BlastinSideways12A

I worship your car! Once I finally get my degree I'm gonna try something similar with a 13B-RE and twin GT25Rs. Parallel twins are definately the key to a fat torque curve, quick spool-up, AND high horsepower for the rotary.

No_Rotor_RX7

i'm soon to find out what twin 60-1's will do

brent clement

HA, Ha, I love it. Nice to see some guy's that aren't afraid to do something different. If it was easy everyone would have it. Thanks for the props.

BlastinSideways12A

Alot of people who think they know everything would probably say something along the lines of "a big single will make more power than twins thats a waste of money" although they have no clue that parallel twins and sequential twins are completely different. This is gonna be one of those mods thats somewhat commonly done in a couple of years much like the halfbridge turbo setup that everyone said wouldn't work, and did.

Hell, 255 RWHP @ 7 psi with full boost at 3,000? On a stock ECU!? What single setup can do ALL of that?

BTW, what kind of fuel economy numbers are you getting?

brent clement

Mileage is hard to tell right now I'm running a 12a gearset in the tranny so my speedo is out to lunch. Somewhere between 15-18mpg. Your right of course, I've heard the big single, twins is a waste of time spiel about a hundred times. The purpose of this build was to promote my shop. That and it was a lot more interesting and fun to drive than a big single. If they want to wait for power all the power to them.lol. We'll see what they say when I crank the boost up in the spring! Thanks for the positive feedback. I hope your wrong about it being common though.

Brent

MetalX7

i gota say again, awesome setup. I've always wanted to do something similar but i get the "single turbo is bettar!" everytime ... and i don't know enough about this to argue back =\

i've asked this before on another forum and couldn't really get a clear answer.

(these are random numbers just to make this easier)
Twin turbo question... lets say that 1 turbo can give you 100hp at 10psi, when you have 2 in parallel, do you end up with a 200hp gain? (twice the flow if i get this right). That's if both turbos are the same ... what if they are different size? (GT25R and a GT28RS for exemple)

I tried to search but the amount of results i get makes this hard to find. same for google. let me know if there's a thread with that info already. thanks

brent clement

The short answer is that 2 flow more at a given boost. Can't say for sure if it's double the power though. If I ran a single at 7psi I would definitely not get the #'s that I have. All depends on which turbo's as well. I'm not by any means an expert on turbo's though.

MetalX7

me neither ... my other car is turboed so i know a bit how it works (i'm also reading maximum boost like everybody else lol) but yeah, i always wondered if thats how it was working.

basically yeah, im sure you don't get exactly double the power but id much rather run 2 turbos like you than a bigger one for the same peak hp ... much better power curve with the 2 turbos i'm sure

BlastinSideways12A

Next project... 20B with 3 turbos in parallel!

No_Rotor_RX7

^^^ that's been done hell i think even racing beat pulled that off years ago. this isn't a new design for rotaries by any means... it's just not common. which is pretty cool. 90% of the people in this scene want to go the easiest route. buy a kit that is proven and just drive. nothing wrong with that.

i've been planning a twin setup for a while now, but i only wanted to do it when i got a good TII body to build on. i ended up putting a turbo v8 in my FB to get me by

anywho, my turbos are in and i just have to port my engine and put it back together. i'll be using 3" downpipes off each turbo and collecting them in to either a single 3.5" or 4" exhaust. the plan is to eventually run 20psi on pump gas/ alcohol injection. these turbos flow enough each for just under 400hp so combined i should hopefully hit around 600hp. gotta remember that 400 piston hp is about 330 rotary power. either way, that will be enough for a street car........ the torque and powerband is what i'm really anxious to see with this

i think when you turn up the boost on yours Brent that it's going to be a power curve similar to that of a well built 6cyl hahaha. hell it already is!

MetalX7

now get one of those 6 rotor engines and put 6 turbos on it

https://www.rx7club.com/rotary-car-performance-77/ok-so-6-rotors-now-586386/

No_Rotor_RX7

bwaahahahah that would be absolutely out of control! ....


maybe we'll try that! we're already talking of building a turbo 4 rotor 12a

MetalX7

oh the things i would do if i had money haha ...

what's the biggest challenge in making something like a 4 rotor 12a? excentric shaft?

No_Rotor_RX7

yep, pretty much the e-shaft is the biggest hurdle. we're looking at taking two 12a shafts and machining them together which all in all wouldn't be too bad, but the balancing is going to be a task. other than that it's just stacking and making manifolds hahahaha

MetalX7

eh ... sounds so easy ... lol

maybe i'll look into it next year. i like being different

brent clement

It's like you guy's peaked into my brain. I've got a million more ideas I'd like to try. If only I had the time and money. The only reason that I went with t25's was because they were easy to get. My buddy goes through a lot of sr20's.lol. Not to mention he does a lot of swaps.

Brent

No_Rotor_RX7

the main problem i see with the t25's is the super small hotsides. i'm running .68's on my twins. t25's have .48's dont they? since you have the exhaust ports opened up like i'm doing you could benefit from the little larger hotside. especially when you crank that **** up!

regardless one stock t25 on an sr20 usually makes around 140 - 160rwhp at 7 - 8psi. so figure your making 250rwhp at said boost level then it's safe to say you really are doubling the power output from having double the same turbo gotta love it!

brent clement

The hot sides really aren't an issue since there is one for each rotor housing. That allows a fair amount of flow. Anyway you slice it though, I haven't even turned them up and I want bigger turbo's.LOL. Can't wait to see a large twin set up!

MetalX7

are the T25s on DSM the same at the SR20 ? they can make decent power from what i heard

i have a GT25R on my other car and it makes ~240whp at 16psi (on a FS-DE 2.0L)

brent clement

No idea, sorry. All I know is the t25's I have won't push more than 12-13psi safely.

BlastinSideways12A

This is a thread of a bunch of kickass fabricators! Me, I have next to no welding experience but its definately something I want to get better at. Over break this December once I finally own a welder of my own I'm gonna build a catback exhaust for my daily driver. (Probe GT which has Mazda's 2.5 V6 and a very smooth sound) I've already got all of the materials except for stainless 2.5" flanges. (can't find them) I'm also using 2 2.5" magnaflow stainless universal round straight-through mufflers, a 4" canister as a presilencer and a 6" canister as the main muffler.

Anyway, I'm just starting off in the welding world but I'll figure it out eventually. I do have a great deal of design knowledge as I am a 4th year Mechanical Engineer and Electrical Engineer dual major so that should help me out. I'm also fairly experienced in cutting and grinding different things so I should have no problem getting something ready to weld together.

In case you were wondering I do have an 85 RX7 project which I am working on. I've got the limited slip and rear disk and am building a 91 TII engine streetported with 9.7:1 rotors beveled and a rebalanced rotating assembly. It will be all motor for now but the bevels do lower the compression to ~9.25:1 so some mild-moderate boost may someday be in order. I still have to strip all of the undercoating off and so some minor rust treatment, ect. and I have the entire factory harness out because I am re-designing the entire electrical system with the battery, fuses, relays, ect in the storage bin areas. I'm hoping to weigh in around the 2100 mark with full interior and power windows but no AC, PS, sound insulation, custom lightweight exhaust, 9 lb flywheel, ect. The engine SHOULD break 200 RWHP too.

Anyway enough of my rambling, you fabricators are my idols.

wyallen

I hate to be the wet blanket on all this, but 255hp @ 7 psi. is good but by no means great. Below is my best dyno run at stock boost (which on my car is 5.8-6.0psi, no boost creep) with a hybrid turbo (stock s4 hot side with a H3 trim compressor), totally stock s5 block with a stock ecu/F-CON in a very poor state of tune.

Not only did the hybrid turbo make more power at less boost, but it made more power sooner (I am not claming the performance difference is only due to the turbo). At 4k it looks likes the twins made ~180 ft/lbs and ~140 rwhp vs. 200 ft/lbs and -150 rwhp for the hybrid (both using CF: STD with Smoothing 1). I am by no means touting my numbers, many have made significantly more with the same boost using an aftermarket turbo (look for some of BDCs old runs), just interjecting a bit of reality. There is some seriously flawed statements in this thread, I would strongly recommend "Forced Induction Performance Tuning" by A. Graham Bell.

Wyatt

r0t0rhead

iTrader: (12)

oops, i was under my boss's name hahahah

No_Rotor_RX7

yea, your dyno graph is pretty common for what you have. we know this. hell, look at an FD with stock twins and it's even better sometimes.... BUT what we're excited about is headroom. your hybrid won't make over 400rwhp and if it does then i garuntee the boost will fall off hard due to such backpressure.

the great thing about two parrallel turbos is with each rotor having less pressure reducing egt's. two T25's will flow LESS than your hybrid i bet. this is a starting point for him. your hybrid will become inefficient around 15psi, his twins are already WAY out of their efficiency by 13psi. now i'll get my setup going and we'll compare yours to mine... then make your judgements.

i see where your coming from on this, but you just have to remember it's a baseline. there are a few people also running true twins with larger turbos making in the 600 range on pump gas still making full boost before 4000. you just don't get that from a single on a rotary.

oh and i've read "Forced Induction" amongst many other turbo and engine books. i've been working on rotaries for over 6 years and am part of a company that has been building race rx3/4/5/7's for 20+ years. i've seen almost any and every single turbo combination. all these "new" turbos you see coming out like the gt500 and gt35r etc... are based on almost the same wheels. a little more efficient fins but that's about it.

just give this time and i think you will come to realize the true benefits of a well done twin setup.

brent clement

What type of porting were you running? Your graph isn't all that smooth. Just to clarify, I never claimed these #'s were exceptional. Only that I'm happy with them. You definitely have some good points either way.