okay, im not wanting to start a debate here. i want to just state what i feel, but without ever riding in a single FD. i have a twin FD with almost all the bolt ons. i dont have an intercooler, but after installing the MP i noticed i lost a **** load of bottom end. i know i might be able to get some back with tuning, but who really knows. before the MP(cat era) i was getting boost by like 2200 rpm's and full boost well under 3K. it was pulling too. after the MP install i noticed i was making boost by about the same and had "full" boost by 3K but it still didnt start pulling. wasnt till about 3500 rpm's that it started the kick. its not that free flowing as i have the new RB dual tip. now my question. when people compare the twins to singles how are they doing this. is it stock twins from factory nothing touched on car, or is it a modded twin rx7 with all bolt ons? i hear of fast spooling single(35/40), and high power(t78) but that is in another thread. dont hijack this one with those. i really wouldnt mind any single if they spool basically at the same rate as my twins with bolt ons. i hope all this made sense, but my car just seems so slow, and i wanted something to talk about tongiht
kris

 

IMO -- the stock twins are unreliable, hard to fix and are only designed for a stock RX-7. People(me included) start getting all kinds of crazy efects that don't make sence when they start adding hi-flow bolt ons + boost spike, boost creep and 40ft of vac line. The stock twins are not worth the time and agrivation. Sell all your stock crap and get a nice single. I too wanted a turbo that spools like a stock twin so I got a RX6 kit. This kit spools the fastest but it's max HP is 450. Now the ultimate is the GT34/40 spools a little bit slower than the RX6 but can give you 500+ hp and a better top end so I'm told. People who love lag and drag racing buy the big turbos and sell their small ones to buy them so you'll be seeing RX6 kit for sale online now and again at half what they are new. I'm sure there are some die hards out there who keep the stock twins and wouldn't have it any other way, but the fact is that they are really small and just cannot flow enough air for anything (reliable) over 350rwhp. I could go on and on with reasons why i hate the stock twins but then I'd be here all night.

GO SINGLE and never look back !!!

 

Kris,

Let me know if you want to meet up some weekend, I will show you my car and my set up. I am fully spooled by around 2500-2600. I have a BLITZ SMIC, injectors, and Fuel pump, very, very highflowing Rx7fashion cold air box with 2 ram air intakes. Other than that we are probably similar. What intake do you have?

My car does not feel like it lost any low end, I have dyno before and after with the MP and Highflow cat and it shows that I do have good low end. Anyway this is not an answer to your question, but I think something is wrong with your setup.

you will not get any single that spools as fast as the twins, its not possible. The very small singles like the T04 or the APEXI 6 may spool quicker than the other singles, but not as good as stock.

 

Very true, I have a TO4E and while it spools quite fast it is not nearly as responsive on the low end as the twins were. I expected this and it doesn't bother me, the lag is really only noticeable when starting from a stop.. or if you are in a low gear (1st or 2nd). In the higher gears the thing spools quite fast, even at 3000RPM in fifth on the freeway I can stab the gas (not even flooring it) and get 10psi almost instantly. But, you don't feel the real kick in the pants from the turbo until you swing past 4000-4500rpm. I opted for the TO4 over the RX6 because of the overhaul issues on the RX6, and I prefer HKS products over Apexi most of the time. HTH..

 

You're definitely going to gain around 30+ rwhp with a midpipe over a high-flo cat but that's peak hp (after 6K rpms) A hi-flo cat will give you better low-midrange response and torque. I went from a midpipe to a hi-flo cat and the car just felt much faster down low. You're not going to pull big dyno numbers with a HF cat but I managed 370 rwhp at 15 psi with a cat.

The twins can be a pain in the *** but IMO there's nothing like them. Getting full boost in any gear under 3K rpms translates into a lot of fun and a more streetable car. I know everyone has their definition as "streetable" but driving a T78 at the same boost level seems like you're waiting for boost and then a insane amount of power unleashes and the car goes sideways. Have to admit that single FDs are a blast on the highway but FDs with sequential twins are more fun to drive overall

Just my 2c

 

i agree, i got my FD running on the factory twins and i plan to keep it that way. My friend is pushing an easy 400+hp running on the stock twins, but i mean ,, whatever floats your boat right?!

 

actually the stock twin are very reliable, but only on a stock car! but single personally is always better and more efficent!

 

It's a very personal thing, basically. Some like twins, some like singles...that's what makes the world go round. For what it's worth, I swapped my twins for an RX6 and I've never looked back.

The other thing I was just thinking, is that "lag" is ambiguous. You have lag due to RPM, ie a single may not pull below 3000, and then you have lag from going from neutral throttle to full at 5000. As far as the low rpm lag, I'm actually quite sure based on my racing experience that I have more power under 3000 with my single than I did with my twins because they are flowing so much better that I allow the engine to make more power even though they aren't boosting. Again, that is based on seat of the pants racing and not any true numbers, so take it with a grain of salt...just my theory.

As far as the lag from off to on throttle, I can't tell that there is ANY difference. The RX6 builds boost damn fast when there's sufficient exhaust flow. Not trying to turn this into a RX6 debate, it's just that it's the only single I have personal experience with.

My final argument for the single in a race environment is the total elimination of the transition spike. That used to get me all the time when autocrossing. So hard to time backpeddling off the gas right at the spike and then get back in it perfectly without losing boost.

So to get back to your question, that's my take on things from going from a fairly heavily modded twin system (street-port, intake, hi-flow, catback, FMIC, PFC @ 13lbs), to swapping in a single. HTH.....

 

This is Flywheel horsepower right? What boost level? If you're guessing or taking his word that he has 400+Wheel horsepower based on butt dyno you're probably both a bit optimistic. IMO

 

Using the dyno plots at www.catenet.net , I made significantly more power than any single tested until about 3200 rpm. I made more power than the big singles until 4000 rpm. After that, of course, it's no contest.

Note that my only mods were downpipe and cat-back at the stock 10 psi, while all of the singles are, obviously, heavily modded and most were running 15 psi +.

Just an observation...

 

For me the whole Twins vs Single wasnt about the power increase. For me it was a remedy for my constant boost inconsistancies. Some days I would get 13 psi others I wouldnt get it on transition and then I would. Always tracking down a boost problem. Even goin NON-Seq didnt cure issues with my Y-pipe and other problematic areas for leaks. The aging system is even more problematic as time goes on and as you turn up the boost. You can get good power from the twins. Enough to really kick some ***. Unless you live near a good 3rd gen rotary tech your car will never be as consistant as a single turbo 3rd gen. The biggest difference I saw with building boost with my single vs my twins wasnt where in the RPMS I was making it but how much faster it builds once it starts to spool. I go from 2psi to 16 psi at a snap of your fingers. Its probably due to the ball bearing turbo but it makes up for any lag. But it is a bit disturbing if you have the boost set high because you tend to have unexpected wheel spin thats impossible to modulate. The twins spooled up more evenly. I would imagine any classic bearing style single would also spool like that. My single makes alot less heat because its run more in its efficiancy range and doesnt create as much heat as the twins. Performance isnt the only reason to switch. And as far as cost alone goesnt isnt worth just the extra 50 to 75 hp vs the twins.