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Old 10-29-2020, 07:00 PM   #1
Mini-Skoolie
 
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How loud should a turbo be?

Theres a consistent high pitch whistling while Im driving at highway speeds varying frequency depending on how much Im on the throttle. It seems to cutout above 3000+ rpm. I have a rear engine 8.3l and inside the bus is completely stripped down to the metal floor currently so there isnt much to insulate from sound.


I bought this recently and checked my air filter because I was loosing power uphill. Literally piles of dust/dirt came out of it so I banged it around the best I could to get as much out as possible and put it back in for now. Its one of those big cylinder filters where you have to replace the entire thing and theyre fairly expensive.


"Cleaning" it seemed to help slightly on hills, but maybe it was just my hopeful bias. It did make the engine run cooler tho. I also tightened all the hoses to and from the turbo. Next on my list was to check the AFC. Ive replaced the fuel filter already, but not the fuel/water seperator. At 65mph my rpm is 2700-3000. That sound about right? Should I not push the engine that much?



Is this normal to be able to hear from the driver seat? Would a dirty air filter make a turbo louder? It says not to clean and reuse the filter on it, can I? lol. Is running it without the filter and taking a short drive a bad idea? What exactly am I looking for after I disconnect the AFC tubing?
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Old 10-29-2020, 08:09 PM   #2
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Theres a consistent high pitch whistling while Im driving at highway speeds varying frequency depending on how much Im on the throttle. It seems to cutout above 3000+ rpm. I have a rear engine 8.3l and inside the bus is completely stripped down to the metal floor currently so there isnt much to insulate from sound.

I bought this recently and checked my air filter because I was loosing power uphill. Literally piles of dust/dirt came out of it so I banged it around the best I could to get as much out as possible and put it back in for now. Its one of those big cylinder filters where you have to replace the entire thing and theyre fairly expensive.

"Cleaning" it seemed to help slightly on hills, but maybe it was just my hopeful bias. It did make the engine run cooler tho. I also tightened all the hoses to and from the turbo. Next on my list was to check the AFC. Ive replaced the fuel filter already, but not the fuel/water seperator. At 65mph my rpm is 2700-3000. That sound about right? Should I not push the engine that much?

Is this normal to be able to hear from the driver seat? Would a dirty air filter make a turbo louder? It says not to clean and reuse the filter on it, can I? lol. Is running it without the filter and taking a short drive a bad idea? What exactly am I looking for after I disconnect the AFC tubing?
I recently transported a similar rig from IA to PA and I could not hear the turbo. It sounds like the wastegate is stuck closed and causing overboost. So that's one mystery probably solved. You can boost a diesel silly within reason, but I can't vouch for the transmission being able to take the extra power. Over time it can destroy the head gasket as well.

Another possibility is that some dirt finally made it past the filter and into the turbocharger. Hopefully not, but if that is the case, the turbo may actually not be doing anything but spooling up, creating no boost. Does the engine blow smoke? That's a common sign of a bad turbo.

Replacing the water/fuel separator is not necessary, you only need drain the water off using a built-in drain valve in the bottom. The water is heavier than diesel, so it will drain right out the bottom harmlessly, just remember not to drain any unnecessary fuel, and do not let it drain completely to empty.
Cummins 8.3 is rated for 2750 rpm, I would not push it further. I kept the one I was transporting at around 2100-2200, as high as I dare to push a diesel, and only if the manufacturer says it is okay. They're most efficient around 1500-1700 though.

Something else to know about the 8.3. It requires a high-zinc content oil for longevity of engine parts. It is also known for valvetrain problems resulting from camshaft wear at about 9,000 hrs of engine run time, regardless of mileage. So find out your engine hours and make appropriate arrangements if / when the time comes. Hopefully yours was already taken care of before you got it, but don't count on it.
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Old 10-29-2020, 08:50 PM   #3
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Aw jeez, I just made a 2000 mile trip steadily at about the max rated rpm on the highways. I feel like at 2100 rpm Id be going dangerously slow on those 80mph speedlimit roads or even 70mph limit sections and just pissing everyone off. I did use my hazards on hill climbs, but maybe I should just keep them on the entire time lol. Luckily I changed the oil and filter before the trip with the15w40 Chevron Delo 400 SDE CK-4/SN which I was told at napa is what I wanted when I asked about high zinc oil, so hopefully that helped her handle the stress ok.


There isnt smoke from what Ive noticed at idle or driving, but if I get it revved up while parked it does blow some blue smoke Im pretty sure. I was thinking the piston rings might be sticky, but Im no professional.


Is the wastegate easy to access?
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Old 10-29-2020, 09:25 PM   #4
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Aw jeez, I just made a 2000 mile trip steadily at about the max rated rpm on the highways. I feel like at 2100 rpm Id be going dangerously slow on those 80mph speedlimit roads or even 70mph limit sections and just pissing everyone off. I did use my hazards on hill climbs, but maybe I should just keep them on the entire time lol. Luckily I changed the oil and filter before the trip with the15w40 Chevron Delo 400 SDE CK-4/SN which I was told at napa is what I wanted when I asked about high zinc oil, so hopefully that helped her handle the stress ok.


There isnt smoke from what Ive noticed at idle or driving, but if I get it revved up while parked it does blow some blue smoke Im pretty sure. I was thinking the piston rings might be sticky, but Im no professional.


Is the wastegate easy to access?
I haven't actually worked on a Cummins so I couldn't say for sure, but the wastegate is basically a blow-off valve designed to limit boost pressure, so it should be somewhere around the turbo, I would think.

Blue smoke can be indicative of bad turbo oil seals, which should be professionally diagnosed ASAP. When they go bad completely, the engine can run away on its own oil and rev itself silly until it explodes or seizes from running out of oil.

Your bus probably has the Allison MD-3060 transmission, which is a double-overdrive six-speed, but most skoolies have sixth gear locked out. It may be possible to get the sixth gear unlocked to increase cruising speeds at reduced engine rpm.

The alternative for the moment would be to take secondary highways with lower speed limits to keep your cruising RPM down, or maybe later you can have the rear axle gearing changed to something more highway-friendly. Highway friendly is higher gearing, which is numerically lower.

These beasties weren't really meant to go fast -- they are 12,000 lb flying bricks and you should know that yours will likely need about 500 feet or more to stop at 55-60.
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Old 10-29-2020, 10:04 PM   #5
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Mine is audible from the driver seat when we drove the bus during a test drive. Its one of the reasons I had to have the 8.3! I would imagine with a stripped out interior the sound will resonate. That is a fairly large turbo and not much if any insulation to stop the sound from reaching you. At least you won't have to add an aftermarket exhaust whistle to make pretend sounds of a turbo!
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Old 10-29-2020, 10:26 PM   #6
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After I replaced my Racor Eco-BC air filter (the big one-piece canister that cannot be disassembled) a few years ago, I immediately noticed that my engine had more power and the turbo whistle was louder. According to my Filter Minder gauge the present air filter is now approaching replacement time, so I'll buy another two filters and keep one as a spare "just in case". However, since building the bus's interior, with three divider walls on each side, the engine as a whole is now almost inaudible at highway cruising speed, and I can't hear the turbo as easily as before.

One of the most useful gauges that I added was a turbo boost gauge: I now know exactly how hard the engine is working and how much fuel it's burning, and therefore how much heat it's producing. This gauge is not only very useful when climbing long grades in hot weather, but it will also tell you if the turbo is beginning to go tits up on you or otherwise show imminent signs of carking. Forewarned is forearmed! (One can never have too many gauges.)

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Old 10-29-2020, 10:44 PM   #7
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Nice, I didnt know boost gauges were a thing. Definitely something Id be interested in. I wish I had a dashboard with a gauge for everything.
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Old 10-29-2020, 10:53 PM   #8
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Certain Blue Birds have a multicluster with one display through which you toggle which information is displayed. Not a fan honestly.
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Old 10-29-2020, 10:59 PM   #9
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Ya it has the Allison 3060 without 6th unlocked. I hear bluebird is not to eager on letting it be unlocked tho?
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Old 10-29-2020, 11:01 PM   #10
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Ya, the multifunction gauge. I started another thread today in electrical about it being a little b*tch.
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Old 10-29-2020, 11:09 PM   #11
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I think in your case it may be allowable. The bus is dangerously slow at acceptable RPMS on the highway. You may be able to find someone who can do it on the down low without bothering with Blue Bird. Doesn't hurt to ask.
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Old 10-29-2020, 11:33 PM   #12
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Whats the deal with having to have BlueBird's permission to unlock your tranny?
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Old 10-30-2020, 12:12 AM   #13
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Liability, for starters. I'm pretty sure that's the whole reason. They don't want responsibility for one of us rolling over in a curve at 70 mph, running through someone's house, or crushing ten cars because we couldn't stop in time. Pretty sure this can be countered by being unsafe on the higway due to inability to maintain the speed of traffic, though. Personally, I'm thinking of learning how to do it.
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Old 10-30-2020, 12:33 AM   #14
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Liability, for starters. I'm pretty sure that's the whole reason. They don't want responsibility for one of us rolling over in a curve at 70 mph, running through someone's house, or crushing ten cars because we couldn't stop in time. Pretty sure this can be countered by being unsafe on the higway due to inability to maintain the speed of traffic, though. Personally, I'm thinking of learning how to do it.
That would be like suing Ford because some 16 year old drove their F-250 at 90 mph and crashed into 5 other vehicles. The defense in court would be along the lines of "This vehicle was purchased second hand and then used in a manner that it was not designed and built for.... bla bla bla"
I see your point but why would we need Blue Bird to do this at all? Is the ecm code locked and only Blue Bird has the code? I would think it's like the trucking industry where the code from the factory is the vehicle vin until the purchaser changes it. Anyway I am rambling now so it must be getting close to bedtime for me.
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Old 10-30-2020, 12:45 AM   #15
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yeah, I am going to have to go through other channels to get my TCU programmed enabling 6th gear.
My melatonin pill is kicking in. Time for bed for me too!
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Old 10-30-2020, 07:17 AM   #16
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I also have the rear engine 8.3. When it was bone stock on my trip home and I could hear it quite distinctly.

Cheese- what ppm zinc do you suggest for these engines? Would you suggest a break in oil or zddp additive or a brand with already high zinc? I frequent bobistheoilguy a lot and the virgin analysis of the shell T6 looks good, what do you think? If you like this kind of stuff I also suggest the Blackstone labs podcast about used oil analysis.
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Old 10-30-2020, 07:37 AM   #17
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use the 3rd party that is mentioned in the allison unlock thread. no permission required and havent heard any horror stories from their work..



essentially they load an allison program from an identical transmission into yours that has 6th unlocked .. ive done a few that way and it works great..



as for the turbo some engi9nes you hear them more than others.. if there any tiny exhaist leak before the muffler you'll really hear the whistle.. or if the gutted bus has the inside hatch just ajar a little then you'll hear the turbo.. the cummins 8.3 and the Cat C7 both have neart sounding turbos..



the whistle is fine.. if it turns into a squeal or a raspy / whiny sound then its time to inspect it physically.. its not a bad idea to periodically check your turbo anyway for damage to the compressor wheel and for end play (side to side and back N forth) movement of the shaft..



-Christopher
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Old 10-30-2020, 08:28 AM   #18
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I also have the rear engine 8.3. When it was bone stock on my trip home and I could hear it quite distinctly.
Guess my hearing isn't all that great, all I heard was differential gears and tires. Of course, I was on mostly level ground with the cruise set at 70, running about 2100-2200. Turbo probably wasn't spooling much. Windows weren't open either, as I have severe asthma and allergies.

Quote:
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Cheese- what ppm zinc do you suggest for these engines? Would you suggest a break in oil or zddp additive or a brand with already high zinc? I frequent bobistheoilguy a lot and the virgin analysis of the shell T6 looks good, what do you think? If you like this kind of stuff I also suggest the Blackstone labs podcast about used oil analysis.
It actually depends on the application and emissions equipment. Here is a TSB I downloaded.

Service Bulletin Cummins® Engine Oil and Oil Analysis Recommendations
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Old 10-30-2020, 09:24 AM   #19
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Your tach must be wrong. I highly doubt an 8.3 is turnin 3000 rpm.
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Old 10-30-2020, 09:32 AM   #20
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Your tach must be wrong. I highly doubt an 8.3 is turnin 3000 rpm.



if it was you'd definitely hear the turbo!!!
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