Twin turbo or single turbo????

[Joekont]

Hi guys.

Newby here. I\'m going to be looking seriously for an FD in the next six months so I\'ve started looking around now and doing some homework.
I\'ve noticed that people do a single turbo conversion.. Why?

Surely 2 turbo\'s are better than 1?
Or do you sacrifice low end power for loads more top end power...

Cheers.
Joe

[g11ary]

generally the stock twin set up is good for 350-400 bhp and the single conversion from 350bhp upwards. the twins have arats nest of pipes to maintain and make the car slightly heavier, although the stock twins properly set up are very powerfull and much smoother in operation, not such a kick in the back when they come in, although with good mapping a single would be smooth. Mostly will depend on how much do you want to spend and how moddified do you want the car. Everything in mods comes with a cost. ie money or reliablity.

[20B_boy]

Originally posted by Joekont
Or do you sacrifice low end power for loads more top end power...

Quite the opposite Joe, the stock twin turbos are sequential in operation; ONLY the first turbo gets all the gas to begin with while the car gets hauling, then at a set RPM range the second turbo is spooled and the gas is fed to both turbines after this point (the \'transition\') for the rest of the engine rev range...

Because all exhaust gas is used to spool the first turbo on its own to begin with, the usual lag you get with a turbo charger is reduced. A stock FD RX7 in perfect nick is a JOY to drive (even after driving big singles IMO, its a totally different car especially nice for every day driving as you would imagine), the stock sequential turbos are VERY responsive and smooth in operation, you never feels as though you are waiting for the power delivery.

Bigger turbos are needed for more power, the simplest answer is one of the many single turbo conversions that can be done reasonably cheaply (well, say £5K or so!). You can of course get modified sequential turbos (although the stock exhaust manifold really needs replacing as early as poss I think) or aftermarket non-sequential twin turbos. But for the best compromise of price v simplisticty v power v reliability, a small/medium single turbo conversion is most popular.

HTH,

[Joekont]

ah. I see. I didn\'t know that the turbo\'s were fed gas seperately.
So how would you go about getting 350-400 from the standard turbo\'s then?

Upping boost, better exhaust and better timing I assume.

[20B_boy]

Yeah, the FD is Sequential twin turbo as standard. Only down side is the very complicated control system which consists of loads of solenoids and vacuum pipes that invariably f#ck up sooner or later!

350 FLYWHEEL HP is easily achievable; exhaust and up the boost will get you close.

You really want do ECU, fuel system, intercooler etc FIRST to do it reliably...

400 fly wheel ponies is really approaching mod\'d/after market turbo(s) as the stockers start losing efficiency at not much over stock-ish boost...

[Joekont]

Right.

So If I bought a standard car, how much would it cost me to get upto 400hp @fly then?

Or would it be better to go for a modified one in the first place?

I\'m planning on spending about £15000 on one but I\'d like a late reg with low miles.

[salamanzer]

I would advise a single T-66 - that would get you about 400 rwhp.

You would need to upgrade the injectors - maybe 800/850 pri and 1400 sec and a uprated fuel pump ?

What ECU are you running ?  I would go for a power FC - they are easy to setup and come with base maps.

Also its not that laggy for a single - you should also get a fully divided exhaust housing with will also help the spool times

Regards

Jason