CAT C9S engine air to air aftercooler isses

[George Curry]

Does anyone know the story on where this issue stand between Monaco, Midine and Navistar? Cat has studied a Contessa and determined that the A2A after-cooler was undersized for this application and the air restrictions on the air intake. What model years are affected?  Have a call into Beaver Tech.

GEC

[Gil_Johnson]

I and many others are tracking this issue.  My coach was one used for testing. A replacement ATAC (CAC) was installed in a coach on the west coast with good results.  CAT is saying it's Monaco's responsibility.  That's easy to do when he old Monaco does not exist.  I'm confident that this is CAT's issue when engine manufacturers always approve the OEM design and finished product.  Anyway, I'm giving CAT a bit longer to replace mine.  Given mine was a test unit, I would not be happy if they come back and suggest they aren't covering the replacement.  BTW, the excess restriction is unknown as CAT won't say what was acceptable.  I do know that it has virtually no restriction up to about 2,000 rpm and then only 2 psi of restrictin at WOT.

This affects all 08 and newer Beavers with the C9S engines and I'm told Country Coaches with the same engine.

BTW, I"ll be writing a letter to CAT's CEO if CAT doesn't do right.  I" m sure he is a busy guy given how poorly CAT has performed in the market in the last few months.  Many of us have been involved with CAT and the problems they have had with constant low intake pressure alarms and high failure rates on turbos.

Gil
08 Contessa

[John Schenk]

This is my first attempt at posting a reply in a forum.
I bought my 2009 beaver contessa 3 months ago , we are really enjoying the coach.
At the moment it has been at a Cat dealer for two weeks dealing with an " engine light problem , they innially replaced a fuel pressure sensor ( very hard to get at ) which did not solve the issue even though it was not functioning properly. They are now replacing the fuel pump with an updated version, hope this fixes the problem. ( little discouraging since the unit is new with only 5400 miles.)
I would appreciate some clarification on the air to air aftercooler issue , don't understand the terminology ATAC WOT etc. is this something I need to worry about ?

JOHN SCHENK

[Sean Donohue]

Ditto

[LEAH DRAPER]

GIL, JOHN AND OTHERS

Could you please use language that doesn't seem to use so many abbreviations such as BTW and others.  Many of you may be into "texting" but for those of us who are not sauvy to this language, I have not been able to figure out what you are talking about.

Would really appreciate this being a 75 yr old female.
Thanks.

[Gerald Farris]

Maybe I can help a little here. The issue with the ATAC (air to air cooler) is that if the cooler is functioning properly, it will cool the intake air as much as possible between the turbocharger and the intake manifold without a restriction that will lower the boost pressure to the engine. An undersized ATAC will decrease the amount of air available to the engine for the combustion process, especially at WOT (wide open throttle).

A diesel engine needs large volumes of air to function efficiently, and since the density of air increases as it is cooled, the ATAC is needed to cool the air as it comes out of the turbocharger that increases the pressure and temperature of the air. An efficient ATAC will increase the amount of air to the engine intake manifold without any exhaust backpressure to decrease engine efficiency. So it is like free turbo charging.

The issue with CEL (check engine light) issues on the coaches that are suspected of having an undersized ATAC is that a restrictive ATAC will cause the the engine electronics to sense the boost pressure that is lower than it should be and turn on the CEL with a code for a defective turbo.

Gerald

[LEAH DRAPER]

Gerald
You are the greatest!  
Thanks so much for using "english" language that understandable, at least by me.  Very good explanation that is understandable to a non-mechanic lay-person.
Thanks again.
Leah

[Paul Schwalen]

Gerald,

Also, thanks for the lesson on abbreviations. My question for you is: is the CAC (charge air cooler) the same as the ATAC (air to air cooler)? My engine is a Cummins and I had to have the CAC replaced a couple of years ago and am wondering if it is in fact the ATAC you are talking about.

Paul

[Gerald Farris]

Paul,
Yes the CAC (charge air cooler) and the ATAC (air to air cooler) are different names that refer to the same part. The same part is also sometimes referred to as an intercooler or aftercooler. All of the names refer to a heat exchanger that is used to cool the compressed air after it leaves the turbocharger. However, all charge air coolers are not air to air coolers, because they are sometimes air to liquid coolers, especially in the marine industry. But they are always air to air in motorhomes.

Gerald  

[Dick Simonis]

Speaking of the CAC, what should the intake temp be with a properly functioning unit??  Also, what would one expect to see for turbo boost on Cat engines??

[Gerald Farris]

Dick,
I am sorry that I can not give you a simple answer to your question. The intake temperature will vary widely with the ambient temperature and boost pressure. Also, there is no maximum boost pressure for all Cat engines. However, there are maximum boost pressures that are programmed into the software, that operates the engine. All models of Cat engines operate at a different maximum boost pressure.

Most C12 engines will run about 24 PSI at WOT (wide open throttle) at 2100 RPMs, where as the C13 will run about 58 PSI under the same conditions.  

CAC (charge air coolers) are sized to the original installation by two factors. First, it must offer virtually no restriction to the amount of airflow that the engine is expected to need. Second, the cooler must have enough surface area to dissipate the projected heat load. That is what engineers are paid to do. The problems arise when the engineers are restricted in physical size, by the design people that think that a particular product will look better with a smaller grill area, or by the accountants (bean counters) who demand a certain price point.

The guy sitting in the front office is expected to solve these conflicts, unfortunately, it does not always happen to the benefit of the product. Therefore, the new owner ends up with a product that underperforms expectations.

Gerald