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  1. #51
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    Click here to enlarge Originally Posted by Zasquatch Click here to enlarge
    I don't know why everyone is so concerned about the heat difference.... The spacer should help with conduction off the head. Other than that, do you think there is THAT big of a difference between the heat transfer rates through very thin plastic vs. comparatively thick aluminum alloy? I have my Heat Transfer book sitting right in front of me, maybe I'll do a quick calc later... Something tells me you are all overreacting though Click here to enlarge
    Aluminium alloy has a heat transfer coefficient of 160 (plain aluminium 200) vs stainless steel 21 and plastic is even lower. You wouldn't use metal for heat insulation, or would you? Click here to enlarge
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  2. #52
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    Click here to enlarge Originally Posted by Autobahn335i Click here to enlarge
    Aluminium alloy has a heat transfer coefficient of 160 (plain aluminium 200) vs stainless steel 21 and plastic is even lower. You wouldn't use metal for heat insulation, or would you? Click here to enlarge
    I'm just thinking aloud here Click here to enlarge

    Plastic should have a k value that is below 1.... like 0.3ish maybe? My point though, is that thickness plays a role here too. The OEM plastic manifold is very thin, hence all the support ribs to handle the pressures. An Al manifold would be considerably thicker I would think, and thus take longer to heat soak vs. Al in the same thickness as the plastic. The point I am trying to make is that while Aluminum is a much better conductor (think heatsinks on electronics, or hell, all our FMIC's), it may not make that much of a difference under the engine bay.... It just may take less time to "come up to temperature" vs the plastic option. In the end I would think the surface temp on the plastic vs. the surface temp on the Al would be equal after a certain amount of driving.

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    Click here to enlarge Originally Posted by Mat Morkin Click here to enlarge
    DBFIU, could I send young file and have you sim the air flow? I am changing the plenum up a bit, the protrusion has to stay bc of the oil filter body, sucks.
    Mat, you can send me the files in STEP204 or STEP214 or Parasolid format. I can simulate the airflow for you, the only problem is I dont have the stock manifold to compare it too. If you have real internal dimensions of the stock manifold I can do a back to back comparison.
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  4. #54
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    Click here to enlarge Originally Posted by Zasquatch Click here to enlarge
    I'm just thinking aloud here

    Plastic should have a k value that is below 1.... like 0.3ish maybe? My point though, is that thickness plays a role here too. The OEM plastic manifold is very thin, hence all the support ribs to handle the pressures. An Al manifold would be considerably thicker I would think, and thus take longer to heat soak vs. Al in the same thickness as the plastic. The point I am trying to make is that while Aluminum is a much better conductor (think heatsinks on electronics, or hell, all our FMIC's), it may not make that much of a difference under the engine bay.... It just may take less time to "come up to temperature" vs the plastic option. In the end I would think the surface temp on the plastic vs. the surface temp on the Al would be equal after a certain amount of driving.
    Not trying to start a pissing contest here, but the surface temperature both inside and outside for the alum manifold will be much hotter than the plastic and it will get there faster. The thermal conductivity of alum is 100s of times that of plastic. The amount of time it takes to get up to temp is dependant on the thermal time constant which depends on the heat capacity which is also much lower for aluminum. You should try a simple hand calculation with properties of plastic, assume an h coefficient inside the manifold by calculating it using dittius-boelter internal flow correlation. For the outside of the manifold, assume a convective h of about 25-35 BTU/ft2-hr-R (just a guess for now) and assume reasonable air temperatures.

    Take an approximate surface area of both inside and outside and convert that to a flat plate with cross flow on both sides, then compute the surface temperatures using reasonable thicknesses for the plastic (maybe 1/4" thick) and the aluminum (maybe 1/2" thick). If you have the time to do it. Also dont forget you will need air properties for both the internal and external surfaces of the manifold which will be different, you probably know that though.

    Either way, he should make it out of aluminum because the flow gains will heavily outweigh the heat pick up loss I am sure of that.
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    Click here to enlarge Originally Posted by DBFIU Click here to enlarge

    Either way, he should make it out of aluminum because the flow gains will heavily outweigh the heat pick up loss I am sure of that.
    This

  6. #56
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    I was unaware we were pissing lol, the last time I looked at a heat transfer problem was 5 years ago! Good points, I may try to tackle this for my own curiousity next week.

    I agree he should make it for the flow gains alone. I would be very curious to see your CFD results Click here to enlarge

    Click here to enlarge Originally Posted by DBFIU Click here to enlarge
    Not trying to start a pissing contest here, but the surface temperature both inside and outside for the alum manifold will be much hotter than the plastic and it will get there faster. The thermal conductivity of alum is 100s of times that of plastic. The amount of time it takes to get up to temp is dependant on the thermal time constant which depends on the heat capacity which is also much lower for aluminum. You should try a simple hand calculation with properties of plastic, assume an h coefficient inside the manifold by calculating it using dittius-boelter internal flow correlation. For the outside of the manifold, assume a convective h of about 25-35 BTU/ft2-hr-R (just a guess for now) and assume reasonable air temperatures.

    Take an approximate surface area of both inside and outside and convert that to a flat plate with cross flow on both sides, then compute the surface temperatures using reasonable thicknesses for the plastic (maybe 1/4" thick) and the aluminum (maybe 1/2" thick). If you have the time to do it. Also dont forget you will need air properties for both the internal and external surfaces of the manifold which will be different, you probably know that though.

    Either way, he should make it out of aluminum because the flow gains will heavily outweigh the heat pick up loss I am sure of that.

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    Click here to enlarge Originally Posted by DBFIU Click here to enlarge
    Either way, he should make it out of aluminum because the flow gains will heavily outweigh the heat pick up loss I am sure of that.
    If the PERFORMANCE gains outweigh the heat pick up loss too, then I'm in Click here to enlarge
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    Click here to enlarge Originally Posted by DBFIU Click here to enlarge
    Either way, he should make it out of aluminum because the flow gains will heavily outweigh the heat pick up loss I am sure of that.
    I was just going to make a comment about the two hot ass turbos that no one seems to complain too much about. Turbos add tons of power, obviously, but they are also hot as $#@!.

    I'll take 3 steps forward if I only need to take 1 back. Beats taking 0 steps forward.

    Lets see proof of concept, then we can nit-pick. (not directed at you)

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    Click here to enlarge Originally Posted by Doyle Click here to enlarge
    I was just going to make a comment about the two hot ass turbos that no one seems to complain too much about. Turbos add tons of power, obviously, but they are also hot as $#@!.

    I'll take 3 steps forward if I only need to take 1 back. Beats taking 0 steps forward.

    Lets see proof of concept, then we can nit-pick. (not directed at you)
    Yea I just like to nit pick for fun Click here to enlarge

    I think the manifold will be great to have and there are definite gains there because the stock one is $#@!ty.
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  10. #60
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    Click here to enlarge Originally Posted by DBFIU Click here to enlarge
    Not trying to start a pissing contest here, but the surface temperature both inside and outside for the alum manifold will be much hotter than the plastic and it will get there faster. The thermal conductivity of alum is 100s of times that of plastic. The amount of time it takes to get up to temp is dependant on the thermal time constant which depends on the heat capacity which is also much lower for aluminum. You should try a simple hand calculation with properties of plastic, assume an h coefficient inside the manifold by calculating it using dittius-boelter internal flow correlation. For the outside of the manifold, assume a convective h of about 25-35 BTU/ft2-hr-R (just a guess for now) and assume reasonable air temperatures.

    Take an approximate surface area of both inside and outside and convert that to a flat plate with cross flow on both sides, then compute the surface temperatures using reasonable thicknesses for the plastic (maybe 1/4" thick) and the aluminum (maybe 1/2" thick). If you have the time to do it. Also dont forget you will need air properties for both the internal and external surfaces of the manifold which will be different, you probably know that though.

    Either way, he should make it out of aluminum because the flow gains will heavily outweigh the heat pick up loss I am sure of that.
    Swooooooosh. That was the sound of your post going over my head. Well, everything except the last sentence...lol
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  11. #61
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    Click here to enlarge Originally Posted by nafoo Click here to enlarge
    Swooooooosh. That was the sound of your post going over my head. Well, everything except the last sentence...lol
    I did stay at a holidy in express last night.
    Some people live long, meaningful lives.

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  12. #62
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    Click here to enlarge Originally Posted by DBFIU Click here to enlarge
    I did stay at a holidy in express last night.
    holiday*** inn***

    apparently not Click here to enlarge
    -'09 135i MT - Custom 6466 ST - 680whp Click here to enlarge
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    Click here to enlarge Originally Posted by DBFIU Click here to enlarge
    Either way, he should make it out of aluminum because the flow gains will heavily outweigh the heat pick up loss I am sure of that.
    Click here to enlarge thank you sir!

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    POC will definitely be key. Like I said in my earlier post, there will be many alternatives to counter high temps. I highly doubt the heat generated from the N54 will be anything like the Z32 bay, and it still ran nails! Good luck fetching anything you drop in there! Click here to enlarge
    Attached Images Attached Images  

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    Very clean setup there man..is that yours?

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    Guys, I need help on the size, and restrictions. It is going to ne made out of Aluminum, stop arguing about it. I need ideas on how to make the plenum larger...I don't do plastic, steel will weigh to much and stainless cost mucho moneys. I order a sheet of 3/16 phenolic today. Look for a spacer soon. Get over the material and stay on task. Lol.

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    Click here to enlarge Originally Posted by DBFIU Click here to enlarge
    Mat, you can send me the files in STEP204 or STEP214 or Parasolid format. I can simulate the airflow for you, the only problem is I dont have the stock manifold to compare it too. If you have real internal dimensions of the stock manifold I can do a back to back comparison.
    Email?

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    Click here to enlarge Originally Posted by Mat Morkin Click here to enlarge
    Guys, I need help on the size, and restrictions. It is going to ne made out of Aluminum, stop arguing about it. I need ideas on how to make the plenum larger...I don't do plastic, steel will weigh to much and stainless cost mucho moneys. I order a sheet of 3/16 phenolic today. Look for a spacer soon. Get over the material and stay on task. Lol.
    Hahaha. I hope this doesn't turn into the same situation as the inlet pipes on n54tech where the dude got all butthurt that he wouldn't dyno his car.

    Do your damn thing and lets push this envelope!

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    Click here to enlarge Originally Posted by Mat Morkin Click here to enlarge
    Email?
    PM
    Some people live long, meaningful lives.

    Other people eat shit and die.

    I'm not racist, I hate everybody equally; especially fat people.


    Click here to enlarge

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    Click here to enlarge Originally Posted by Mat Morkin Click here to enlarge
    Guys, I need help on the size, and restrictions. It is going to ne made out of Aluminum, stop arguing about it. I need ideas on how to make the plenum larger...I don't do plastic, steel will weigh to much and stainless cost mucho moneys. I order a sheet of 3/16 phenolic today. Look for a spacer soon. Get over the material and stay on task. Lol.
    Agree.

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    Click here to enlarge Originally Posted by Mat Morkin Click here to enlarge
    Guys, I need help on the size, and restrictions. It is going to ne made out of Aluminum, stop arguing about it. I need ideas on how to make the plenum larger...I don't do plastic, steel will weigh to much and stainless cost mucho moneys. I order a sheet of 3/16 phenolic today. Look for a spacer soon. Get over the material and stay on task. Lol.


    Like I said aluminum is fine, just run with it. I will help you design the manifold for optimal flow charateristics; you figure out how to manufacture it, send me your current iteration and I will suggest some design changes as I begin to simulate it.
    Some people live long, meaningful lives.

    Other people eat shit and die.

    I'm not racist, I hate everybody equally; especially fat people.


    Click here to enlarge

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    Click here to enlarge Originally Posted by DBFIU Click here to enlarge
    Like I said aluminum is fine, just run with it. I will help you design the manifold for optimal flow charateristics; you figure out how to manufacture it, send me your current iteration and I will suggest some design changes as I begin to simulate it.
    Now we're talkin'! Click here to enlarge

  23. #73
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    Yes, back in the glory days when Japanese cars were very heavy and over engineered.

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    Some people live long, meaningful lives.

    Other people eat shit and die.

    I'm not racist, I hate everybody equally; especially fat people.


    Click here to enlarge

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    Hey guys, I went to the drafting lab at my local Jr. College to get some pointers from my old professor on how to make the plenum exactly how I want to, look for a radical redesign in a few days. That, and I've been watching old episodes of McGyver on Netflix so it's going to be good.Click here to enlarge

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