Turbo

Topic: Turbo (Read 677 times) previous topic - next topic

Turbo

July 05, 2022, 05:18:26 pm

Last year the turbo wasn't working at times. No pattern, so Andy2 came over with his test box and pronounced the sensor/controller device bad. I went to NAPA and bought a replacement. Tested good, but still a few intermittent issues. Andy brought his box again and pronounced the new sensor was good, but there were intermittent connection issues. That was also my guess, so I bought a genuine GM part ($200) and put it in. Not a hiccup today!

On to the next problem!

Re: Turbo

Reply #1 – July 06, 2022, 12:26:50 am

I've had suspicions that my turbo isn't quite right.
Other things on my table right now but I'm thinking a test on freeness (does it spin) and a lack of wiggle on the bearings would be the extent of my testing ability.
Are they hard to obtain/replace?
Bolt off/bolt on.
How idyllic am I being?

Re: Turbo

Reply #2 – July 06, 2022, 01:03:07 am

Turbos are relatively cheap. Easy to R&R if you don't run into rust/corrosion on the fasteners. One broken bolt can add a lot of time to an easy and fast job. Best to use a good penetrating fluid or make some like Brett made up. 50/50 acetone and ATF.

Check the model you need and then look it up on ebay plus Google searches. Prices may be quite a bit different for the same turbo..

Poor performance may not be the turbo but may be the intercooler/CAC faults or restriction in the exhaust system. Low fuel pressure from filters/air in fuel system can also limit boost. Also check the air cleaner. Unless you see damage on the vanes or bad bearings, look to the other possibilities. Boost pressure should be somewhere around 20 psi.

Depending on the engine, make sure the turbo and exhaust clamps are secure as one member had a clamp come off after a shop did turbo work and the exhaust started the engine compartment on fire. No trick to install one but haste makes waste.

Pierce

Re: Turbo

Reply #3 – July 06, 2022, 01:14:19 am

Pierce,
More questions now.
WTH is a "CAC"?
Had fuel/air filters replaced with no change in performance.
Went up Wolf Creek Pass towing the passat and it was torture. Slow speed and engine getting hot.

Funny about the exhaust side coming off.....
Mine came off half way up Killington Mtn. Ended up melting a bunch of my brake hoses. THAT was a long night.

Re: Turbo

Reply #4 – July 06, 2022, 01:36:18 am

Quote from: Moby – July 06, 2022, 01:14:19 am

WTH is a "CAC"?

When air is compressed it heats up.
A CAC is a radiator that cools the hot compressed air coming from the turbocharger, before it enters the intake manifold. The cooling increases the density of the air entering the intake manifold.
Other names for a CAC are: intercooler and aftercooler.
Tim

Re: Turbo

Reply #5 – July 06, 2022, 03:04:29 am

Moby,check/make sure your Cac and radiator are clean,can be blown out with air and/or a water hose.

Re: Turbo

Reply #6 – July 06, 2022, 04:10:43 am

Quote from: John44 – July 06, 2022, 03:04:29 am

Moby,check/make sure your Cac and radiator are clean,can be blown out with air and/or a water hose.

Done last year and no improvement noticible.
Used simple green and garden hose from outside.
Hmmm...... hit with cleaner from INSIDE?
Simple stuff first, right?

I've complained that I feel she's underpowered, but here's a question;
I've got the baby GV, with the smallest engine. Is having issues going up Wolf Creek Pass to be expected while towing a Passat, or am I over reacting as I sometimes do?

Re: Turbo

Reply #7 – July 06, 2022, 05:14:20 am

Some with the same setup will chime in,may not be feasible but can you try going up a pass without towing the car,let someone drive the car and see if that gives you more power and less overheating.Have rebuilt hundreds of turbos,the vanes should spin freely,hard to describe but there should be some end play but not much.Try putting some fuel additive in to boost the cetane,won't hurt to try,use the maximum amount.

Re: Turbo

Reply #8 – July 06, 2022, 09:51:13 am

Quote from: Moby – July 06, 2022, 04:10:43 am

I've complained that I feel she's underpowered, but here's a question, I've got the baby GV, with the smallest engine. Is having issues going up Wolf Creek Pass to be expected while towing a Passat, or am I over reacting as I sometimes do?

Hard question for anyone to answer with certainty. So many variables to cloud the picture. I can only think of two ways to get a truly objective answer.

You could compare your coach's performance to another identically loaded/equipped coach, pulling the exact same weight, up the same hill, on the same day, under the same atmospheric conditions. What are the odds of that happening?

OR, you could put your coach on a chassis dyno and test the performance of the engine. See if your engine makes the rated horse power and torque. I know dynos are available for motorhomes. I don't know offhand where you would find one.

Otherwise, you can only get subjective answers to your question. You could try to find comparisons of the performance of your coach to other similar model motorhomes. Your B5.9-230 engine was rated (I believe) at 605 lb-ft @ 1600 rpm. Do you have the Allison MT643 4-speed transmission or the MD3060 6-speed? A quick Google search revels that many contemporary 1993 SOB motorhomes came with the 6-speed. More gears is nearly always better when pulling heavy weight. You are pulling a Passat + tow dolly. That combo probably weighs around 4000 pounds. You can search for reports on this Forum or other RV forums from owners with similar coaches pulling similar weight. See if they are happy with how their coach performs.

Re: Turbo

Reply #9 – July 06, 2022, 09:53:30 am

The U225 had the mechanical Cummins B 230 HP and Allison mechanical 4 speed.

Only the U240 and "higher" had the Allison 6 speed. And, yes, 1993 was the transition year from 4 to 6 speeds in the "higher" models.

And, agree with Chuck-- way too many things can degrade performance for us/you to guess. But, start with the basic PM items:

New fuel filters.
Check fuel lines for cracks that will allow air in.
Air cleaner filter minder in green and filter not over 3 years old.
Front of CAC clean, particularly the lower perimeter where dirt accumulates.
Check all boots from turbo cleanside outlet to CAC and CAC to engine intake manifold.

Re: Turbo

Reply #10 – July 06, 2022, 10:37:05 am

So, the intercooler (CAC) is just a radiator but instead of having coolant in it, it has compressed air from the turbo in it. The turbo is hot from the exhaust and the law of compressed gases shows us that when air is compressed, it gets hot. This is how a compression ignition diesel works.

So, the intercooler may have a crack in it allowing the pressure to escape, a clamp could be broken or missing, it could be dirty.

Here is the other problem. You have the smallest diesel fitted to a Foretravel at 5.9 liters. Going up a grade with your coach and a toad will be slower than a coach with a 8.3, 10.8 or Detroit 9 liter. Because of the slow speed, you may not be in torque converter lock up and because of this, the transmission temperature will go up. It is partially controlled by the heat exchanger but this also puts a load on the engine cooling system.

Anytime you are at high altitude, the engine will have less power so uphill speeds will be slower. In summer, this is compounded by high temperatures at high altitudes. You may go over a grade summit at 8000 feet on the road marker but in hot weather, the "density altitude" may be 10,000 or 12,000 feet. This is the altitude your body and your coach think it is. Just as your lungs can't get as much oxygen because the air is less dense, the radiator, the radiator fan, the turbo, the engine all have less dense air to cool and produce power. You can quickly see that the high altitude and especially a high density altitude, will slow the coach going up grades, require a lower gear that may not be in transmission lockup, and all the cooling components will be much less effective.

Even with a wastegate on the turbo, the engine will reach a "critical altitude" where it will no longer produce sea level horsepower.

High density altitude kills many pilots each year and while our coaches don't have to worry about taking off, most owners have no idea what high altitude and hot weather will do to their RV. Just think about hiking uphill in Yellowstone. At 8000 feet, it's hard enough in fall or spring but summer makes stops to rest more frequent. Plus, you have to take off more and more clothing to stay cool.

Pierce

Re: Turbo

Reply #11 – July 06, 2022, 11:03:46 am

Thanks for all the very worthwhile suggestions!

Re: Turbo

Reply #12 – July 06, 2022, 11:31:17 am

If you have the Cummins B engine the fuel shut off solenoid can lose effectiveness when the rubber boot degrades and gunk builds up on solenoid piston. With key on, engine off see if it is traveling to its maximum length.

Get the app for CAT scale and get a three axle weight with full fuel in toad, full fuel in coach, fully loaded for travel, all passengers aboard, and carrying your customary fresh water load. This will give you your GVW and CGVW. Compare those to your placard by the driver seat. It's tempting to use the toad for extra storage and you might be surprised by what it weighs. That will give you a good idea how much load you can remove in a hot, high pass by off loading toad. In Camaroon Africa it was common to see passengers walking behind a Toyota Minivan that was horribly overloaded going up a steep hill.

Re: Turbo

Reply #13 – July 06, 2022, 03:40:09 pm

I think if one looks deeper, Simple Green can damage aluminum in radiators and charge air coolers (inner cooler/ turbo coolers). We use a Simple Green product made to be safe for aluminum...

Simple Green | Frequently Asked Questions

Re: Turbo

Reply #14 – July 06, 2022, 03:41:50 pm

Simple Green EXTREME is aluminum friendly and is what you should use.

Re: Turbo

Reply #15 – July 06, 2022, 03:48:34 pm

I pull the hard hills at night . Everything works better in the cool night air .

Re: Turbo

Reply #16 – July 06, 2022, 04:34:38 pm

So lots of variables. Chuck is correct in that a base line power run on a dyno will show current status and can document any improvements. Washing the intercooler out is great but you must visually see what is between them. I had no clue about the amount of blockage and it was not visible till disassembled. Failing CAC certinally can cause low power but also fin rot on the inside. Also need to get a baseline on boost output before you start throwing money at the problem. May be a control issue rather than a failing turbo or bad CAC. Resulting in a cheap repair.
Scott

Re: Turbo

Reply #17 – July 06, 2022, 10:35:15 pm

Scott, when I replaced my CAC it was leaking really bad at bottom when I pressured it up. I tried aluminum solder and the holes started growing so I went to a aluminum epoxie and didn't like the results, SO 2 coach bucks later and about 8 to 10 weeks wait
I installed a new CAC and we keep marching onward!! that was in 2019 so there is no telling what it cost now.
Chris

Re: Turbo

Reply #18 – July 06, 2022, 11:21:52 pm

Quote from: Chris m lang – July 06, 2022, 10:35:15 pm

Scott, when I replaced my CAC it was leaking really bad at bottom when I pressured it up. I tried aluminum solder and the holes started growing so I went to a aluminum epoxie and didn't like the results, SO 2 coach bucks later and about 8 to 10 weeks wait
I installed a new CAC and we keep marching onward!! that was in 2019 so there is no telling what it cost now.
Chris

Fourdayoff Jim just replaced his 3k. Ouch.

Re: Turbo

Reply #19 – July 07, 2022, 12:09:19 am

When I needed a new CAC I went to a rad shop and they welded a new core in for half
the price.

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