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Rob Spiegel
User Rank
Blogger
Re: Something wrong with turbo
Rob Spiegel   12/23/2011 2:49:08 PM
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Hey Keldawwg, that's the kind of detailed comment that realkly raises the bar on comments. Thanks for all the detail.

shjacks45
User Rank
Bronze
Thanks for confirming my comments
shjacks45   11/21/2011 8:43:40 PM
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@Keldawwg:

 Thanks for verifying my comments (& @wade's).

Keldawwg
User Rank
Gold
Re: Something wrong with turbo
Keldawwg   11/21/2011 2:18:40 PM
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A couple things...

It was not an aircraft turbocharger, it was simply an aftermarket turbocharger that was fitted to a car that did not originally have a turbocharger.  It was added to the car to increase the performance of the engine...

Exhaust turbo engages at low engine rpm? I don't know what you are asking with this question... The car had a small amount of turbo lag where the engine responded more slowly than a non-turbocharged engine until the exhaust flow was sufficient to spin up the turbocharger and start providing boost pressure. So from 600 RPM (Idle) to about 1500 RPM the engine did not have any increased power, in fact it had less power than a stock 280ZX. From 1500 RPM on, the engine produced a great deal more power than a stock normally aspirated engine. The time elapsed from 1500 rpm (Starts to develop boost) to 3500 rpm (approximately when the engine blew up) was perhaps 2 seconds...

The waste gate is a device that opens to vent any additional pressure beyond what it is set at. At 9 pounds of boost, the car performed great and did not require any additional hardware to keep detonation from happening. The engine did not knock from preignition at that boost level. The straight six in the Z cars was developed from a design originally licensed from Mercedes-Benz, 7 main bearings, 8.3:1 compression ratio and one of the most durable engines ever produced by anyone...

PCV valves were added to cars when they could no longer just vent the crankcase. (This is what they had on cars manufactured before the late 60's... Just simply a vent...) They wanted to pull the blowby gases from the crankcase. Without a PCV valve, if there was a backfire in the intake manifold, it would have a direct path into the crankcase, which would likely ignite the air-fuel mixture which is present in all internal combustion engines. I think you can imagine why this would be a bad thing. At the very least, the engine would probably blow a few seals from the internal pressure...

PCV valves need to be replaced regularly for two reasons. If it is clogged, and no air is being drawn from the crankcase, the resulting pressure from the blowby gases could blow your seals on the engine because the engine is now a sealed unit... If it is stuck open, the backfire-blown engine scenario could happen just like when they didn't have the PCV valve in place... A PCV valve is simply a calibrated air leak from the crankcase to the intake manifold... But probably it's most important function is that it is a one-way valve. Air is supposed to flow only one direction. From the crankcase to the intake. This is why I stated that the PCV valve was defective... If it was installed in a non turbo charged car, the result could have been blown engine seals; in a turbocharged car the problem was a bit more dramatic...

Question 6... Is there a question there? I didn't under rate my turbo, I just simply adjusted the waste gate so that it would open at 9 pounds of boost. This means that the turbocharger would never pressurize the intake system with more than 9 pounds of pressure.

Question 7... Ummm, in the 2 seconds going from 1500RPM to 3500RPM, I was driving my car... Specifically, I was in second gear accelerating to approximately 45 miles per hour. I didn't see the oil jetting into my turbo, I saw all this evidence as I was taking the car apart to replace the engine. I had no advance warning; one second the car was running perfectly (with 260,000 miles on the clock) and the next it was dead.

A 1979 280ZX did not have carburetors... 1974 260Z was the last year the Z cars had carburetors in the US... I believe that some Fairlady right hand drive cars produced for the Asian markets might have had carburetors as late as 1975, but by 1976 world wide they all had common rail fuel injection...

I did not try to get Fram to pay for my engine... I just chalked it up to a learning experience; never buy ANY Fram products. Fram oil filters are the absolute worst you can buy, I have seen several cars destroyed by them, and a couple motorcycles as well. I worked as a mechanic all the way through school becoming a mechanical engineer; I have seen a lot of shoddy products produced by companies that used to make good stuff. Fram tops the list easily. I once replaced an engine for free for a single Mom with three kids whose engine was destroyed when her Fram oil filter split wide open on the freeway and her engine seized. She had no warning either; one second she was driving to work, the next her engine was locked up so hard she spun out of control on the freeway... I took pictures of the oil filter, and Fram graciously offered to refund her the purchase price of the filter... It was all she could do to pay for a used Japanese engine, which back then was around $350...

shjacks45
User Rank
Bronze
Something wrong with turbo
shjacks45   11/21/2011 4:02:17 AM
NO RATINGS
1. Aircraft turbocharger for 280 HP aircraft engines placed on a 140 HP auto engine? This series of parts could be turbo-normalizers, which upgraded 18,000 ft altitude air (3psi, -20 degrees) to sea level air pressure. As a turbocharger, several engine changes such as lowering compression ratio is required (late 70's 280Z had 10:1 compression ration; the aircraft engines were 8.5:1 needed lowering to 7.5:1). On the aircraft engines the turbos were originally used on, 70F air was compressed to 198F (results in power loss when used without intercooler) .

2. Exhaust turbo engages at low engine RPM?

3. Stock 1979 Nissan 280ZX has a carbuerated engine. Carburator are designed for a manifold vacuum. Positive Crankcase Venilation valve is designed to take oil fumes (gas, etc.) from the crankcase headspace and using the Manifold vacuum to pull them into the engine and burn them.

4. PVC valves were added to reduce air pollution. Older cars did not have them and newer vehicles operate satifactorily when they are clogged.  The question implied is why did you feel that you needed to change the PCV valve, presumably there were engine problems such as excessive oil usage?

5. FRAM would not be liable for any damage caused by using its replacement parts outside the parameters that the original part was designed for q.v. engine with non-Nissan turbocharger.

6. You say you under rated your 14 psi turbo to 9 psi. Measured or settings for the original spec 280 HP aircraft engines (which take in twice as much air as the 280Z)?

7. Gee, if I saw oil "jetting" into my turbo I do not think I'd continue running the engine. Your dialog seems to indicate you revved the engine until it blew. Manifold detonation would be a likely cause of your engine damage. Engine oil ignites at a much lower temperature than gasoline, the extra 200+ degrees from compression, high compression engine, boom.

 

 

 

wade
User Rank
Bronze
turbo pcv setup
wade   11/17/2011 10:16:16 AM
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william has it correct.  pcv should connect ahead of turbo.  also, broken pistons from hydraulic lock or combustion pressure?  turbo would never drain into the intake manifold.  blow the turbo oil seals and you will get smoke but will get oil to the cylinders if you are cranking without the engine firing.

Charles Murray
User Rank
Blogger
Website
Charles Murray   11/15/2011 4:07:38 PM
NO RATINGS
What a great website link. Simple products -- such as PCV valves, oil filters, and fuel pumps -- have the potential to turn small problems into a fatal ones, as was almost the case for this writer. Thanks for the website link. We should all take a hard look at it, especially those of us who are do-it-yourselfers.

Lauren Muskett
User Rank
Platinum
Re: Oil Filters
Lauren Muskett   11/15/2011 2:20:01 PM
NO RATINGS
Asking for your used oil filter is a great tip, especially at the quickie oil change places. I am always concerned with what goes on with my car when I bring them to those places. You definitely get better quality oil/filter when you do it yourself, but soemtimes it just doesn't happen that way!

jmiller
User Rank
Platinum
Re: pcv valve rattle?
jmiller   11/14/2011 10:44:13 PM
NO RATINGS
I'd laugh, except I've done the same thing.  Wiring them darn trailers isn't easy.  Even though I'm an ME I sure thought I could follow a simple schematic and put everything together in the right way.  Little did I know.

Critic
User Rank
Platinum
PCV Misunderstandings
Critic   11/14/2011 4:12:04 PM
NO RATINGS
A PCV valve should not be relied upon to prevent boost pressure from pressurizing the crankcase.  Also, it is important to understand that the crankcase will be pressurized while the engine is boosted, from blow-by.  When a turbocharger or supercharger is added to a car, it is very important to re-engineer the PCV and crankcase venting systems.  I suspect that in this instance, this was not done.

bob from maine
User Rank
Platinum
Oil Filters
bob from maine   11/14/2011 12:58:24 PM
NO RATINGS
Quickie oil change places are notorious for 'double gasketing' and using cheap oil filters. If you have one of these places change your oil, ask for the old filter in a plastic bag; check to make sure the the o-ring gasket is with it, if not, find out why. There is generally a reason why most manufacturers offer different grades of oil filters for different prices, the difference in cost is insignificant over the life of the car, buy the best you can find. Regarding the PCV valve, it is likely the original had come with the turbocharger kit and did nothing but block off the vacuum line, or was deliberately installed backward to prevent damage.

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