2nd Generation Specific (1986-1992) 1986-1992 Discussion including performance modifications and technical support sections.

Serious Guru's answer only..please..

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Old Aug 16, 2006 | 10:31 PM
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Serious Guru's answer only..please..

I was thinking about fabricating an intake pipe, Aluminum or something simalair, so that it bends in a way to travel in front of the intake manifold and down somewhere like just behind either headlights...preferebly the driver side HL so it's long enough to cool the air as it travels achieving a minimal amount of pipe traveling over that damned exhaust. Locating it behind the driver side Head Light would also eliminate the need for an air box allowing me to use a cone filter.

Would anybody agree with this Idea?

And would it be recomended to cut out an intake hole on the top of the headlight cover? I think I can just put it slightly infront of my radiator right?

Also, would this allow me to coil some of the copper tubing used for the a/c theoreticaly further cooling the tube and air passing through it?

I know it sounds complicated but it's really not.
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Old Aug 16, 2006 | 10:35 PM
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Well, being as the pipe is inside the engine bay, chances are it would eventually get a bit heat soaked.
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Old Aug 16, 2006 | 10:43 PM
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Originally Posted by Street_Knight
Also, would this allow me to coil some of the copper tubing used for the a/c theoreticaly further cooling the tube and air passing through it?:
Not trying to threadjack, But I had a similar idea of cooling using a Peltier device tucked under the TII scoop. Or the possibilty of cooling an air/water IC w/ a peltier.

Would be interesting to find out if running the ac compressor would also offset the power gained w/ the cooler intake charge.
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Old Aug 16, 2006 | 10:43 PM
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Having a hole the headlight will have little effect for drawing in colder air. Use this pic while designing you CAI:

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Old Aug 16, 2006 | 10:44 PM
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yeah, I'm just trying to get the pipe as cool as possible.
Would it be a better idea to fabricate it out the front quarter panel on the passenger side?
Just make a fair sized scoop in the quarter panel with the new intake RIGHT there connected to it?
And what do you think about the a/c coil I mentioned?
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Old Aug 16, 2006 | 10:44 PM
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I'm no guru...but this is a very bad idea.

The radiator pumps out hot air. Not cold. The pipe would be heated by this air = not good.


And no, this would not eliminate the need for an airbox. The entire engine bay gets super hot .... not just the area where the stock airbox is located.


Search "prelude cold-air intake", it is (arguably?) the best.
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Old Aug 16, 2006 | 10:44 PM
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Originally Posted by carzy driver
Having a hole the headlight will have little effect for drawing in colder air. Use this pic while designing you CAI:

That does help....thank you.
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Old Aug 16, 2006 | 10:48 PM
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Originally Posted by adrock3217
I'm no guru...but this is a very bad idea.

The radiator pumps out hot air. Not cold. The pipe would be heated by this air = not good.

And no, this would not eliminate the need for an airbox. The entire engine bay gets super hot .... not just the area where the stock airbox is located.

Search "prelude cold-air intake", it is (arguably?) the best.
yeah, I'm just trying to get the pipe as cool as possible.
Would it be a better idea to fabricate it out the front quarter panel on the passenger side?
Just make a fair sized scoop in the quarter panel with the new intake RIGHT there connected to it?
And what do you think about the a/c coil I mentioned?

And I was talking about putting the intake infront...and slightly at that....of the radiator. Between that and the grill, it would only have air blowing on it while I'm driving right? Wouldn't the hotter air be behind the radiator and back like more towards the engine?
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Old Aug 16, 2006 | 10:55 PM
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The (best?) place to put the intake is to route it down *under* the passenger headlight. The piping is short, no extreme bends, and it will get a load of fresh air coming in thru the brake-duct. And no, puddles and rain won't hurt anything...


If you are going to use metal pipes of any kind, you can do a few things to avoid heat soak and the like.

High-temp paint the paint, wrap it in heat-wrap, and then high-temp paint the heat wrap a color to match whatever colors you have going in your engine bay. This will help immensly with heat soak, and will cool your intake charge dramatically.
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Old Aug 16, 2006 | 10:59 PM
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Why don't you just run a normal CAI? It accomlishes the same thing or better.
The peltier device does sound intersting. Maybe have a air-water cooler for the hot side of the peltier and a seperate water source being cooled by the other side that runs through a air-water intercooler. It would take some work to fab up properly, but might work quite well. It would take a lot of power to run a peltier of enough size to work, though. One that is large enough for a CPU draws close to 20A, and I would think you would need an even larger one for this.
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Old Aug 16, 2006 | 11:00 PM
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SEE, that's the one simple answer I needed.
Thank you.
For this would I have to cut out metal or anything to get it air from the brake duct?
I'm just trying to cover all areas before setting my car on fire. lol.
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Old Aug 16, 2006 | 11:02 PM
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To get the intake piping down into the area, you have to use a circle-saw to make the hole. And uh..your windshield washer fluid bottle needs to be removed/moved.
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Old Aug 16, 2006 | 11:14 PM
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okay....so I'm doing this right below the washer fluid is?
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Old Aug 16, 2006 | 11:18 PM
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I'm actually kinda sceptical of using the brake duct on a car that sees much heavy braking. If you do any type of auto-x or similar I would think the brake would need that fresh air to cool it. I've never actually heard whether that's true or not, just basing it on logic.
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Old Aug 16, 2006 | 11:33 PM
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Originally Posted by Sideways7
Why don't you just run a normal CAI? It accomlishes the same thing or better.
The peltier device does sound intersting. Maybe have a air-water cooler for the hot side of the peltier and a seperate water source being cooled by the other side that runs through a air-water intercooler. It would take some work to fab up properly, but might work quite well. It would take a lot of power to run a peltier of enough size to work, though. One that is large enough for a CPU draws close to 20A, and I would think you would need an even larger one for this.
Depends on how much of a heatsink to absorb intake air temps and how much of the heat to lose into the atmosphere.

Last edited by ErixHvn; Aug 16, 2006 at 11:35 PM.
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Old Aug 17, 2006 | 12:15 AM
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Ah, heat transfer! And I didn't think I'd be a "Guru".

First, the aluminum tube does not need to be insulated. Only the air a fraction of an inch from the surface will suffer from heat soak. What is more important is making a good seal to keep hot air from getting into the intake. But insulation won't hurt. If you give it a wide enough path (significantly wider than the engine intake) you don't have to worry so much about bends, either.

On that aerodynamic flow profile: The reason there is so much pressure pointing away from the headlight is because the path of flow into the headlight is blocked. If you open it air will flow in, just like it flows into the bumper.

Cooling (A/C or Peltier):
load = (engine displacement) * (engine rpms) * (specific heat of air = 1000J/kg*C = 0.240 Btu / lb.-F) * (density of air = 1.184kg/m^3 = 0.07391 lbs./ft^3) * (degrees of temperature drop)
Next multiply by 60 minutes per hour (for Btu/hour) or divide by 60 second per minute (for J/s = Watts).

So: (1.3L = 0.0013 m^3) / rev * 8000 revs / minute * 1000J/kg*C * 1.184kg/m^3 * 10C / (60s / minute) = 2050W

Peltier: A peltier is out of the question. 2050W will cost you about $600 in peltiers, not including heatsinks & fans. It would draw ~230A from your alternator, and send your mpg down the toilet.

A/C: 2050W = 7000 Btu/hour. That's bigger than the A/C cooling my bedroom. My A/C draws 450W (0.6HP), so we're looking at about 1HP to drive the A/C. The gain from running 10C cooler is about 5HP. The A/C designed to cool the car's interior probably isn't as strong as the one designed to cool my bedroom. I'd guess about 1mpg lost to the A/C, since (I assume) it's not always on full blast. If you want to run 20C cooler (~+10HP), then simply double the size of the A/C. Triple for 30C, etc.

The density of turbocharged air is higher and hence requires a bigger A/C.

I double checked by math, but I could still make a mistake. Somebody else want to double check my math?

The A/C is just a Freon compressor/decompressor that would increase the density of air by cooling it. IMO, why not skip the complication and simply compress the air? That's a turbocharger. Then again chilled air puts less stress on your engine. I'd just go with a CAI.

Last edited by ericgrau; Aug 17, 2006 at 12:33 AM.
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Old Aug 17, 2006 | 01:25 AM
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so if I could coil the a/c tubing...that copper crap....around my cold air intake, that would be worth my time?
But I would have to run my a/c for this application to serve a purpose right?
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Old Aug 17, 2006 | 02:38 AM
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Originally Posted by ericgrau
Cooling (A/C or Peltier):
load = (engine displacement) * (engine rpms) * (specific heat of air = 1000J/kg*C = 0.240 Btu / lb.-F) * (density of air = 1.184kg/m^3 = 0.07391 lbs./ft^3) * (degrees of temperature drop)
Next multiply by 60 minutes per hour (for Btu/hour) or divide by 60 second per minute (for J/s = Watts).

So: (1.3L = 0.0013 m^3) / rev * 8000 revs / minute * 1000J/kg*C * 1.184kg/m^3 * 10C / (60s / minute) = 2050W

Peltier: A peltier is out of the question. 2050W will cost you about $600 in peltiers, not including heatsinks & fans. It would draw ~230A from your alternator, and send your mpg down the toilet.

A/C: 2050W = 7000 Btu/hour. That's bigger than the A/C cooling my bedroom. My A/C draws 450W (0.6HP), so we're looking at about 1HP to drive the A/C. The gain from running 10C cooler is about 5HP. The A/C designed to cool the car's interior probably isn't as strong as the one designed to cool my bedroom. I'd guess about 1mpg lost to the A/C, since (I assume) it's not always on full blast. If you want to run 20C cooler (~+10HP), then simply double the size of the A/C. Triple for 30C, etc.

The density of turbocharged air is higher and hence requires a bigger A/C.

I double checked by math, but I could still make a mistake. Somebody else want to double check my math?

The A/C is just a Freon compressor/decompressor that would increase the density of air by cooling it. IMO, why not skip the complication and simply compress the air? That's a turbocharger. Then again chilled air puts less stress on your engine. I'd just go with a CAI.
Talk about making a simple CAI complex...
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Old Aug 17, 2006 | 02:50 AM
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I know right.....
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Old Aug 17, 2006 | 06:33 AM
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Originally Posted by adrock3217
To get the intake piping down into the area, you have to use a circle-saw to make the hole. And uh..your windshield washer fluid bottle needs to be removed/moved.
Yep, throw the windshield washer bottle away...
Get a 4" (or smaller) hole saw and go to town...
Plumb piping down under there...


-Ted
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Old Aug 17, 2006 | 06:35 AM
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Originally Posted by carzy driver
Talk about making a simple CAI complex...
Layman's terms...
"It's a waste of time."
Too much energy in minus resistive losses equals not enough cooling to make a dent...


-Ted
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Old Aug 19, 2006 | 09:53 PM
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Thanks RETed. That's exactly what I was going to say.
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Old Aug 19, 2006 | 10:03 PM
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fenderwell all the way



i blocked off the brake cooling duct (not shown in pic) and haven't warped the rotor yet... even with my brakes dragging on the highway for a couple miles. i auto-x as well and have seen no adverse effects.
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Old Aug 19, 2006 | 10:07 PM
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Why did you block it off? :\


You could have routed the air around the filter..or just..left it open..

Afraid of water? If you think your intake (non-turbocharged) is going to be able to suck up more then water vapor, you'd be wrong :-O


Edit: And to whoever does this mod, the above is not the ideal hole size..you should really make it a tad bigger than the pipe you are putting through it...unless you like mega vibration, and eventually wear. :-X
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Old Aug 19, 2006 | 10:59 PM
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Originally Posted by adrock3217
Why did you block it off? :\


You could have routed the air around the filter..or just..left it open..

Afraid of water? If you think your intake (non-turbocharged) is going to be able to suck up more then water vapor, you'd be wrong :-O


Edit: And to whoever does this mod, the above is not the ideal hole size..you should really make it a tad bigger than the pipe you are putting through it...unless you like mega vibration, and eventually wear. :-X
i blocked it off on the other end... not the bumper inlet which is what you're thinking. i didn't want the tire throwing rocks on the filter thru the brake duct. i just added piece of plasting to the fenderwell shroud.

the filter gets plenty of air thru the front. as far as routing it around the filter. did you think about how much fabrication that would require? and to what end?

and where exactly am i going to get mega vibration and wear?
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