Hey everyone,
So I've been looking into reading compressor maps and such so that I can effectively pair a turbo to the renesis engine. Along the way I became curious about if I could find a turbo that would be effective in a twin turbo set up.

I found a BW EFR 6258 with a 58mm turbine and. 85 a/r to be an incredibly effective and efficient pair for twin turbo on the renesis. It can produce 7psi of boost at 3500 rpm, 9psi at 4500 rpm and hold 11psi from 5500-9000 rpm. It also has a very stable delta pressure or +2 from 3500-5500 rpm +1 for 6500rpm 0 for 7500rpm and -1 for 9000rpm. It also maintains a pretty stable intake charge temp of 80-88°F from 3500-6500rpm and 88-94°F from 6500-9000 rpm. I've posted screen shots of the specs and info used to determine this calculation along with the mapped points on the compressor and exhaust maps.

 

This may be useful to you if you've never dealt with turbo rotaries before. The math is a little different because we take more air than a piston engine. Most calculators don't take this into account at all.

https://www.rx7club.com/auxiliary-in...-fuels-882676/

 

What do you meam by take more air? I know that the general assumption of 1lb/min of air equals 10 hp when applied to piston engines, and that the rotary is more like 1lb/min air = 7hp. However I only see how that would affect the calculated hp output on the calculator. Most calculators are only going to be accurate up to an extent, I used this more as a general guide to how the compressor/turbine match would work with the renesis. As with any engine build I always expect that the hp gains will be 10-15% lower than calculated for example, if you calculate it out to make 350 RWHP I would expect to see maybe 308-315 RWHP in reality.

 

Also remember that those calculations are based on 1 turbo and 1 rotor housing. So that 23.38lb/min of corrected airflow at 9k rpm would actually be 46.76lb/min with both turbos installed. So calculated hp at the crank would be appro. 46.76x7=327.32 - 15%= 278.22. I'd be very happy with those numbers in reality. For a quick spool time, and with boost coming on at 3500 rpm you can still employ economic driving style at cruise. Win win in my books, decent boost, quick spool, relatively low intake temps and a pretty good exhaust delta pressure. My bigger issue with it would actually be packaging and installation as getting two turbos under our hood in a clean and accessible manner would be an interesting endeavor to say the least.

 

i think red is saying in general a rotary requires more air (n/a of f/i) to work than a piston engine

 

Yes, the 13b-msp flows more air than its 1.3L piston counter part. We are more comparable in flow to a 2.6l piston engine. For the calculator I used and piston engine displacement of 1.3L to account for the flow for 1 rotor housing feeding 1 turbo. i assumed this would account for the flow differences between a rotarty and piston engine.

 

why bother with twins in the first place? going to a single proper turbo is a go to mod for fd owners. really trying not to make the joke about bolting on the b-rew twins on a renny

 

Well as to why, I'm not really sure yet. I really like the numbers this turbo puts out being run of one rotor it gives a nice bosst level and good air flow at relative rpm. Doesn't create uncomfortably high air intake temps. For a daily driver it seems like a nice ratio of power, with a quick spool time.puts you right around 300whp. Yes at the downside to more piping, more fabricating, more weight and more cost. Im going to be doing the same thing for a single turbo as due to complexity and cost it will be the cheaper option. Im curious to see the difference in data for the single vs the twin tho. This thread was more so to put out there this turbo for our renesis as a twin turbo set up and get people opinions on it. Most threads are just hey I wanna twin turbo will this univeral kit work on the 8? In this thread I posted what I think would be a good match for a twin turbo set up so that people can weight in on the topic.

 

the 8 has been around since 2003 and i dont ever recall seeing a twin set up. low mount, top mount, sfr sure but never saw a twin. i dont think there would be room without serious fab work. im guessing these wouldnt be sequential so would the distance from the exhaust ports (turbo placement would be different for each rotor) make a difference?

 

I mean, technically we only have one bank of exhaust.

Parallel twin turbo setups are usually seen on engines with 2 banks, AKA V engines.

What you are doing is like having a turbo for each individual cylinder for a piston engine. Just the amount of space this will take up will be a lot. I don't know how you would route this.

As for a sequential setup, 200 is right. I have an FD owner who says getting a twin scroll single turbo is a lot better than having the stock sequential turbo. It was necessary 20+years ago, but not anymore.

 

Im not at all denying that the installation would require serious fabrication. I wanted to talk about how the above compressor/turbine housing pair would function on the renesis as a twin turbo. With the middle port divided in 2 runners with each runner merging with 1 of the primary exhaust runners. Each bank would than feed each turbo individually and merge together after the turbos.

 

Ok so upon comparison to a large single turbo it become clear that booat throughout the rpm range can still be had, the only difference is the twins create a fraction less heat up top 1° more for intake temps and a slightly higher delta pressure up top - 3 instead of - 1. So in conclusion the fractional advantages of twins are far outwayed by the added complexity and cost of the twins. Which it is clearly possible to do the only reason to do so would be for bragging rights it would appear.

 

its your money, good luck. this is getting too technical for me. maybe brutus will chime in