- Joined
- May 26, 2001
For years I have been telling people about the benefits of the Ported S cover on any turbo upgrade larger than the normal TA and E cover equipped turbos. Aka 6262 and up. The stock turbo typically does not suffer bad surge, although you can force it to surge under certain conditions. What the others have said about the sounds you are hearing under decel are correct. That horse winny sound is normal and made much louder with a K&N cone filter on the MAF sensor. That's not surge. The TA-49 and TE-44 turbos can suffer from terrible surge under part throttle conditions. When I got my current GN, it had a brand new TE-44 on it and with this combo, it would surge like a mofo. The trick is learning what boost number surge starts under part throttle to keep it at bay. And here's the most important piece of advice I can give anyone with a journal bearing equipped turbo street car. When you get into boost, it doesn't matter if it's 1/4 throttle, part throttle, 3/4 throttle or WOT...... when you are ready to shut it down, never NEVER jump off the gas pedal. Always slowly lift off the gas pedal. I don't care if it's the Chief of Police behind you escorting the Pope, slowly lift off the gas. You see, the turbo is spinning at incredible speeds, typically anywhere from 70k - 140k rpm under WOT, depending on the turbo. The charge air is traveling at mach speeds under WOT, when you quickly slam the throttle shut, the charge air has no where to go but backwards. As our cars do not have a blow off valve from the factory. In a split second, this mach speed airflow reverses itself and slams directly into your compressor wheel. Visualize that for a second.... The shock that the rotating assembly, the bearings, the thrust bearing and the oil rings must endure, when repeatedly subjected to this kind of behavior is horrible. Now you couple this type of extreme condition with oil that doesn't have enough zinc and phosphorus to properly protect the journal bearings, gives the turbo a short life span. This is the true definition of being rode hard and put up wet. This is also the main cause of premature bearing failure in the turbos' CHRA. (Center Housing Rotating Assembly) Some techs call it beating the thrust out of the bearings. When you slowly lift off the gas, the airflow has a chance to slow down and the reverse flow is no where near as severe on the rotating assembly when it does fully reverse flow back through the compressor wheel and MAF pipe. Also, one more thing that this repeated behavior can cause. MAF sensor failure and here's how.
The factory MAF sensor, not the aftermarket ones, but the OEM MAF sensor, has two honey comb / airflow straightening screens that are held in with typically 3 ring clips, 1 on each side of the screen and one to separate the screen. Sometimes 2 between the screens. The more you on and off throttle like a rally racer, the more wear you put on these rings, as they are just held into the MAF housing by tension on the tabs. Plastic on plastic wears out with heat, time and repeated abuse. Eventually, the rings will break or fail and the screen and ring will get sucked into the turbo, resulting in catastrophic turbo failure. The other method that can kill the MAF sensor is this. With repeated punishing decel behavior (jumping off the gas after a WOT blast) the oil seal (some mistakenly call this the turbo seal) gets worn out and starts to let oil leak out. These oil seals are nothing more than miniature piston rings. When the thrust bearing gets taken out from these numerous "events", (excessive side to side motion of the rotating assembly caused by those rapid throttle lifts) the oil seal is the next thing that goes. Now you have oil not only leaking into your intercooler and being blown into your t-body, IAC housing, upper plenum, intake manifold and cylinder heads, but on decel, when the turbo spins backwards and the charge air gets blown out of your air filter, guess what else get's blown out? That's right. That leaking oil from the turbo's oil seal. That oil will coat the inside of the MAF sensor's housing, the heating element wire and circuit board. A bare electric wire that has current running through it and is heated, does not like having motor oil on it. It's only a matter of time before that wire breaks or the circuit board shorts out. Resulting in a dead MAF sensor. This is also a very good way to avert a catastrophic turbo failure. If you ever see oil inside your MAF sensor, the oil seal in the turbo is starting to go out. So check your MAF sensor frequently if you "enjoy" your car's turbo power frequently.
One last bit, what was mentioned earlier about running a blow off valve. Some have had excellent results putting an aftermarket blow off valve onto their setups. Others have had drive ability issues. Most people who run MAF sensors, typically don't run blow off valves. Typically cars with aftermarket Engine Management systems, or Speed Density setups, run blow off valves and have zero issues with drive ability. I personally don't like them on MAF equipped setups and prefer to run a turbo that has a Port Shroud compressor cover. Nor do I like the sound they make. IMO, save the blow off valve for true high hp setups that need them. There are many versions of the ported shroud cover out there, as each turbo company makes their own version for a given turbo. PTE's S ported shroud cover has the bullet hole style, where as their H cover has the slotted style. Both do the same thing and that is to help eliminate part throttle surging. Some people don't want to change their piping and or hoses around to accommodate the larger compressor cover, but rather prefer the TA stock appearing or the E compressor covers. For those guys, I highly recommend a dual ball bearing turbo and an oil filtration kit to give the turbo the longest life span it can get.
Sorry to ramble on and I hope some of this helps.
-Patrick-
The factory MAF sensor, not the aftermarket ones, but the OEM MAF sensor, has two honey comb / airflow straightening screens that are held in with typically 3 ring clips, 1 on each side of the screen and one to separate the screen. Sometimes 2 between the screens. The more you on and off throttle like a rally racer, the more wear you put on these rings, as they are just held into the MAF housing by tension on the tabs. Plastic on plastic wears out with heat, time and repeated abuse. Eventually, the rings will break or fail and the screen and ring will get sucked into the turbo, resulting in catastrophic turbo failure. The other method that can kill the MAF sensor is this. With repeated punishing decel behavior (jumping off the gas after a WOT blast) the oil seal (some mistakenly call this the turbo seal) gets worn out and starts to let oil leak out. These oil seals are nothing more than miniature piston rings. When the thrust bearing gets taken out from these numerous "events", (excessive side to side motion of the rotating assembly caused by those rapid throttle lifts) the oil seal is the next thing that goes. Now you have oil not only leaking into your intercooler and being blown into your t-body, IAC housing, upper plenum, intake manifold and cylinder heads, but on decel, when the turbo spins backwards and the charge air gets blown out of your air filter, guess what else get's blown out? That's right. That leaking oil from the turbo's oil seal. That oil will coat the inside of the MAF sensor's housing, the heating element wire and circuit board. A bare electric wire that has current running through it and is heated, does not like having motor oil on it. It's only a matter of time before that wire breaks or the circuit board shorts out. Resulting in a dead MAF sensor. This is also a very good way to avert a catastrophic turbo failure. If you ever see oil inside your MAF sensor, the oil seal in the turbo is starting to go out. So check your MAF sensor frequently if you "enjoy" your car's turbo power frequently.
One last bit, what was mentioned earlier about running a blow off valve. Some have had excellent results putting an aftermarket blow off valve onto their setups. Others have had drive ability issues. Most people who run MAF sensors, typically don't run blow off valves. Typically cars with aftermarket Engine Management systems, or Speed Density setups, run blow off valves and have zero issues with drive ability. I personally don't like them on MAF equipped setups and prefer to run a turbo that has a Port Shroud compressor cover. Nor do I like the sound they make. IMO, save the blow off valve for true high hp setups that need them. There are many versions of the ported shroud cover out there, as each turbo company makes their own version for a given turbo. PTE's S ported shroud cover has the bullet hole style, where as their H cover has the slotted style. Both do the same thing and that is to help eliminate part throttle surging. Some people don't want to change their piping and or hoses around to accommodate the larger compressor cover, but rather prefer the TA stock appearing or the E compressor covers. For those guys, I highly recommend a dual ball bearing turbo and an oil filtration kit to give the turbo the longest life span it can get.
Sorry to ramble on and I hope some of this helps.
-Patrick-
