so i was smoking crack, right. when all of a sudden....

[tyrannix]

it came to me...

not really.

ive been thinking of this for awhile, just the pertculars of exactly how to do it just came to me

CAXYDETT

you have your normal setup in front, with a bigger turbo, ots of high end that takes a bit to spool up with an external wastegate (so theres more air gong thru the turbo, so more exhaust gas gets to the second turbo, than if the small turbo was first)

then a REAR mounted small turbo, even a standard 6psi t25 would be great. I Know there are already read-mount kits for some cars (RSX and Maxima come to mind without looking it up)

so, youd have your wuick spooling t25, no boost controller, just running on the stock actuator (so no vaccuum lines going under the car) ... then youd just need your oil send/return, coolant send/return.... but the rear kit for whatever car should come with those.

the rear turbo doesnt need an intercooler, as teh return pipe to the front acts as one, so that pipe would join the coldpipe right after the intercooler, snf then go wide piping .... up to your Q45 TB

is there anything i didnt think of why this thing shouldnt work?

CJ
Modified by tyrannix at 11:35 AM 8/20/2006

[ccasey645]

sounds cool! Im a bit confused though wouldnt the small rear mount turbo experience boost creep or over run the waste gate after it has spooled and the big turbo kicks in a high rpm's and throws a bunch of exhaust at the little t25? Maybe I'm not picturing it right but i think if the t25 had a external waste gate it would work and would solve having a very narrow powerband! Omg wow im gunna do some more research on this, ive got some crazy ideas now!

[c-rad]

is there anything i didnt think of why this thing shouldnt work?

CJ

Modified by tyrannix at 11:35 AM 8/20/2006

The cost/performance benefit isn't worth it. If there would even be a performance benefit.

[tyrannix]

weel say turbo A = big mounted normally

turbo B = small mounted rear

A = externally gated, weel say full spoolup around 4500, at .. weel just say 20 at the moment. at that point excess is gated atmospherically, so it can hold that 20 psi as it revs up higher

b= normal t25, internal gated.... it should reach full spool ~2500-3k at 6 psi, while it starts to gate that extra gas past 3k... and will only need to gate the difference between the flow it needs to be spooled to 6k, and what Turbo A needs to stay spooling 20 psi

Tx= turbine for XCx = compressor for xWZx, W = wastegate for XWZx, Z = R, replumbed after the turbo, Z= E externally, atmospherically gated

kindof upside down.... like youre looking at the engine from teh front, but then the exhaust goes down/front, instead of behind.

. ATMOSPHERICALLY VENTED Big A turbo. /. Bs.....................WEaIIIrrbrrIc.IspEc.E-0|TA-------\IIIrrbrrIc.IspEc.E///CA |IIIrrbrrIc.IspEc.E// | |IIIrrbrrIc.IspEc.E/ | | | |0¯¯¯¯0| | | | \ _ / | | | 0| / | | | | |0 | | | | | | | | \0/ | | | | | normal exhaust pipe from |\____ICICICICIC_/ | A big turbo to B small turbo | | | | |<ACTS LIKE AN ic | | | | | \__________CB | rear mounted small t25 Bt______/ BE \\\ ||| |---| |---| huge ricer can muffler with maxwell house tip |---| |---| |---| ||||

[ccasey645]

Trying to research it found this baby

[tyrannix]

well, the ascii art got pwned by the board software

but i think i stated the cost and benefit ... cost would be about what a normal rear mount turbo would cost

1. oil+coolant lines2. old t25 small quick spool turbo3. pipe to go from rear compressor to join fron IC piping after the IC

benefit is you can run a bigger turbo up front to take advantage of the higher top end output, and have the quick spoolup of the smaller turbo , which will help the bigger one spoolup faster

ill make a non ascii-art pic describing it in a bit

CJ

[ccasey645]

Sequential Twin-Turbo

Sequential Twin-Turbo refers to a set up in which the motor can utilize only one turbocharger for lower engine speeds, and both turbochargers at higher engine speeds. During low to mid engine speeds, when available spent exhaust energy is minimal, only one turbocharger (the primary turbocharger) is active. During this period, all of the engine's exhaust energy is directed to the primary turbocharger only, lowering the boost threshold, and increasing power output at low engine speeds. Towards the end of this cycle, the secondary turbocharger is partially activated (both compressor and turbine flow) in order to pre-spool the secondary turbocharger prior to its full utilization. Once a preset engine speed or boost pressure is attained, valves controlling compressor and turbine flow through the secondary turbocharger are opened completely. At this point the engine is functioning in a full twin-turbocharger form, providing maximum power output. Sequential twin-turbocharger systems provide a way to decrease turbo lag without compromising ultimate boost output and engine power. Examples of cars with a sequential twin-turbo setup include the 1993-2002 Toyota Supra Turbo (JZA8x), the 1992-2002 Mazda RX-7 Turbo (FD3S), and the 1986-1988 Porsche 959. With recent advancements in turbocharger design, sequential twin turbo systems have fallen out of favor because they are seen as unnecessarily costly and complex.

wikipedia is a great thing

[tyrannix]

yeah, thats great, but this is different.as teh big close turbo is spooling all the time, and so is the smaller rear one, the small one will just reach full boost first, and wastegate teh rest out, it will only be running on the main charge output from the first bigger turbo

CJ

[ccasey645]

yea I get it put the t25 behind the big turbo A on the exhaust but what stumps me is how the IC piping would work. Would it be best to have the y right at the throttle body? At the y would the intake air mesh well at different boost levels? Or would the big turbo try an push air up the little turbo's hot pipe at high boost? If im dumb and that doesnt make an issue I would be all up for tryin this out! Ive got a t3 in the mail

[ccasey645]

if you wanted to run really high boost compound turbo system could be used to multiply the boost pressure http://en.wikipedia.org/wiki/Twin-turboi guess thats what this is more of I might try it with running the hot pipe of the smaller turbo into the inlet of the bigger turbo. hopefully my motor can handle it! addCompound turbochargers are set up in various fashions. The most popular set up is to use one medium and one large turbo. The large turbo compressor blows into the smaller turbo compressor. The exhaust is set up to first enter the turbine of the smaller turbo, and then into the turbine of the larger turbo. Compound Turbo Charging has little "turbo lag" and can create high power levels. I guess the only limit to this is detonation from forcing massive boost though the small turbo and the heat generated from it. But most everyone runs intercoolers 3X bigger than necessary and ssautocrap sells 12X30X4in ones I would think would cool it enough. If anyone knows anything about this let me know before i attempt!! thats alot of customization to be limited to 10psi because of heat issues. Ive seen this sort of thing done many times on industrial and race diesel motors, i.e. semi's and tractor pulls, where massive boost is generated (upwards of 140psi!!). Of course diesel's thrive on heat so much different. Maybe I'll get a turbo with variable vane technology and save myself the hassle. Plus this would have to work on pump gas hence my skepticism. Dee help me out!!!IM almost positive it wouldnt work becasue of pre-ignition from the heat of the second turbo translating into the intake plus the octane level to make this work would be astronomical. It might work with two massive turbos but not with a small and med one.It just sucks caterpillar and cummins bolth do this all the time as well as many other diesel manufactors. My cousin went to wyotech for advanced diesel and works on semi's and industrial diesels all day and ive seen numerous setups like this its just diesels thrive on heat where as gas motors have fuel stability problems. After all this thought I'll just go with the t4.

Modified by ccasey645 at 2:40 PM 8/20/2006

Modified by ccasey645 at 8:19 PM 8/20/2006

Modified by ccasey645 at 8:36 PM 8/20/2006

Modified by ccasey645 at 9:36 PM 8/20/2006
Modified by ccasey645 at 8:53 AM 8/21/2006

[yourmomsrps13]

you might be better off with trying to get your hands on a Borg Warner VTG turbo. "The core features of the VTG system are the variable turbine blades guiding the flow of exhaust gas from the engine in exactly the direction required on to the turbine wheel of the exhaust gas turbocharger. The principle of variable turbine geometry thus combines the benefits of a small and large exhaust gas turbocharger all in one – a combination ensuring both very good response and high torque at low engine speeds as well as superior output and high performance at high speeds. And the supreme level of torque is now maintained consistently throughout a much wider speed range."

im sure in a few years we'll be able to find turbos like this that are affordable and adaptable for our motors

if your not big on the idea of a bunch of turbine blades moving because you think there is alot of moving parts to go wrong, then consider the cummins design where they use a sliding nozzle over the turbine, so there is only one moving part, sorta like the new turbo design that acura is going to be using, but their design is more of a diferent internal wastegate design.

[tyrannix]

i havnt done any research on the variable turbos, they sound cool. But the advantages to this system/idea, is that its almost an off the shelf cheap answer... using a small stock turbo, then a big non BB turbo as well (because it wont need to spool up on its own as fast)

cost of maintaining teh system, like if a turbo blows, will be much cheaper

but, like i said, its just an idea.. i may do it at some point. probably not (as i want to get the ca20 built before then, and i just found out i wont have my month of terminal leave to transition to the new job now :\ )

CJ

edit> BTW, buy my powerFC.. 1g and i toss in a z32 maf with some bonus stuff

[float_6969]

For a small displacement 4 cyl like ours, I seriously thing you would be SORELY dissapointed by the results. Building a VNT/VGT setup would be much easier I think. The best route IMHO would be to try and source a turbo form one of the new Jeep Liberty CRD 2.8L Deisels. It's a VNT/VGT turbo. I don't know much about the exact specs on it, but I know that that stupid little 2.8L and that turbo will make almost 300ft/lbs of torque by 2K rpm and makes it's peak HP of 160hp by 3500rpm. (I think it's capable of more HP as the curve wasn't tapering off, but I think the redline was the reason it stopped there.)