| Im having problems with my Z smoking and it has rebuilt T28 turbos with new center assembly and seals, and the whole PCV system is new. So i ran across this on aus300zx.com. Is this guy correct with his theory? ____________________________________________________________ OK so here it goes
Please don't doubt this theory in public as unless you have seen it work you may be costing members thousands by sending them off changing seals and turbos etc when there may be no real need. I purchased a TT Z32 over six years ago, the engine and turbos were very tired and smoked a little - not a lot a little.
The exh was screwed and falling apart so I replaced it, 2.5 inch the whole way through with two resonators and stainless mufflers (one of each per bank). Now I had a serious smoke issue - exactly the same symptoms as above posts. I replaced the engine with a know good engine and had the turbos overhauled so the entire eng system was replaced/repaired. IT STILL SMOKED! At this point I doubted the turbos had been done correctly as this is typical worn turbo smoke signals, I approached the turbo shop and they did some research as did I.
When we got in contact with each other again we found we had both got the same advice from several other people - BALANCE PIPE ON THE EXH?
We had a think and decided to try it as it is cheap and the previous system had one and it smoked heaps less (remember I changed the engine & OHd the turbos after then). I took the car to a local Pitstop who laughed at me and said it will never work.
The guys were so convinced I was wrong they made me point out the exact place to put the pipe and show how long it had to be and what diameter (they really were having a go at me). Well I had the last laugh we started the car after the pipe had been fitted and left the car sitting for a good 15mins with no smoke at all.
Straight off the bat the problem was sorted Pitstop ended up only charging half the price they were so embarrassed. This fix worked for over two years until ultimately the turbos wore from abuse and began smoking again - they have now been replaced with BB type........
THE THEORY:
OK so we have a V6 firing order 123456 so we have a pulse of exh on one side then a gap then another then a gap etc etc etc while the other side does the same in the gaps from the first side.
Engine idling at around 700RPM being a four stroke thats 350 exh beats per minute per cylinder, six cylinders thats 2100 per minute, half each side so around a thousand exh pulses per minute past/through the turbo (17Hz) Imagine you have a crapy little partly worn turbo seal being bounced backwards and forwards on its shaft at 17Hz with relatively high oil pressure on one side and low exh pressure on the other - isn't there just the slightest chance this could create a pumping situation where even the smallest amount of oil could be drawn through into the exh? We are talking around two or three drops of oil a minute here not liters of the stuff.
Go and change all the valve guide seals if you want and the piston rings and overhaul the turbos etc etc etc or if you like put the balance pipe back in as per the original design (the resonators at the back are joined) and hope that ya haven't already done to much damage.
We have had the turbo Zeds over here in NZ for at least ten years in large numbers and many many people have been caught out by this same mistake. Some of the cars above may have worn turbos etc and may smoke even with the pipe fitted but I betting there will be others this will fix. Oh and by the way I'm an ex aircraft engineer who has now gone to the automotive industry so there are a few brain cells behind the posts. Happy arguing for those that doubt and best of luck to the smart ones who will try it.
MungyZ of NZ
Josh E. |
