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Tips on how to fabricate a mica heat shield for the LIM?
After doing lots of reading here, I'm looking to fabricate a heat shield/thermal break for my LIM out of mica. I currently have a PTP "lava" blanket around my turbine housing, and the DP is wrapped with PTP lava wrap, but I'm looking for a bit more thermal insulation to keep the cold side cold and hot stuff hot. Problem is I've never fabricated anything out of mica before, so I'm looking for tips from those who have done something similar. Some specific questions:
1. Perusing the McMaster-Carr online catalog, there are lots of options out there for mica materials, with different characteristics - thermal, machine-ability, etc. What are you all using & why? I'm thinking a rigid mica panel between 1/8"~1/4" thick would work well if positioned with a roughly equal air gap spacing between the LIM and turbine housing.
2. What kind of tooling is needed to cut, shape & drill the mica panels? I'm thinking it might be more similar to a ceramic/masonry material than a metal, so some specialized tooling might be needed?
3. How have you guys mounted your mica insulation? Pictures of finished installs would be awesome. I'm thinking of fabricating a SS or AL bracket bolted to the mica panel that fastens to the LIM somewhere, probably using an existing tapped hole, positioning the mica panel roughly halfway between the LIM and turbine at its closest point as an air gap.
To be more specific, I'm running the 13B-RE Cosmo LIM & UIM with a BW SX300E series turbo. For reference, here's a couple of pictures of my engine bay as it is now. Thanks in advance!
as purchased from McMaster Carr, the sheets of mica are workable as wood. easily drilled or sawed.
^Thanks Howard, that's very helpful. Did you do yours with the 1/4" or 1/8" thick mica? I figure if I can make it fit, the 1/4" would be a more effective heat barrier.
Similar to Howard I have straps at the top. I bent similar metal to create slide into points for the bottom. These are mounted on the top exhaust studs with an extra nut, i.e. the first nuts is normal setup for securing exhaust, then slide strap, then another nut. I also partially cut the mica so I could bend the bottom close to the intake. The top straps are easy to see in first picture while one of the bottom slide in points is somewhat visible. I also cut a piece and attached it at a 45 degree angle on the front as can be seen in second picture. A similar/improved setup to this may be more important for those of you with turbos mounted further forward than Howard's and I.
Tho this will not be superior to mica, it’s easy to form and mold around the lim making it more attractive than a flat board shoved in between them ( sorry Howard). I used this and molded it around the lim. It comes in different lengths and thickness to suit your needs. You can mount it with a spacer right to where the egr mounts using some fender washers where you poke holes thru it. If you have a xcessive type, some simple aluminum brackets will work great. I noticed a difference in my afr after and was able to touch the lim under it where before I could not, unfortunately I did not take any temperature readings prior to installing it. Just a simple and clean solution that I’m very happy with the end result.
gdub29e. i spent some time on the Heatshield Products site and they have a number of good products. i especially like their focus on lava which is similar to mica. i also applaud your recognition of the need for heat shielding the LIM runners. while my "flat board" type of shield might not sound real sexy it does offer the essential air gaps and perfectly covers the rectangular area that needs to be protected.
Howard, I agree they have some decent selections. Mica would be best in function. I’m definitely not knocking your board, for functionality you couldn’t get much better. I actually accidentally stumbled across them because I was looking for something like Mica but had some flexibility to mold around the front lim runner. I remember reading a post of yours some years back about the heat transfer rate of aluminum. It’s actually the reason I had my xcessive lim coated with 2500°. Much later, I wanted to take it a step further and added that stuff to separate the lim from the header / turbo. At the time I didn’t think it would make much of a difference, but I was wrong. I wish I would’ve taken temperature readings, pre-and post install. It did make a change to the original tune. There are a few decent options out there to create a thermal barrier, but even a sheet of aluminum with that gold foil crap stuck to it would be better than nothing. I’m interested to see other peoples ingenuity also.
... even a sheet of aluminum with that gold foil crap stuck to it would be better than nothing.
I have at least 1/2" of air space on the manifold side with this sheild.
I don't feel this is ideal but I definitely couldn't snake a flat piece of mica around the front edge of the manifold. I plan to run this to start and may squeak in a flat piece of mica where space allows. Figure it is worth trying to acquire some temperature readings first. Most important goal IMO is evening out the heat soak, with temperature being a close second.
Wondering if we can sticky this thread. Until recently, I had no idea how much on an impact a shield could make on AFRs. Thinking a sticky thread like this with multiple solutions could help the entire community.
Surprised Sakebomb, IRP, Banzai, etc has yet to create a universal Mica shield with tabs for the community. Significantly less in cost relative to the Inconel shields that are sold.
Alex, yes that’s great compared to nothing. I really like how yours wraps around the front of the lim also. That resembles mine. I just can’t stand that dei gold colored foil personally . Some like it, and there’s no denying it works.
I'm leaning toward the rigid mica panel for its better thermal characteristics, but if you take a close look at my engine bay pictures in post #1, you'll see that because my turbo sits far forward & up high, there's a tight pinch point right at that front LIM runner corner. In fact the PTP turbine lava blanket I have almost touches the LIM there with little air gap. So I think I really need to be able to get whatever shielding I come up with to wrap around that corner of the LIM. I can probably fab up something with the 1/8" mica that could follow that corner in the tight space, or the stuff Gdub29e suggested could work here.
I'm leaning toward the rigid mica panel for its better thermal characteristics, but if you take a close look at my engine bay pictures in post #1, you'll see that because my turbo sits far forward & up high, there's a tight pinch point right at that front LIM runner corner. In fact the PTP turbine lava blanket I have almost touches the LIM there with little air gap. So I think I really need to be able to get whatever shielding I come up with to wrap around that corner of the LIM. I can probably fab up something with the 1/8" mica that could follow that corner in the tight space, or the stuff Gdub29e suggested could work here.
Pete-- Can you use a spaced off of the motor to give you a little more room? Looks like you have more room on the cold side of the turbo toward the inner fender well. Would get the hot side from touching and allow enough space for a Mica shield?
Jp3 stuff is top notch. Downside is you have to buy four exhaust manifold gaskets… Last time I checked, they’re not cheap. Plus any of the other stuff that is affected like downpipe, oil feed line, drain, his new airbox and intercooler piping. It could open up a can of worms.
Pete is pretty handy, I would imagine he could blend both styles together and fabricate something out of mica in the flat area with something flexible on top wrapping around the front of the lim. My turbo set up is an old aspec long tube that places the turbo in a similar position. You kinda have to work with with you got sometimes.
Pete-- Can you use a spaced off of the motor to give you a little more room? Looks like you have more room on the cold side of the turbo toward the inner fender well. Would get the hot side from touching and allow enough space for a Mica shield?
^Those spacers would probably solve the LIM insulation problem, but end up creating a new one. I have my external WG's recirculated into the DP, so the spaced out exhaust mani would likely bugger up the WG dump plumbing alignment & clearances.
Jp3 stuff is top notch. Downside is you have to buy four exhaust manifold gaskets… Last time I checked, they’re not cheap. Plus any of the other stuff that is affected like downpipe, oil feed line, drain, his new airbox and intercooler piping. It could open up a can of worms.
Pete is pretty handy, I would imagine he could blend both styles together and fabricate something out of mica in the flat area with something flexible on top wrapping around the front of the lim. My turbo set up is an old aspec long tube that places the turbo in a similar position. You kinda have to work with with you got sometimes.
~ GW
^Bingo! That's exactly what I was thinking could work - the rigid mica with your flexible stuff attached to the front edge of the mica & bending it around the LIM's tight front corner. Then the mica would just bolt up to the LIM with brackets like Howard's setup, using two of the LIM/UIM studs/nuts. May need to substitute 2 slightly longer M8x1.25 studs to account for the bracket thickness but that's easy.
I wouldn’t be opposed to putting some mica behind mine for added value. I think you’ll find the flexible stuff is not terrible to work with. You can make compound curves and use sharp scissors to cut the aluminum down. Shrink the inside wall leaving the outside and insulation intact. You can roll the edge over at the ends sealing the insulation inside better. Again, it’s not mica but teamed together I would imagine it will cover all the bases for you.
I took Howard's words of advice and fixed mica to the area in discussion. With the Turblown shorty IWG cast manifold, little space remains between the turbine housing and the intake runner. The compressor cover leaves no space for separation, well, maybe 1 mm.
With the PTP lava blanket, it allowed me to rest the mica sheet in place and attach to LIM using 2 locations. It gets me plenty of stability.
Pics for reference, don't mind the corrugated plastic sheathing on the fuel line, it's embarrassing I know
While perusing the McMaster-Carr catalog, I found these flexible mica sheets. They are thin, thickest sheet is a 0.040" thickness, but they come in 23" x 39" sheets, and can be bent around objects like the LIM. They share the same thermal characteristics as the rigid mica panels McMaster-Carr sells. Has anyone used these before on your heat shielding projects? I'm thinking that if I were to stack several of these sheets on top of one another, and getting total stack thickness to about 1/8", it would be a great thermal break/insulator that can be wrapped around the LIM and fit between those pesky tight spaces, such as the turbine and the front LIM runner like I have in my FD. Thoughts?
While perusing the McMaster-Carr catalog, I found these flexible mica sheets. They are thin, thickest sheet is a 0.040" thickness, but they come in 23" x 39" sheets, and can be bent around objects like the LIM. They share the same thermal characteristics as the rigid mica panels McMaster-Carr sells. Has anyone used these before on your heat shielding projects? I'm thinking that if I were to stack several of these sheets on top of one another, and getting total stack thickness to about 1/8", it would be a great thermal break/insulator that can be wrapped around the LIM and fit between those pesky tight spaces, such as the turbine and the front LIM runner like I have in my FD. Thoughts?
Did you end up trying this by chance? Would only have to stack 3x to get .125. “Amber mica” is that similar to lamp shade material (according to google).. I would even consider framing it in with some strips of metal, rivet together or something.
I decided to re-do my lim heat shield with a superior product that heatshield products makes. I originally was using their alum version which was rated to 900°f. I picked up the 321 stainless version with “lava” that is rated to 1800° continuous / 2200° intermittent. It’s definitely a little more arduous to form than the aluminum version, but it is double to temperature rating while still being flexible enough to form into compound shapes ( with some patience ). I wasn’t super happy with my original mounting, so I machined a few spacers that use the existing bottom lim studs along with some supports up top. I fabricated a cover for the FPR also. That should help keep the heat off of that as well. Here is the current state. I plan to finish making the front wrap around the lim in a similar fashion to the rear. Just not exactly sure the final placement on it, but it will cover the entire lim. Will update when I get it totally wrapped up.
Did you end up trying this by chance? Would only have to stack 3x to get .125. “Amber mica” is that similar to lamp shade material (according to google).. I would even consider framing it in with some strips of metal, rivet together or something.
Haven't gotten around to it yet unfortunately. I was also thinking of framing the mounting edges with metal to give it some rigidity if the stuff was too flexy - will find out if that's necessary or not when I purchase the flexible mica sheets.
Originally Posted by rx7srbad
Can i get this stuff in the UK?
McMaster-Carr does ship internationally, but it will probably be rather spendy to ship it there. I'd look for similar industrial supply shops local to the UK first.
Originally Posted by gdub29e
I decided to re-do my lim heat shield with a superior product that heatshield products makes. I originally was using their alum version which was rated to 900°f. I picked up the 321 stainless version with “lava” that is rated to 1800° continuous / 2200° intermittent. It’s definitely a little more arduous to form than the aluminum version, but it is double to temperature rating while still being flexible enough to form into compound shapes ( with some patience ). I wasn’t super happy with my original mounting, so I machined a few spacers that use the existing bottom lim studs along with some supports up top. I fabricated a cover for the FPR also. That should help keep the heat off of that as well. Here is the current state. I plan to finish making the front wrap around the lim in a similar fashion to the rear. Just not exactly sure the final placement on it, but it will cover the entire lim. Will update when I get it totally wrapped up.
it is great to see people working this very important problem area. let's see other fixes.
Having the engineer perspective (good/bad, right/wrong) leaves me going down some odd paths, but right now it’s my heat shield (custom shape to match a set of twins) The many threads on the subject are a bit older now and seem to lack some technical info.
I read through HC’s entire web pages, and immediately gravitated towards the mica topic, thanks HC. Mica just seems like a great fit for cost vs value. I looked into some composites, Al alloys, double layer aluminum (F1) but too much $ and headaches. I might end up trying the flexible stuff to see.
I saw the lava kit too, so thanks for the input. Seems to be a readily available choice that will work, have considered that route as well. Good to know you were able to use
02-12-23, 09:34 AM
