Some years ago I was involved in research of 2 stroke diesels and a lot of my work involved digging into the stuff that Detroit did. I also talked to a lot of former engineers involved in that era. I dug up the culmination of my work and summarised it into palatable chunks for those who are interested in this forum.
Along with technical conversations- the source of my work predominantly comes from the following SAE papers:
740037-8v92
881584
770255
870402
831202
It seems that the 92 series is an evolution of the 71 but the 'phase in' of the 8v92 was slow and not absolute.
The 8v92 uses wet liner configuration above the intake port compared to the 8v71. I don't usually like wet liners for boosted application and I have hear the earlier green 92 engines suffered from electrolytic corrosion problems- but that's probably also connected to inproper use or/changing of coolant etc.
Elimination of upper water jacket coring simplified the casting
While the water jacket cores surrounding lower cylinder bores are somewhat smaller in the 92 series
(https://busconversionmagazine.com/forum/proxy.php?request=http%3A%2F%2Fi273.photobucket.com%2Falbums%2Fjj229%2FMarquisRex%2F8v71%2520vs%25208v92%2520block_zpsfr9jgkfg.png&hash=9450c0709fd6f0a9145d12456e81c4f9bc0a7834) (http://s273.photobucket.com/user/MarquisRex/media/8v71%20vs%208v92%20block_zpsfr9jgkfg.png.html)
The Cylinder bore centres kept the same on the 71 series vs the 92, as were head bolt locations but fasteners increased from 5/8-11 to 11/16-11 for increased clamp load.
Struts that carry head bolt loading directly to main bearing bulk heads have proven 'entirely adequate (their words- sounds more like how Bentley or Rolls Royce would describe it)' at very high engine loading a comparable structure used for 92 series
Early prototype 92 series using the old style 5/8-11 bolts exhibited cap to block fretting and ultimately web cracking at the bolt holes. This is why the 92 series utilizes 1.12 inch wider caps, 11/16-11 bolts and stamped cap to pan stabilized plates.
I know from experience that clamp loads for fasteners are derived considering the peak cylinder pressure loading of the engine. That's what makes me slightly nervous about the 8v71 Turbo series- however a coach/RV application is probably not under very much load/duty cycle compared to HD trucks.
(https://busconversionmagazine.com/forum/proxy.php?request=http%3A%2F%2Fi273.photobucket.com%2Falbums%2Fjj229%2FMarquisRex%2F8v92TA%2520vs%252012V71_zps5hf00g1k.png&hash=e3c45b25f9845a9d2bcb3d6e54ffd91a6d7cd92e) (http://s273.photobucket.com/user/MarquisRex/media/8v92TA%20vs%2012V71_zps5hf00g1k.png.html)
(https://busconversionmagazine.com/forum/proxy.php?request=http%3A%2F%2Fi273.photobucket.com%2Falbums%2Fjj229%2FMarquisRex%2F6v92%2520vs%25208v71_zpsixqfgpzi.png&hash=de37fabbf7debd3bb634aab9096faf652a754794) (http://s273.photobucket.com/user/MarquisRex/media/6v92%20vs%208v71_zpsixqfgpzi.png.html)
The 92 series has provision for an air to water heat exchanger-directly below the roots blower where the investment in tooling would have been too much for this on an 8v71 Turbo before- cooler effectiveness increased and quoted in the order of 70%.
92 series head design changes:
Valve head diameter of 1.38 inches. Cored water passage between traverse exhaust valves increased but stiffness also increased. Overall much less restriction over the exhaust posts AND intake port windows- this means less supercharger/blower gearing is required thus lowering parasitics
(https://busconversionmagazine.com/forum/proxy.php?request=http%3A%2F%2Fi273.photobucket.com%2Falbums%2Fjj229%2FMarquisRex%2FExh%2520ports_zpshp7zphzt.png&hash=e915c8e3b3eb720675bce70d3371a180a14a7445) (http://s273.photobucket.com/user/MarquisRex/media/Exh%20ports_zpshp7zphzt.png.html)
Crosshead vs Trunk pistons:
The 92 series utlises the later Crosshead piston design unlike my earlier trunk piston design of my 1964 71 series- this has proven much more robust- and we tested the two types of design in the labs back to back when I worked in San diego.
Better lubrication:
The V92 con rods incorporate a y drilled oil passage to supply piston cooling oil (to eliminate bearing shell steel fatigure failures which occurred) . Rods are good up to 4000 rpm testing- although this was under no gas load (even though the exh valves probably aren't!)
(https://busconversionmagazine.com/forum/proxy.php?request=http%3A%2F%2Fi273.photobucket.com%2Falbums%2Fjj229%2FMarquisRex%2FBearing%2520oil%2520supply_zpsdlebwsil.png&hash=1bffe0cb838c1c5de63d0f742380cf04fbd98a76) (http://s273.photobucket.com/user/MarquisRex/media/Bearing%20oil%20supply_zpsdlebwsil.png.html)
Above picture shows oil flow to piston 92 series vs 71
(https://busconversionmagazine.com/forum/proxy.php?request=http%3A%2F%2Fi273.photobucket.com%2Falbums%2Fjj229%2FMarquisRex%2FMain%2520bearing%2520shells-%2520upper%2520grooved%252071%2520vs%252092_zpskrcq4omf.png&hash=b1d4938b9a3885672a880381fe4734e5934bd076) (http://s273.photobucket.com/user/MarquisRex/media/Main%20bearing%20shells-%20upper%20grooved%2071%20vs%2092_zpskrcq4omf.png.html)
The upper main shell beariings on the 92 series are designed for better oil supply vs the earlier variants also.
There are other myriad improvements I haven't covered.
If I were to make more improvements with the benefit of hindsight and experience of modern engines- I would focus on combustion improvements- the BSFC or efficiency numbers are pitiful- and when I see numbers quoted of needing 32:1 air fuel ratio - I can see why, with the opposed piston 2 stroke I was involved in - we could get that number right down to 18:1. This would allow the supercharger blower ratio to be lowered even more thus lowering the parasitics further. I would also increase the injection pressure- both the 71 and 92 series only has a pressure of about 200 bar. The benefits of higher pressure aren't only emissions but also significantly on efficiency.
Then I would focus on the rootes type blower itself- the older style would get efficiency numbers of around 50-55%, where as the newer TVS style blowers attain 60-70% using bradable coatings to tighter tolerences and using a four lobe rotor design with 160 degree twist. I have experience of these design when we upgraded from the M112 super chargers on the old Jaguar XJRs to the later XF cars.
This is too cool Dread...thanks!
I'm certainly going to leave the technical details to those of you more technical than I, but I am curious about something.
As most of you know, I have 8V71N. When dad (who was responsible for a large fleet of heavy equipment, buses, police cars etc.) ordered my current engine/transmission in 2000 he could have ordered anything, literally. He was not restricted by funding.
My specific engine is "customer specified", and I am learning what I can about those specifics. This type of information is very helpful.
Here is what I don't get, and I am being literal, no embellishing I have also driven a few much newer buses with 4 strokes:
For all the various discussion of HP and Torque (the latter in my mind, for some reason, as being more important on the bus), I accelerate quickly when necessary; climb mountains; pass the trucks, some cars and on the flats, I have been well over 85MPH several times. I have never come close to overheating. I have never seen any smoke whatsoever. When not torn apart, she's NOT light weight.
I do need to lube up the throttle, as it's heavy enough to kill my leg on long trips with mountains.
But how is this possible? Other than the injectors and the governor, where would the most efficient modifications be made so that an 8V71N performs like it's not an 8V71N?
Quote from: daddysgirl on June 24, 2017, 11:49:06 AM
This is too cool Dread...thanks!
I'm certainly going to leave the technical details to those of you more technical than I, but I am curious about something.
As most of you know, I have 8V71N. When dad (who was responsible for a large fleet of heavy equipment, buses, police cars etc.) ordered my current engine/transmission in 2000 he could have ordered anything, literally. He was not restricted by funding.
My specific engine is "customer specified", and I am learning what I can about those specifics. This type of information is very helpful.
Here is what I don't get, and I am being literal, no embellishing I have also driven a few much newer buses with 4 strokes:
For all the various discussion of HP and Torque (the latter in my mind, for some reason, as being more important on the bus), I accelerate quickly when necessary; climb mountains; pass the trucks, some cars and on the flats, I have been well over 85MPH several times. I have never come close to overheating. I have never seen any smoke whatsoever. When not torn apart, she's NOT light weight.
I do need to lube up the throttle, as it's heavy enough to kill my leg on long trips with mountains.
But how is this possible? Other than the injectors and the governor, where would the most efficient modifications be made so that an 8V71N performs like it's not an 8V71N?
Andrea, to get more power/torque out of a diesel you need air and fuel. The air in the case of our Naturally aspirated engines come from the blower or supercharger and the fuel from upgraded injectors.
On engines that have good efficienct clean combustion- they need less air (oxygen) and are able to burn cleanly.
Above- when I said: "the BSFC or efficiency numbers are pitiful- and when I see numbers quoted of needing 32:1 air fuel ratio - I can see why, with the opposed piston 2 stroke I was involved in - we could get that number right down to 18:1"- I was touching on this and comparing it to my experience- according to the papers- the 8v92 needs a lot of air (hence 32:1 Air fuel ratio) to burn cleanly- this means that its combustion isn't great. When combustion isn't great, the engine will black smoke quicker than 'brand b' engine with better combustion when you inject the same amount of fuel.
In your case- the injectors are probably pretty potent. It would be interesting to see what they are. Mine are C60s, I wonder if yours are 75s? But it still doesn't smoke. The thing they do on the 71s is advance the timing to mitigate potential to smoke.
The only way to supply more air is to change the blower speed but that's very hard on a gear driven type of equipment like ours and its a precarious balancing act- if one does this , they also increase parasitic losses which is bad for efficiency.
Big injectors like 80 or 90, timed so they don't smoke, and a cooling system in good order, probably explains your circumstance.
JC
The technology DD used on the 92 with the liners having 2 inches of water at top carried over to the DD 4 stroke engines cooling the upper cylinder to produce more HP.
The 92 series are not really a wet liner if you compare it to other wet liner engines like Cummins or Cat the 92 just has a 2 inch space that contacts the coolant.
The 8v92 will always be one of my favorite engines second to only the CAT 3406.FWIW I have in my shop one of the double O's 8v92TA engine that was produced between the old green engine and the Silver 92 so far I found very little difference in it and a Silver 8v92,I do like the single wide oil control ring they used instead of the 2 thin ones used today
Thanks for confirming what I was thinking...one aspect of it at least. Air and fuel I understand. I know my injectors are larger, I have the invoice for them somewhere. I can't remember what size...I'll dig it up.
Your responses do lead me to what might be the most stupid question ever asked. If so, my apologies...it just popped into my head. I know nothing about 8V92s.
You know how there is so much discussion about the 8V92 and overheating in coach applications?
Is it possible that the increased air demands and the configuration could be partially responsible for that problem? If so, could the intake point of the cycle be modified in some creative (exterior) way to introduce cooler air?
Quote from: daddysgirl on June 24, 2017, 12:48:58 PM
Thanks for confirming what I was thinking...one aspect of it at least. Air and fuel I understand. I know my injectors are larger, I have the invoice for them somewhere. I can't remember what size...I'll dig it up.
Your responses do lead me to what might be the most stupid question ever asked. If so, my apologies...it just popped into my head. I know nothing about 8V92s.
You know how there is so much discussion about the 8V92 and overheating in coach applications?
Is it possible that the increased air demands and the configuration could be partially responsible for that problem? If so, could the intake point of the cycle be modified in some creative (exterior) way to introduce cooler air?
Intake or ambient air could be cooled. That's what a charge air cooler would or could do. The problem is - that it needs to be tied up to some sort of heat exchanger like a radiator. And....if you cool the intake charge- it WILL have some impact on combustion temps and therefore coolant temps but it wont be as good a method to reduce temps as cooling the coolant further. Modern engines cool intake charge for other reasons- to cool the EGR (for emissions reasons) so this is how I know- if you go too cool here you can end up with internal engine condensation and then corrosion- you typically want to target about 55 deg C.
Other ways to tackle it- would be:
-Advancing injection timing- if you do this- the exhaust temps get cooler but the piston temps go up- the problem with doing this is that your peak cylinder pressure goes up and you could go above what the engine components were designed for. So this rules that out
-You could BLOW more air through- using the blower- i.e changing the blower ratio. However in the real world- how do you do this? Will we get a gear set made up and somehow matched? In addition- doing this would make the engine specific fuel efficiency (BSFC go down the toilet due to increased parasitic loss.
-You could mess around with the port timing- but this would involve getting liners with new port windows custom made- whos going to do that?
(https://busconversionmagazine.com/forum/proxy.php?request=http%3A%2F%2Fi273.photobucket.com%2Falbums%2Fjj229%2FMarquisRex%2F2%2520stroke%2520vs%25204%2520stroke%2520port%2520timing_zpsem2z98ah.png&hash=8b2f85c9ec05e367beaae436cd89546b128c4b19) (http://s273.photobucket.com/user/MarquisRex/media/2%20stroke%20vs%204%20stroke%20port%20timing_zpsem2z98ah.png.html)
In the above pic- the green curve is the intake opening area and the red is exhaust. The plot on the right shows a conventional diesel engine like a Cummins ISB and the plot on the left shows a 2 stroke prototype engine. You'll notice the big where the red and green curves overlap is where both intake and exhausting are simultaneously open. A 2 stroke characteristic is to have that simulataneous opening period very large- its called the scavenging period. If this is increased- it can help cool the engine but is very wasteful and can shoot fresh intake charge through the engine and again waste energy/efficiency. So its very complicated.
What I would do is simply try to find ways of increasing the cooling ability of the vehicle/cooling system. I have measured heat rejection data for a series 60 and various 4 stroke Cummins engines. I have friends who have sized up radiators and cores so I could probably come up with a rule of thumb as to what radiator core would dissipate what. The problem I have is- how do I find out how much a 550 bhp 8v92TA produces in terms of heat. I will continue to do some digging and extrapolating. Something tells me it wont be the same rule of thumb or ascertained by simply scaling 4 stroke data I already have. I will continue digging. Once I get that I can find a way to size up radiators and sort it. That's what us engineers do.
Dread -
I went with Scott Robertson on Thursday to help him pick up an MC-6 with the original 12V71 engine in it.
Unlike the 5s, 7s, 8s, 9s, etc., the 6 uses a HUGE, hydraulically-driven, radiator on the LH side, like GM, Prevost & Eagle and now current MCIs.
Only reason I mention this is that the 12V71 hp & torque figures aren't that different from an 8V92TA, so you might be able to come up with some rough heat load numbers that could help with your extrapolations.
You might have to look outside the normal transportation numbers for the 12V, possibly marine or industrial applications, to find what you're looking for.
FWIW & HTH. . .
;)
PS: I drove the 6 for about a mile - that 12V has got TONS of torque! I remember reading somewhere that with 60 injectors, it produces 1350 ftlbs of torque at 1200 rpm! Insane (for it's day, of course!) Fun, none the less! ;D
Andrea,, probably the reason you perform so well is the location your in.. the 8V71 does very well near sea level but runs out of breath quickly above 5 or 6 thousand feet.>>>Dan
Very interesting, thank you for those insights.
I often wonder how much improvement a 6V92 would derive from an air-air CAC instead of that air-water aftercooler that probably heats up the coolant more than it helps the engine's intake air temperatures. I think a lot of our perennial cooling problems are directly related to that aftercooler.
During your research did you have any chance to compare the venerable Commer TS2 with Detroit's 2-strokes? Is the TS2's opposed-piston design advantageous to a non-OP 2-stroke? (How does the Deltic also compare?) TS2s used to get quite a lot of power from a relatively small displacement, but I suspect they weren't torquey.
You mention the difficulty of producing liners with different port windows. Didn't Don Fairchild do this with his CCTS-modified 2-stroke Detroits that could achieve later emissions standards?
John
Quote from: RJ on June 24, 2017, 06:29:20 PM
Dread -
I went with Scott Robertson on Thursday to help him pick up an MC-6 with the original 12V71 engine in it.
Unlike the 5s, 7s, 8s, 9s, etc., the 6 uses a HUGE, hydraulically-driven, radiator on the LH side, like GM, Prevost & Eagle and now current MCIs.
Only reason I mention this is that the 12V71 hp & torque figures aren't that different from an 8V92TA, so you might be able to come up with some rough heat load numbers that could help with your extrapolations.
You might have to look outside the normal transportation numbers for the 12V, possibly marine or industrial applications, to find what you're looking for.
FWIW & HTH. . .
;)
PS: I drove the 6 for about a mile - that 12V has got TONS of torque! I remember reading somewhere that with 60 injectors, it produces 1350 ftlbs of torque at 1200 rpm! Insane (for it's day, of course!) Fun, none the less! ;D
That's insane and amazing! I love the idea of the 12 cylinder however I must keep sane and I know the Turbo has benefits at high altitude!
Does the MC6 with 12v71 have just ONE radiator on the Left hand side or in this radiator in addition to the two that are there on the MC5s?
I just talked to my friend whos still at the Opposed piston 2 stroke company and we tried to figure out,qualitively if not quantitively, if the Detroit 2 stroke would be worse in terms of heat rejection than a series 60 4 stroke, or a Cummins 4 stroke, then where it stood relative to an opposed piston 2 stroke etc.
We decided that the fact that it has 4 exhaust valves and a coolant jacket around that made it worse than a 2 stroke opposed piston (this rejects less heat to coolant and more to the exhaust gases themselves) and likely worse than a the 4 strokes.
Quote from: Iceni John on June 24, 2017, 07:11:07 PM
Very interesting, thank you for those insights.
I often wonder how much improvement a 6V92 would derive from an air-air CAC instead of that air-water aftercooler that probably heats up the coolant more than it helps the engine's intake air temperatures. I think a lot of our perennial cooling problems are directly related to that aftercooler.
During your research did you have any chance to compare the venerable Commer TS2 with Detroit's 2-strokes? Is the TS2's opposed-piston design advantageous to a non-OP 2-stroke? (How does the Deltic also compare?) TS2s used to get quite a lot of power from a relatively small displacement, but I suspect they weren't torquey.
You mention the difficulty of producing liners with different port windows. Didn't Don Fairchild do this with his CCTS-modified 2-stroke Detroits that could achieve later emissions standards?
John
I mentioned the difficulty of producing a liner- yes, as I'm a single independent guy- trying to save my money! At Achates with opposed piston engines- we made them all the time, but I'd build a one off. Believe me, I'm not going into some sort of business trying to pedal this. I don't see a viable market.
We bought a Tillings Steven engine from New Zealand (the commers seem to have a following down there) but on the first run one of the huge rocker arms broke and we never got any useful data out of it. :-(
What I have found with opposed piston engines is the following:
The- the OP layout allows for a long stroke which has advantages in terms of scavenging and thermal efficiency but this is pretty much lost due to the friction from the extra piston- also figure that the piston skirt grows ALOT with increased stroke to maintain the port timing.
We found that less heat was rejected to the coolant and more went to the exhaust system. As I extrapolated or hypothesised above- I reckon our Detroit diesel style would possibly reject more heat to coolant- as it has a water jacket around 4 exhaust valves...
Quote from: Iceni John on June 24, 2017, 07:11:07 PM
Very interesting, thank you for those insights.
You mention the difficulty of producing liners with different port windows. Didn't Don Fairchild do this with his CCTS-modified 2-stroke Detroits that could achieve later emissions standards?
John
Yes Don did do that,you can buy different port size liners aftermarket or from Detroit the
95 and 105 are the 2 most popular now
Starting with an 8V-71N with C65 injectors, that gives me 300hp and 800lb/ft torque. By increasing to 7G75 injectors (same 18.7 two piece pistons), custom air to air intercooler, by pass blower, but same injection timing, power was increased to 375hp and 1125lb/ft torque. While fuel mileage remains about the same (5-6), my performance has improved and smoking in high altitudes has been reduced to almost zero.
I had a OO-92 (stood for Owner Operator) 8V-92TA in my first truck in 1980. While it was a great performer and loved the engine sound, maintenance on it was intense and fuel mileage was about half of what trucks get today. The only 2 stroke Diesel I know that are extremely efficient are the giant low speed engines used in container ships. They run at 82rpm and have a 39" bore by a 135" stroke (yes thats over 11ft!). Those engines are the most efficient engines ever made. Good Luck, TomC
Tom Detroit did the smart thing letting you truckers find the trouble spots for the 8v92 ;D they only built 11,000 of the double O engines
Yes, I enjoyed driving the 8V-92TA. When I got my next truck, it had a Cat 3406B-I had to relearn to shift all over again.
8V-92TA has a lot of preventative maintenance. You change the oil at 10,000 miles. At 100,000 you run the rack and adjust valves. 200,000mi run the rack and adjust valves and roll in rod and main bearings. 300,000 you run the rack and adjust valves and rebuild turbo, blower, governor. 400,000 you run the rack and roll in rod and main bearings. 500,000 usually ready for engine overhaul. Fuel mileage average- 4.8
Compare to the Cat 3406B. You change the oil at 12,000 miles. Every 100,000 adjust the valves. At 500,000 roll in rod and main bearings, injector tips. 1,000,000 or when needed overhaul engine. Fuel mileage average- 5.6
Compare to the new Detroit DD engines. You change the oil at 50,000 miles. Adjust the valves at 100,000, then every 500,000 after that. Overhaul at 1,200,000 miles. Fuel mileage average- 8.
Good Luck, TomC
s.
Only reason I mention this is that the 12V71 hp & torque figures aren't that different from an 8V92TA, so you might be able to come up with some rough heat load numbers that could help with your extrapolations.
.
FWIW & HTH. . .
;)
The DD application manuals and engineering bulletins have the heat rejection numbers in the manuals needed for the 2 strokes.The 8v92 replaced the 12v71 mostly because of the HP to weight ratio the 12V71 really never made it's mark in the trucks it was to heavy a 8v92 weighs 2306 lbs and the 12v71 a whopping 3502 lbs for about the same hp and torque rating
Quote from: luvrbus on June 25, 2017, 07:00:26 AM
The DD application manuals and engineering bulletins have the heat rejection numbers in the manuals needed for the 2 strokes.The 8v92 replaced the 12v71 mostly because of the HP to weight ratio the 12V71 really never made it's mark in the trucks it was to heavy a 8v92 weighs 2306 lbs and the 12v71 a whopping 3502 lbs for about the same hp and torque rating
Thanks! Where can I get hold of these manuals?
Would save me from extrapolating!
I found data on a CAT C15 (485 Bhp), a Cummins ISX and a DD15 engine and their heat rejection numbers- (all between about 140-200 kw to coolant) and I was trying to get a 'feel' for typical numbers. If I get direct numbers from DD about the 8v92 so much the better!
In the application manual DD used a simple formula 2250 BTU for ea HP setting on the 8v92 TA engine almost twice as much for a 500 hp 8v92TA as compared to the 60 series with 500 hp
Quote from: Dreadnought on June 24, 2017, 04:08:48 PM
I have friends who have sized up radiators and cores so I could probably come up with a rule of thumb as to what radiator core would dissipate what.
Is there a simple way to determine a radiator's heat rejection ability that us busnuts could use to know if our cooling systems are adequate or not? I recently completely replaced my entire cooling system in an effort to address some serious overheating, and while my new setup is much better than before I still wish for slightly lower coolant temperatures. I'm toying with the idea of adding a second smaller radiator to help in hot weather, but I've not been able to find a single radiator maker who can quote plausible heat rejection numbers for their radiators. Is it really that complicated?
Using Detroit's formula of 2250 BTU/hour per HP, my 277 HP engine should need 10,400 BTU/minute of radiator capacity. When I turn on my 150,000 BTU/hour heaters I see a noticeable drop in coolant temps, so if I could achieve the same results with a second radiator I'll be happy.
John
Quote from: Dreadnought on June 24, 2017, 07:11:51 PM
Does the MC6 with 12v71 have just ONE radiator on the Left hand side or in this radiator in addition to the two that are there on the MC5s?
Just one, HUGE, radiator on the MC-6, LH side, hydraulically-driven fan.
Scott's bus is currently stored about an hour away from me. Next time he's in town, if I go with him, I'll measure it for you.
FWIW & HTH. . .
;)
When I was running twin turbos on the 8v92 in the Eagle I had Atlas in Texas build me a radiator for it the dimensions where 42 inches tall X 47-1/2 inches wide with 9 rows of tubes, with a 13 blade 31 inch dia variable pitch plastic fan and I could still heat it if not careful on a long grade
Since all the knowledgeable guys are here, if you ran a proper sized turbo and instead of dumping the cooled charge air into the blower what would happen if the turbo boost air got instead dumped into the air box inspection cover(s)?
I'm thinking of some sort of clapper valve to keep charge air from coming back out through the blower.
Quote from: Iceni John on June 25, 2017, 10:10:14 AM
Is there a simple way to determine a radiator's heat rejection ability that us busnuts could use to know if our cooling systems are adequate or not? I recently completely replaced my entire cooling system in an effort to address some serious overheating, and while my new setup is much better than before I still wish for slightly lower coolant temperatures. I'm toying with the idea of adding a second smaller radiator to help in hot weather, but I've not been able to find a single radiator maker who can quote plausible heat rejection numbers for their radiators. Is it really that complicated?
Using Detroit's formula of 2250 BTU/hour per HP, my 277 HP engine should need 10,400 BTU/minute of radiator capacity. When I turn on my 150,000 BTU/hour heaters I see a noticeable drop in coolant temps, so if I could achieve the same results with a second radiator I'll be happy.
John
I'm pretty sure there is , but I don't know what the rule of thumb is right now. I have to confer with some old friends...
Quote from: HB of CJ on June 25, 2017, 12:47:57 PM
Since all the knowledgeable guys are here, if you ran a proper sized turbo and instead of dumping the cooled charge air into the blower what would happen if the turbo boost air got instead dumped into the air box inspection cover(s)?
I'm thinking of some sort of clapper valve to keep charge air from coming back out through the blower.
Quote from: Utahclaimjumper on June 24, 2017, 06:36:32 PM
Andrea,, probably the reason you perform so well is the location your in.. the 8V71 does very well near sea level but runs out of breath quickly above 5 or 6 thousand feet.>>>Dan
Yes, at sea level, I'll get a ticket if I'm not careful. However, I've been from VA to CA and back, and all over the mountains...I remember 6200 feet, and 7000 a few years ago, and the bus didn't struggle. THAT is what I don't understand.
I like Toms turbo setup, but I just finished tearing out and reinsulating the rear interior, over the engine compartment, as the beginning of the re-rebuild process. It's going to be a while before I worry about the engine. But I will be sending Tom a message or two before I start that process.
Hi All, when I was searching for a bigger bus, there was an MCI9, that had 2 additional radiators inside where the side engine doors were on either side and it was an 8V92. I think he said it was from Saudi Arabia. It was in central texas. He said it never overheated no matter how hard he pushed it. Clifford how would you route inlet and outlet pipes, inline with the upper radiators? lvmci...
At risk of sounding like an idiot. I noticed that nobody is talking about the 6v92 (which is what I have). Is that a dinosaur? I'm curious on how much of a difference in speed/power between the 6v vs 8v. I guess it shouldn't matter to me really b/c I don't plan on changing engines unless I do something stupid and ruin the one I have.
lvmci, my idea for a second radiator for my 6V92 is to use the existing 1" coolant outlet on the driver-side of the block that presently supplies the two heaters. (Curiously, the heaters are supplied through 3/4" hoses and pipes, so presumably a 3/4" flow rate is sufficient for 150,000 BTU/hour heat dissipation; the 1" outlet now immediately reduces down to 3/4".) If I ran a 1" line to the radiator and a 1.25" return line back to the existing radiator lower return pipe into the water pump, I'm hoping I wouldn't need a coolant booster pump like my heaters now have. I've found a 3-row aluminum radiator for a Ford Excursion which is the largest that will fit, and if I used two shrouded 14" or 16" Hayden electric fans would they draw enough air through it? So, the big question is, what is this radiator's heat rejection ability? I would also need to know the total CFM of the fans and the static pressure, and the coolant flow rate. If this radiator matches the heaters' 150,000 BTU then it's worth doing, but if it doesn't then I won't bother with it.
The more I learn about heat dissipation the more complicated it becomes! I know that what's theoretically possible doesn't always work so well in practice, and intuition doesn't get you very far. Nothing's easy.
John
Hi John, does it go toward the driver and cabin heat? Where does it return to the block? Is it also 1"? tom, lvmci...
Quote from: lvmci on June 26, 2017, 06:02:51 PM
Hi John, does it go toward the driver and cabin heat? Where does it return to the block? Is it also 1"? tom, lvmci...
The present 3/4" feed from the engine for the heaters goes to a coolant booster pump, then to some 3/4" hard pipes that go to the front and all the way back to the radiator's lower return pipe into the water pump inlet. My idea is to have valves to select coolant flow to either the heater loop or to the additional radiator, but not to both at the same time. I'm hoping the present 1"-to-3/4" coolant supply has enough flow force to avoid needing a booster pump for the additional radiator, especially if I use a larger 1.25" return back to the water pump; the pump is sucking the return as much as pushing its outflow. I definitely don't want to introduce any cavitation with this extra circuit.
Has anyone here done anything similar to this? I want just a small amount of extra cooling for those rare occasions when the temperature gauge keeps creeping up, but I really don't want to use misters.
John
John, I'm thinking about making the driver side engine bay door into a grill, like eagles and the MCI six and 7 combo and go directly from the outlet and inlet pipe on the driver side of the engine adding continuous Cooling because of living in the desert, Tom...
I'd think that if you have done everything to get your coolant temp down but still have problem that maybe you have a combustion gas leakage into your coolant. That can cause some strange effects, like loss of coolant pressure and high temps.
Reading all of this had led me to another question (I'm sorry. I wish I wasn't as inquisitive)
You all are describing some different ways to cool the coolant, and I personally think there are various thoughtful ways to accomplish this.
So this question is on the other end of the temp spectrum...
I'm a fan of exhaust wrap because it works. BUT...Because the entire issue is reducing overall heat, what could be done to better channel/address the exhaust?
I've seen buses with the rear doors louvered, different ways of adding extra ambient air to the engine compartment. My issue with this is that if it is not done correctly, (on the ease coast at least) you end up with a wet engine compartment and that leads to rust/corrosion. Or if the outside temp is too high are you really helping the situation?
On a coach, the engine compartment contains more than just the engine, and electrical components don't like water. So... what about helping cool everything by addressing the other side...the exhaust?
The freer the exhaust flow, the more heat goes out the pipe. The less exhaust restriction, the better. Since I replaced my muffler with a resonator, I think I run cooler. Wrapping also helps getting the exhaust out faster, because the hotter it is, the more it expands, therefore the faster it goes out.
Outside air, drawn through the rads, is cooler than what is inside the engine compartment, even on a hot day.
Regarding the electrical components getting corroded, they already are getting most air on a rainy day, or worst in the winter, so a little more by increasing the flow wouldn't make a big difference. Replacing rusty switches and the like is a normal maintenance thing anyway.
JC
I think we're way off Dreadnaughts thread. All the DD gurus have always written about pushing a 2 stroke and the heat that creates. My engine can idle for some time and not heatup, so I dont think the more complex issues are my heat problem with mountain driving. Every direction from LV is mountains to go over and those mountains that dont amount to a hill of beans in the winter, but in summer I keep my eyes glued to the temperature gauage as the bus climbs and so does the gauge. Im going to recore or rod out, the two big size radiators on my 8V92T 102C3. Ive added sprayers and listend to Clifford, Gary and the rest of the knowledgeable bunch on driving technique, all their suggestions have led to my successful driving over the mountains. But I want to increase the horespower, as it is at the minimum horsepower rating right now. Observing the different solutions is not only interesting, but will lead to more fun while driving my big bus. You guys are great and once again, thanks for your kindness in advising all of us new to diesel, tom, lvmci...
My observations about coastal bus lines is the tremendous suction on the two radiator systems on MCIs, is that's where to look for corrosion, rust when looking for problems when searching for a new bus. So I dont think protection from outside salt air is posible on those models. lvmc...
Quote from: Iceni John on June 26, 2017, 08:29:21 PM
The present 3/4" feed from the engine for the heaters goes to a coolant booster pump, then to some 3/4" hard pipes that go to the front and all the way back to the radiator's lower return pipe into the water pump inlet. My idea is to have valves to select coolant flow to either the heater loop or to the additional radiator, but not to both at the same time. I'm hoping the present 1"-to-3/4" coolant supply has enough flow force to avoid needing a booster pump for the additional radiator, especially if I use a larger 1.25" return back to the water pump; the pump is sucking the return as much as pushing its outflow. I definitely don't want to introduce any cavitation with this extra circuit.
Has anyone here done anything similar to this? I want just a small amount of extra cooling for those rare occasions when the temperature gauge keeps creeping up, but I really don't want to use misters.
John
I added an extra radiator using the 1" heater hose that used to supply the passenger heating system. The coolant pump moves the coolant through a heater core that measures 1' by 3' and uses 3 electric 12v fans with a 190 degree switch. The RTS has a screen in the roof so that is where the extra radiator is mounted. With this system I was able to quit running the water sprayers on the main radiator. 350HP 6V92TA.
--Geoff
Geoff, good to hear that my idea's not so whacko after all! The Ford radiator is between 3 and 4 sq.ft core size and has 3 rows, and I want to fit as many fans as space allows, ideally two 16" or maybe four smaller ones on a shroud. I would let the coolant flow through it all the time, but have the fans switch on at 195 degrees. It sounds like we're on the same track here. If it drops temps by just a few degrees, I'll be happy.
I think I already have a low-restriction Donaldson muffler (it's loud!), and I'm also thinking about wrapping all the exhaust pipes to keep the heat inside them. I don't think I have an exhaust leak into the coolant, but I'll check it anyway. Keeping these old 2-strokes cool is never easy. Sometimes I'm tempted to put in a Series 50, but those engines leave me cold (so to speak).
Thanks, John
I should mention that the heater core I used was designed to run high up so it has a small air bleed hose with a check valve going down to the main radiator. Without the bleed hose you would probably get an air lock.
--Geoff
Here is some food for thought,the water pump on a Detroit is 67 GPM @2100 rpm and takes very little wear on the impeller to diminish that flow.It marine use the raw water pump is 107 GPM over the the exchanger on a 6v92 with 70 dgree water
Quote from: luvrbus on June 27, 2017, 03:53:12 PMHere is some food for thought,the water pump on a Detroit is 67 GPM @2100 rpm and takes very little wear on the impeller to diminish that flow.It marine use the raw water pump is 107 GPM over the the exchanger on a 6v92 with 70 dgree water
Is there a different design water pump with an alternative part number that could be fitted to a DD 2stroke in a bus? If so, would a larger (50%+) flow be a benefit to someone who is having overheat problems?
I thought I heard that if the coolant flows too fast through the rad, it doesn't have time to cool. So maybe a faster pump is not the answer?
JC
My 8v92 has a one inch line off each bank and two returns in the lower radiator line. No reason to switch between the radiator and heater if you want to run off both sides of the engine.
Quote from: lostagain on June 27, 2017, 08:53:17 PM
I thought I heard that if the coolant flows too fast through the rad, it doesn't have time to cool. So maybe a faster pump is not the answer?
JC
Too fast thru the radiator doesn't make sense to me - isn't it is going the same speed thru the engine?
What makes more sense to me is lower pressure at the pump inlet causing tiny 'air' bubbles to form in the coolant - that reduces the coolants ability to transfer heat. . . . . It takes a lot longer for that 'air' to go away than it did to form.
Changing a properly designed system seems to always present unexpected opportunities. :o
BTW, I have a technical paper on my coach that states the cooling system was designed for the coolant temperature to stabilize at 125F above ambient at full power. Would be great if they all came with that information.
Quote from: kyle4501 on June 29, 2017, 06:31:03 AM
Too fast thru the radiator doesn't make sense to me - isn't it is going the same speed thru the engine?
What makes more sense to me is lower pressure at the pump inlet causing tiny 'air' bubbles to form in the coolant - that reduces the coolants ability to transfer heat. . . . . It takes a lot longer for that 'air' to go away than it did to form.
Changing a properly designed system seems to always present unexpected opportunities. :o
BTW, I have a technical paper on my coach that states the cooling system was designed for the coolant temperature to stabilize at 125F above ambient at full power. Would be great if they all came with that information.
It's too bad that Arrowhead Radiator's website is now gone - they had a very informative paper there called "14 ways to improve cooling in high-performance vehicles" or something like that, and it explained very clearly about the pros and cons of different coolant flow rates.
You mention bubbles caused by suction. That's cavitation, and it's something I am concerned about if I start to change coolant flow rates and pressures by having a second radiator. Whether I would need an extra circulation pump like Geoff has for his second radiator, or if the engine's water pump has sufficient pressure and flow rate (bearing in mind what Clifford said about wear on impellers), are all things I need to research before plunging into this project. I just don't want to create more problems than I solve.
John
I worked with Griffin Radiators on hard to cool cars & trucks that had been modified for more power in the early 90's.
I was surprised to see how much was involved in a cooling system.
They were very quick to find real & durable solutions for those unusual cooling applications.
(sure was nice to have the quickest street car at the drag strip that didn't have any cooling problems - even in August ! )
I asked their thoughts on too fast thru the radiator. Their response was that cavitation always happened before they could find a flow that was too fast.
Quote from: kyle4501 on June 29, 2017, 08:46:34 PM
I worked with Griffin Radiators on hard to cool cars & trucks that had been modified for more power in the early 90's.
I was surprised to see how much was involved in a cooling system.
They were very quick to find real & durable solutions for those unusual cooling applications.
(sure was nice to have the quickest street car at the drag strip that didn't have any cooling problems - even in August ! )
I asked their thoughts on too fast thru the radiator. Their response was that cavitation always happened before they could find a flow that was too fast.
I talked to griffin too.
I mention it here
http://www.busconversions.com/bbs/index.php?topic=31978.0 (http://www.busconversions.com/bbs/index.php?topic=31978.0)
It was interesting, they said that although copper was a better conductor, the way the copper or even brass was soldiered didn't help heat condiuction and aluminium didn't have those impediments. They said they did custom work not only for hot rods but also industrial applications, where they would use CFD (computation fluid dynamics) to model the system etc.
One of the truck applications I worked on- the pump would cavitate if spun any faster and the impeller would eventually suffer from cavitation erosion. The solution was to decrease the pump rotational speed but make it bigger to maintain/increase volume flow rate
I have a '63 Ford Falcon with 302 in it. I replaced the water pump with a rebuilt. The impeller looked like a piece of heavy sheet metal with 6 bent lips on it. It cavitated badly above 3,000 (car is geared 3,500 at 75), and wouldn't cool. I then replaced with a Ford rebuilt that had the normal look impeller and problem solved.
Quote from: luvrbus on June 27, 2017, 03:53:12 PM
Here is some food for thought,the water pump on a Detroit is 67 GPM @2100 rpm and takes very little wear on the impeller to diminish that flow.When in marine use the raw water pump is 107 GPM over the the exchanger on a 6v92 with 70 degree water
How did this happen lol
With all the battery power why not a large radiator fan?
I know this an old topic but it is a perennial one.
Just joined this board and I would like to add my 2 cents worth as I have taken a slightly different approach.
Bus was an 84 model, here in Aussie called a Tourmaster. Pretty standard setup with rear mounted north south 6V92T and a six, now 7 speed crash box. Rockwell running gear. Called Vanishing Point after a favourite movie.
Pretty rusty when I purchased, abandoned project, at that age there must have been 20K rivets, all potential leak points so a coremat 6mm fibreglass body was on the agenda, after lots of steelwork. Cut off at floor level and started again.
Very early in the piece joined an experimental Lithium group here and fitted both 12 and 24 volt Lithium banks, 200 Ah x 12 V and 800 Ah x 24 V. To charge them fitted 3000 watts of solar.
With so much electrical power thermatics should be looked at. The original radiator in good condition was rodded and tested, 4 x 14" high performance fans fitted (these had the motors from 16" fans) in a tight fitting shroud.
Knew this would not be enough so bought a ford V8 radiator and shroud/fan setup off ebay. This has 2 x 12 v fans, run real well in series with 24 v supply. Perfect for coach alone, but when I put my enclosed car trailer on, with 400 ltrs water, Suzuki 5 door Grand Vitara, washing machine, tools, coach and trailer spares, was restricted to 80 kph. I don't like to hold up traffic so back to the drawing board.
I invested in a custom made radiator (aluminium) which was thicker and higher than the ford one which was removed. We fitted 2 x 16" fans to the new radiator
This allowed travel at 100 kph on even the hottest days, on the flat with the trailer on, sat at around 82 deg C.
However to get anywhere west of where we lived at the time you had to climb the great dividing range, some of which is 1 in 10, or a less steep route which is 9 k's long. Either way engine heat was getting dangerous by the time you got to the top.
As coach by itself was solved I took the ford radiator and mounted it above the washing machine box on the trailer, rationale was I only needed it with the trailer on so it could stay there. Couple of hoses with hydraulic fittings and a spare wire via the trailer plug and the trailer mounted radiator only comes into play at 86 deg C, and then only for a couple of minutes. Water flow is controlled by a couple of electric ball valves that only open when the trailer mounted radiator is activated.
So finally I am happy with the cooling performance as I am actually able to move in excess of what the old Horton fan was doing which was 7,000 litres of air a second at full song. And I have saved the approx 10% of horsepower required to drive the fan
Funniest thing is everyone sees this black thing sitting up there and thinks the whole trailer is a bloody fridge unit !
Busman, sounds like a great system you built! Are your radiator fans powered only by the solar panels? If so, what do you do when the sun don't shine?
I have 700 watts of solar on my bus, which is a great help when the sun shines high and bright. But there are a lots of times when it doesn't, either because it is cloudy, or parked in the shade, or the sun is low like in winter, and I have to run the generator if not plugged in to shore.
JC
Hi JC,
I have switches up front that allow me to choose where the power comes from. I can select either the DN50 or solar/battery bank just by flicking a switch. Divided into 3 sections, original, custom rad and trailer rad. Also have an LED for each section so I know if they are on or not, when they should be. This is how I know how long the trailer one runs for.
I have no generator, with so much solar and the large Lithium bank I don't need one.
If it is raining for instance, I will be down on thermatic fan use, there has been a couple of occasions going downhill in the rain when they have all been off, it depends on the conditions as to how much cooling is needed, less heat, less cooling.
The thing I have discovered is simply that you need to move around the same amount of air as the original, then thermatics work well.
Having such a large battery bank is a bonus, I can run one of my splits all night with no problems
Cheers
William