There is not really any real significant advantage to a twin or single turbo set-up in that of itself. Theoretically, if you used either on the same motor, as long as the efficiencies at the airflow rates(split in a TT set-up) are the same, the results would be the same. Of course in a V-motor, there are some advantages to being able to bring more exhaust energy to the turbos. For a given application twin turbos split the overall exhaust energy the bearings see as well so there may be some slight longevity advantages as well. But all things equal, they are for the most part, equal.

As far as the intake piping, how much heat do you really thing will be radiated into the intake stream. The section of pipe that would see a higher temp will be short. Under boost the air will be moving through the pipes quite quickly. And with such a low surface area to volume ratio, a pipe is not exactly the ideal device for heat transfer. It takes an intercooler to pull some 70-80% of heat out of the charge air. And an intercooler is designed as a heat exchanger. It slows down the air and spreads it out over a much higher surface area to volume ratio. The piping will not be a significant issue.

 

With regard to the intake pipe running over-top the turbo, just wrap a little insulation around both of them, and then no more heating issues, right?

'03 G35s 5AT, Garnet Fire/Willow
Staggered 18" SSR GT1/Bridgestone PP S03
Eibach Springs/Sways, Stillen 2-pc BBK
Stillen Intake & SS Cat-Back Dual Exhaust

 

CARB, well JWT and most likely APS "will" get CARB approval this year and next repectively. Even if Turbonetics did intend to file , this plumbing configuration woud make it nearly impossible to pass. When we see this Kits "Best and Final TQ curve" , then we will really see the difference.

For a strret/strip setup , a "power way up top" TQ curve is less than desirable when compared to a flat mid band curve , IMO.

 

there are trade-offs between a single and twin turbo setup. if you are into top end power, twin turboes will be a disadvantage because you have two smaller turboes that cannot move the same amount of air as one huge one. if you split the efficiencies between 2 turboes you get half the output per turbo, therefore you would have to use a turbo half the size of a big one to get the same output right? wrong. there are limitations on how many cfu's a turbo can push out and the harder you push it, more likely it will fail. thats why all of the 1100 hp, 200 mph monsters run single turboes. if what you desire is a fast spool up and lightening response, then a twin turbo will be right up your alley, i guess its really a matter of what floats your boat.
in regards to the intake piping, i think the intake piping will be an issue. as hot as that turbo gets, try to swipe your hand over the turbo when its at full boost and tell me your skin won't fall off. that thing will get red hott, and being enclosed in an engine bay right underneath the charge pipe will have effect on intake temps. and the pipe, being metal, will transmit that heat along the length of the pipe all the way to the intercooler outlet. so in a sense there is not heat just where the turbo sits, but rather along the intake piping. as for an intercooler, its 70-80% cooling efficiency is due largely in part because it sits in a well ventilated area with free flowing cool air running thru it. if you jam an intercooler into an engine bay with no venting, it becomes useless.
in regards to the turbo being better sitting next to the exhaust ports, that is not necessarily true. if the exhaust gases do not have enough travel time to become more laminar in flow, you get uneven pulses hitting the exhaust propeller, which is inefficient as compared to exhaust pulses hitting in a smooth pattern, ergo better spool up. think of it as a random "1-4-2-5-6-3..." pattern. to run more efficient you want more of a "1-2-3-4-5-6" pattern as your cylinders are pumping out exaust gases. that is the theory behind equal length headers. you give each exhaust pulse enough travel time so that you get a consistent pulse to the turbine. since the exhaust pulses will not overlap each other or become unsynchronized you get better spool up. this theory is derived from F1 race cars from back in the day. they ran exhaust manifolds that placed the turbo far away from the exhaust ports for quicker spool up and better top end performance. all of the top drag racers, look in their engine bay, none of them run manifolds that place the turbo right near the exhaust ports. if that was the case, then they'd all be running manifolds similar to the GReddy ones. they run the equal length headers for better boost response. this is not limited to drag racers, as i have mentioned the theory was derived from older F1 race cars.

04 DG/G/6MT/Premium/Nav/Clear Bra
Bone Stock...to be continued...
"You kill mah brodah, now I kill you!" - some old kung-fu flick

 

I highly doubt Turbonetics will or was even considering CARB legality. My understanding is that this kit removes the cats entirely. A big no no as far as getting an EO number is concerned.

 

2 small turbos that each move 15 CFM of air at 75% efficiency will be moving the equivelent of a large turbo moving 30 CFM of air at 75% efficiency.

Umm? Most, if not all of the 1000+HP Supras use 2 large turbos. when a lot of airflow is involved, you will end up needing a rather large turbo. Considering space requirements, it might be better to fit to smaller turbos in place of a large one. So long as efficiency at the given boost and total airflow is the same, output would theoretically be the same. And this type of twin turbo configuration isn't going to be spooling much faster if at all. Keep in mind each turbo is recieveing effectively half the exhaust energy.

As far as heat, tell you what, remove the Front mount intercooler on a car and run a regular pipe across the front of the car in it's place. I guarantee the air temp of the charge air will drop to any noticible degree. And intercooler works for several reasons. Yes it does have to be cooler than the air going through it. Heat isn't going to transfer from one object to the other if they are the same temprature. This is what happens when an intercooler heatsoaks. With the internal volume of the intercooler, it causes the charge air to have to slow down. Particularly when there are more channels. This increases the charge air's dwell time in the intercooler. Lastly, the surface area is vastly increased. With turbulators both inside and outside, there is a lot of metal making contact with the air, both inside and outside the I/C. A pipe has a boundary layer of air right next to the pipe. This is the only air that will really see an increase in heat. And couple that with the high air velocity, the time the air is allowed to even get heated is minimal.

Turbine temps will of course soar under boost. Compressor housing temps will probably be about 200 or so degrees as well. But with air moving thorugh so quickly, it won't have nearly the exposure to hot air as you might think. Certainly ideally keeping everything cool will help in the search for every last bit of HP. But when does it become unreasonable. When you are talking about a difference of maybe 1-5 HP, it just isn't worth nitpicking.

As far as exhaust pulses, unless you want a very odd non-equal length manifold, you will never get a 123456 pulse order. Not unless the motor was designed with that firing order. And an equal length mani is not going to fix that. Equal length manis have two advantages. They offer evenly distributed pulses. I think this is what you are referring to. But it has nothing to do with the order of the pulses. When you are talking about a 4-1 or perhaps a 6-1 merge colllector that is properly designed, and the tubes are equal length, then at a given RPM, each pulse will reach the turbo in the same amount of time. which means then that the exhaust pulse spacing will be equivalent to and in the same order as the firing of each cylinder. And secondly, they offer pulse tuning where the pressure wave is sent down the tube and up another tube creating a negative pressure wave behind the valve. At certain RPM's it will create a slight vacuum and actually help pull air out of the cylinder as the exhaust valve opens. It is limited to a small range of RPM's though as the length of the pipes will dictate the timing of the negative pressure wave in relation to the valve opening. Longer tubes generally cause this event to occur at higher RPM's, which is why race cars use them. They tend to be driven at higher RPM's.

Drag racers use equal length manifolds as they flow better and offer the above advantages.While quick spool is certainly desirable, there are several ways they can achieve that without worrying as much about turbo size and manifold design. They spend much less time waiting for the boost threshold to be reached than actually boosting. And considering drag slick allow a much higher and harder launch then street tires would, they can get beyond the boost threshold relatively quickly. And most 4-cyl drag racers do use equal length manis for flow and use split entry turbines to group exhaust pulses to get stronger but less frequent exhaust pulses at lower RPM's to aid spool. And if you don't believe these things I say, feel free to take up the argument with Corky Bell.

 

all very good points, but waaaaaayy too much reading, lol. oh yea, as for the "1-2-3-4-5-6" order, i didn't mean that the cylinders were firing in that order, i just used that sequence to show a synchronized order as opposed to an off beat random one. i also agree with you on the 2 huge turbo subject. key word was "huge" though, and i was referring to a smaller turbo setup, i should have made that clear.

04 DG/G/6MT/Premium/Nav/Clear Bra
Bone Stock...to be continued...
"You kill mah brodah, now I kill you!" - some old kung-fu flick