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Old 04-15-2015, 10:35 AM   #11
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Originally Posted by Booyah45828 View Post
I don't know about that. The 3406 was a pretty great engine, although at 14.5L it'd be overkill for a school bus. I don't think we've had too many problems with 3126 mechanical engines either. However, once cat went to electronic injection, especially their acert program, the engines went to ****.
If it was me if avoid any engine that uses high pressure oil to drive the injectors, it's a good thought on paper but it just doesn't work that well in life.
Man, I would love 14.5 L in a school bus! 6% grades with no issue in the highest gear!

I agree with you on the HEUI systems. I think the main reason they went through with the design is because, since the injection is not cam or pump driven, you can time injection independently of the cam, which can increase power and efficiency while cleaning up emissions. Think of it like distributor advance / retard. You can also control the duration of the injection better as well. The repair manual for my bus specifically brags about how they met 1999 emissions standards without any exhaust emissions equipment while others didn't. I had the issue on mine where an O ring (or more) went and caused the system to dump engine oil into the fuel return. Imagine my surprise when I had the engine running for an hour and it used a gallon of oil with no leaks or smoke. It is relatively easy to fix, but still is a problem other engines just don't have.

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It's like this Lucy. "Supposedly" the synthetic is "harder" to compress then its conventional Dino counterpart. 15w40 Rotella T, arguably the best oil out there for a compression ignition engine, low on detergents. The equivalent 5w40 is of course thinner, but contains a lot more detergents.

So 2 things I'll say here and then I'll sit back while the attacks come, lol: 1st with synthetic, even matching weights, it will be thinner than conventional, your HUEI motors HPOP's regulator runs about 5-10 more than the same motor with non synthetic. The HPOP makes pressure, the regulator decides how much will get to the injectors. So basically the HPOP has to work a little harder to make the same range of pressure.

2nd, have you ever felt black, "nasty" diesel oil in your hands? All that carbon and soot makes it feel like fine ash. Some have argued that this ash in the oil CONTRIBUTES to lubrication. I cannot say for sure personally.

I did take 3 classes back in the day for ford 6.0 repair since I was seeing soooo many in the shop. One consensus among all the instructors was synthetic was terrible for those motors, as we all may know, the 6.0 is a long shot from the 7.3. I've heard a lot of bad stuff about synthetic oil, that it's a leak finder and such, but I still use it in my suby! I've pulled off valve covers at 100k where the valve train was so clean there wasn't a spot of varnish, nothing but conventional oil, and opposite I've done BMW timing chains that used nothing but synthetic at 60k and had to chisel out the sludge and upsell an oil pan removal so I could clean the pickup tube. Now the bmw was doing 10k intervals and the Toyota was doing 5k.

Honestly you could probably use anything, just please be religious about changing it. Oil analysis is good too, use to do that for a fire department. And I always put BG MOA in everything....except for wet clutch motorcycles.

Nothing but love for synthetic BTW.
I ran a blackstone labs oil analysis on the last oil change I did in my motor. I used Rotella T 15w-40 which is conventional. I had 5500 miles on the oil which was a lot of cold idling, mostly highway running but at engine redline at 2400 rpm, and it had overheated on this oil to 220 degrees a number of times. I also installed a new turbo on this oil, and did the injector repair. Despite all this, they said it was good for at least another 3k miles in addition to what I did, and all things considered the wear metals were low even with turbo break in. That convinced me enough that I don't need to spend any more than I do on oil.

A lot of that, I admit has to do with me using CAT OEM oil filters which are probably better (or they say they are). They are $15 each for this motor which is not unreasonable so I will keep using them.

Also, BMW's oil change intervals are nuts. My dad's BMW is set to have it changed at 15k intervals on a turbocharged 3 liter gas engine making over 300 hp. This is an engine known for oil consumption issues too (thanks BorgWarner). They had a TSB where this interval was reduced to 10k miles. My mom's diesel X5 (2014) has 7500 mile intervals which is a bit more reasonable.

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I'll agree on the synthetic part. But I always attributed the problem to the longer oil change intervals when using synthetic than anything actually with the oil. Heui engines NEED clean oil. When you have tolerance levels in microns, you can't use dirty oil to drive them. It just doesn't work. Another thing people don't realize is the shearing effect Heui pumps and injectors have on the oil molecule that seems to take away the lubricity of the oil. I've worked on 3126, c7, c9, dt466e, maxxforce, 7.3 and 6.0 engines and never really seen a difference in reliability between one Heui engine to the next. All I can say is change the oil, change it often, and use good filters.
Agreed. Oil is not "just" a lubricant in this engine, it is used to drive the injection system which (I think) has tighter tolerances than any main bearings would. Also agree with you stressing the importance on changing the filters. Interestingly, CAT says to not fill the oil filter when changing it, but rather just let the engine run dry a few seconds and let it fill itself up so you don't introduce any contaminants by pre-filling it. I feel like if they suggest you run the motor dry over possibly introducing particles, then it is probably pretty important that the oil stay clean

Quote:
hmmm, never thought about the compression thing. makes sense tho. conventional dino oil has more air in it? thats the only thing i can think of, as we all know you cant conpress a liquid. you state the synthetic is thinner, but is that at lower temps? how about once the engine is at operating temp?

the greatest (and imho only real) benefit of synthetic is its ability to remain oil at higher temps. in an average engine that never heats up, i would run dino. in these modern engines that have elevated operating temps to meet epa regs, synthetic is a necessity.

it has been proven that if synthetic never gets overheated, it never breaks down, only dirty. on out skoolie engines, running at 170-180 max, overheating of the oil would not be a problem.
I have always heard people say that synthetic is thinner but I don't know if that is actually proven or not. I will say, in my BMW 325is with the older M20 straight 6, which has a non-hydraulic valvetrain (noisy by nature) that the valvetrain is much quieter running Rotella 15w-40 diesel oil than Mobil 1 15w-50 oil. Not sure if this is due to thickness or what, but I have run Rotella in it since.

Also, my skoolie engine (again, CAT 3126 HEUI) is supposed to run at 195 degrees, and is good to 205 degrees. I don't worry about overheating of the oil since it doesn't specify to use synthetic, and it is running in its normal range, but I am definitely mindful of when to shut off the motor. I.e. if you have just been giving it the beans on the highway, don't pull over and shut it off immediately, as the turbo will be super hot and oil will cook inside it. You are supposed to give it 5 or so minutes after cruising of idling time to let the oil and metal bits cool. I know a lot of people try to shut off the motors as little as possible.

I doubt lack of maintenance is a problem with any of us on here, I for one am neurotic about preventative maintenance. It is more about how these were treated when in service that causes the damage to these motors, and I know some fleets take better care than others, but I have seen some repairs on my bus that made me doubt that my bus regularly saw good upkeep. That being said, the oil analysis came back great and the engine has over 13,500 hours on it. The mileage on the odometer is wrong, but even with a low average speed of 20, that is 270,000 miles (figuring a lot of stop and go and extended idling) and it still runs great.

Sorry for the long-winded response, I just got an adderall prescription and it works.
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Old 04-16-2015, 09:22 AM   #12
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Originally Posted by porkchopsandwiches View Post
I think the main reason they went through with the design is because, since the injection is not cam or pump driven, you can time injection independently of the cam, which can increase power and efficiency while cleaning up emissions. Think of it like distributor advance / retard. You can also control the duration of the injection better as well. The repair manual for my bus specifically brags about how they met 1999 emissions standards without any exhaust emissions equipment while others didn't.
Yep, they went to the electronics for the emissions only not reliability. You're right that it gave them complete control of the injection process, but that was possible before hand. There are/were engines that used mechanical injection with electronic solenoids to fire the injectors. Cummins' ISX and Detroit's Series 60 are examples(there's more, but those are off the top of my head). Hell even the cummins ISB used an electronic/mechanical pump to fire the injectors(electronics changed the timing in the pump vs at the injector). Electronic injection also gave the engine the ability to fire the injector multiple times per engine cycle(multiple little squirts vs. one large one) which also reduced emissions.

The key about HEUI is it allowed the engines to vary the fuel injection pressure. That allows low injection pressure at low power, which quiets the engine down tremendously. At high power, they can increase the pressure beyond that of a mechanical engine, which increases fuel atomization which makes more power with less emissions.

The problem is that 10 years later, Common Rail injection systems came along(more pulses per cycle) which made HEUI technology outdated. And Navistar/Caterpillar just dumped boat loads of money into designing this system, so they couldn't just throw it to the wayside. They tried a few redesigns and they stuck it out until they could no longer meet the emissions with it. The result is Caterpillar quit the business altogether and Navistar partnered with Cummins to use Selective Catalyst Reduiction to meet the new emissions.

That's pretty much where we are at today. Sorry for being so long winded, and I hope I didn't derail the thread or lose anybody.
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Old 04-17-2015, 01:27 AM   #13
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Quote:
Originally Posted by Booyah45828 View Post
Yep, they went to the electronics for the emissions only not reliability. You're right that it gave them complete control of the injection process, but that was possible before hand. There are/were engines that used mechanical injection with electronic solenoids to fire the injectors. Cummins' ISX and Detroit's Series 60 are examples(there's more, but those are off the top of my head). Hell even the cummins ISB used an electronic/mechanical pump to fire the injectors(electronics changed the timing in the pump vs at the injector). Electronic injection also gave the engine the ability to fire the injector multiple times per engine cycle(multiple little squirts vs. one large one) which also reduced emissions.

The key about HEUI is it allowed the engines to vary the fuel injection pressure. That allows low injection pressure at low power, which quiets the engine down tremendously. At high power, they can increase the pressure beyond that of a mechanical engine, which increases fuel atomization which makes more power with less emissions.

The problem is that 10 years later, Common Rail injection systems came along(more pulses per cycle) which made HEUI technology outdated. And Navistar/Caterpillar just dumped boat loads of money into designing this system, so they couldn't just throw it to the wayside. They tried a few redesigns and they stuck it out until they could no longer meet the emissions with it. The result is Caterpillar quit the business altogether and Navistar partnered with Cummins to use Selective Catalyst Reduiction to meet the new emissions.

That's pretty much where we are at today. Sorry for being so long winded, and I hope I didn't derail the thread or lose anybody.
Thanks for the history lesson! I didn't know all of that. Again, I like the HEUI system but it adds a hell of a lot of things that can go wrong. The bus never smokes, maybe a puff on startup if I haven't run it in a while, and is halfway decent on fuel, and not absurdly noisy. But yeah, I have encountered the problems that come with a poorly maintained one (and one with over 13,500 of hard hours on it) and it is not fun.
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Old 07-10-2015, 01:21 AM   #14
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Porkchopsandwiches - Did you buy yours directly from Montgomery County? I bought #8895 (2000 MVP ER), but it was owned by a local company, ATS for a short time before winding up in an auction in Denver. Pretty sure ATS didn't do any maintenance to it that wasn't absolutely required. Just curious if there's anything I need to pay particular attention to.

Thanks in advance!
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Old 07-13-2015, 12:03 AM   #15
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Porkchopsandwiches - Did you buy yours directly from Montgomery County? I bought #8895 (2000 MVP ER), but it was owned by a local company, ATS for a short time before winding up in an auction in Denver. Pretty sure ATS didn't do any maintenance to it that wasn't absolutely required. Just curious if there's anything I need to pay particular attention to.

Thanks in advance!
Correction: Bus #9985
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Old 04-18-2016, 01:29 AM   #16
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Jeebus sorry for the late reply haha. No I bought it from a middle man in MD who bought it from auction. They didn't do anything to it nor provide any sort of documentation, and if you read my build thread, I paid the price. haha.
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Old 04-18-2016, 01:39 AM   #17
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Jeebus sorry for the late reply haha. No I bought it from a middle man in MD who bought it from auction. They didn't do anything to it nor provide any sort of documentation, and if you read my build thread, I paid the price. haha.
No worries. I ended up selling my Thomas. It had a slow 3-4 shift and wasn't engaging TC lock-up.

I ended up getting a 98 Blue Bird with a Cummins 8.3 and a hydraulic retarder to boot. Worked on it like a mad man for two weeks, then drove it to Burning Man. 2300 miles, give or take.
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Old 07-18-2016, 10:51 AM   #18
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thickness

One common misconception about Synthetics is its not thinner, a registered weight such as W40 has to be the same thickness or viscosity by regulations. Synthetic only seems thinner or finds leaks better because it simply is a better more perfect product that is more slippery, or better phrase would be a higher lubricity rating. Learned this from having a conversation with an oil engineer from shell. Plus viscosity is a measurement of oils ability to flow not be compressed, that would be something else I guess
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Old 09-04-2016, 12:51 PM   #19
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Seriously. Just don't. Get something with a Cummins or DT466 or T444e or anything else. Thanks. PM me with any questions.
Why hide behind private messaging?
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Old 09-08-2016, 09:00 PM   #20
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