Drivetrain How to get 80% thermal efficiency from the stock IC & scoop
My little dose of LITHIUM
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From: Albuquerque New Mexico
Steve: Well, we keep coming back to it, so why not? I think we'll be seeing an IC exit duct for the DFIC shortly. As so many have said, it's a matter of getting lots of air in, and out, of the IC. This is just a simpler challenge with the DFIC, but doesn't mean the stock IC isn't worth improving on these grounds.
6th Gear
Joined: Mar 2006
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From: Northampton MA
Steve: Well, we keep coming back to it, so why not? I think we'll be seeing an IC exit duct for the DFIC shortly. As so many have said, it's a matter of getting lots of air in, and out, of the IC. This is just a simpler challenge with the DFIC, but doesn't mean the stock IC isn't worth improving on these grounds.
i posted this over on the dfic but i'll put it to you also; why not a shaker hood for the dfic? redesign the ic horns to allow the dfic to protrude thru the hood with a cool carbon fiber or whatever scoop on it . the scoop would be flow thru of course .
6th Gear
Joined: Sep 2002
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From: Hampton, VA
The forthcoming exit duct, if done properly, will be a better idea.
5th Gear
Joined: Jun 2003
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From: Naw-folk, VA
After seeing a beautiful Elise this weekend, clearly an exit duct makes good sense to people making cars a lot faster than Mini's. If M7 puts out a cool exit vent for the DFIC, I can't really forsee a different IC in my future. 
thank you and very, very nice work.
"For example serious hard core racers have been known to tape their exhaust headers in the engine bay with thermal insulation tape and while that produces a cooler engine bay eventually it destroys the header which is all taped up because the heat has no where to go except out to the exhaust."
Is this true?
Is this true?
If you are taking the trouble to do this, don't neglect that lower part of the inlet manifold, especially the side facing the radiator hose. Next time you stop the car, feel how hot this rad hose is, and you'll be amazed that it sits right up against a part that so much upstream effort has been put into cooling!
6th Gear
Joined: Mar 2006
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From: Northampton MA
Some people use header wrap for street cars too. I used some for a long time on my old SR20 powered Nissan Sentra with no problems. Back then I was told that two problems that you can run into when using exhaust wrap is moisture and rust, but these are much more common when the wrap is used on a mid-pipe. If the moisture gets under the wrap it will can cause the exhaust pipe to rust and weaken the metal. Then, when it gets hot, the wrap won't let the pipe expand and can cause it to collapse.
My Spitfire had wrap on the TT headers since 85. The wrap was removed 3 weeks ago, yea, there is some rust. I'll bead blast, reseal & re-wrap when time permits.
6th Gear
Joined: Sep 2002
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From: Hampton, VA
The exit vent is being worked as we post. I beleive an exit vent will only mariginally help IC Thermal efficiency because I don't believe that the air is presently being trapped under the bonnet to the point that it is pressurizing and affecting inbound air. However, it should be most useful in dumping heat build up when the car is not in motion.
A well designed exit duct is as important as as the entrance duct.
Only Sidlike vents will help under static conditions. Or a BFF*
Air pressure trapped might not be true but there is no doubt that air flowing under the hood adds to the flow. Minimally? Maybe, I really don't know but add it does. Like I said, I was talking about track speeds. The less you add to flow under the car the better.
* Big Friggin' Fan
The stock scoop & IC work reasonably well. Various figures have been reported for thermal efficiency of the stock set-up (i.e., [Tin-Tout]/[Tin-Tamb], so that at 100% efficiency the outlet temp = ambient). These range from 55% to 70%, and mostly sit around the low 60's. My own tests have shown 55% to 68%, which is in line with what others have measured.
To do better than stock, paying $500-$800 for a bigger IC seems to be the rule. I could find a thermal efficiency posted for only one after maket IC, the M7 DFIC, at 71%. You can do better than this, for less than $50 and a bit of time! Follow these steps to get a reliable TE of around 80%:
Insulate the IC
That's right - the IC has many surfaces exposed to hot air from the engine, not exposed to cold flowing air. These include the front and back, and the bottom surfaces of the channels (between the fins, facing the engine). I think many of the after market ICs really suffer from heat absorption, especially those that extend back over the spark plugs. I'll go out on a limb and say that the main benefit of the M7 DFIC is relative immunity from engine heat, due to its horizontal orientation. You can do just as well, though, with some insulation on the stock IC.
Here is a pic of my IC with the ends insulated with silicone foam, and the bottom insulated with self-stick woven glass fiber with reflective aluminum (not great for reducing heat conduction, but good for radiant heat transfer).
https://www.northamericanmotoring.co...=&ppuser=16996
I've also insulated the inlet manifold from the radiator hose and the SC exit horn. These are very hot items, and close to the air inlet manifold. Although the IC outlet air temps are not directly affected by the downstream intake manifold, it just seemed like the right thing to do, and very easy as well.
https://www.northamericanmotoring.co...=&ppuser=16996
Make a better IC diverter
The stock diverter, as many have attested, could use some improvements. It doesn't use the air from the right side of the scoop, it has only one fin to divert the air downwards, it leaves gaps on the left and right sides of the IC, as well as a big gap between it and scoop. You could buy the Alta version, or make you own that is probably better. Here is mine. It has 2 fins, and additional foam to prevent leakage. I've left the stock foam "U" in place. As you can see, my diverter extends much farther forward than than stock piece, so it can meet up with the scoop (more this later).
https://www.northamericanmotoring.co...=&ppuser=16996
To get the diverter to mate up well with the scoop, I found I had to remove the two front IC mounting brackets. These hold the diverter up too high, so if extended it runs into the scoop instead of under it. Here is a pic of the IC on the car. If you look closely at the far left side, you can see a black "undermount" bracket I made, so that the IC is at least held on 3 of the 4 corners:
https://www.northamericanmotoring.co...=&ppuser=16996
Open up the stock "mailbox slot", and eliminate the scoop - diverter gap
The stock scoop has two pieces - the outer painted part, and a black plastic inner piece. The bottom section of the inner piece forms an overly narrow slot, and also interferes with extending the diverter forward to eliminate the gap. Cut the bottom of the inner scoop off, like this:
https://www.northamericanmotoring.co...0&ppuser=16996
This probably gives at least 20% more area for flow. Next, glue some rubber strips on the bottom of the painted outer scoop, so they extend over your diverter. Here are the rubber strips I glued on:
https://www.northamericanmotoring.co...0&ppuser=16996
Since the rubber is black, you can't see them from the outside. The scoop looks totally normal. The idea is to have the scoop and the diverter mate up like this drawing tries to show, so that the engine can move back and forth without opening up a gap:
https://www.northamericanmotoring.co...0&ppuser=16996
If you do all this, what do you get?
Here is some data I logged today, under a variety of conditions. I forgot to mention in the table that ambient temp ranged from 60 to 62 F, so I used 61 F for the calcs. The best TEs are found during acceleration, probably because the thermal mass of the IC helps cool the inlet air during these brief periods. Averaging just the cruising values, though, gives 79.9% TE .
https://www.northamericanmotoring.co...0&ppuser=16996
If you do nothing else, take the first step and insulate the IC. I did the diverter/scoop mod first, but adding the insulation makes a noticeable in the seat-of-the-pants, particularly after idling the engine a while.
Also keep in mind, I have no OCC! So there is still room for some small improvement!
To do better than stock, paying $500-$800 for a bigger IC seems to be the rule. I could find a thermal efficiency posted for only one after maket IC, the M7 DFIC, at 71%. You can do better than this, for less than $50 and a bit of time! Follow these steps to get a reliable TE of around 80%:
Insulate the IC
That's right - the IC has many surfaces exposed to hot air from the engine, not exposed to cold flowing air. These include the front and back, and the bottom surfaces of the channels (between the fins, facing the engine). I think many of the after market ICs really suffer from heat absorption, especially those that extend back over the spark plugs. I'll go out on a limb and say that the main benefit of the M7 DFIC is relative immunity from engine heat, due to its horizontal orientation. You can do just as well, though, with some insulation on the stock IC.
Here is a pic of my IC with the ends insulated with silicone foam, and the bottom insulated with self-stick woven glass fiber with reflective aluminum (not great for reducing heat conduction, but good for radiant heat transfer).
https://www.northamericanmotoring.co...=&ppuser=16996
I've also insulated the inlet manifold from the radiator hose and the SC exit horn. These are very hot items, and close to the air inlet manifold. Although the IC outlet air temps are not directly affected by the downstream intake manifold, it just seemed like the right thing to do, and very easy as well.
https://www.northamericanmotoring.co...=&ppuser=16996
Make a better IC diverter
The stock diverter, as many have attested, could use some improvements. It doesn't use the air from the right side of the scoop, it has only one fin to divert the air downwards, it leaves gaps on the left and right sides of the IC, as well as a big gap between it and scoop. You could buy the Alta version, or make you own that is probably better. Here is mine. It has 2 fins, and additional foam to prevent leakage. I've left the stock foam "U" in place. As you can see, my diverter extends much farther forward than than stock piece, so it can meet up with the scoop (more this later).
https://www.northamericanmotoring.co...=&ppuser=16996
To get the diverter to mate up well with the scoop, I found I had to remove the two front IC mounting brackets. These hold the diverter up too high, so if extended it runs into the scoop instead of under it. Here is a pic of the IC on the car. If you look closely at the far left side, you can see a black "undermount" bracket I made, so that the IC is at least held on 3 of the 4 corners:
https://www.northamericanmotoring.co...=&ppuser=16996
Open up the stock "mailbox slot", and eliminate the scoop - diverter gap
The stock scoop has two pieces - the outer painted part, and a black plastic inner piece. The bottom section of the inner piece forms an overly narrow slot, and also interferes with extending the diverter forward to eliminate the gap. Cut the bottom of the inner scoop off, like this:
https://www.northamericanmotoring.co...0&ppuser=16996
This probably gives at least 20% more area for flow. Next, glue some rubber strips on the bottom of the painted outer scoop, so they extend over your diverter. Here are the rubber strips I glued on:
https://www.northamericanmotoring.co...0&ppuser=16996
Since the rubber is black, you can't see them from the outside. The scoop looks totally normal. The idea is to have the scoop and the diverter mate up like this drawing tries to show, so that the engine can move back and forth without opening up a gap:
https://www.northamericanmotoring.co...0&ppuser=16996
If you do all this, what do you get?
Here is some data I logged today, under a variety of conditions. I forgot to mention in the table that ambient temp ranged from 60 to 62 F, so I used 61 F for the calcs. The best TEs are found during acceleration, probably because the thermal mass of the IC helps cool the inlet air during these brief periods. Averaging just the cruising values, though, gives 79.9% TE
. https://www.northamericanmotoring.co...0&ppuser=16996
If you do nothing else, take the first step and insulate the IC. I did the diverter/scoop mod first, but adding the insulation makes a noticeable in the seat-of-the-pants, particularly after idling the engine a while.
Also keep in mind, I have no OCC! So there is still room for some small improvement!
6th Gear
Joined: Jan 2006
Posts: 1,808
Likes: 3
dude thx for the pioneering. i did your mod today and all i can say is wow!!!! the post i/c horn was stone cold. i also sealed and insulated all but the pre s/c tube and the intake (time was factor) plus i don't want atomization issues at the intake. but man nice and cold .
5th Gear
Joined: Jul 2005
Posts: 746
Likes: 1
From: Miami, FL
dude thx for the pioneering. i did your mod today and all i can say is wow!!!! the post i/c horn was stone cold. i also sealed and insulated all but the pre s/c tube and the intake (time was factor) plus i don't want atomization issues at the intake. but man nice and cold .
Ken
i was doing my bpv so while the i/c was sitting in soapy water i did the insulating. i've got an older style intake with a k&n filter so the box was pulling alot of engine bay heat in . it can be done in a couple hrs. without doing the intake to the s/c and the intake manifold. got all at lowes . but don't apply the rubber pipe tape straight to anything hot , i put the reflective tape on the i/c first then two layers of rubber foam then reflective again. . try it out it's cheap enough. the car is smooth.
a little heat in the intake manifold is not a bad thing it helps atomize the fuel if it's too cold it's crap. being that i don't know the ideal temp. for these cars i thought it best to leave it alone .
6th Gear
Joined: Jan 2006
Posts: 1,808
Likes: 3
i was doing my bpv so while the i/c was sitting in soapy water i did the insulating. i've got an older style intake with a k&n filter so the box was pulling alot of engine bay heat in . it can be done in a couple hrs. without doing the intake to the s/c and the intake manifold. got all at lowes . but don't apply the rubber pipe tape straight to anything hot , i put the reflective tape on the i/c first then two layers of rubber foam then reflective again. . try it out it's cheap enough. the car is smooth.
Thanks though....
My little dose of LITHIUM
iTrader: (1)
Joined: Jul 2005
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From: Albuquerque New Mexico
OK, I don't want to hijack this thread, and will start a new one if warranted. But for those of us with a DFIC, (and mine, like many, has ceramic coating on the underside), I wonder if doing the insulating thing is a good idea. Here's my logic (I'm no physicist!):
If the heat is coming from inside the IC horns and IC, then you want a coating that dissipates heat, not reflects it. If the heat is being transfered -to- these parts from the engine bay, then you want a reflective insulator like the thermal blanket. The question I have is: which scenario is it? Because if it's #1, then putting the insulating material in the horns and IC would tend to keep heat -in- the parts and would raise AITs at stoplights and such, (?)
thanks,
If the heat is coming from inside the IC horns and IC, then you want a coating that dissipates heat, not reflects it. If the heat is being transfered -to- these parts from the engine bay, then you want a reflective insulator like the thermal blanket. The question I have is: which scenario is it? Because if it's #1, then putting the insulating material in the horns and IC would tend to keep heat -in- the parts and would raise AITs at stoplights and such, (?)
thanks,
6th Gear
Joined: Mar 2006
Posts: 1,710
Likes: 1
From: Northampton MA
OK, I don't want to hijack this thread, and will start a new one if warranted. But for those of us with a DFIC, (and mine, like many, has ceramic coating on the underside), I wonder if doing the insulating thing is a good idea. Here's my logic (I'm no physicist!):
If the heat is coming from inside the IC horns and IC, then you want a coating that dissipates heat, not reflects it. If the heat is being transfered -to- these parts from the engine bay, then you want a reflective insulator like the thermal blanket. The question I have is: which scenario is it? Because if it's #1, then putting the insulating material in the horns and IC would tend to keep heat -in- the parts and would raise AITs at stoplights and such, (?)
thanks,
If the heat is coming from inside the IC horns and IC, then you want a coating that dissipates heat, not reflects it. If the heat is being transfered -to- these parts from the engine bay, then you want a reflective insulator like the thermal blanket. The question I have is: which scenario is it? Because if it's #1, then putting the insulating material in the horns and IC would tend to keep heat -in- the parts and would raise AITs at stoplights and such, (?)
thanks,
Thought about this one for a bit...
I think insulating the post IC horn might be a good idea, as the air coming out of the IC should be cooler than the air that flows through the radiator. But the SC to IC horn is sometimes hotter (high RPM and load) than the air in the engine bay, but at cruise and light load, it's cooler..... So flip a coin on that one!
Matt
Matt
I think insulating the post IC horn might be a good idea, as the air coming out of the IC should be cooler than the air that flows through the radiator. But the SC to IC horn is sometimes hotter (high RPM and load) than the air in the engine bay, but at cruise and light load, it's cooler..... So flip a coin on that one!
Matt
Matt
My little dose of LITHIUM
iTrader: (1)
Joined: Jul 2005
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From: Albuquerque New Mexico
Hang on Herbie-- I remember your post about how you could touch the horn after hours of driving, so I'm confused now. Perhaps you were speaking of the IC-out horn, as opposed to the IC-in horn?
Here's how I see the insulation thing.
The air flows through these systems:
1. The air box and filter. Insulate this system and seal it from the engine bay.
2. The intake tube to the throttle body. Plastic or silicone, but insulate anyway, why not?
3. The inlet to the SC. Made of plastic, probably pretty well thermally insulated but might be wrapped.
4. The SC. Ah too big to worry about, and it mostly happens on the inside.
5. The SC to IC horn (IC-in horn). Leave this sucker alone, or coat with some thermal dissipating product. Don't wrap or insulate.
6. The IC. Depends, insulate the stock one, don't insulate the DFIC.
7. The IC-out horn. Air in here should be cool, thanks to the IC, so insulate this sucker.
8. The intake manifold. Close to the radiator hose and engine block, so insulate this as well.
What do you think?
Here's how I see the insulation thing.
The air flows through these systems:
1. The air box and filter. Insulate this system and seal it from the engine bay.
2. The intake tube to the throttle body. Plastic or silicone, but insulate anyway, why not?
3. The inlet to the SC. Made of plastic, probably pretty well thermally insulated but might be wrapped.
4. The SC. Ah too big to worry about, and it mostly happens on the inside.
5. The SC to IC horn (IC-in horn). Leave this sucker alone, or coat with some thermal dissipating product. Don't wrap or insulate.
6. The IC. Depends, insulate the stock one, don't insulate the DFIC.
7. The IC-out horn. Air in here should be cool, thanks to the IC, so insulate this sucker.
8. The intake manifold. Close to the radiator hose and engine block, so insulate this as well.
What do you think?
yeah that's what i said i can't understand it today it was hot . the oulet i/c horn i mean. before it was cold. maybe i just drove it harder. i'm not being wicked scientific here either but i will still say the difference is notible . thx again to inimini for this idea. i am gonna get some of that gold foil though. the guy at ktr said it was the cats' *** .