Turbo failures
11-02-2002, 09:05 AM
#1
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Turbo failures
I am an S4 owner concerned about my turbos. I hang out on the S4 forum where I hear about failures, and I know personally several owners who have blown them. Yet there are owners who have extensive mods and who race their cars with stock KO3's that never had a problem. Never has there been an adequate explaination on the S4 forum for the failures, so I thought I'd post over here where the technically savy owners of previous generation cars hang out.
My pet theory is that running lean on sustained high boost, resulting in high exhaust temperatures, can destroy a turbo, especially a KO3 pushed to it's imits by aftermarket software. That could be caused by faulty ecu software, bad injectors, or maxed out injectors. Any thoughts?
My pet theory is that running lean on sustained high boost, resulting in high exhaust temperatures, can destroy a turbo, especially a KO3 pushed to it's imits by aftermarket software. That could be caused by faulty ecu software, bad injectors, or maxed out injectors. Any thoughts?
11-02-2002, 12:32 PM
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Maybe it's still a lean problem, even stock?
Even with stock boost I would think a lean mixture could kill the turbos if driven hard. That could be caused by other than inherent turbo problems.
11-02-2002, 12:33 PM
#4
Re: Totally stock S4's have lost one or both turbos too. A few within the break in period.
I think it has more to do with how the owner drives the car during its "warm-up" period. Gotta let things get up to operating temp before you beat on them. Also, cool down on a turbo is very important. The old 10vt and 20vt cars with water cooled turbos have auxilary water pumps (electric) that will come on after the car is shut down (along with the elec. fan on the radiator) if temps are too high. It will cycle until the temps are low enough. Heck, the CIS turbo cars even have an elec. cooling fan system for the injectors.
Why Audi stopped doing this with the water cooled turbos is beyond me.
Why Audi stopped doing this with the water cooled turbos is beyond me.
11-02-2002, 02:35 PM
#7
Re: One stock car that I am familiar with was ALWAYS properly warmed and cooled. I thought the S4 ha
item #13, part # 078 965 561 additional water pump...so it seems that the B5-S4 does have an after run system, or at least an aux. electric water pump. This brings up, why can you get a similar pump on the 2.8 30v, but not the 1.8t, from the factory?
The fan I believe is still a hydraulic/mechanical drive unit on the B5-S4 (vs elec. of the older cars) so the radiator would be of not much use when the car is switched off. What use is circulating hot coolant around if you don't have air moving over the radiator to cool the fluid? Sounds like people should be doing the electric fan upgrade, and tieing it into the after run system.
Another thing to think about, is how has 3K's manufacturing/quality changed from then to now? I have really only heard about turbo failures from high-mileage units, or the old oil-only units as found on the early 5kt's and urq's. Also, knowing what the engine bay looks like in an A4tq, I'd have to believe that the B5-S4 would offer less empty space around the turbos for adequate air-cooling.
Lots of variables to isolate.....
The fan I believe is still a hydraulic/mechanical drive unit on the B5-S4 (vs elec. of the older cars) so the radiator would be of not much use when the car is switched off. What use is circulating hot coolant around if you don't have air moving over the radiator to cool the fluid? Sounds like people should be doing the electric fan upgrade, and tieing it into the after run system.
Another thing to think about, is how has 3K's manufacturing/quality changed from then to now? I have really only heard about turbo failures from high-mileage units, or the old oil-only units as found on the early 5kt's and urq's. Also, knowing what the engine bay looks like in an A4tq, I'd have to believe that the B5-S4 would offer less empty space around the turbos for adequate air-cooling.
Lots of variables to isolate.....
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11-02-2002, 04:06 PM
#10
Re: One thing to remember about the afterrun pump:
Yes, but what is the hot coolant temp after running thru that hot turbo? The cool down time will be greatly increased w/out airflow over the radiator (ever take a thermodynamics class?).
Running a fan in conjunction with the pump would be best. Why run the coolant through a nice air/water heat exchanger if you aren't going to pass air over the H.E.?
Running a fan in conjunction with the pump would be best. Why run the coolant through a nice air/water heat exchanger if you aren't going to pass air over the H.E.?