Looking for some good advice on here for turbo sizing, not brand or specific turbo, just the sizing.

First for my current setup, and intended purpose. The engine is an S4 turbo engine, with a street port and exhaust port. The current turbo is a t04 hybrid, with an a/r 70 cold side (I don't know the specifics of the wheel, but told the setup makes 300hp at 14psi). The purpose is for drifting, and I would like the engine to make good spool time, and good power, in 3rd gear at 4k rpm (for the occasional instance coming out of tight corner that goes into high speed instantly). I also would like to make around 400 peak hp. Peak power isn't my main concern, I primarily would like strong fast power in the 3500-6500 range if possible.

I was originally thinking a .63 turbine housing would do the trick, but after looking into the size of the stock turbo trims, that might not be such an upgrade. So I've been looking more into .82-.84 (or is that still too small for a ported motor with tune). Next wheel sizing, would an inducer of 73.9 and exducer of 58.3 be good for a .84 housing (or around). The compressor side, I'm thinking the a/r 70 is good, but wheel sizing I'm not particular on. I know for spool time it's best to have a smaller inducer part of the wheel, and larger exducer. So maybe inducer 56.2 and exducer 72.9 (or any where around). I am trying to keep a good wheel diameter ratio of 1.2 or 1.3 max. Last is wastegate size, normally cars run 38mm or 44mm, but I see a lot of rotary guys running 50mm, why is this?

So keeping in mind my use, and my goals, what sizing do people recommend using. If you have a turbo that works great and sounds like it meets my goals, then please let me know, but only if you know your exact sizing. Any input is also for knowledge that will help me understand the rotary engine substantially.

 

Budget?

 

GT35R with a well built manifold and 3.5" downpipe at a minimum. V-mount with short IC piping.

thewird

 

I would go with the Borg warner EFR 7670 turbo. Sppedjunkie has one on his and it rips up here in CO with thin air. Boost comes on in the 2000's rpms and runs strong all the way to redline. I think he runs his at like 25PSI. He thinks his power is around 360-380WHP at 6,500ft above sea level. More like mid 400's WHP at sea level.


I am connecting mine up soon and will have input anytime now with a GT3574R on mine. I hope mine is like the EFR7670.

 

Nice, I am actually in CO. but am building the car for a Vegas series. But it doesn't really answer my question. With the GT35R or Borg Warner EFR 7670, what exhaust housing option would you run, because they're available in multiple configurations. Also what about comments on the wheel sizing, or mainly the wastegate size?

 

With a GT35R, get the T4 1.06 divided, it will fit your powerband goals perfectly.

The EFR only comes in one A/R that is divided without a wastegate which is 1.05 a/r.

With either setup concentrate on manifold design and exhaust flow and they will spool like hotcakes. If you can afford it, go dual wastegates so you can make your manifold 100% divided. Keep your IC pipes short and don't run an intercooler bigger then you need. It makes a difference.

thewird

 

Have got the EFR 7670 on order with the 1.05 divided external gate. (expect a 3-6 month wait so that might make your decision easier...) I think it will be a good thing but other than speedjunkie, I don't think anyone has any data on them on a rotor. Bit of piston info out there. Will be some time before i can offer any results, but I am setting out with similar goals.

GT35r is definitely a known quantity and readily available.

 

Precision PT5862 CEA

Same turbine size as a GT35R, but a smaller more efficient/faster spooling billet compressor wheel. Along the size of a 60 trim To4E. Get it with a T4 1.0 divided turbine housing, run a 3.5" exhaust system and dual open waste gates.

 

.84 not 1.0

 

^^^ Elliot, know of any actually being fitted? Looks decent on paper, although you are always in the dark a little with precisions with no compressor maps.

 

Thank you so much for all the info and recommendations everyone! From the information given I was able to do a ton of research. It seems as tho those are the perfect options for the exact power band I'm seeking.

I don't have enough money to go with dual Tial wastegates, so careful attention will have to be made in my custom manifold design. I'll be sure to post my setup when it's completed this winter, and let everyone know details on how it works out for me.

 

I actually do have one other question. With my S4 13b, is there anything specifically internally I should be aware of that is common to fail under high power (350-400). I am basically building it factory with the Rotary Aviation's kit, with the exception of the Atkins Rotary solid corner plugs, and careful attention to the clearances Pineapple Racing advises in their videos. A lot of attention is also being placed in dual oil coolers, radiator setup, fuel cooling, pre-mix, and Haltech Sprint RE for max tuning capabilities.

Lastly - E85 yay or nay

 

Change to S5 irons which have the bigger dowels to get rid of the possibility of cracking plates.

thewird

 

I have fit several, haven't seen them dyno yet however...

 

Cool. If one ever surfaces, it would be good to see.

 

You've almost described my setup Can't wait for the day I can drive this thing.

GTX35R 1.06 T4 divided, dual 44 wg, shortest divided manifold, v-mount with shortest piping, 3.5" downpipe. I'm expecting over 400whp and also expecting this thing to spool like a mother and have good on/off throttle response.

 

^^^ Would look forward to results on that setup. How far away form getting up and running are you?

 

^^^ Not long to go, I'd say a week or two, three weeks max. Although I have to run the engine in first.

https://www.rx7club.com/build-thread...ssible-989042/

I will update my build thread once it's done.

 

I would say yay, especially for a track car. E85 is a great fuel IMHO especially if you are going to be beating up on it. Has great detonation resistance (particularly helpful in a rotor) and also helps reduce temps..intake combustion, exhaust so it's all good. Just make sure you have a robust fuel system to deliver required fuel.

 

Well if it has great detonation resistance, then I should definitely go that route in my fuel, and tuning setup. I hear the number one thing that kills rotaries is detonation, like instant K.O.

 

Correct. Rotors are nowhere near as forgiving as piston engines with det.