therm8

With the unavialability of the Greddy kit for automatics, I started thinking: What if I just design my own turbo kit. Now to be realistic, I don't currently have the time, workspace, or equipment to do so, but it did show me that I have a lot to learn before taking on such a project.

First: Low power Renesis airflow:
For a piston engine: (engine rpm*engine cid)/(1728*2), for a rotary I multiplied this by 6, since a piston engine only takes in air every 2nd revolution and the Renesis takes in air 6 times every revolution(*)

So at 7500rpm (2500 engine rpm) i get 347.222 cfm. 138.888cfm at 3000rpm.

Second: turbo efficiency maps:

assuming i want to run 6psi of boost, PR =20.7/14.7 = 1.4
I've seen many people use 1 lb/min = 14.472 cfm so I'll use that(*)
for lb/min(m^3/sec) do i use the airflows above?? ie at 7500rpm = 23.992 lb/min (0.164 m^3/sec) (*)?

Assuming I have a tenth of a clue about all of this. I picked this compressor map as being the best map (that I could find) for the Renesis at 6psi of boost max. (Mitsu TD06-17c used on the 4.3 gmc syclone):


map

(*) = assumptions and calculations that I'm unsure about.
So now someone who knows about this stuff, come along and fix me

Richard Paul

iTrader: (5)

That should give you about 170 hp

therm8

lol i already have 'about 170hp', guess my left brain isn't working right today.

Richard Paul

iTrader: (5)

Maybe you do and maybe you don't. But the ren needs 1.3 lbs/min to make a hp.
A piston engine gets 1 for 1
Sorry, that's the fact I learned the hard way.

therm8

I figured out that I messed up some calculations. Didn't factor in density or boost press.

I get 30.957lb/min @6psi (corrected) which leads me to choose this turbo:

map

again, this is all assuming I've calculated anything correctly, please correct me if I'm wrong.

Richard Paul

iTrader: (5)

You know what, we have a member of the forum called Rotarygod. This is his specialty, he knows all the turbos and knows rotarys. There can't be a better man to turn to and he will do it for free. He likes to write. So just wait awile till he spots your post, I'm sure you'll get advice that you can count on.

No sense in me giving you a wrong direction.

therm8

heheh, I've been hoping he'd show up, guess I'll have to wait :D

Japan8

Tuning and reliablity may be a real b!$&%, but otherwise... you could used some of the Greddy parts to help things along... cutting down on some work for you. I don't think that you'd have to fab up too much other stuff... maybe just the manifold.

MazdaManiac

iTrader: (3)

Good pick. The GT35 is a good choice for a medium to low boost application on the Renesis.

The max flow is about 250 CFM N/A (18.4 lbs/sec).

JeRKy 8 Owner

Wheres the guywho is supposed to have figured out a way to get Canzoomer towork w/automatics?

dannobre

iTrader: (3)

The CZ will work if you do a custom map....just start over, and tune it. It will work the same as the 6Sp...just will need very different map

rotarygod

You guys are talking about me again!

The first and most relevant question that I have is how much power do you want? Don't base your mod on boost pressure. Pressure is irrelevant without knowing the amount of airflow in cfm. Since the engine makes it's power based on effective compression ratio and not static compression (10.0:1), the amount of pressure in the intake manifold is irrelevant so long as the same amount still enters. A large turbo at 10 psi will flow far more air in cfm than a small one at 10 psi and therefore should make more power. Just assume they heat the air up the same. Decide on an output goal and then we'll figure out a good turbo from there.

FWIW: My friend Brian in Dallas made 425 rwhp at 15 psi on a 60-1 HiFi (the small one). Check out it's efficiency chart. For 350 rwhp or less, I'd just probably use a T-04B with a P trim exhaust and just size the a/r housing for my need.

MazdaManiac

iTrader: (3)

Not enough room for a T-04b exhaust housing in the Greddy (MazdaManiac:p) position.
The T-04e compressor housing only fits because of the angle at which I have it mounted.

rotarygod

Just remember the number one rule of fabrication. "If it doesn't fit, you just didn't get it going fast enough!"

MazdaManiac

iTrader: (3)

Ouch!

Not my idea of good machining practice!:p

therm8

Personally I'd like to have about 260-270 shaft hp, although what i'm really after is some midrange torque. I don't feel that the tranny would be able to handle more than that (if it can even handle that much). And I have the feeling that beefing up the auto tranny isn't going to be as easy as beefing up, say, a 700r4 or 4l60e transmission :p . I was just kicking the idea around anyway, while teaching myself about turbos, and compressor/turbine maps. I just refuse to pay 5 or 6000 dollars for a kit.

Rotoman

Does anyone know Which is a better turbo for the RX8 and why ? The Greddy T618z or the SSR/SFR TD04

rotarygod

"Better" is really a subjective term. It depends what you are looking for. The Greddy turbo is pretty damn small. Don't plan on turning the boost up much with it. It is probably best for a nice power gain with good low end response. The SSR turbo on the other hand is based on the T-04 series of turbos. These can be configured in an almost infinite number of ways to do everything from a small upgrade to a serious horsepower monster. The T-04 definitely has more power potential. Which is the "better" turbo really depends on you and your needs.

Rotoman

Rotarygod thanks, Greddy did tell me that the T618z will support up to 20lb boost, would'nt
that be more than enough since the RX8 probably can't handle more than 7/8 lb

rx8wannahave

Gosh, I've been hanging out in the "common" places on this website:

RX8 Disc
Multimidia
Etc etc

Comming here for the fist time has shown me..."I know sooooo little about mod's"

Turbo/SC, etc....I could never do this on my own...I know nothing about it, well...humbled once again in life. It's OK...it's OK to be humbled...just not good for the ego!

I need a teacher...LOL

rotarygod

How much boost a turbo can physically produce is irrelevant. It's how much air it can flow, not at what pressure it can do it that counts. Can it (a turbo that small) flow enough air at 20 psi to efficiently boost a Renesis? When monkey's fly!

Rotoman

Thanks for the education, I knew I was talking to the right guy..

Japan8

I'm not going to doubt the master here, but I do recall having read that Greddy used a different exhaust wheel than normal. But that would only affect response... right? TO push more air you need a bigger turbine wheel?

rotarygod

The turbine and the exhaust side play a very important part in making good power. However, with a turbo that small, in order for it to make 20 psi of boost at the required flow rates for a Renesis, it would have to be spinning pretty damn fast. That is not going to be thermally efficient. This assumes the exhaust side can handle it. If they had a turbo that could run 20 psi on a Renesis, they wouldn't use it to produce a low boost kit. That would make no sense efficiency wise.

Rotoman

Hey Rotarygod, I guess we established that the T618z could not provide the Renesis with the proper flow rate for the 20 lb bosst they said it can go up to. But would this Turbo provide a better boost rate than the T04 would with less lag to say maybe 10lb boost, just want to pick your Brain alittle, Thanks