Turbo "tight tolerance" coating for increased performance?

[forcefed86]

So I’ve read about a few companies using a special coating on the inside of a comp housing to help lower the clearance between the blades and housing. A tighter turbo will have greater efficiency. Anyone know what these coatings are comprised of? I know they are typically sprayed on and as the blades turn they etch a very tight seal into this “coating”. I had an old junk 60mm garret turbo I tried spraying some high build sandable primer into the back of the cover last weekend. I was able to put 2 light coats and a good 7 heavy coats on the inside of the major compressor before the blades contacted the primer. I never got the minor blades to hit. It’s hard to get in there and get even coats…then I ran out of primer.

Now before anyone starts flaming, I’m not suggesting anyone do this with primer. I was just curious how many coats it would take before the blades came into contact. There is quite a bit of clearance there. I think this would be especially useful on housings that have had a very slight amount of blade contact.

 

[silvreclips]

This sounds like a great idea, if that gap could be made smaller the efficiency would deffinately increase. I think the biggest problem is going to be finding something that will stand up to the extreme heat that the turbine housing sees and is also soft enough not to damage the turbine blades if they do come in contact with it. Deffinately an interesting topic

 

[pj91gsx]

There is only ~.040"(inch) clearence between the compressor wheel and housing for turbos from the factory. the smaller the turbos are the smaller the clearence seems to be. The closer the clearance the less air can escape= increased spool, lb per flow min, and overall efficiency of the turbo.

 

[polarmoment]

I think the biggest problem is going to be finding something that will stand up to the extreme heat that the turbine housing sees and is also soft enough not to damage the turbine blades if they do come in contact with it. Deffinately an interesting topic

As well as finding something that won't damage the engine that has to ingest it while the compressor wheel etches it away.

I remember reading about this from a guy that dealt primarily with KKK turbos on porsches and audis, and him saying it was the bee's knees, then nothing really coming of it. He was claiming orders of magnitude increase in efficiency, but I'm not sure he ever provided data to back up those claims.

 

[silvreclips]

I dont know if I would try this on the compressor side, I was thinking he was talking about the turbine side. I guess it would be easier to do this on the compressor side as less heat is involved. Your primer might even be able to hold up to the challenge. Small bits of primer should no hurt the motor.

 

[silicosys4]

Your primer might even be able to hold up to the challenge. Small bits of primer should no hurt the motor.

Only on a dsm forum.

 

[forcefed86]

Haha! Gotta love it. Some high temp caliper or engine enamel would be more than enough to hold up to the heat. Although it may not like contact with oil. And performance gains would be very minimal on small turbos. Figure a 1% increase in efficiency on a 70-80lb a min turbo may be worth it. (not saying it would even be worth that much)

On a side note assuming you used some sort of dark color on the final coat and a lighter color on the bottom coats. You would be able to see if the blades were starting to touch the housing very easily. Maybe even in time to salvage the housing and compressor blades before damage occurred.

 

[JusMX141]

To me it just means less wear margin for your journal bearings before the wheel rubs the housing, ruining both the wheel and the housing. Not really a marvelous idea.

 

[97gst_spyder]

What about for a bb turbo? Would the gains be noticeable?

 

[silicosys4]

1. Sounds like a bandaid for buying a crappy turbo.
2. 1% efficiency gains for a near guarantee that you'll be sending a constant stream of material, both the coating and your blades, into your engine, as the turbo wears and develops just a teensy bit of side to side shaft play? No thanks. That clearance gap is best fixed during the manufacture of the turbo, IMO.

 

[JusMX141]

I agree, too much work to gain 1/10th of a HP and cause possible turbo damage.

What most people don't realize is the shaft of the turbo moves quite a bit under load....the compressor wheel lifts slightly under full boost then returns to center after letting off, so you never know exactly how close it is to the cover.

Obviously the company building the turbo will take all of this into consideration prior to shipping it.

 

[forcefed86]

If your in the performance/racing world and had a product that made you 1% faster than the next guy you would want it... That being said the 1 percent gain is something I totally made up. I have no idea what type of gains could be seen with this.

Not like I pulled this out of my bum. It's been used for a very long time on aircraft turbine engines, superchargers and turbochargers. Also read an article BorgWarner has been recently testing with it. If the benefits weren't worth the investment why would almost all new aircraft be running these types of coatings?

The yield strength of "coating" V.S. the aluminum housing and how much damage each would do has to be taken into affect. The coating is soft made to wear. Technically the shaft should be riding on an oil film and the bearing tolerances shouldn't change. If bearings are wearing it is time for a rebuild as it will only get worse.



I just thought it was interesting and wondered if anyone had read something I had not.



Heres a descriptive site.

http://www.welding-advisers.com/Abradable-coatings.htm

For best engine efficiency the clearance between the rotating and the static parts should be kept to a minimum because the fluid passing through that space is wasted, as it does not perform any useful work.
Thermal spray Abradable-coatings are designed to have low structural integrity so that they are readily abraded when they come into contact with a high speed moving surface made of stronger materials. The coatings should not to damage the mating surface.
The debris must be tiny and soft, should find their way out of the engine with the air and gas flow, without eroding other parts of the engine. It is therefore not a simple task that of developing suitable Abradable-coatings materials and finding proper processes for their application in reliable and proven ways.
The goal of developing suitable materials and application techniques is to produce seals that do not cause blade wear, that maintain as smooth as possible shroud surfaces and that remain serviceable for thousands of operating hours.

 

[silicosys4]

That looks plausible, now that you have given us some background info and a link. However, the average dsm'r is a far cry from an aeronautical manufacturer, and "spraying primer" into your turbo is about what I'd expect the average dsm'r to be able to do with the info. Just PM'd FP and asked them what they think, and if they would consider offering a coating as an option.

 

[JusMX141]

If the benefits weren't worth the investment why would almost all new aircraft be running these types of coatings?

Average aircraft budget = $100,000,000

Average DSMer budget =

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While this may be worth a try on a shop car, I don't see it making a noticeable difference on a street car. A more efficient intercooler or one less boost leak will definitely translate into more power being made.

 

[forcefed86]

I totally agree... I just thought it was interesting.

FWIW pre-compressor water injection has a similar affect with more benfits IMO. Thats a different topic though.

 

[greengoblin]

sound like you guys are talking about stuff like NIC's turbine coating. It's pretty neat stuff that i'm going to play with once I get to this area of my build.

NIC Industries - Turbine Coat

 

[pj91gsx]

I agree, too much work to gain 1/10th of a HP and cause possible turbo damage.

What most people don't realize is the shaft of the turbo moves quite a bit under load....the compressor wheel lifts slightly under full boost then returns to center after letting off, so you never know exactly how close it is to the cover.

Obviously the company building the turbo will take all of this into consideration prior to shipping it.

That make sense why turbos with a little bit of thrust bearing failure will rub on the top inside of the housing 1st! (can only be seen with the compressor housing off.)

 

[silicosys4]

Here's what I emailed to Fp and here is their response

Hi, I have been reading online about an "abradable coating" that is applied to the housing of a turbocharger in order to reduce the tolerances between the housing and the compressor wheel, so as to increase the efficiency of the turbo. Has anyone there at FP heard of such a product, and would FP recommend such a product, either to be applied by FP themselves, or by the customer themselves after recieving the turbo from FP? Here is a quote regarding the coating, which apparently has been in use by aeronautical turbo and supercharger manufacturers already.

"For best engine efficiency the clearance between the rotating and the static parts should be kept to a minimum because the fluid passing through that space is wasted, as it does not perform any useful work.
Thermal spray Abradable-coatings are designed to have low structural integrity so that they are readily abraded when they come into contact with a high speed moving surface made of stronger materials. The coatings should not to damage the mating surface.
The debris must be tiny and soft, should find their way out of the engine with the air and gas flow, without eroding other parts of the engine. It is therefore not a simple task that of developing suitable Abradable-coatings materials and finding proper processes for their application in reliable and proven ways.
The goal of developing suitable materials and application techniques is to produce seals that do not cause blade wear, that maintain as smooth as possible shroud surfaces and that remain serviceable for thousands of operating hours."

Here is a link, describing some applications

Thermal Spray Abradable Coatings

Is there a possibility that FP could offer this as an option when purchasing an FP turbocharger?


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[polarmoment]

Honestly, I'd be most worried about it building up in the intercooler on the fins and big chunks of it breaking loose at a time, or making a nice fine powdercoat on the IC's interior surface and hurting heat transfer.

This is one of those things where I'm more than happy to let someone else prove that it's worth it and not be the guinea pig.

 

[PieEyedPiper]

OT, I'm amazed FP is so actively "prosecuting" Mobil 1.

Neat.