Spoolin8

iTrader: (2)

After doing some research around the forums i found that STS way back, bailed on creating a STS kit for the 8 and one other member created a kit were the turbo sat where the stock cat was. However, it appears he has since blown two engines. I was thinking about creating a rear setup in which the the turbo would sit in the location were the stock exhaust would be. There is plenty of room to get a turbo and WG in there. Im no newb to turbo's so please dont come in here saying it will lag and be inefficient because the fact is a properly STS style kit can spool just as fast.

What im looking for is any more information i may of missed as far was what the best engine management would be for this? One other thing i was looking for is on the greddy turbo kit where does the oil return line run/tap into? I need to figure out if im going to need a small electric oil pump to flow the returning oil back into the sump...

Thanks in Advance

maxxdamigz

iTrader: (1)

The Greddy kit (and most kits) gravity drain to the oil pan. You will need to set up an pump driven oil return system or some other arrangement. I'm pretty sure they make rear turbo kits for corvettes so my input on the matter would be to get the core of that design and just fab up similar components. The turbo doesn't really know or care what engine it's attached to. I should think a key aspect of this arrangement is how you are going to arrange the turbo and wg to maintain ground clearance. And after that, how you route the pipes so that the hot exhaust pipes don't heat your charge. The guy before you who built this put a ton of documentation up. Given the number of more standard kits available, I'm not sure if the rear mounted kit is really necessary, but if that's where you want to put it, go nuts.

Brettus

iTrader: (2)

correct

Spoolin8

iTrader: (2)

lol but really it would not lagg. The pressure in the exhaust is constant in a free flowing exhaust and that does not change depending on how far away the turbo is. Its not about the the distance the air needs to travel but rather the time it takes to pressurize the volume. using smaller diameter piping to allow the onset to be the same if not better than a manifold kit.... The Esmeril and Greddy kits would spool at the exact sime time if they had the same turbo's and piping volume.... does not matter the distance.

So in my case i can only take the pipes so small so yes i will have a little lag on the bottom end because i dont want to restrict the exhaust but i can use a 1" pipe for the charged air which would most likely have less volume then the greddy or esmeril kit and could offset the lagg from the exhaust.

Brettus

iTrader: (2)

IDK man - heat loss is very important also because heat translates to energy used to turn the turbine . And small dia. tubes will restrict flow .
We know the concept works because Rotorocks did it . He said it was not laggy , but did he have anything to compare it with ?

syntheticdarkness

iTrader: (7)

I've looked into doing this also, and call sts, and they have a really good shop here in PA that they would install all SS pipes etc.., and match a specific turbo size that would work best, then they would have me go to an rx7 shop and have them tune it.

I'd do it myself, but I likes warranty. I've also decided to probably go with esmeril or greddy instead, but I can't make up my mind. Since the procharger is way more then I wanna pay. If you have any questions call them up and ask, that's what I did.

Mawnee

Good luck with the project. I know when people started talking about rear mounts on C5s back in the day the naysayers ran out the Lulz flags. But then the numbers and time slips started coming in and they got quiet quick. As long as its done right a rear mount can make GREAT power!
When i started contemplating my turbo build I gave a rear mount setup some serious consideration.

Spoolin8

iTrader: (2)

Honestly if you know how to weld you can make yourself a fairly cheap turbo kit by going the STS method. Im not doing it this way for the price aspect i would just like something different.

Im thinking if i get the maf mounted back there with the 3" inlet i can use a accesport to tune it which would really be the biggest issue. the return oil pump is really not a big deal im just curious as to where the greddy kit pulls its oil from and returns it.

kersh4w

iTrader: (3)

i believe STS sells a universal kit for ~$1700.

some guy on the forums bought and installed it.

Mawnee

The intake part was exactly where I got annoyed with the rearmount idea. I couldnt come up with a mounting location that I was happy with. My main concern was with the rain we get here in florida. Funny enough, my current filter is highly exposed to the elements where it is currently located in my bumper lol

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Chris

iTrader: (10)

this has already been done before... search a bit

Spoolin8

iTrader: (2)

For the MAF i was going to just rewire it to also be covered in the rear exhaust shielding. Clearance really is not a issue because i have never bottom'd out my exhaust and this is going to sit higher then that anyways.

Spoolin8

iTrader: (2)

I just looked at that universal kit and thats not really a bad deal. I get heavy discounts through Precision though so i could get a turbo through them for alot cheaper. (i have a few turbo's lying around my house but they are all small GTI/EVO turbo's). It seems most people do a drawthrough setup with their kits but has anyone done a blow through setup? Generally speaking a blow throught setup is easier to tune and provides more accurate readings but im not sure how well the 8's MAF withstands the abnormal pressure. If it can handle a blow through setup then this wont be that big of a task.

Talic

a blow through kind of makes our maf useless, you would have to go standalone ecu and wouldnt beable to use the cobb
im going though the same process just about to lay the car down for the injector pull,intercooler install and exhaust fabrication see my link
https://www.rx8club.com/series-i-major-horsepower-upgrades-93/rear-fi-daily-driver-project-179348/

alnielsen

iTrader: (4)

Good luck with your project Spoolin8. I have been interested in this type of setup and may use it if I ever go turbo. Rotorocks original setup was a rear turbo, before he went with a mid mounted setup. Recently, david8 from Canada posted that he had created a rear mounted turbo. This was a few months ago and I haven't heard anything about it since. He posted at the end of this thread https://www.rx8club.com/series-i-major-horsepower-upgrades-93/sts-turbo-rx8-2005-a-47024/page3/

rotarygod

Just as a fwiw, some of the worst spooling setups are cast iron manifolds where the turbo is mounted right off the engine. This is actually a terrible setup and it spools much slower than a good header type of system that moves the turbo a bit farther away. Keep in mind I am referring to within about 2 feet or so.

ALL turbo system, no matter how small, how well balanced, or free spinning will have some form of lag. If you are a person who thinks this isn't true, go drive a supercharged car. You'll see what I mean.

As far as the rear mounted turbo goes, while it's not perfect (what is?), there is no reason why it can't be made to work acceptably. There is less exhaust energy at this location so the turbine side needs to be a little smaller but that actually doesn't mean more restriction. People make the mistake of thinking that air at any temperature has the same amount of energy in it and takes up the same amount of space. As it cools, it loses energy, speed, and increases in density. But the same amount of molecules take up less physical space so they can flow through a smaller orifice which in this case is a smaller exhaust wheel.

I actually find it funny that so many people will use a nonoptimal turbo for their application, stick it on a crap designed cast manifold, then run 15 feet of piping to an intercooler and proclaim that their system has no lag. A good exhaust going to a remote mount turbo without an intercooler can easily respond just as fast as these systems can in the real world of daily driving. STS's logic for remote mount is reall twofold. First it's easy. There is almost never a time during the whole process that your car can't be made to be drivable. Second is emissions. Regulations typically state something to the effect that anything before the maf and after the cat is fair game in the aftermarket world but nothing in between. By placing the turbo after the cat and plumbing it before the maf (if possible), they technically get around this.

Go for it. Report your progress. Many of us would love to see it.

Spoolin8

iTrader: (2)

Thank you rotary for putting the logic into writing. I know how it works in my head and can explain it in person but im bad at writing it out.

Currently im looking for a New TIG welder. A MIG welder would easily work for this setup but i would like to see about getting a new TIG before i begin this project. If i went through with this, i would be starting it in about a month when i can set the car in for the winter and have some time. Buying a house in about 2 months so have alot going on.

MazdaManiac

iTrader: (3)

Having driven many supercharged RX-8s, I have yet to find one that builds as much boost as quickly as a turbo car.
The "instant" boost that the SC folks claim is but a few PSI and the turbo almost immediately eclipses it.
Such is the problem with adapting a RPM-fixed air-pusher to a motor with as substantial a dynamic range as the Renesis.

Just like the word "lag" is improperly used here, I find the word "proclaim" to be suspect.
Who might be proclaiming something for which they haven't accurate data? I might want to have a word with them.

The exact amount of airflow that is available at the manifold is available at the tailpipe, minus any losses through radiation. Wrapping/coating/shielding might be properly employed here to great effect.
It is the same process to select a turbo for that position as it is for anywhere else on the car. (Now, whether or not an individual will actually engage in that process is another matter.)
The same goes for the cold side - the volume isn't really an issue, though the velocity is finite, so the delta flow will be different.

The only real drawbacks in a rear-mounted system are packaging constraints.
Getting the air to the motor and getting the oil to and from the turbo are going to be problematic for a number of reasons.

Brettus

iTrader: (2)

Very true - I've often wondered whether the SC guys appreciate this fact when they talk about laggy turbos . Sure it takes a little longer to build to maximum boost , but at low rpm say 4000 rpm when the SC only makes 3-4psi the turbo can make perhaps 12psi .
It does take a little longer to build that boost and that is seen as a bad thing but if you limited the turbo to the same psi as the SC i'm sure the response time would be near as damn identical .

JinDesu

iTrader: (2)

Short of being a terrible track driver, when you have 9k rpms to play with, and you generally should land above the 5k rpm mark at any point in time, when is a turbo ever considered laggy?

Just a little off topic thought, that's all. I saw the other rear mounted turbo thread, along with it's pictures. I'm quite interested in seeing this one happen. It's a cool idea to me.

rotarygod

I could really give a crap what a turbo does better than a supercharger. I'm the last person that needs a lesson on how they work or why. I'm just pointing out that ALL turbo systems have lag and remote mounting isn't necessarily bad.

MazdaManiac

iTrader: (3)

Then you might not want to make statements like this:
I wouldn't presume.

Once again, you are misusing the term "lag".

paulmasoner

iTrader: (1)

Anyone here with a brain knows that both of you know what you're talking about. and that both of you will come to the same conclusion ultimately when talking apples to apples. so why bother arguing(or not) over semantics and whatnot....

I'd REALLY like to here both your inputs on pipe sizing(hot and cold side) and your opinions/facts on how a cooler, denser exhaust stream effects turbine sizing. And how all that extra length of cold side pipe plays a role in outlet pressure/flow, versus manifold pressure/flow...

btw, something was said about making the car driveable in all kinds of less than optimal situations is a small part of a reason i want to see this discussion unfold(again, i'm still re-reading through the old rear builds)

MazdaManiac

iTrader: (3)

The difference between boost onset and lag is not a matter of semantics.

The rules for sizing are exactly the same - you need to know your optimal turbine flow to select the correct hot side and the cold side piping has the same trade-off between sectional diameter and velocity at pressure.

As a realization, you can use the same turbo in the front of the car as well as the rear, just go down one or two AR on the turbine and keep the piping to the same diameter as the turbo's compressor discharge (2", typically) to maintain the velocity.

2SeeKU

iTrader: (1)

Simple question. With the amount of free space in the 8's engine bay, why would you do this? I'm not trying to make a point, l just don't know much about this type of setup...