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is it possible to have a TT setup in which the first turbo is a small turbo and the 2nd turbo is a bigass turbo? i mean, the small turbo would keep the lag down on 1/4 mile runs and help the time; and the big turbo would have its uses on the freeway. am i correct or am i just totally confused, haha...anyhow, can it be done? thanks
Ahmed-->still Z-less
 
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You got at least $20k for just that turbo setup? Then if you do I'd guess it is possible. It would be one trick setup. I'd think you'd be replacing that 2nd turbo quite often though. You'd basically have to copy Toyota's original design with the TT's but modify it out the ying yang. That would be everybody's dream I think. If I ever get a job makin shitloads of money I'll try and make it happen. Then you will all bowdown to me in fear of my t66, and when the t78 kicked in you will all PISS YOUR PANTIES!!!! Oh sorry guys just went off the deep end a little there. But that would be really bad ass to have that setup. But you're talkin custom everything. I couuldn't imagine tuning that thing.
 
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A way chepaer alternitive would be to use the stock turbo setup in sequential mode and replace the stock turbos with a CT20 and a CT26. I dont if anybody has done it or if i can be done tough.
 
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Josh S said:
you can't have a "small" turbo and a "big" turbo online at the same time because the pressure frol the larger turbo will try to force it's way back through the small turbo's compressor and will slow it down or even make it spin backwards :eek: which will likely twist the shaft.
I'm no authority on this (this would be something for those fluid dynamics physicists), but I don't think this will occur, if the pipes are configured properly. I'd think the BOV would go before the pressure would be great enough to flow around the Y bend into the smaller turbo (assuming you use a Y pipe to collect both inputs to a single input on the intercooler). With both turbos going, the flow from the smaller turbo will be less than the larger turbo, but they're still flowing in the same direction, which means the larger turbo would have to overcome the pressure from the smaller turbo. This wouldn't happen if they're pointing in the same direction. If anything, the larger turbo will create a vacuum for the smaller turbo, causing it to spin faster. If you connect them to the intercooler separately instead of using a Y pipe, it might get rid of the backpressure issue completely.
 
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Discussion Starter #6
me and a friend were talking abou this, when the second turbo spooled wouldent it spool the shit outa the first one?
 

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Possible, but hard.

Let's use some common sense here...

The engineering involved would rival that of Toyota's (pretty complicated stuff).

You'd still need an IACV, EGBV (or their equivalents) and several VSVs to control them connected to a stand-alone ECU with additional outputs.

I have no idea whether or not the #2 will cause the #1 to spin backwards, but common sense dictates that there would be a loss in efficiency for both, since the #1 is being retarded (due to drop in the pressure difference between the charge air and exhaust side) and the #2 is working against #1, but either way you'd have to gradually bring #2 up instead of slam-starting it, again just like the stock sequential system.

Maao, the "direction" of the air doesn't matter... as you learned in high school chemistry, pressure equalizes throughput a closed system and does not flow like a fluid does downhill. The air doesn't know where to go; it goes everywhere. In a car, it just so happens that the pressure differential between the turbos and the engine (engine creates vacuum by consuming air and burning it) causes the air to be sucked into the manifold and into the cylinders.

There's always going to be static pressure in the manifold (positive boost), so you'd probably have to shut down the #1 turbo once the #2 comes on (as opposed to the sequential, then parallel, operation of the stock twins). Basically you'd replace #2 with a turbo that has greater output than the stock twins combined and you'd come out on top.

Bottom line; the two turbochargers would have to be segrated using a system very similar to the stock sequential to avoid complications due to boost difference. You'd probably need 2 separate wastegates as well, connected to the system that controls boost management. But once #2 comes on, #1's wastegate will have to be closed to use all the exhaust pressure possible to power #2, and the manifold going to the #1 will have to be blocked off to prevent unwanted complications. You'd probably still have a pressure drop in the transition period.

Yeah, probably $20,000-30,000 to engineer, not to mention the test equipment. That's why companies put R&D into complicated turbo systems and not individuals. :(
 

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Now what would be interesting would be the stock sequential system with two small aftermarket turbos. Like the sp57 or sp60?. Then you would have about the same level of lag as stock but on the high end you would have much more power.
 
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Discussion Starter #9
I've already designed a sequential that uses almost all the stock components including gaskets, and more importantly looks completely stock. I won't say what turbos I'm using specifically (not Toyota) but it took alot of machine work and time to think it all out. About 2years actually. It will take alittle bit of tuning to be seamless, but I will develop some signal conditioning circuits to modify the factory signals to the vsvs to allow me the control the actuation rates. My exhaust manifold is under contruction at the moment and should be done shortly. The output of the two turbos should surpass a T66 single but I am not overly concerned with rediculous HP#s and don't expect it. Besides I have an automatic so they never dyno very high. I did recently pull 380 HP at 1.2 bar on the dyno through a factory airbox, and intercooler. My car is completely stock looking so will my turbos. Mani and Keith Ta know my car. :)
 
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I raced your car that night we all met up in irvine...I had the stock white 97 TT 6speed. I got smoked even after you lit up the tires for a few seconds on the launch. Sounds like you have an interesting setup in the works as well...I would love to hear more about it. We should set up another meet sometime early next month if anyone is interested.


Mike
 

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you can't have a "small" turbo and a "big" turbo online at the same time because the pressure frol the larger turbo will try to force it's way back through the small turbo's compressor and will slow it down or even make it spin backwards which will likely twist the shaft.
This won't happen for the same reason your turbo doesn't spin backwards when restricted by the intake. Boost is a measure of restriction not flow, so when the system as a whole reaches a certain set pressure the excess is vented to the atmosphere. Two turbos the same size, or different sizes both work to pressurize the same "system" with your engine as the path of least resistance while the TB blades are open. Even If you had the turbos facing each other in a T with one end going to the engine, it still wouldn't happen as long as you have a BOV.

So, yes it's possible and it has been done many times on cars, not sure about the Supra though. It would be similar to any twin type setup for your car.
 

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What happened to RPS aftermarket sequential turbo system? I remember them hyping it up before TX2K1 and then we heard nothing else about it. I guess its just vaporware:rolleyes:.

-Amir
 

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Although both argue good points...

you have to undestand the messurement of CFM. The larger turbo moves CFM then that compaired to the smaller one at the. This occurs.... BEFORE the turbos have a chance to vent through the BOV. This is not only a problem of PSI going from the turbo to the engine....but the CFM leaving the engine and exiting through the turbos as well. The amount of CFM the larger turbo puts out, will have to be forced through the smaller turbo.....and will overspin the shaft. Kiss .....your smaller less effecent turbo g'night.

The bov plays no role in this problem. As you most likly will NOT reach PSI leaves high enough to vent.........but you will reach a level of pressure that is too great for the smaller turbo to handle.
 

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Whats up guys?! I work on planes and play with pneumatics pretty and hydrolics often so I guess I feel pretty comfortable on the subject(though i did not write the book on it). Alot of the valves on a plane work on differential pressures and not CFM, which cause them to open and close, hence this is what I conclude: If you install a bigger blow dryer in the number two position, it will not backflow into the number one and this is why. Volume does not come into affect here only psi. 14psi is 14psi regardless if you have X number of cfm or Y number of CFM. If you have the turbos set at a normal boost then you should be happy camper. NOW say you run with the waste gate in the full close position, both turbos will peak at there highest range. The smaller one will actually peak out but then after it peakes out it will then be forced to reverse flow, the reason being that the turbo will be able to max out at a higher PSI than the Smaller one, hence twisting that shaft like a bat out of hell (always wanted to say that 80) ). Also, the BOV has nothing to do with maintaining pressure, its only purpose is to act as a relief valve when it feels a differential pressure between both sides of the throttle valve. when the throttle closes, you have less pressure in the manifold which is now felt on the nipple of the bov, the pressure inside the plumping is higher that the pressure in the nipple so it causes the valve to open hence giving you that lukeskywalker lightsaber sound, boo yaa!

Have a blessed one guys.
 
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Discussion Starter #15
forcefeed said:
What happened to RPS aftermarket sequential turbo system? I remember them hyping it up before TX2K1 and then we heard nothing else about it. I guess its just vaporware:rolleyes:.

-Amir

The aftermarket sequential set up is still in the works. RPS automotive has closed. Rob is concentrating on making killer clutches, My brother and my self are opening a new shop called TWINS TURBO. as we are twins. we will be continuing to attempt to perfect the set up . we had a running test car but the engine was built by a less than quallified person, and it was hurt in testing. so we are building a new real race motor so we can conitnuing to play with the setup. we have lots of other interesting things in store for 2002 and will try to keep every one posted.
 

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Supraholic NYC said:
The aftermarket sequential set up is still in the works. RPS automotive has closed. Rob is concentrating on making killer clutches, My brother and my self are opening a new shop called TWINS TURBO. as we are twins. we will be continuing to attempt to perfect the set up . we had a running test car but the engine was built by a less than quallified person, and it was hurt in testing. so we are building a new real race motor so we can conitnuing to play with the setup. we have lots of other interesting things in store for 2002 and will try to keep every one posted.
Sounds very interesting. One thing to keep in mind, it would be good if your set up looked nicer then stock. (eg. the turbos are on top in view instead of hidden under a maze of pipes) So many people look at my stock motor and say "Where are the turbos?"
 

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With the AEm out now controlling this would be cake. Now we just need some reasonably priced hardware to bolt on (sigh). The upgraded sotck turbo thread is also interesting but as big a PITA as it is pulling the stock ones I don't know how interested I'd be since if they failed I'd have to shoot someone ;)
 
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