Very foreshadowing statement in relation to the FD.

 

After driving on the twins (seq. and non. seq 370rwhp), a T04S and T88 singles 400rwhp and around 500+rwhp for the 2 latter, I would have to agree with this statement. Each application varies in its abilities, and lag is an issue with the more powerful singles, but it depends on what you want out of the car. I personally plan on going with the T04S once the twins are shot, but I could easily see valid reasons for wanting to stay with the twins.

 

Wow. It doesnt take much to turn any thread into a "single vs. twin" thread. Does it?
Cant we all agree that the driving experience in a FD is a very subjective thing and its the variety and options we have for our powerplants that ad icing onto an already tasty cake?
Hell, what am I talking about? That'll never happen, that's why this forums so popular. There's no such thing as majority rule.
We can all agree that it comes down to money. If I put a single on mine, I'll be payin 4 parts labor and money lost in havin my daily driver down and the whole CA smog issue.
I do know I like answering "yes" to the question "is your car a twin turbo", but , yeah, that only impresses the non-rx7 public who then ask "how many cylinders does it have?"

 

There's nothing really preventing a single turbo from spooling quickly. It's not like having the stock secondary turbo makes the stock primary turbo spool up any quicker. The thing is, both of the stock turbos are nice and small which makes the primary spool quickly and the addition of the secondary allows a good amount of flow at higher rpm. So to replace them you generally can't find a turbo that will do both.

Here's an example. The Garrett GT28RS (a.k.a. "disco potato) is becoming very popular among the smaller displacement piston engine crowds, mainly due to SCC using it on their 240SX project car. That car which has a stock internal SR20DET and the typical upgraded intake, intercooler, downpipe and exhaust, makes 274 whp at 15 psi with full boost reached by 3000 rpm. The SR runs out of steam sooner than the 13b-REW so presumably that same turbo in an FD would be capable of about 300 whp at 15 psi of boost. So, a GT28RS would be a good choice if that's all the power you ever want to make and you want a less complex setup than the stock twins while maintaining their quick spoolup. It does a good impersonation of the primary turbo's ability to spool quickly while at the same time it can flow enough air to actually be used by itself. However it still cannot match the flow capacity of both the stock turbos working in concert.

If you want to get any more top-end flow out of a single turbo than what the GT28RS can do, you sacrifice some of its ability to spool as quickly as the stock twins. Granted it won't necessarily be "laggy" by the common definition but it will not build boost as instantaneously as the twins.

 

I like my twins. No problems.....yet. Sure the singles are better for straight line racing, when you don't use any low RPM's. The twins are just a little more "user friendly" when they are working right. I won't be changing anytime soon.

 

i wouldnt even go as far as that. . . single turbo is the way!!!! my to4e spools up just as quickly as my stockers did. drag or street. . . single is the king!!!

paul

btw d1import2nr, who are you? haha. . . i recently met a guy named don w/a red touring model. . . cant remember his screen name for my life. . . is this don? if not. . . you need to come out next time we all meet up.

paul

 

it's still non sequential..is it not?? i'm sure ppl thought of going twin non-sequential turbos per manifold on the z32 but there just isn't enuff space for four turbos in the infamous cramped z32 engine bay..

i think we all get the idea now.. twin sequentials has their place but singles win most of the time..

 

Stock sequentials were great. '99 J-spec twins are even better...boost down low @ 2800 rpm, no waiting. Love not having to make a downshift to accelerate on the interstate...just mash the gas in top gear, and away you go '99 J-specs are easily capable of 15 psi boost with spikes up to 16-17 psi...and yes I'm plenty happy with 350 rwhp

 

i have a 240sx (yeah..not a rotary) but i'll be happy with 250hp to the wheels.. who really needs a 500hp daily driver??

 

Seeing as FDs are capable of 375 whp no problem on the stock turbos, people always aspire to make more.

 

with great tuning.

 

Those turbos in that custom kit they are selling (2 ballbearing T28's) are off of the S14 240SX SR20DET engines. My friends S14 is pretty fast on just one of those, they are very good quality garret turbos. Very nice units, and this is what I think I am going to go with when I decide to upgrade.

 

it's too bad the 2 is more than 1 theory doesn't hold for the twin turbos.

 

Hah, yep.

It all comes down to CFM and response. Smaller highly-responsive turbos with low CFM flow-rates won't hold a candle to larger less-responsive turbos with high CFM rates.

I think efini7 is also forgetting that adding 8 turbos to the car requires enough exhaust pressure to spool them all up.

 

hehe..15 and still learning

 

Wow, when I started this threa I didn't think it'd hat up this much. Its great to know that theres such a big rotary community. I guess for now, Ill stick with my stockers (try to squeeze as much hp possible out of them......safely) but when I blow them (hopefully not TOO soon) I will consider both sides, and will DEFINITELY have to ride in someones sigle turbo fd before I make my final decision. Why isn't upgrading the twins such a popular option?

 

Because it's like upgrading a car to larger drum brakes - why bother? We have disc brakes now.

 

341.1 rear-wheel-hp @6500 rpm; 281.1 lb.ft torque @5750 rpm, @ 14.6 psi (after multiple dyno runs with lots of heatsoak).

Fuel was a mixture of 110 leaded race gas, and 94 pump gas, resulting in 102 overall octane. Air-fuel ratios were 10.9-ish.

The dyno plot of my J-spec twins and mild-street port KDR motor shows that my motor/turbos are set up for street driving. Usable torque ranged from 200 to 281 lb.ft from 2800 to 7000 rpm (yes the torque band is over 4000 rpms broad!)

Dyno numbers are one thing, but the seat-of-the pants is another. Wow. No need to downshift most of the time. Just squeeze down the loud pedal, and away you go!

 

I think you're oversimplifying how hard it is for stock twins and motor to make 375 rwhp!!

 

I just bought a set of 99twins. I had an Apexi single in my last FD and loved the simplicity of the system. However, if you are able to delete your,(double throttle solenoid,EGR solenoid,Fuel pressure solenoid,both solenoids for the air pump system/air control valve. etc..) you lose 5 of the solenoids on the rack,AKA: the rats nest. Once this is done the twin system is actually simple to diagnose. IMO

 

Well yeah, probably.

I guess the point is that if the stock twins can put down that much, people will want to upgrade to something that is capable of exceeding that number by a fair amount. And to do that with one turbo it simply will not respond to throttle input as quickly as the stock eensy-weensy primary turbo is able to do.

 

Spoken like someone who has never rode in a single turbo FD.

I'd like to know how "wastegates decrease turbo lag" since wastegates have ABSOLUTELY nothing to do how a turbo spools

 

Of the five you listed, the DTC is the only control solenoid that would affect sequential turbo operation. You wouldn't need to diagnose sequential turbo problems if you have an Apexi single turbo would you?

 

Yeah, I don't think I'd go single. In looking at my dyno plot (99 J-spec twins/streetport motor), I have 200 lb.ft torque starting @ 2700 rpm. Torque peaks to 281 lb.ft, @ 5750 rpm, and drops down to 260 lb.ft @ 7000 rpm. I doubt a single turbo FD will have that broad, and relatively flat (and thus controllable) torque/power band. IMHO, shooting for peak hp isn't necessarily the ultimate goal in tuning for speed on a road course or drag strip. Afterall you still gotta hookup. What good is 500 peak hp, if all you do spin the tires? Well I guess for exhibition, it's cool, but not very effective for ETs or low laptimes LOL

 

hey what's wrong with civic. it gives good milage which is good b/c my t78 only gets about 14-15 miles a gallon.