I was reading a friend's website and he's put down some good info on turbocharger myths. Much of it has been formatted to his specific car platform, so I have reformatted it again for everyone here.
TURBOCAR MYTHS AND HALF-TRUTHS:
Myth #1 "20 pounds of boost! how often do you change headgaskets?"
Answer- almost never.
leaking or "blown" headgaskets are caused by one of three things.
1) normal wear and tear
2) poor installation
3) overheating/detonation
Myth #2 "turbo engine? they are throwaway motors after 100,000 miles"
Answer- Nonsense.
Almost any motor will last a long time with proper maintenance and handling. It all depends on how it was treated and maintained from day one. Turbocars require a bit more attention to preventative maintenance, especially chainging oils. Otherwise they can be reliable as long as they are not out of tune.
Myth #3 "you need a catalytic converter for backpressure or you will hurt the motor"
Answer- More nonsense.
You need a C.C. on your car because of tailpipe emmissions standards in your area. Otherwise, your engine will suffer no damage because this "backpressure" from the cat-con is no longer present. As a matter of fact the first time you stuff your foot in it and the tires are smoking because your making another 10-30 h.p. you will be wondering why you waited so long!
Myth #4 "headbolts have to be thrown away every time you use them"
Answer- Maybe.
Mopar specifies that headbolts SHOULD be replaced if they have been used twice. A simple way to test headbolts:
First step is to throw out any bolt that looks stretched or has some corrosion on it. Then you install the bolts using the procedure in the factory service manual, then stop before the last step.
The last step is to turn the bolt a 1/4 turn from the last torque reading (65 ft/lbs for an 11mm headbolt) set your torque wrench to 100 ft/lbs and do your 1/4 turn. If the bolt is good you should have no problem getting that reading before you hit the 1/4 mark, if a bolt is bad it won't come up to the 100 ft/lb mark. Just replace that one and continue on to the rest of the bolts.
Myth #5 "if you pull the head off it must be planed"
Answer- Not unless you saw excessive engine temps (water temps) when the engine was running. If you had, then you might have a warped head. Slightly warped heads can be planed. Severely warped heads make good boat anchors but cannot be reused on an engine.
Myth #6 "lean is mean" (to infer your car will go faster being lean)
Answer- Dangerously false.
Only if you wish to smoke a few pistons. You have some leeway of course on each side of the magic number (that value where fuel is mixed correctly) which to play. Cooler (richer) at most you risk losing 10% of your h.p. if your running very rich.
Too far on the other side however and you risk melting a piston. So in this case the only thing "mean" is when your piston melts from being "lean". its a catchy phrase but not true with automobiles.
Myth #7 "you cannot mix synthetic and normal motor oil"
Answer- False!
Hell they are selling blends of the stuff at the stores now.
Myth # 8 "100,000 miles on a turbo means the turbo is fried, regardless of maintenance history."
Answer- Nonsense. See #2.
Myth # 9 "If you run the turbo past it's factory boost setting, it is called overspinning the turbo, and you will destroy the turbo."
Answer- True and False.
It is called overspinning a turbo when your operating a turbo outside it optimum compressor map range, this much is true. But if your turbo has been built correctly and you follow proper maintenance along with common sense (letting the engine cool off before shutting down the car after hammering on it) your turbo will have a long and happy life, even at levels exceeding its optimum map range.
Myth # 10 "Big intercoolers cause lag"
Answer- False!
A bigger intercooler flows more air, thus there is les restriction to the turbo, and hence less resistance to the exhaust on the turbine side of the turbo's shaft. Less resistance, quicker spool.
Myth # 11 "Turbos don't glow. If your turbo glows, you have more problems than you know!"
Answer- True and False.
It's quite normal for your turbocharger to glow after "spirited driving" after all your exhaust flow is as high as 1500 degrees! The more power you make the more your turbo is likely to glow a bit after hammering on the car...
However it is possible that your cam timing or distributor timing is off and that would cause you turbo to glow A LOT! I have seen one car where the cam timing was off far enough where the turbo got so hot that pieces of iron were flaking off the housing! If everything is in order moderate amounts of "glow" is normal....
And remember to let your car "idle down" a few minutes after hard driving, your turbo will live a lot longer.... Or install a turbo timer to do this for you!
_________________
-Jason Arro -- Club-S12 Moderator
'85 Nissan 200SX -- CA20ET
http://www.cardomain.com/id/arro200sx
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Oct 9, 2002, 10:54 am · #1