Kool-Aid

 

Thanks, good info. Makes enough sense to me!

 

For those of you running the turbo blankets, have you noticed a decreased lifespan on your turbos? Trapping the heat inside the blanket may be good for everything else in the engine bay, but I think that would cook your turbo pretty quick. I wish I had my textbooks here at home so I could put some numbers to it, but I know oil breaks down at high temperatures. I am not sure what sort of temperatures the turbo reaches with/without a turbo blanket, but it would be interesting to look into.

Has anyone tried taking cool air from the front of the car, running it over the turbos, and out the side vent of the car? This coupled with a heat shield between the LIM and turbos would keep heat away from the engine and provide the additional benefit of getting heat out of the engine bay rather than trapping it inside a blanket.

 

I've been running the same blanket going on 3.5 years now with zero turbo problems. Haven't removed it very often either, zero oil leaks.

The studs belong to the LIM that the blanket is wrapped around

I have the prototype LIM blanket on my GZ piece, and it's silver as seen in the picture I previously posted.

 

running cool air over the turbos would detract from their ability to make power.

Horrible idea (no offence)

80% of a turbo's power is from heat isolated in the hotside housing not from actual compression from the impellers

TURBOS ARE A WEARABLE ITEM

There are 2 main issues that people need to understand about turbos, to understand their wearable nature.

Bearing failure

Impeller Erosion

Both of which are possibly increased with higher boost & when increased heat isolating barriers are put into play.

 

Just like your apex seals and rotor housings, brake pads and rotors, tires and fuel filters...... Did somebody state that turbos last forever

 

No offense taken, just throwing ideas out there. Prometheus, would you mind shooting me a PM explaining how turbos get their power from heat isolation in the hotside housing? This is something I hadn't heard of and definitely want to learn about.

 

"thermal conductivity, k, is the property of a material that indicates its ability to conduct heat."

you'll note MICA doesn't have mucho K...

the bigger the number the more heat is transferred:

Aluminum alloy 180-120

Steel carbon 43

Stainless steel 12-45

Mica .71

Fiberglass .04 (but resin melts approx 1000F)



my 1700-1900 degree propane/air flame only heated the opposite side of the MICA to 320 F. in addition, the panel was ambient (66 degrees) less than 2 inches from the flamepoint on the reverse side.
mica melts at approx 6000 F.

 

^ oooh, blow torch resistant.

Oh ok, thanks. hey wait, wasn't that your engine in the pic? I can tell cause of the huge DP. That is the black colored blanket?

 

Hahaha no way...just read the 2 pages and this has been my theory since day one. makes no sence to put a hot hunk of iron next to a hunk of aluminum that needs to be cool. Now i will post what i use. its lagit poo
https://www.rx7club.com/showthread.php?t=906307...just a recent thread i started....and this idea howard has here has been applied

 

There are three different blankies in question here......

black=turbine
silver=LIM
light blue=Linus

 

Nobody said they last forever, but people tend to think they last much longer than they actually do.

I just put that in caps to emphasize the idea of having to replace/ rebuild the turbo/ turbos, before they get fragged from introduction of foreign media.

 

Thermal conductivity of some ceramics get very close to that number (W/mK)
http://www.matsceng.ohio-state.edu/f...eThCondJMR.pdf
http://www.accuratus.com/zirconia/zro2_thermal.html
As far as the advantage of mica over ceramics, I don't think there's much in it. How does the durability of mica stack up to ceramic and how easy is it to apply? There are countless vendors who do ceramic coating at relatively low cost, who the heck does mica coating of exhaust components?

 

This is one of the things my welder and I considered when it came time to make the manifold for the Holset H1C swap. Also we made a heat shield out of inconel that was attached to the front of the block off plate on the LIM. Howard, what is your opinion on the position and type of block off used to combat this heat? I plan on putting a stainless steel shield around the turbine as well here in a few days.

 

^ Looks professional, I'm diggin it....never cared for the blankets, they don't wear very well, and, as others have said, if they get oil soaked they're a fire hazard

 

excellent write up as always howard. i'm interested to see where we go with this thread. subscribing.

 

A few more relevant figures for your list:

Air .024 (illustrating the importance of heat shields & air gaps)

Cast Iron 55 (or less, composition dependent)

refractory mineral fibers .04 (aka rock wool)

high performance refractory ceramic fiber--typically <<1.0


A couple of notes:

Adding a blanket will not necessarily make a component run substantially hotter; what it will do is dramatically reduce the egress of heat as transfer slows down dramatically as the temperatures approach equilibrium. It tends to promote uniform temps throughout the casting and slows the rate of cooling which are good for the stability and life of a casting. If you can keep the oil & bearings cool enough, then there is no drawback to insulating the hotside.


For good thermal control in a managable pakage, I agree with the approach you've outlined. A hotside blanket and an external heatshield; I would suggest lining the heatshield with a thin (1/16") refractory ceramic cloth facing the hotside.

 

Where'd you get a piece of mica that big?

 

A proper turbine blanket works extremely well, and the benefits far outweigh any supposed 'risks' in my opinion.

They last for many years and, and anyone that worried about a fire hazard probably owns the wrong car.

We install/recommend them on every single turbo car that comes out of our shop if that tells you anything

 

i like it

 

if anybody cares and i can't see why they would but just to give a sense of my drift... i think a well designed turbine housing cover (blanket sounds too bedroom, we are talking engine compartment w gonzo hp) featuring some air gap is an essential part of the setup. i like barrier panels too. i plan to incorporate a panel that shields the primary runners on my CPR turbo manifold as well as the turbine housing.

i have an upcoming 4 turbo multi day dyno program (https://www.rx7club.com/single-turbo-rx-7s-23/separating-fiction-reality-couple-days-dyno-903611/) and will be doing a bit of heat r&d during the tests.

i suspect a lot may come from this thread as far as heat management. there certainly are lots of members that have come up w their own ideas. i hope to see some.

the mica was donated to the cause from a friend but McMaster Carr sells a good sized 1/8th plate of MICA for $61. cheaper than a blown motor. BTW, MICA may or may not be the answer... i am just peddling along here in hopes of learning a few things.

the thing that most impressed me about the MICA sheet was that it was totally ambient (66 F) less than 2 inches from where i had the 1700+ flame on the backside!

that tells me it just doesn't transfer heat. transferring heat away from the heat point should be no different than transferring heat thru the material to the other side which is our consideration.

i haven't (yet) put a saw to it but it appears to be workable.

hc

 

So on the turbo blanket, you want it to be loose fittiNg with an air barrier between?

 

glad i found this thread! i want to do some heatshielding soon... ^^ like what he said above, to properly heat shield there has to be a gap of air between the layers?

how easy is it to flex the MICA?

 

and some more good info in a howard thread.
I need to go play in the garage this weekend

 

Real thin sheets of mica can be cut with regular scissors. Thicker piece can be sawed - maybe snipped. They also make lampshades and stuff outta mica sheets. It's pretty workable.


Thanks for the info on where you sourced it at. All the sheets I found were very small and very thin (which would mean layering - and then you get into a "what type of adhesive" discussion). Thanks, HC!