Coffee time conversation and this topic came up. Should the exhaust be capped when transporting the machine [excavator] down the highway to protect the turbo. What is your educated thought on this topic.
I usually do it but on the newer machines there is so much aftertreatment hardware to the exhaust I'm told it's not necessary. Whether or not it's needed, I still do it as a carryover from the old days. Folgers coffee can, (plastic nowadays) and gorilla tape along with a gallon of mineral spirits in the cab is standard package for me.
Well, it ultimately depends on whether the engine has any exhaust/intake valve overlap designed into it. Each model of engine will be different, so rather than take a chance, on a turboed engine i plug the exhaust. The odds are extremely high but i would rather not chance it but thats just me
Belt and suspenders type of thing. I'll do it if the exhaust is facing forward and we're taking it a long distance.
I've never covered the 120 stack :shrug:
Failure to strap the coffee can down before transport was a 'fireable' offense. All them drivers heard that, and did a good job. As a mechanic, I can't see enough breeze running thru the turbo to gall bearings. Is it possible? Is there any other reason to cap the stack during transport?
On the older mechanical engines the turbochargers could freewheel without lubrication from either pressure induced by "ram air", or vacuum created by the air passing over the exhaust stack creating a low pressure zone in the exhaust stack. This creates a suction through the engine causing the turbocharger to spin without lubrication as air is pulled in through the intake manifold. The same scenario in reverse for the ram air effect.
Never done it in 57 years of owning turbocharged machines, and I often hauled them several hundred kilometres at 100kmh (62mph) with open exhausts. Never had a turbo failure I could definitively trace back to spinning without lubrication whilst zipping down the highway. All the turbos I've ever experienced failure with, either had shattered valve heads go through them or they simply wore out and started leaking oil into the inlet side. Compressor/turbine wheels only turn at very low speed from air passing the exhaust pipe, and residual oil in the bearings is adequate for lubrication under those conditions. I think perhaps the earliest turbochargers (mid-1950's) might have had some problems in this area, because the earlier turbochargers were bigger, the compressers/turbines/shaft were bigger accordingly, and they more than likely spun with more speed due to inertia - and perhaps the lube systems for them contained inadequate residual oil. Also, none of the early tractor engines were muffled, a muffler slows a lot of air movement. As well as all that, tractors of the 50's used oil bath air cleaners, so air movement though a stopped engine was easier with an oil bath air cleaner, than with dry-type air cleaner elements. The other factor is the fancy curved-end exhausts, such as Allis-Chalmers used - if these faced forward, they would act like an air scoop. I've only ever had straight pipe exhausts on my machines, and many had rain caps.
We cover all of ours. I really doubt that we stand any chance of ruining a turbo in this day and age but it keeps rain out, only takes a minute, and removes all doubt. I especially want the exhaust covered when hauling for hire just so our culpability for any damage to a turbo is mitigated.
CYA. I have covered the exhaust on a machine maybe half a dozen times in 30 years, like OZ have never had a turbo failure period. Hauled everything from 780C to 1150E, 446B to 644E, 880B, 1080B, 9030B, D7H, D61, 75C, 95E, 621B, 210C, now 290, and probably a couple dozen 1 timers. It is a question for the ages.
first time I saw it, bought a d8n for a pond project, heavy hauling dude said he always does it, company policy. I have hauled lots of stuff without it, but its still in the back of man mind so whenever I mess with exhaust I always face the pipe out sideways instead of straight back.
Ide be more worried about heavy rain entering the exhaust.
I this world of techno crap---no one has delved into the mystery of spinning compressor turbine theory's? It has been a great subject in the annuals of internet worrying. Surprised someone hasn't gone the Harbor Freight & Salvage route & installed a bore scope in the exhaust or intake side and transmitted that finding to a laptop for all to see-----is there a Bigfoot or not and is he fa@king with my turbo, although there was one caught messing with a engine on a airplane in a episode of The Twilight Zone, seen by William Shatner himself. * A mission for someone to take on, not me though, I'm busy.
I'm probably wrong here but... surely you need air FLOW to make a turbo spin? if you are getting a flow of air through the turbo with enough force it to spin at a speed that will damage a turbo ( even prolonged steady spinning will be fine with the residual oil on the bearing surfaces), you have bigger problems than the turbo! There is a small amount of valve overlap to create flow, but only on one or maybe two at most cylinders and would that cause a significant enough air flow to spin a turbo fast enough to create any form of lasting, Also a second thought you'd be trying to spin a turbo in the opposite direction it is designed to flow the air in, so even more air flow would be required? I might have to fire up the compressor and and old unit turbo for sciences sake
Only one at a time on a 6 cylinder and it would be minimal, valve overlap would take place for example when 1 is at TDC & 6 would be in overlap.
So basically minimal flow of air then, the air would enter the turbo through the exhaust side and hit the exhaust valves in the head with valves in the a small amount would pass the valve but nowhere near enough to make the exhaust side spin in the reverse direction at any sort of speed that would cause any issue
I think the upshot of this is those low boy drivers just better slow the heck down. They're driving too fast!
Most every skid steer is hauled with the exhaust facing the wind. Never heard if an issue. Would be at best 1 cylinder that's sitting with intake and exhaust valves both open
It reminds of the mechanic/wives tail-----{Don't touch the bearing surface of new main & rod bearings because the oil in your hands will etch the bearing}.. Peeeewwwwwwwwwwww.
Something I've always wondered about. I cover the exhaust because the boss wants it. I found a wind load calculator online and discovered that 60mph creates .06 psi. Then I found an airflow calculator that says 60 mph through 1 square inch is 36cfm. I don't know what the area of the opening of a partially open valve is, I just guesstimated that number. Doesn't seem like enough pressure or flow to do much.
Probably .070. But overlap in a gas engine is measured at .050 and how much lobe separation 110 or 112. Either way it wouldn't matter--just isn't enough air flow.
I have never covered the exhaust, and have yet to have a turbo failure. You need flow to make a turbine wheel spin. On my excavator there did not appear to be any point where there were both intake and exhaust valves open at the same time, but even if there were, that is one long tortured path for the air to try to push though.
Engines have tendency of always stopping in a few spots, it would be rare for one to stop at tdc and overlap.
my 2 cents. - I would assume it is not that uncommon to stop on TDC because as the piston comes up to TDC compression stroke it is under max load and the point when the engine would want to stop turning resulting in the running mate being on valve overlap -A lot of the time on Cat equipment the exhaust stack is bigger than the exhaust pipe (Venturi effect) so the air would naturally push into the engine bay and out not down the actual exhaust (path of least resistance) And just to be clear for non T4 engines the path the air would have to go while creating enough flow to spin the turbo -down exhaust -through muffler baffles -past exhaust side of turbo -into exhaust manifold and find a valve on overlap -out intake manifold -through aftercooler -through turbo compressor side -reverse through the air filters …..not likely
It would seem that way--but it aint.
^ trying to bump starter around to set valves is a losing proposition for that reason.
I cover mine, unless it has a rain cap that will be closed the direction I am driving. I’ve heard the oil thing, but was told rocks, kicked up or a bird in there could be an issue. I’ve never seen it, but it only takes a minute or two, so I do it.
I think its not so much the risk of air pushing into the exhaust as the possible venturi effect of the air rushing past the top of the exhaust pulling air out of the exhaust at todays highway speeds combined with pushing into a strong headwind
Back in my heavy towing days in the eighties, whenever we towed a truck into the dealership they would verify that we had the stacks covered. Probably just CYA, for us and them, but the habit stuck with me. After all, what happens when a machine is parked on a jobsite during a 60 mph wind? Really no difference in my mind.
Don’t know if it ever helped but I always did it just so some guy would look at it and say wow that’s a good idea I never thought of that
Well lets see--first off I'm not going to carry a fruit ladder acting like a fruit bum to climb to the top of stacks 13,6. Never happened not going to happen. I tow damn near every thing from the back because I'm not going to lay in water or a truck stop where people have been pi$$ing in the lot to pull a driveline if I don't have to. I tow at 65 mph when I can, given wind conditions, sometimes only 55. Just not going to worry about some damn turbo compressor wheel spinning out of control.
So I am a bit confused. I would have thought, for the turbo to spin it requires airflow. So where exactly is the air flowing through the turbo when the engine is stopped going to? Is the train of thought, air is going to enter the exhaust outlet, go through the muffler, through the turbo, and then go where exactly?
RC, the air potentially goes through the engine via partly open, overlapped valves, then back up the intake and out through the air cleaner. As I said above, in the days of oil bath air cleaners, there was a lot less resistance in the air cleaner for air to take that path - but with dual dry elements, there's nowhere near the same ability to allow volumes of air through.
I believe the odds of catching a bird into the exhaust stack while going down the road is much greater.
I've done that. Not into the stack but smashed against it at highway speed. Bent the damned thing too. Brand new tractor and a hawk eating road kill which is common around here.
My fave is the battery on the concrete thing. The science is just amazing!! How about keep it warm or charged or both?
Dangit Skyking, another myth busted.........I still set mine on a board just cuz!
The discharge thing used to be true but that was back in the days of "bakelite" cases which were not always a perfect insulator. The plastic cases replacing these in the 1940's did away with that but old habits die hard sometimes. I do keep batteries on a float maintainer as do believe they work. Just put a new group 31 in my skid steer yesterday replacing one that was new in August 2016 according to the receipt. The one prior to that battery was an Interstate and new in 2008, and the one prior to that was new in 2000 when I purchased the machine with a bad battery. I don't think with the vibration these things take that is too bad of service life but I do feel the maintainers help to extend this life.
It is that much further up to lift. as you get older use bigger boards. Eventually set it on a chopping block so you don't bend over at all, and for sure get those batteries with the handles on them.
Well the older a boomer gets the handles grow above the belt line and the buckle starts staring at the ground.