Turbo setup (FD) for road courses?
 

Right now my FD is still bone stock, and I'm going to be going on a small spree to start my reliability mods. Before I buy some of that stuff though, I need to know what sort of turbo setup I'm going to be having at completion.

I've had some people say that the stock twins work pretty well for road courses, while some others say change to a larger single.

I've done some looking, searching, and debating, but still have not been able to come to a good conclusion so far. What do you guys have to say???

single for sure
more linear powerband for road tracks, plus you can get some good power out of one.
the trend these days is the GT35R would be worth looking at..

According to the track junkies on here, it appears that the sequential twins or the BNR upgraded sequential twins are the best solution for a responsive track car. I have read that a small single, like the RX-6, works well too.

I'm sure a search would reveal a thousand threads, which often makes it difficult to distinguish a good thread from a bad one.

I think when it comes down to it, a set of stock twins in good working order with all the bolt-ons is a fantastic track/street setup. You can probably hit 300-350 rwhp, which is pretty much all you need at a track with a street car.

For me, I could never get the twins to work right, so I switched to a single, which has worked out great for me. Still, even with the smaller single, I sometimes miss the low-end torque of the stock twins, and the car's not even close to being smog-legal anymore.

Going single would simply provide way too much smog complications (especially if you live in Cali), but if smog's not an issue, and you want that extra power up top with some cash to burn, go single.

Stock twins:
Unbeatable low-end power
Smog legal
Capable of putting plenty of power for street/track use

Single:
Higher potential for high horsepower
Illegal
Simplicity (FAR fewer hoses and complications)
Higher Cost

I think those are the advantages/disadvantages in a nutshell.

I should add, you should come up with a long-term plan for the car, and that will dictate the route you take.

If you're looking for a nice street/track car that you can potentially sell later on down the road, I would stick with the stock twins (or upgrade to the 99 specs). If you're thinking of potentially making a track-only monster, definitely go single (the car will never see the benefits of the low-end boost anyway, and you will get the monster hp figures up top where you should be all the time when track-driving).

Good luck with the decision!

I think this guy pretty much summed it up. It really depends on if this is going to be a track car that you drive on the street sometimes, or a street car that you drive on the track sometimes...

If you go by the old Corky Bell bible of turbos, it's better to have a larger turbo and run less boost. Why? You aren't working the turbo as hard to generate the boost you need, thus creating less heat and better intake temps.

If you have the money, a larger single turbo run at a lower boost setting is ideal for the track. However, the stock twins are just fine especially if you are just getting started with this car.

allenhah and mahjik laid it out pretty well.

for comparison of a few different setups from track guys (some in Cali), check out the setup of board members rynberg, maxcooper, damian and John Magnusen, Carl Byck (sp?)

The 4 of those guys run the gammut from stock twins (John), BNRs (rynberg), max and damian used both small and large singles. Search on their names and check out their setups and read their threads.

I am setting up my car as an eventual track car but want it to be as reliable as possible for now. I went the route of getting a single turbo (GT35R) and will be running relatively low boost on it for most of time as that will still be a handful... The airpump and all other emission systems on the car are all intact and the goal is to get it to pass inspection. Only two downsides I have seen so far though, time to complete project and very high cost, but I was willing to deal with both of those.

GT35R is your best choice. But .....going single isnt cheap.

If I remember correctly the RX6 allows you to keep the air pump and most of the main requisite emissions BS, while greatly simplifying the turbo control system and not completely murdering the low end. Might be a good route to look at.

I think the big thing comes down to exactly what you mean by road course. If you just want to go out to the local place once a month for one day and have fun, the stock twins + reliability mods + not too much boost (keep heat down) would be great fun and cheap.

If you want to build an all-out track monster than there is no substitute for a single.

RX6 = ?

Some kind of APEXi turbo?

What are some of the specs of that turbo? Compressor/exhaust housing A/R ratio's, etc, etc.

GT35R was probably going to be my turbo of choice. I'm looking for roughly 450rwhp myself. I figure that's reasonable with that turbo, proper fuel, proper cooling, and proper tuning. Shouldn't be a problem.

I can agree with the previous statements regarding low-end torque that only twins are really capable of giving. I say '99 twins are a fantasic way to go for track, or the BNR's. I myself plan to go single, because personally, I think the reduction in engine bay clutter, vacuum lines, and overal predictability is more worth it for street, and mild track/1/4 use.

Specs on the RX-6: Apexi

Basically, it's a ball-bearing turbo that is small enough to still retain some low-end power, not as much lag as some other units, and capable of some big numbers. A friend of mine has a street-ported motor, this turbo, DP, high-flow cat, RB exhaust, and is making 450 bhp (uncorrected) on a rough tune

I use a gt-66 for a mostly track car, very little street use. I only run about 11-13 #'s of boost. Works good for me, as long as I stay above 4500 rpm. At 13 pounds I made 409 rwhp.

so do the 99 spec turbos bolt right up? what's the major differences both in performance and fitment between the 99 and my stockers?

i think i'll stick with a twin setup, mostly because of the low end power. it suits my driving style a little better. i just want to learn more about the 99 spec before i commit.

the 99 spec are essentially the same turbos with better tolerances and thus better performance. they are not a signifigant upgrade. theyre newer and better but not in the sense of the BNR twins or a single. if you want to stay twins you can go get the BNR's and make them parallel and they will act as a single turbo while stil retaining the stock setup.

Isn't the RX6, a b*tch to have it rebuild?

Its virtually a throw away last time I checked, but its based on a relatively reliable design from IHI that has been out there for quite a while. I'd be real leary of running twins on a serious race car due to reliability and the amount of heat all that junk holds in, both things you want to avoid like the plague on a race track. But thats just me, I like to keep my cars simple even if its somewhat of a compromise, its not like this car needs a whole lot of help in the performance dept, if its a bit sluggish on the low end I'll live with it, the wankel is by design a high reving engine.

Single turbo is very peaky. Especially on tighter courses, this will adversely affect your competitive advantage. You won't always be using all your power in road racing, unlike drag racing, and thus you want the flattest powerband possible. Sequential was designed for a course!

All this is fine and geat..... but these people spouting off 450 HP on an RX6 or any other sigle for track use either are HOPING for such numbers or aren't telling the whole story....

(Whole story follows):

Anything higher than stock boost on stock turbos will shorten engine life. Any tuning attempts under boost, can and most likely will stress the engine severely, and sometimes it will break it. People who promisse you an easy 450 RWHP upgrade, are all full of BS, it's a long arguous road, filled with descisions that can cost you your motor.... Example, 1300cc secondaries or 1680 cc secondaries ??? (Do a search on stuck injectors)

Upping the power is a rich mans game, and if you don't have the patience, and the stomach for the nagging of your friends to drop that POS allready.... don't Enter.....

Scorned, yet still in the game... :D

-DC

Hahaha! Well I can certainly handle the hassles of finding the right information on the right parts, tuning, safe practices, practical application, and the monetary progression of upgrading. Heh, I certainly don't care what my friends have to say about what I do with/to my car!

I am a professional mechanic, so being careful and doing things right is my philosophy. BUT, I also recognize that there are members of this community who have more knowledge specifically about rotaries than I do, and I'm willing to concede that though I'm a pro, some of you may know more specifically about these cars than I do.

As for any claim of "an easy ____ HP gain," I generally don't believe it until I see numerous tests showing hard numbers. I'm skeptical of many claims in the automotive world.

do a search on that. there is lots of info about the differences between them. both the bnr and 99 turbos bolt right on.

I regularly track my car (~10 events/year). If I wasn't worried about passing smog and enjoying street driving to the utmost, I would have gone with a GT35R from A-spec. Instead I went with the BNR Stage 3s running sequentially. I just had a tuning session with Steve Kan and will be posting results shortly. As a teaser, I made 308 rwhp at 10 psi with a very conservative tune for our 91 octane.

I am 99.99% of the way to deciding to replace my worn-out stock sequential twins with the A-Spec GT35RS. A-Spec has a short runner manifold that let's you keep the air pump.