Charge Air Cooler

[jack14r]

My last 4 trips have been to the west which means that I have to go through the mountains.I have been getting Detroit Diesel codes that my local service center was not sure was a problem.The last trip there were 2 codes(1) Intake Manif Temp E197 (2)Air Inlet Temp Too High E11.On an earlier trip I actually got a reduction in power for 10 seconds or so.My fuel mileage is down about 1/2 MPG and I have a small amount of black smoke when I depress the accelerator slowly.Kevin at Covington Detroit Diesel in Greensboro,NC found that the Charge Air Cooler is cracked and that the crack has grown.Since this part is a Prevost part and not a DD part and Covington is not a Prevost Warranty Center I had to get Prevost to approve the repair which they did in a very professional manner.Brian Joy from Florida and Lindsey from the Volvo office in Greensboro,NC handled the paperwork and Covington ordered the part,there are none in the USA but it will be shipped from Canada.This cooler on the EGR engines looks to be about 200 pounds and is a huge radiator,hopefully this will cure my problem for good.

[Jon Wehrenberg]

If it was leaking Jack I am surprised it did not affect total boost.

Does your engine have a waste gate and waste gate controller? The reason I ask is if it does then to compensate for the leak the waste gate was closing, making the turbo work harder to compensate for the leak, and that in turn was heating the air beyond limits. Just talking out loud here.

[jack14r]

Yes it does have a waste gate and controller and you are right the turbo had to work harder and produced more heat.

[Jon Wehrenberg]

I guess I have to poke my nose into the engine area of a newer coach to see what magic they employ.

My guess is that wastegate and controller was required to assure full combustion and that is tied into DDEC. What boost do you show?

The small puff of black smoke now makes perfect sense because the leak in the intercooler caused a loss of boost and you saw the results. Somewhat like when I had a turbo inlet pipe break on my 8V92. That impacted the ability of the turbo to pump air the cars behind me were completely hidden by the black smoke I was putting out.

[jack14r]

It does all make sense now the DD guys were stumped for a while,the boost is about 27-28 inches.

[Joe Cannarozzi]

Question is what is it normally and what did it go to when the intercooler was leaking? Should have been less, but wasn't?

[Jon Wehrenberg]

I'll bet the change was both subtle and slight, if at all.

It probably was a fatigue crack that propogated. With a waste gate controller the boost was staying close to normal, if not normal, but because it was working to build pressure the compressed intake air coming out of the turbo was waaaay hot. The reason for the intercooler is to get the air more dense by cooling it, but the intercooler can only get rid of a certain amount of heat, so the intake air charge temp was seen as too high by the sensors.

The net result was there wasn't enough air molecules to complete combustion so Jack saw the puffs of black.

If I had a wastegate and controller on either of my coaches I never found it. I suspect that is an addition required by the EPA requirements and it regulates the exhaust going into the turbo to maintain the intake manifold pressure.

[jack14r]

Apparently the waste gate adjusted for the leak and I never saw any reduction of boost on the gauge.I do think that I noticed a small reduction in performance,but it is almost impossible to really be sure,I had been thinking for awhile that I really didn't have as much power as I thought I should.Looking back to my first trip last July,I now remember that I got the same codes on that trip(it must have been cracked when I took delivery) I remember telling my wife that this coach seemed to have less power than the previous one,I told myself that because it weighed more the performance would be reduced.Prevost shipped the part yesterday and I am looking forward to finally feeling the real performance on my next trip.

[jack14r]

Estes Freight delivered the Air Charge Cooler today and Covington DD will install it on Monday,I will be interested to see if the performance improves.

[rfoster]

Jack: Did you mention your mpg performance? If you did I missed it. Can you post your mpg performance- both before and after.

The reason I ask is my mpg performance last trip dropped to 6 mpg and I noticed a huff of black smoke out of the exhaust when I would accelerate or even hit the resume button on the cruise. I had been getting quite a bit better mileage than that even with a tow, and the last time out I had no tow. The OAT was in the low 90s. And I did not use the gen at all. Power seemed ok.

Thanks in advance.