We all know the engine bay in the average performance rotary can get hotter than hell, and one thing you don't want is the engine breathing it's own hot air. And while a good cold air intake gets you a long way, it doesn't solve the problem of heat soak in the intercooler pipes. On that issue I had idea on how to make heat resistant intercooler piping.

The basic concept is a double walled pipe with a sealed void in between, this void is made devoid of air (i.e a vacuum), leaving the heat in the engine bay without a medium to be conducted via, thus creating a heat barrier. The gap between the two walls need only be 1/4 -1/2" to work, say a 2.5" pipe inside a 3" pipe.



The top diagram shows my idea, the lower a normal single walled intercooler pipe.

Now to construct the double walled pipe, each straight and curved section would have to be a separate section of pipe, as you of course couldn't feed the straight sections of the inner pipe around the corners of the outer pipe.

So the logical way to build the pipes would be to start with the flange for one end of the pipe, and weld on the first section of inner pipe. Then on the other end of that section of the inner pipe weld on 3 or 4 spaces, to hold the inner pipe central to the outer. Then slide the first section of the outer pipe over the spacers and down the inner pipe to the flange. Then weld the outer pipe to the flange, then at the other end of the outer pipe, weld that to the spacers already welded to the inner pipe. You would then repeat the process, welding the second section of the inner pipe to the first section of inner pipe, then weld on another set of spacers to the second section of inner pipe. Then weld the second outer section of pipe to the first outer section of the pipe, and the second set of spacers. And so on and so on for each section of the pipe, until you finally weld on the flange and the other end.

Once the pipe itself is constructed, you would need to create the vacuum in the void between the two walls. To do this you simply drill a hole in the outer wall and mount a check valve in it, you then attach an vacuum pump to the valve via a hose and pump out as much air as you can. Once happy you have out all the air you can, you remove the hose from the valve and cap the valve to prevent it leaking.


Now this is over simplification of the work involved, in fact it would be so time consuming that it would be best if your were related to a fabricator to keep costs down. But what you would be left with is a set of custom intercooler pipes, whose conductive surface area has been reduced by a factor of thousands, with only the flanges & the internal spacers directly conducting heat from the outer to the inner wall of the pipe.

Wow, that got kinda long, I hope anyone who gets this far understands what I'm on about.

Now before everyone rips my idea to pieces or points out that someone has already done it. Please realise this is idea is a theory only and is based on my understanding of physics, which I haven't study in 12 years, and my understand of fabrication that is nearly as dated.

Yes, I know it will cost a bomb to make, for very little performance return.
Yes, I know a vented hood and insulating the pipes will have about the same effect.
Yes, I know it will be a pig to install due to the enlarge external diameter of the pipe.
Yes, I know there is no such thing as a perfect man made vacuum, so some heat will still get through.

Well, have at it. and let me know what you think.

 

I think it will work. Thermos has been doing it for years.

The only fault I see is that the spacers will transmit heat. If those are rubber then youll be fine, if they're metal you'll still see a minimal amount of heat soak.

You are correct in that the hard part will be working the two pieces together around the bend.

As always, I'm going to be an *** and tell you that its a great idea, but will the work really be worth the extra effort?

If you get a chance install a pair of MAT (manifold air temperature) sensors at the IC and engine end of your current piping. Find out how much hotter its really getting once it leaves the intercooler and gets to your motor. Then if you decide to use the insulated pipe, do the same thing and see how well it really worked.

 

Turbine engines use a similar design, but with airflow traveling through the gap to carry away the heat. However, the reason it is used on turbine engines is to protect the metal from the heat of the engine rather than to protect the engine from the heat of the engine bay.

As already posted by nevarmore, I think you are trying to solve a problem that doesn't exist. Contrary to what you hear from rice vendors, the engine bay isn't really very hot, and a straight-walled pipe transfers very little heat, especially at high airflow rates. The amount of heat soak through the pipe is insignificant for any application other than professional drag racing where even 1 or 2 hp counts. According to George Spears (Spearco Intercoolers), metal intercooler piping only adds about 4-5 deg F to the intake air, which he considers insignificant. This temperature gain would work out to a hp loss of only about a 0.6% loss (2.7 hp on a 450hp engine). Also, the metal intake manifold would pick up more heat than the pipe, anyway.

If you are that concerned about heat, then why not just make the after-cooled portion of the piping and intake manifold out of ceramic or synthetic material that acts as a good thermal barrier?

 

Which if you're talking about such small gains, will that extra 1% of power make up for carrying around a double walled pipe??

Still though, I'd love for you to prove us wrong. Slap that sumbitch on the dyno and baseline it. Take some temperature readings too. Install your pipe and dyno it again with the thermometer.

 

Stainless steal ceramic coated and then thermally wrapped would be the most economical and practical way to do this wouldn’t it.

I agree that it is not that significant of issue to warrant the money and effort, but it is a academic practice in theory that would technically increase performance, but at a cost that could probably be better spent in different areas.

 

Though as a passing thought I bet you could find an extrusion similar to your layout that has been produced or is in production for strait section. But putting it into a mandrel bender would prove to be the limiting factor for an extrusion like this. So the bends would have to be manufactured independently unless you had a great line on aerospace quality castings.

 

What about wrapping a steel pipe with that aluminum foil / foam pipe insulation tape on the aftercooled section?

 

Thats the industry standard if you feel that you need the insulation. Light, cheap, easy, but it has the drawback of being somewhat flammable and its not too flashy if youre the type who likes the engine bling.

 

leave it to 88integrals to be practical...

 

just create carbon fiber piping and you dont have to worry about heat being disapated too much.

 

I have CF piping, its only 1 1/8" though.. I bet i could get a mold for larger

 

You'd be far better to try and add cooling capacity before the intercooler where the delta T is greater, this will promote cooling easier because of the greater temperature gradient and be much more worth your while. On the "cool" side, just be smart about where you run the pipes and if you want to go all out for that extra 1/2 hp use a cheap ceramic paint and the other methods mentioned above.
Good Luck

 

Before the Intercooler the compressed air inside the piping is actually hotter than the engine bay (delta T may be greater magnitude but opposite sign). So you are in effect cooling the air inside the IC piping (good thing) and it is fine to remain non insulated.

Post intercooler it is the other way around, the air in the charge piping has been cooled by the intercooler, and is now cooler than the air of the engine bay and insulating will be a benefit.

 

I have 3 inch carbon fiber piping but was leary of using it because I noticed after working with this stuff that it only holds up to 250 degrees and then everything melts. Appication will have to be worked but it could work to replace a few pipes in your FMIC setup. Drop me a email at my website of anyone wants any 3inch 3d twill weave.

 

nevermind, you guys beat me too it.

 

This was a purely academic theory, and just one of many crazy idea that pop into my head each week, I just figured this one was rooted in reality enough, to see what others thoughts on the idea were.

nevarmore,

Yes, it is just like a thermos or those stay hot coffee mugs. and I'd love to see if it made a difference on the dyno, but I don't have resources to do so.


Evil Aviator,

That's interesting about turbine engines, I'll have to check that out sometime.

because metal is shiny and has bling appeal


rotarypower101,

Can't say I've ever come across anything referring to ceramic coating intercooler pipes before, exhaust yes, but not any of the other plumbing under the hood, I'll have to look into that. And yes thermal wrap would probably be just as effective, but 20 times uglier.


88IntegraLS,

Your the guy that looks at the $60,000 NASA pen and says why didn't they just use a pencil, while everyone else just wants one.


fastcarfreak,

While carbon fiber is a very cool material (as anyone who has ever looked at a Britten motorbike will agree), but I think it's often thought of as the magical fix-it-all material ,when it isn't, plastic pipes would probably have the same effect as carbon fiber.


CrackHeadMel,

You could make your own carbon fiber pipes with a little practice, you just use a pipe of the desired diameter as a template to mold the carbon fiber around.


couturemarc,

I release that there is a lot to be gain before the intercooler, but everyone has done that, I was just looking to see how you could preserve as much of what you've already gained as possible.

mwatson184,

I always thought that the compressed air charge after the turbo, while hot was still cooler than the engine bay, but I guess it depends on the amount of boost your running, more boost more heat.

Bukwild,

thanks for the comments, nice to known someone else realises that carbon fiber has it's limits.

andrew lohaus,

Thanks for reading my post anyway.

Everyone seams to agree that it would work, but the results just wouldn't justify the expense or the extra weight. I just wanted to look at the one part of the intake system that seems to be always overlooked. I seen air ram intakes, cold air boxes, ceramic spacers between turbo housings, thermal wrapped turbos and exhaust manifolds, huge intercoolers (some to huge), water injection, but nothing really for the intercooler return pipe.

 

The turbo-to-IC pipe can get very hot and will be hotter than the engine bay under boost. Temp at peak boost can easily top 300F. Perhaps using some kind of heat shedding coating would be marginally useful there.

For the IC-to-throttle pipes (and all the plumbing on to the engine), just get it ceramic coated. They have pretty colors now, and the finish is generally more durable than plished aluminum. I've got my intake manifolds and some of the piping ceramic coated with "chrome look" stuff.

But keep in mind that the thermo effects are likely to be small or insignificant, since there really isn't much transfer between a pipe or manifold runner and the air rushing quickly though it.

-Max

 

With the cost of a $60k pen, I could buy an FD and a doublewide on some land!

 

You would want the turbo-to-IC pipe to shed as much heat as possible, so performance would actually go down slightly if a heat barrier were used for this portion of the plumbing. Heat in the engine bay doesn't matter a hill of beans. It's the heat in the intake air charge that you want to keep cool.

 

So coat all after intercooler pipes. Don't coat pre-intercooler pipes.
I've thought about trying carbon fiber piping from the wet sleeves, not sure how it would hold up though.

 

This is especially true since the heat you would be keeping in the turbo-to-IC pipe is about 2 feet from where you are going to try to blow all the heat out of it and right into the engine bay (IC core).

-Max

 

Hmm, can you scrounge a thermos from the bowels of your storage closet or the local thrift store? Buy a few, hack the ends off, weld a plate on to make it a pipe and depressurize the inside again. No need to muck about with your own piping and it'll be enough to tell you if its appropriately insulated.

Hell a regular thermos and two thermometers should tell you if the concepts are still worthwhile under the hood. Unscrew the thermos and drop a thermometer in and seal it back up. Tape another one to the outside. Then zip-tie the whole load to your current IC piping (or a location in the engine where it will see similar heating) and go for a spin. Come back and read the thermometers. The difference between the two should tell you how effective such a setup really is. If there is a significant difference between the two then it might be worth it, if not go find some soup to put in the thermos and be happy.

 

Exactly. The turbo-to-IC pipe is best configured as a heat exchanger, just like the intercooler, because the engine bay is going to be cooler than the intake air charge after it is compressed by the turbo. Any heat shield on the turbo-to-IC pipe would just act to keep the heat in the system, which is counter-productive. It's the intercooler outlet air that would be best served with a thermal barrier if you are trying to keep that last 4-5 deg F out of the intake air charge.

 

You need some flow to make the test valid. A 1-foot long Thermos has 1/250th the amount of air that would be flowing through the IC pipe in one second at 250 fps. Maybe that tells us something useful -- that one Thermos-foot of air isn't going to pick up much heat at all in 1/250th of a second!

-Max

 

It's not a problem. Do the math, the air spends very little time in the pipes and there is very little surface area relative to the volume of air flowing through it. It simply doesn't have the time or the inclination to absorb heat before it is slammed right from the turbo to the intake manifold.

If heat was readily absorbed by the air flying through the pipes, we would just run a pipe to the front of the car.

But we don't, we buy these expensive things called intercoolers that slow down the air, divide it up into scads of little tubes to increase the surface/volume ratio, and then we put FINS in the cooling airflow path to FURTHER increase the surface/volume ratio (in this case the amount of surface area seeing airflow). Some intercooler designs put fins inside the tubes to go even FURTHER.