go single, is it worth it?
 

hey guys..

After all these yrs i am finally thinking about going single. My car is maxed out on the stock twins making 360 rwhp, trapping 118mph. but it isnt enough anymore. Seems everyong owning a ls1 these days get a shot of n2o and makes 500rwhp plus. My concern is that my car has been very reliable for the past 6 yrs and am worried about spending a ton of $$ to yield an extra 40 rwhp and an unreliable 7. How are you guys liking your setups? Is it a constant work in progress or is there a real a posibility of owning a 475rwhp plus turn key rx7?
Also why not go half bridge or full bridge when going single....why do 99% of the people outthere only go streetport when upgrading to single turbo?

i know this seems like a noobish question but i really havent spent much time reading about singles or porting. i thought i would be happy with my car with only twins...but its time to up the anti.

You have options as single turbos can be very reliable but so are the LS1 conversions.

If you keep the boost reasonable for the fuel octane you run, a single turbo car can be easy to tune to high 300 or low 400-ish rwhp and be a reliable daily driver if done right and tuned well. The LS1 is also easy to make 400-ish rwhp but with a bonus of easily passing tailpipe emmisions testing. Single turbo with aftermarket ECU is easier to buy, install, and setup as there are many known setups and turbo kits out that work but honestly the turbo rotary is more touchy to get right as things can go boom if little things fail (regardless of tuning). Failed rotary motors typically take out the turbine wheel and are generally expensive repairs. LS1's are relatively bulletproof by comparison to a 400+rwhp rotary but the install is a bitch if you are used to bolt-on type modifications.

My advice, if you love the rotary like most of us then a trip down single turbo or highly modified twin lane is a must ... learn to tune, learn to troubleshoot, learn to rebuild motors. You can always go LS1 later. If you have no love of the rotary then sell your car and buy a completed LS1 conversion, it will be cheaper and take much less time than converting one of your own.

475 whp turn key RX-7? LS1... Theres a guy with a 402 cid LSx motor with a mild cam with 500 whp. NA. No bottle no turbo no blower no ice on the intake no nothing.

As far as with a turbo, a bigger single than the twins you have making 360 whp would probably be MORE reliable, blowing out colder air and not having the boost control issues the twins are known to have. But, I dont know about 475 whp from a turbo on a 13b.

Im sure youd know a LS1 would be a LOT more streetable with that power and more reliable, but bare in mind either way youd be spending $$$ (turbo, or LS1 + stroker kit).

def wont go ls1. i love the rotary! have owned all three gens and been rotary only since 16 yrs old...i am 30 now.
My car has been bullet proof for 6 yrs and i have tracked and taken it down the 1/4 mile a couple dozen times. The problem is that i want more power given whats out there now a days. i am leaning towards a half bridge with a big single. But in doing that am i opening a can of worms? i dont want to ruin a perfectly good car (engine and turbos are still very healthy) for a headache. The car isnt a daily driver but the questions remains. Can i make 500plus and still drive the thing every weekend without dealing with annoying problems.

I think you could do an aggressive streetport, and perhaps a T4 35RS turbo, and be in that ballpark at 15-17 psi.

Yes, you're buying yourself some troublshooting/down time getting it right, but once sorted it will be very reliable. It sounds like you're a person with the wherewithall to maintain a rotary properly, so you don't need to drop a V8 in the car for "reliability".

You can pick up a used Z06 for in the 20's, so if you really want pistons, I can't image why you'd embark on a conversion when you could just buy the car.

There is a big debate about bp, half bp, pp semi and pp going on in this section. JD has written a good ammount of info on why its just not a good combo to go with a bridge, pp when using forced induction. I don't have tons of $$ to do R&R testing on different applications but from what i've seen at the track that is consistant are streetported turbo applications. Friend of mine (RX794) is making 450rwhp running very rich up top for safety on 93octane for everyday street driving. So just by looking at his dyno sheet he should be near 500rwhp at 20psi on 93 octane. Basically its all about tuning once again and what combo you go with in your application and also your $$ budget. Expect to spend anywhere from 5k-12k when you go single. Cost for a new motor, porting, turbo, fuel system, ignition, ecu and lots of dyno/street tuning time which isn't cheap..

i was thinking porsche twin turbo..thats the only car i would sell the fd for. and believe me it has crossed my mind.

but why go streetport when u can go half bridge....for emmissions? i never understood that. Does a half bridge reduce reliability?

Well, you alreasy loose a little bit of low-end power even with a mild streetport, and a large one will start making your idle lumpy. I would suppose it's a combo of drivability and emissions, but i'm no port expert.... don't the more aggressive ports also start to affect longevity?

i wonder if pianoprodigy ever sold his car...that looked like one clean single

If done right and with a knowledgeable owner you can have a great car. A 35Rs car would be a riot and you would be hard pressed to not grin from it. Stick with a large streetport it will make all the power you need. And yes it is certainly better than wringing the crap out of your twins.

-S-

matt,

roan at J&R on Long Island has a half bridge running a T66. I don't know how long its been running, but he has one :)

i heard his car once at the shop and it sounded cool but very lumpy idle. half bridge definitely makes it impossible to pass emissions. it also pushes the power curve further up the rev range decreasing low end power.

good luck.

hey alberto.

i was thinking t-51 or similar size monster. if i do make this change i am going all out. not gonna do it to make 430rwhp.

yeah the sound of the halfbridge is a definte perk. anyone have any vids?

I went the same way you did , maxed out my stock twins and after going threw three sets, I went single. A engine swap doesnt make sense, half of the FD's attraction is the rotary.

The only thing I didnt expect was some of the cost , its not cheap and its a process .

the "process" part is what scares the shit out of me. def dont want to tinker with the thing for 2 yrs to get it right. i want to drop it off and big up a 500plus rwhp beast

What unexpected costs and/or time-consuming "process" things did you run in to?

I went single and wished that I would have stuck with my twins, just because of the amount of odds and ends involved and money involved. If I were to do it all over again I would stick with non sequential conversion, CB, DP, and intake. I personally don't think that the 13B no matter how you get to 4-500 hp really is that reliable, due to the internals more than anything else. I love the FD and the rotary though, but from my view I prefer to enjoy the car versus run it on the edge and being tempted to boost higher and higher. The twins at least keep you limited. The single always seemed to be too easy to just bolt on a better one, and retune for more boost/hp. LOL... just my .02 cents. My RX7 went from a fun car to a money pit when I went single in my opinion and the enjoyment just wasn't there. good luck either way.

Look at what Carlos Iglesias has done (search). His car is teets and is probably in the ball park HP you are looking for. Either way speed cost money no matter how you spin it.
Regards,
Crispy
- no regrets over going single T

500+ rwhp is a different game, I thought you only wanted another 40 hp?

Now you are looking at a race gas application if you want any reliability or safety factor in the car, or you are talking 3 rotor on 93 octane.

If I built another turbo rotary I would build a 15 psi car and tune the crap out of it under all seasons of pump fuel formulations and intake air temperature combinations. Keep it simple, street port the motor, run a nice divided equal length tubular mani, pick a bb turbo with a q trim sized turbine and a large diameter low backpressure exhaust to keep the backpressure on the motor to a minimum, run a large FMIC, a PFC, run a 1 bar wastegate spring with no boost controller, and tune it conservative for 93 pump gas.

emmm sorry, but i am non seq.... and the turboes will boost to 1.7 bar any time!!!!

true they wont last, but they do spool up easily.... so i cant see how you are limited being non seq. my profec b boost controller mucked up, and i mis read 1.7 bar to 17 psi... DOH... and i melted a rotor and blew a seal. so trust me, non seq is still with its odd ans ends. I am going to TO4R .... so single should make life easier....its just my experience anyway. single is fine if you are conservative and are not a number junkie. ever drove a 400bhp car? it flies.... prudent tuning and saftey marhgins with a bit of porting and supporting mods will get you a long way.

George

Please explain why you would run no boost controller and a 1 bar spring vs a 1 bar spring and a boost controller.

1 bar spring with no boost controller = 1 bar, with no electronics to fail :)

your boost might be a little "slower" coming on, but thats it. all the boost controller does is it allows you to boost higher than your spring pressure would allow, and it allows it to pressurize the pipeing a little quicker by holding the wastegate shut a little longer. It then cracks it open quicker to stabilize the intended pressure ratio.

If you don't hook up a controller it will still boost to 1 bar without the cost of the electronics, and without the worry of them failing.

kenn

I forgot it's all about pressure and not flow, and heat generation right..... just keep running your twins at those numbers and let me know how that works out for you.

This is gonna hurt someone.

good explanation Kenn

you noted both the positive and negative aspects of having the boost controller

kenn_chan is spot on for the protection from overboosting and the cost savings, also saves weight for those weight junkies out there that are looking for every ounce.