesn't however suggest that the changes I've made are any different that what was available in the "old days" or that previous Engineers hadn't implemented them somewhere else, just that for my model, make, and year - my bus didn't have them as part of the design. -Tim

[WorkingOnWise]

That would be great if you could post that stuff Tim. Thanks
As for the ECU, I can get a donor car for dirt and have all the electronics and connectors, and most of the wiring. I don't have to design the communications bus, data conversions, sensor interfaces, nothing. And I already own the data interface tools, so the cost and effort are quite low. But, if you don't already own the scanner and tools to service the specialized electronics, yes, it would be tons easier to design a stand-alone system. I may still, but if I don't want to think that hard, I can fall back to the '96 ecu plan. The thing that has me going back to that is the ability to detect misfires. it took GM 4 years to be able to do it fairly accurately, and Chrysler 3 years, but it is very useful now. To re-invent that ability, and eliminate the false positives from vibration....not so easy, I imagine.

[Tim Strommen]

Hmm...

     Most of the older (OBDI/II based) misfire detection was based on a gear tooth magnetic pickup signal being compared to time.  If there was an expected firing, the gear tooths would accelerate as they pass the sensor under the combustion stage and frequency would increase - if the cylinder mis-fired, it would result in a minor deceleration (frequency would decrease) for that stage.  A few occurences of the deceleration at one cylinder's expected time would trigger the misfire flag.  Several, on different cylinders would set the misfire flag with a distributor or coil service notice.  This is just as simple to do now as a stand-alone processor task with a cheap sensor that'll probably be there already for the tach.
     The new-fangled way to detect the combustion quality and sucess is to have a slightly capacitive spark plug, and after the initial spark shot is fired into the plug - a lower (but still high) voltage is placed on the wire and a field impeadance measurement is taken (this allows the O2 content for the specific cylinder to be read before it opens the exhaust valve {or valves}).  With a certain impeadance, it can tell a mis-fire occured (before the engine would have slowed down).  An added side bonus is that a fast microprocessor can adjust its PID algorithm and LUT to account for the O2 content (and thus the burn efficiency, by adjusting the PWM duty cycle for the injector {fuel-shot volume} and the timing advance for the next spark plug {duration of power stroke}) in near real time - providing better RPM/Power transient response (in other words the gas pedal feels more responsive).

     Of course, with an o'l 2-stroke there's no need to get any more complicated than an OBD-I git'up.  There is no timing adjustment to be had, and without electronic injectors and variable valve timing there's no timing to control.  With a pyrometer, you can read the load on the engine, and with a high precision tooth sensor as a tach with a simple firing order table/counter, you can figure out which cylinder/injector is not tuned properly - or if you have an injector failure (no-fuel or stuck wide open).  And we're not watching O2, as our rigs are (for now) emmissions unrestricted.


There are some other interesting things to watch while your engine is running that OBD-I doesn't pay attention to though:

• Tach
• Fuel Control Position
• Air Intake Temperature (this can indicate possible need to reduce power demand)
• Air Intake Vacuum (before turbo if equiped - can indicate air filter restriction requiring service)
• Turbo Boost (if turbo equiped - interesting to watch in high altitudes)
• Air Temperature after the Turbo ("charge air" if turbo equiped- this can indicate possible need to reduce power demand)
• Exhaust Temp (one for each side if a V-Engine, combined with tach and fuel control sensor - one can derrive "lugging" condition and can indicate possible need to reduce power demand)
• Head Temperature
• Engine Compartment Temperature
• Radiator Air Intake Temperature
• Radiator Inlet Temperature
• Radiator Output Temperature (difference between this and other above readings can be used to determine BTUs rejected, and cooling efficiency)
• Fuel Pump Inlet GPH
• Fuel-Rail Outlet GPH (difference between this and above can be used to derrive your consumption GPH and with speed your actual MPG - and with Exh. Temp, can determine operation efficiency)
• Oil Presure

These variables, combined with the appropriate math (and presentation) can speak volumes about the health of an engine or the way it's being used .

Cheers!

-Tim

[RJ]

Keith -

Back to the original thread topic. . . but first, an introduction to my background:

I spent 25+ years in the bus industry, the first 10 pounding the pavement to the tune of 80K/mi/year, the latter in Operations Management and Training.  I don't have an engineering background, other than turning a wrench on Corvairs as a hobby. I was a business major in college, back when the computer science guys were still writing programs using punch cards (and I drove a skoolie to pay for skool, too!).  I've been sharing my real-world industry experience with others in the busnut community for the last 10 years or so, as well as gaining a lot of good insight from others who also have been willing to share (many of whom are sorely missed since they are no longer posting).

In all my years behind the wheel, I never had a coach overheat on me, and that included running in the Mojave Desert in the summertime with MCIs, which are notorious for overheating.  I'm in CA, and from where I live, whether I go N, S, E or W, I have to climb 6% grades to get out of the Central Valley.  So, based on my real-world experience, here are some of my thoughts for you to ponder, as well as a very important trick to keeping it cool:

I've read your comments about engineering "then and now", and do not disagree with you.  However, I'd like you to consider some of the design criteria that the factory was dealing with, which was (and is) considerably different than that of the guys building cars.  Building a commercial vehicle, one who's purpose is to generate income for it's owner (yes, even if it's a government-subsidized transit agency) means designing the entire vehicle to minimize down-time.  Transit buses especially are ridden hard and put away wet, and still survive.  Everything from the door operation, the floor-mounted turn signal switches, the brakes, suspension, steering, and powertrain are all engineered with reliability and ease of servicing in mind.  Nowdays, compared to your Fish, this includes meeting all the government mandates that didn't exist previously.  But the overall concept is still valid.  Nobody likes to get a call that "there's a bus broken down on 41st Ave blocking the intersection", especially during morning/afternoon rush.  So keep the reliability and ease-of-service in mind as you progress with your project.

GM offered the cooling system on the Fishbowls two ways - direct drive, and the torus drive (looks like a big torque converter between the block and the fan).  Direct drive is obvious - the fan runs all the time.  The torus drive acts conceptually like the viscous clutch on a 327 Chevy's fan - the fan freewheels until the engine reaches a certain temperature, then locks up to increase the cooling capacity.  Whoever bought the coach initially had the option of choosing which one they wanted, both worked, and worked well.

Radiator sizing varied depending on what powertrain was installed in the coach.  Fish with 6V71s used a slightly smaller capacity radiator than those who's buyer checked the box for the 8V71 engine.  The radiator on my 8V71-powered 1964 PD4106 is huge compared to my friend's 1960 PD4104 with a stock 6-71 in it.  His coach has a direct drive fan, mine's got a torus drive.  My fan is also considerably larger than his, and is more tightly shrouded.  As Tom pointed out, that big fan on a 4106 draws upwards of 25 hp when locked up - and if you stand close to the radiator with the engine running at 2100 rpm and the fan engaged, it's really hard to not get sucked up against the side of the coach - those fans draw a HUGE amount of air at speed.  As others have found out, matching OEM with aftermarket electric is a fruitless pursuit.  (Side note:  Some of the late-model Prevosts with the 500 hp 8V92TAs stuffed in their tails have hydraulically-driven fans that draw in the neighborhood of 40+ hp!).

System maintenance is a critical element that is often overlooked.  Not only the condition of the components, but also the chemistry of the coolant itself.  Are you aware of the phenomena known as "coolant cavitation" in a diesel?  Detroit's got very specific guidelines for the coolant chemistry for the two-stroke, just like they have very specific requirements for the type of engine oil to be used (that's a whole different thread!!), in order to help control this phenomena.  This cavitation, if not controlled, can actually lead to cylinder wall failure in the most extreme cases.  This isn't just a matter of mixing anti-freeze and water in the right proportion, it also includes the type of anti-freeze used and a couple of other things that escape my memory at the moment.  Test strips to check the chemistry are available at your local Detroit dealer.

Most automatic transmission-equipped coaches come with a transmission oil cooler.  For 99% of the time, the OEM design is adequate for the application.  It's that odd 1% that can bite you, and it's usually in conditions where the coach is being used for something other than it's original design.  (That means us, you know. . .)  Jack Conrad came up with a good idea that works well for his coach, and is applicable to others:  He uses an additional cooler mounted on the curbside access door, that's tied into the transmission coolant lines.  Not uncommon.  But what he did differently was to tie it back in in such a way that if it cools the oil too much, it's routed back thru the OEM cooler, in order to maintain the transmission oil in the same range as the engine's coolant temp.  Perhaps Jack can jump into this thread and explain it in a little more detail.

(Slight detour here:  The VS-2 in your coach has three modes: hydraulic, 1st gear, 2nd gear.  Starts in hydraulic, then locks into 1st at around 25 mph, then into 2nd at about 35/40 mph, so it feels like a three-speed even tho it isn't.  But that also explains why it will hardly climb a 4" curb from a dead stop - and you'll rapidly heat the transmission oil as you try - because there is no actual mechanical connection between engine/transmission until it locks up into 1st.)

But IMHE, it's been the weight of the driver's right foot that creates the biggest cooling problems.  That, coupled with inattention and a "gotta get there" mentality, has probably fried more engines than all of the above combined.

The real trick to keeping a Detroit two-stroke cool in most conditions is to keep it in the "sweet spot" of the power band, i.e. 1800 - 1900rpm on a partial throttle.  You should be able to step further on the throttle and still accelerate w/o a lot of black smoke.  As long as the coach will maintain speed or slightly accelerate while climbing in this rpm range, most coaches with cooling systems in good condition will not overheat.  BTDT.

As soon as the coach will not maintain speed, or starts to smoke heavily when trying to accelerate from the sweet spot, it's time to grab the next lower gear and get back into the above rpm range.  This is very easy to do with a stick-shift, or a late-model Allison, but virtually impossible with your VS-2.  BTDT, again.

Be aware that heavy black smoke is going to be a problem with any non-turbocharged Detroit when you get up into the higher altitudes (above 5000 ft), and therefore requires even more concentration on what you're doing.

Droopy eyelids preclude me from continuing at this point, but hopefully this post has been informative.

Start another thread on weight distribution, and I'll share some more real-world experience related to that with you.

FWIW & HTH. . .




PS:  What's the VIN on your Fishbowl?

[Sojourner]

Tim & Keith....you guys bring back memories while I was working in GM Engineer Staff in APE division in Warren, Mi. That was my dream to work in the "wonderland of experimenting" place. Am now retired since 96, would love (if you will) to learn your data report whenever it available. I am too going to increase cooling system pressure as long the DD 2-cycle water pump allowed as far as wear & tear on seal. Later the Lord willing...going to switch to 60 series DD with World Trans. It already lengthens to accommodate longer engine.
It a MCI-8 (102x43.5) with a large radiator opening on the left lower side. In a few weeks I will be installing a radiator with A/A cooler. So if you don't mind, keep me or the MAK board informs what works better or doesn't. I am at least a year to go in project before I can get any reasonable data can be taken such as air flow of side, rear end turbulent and heat study.

PS...done under hood heat study to reduce heat damage on battery, plastic and improve a/c's condenser air exhaust flow. Rework radiator concept design from the normal. All kind of hose & clamp testing. To name a few during my life time.

FWIW

I'm 69 slow but ready to be with the Lord with new eternal body. Praise the Lord!

Sojourn for Christ, Jerry

[JackConrad]

Jack Conrad came up with a good idea that works well for his coach, and is applicable to others:  He uses an additional cooler mounted on the curbside access door, that's tied into the transmission coolant lines.  Not uncommon.  But what he did differently was to tie it back in in such a way that if it cools the oil too much, it's routed back thru the OEM cooler, in order to maintain the transmission oil in the same range as the engine's coolant temp.  Perhaps Jack can jump into this thread and explain it in a little more detail.

    When I installed the Hayden cooler and 3000 CFM fan on the passenger side engine compartment door, we ran all new transmission hoses (OEMs were getting questionable). The transmission cooler output goes to the top of the added cooler, exits the bottom of this cooler, goes to the OEM (engine mounted) cooler and then back to the transmission. This allows engine heat to help warm the transmission fluid when bus is first started. I do not know how much heat is actually removed by the aux. cooler, but IF the fluid leaving the aux cooler is cooler than the engine mounted cooler, it will extract heat from the engine to bring the trans temp to engine temp. Any heat removed by the aux. cooler is that much heat that does not have to be removed by the radiators. Since doing this all temperatures (water, oil, & transmission) run about 10-15 degrees cooler.  This is without even turning on the 3000 CFM fan. So far we have found that we get an adequate air flow created by the squirrel cage blowers and natural air flow.
    Another thing we added that we really like is a pyrometer. I was amazed at how fast this gives an indication of engine heat. When climbing a hill, I watch the pyrometer.  as the pyrometer starts to climb, I downshift, and watch the pyrometer drop back. All this happens almost as fast as I am writing this. All right, I type slow with 2 fingers, but it still happens pretty quick.  Jack

[kyle4501]

WorkingOnWise, you dodged the question concerning your background, experience, & abilities. Before you diss someone's background, share your own. This info will help us to answer your questions more completely.

Some of your comments & questions have me a bit confused as to your basic understanding of engineering. It seems to me that your planning & research is not as far along as you thought.

Where is Clarke? He can definately share some info on the custom engineering issues.

I still think you will be time & money ahead by getting a better starting point, but this is comming from someone with four PD4501's. (If anyone cares, I have a BSME & design OEM machinery in a machining & fabricating shop.)

Oh, another 2 cents worth:
Being a newbie to the board & dissing someone or their bus is not the best way to get information here.

[WorkingOnWise]

Jack- Thanks for the detail. The trans cooling mods are great! With auto trans service being my absolute least favorite thing to do, it's important to make it live long, and only need fluid, filters, and an occasional external adjustment!

I would not have considered a pyrometer to be useful on a non-turbo engine. I have one, so I'll have to give it a try.

Sojourner- You worked in Warren huh? Cool. I lived in Macomb County most of my life.
The data you are talking about, do you mean the crash simulation data? I'll share everything we find on the board.
I never considered the water pump being a potential limitation to raising the system pressure. Anyone know about that? Is the same waterpump used in a high pressure system?

Kyle4501
Yes, I did dodge the question. I felt the question was more of a dis than an inquiry intended to help anyone to answer my questions more completely, and I responded to him, and only him, in the way I saw fit.

There are things I know, and I know them well. There are things I don't know, and I will gladly state them. I will ask, even if it is a question that I probably should know the answer to.
Thanks
Keith

[RJ]

Keith -

Since it was rather late when I wrote my missive, I forgot to mention an important part of the GM cooling system.

Look under your coach.  Do you have a full-width mudflap across the coach behind the rear axle?  If not, then you need to install one.  OEM was in three pieces, I have the specifications for each piece if you need it.

If you have one hanging off the back bumper, you need to take it off.

Why?

Because that full-width mudflap creates a low pressure area under the engine compartment, helping to draw hot air out while running down the road.  Simple and very effective.  OTOH, hang one off the rear bumper, and you trap the hot air right where you don't want it.

Crown and Gillig used this same trick with their midship-mounted powerplants, except they hung the full-width flap right behind the front axle.

FWIW & HTH. . .

[tekebird]

I've got the answer (s)

A remote front mounted radiator.......nope that would put weight forward of the front axle effecting handling

a roof mounted radiator.....nope that would raise the CG also screwing with the handling

AHHH..........a midship mounted radiator.....with a ducted roof scoop and a bank of squirel cage fans.........set it up similar to the MCI system which shuts off the airflow of the cage fans ( a squirel cage fan that is not moving air draws practically no power)

[RJ]

Doug -

Your sense of humor's showing again!   

[tekebird]

some people just bring it out......LOL