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White carbon deposit?

Old Jul 4, 2020 | 04:11 PM
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White carbon deposit?

Took out the twins checking for a coolant leak and
due to the history of this car being(parked for almost 10 yrs and driven 2) not a pretty sight and boy was it difficult.
I came across this. Normally carbon is black but this is more white/tan like coal ashes.

I only found one post with similar description about running lean. In my case, might be due to having extra air when i was fixing idle problem.

This is just my thought. Anyone else know or seen this.
scale 1-10. How serious is this? Will it go away? Break cleaner the heck out of it?






(Im not too worried as when the engine goes and car gets overhauled ill probably go single turbo)
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Old Jul 6, 2020 | 09:37 AM
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Typically that's from running lean or running funky race gas. I've seen guys running leaded race gas and the inside of the exhaust tip was bright white.

Regardless it's cosmetic as far as the turbos go, no need to try and clean it or anything.

You may need to figure out for sure if the engine is running lean or something, though.

Dale
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Old Jul 6, 2020 | 10:12 AM
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Weirdly enough it kinda just stops at the turbine housing for the twins, my downpipe looks pretty much like how youd expect.
while they were out i thought id "refresh" them visually at least.

Might last a while or itll flake off


How would i check of its leaning out with stock ecu?
I can only think of one way and thats AFR gauge

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Old Jul 6, 2020 | 11:21 AM
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They sure cleaned up! If you use paint on the turbine housings, that will burn off in 10 minutes or so. It will smoke and stink big time. Once it's burnt off, it's burnt off though.

Hard to say on the running lean. Does the car generally run well? Do you know how much boost you are running?

Dale
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Old Jul 6, 2020 | 12:14 PM
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Its a shame they wont be seen.
I used vht so ill either be one of those success stories
or say it doesnt work. Ill follow their curing instructions
but if it doesnt work at least no one can see haha

Yes car runs well, after fixing tps issue
last time i drove it under boost it did do the 10-8-10
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Old Jul 6, 2020 | 12:58 PM
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From: https://www2.mazda.com/en/100th/
Originally Posted by rattlehead
How would i check of its leaning out with stock ecu?
I can only think of one way and thats AFR gauge
the stock ecu will run lean at low throttle openings and rpm for better mileage and lower emissions, for power it runs stupidly rich.

the point being that if you looked in there after a long highway cruise, it will be just off white. if you look in there after idling for a long time, or after lots of full throttle, it'll be dark.

so its meaningless, except that both rotors exhaust ports should be the same color
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Old Jul 6, 2020 | 01:31 PM
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j9- well it had only seen idle recently due to fixing the tps
but it seems like not really much to do about it. I guess im just glad this doesnt mean its the end
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Old Aug 12, 2020 | 09:37 AM
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Instead of starting new thread simce its related ill bring this one back
Could/should i use a dremel to smooth up all around(without going past gasket)white box. Any benefit besides looking cleaner?
any issues if i were to remove the red, i just wouldnt want it snapping off and ruining things on its way out. Perhaps get it welded?
Im still keepin an ey out for some twins near me, but while i have them out could do this.
thanks



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Old Aug 12, 2020 | 09:45 AM
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Frankly I'd leave it be. Those cracks will spread long term no matter what you do, all the N3A1 turbos are like that.

Grinding anything out may just accelerate things.

Dale
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Old Aug 12, 2020 | 10:07 AM
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Alright thanks!
i'll just throw them back on as i look for another set.
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