..and ordering an uppipe so I can just do one big UP/DP install. Leaning towards the PDE. I know John (married04wrx) has one and likes it. Anybody else have opinions on the PDE or other pieces? I'm willing to fork out the $ necessary to get the best, most troublefree piece out there. The only other uppipe I've heard nothing but good things about is the TurboXS one.
I probably will. Looks like my schedule might be slowing down a bit finally, so will have some time to finish up my garage and do some fun stuff. :bigthumb:
I have a question about exhausts and I've talked to Alex a bit on this. I'm looking into B&B TBE, twin tip. I'm a fan of how they sound on Porsches and BMW, but I wonder if any of you know of any WRX's with these installed so I can hear that too? Best of all it has a high flow cat for my CA emissions =) Thoughts?
I'm trying to convince Alex (WRX-WRC) to just get an up pipe and not go with a gutted one, but I'm having no luck...
"I'm trying to convince Alex (WRX-WRC) to just get an up pipe and not go with a gutted one, but I'm having no luck..." I hear ya, i think im just gonna wait, if i can sell the jag then i will ahve no problems with buying one.
TXS The Turbo XS upipe is cast iron and retains heat better than the others mentioned. Better Heat retention = Better Spool up. The inner diameter is also the same as the stock pipe is so airflow is much smoother. Good luck Matt
Another satisfied Crucail Racing UP/DP owner! Since it was ceramic coated, i din't install heat shield to save some time. I feel like ceramic coating is doing better job of keep heat than stock heatshield.
Re: TXS I really want to see some tests of how much better each UP retains heat. I imagine the ceramic coated ones are better than cast iron.
Re: Re: TXS I would think just the reverse. Cast Iron having more mass should retain much more heat than is even possible with a coating. Thats why all these aftermarket headers spool up slower than stock, even if they do have the ceramic coating, they still dont have the heat retention that the cast iron does. Matt
is there even any data about the temperature or pressure gradient from the cylinder head/exhaust valve to the turbo to prove anything either way? I understand that cast iron is incredibly dense but ceramics are used more widely in industry due to higher heat capacity and lighter weight.
I don't know whether or not it's better to have a hot pipe or not for turbo spooling, but I do know a fair amount about heat transfer and thermo. So what I'd like to do is offer some facts, suggest how it will affect both the pipe and the temperature of the air within the pipe and the air itself. From that hopefully you all, knowing whether or not you want a hot pipe/air you can make a determination: Since the question has risen between cast iron and ceramic coated steel, I'll discuss those two materials in a basic context. First of all, the average energy <e> in a gas is proportional to the velocity of the gas squared, v^2. It is also proportional to the temperature of the gas, T. Basically: <e> = 0.5*m*v^2 = kT where m is the mass of the gas and k is a constant. The first part states that you will have a more energetic gas where the velocity is higher, and velocity is inversely proportional to the restriction. Less restrictive pipe allows for a higher velocity, more energetic molecules. The amount of heat will be proportional to the energy of the molecules. However, by this argument the velocity increase will be accompanied by a temperature rise and vice versa. Since the temperature is dictated by the engine combustion, we can ignore this argument and assume that the temperature difference from restriciton and velocity is negligible. So, the temperature of the gas inside of the pipe is the same in both. Because we have a moving gas inside of a stationary pipe, most of the heat will be transferred by convection to the pipe and the dissipated by conduction within the pipe. Thus, the heat capacity is important. A metal surface has a higher heat capacity and higher thermal conduction than a ceramic. In basic terms, this means that the metal will get hotter all the way through than the metal coated in a ceramic. The main difference between the two is that the ceramic coating disspate heat to the metal beneath it and away from the surrounding parts. In other words, the interior of both pipes will be exactly the same temperature while the exteriors will change. A ceramic pipe will provide a lower exterior temperature outside of the pipe and in the surrounding engine bay. The most obvious reason for this is the elimination o a heat shield around the pipe within the engine. As to the argument with spooling, I don't know why it would make a difference. If you're looking at the interior of the pipe, there shouldn't be any noticable difference. The only benefit I see from heat transfer applications is the exterior temperature. Perhaps you can explain the theory behind the turbo spooling and someone else, or maybe I, can offer some more information on how the different pipes should affect the temperatures, buw from what I've seen posted, the temperature argument vs. turbo spool seems irrelavent for the above reasons. i would expect a much greater affect from the surrounding engine. If anything, I think the cast iron would hurt performance because the engine bay heat it created which would cause the air in the next pipe going into the cylinders to heat up. The ceramic coated pipe would help maintain a lower temperature in the other pipe, helping provide more air int he cylinder for combustion? Thoughts?
You guys kill me, lol. Heat does indeed make turbos spool faster. The more heat you can keep in the exhaust pre turbo the better. You can use all the formulas you want but it doesnt change the fact that heat makes the motor go round. You guys should pick up a little book by Corky Bell, its about turbos. I have no idea if any of your formulas are correct, what I do know is that if you heat up a 1\4 inch thick thick stainless pan, and you heat up a 3\8 inch thick cast iron pan, the cast iron pan will be hot far longer than the stainless pan. Thats what we are talking about is heat retention.
Wow...a little over my head with that post...good stuff though. My opinion(probably a little brainwashed by Porter) is to stay with the flex. Ok..say the Cast piece does give a couple HP...is that enough reason to risk having that solid piece leak on you and having to go through what I consider to be a PITA to get to it to fix it? To me, putting the Flex pipe on and knowing with a high degree of certainty that I'll never have to F with it again negates any small gain using the cast pipe... my .02 Now lets take these uppipes to Commerce and race them allready dammit!!!
Guys correct me if I'm wrong, but the turbo benefits from the heat because the hotter the gas the more volume it takes up. The more volume it takes up for a restricted space (header/up-pipe) the more velocity it has. Think of it as a river going through a narrow section, the water flows faster right? So the hotter the gases, the faster the flow. The faster the flow the quicker the spool. However if you tighten the diameter of the pipe, i.e. a tapered velocity stack or smaller than stock diameter up-pipe you can increase the flow without increasing the heat. Remember the hotter the exhaust side of the turbo the hotter the intake side. As we all know the cooler the intake charge, the more dense the air. All of this equates to more power.
If you're looking for a hotter gas temperature and keeping the heat inside of the pipe, then cast iron seems like a self defeating argument. Yes, it has better heat retention than ceramic/steel. But it also conducts that heat away from pipe *through* the cast iron, out into your engine bay. A cast iron pan vs a steel pan seems like an irrelavent argument because both are open to the air on all sides to cool. In an engine, the flowing gas is going to be determined by your engine temperature, then that heat is either going to be retained in the exhaust or dissipated through the exhaust walls. From what is said here, people seem to agree that you want retention in the up pipe? Ceramic/steel will retain that heat better inside the pipe by preventing it from being transferred into the engine bay. I also don't see why retention in the pipe is an issue unless you are constantly turning your engine on and off. Maybe you can explain the reasoning behind retention and why you want that in the pipe more than the air? Your engine will do the retention in the air for you from combustion because it provides a continuous gas temperature (at constant RPM), but a ceramic (low thermal conduction) basically acts as insulation to hold the heat inside the pipe rather than in the pipe itself. It's more efficient. That's why you have ceramic furnaces and not cast iron ones. If you retain heat in your pipe, then it's heat sapped away from your gas. The reason that cast iron is preferred in cooking is precisely because it transfers heat through. You don't want the bottom of the pan to be hot, just the top. That seems like the exact opposite of the case here. As to the flow argument and smaller pipes... The argument about a smaller diameter seems to be a good one, but what is the limit on that smaller size? Obviously we can't all drive around with 3" pipes tapered to 0.25" for the faster airflow because at some point doesn't the back pressure created actually hinder the flow? Fluid flows aren't my specialty, but there's two basic types: llaminar (smooth flow) and turbulent (think eddies in a river or rapids). When you are trying to retain heat then you want llaminar flow, which is partially determined by the velocity and by the surface roughness of the pipe. A smaller diameter pipe increases the velocity but at some point, the air starts swirling back on itself when it tapers and slows down the flow. Also, as this swirling begins the heat in the air is dissipated into the walls of the pipe (if the pipe hes a cooler temperature), which would decrease the temperature at the inlet. Cast iron also has a much rougher surface than a ceramic, which I think would contribute to the swirling of the air. Just another $0.02 in canadian pennies
Actually, if memory serves you WANT a slightly rough surface to increase flow. My fluid dynamics knowledge is a bit rusty, but I think it had to do with a layer of turbulence being created that reduces friction overall...
Like I said, flow isn't my specialty.... Is it analagous to the dimpled golf-ball but on the surface of the pipe? Having a small turbulent layer creates a cushion between the laminar flow and the wall? That makes a lot of sense to me. But that still brings into play the heat convection between the gas and the pipe surface. Having that turbulence will deliver more heat into the pipe (assuming the air is hotter than the pipe), making the inlet temp cooler. I could run all of the formulas to see how it should play out, but I still have a feeling that the temperature drop for cast vs. ceramic coated is negligible. It seems like an efficiency matter, and to retain interior heat ceramic coatings are by far much more efficient than cast iron. The heat retention of iron is good, but you have to use the heat from the gas to obtain (and maintain) that temperature. A ceramic will reach its steady state much sooner and not require as much heat-sapping to maintain the interior temperature.
Yes, the example I recall was how a slightly rough hull on a boat would decrease friction as the micro-turbulence generated by the roughness would create a layer that the rest of the water interacted with.. so the friction was basically water against water, rather than water against boat hull. As for the heat retention... the heat has to come from somewhere, so in order to 'charge' the cast iron it has to sap heat from the exhaust. I suppose that it could 'even out' the exhaust temps (heating up the flow when it's cooler), but it'll also radiate heat outwards. I don't doubt a ceramic coated pipe would have more 'area under the curve' as far as heat going to the turbo. But honestly, I doubt we're talking more than 1-2hp if even that.
You guys are talking about the boundary layer of the flow. We didnt really get into frictional forces in my Low Speed Aerodynamics course this semester but the airflow will be slower along the walls of the pipe due to friction, as far as I know a smooth pipe should flow better than a rough pipe. Basically what happens is that the friction against the walls slows down the air that is touching the walls and then that slower air is what interacts with the rest of the flow instead of the metal pipe. About the pipe diameters, it is my understanding that they all keep the same diameter as the turbo inlet to reduce turbulence. If the exhaust pipe is too large for the flow going through it the airflow will separate and no longer be smooth and laminar. I was talking kinda out of my ass with the thermo stuff, I havent actually taken Thermo yet but Intro to MSE which discusses the properties of different materials. As far as heat retention stuff header wrap is cheap and works great in conjunction with any type of UP.
I talked over the thermal stuff with another MSE grad that I work with who specializes in thermal properties. He agrees that a ceramic coating on the pipe is better for keeping the exhaust temperature as high as possible for the above reasons. There's a lot more theory behind this, but not necessary to understand. If you want the "best' retention, you can always get a graphite coating on a steel pipe. It heats up fast like cast iron, but insulates better than a ceramic, so the metal stays cooler. It's only $200/sq.in. We also addressed the "evening out" of temperature. Basic thermal properties says that the pipe temperature will never be hotter than the exhaust temp as long as the engine is running. We don't really care what the temp of the air is when the car isn't running... ;-) Bobby, can we just assume that air is Newtonian, basically eliminating turbulence on the walls as a factor? There are very few interactions between air and other surfaces.
The easy way Lets just do this the easy way, we can all meet at the track and the one with the fastest car wins
Well gentlemen, let it be known, that I do enjoy skittles, and sometimes m&m's. End the thread hijacking now, or I will lock Moose's thread. If you feel the need to continue this, please start a dedicated thread. Cheers :bigthumb:
i recommend the crucial UP, i have it as well asthe DP. Install sucks, but i'm happy now. the coating is pretty cool. i can touch the dp after running bthe car for a long time and it's hot but i can touch it.:bigthumb:
Yeah, I have considered those too. Leaning towards PDE flex right now, but not decided yet! It seems like the real issue with any pipe is installation, even more so with non-flex pipes. I wonder if the problems people are having could be related to tightening things down in the wrong order. The only component I see that you can move around a bit would be the turbo... so would it make the most sense to torque down the exhaust manifold and UP-to-manifold first, then torque down the UP-to-turbo and finally the turbo brackets. Looking at the rest of the exhaust, seems like it has enough give to move around...
I don't think it is a matter of order in which you tighten, just maybe tightening enough or too much. Not sure though, I am probably not the best person to answer. Call Porter and ask him, or Scott Siegel, they would both know.
my problems with installation has nothing to do with the actual piece... just the labor... every bolt sucked and didn't want to come undone. you can ask kris, it wsas the installation from hell.
You have to spray "PB Blaster" on the bolts to loosen them. When I say PB Blaster I mean PB not wd40 or anything else, nothing works as well as that stuff. MATT
Slow, we had enough PB blaster on that car that it was smoking when he had it all back together and running...
You can never have enough PB on hand for any install. It makes life much much easier, and it's pretty inexpensive
The Blaster I sprayed my car down with it the night before and let it sit all night. The next morning about 10 minutes before I started I sprayed it again. Everything came off really easy. Matt
End threadjacking? I guess I'll have to head over to another thread then. I still want to witness the hell that is a WRX UP install, my car came with the Vishnu UP on it already.
i have no idea which is better. But i do want to say that i think that you all are genius' and whenever i do an install on my car, i will let you all argue about what is going in on a scientific standpoint. who knew that you could get a science lesson on wrx atl. seriously, i think i learned more there than i did with 4 years of science class at college.
I got the turboXS flex uppipe too and from what i could tell it was stainless steel, not cast. Anyway i like the pipe and recommend it. I heat wrapped mine and it has and EGT bung in it too (though i decided not to reinstall it)
Yeah, seems like there are two versions of it.. one solid cast iron one and a stainless steel one with flex joint. I got quoted a good price on the PDE Flex, so might go ahead and order it this week.
i have a question... then why the big deal with CAI and larger intercoolers, and why the name cooler, and intercooloer sprayers?? are those not created to provide the engine / turbo with cooler air?? now i know that CAI are pointless b/c by they time the air actually gets to the turbo it is as hot as it would be w/o it, or so im told, but why do people constantly talk about power gains and such with these parts if the engine/turbo is indeed that relient on heat?
Correct me if I'm wrong, but the intercooler air and the up-pipe go to different parts of the turbo. The exhaust gas drives one side of the turbine, spinning the forced induction side that takes cold air from the intercooler which enters the cylinders. This is burned and the hot exhaust gas drives more air into the cylinders. But you want hot air (exhaust) driving the blades and cold air entering the cylinders (intercooler). The colder the air is, the more air you can squeeze in (think back to chemistry and the ideal gas law Volume is proportional to Temperature). When you squeeze in more air, you get more burn and better burn, providing more power.
SkullWRX is right. There's a difference between the air driving the turbo (exhaust) and the air going into the motor. Both pass through the turbo, but one goes through the turbine and one through the compressor. Of course, the hotter you get the exhaust going into the turbo, the hotter the turbo gets and it'll result in some heat transfer to the air going through the compressor no doubt... can't really win that one.