winzie

Has anyone ever done a rear mount turbo in a rotary ?
If yes or no, can we have a discussion on the pros & con ?

RoTaRyBoYz

weyyy sah that car turned out nice boy, i remember reading the other thread about the build up....do u know Rana?? the guy with the 20b cosmo, thats meh pardner contact him he have alot of rotary parts & he have a few good contacts in Australia....good luck with it

saltyslug

I have a 12a turbo in the back of my vw baja. close ratio 4sp bus box. 1-3 is super fast. 4 is for the highway, I don't know how fast it is boosted but na it hauled ***. should be good for 11 sec passes

xrotaryguy

I have heard that rear mounted turbos spool nicely and do not need an intercooler. That sounds like bunk to me though. Seems like running oil and coolant (if necessary) lines would be an issue as well.

On the flip side, if you don't have much space under the hood, then maybe it's a good way to go.

Directfreak

iTrader: (2)

I would love to see a Rear mounted Turbo option for an RX-8.

trochoid

iTrader: (6)

I saw one of those installs on a Camaro, either in a mag or one of the diy car shows. I find the idea unique and interesting and may have potential for the rotarys heat issues.

I just recently ran across the thread on your build, all I can say is OUTSTANDING job, love the paint scheme too. I your situation/setup, this might be an ideal course to pursue, though I next to nothing about them. A small pump, with ducted air flow to a transmission cooler might be the ticket for oil cooling the turbo in a closed system seperate from the engine oil.

Other issues such as turbo lag, intake charge ducting and repiping the exhaust may be the biggest hurdles to get over. As short as the Mini is, these issues will be minimized and may be a very viable option.

winzie

Yea I spoke to Rana last week.
I am trying to get in contact with an Aussie.

winzie

Repiping tha exhaust is no problem. The only thing is what size pipe to use and what material is used to ( wrap ) keep the heat in the exhaust. The turbo will be about 50 inches from the engine. Is there any engineer that could throw some light on this?

calculon

iTrader: (29)

i am not a fluid dynamics engineer by any means, but i took a few classes in getting my degree

basically the only con (fabrication/cost wise) is going to be the complexity of the piping

the only con (performance wise) is going to be added turbo "lag"

it's hard to tell how much of an impact on lag there would be since the majority of the additional length of piping would be straight (thusly the pressure drop would be minimal compared to bends)

pros would be less heat sinking into the motors intake charge from being in the engine bay the whole time. i don't know about not needing an intercooler, but it sure would make using an air-to-water intercooler a bit more appealing in my opinion since the plumbing to the IC and associated reservoir could be pretty greatly simplified.

all i can say for sure, is that i'd love to see some data points on these types of systems. with my limited knowledge on the topic, i can't offer any quantitative answers, just general principles. mostly common sense stuff i'm sure you already knew.

dantheman

iTrader: (4)

you would see more lag by installing a intercooler. The time to fill the pipe is like .3s for a rear mount turbo on a honda.

SPOautos

Yea, think about it like this....if your flowing 600cfm (10 cubic feet a second) how long do you seriously think it will take to fill a 2.75"id pipe thats say 10 feet long? Thats roughly 1,036 cubic inches of space to fill which isnt even a cubic foot.

I wouldnt worry TOO much about the lag time from long IC pipes. The main thing is you loose a lot of exhaust energy. heat = energy and you dont have as much of it 4 feet farther down the exhaust. What you might consider is building your headers and exh pipe out of a high grade stainless like 321 then wrap it real good with a thermal barrier wrap to keep as much of the heat as you can inside the pipes all the way to the turbo.

If you plan on running more than about 7psi you should run a a IC

Good Luck with it,
Stephen

KeloidJonesJr.

iTrader: (8)

GL going to take alot of money and labor.

trainwreck517

iTrader: (1)

I've seen it done on V8 comaros, and there is no noticable lag. I think the lag, if any, will be less then then 1/2 a second compared to a turbo sitting in the engine bay.

I would thremo coat/power coat the exhuast pipe leading to the turbo, along with thermo wrap to try to maintain as much heat as posible.

Good luck, and be sure to post some pictures.

trochoid

iTrader: (6)

Ceramic coating, inside and out, along with mounting the bov as close to the throttle body as possible will help reduce lag. Keeping the exhaust piping at 2-1/4" will help keep velocity up, depending on turbo size, 2-1/4 may choke it off too much.

winzie

This is good input.
I am absorbing a lot.
Keep it coming Guys.

-efini-

The rear-mount turbos is really for vehicles that cannot fit one right off the manifold, and for running a single on a V-type engine. Ive only seen one full kit before and it is designed to be used with a chevy 350. Honestly, its hella stupid. Theres No need for it on our cars. We have plent of room to fit a turbo. SPLauto was right, having the turbo at the end of the exhuast isnt as effeiceint because the gases lose some velocity by the time it reachs the turbo compared to regular setups. And yes if your going to run anything over 5-7psi you need an intercooler.

z-beater

Ok, here are a few things to add. I will be speaking purely theoretical. Sorry if I repeat.

Personally I do not feel this is an ideal setup for a rotary. Of course it may work on BB or SB v8's. For goodness sakes there is a guy locally that is running a 106mm turbo on a SBC producing 1260 something to the wheels on a dyno dynamics dyno. He hits full spool(35psi) at just over 3500. Now lets look at what a rotary will produce. Take mine for example. 61mm cold side with a 1.0 hotside. I will hit full spool (15psi) at around 3500-4000. Fair comparrison? I think not. Anyone that has studied turbos knows that the objective is to get as much exhaust energy possible to that hot side. There are a couple ways to do this. 1. Wrap/coat the manifold or 2. most importantly get that turbo as close to the block as possible. Now I fully understand that the closer you get the turbo the worse it is. You are stuck in a catch 22. Not all systems that are designed are going to be perfect. It is all about compromise.

If I were to run a rear mounted turbo I would do what tochroid suggested. Run 2 1/4 pipe, coat inner/outer and then wrap. If you are creating an inneficient system take all the precautions necessary. Build it to your best ability.

Same goes for the IC. Don't build an inefficient system. You don't have to run a IC, but at least put some sort of cooling in there. For example, Water Methanol Injection.

I do not know your particularly build, maybe you could provide us with a link. But judging by the picture your car is strictly race.

Personally I would rather push the turbo farther forward. Piping will be a lot easier to route. Not to mention that overall cost would be cheaper. You could push the turbo far enough forward so that it was a direct drop into the IC(run a FMIC). At that point you would only need to fabricate the exhaust manifold and IC pipe on the left hand side. I know that it was mentioned before but less IC pipe = less lag. Yes I know this is fairly minute. However remember we are still talking theoretical.

That being said let's address the heat issue. This is where the rear mounted turbos really excel. As mentioned before since the turbo(s) are no longer in the engine bay the ambient temperatures under your hood will decrease this will vary on the setup you are running however I feel that there are other precautions that can be taken in order to reduce, ie turbo blankets, shield etc. Let's take for example a turbo that was placed mid car(as you stated will happen). If you were to have ideal exhaust velocity(ie right off the block) you would still be creating heat. However if you have longer IC pipe then that heat would have a chance to dissipate as the fluid travels through the pipe. In addition to this cold air will be flowing across the pipe. I was curious as to hot the IC pipe got so I ran a quick test. On a dyno and steady state tuning(gets the car the hottest) I was at about 80 degrees F before the IC. After it traveled through the IC I had a 10 degree drop on average. I am sure that you would notice a larger drop due to the pipe being so long.

When it comes down to it there is no need for a rear mounted turbo if you have the space. But if constraints do not provide you the option to choose then it might be a viable option. If you are going to build something from scratch then why build something that is inefficient?

Hope this helps...

fcdrifter13

You guys talking about something like this

http://images.google.com/imgres?imgu...lr%3D%26sa%3DG

trainwreck517

iTrader: (1)

First of all, your hot side is way to big, .86 would be better.

On my friends drag car, with have .96 hot side, on a T-78 BB turbo, made my turbonetics.. and he has full boost by 3.5k rpms, thats 38psi!

On my Street port motor, with a .86 hot side, and 60-1 compressor, I have full boost by 3k (14psi)

Yes having the turbo closer to the engine will help alot, but having it farther back would not cause a huge lag.

-efini-: Do you even know what car he is mounting it on?
If he is going threw the trouble of running the turbo in the rear, I'm sure its because he doesn't have much room in the engine bay.

xrotaryguy

Yeah, I think that the Mini is all out of room up front. A lot of SBC's and v6's etc use a cross over exhaust pipe from bank two to feed the turbo, which is mounted more conventionally to bank one. I still think that a rear mounted turbo is not as good as having it right on the manifold, but you have to put the thing somewhere. You're not the only one. It must work

z-beater

If you read through my post I was speaking theoretically. I don't know why I have to even put disclaimers in the text.

My hot side is not too big. I have clipped a few turbo setups from the single section, take a look:

Turbo: 60-1 .70 intake, dry center, p-trim exhaust wheel with 1.15 divided housing

Turbo: HKS T04S P-trim AR 1.00

Turbo: Garrett BBT-70 1.15ar

60-1 Hi-Fi turbo .70 compressor 1.15 A/R turbine

Turbo: Garrett GT 35/40 1.06 a/r

Your friend has a BB turbo as well, and as we know that is a better setup for spool time. Both turbos in my comparrison were non-BB. Even if your friend does spool his turbo by 3.5k do you still think that it is fair? The turbo on the V8 is a lot larger.

I am not here to quibble over my setup. I thought that I would just add a little bit of engineering and try to illustrate this point with a few examples.

rotary guy, that is a good thing to know. I hope that he posts a link with some pictures. I would really like to check his car out.

winzie

Checkout this site: http://groups.msn.com/winztek
You will see the MINI

z-beater

Nice build. And I can see the space issues that you are woking with. I have a couple questions though.

1. The picture with the turbo on top of the engine, is that where you are planning on sitting it? If so I would like to see how you built your manifold.
2. How much room is up and to the right?

It looks like you have a fairly tight fit. Other than the heat issue it might be possible to put that turbo on top of the engine. IC pipe would be interesting that is for sure.

Or it still looks like there is a little room on the front right side. Either way good luck and I hope that it works out for you.

dguy

iTrader: (8)

Probably already been said but the issues really isn't loss of exhaust velocity per se, but the loss of thermal energy via radiating heat and dissipation.