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John Slade

Turbo toast.

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I have been reading on turboes extensively and the most common problem is lack of coolant flow. Did you run the engine with the oil feed line detached and verify the quantity for a minuit? I have a book at the office that tells the amount needed for proper cooling.

 

Is the oil return above the level of oil, if it is not then you have two choices, pump up from turbo or move the return line.

 

enjoy the fiddling

 

dust


maker wood dust and shavings - foam and fiberglass dust and one day a cozy will pop out, enjoying the build

 

i can be reached at

 

http://www.canardcommunity.com/

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After reading your experience a couple of questions came to mind.

 

First, how good is the stock Mazda turbo? Would some of the high priced turbos from somebody like Turbonetics be worth the extra money if they were more reliable? I'm not an expert, but is seems to me that a turbine that spins at 100,000 RPM is the last thing you would want welded, but maybe all turbos are made this way.

 

Second, would it make sense to separate the turbo oil and coolant supplies from the critical engine systems. Similar to how some people are thinking of separating the cabin heat water/oil circuits? While an hour should be plenty of time to find an airport there may be circumstances where a failure will cause a larger leak giving you much less time.


Rui Lopes

Cozy MkIV S/N: 1121

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Good points, Rui.

I'm told that the stock '91 Mazda turbo is very durable. There's a Swiss company ( Myriad or something) using it on their firewall forward package.

 

I think the compressor wheels are welded to the shaft by some special electronic process on all turbos. I looked at a turbonetics unit on the web today - $2300 +. Rebuild cost on my unit is about $600, so I think I'll either get a replacement stock unit or have mine rebuilt.

 

Seperating the oil & coolant supplies would make sense if this were a common problem, which I'm hoping it's not.


I can be reached on the "other" forum http://canardaviationforum.dmt.net

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This is from your notes on the turbo plumbing in Chapter 23

"Anyway, back to the turbo. I was working my way around the housing with the blasting gun when something occurred to me. The housing looks totally symetrical, except for the outlet. Sure enough, the bolts just clamp the housing in place, so you can orient it anywhichway you like. I reinstalled it with the outlet pointing down instead of up. This solves the cowl interference problem while also shortening and simplifying the run from the turbo to the intercooler. "

 

Sounds like you clocked the turbo (changed the orientation of intake side and exhaust side) for a better fit. Whats the orientation of the oil inlet and outlet? I think they are designed to be flow through top-bottom. Are you sure you didn't switch the oil inlet for the outlet by mistake? They are usually marked.

 

Are you using the stock oil and water connection points for the turbo to the block?

 

Do you have any good pics showing the turbo and it's plumbing? Is the center section (especially the lines going into it) shielded from the exhaust?

 

Be sure the lines for oil and water have no restrictions on them, it looks like theres an ugly weld or crimp on the water line in this pic.

post-300-141090152425_thumb.jpg

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thanks to a book i think aaron suggested

 

Edit - Sorry but i looked it up and it was Richard Schubert who suggested the book, when i think turbo, i think aaron

 

"turbochargers" by Hugh MacInnes

 

3" turbo needs at least 1/2 gallon per minuite 1/4 OD for feed 5/16 OD for return

 

 

3.5 or 4 inch requires 1 gallon per minuite same tubing for these as long as oil preasure is at least 30 psi with hot oil (not 0 degree (c or f) full boost for you in southern florida)

 

because the oil on the return to the sump is foamy it must run DOWN hill all the way and must enter engine above the level of oil with NO restrictions or kinks

 

enjoy the fiddling

 

dust


maker wood dust and shavings - foam and fiberglass dust and one day a cozy will pop out, enjoying the build

 

i can be reached at

 

http://www.canardcommunity.com/

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John

Was your turbo oil system and position stock? If not then how did your turbo drain back to your system? Not only is proper flow important but the oil exit needs to be very open and flowing. Oil out of a turbo can be very "frothy" and needs a place to flow free to and settle before being pumped out, or a very high volume dry sump used to get all the froth out of the way for the incoming froth. If it backs up your turbo is toast.

 

But the number one thing that raises flags for me is that the turbo wiggled before you used it. I have rebuilt a few turbos and they should never be "loose". They need to be able to spinn free but not wiggle about the axis.

 

I would bet, not a lot of money, that the bearing was a little worn before you began, leading to the free play. The end snapping off would be typical of this event as thats the point where it gets cocked.

 

I would take the turbo to a performance turbo shop and get a post mortem. I think it is very important you figgure out what happened before you replace it.

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Just a thought. After being in the repair busness for over 30 years. The standing joke was to send a kickback to the guy who invented sand blasting. It brought a lot of work to us for bearing replacement. Also Arc welding on any object with bearings in them. I seems no matter how carful you are with the ground placement. The path of least restance seems to be through the bearings.

This is just trying to help prevent it from happening on turbo #2. Jon: After looking at the picture on your web page. I felt I had to write this. I have seen this before.


If the phone don't ring. It's me

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Speaking of turbo oil returns. A while ago I owned a turbo Chrysler LeBaron that had a leak from the oil return gasket. I tried fixing this a couple of times, but both failed, I just let it leak. Anyway, the return was a good 3/8-1/2. The feed, as I remember was much smaller, maybe 1/4.... So the above advice makes sense.

 

btw, that Chrysler was the reason I swore to never buy another North American car again. I've been very happy with my Honda in the 7 years I've owned since trading in that piece of junk Chrysler... The turbo however, seemed to be really good quality. I think it was a Garrett.


Rui Lopes

Cozy MkIV S/N: 1121

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when i think turbo, i think aaron

 

:yikes:

I get that alot. I spin 'round way too fast and blow lots of hot air.

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