I am planning to rebuild my S4 Turbo motor because im interensted in a large streetport. Im looking at some possible options, as into using S4 N/A rotors instead of my S4 Turbo rotors. I been doing a little research with the search engine... I discovered that I need the counter weights and a flywheel, the swap would yield a 0.9 ratio increase, also I know that I will NOT be able to run the same boost with the stock turbo I have, for obvious detonation reasons.

My question is that a possible upgrade that is worth the trouble. I dont use my car as a daily driver. Has anyone built this, or at least had this done to their 7? I have been searchin for this for about 3 days and the only evidence I can find is from 2002. Maybe Im not doing a good enough search.

Im pretty well versed in tuning. I seeking hard evidence and expirience in the mod. Thanks for lookin

 

You do not need the counterweights and flywheel if you are keeping it all S4. The imbalance is the same.

Most people use 9.7 rotors, because they are starting with 13B-RE, -REW, or 20B engines, for the same reasoning. That, and if one is buying rotors anyway, the tendency is to take it as far as you can...

 

Thanks...Great! Someone who knows about this. On that note, where there some dangers besides detonation. Also, I hear that using two of the same rotor (ie front & front or rear and rear) you have a greater chance of a balanced motor. Nothing extreme like being able to go above 8.5k, though

 

13Bs do not have "front" and "rear" rotors. Same part.

That said, if using used parts, it's a good practice to put the engine together the same way it came apart - the rotor that was on the front, stays on the front, and the two rotors keep the same orientation relative to each other.

 

it pretty much depends on what your goals are. using the higher compression rotors will likely limit your maximum boost, but it should make for better power all around - relatively speaking. you'll have to go the extra mile to control heat though.

the question about it being "worth the trouble" is totally up to you. however, what engine management, turbo and supporting mods are you planning to use? i'm just trying to get a better picture of your plans.

 

Well I would like to get the most out of my car before I have to use a stand alone. I was looking at maybe a Rtek7 2.1 (I believe), with 720 injectors. And a piggy back later on. I wanted to avoid getting a bigger turbo than stock for now cuz I would like a baseline for tuning for a while before I give it more cfm. Fuel isnt a issue being that I have rewired my pump and use a Walbro 255, and have a regulator. Im still a little uneasy about which rebuild kit to use. I have upgraded to a aluminum radiator. Intercooler is stock until I find a good v-mount. I dont lik the idea of giving my radiator a blocker, lol (had problems with my talon years ago). This is my first rotary, so any advice will be taken seriously.

 

i have a BP TII with 9.7 comp.ratio........running a haltek ek6, 1650 sec. 780 prim, 4 inch thick intercooler.....a few weeks away from actually runnig the car, needs to do exhaust on it still..but i am pretty confident I can run high octane pump...and lower boost and stilll get some decent HP numbers......
i am expecting to run about 14 psi of boost and hoping for a conservative 350 to 400 whp

I am using a Garrett TO4E not a stock turbo..........but i am very stoked about having it runnig in a few weeks or sooo.....


ohhh did i mention its in a MIATA..LOL

2200 lbs of pure excitment..lol

 

i run the 9.4's on several engines under boost,,both petrol and LPG
== no real issues except for need to custom the ignition curve
and so aftermarket ECU is paramount to making it come together

-- and the 9.4 and 8.5 ..2mm apex slot ( s4 ) rotors use the same balance weights as each other ,,
and are much sturdier,, if a little heavier than the weight of the 9.0/9.7 2 mm apex slot rotors
( 3mm internal ribbing,, while the 9.0/9.7 is 2mm )
-----

my current FC engine is-
mild s4T primary,,
s4 6 port endplates,
s4 6 port rotors ( 9.4 ),
turbo oil pump with modded reg ,,
impco 225 LPG mixer
stage 2 highflow turbo
and LTX-8 with 4 x 715 HEC coil packs

 

How big of an adjustment did you have to make to the timing?

 

with 98 RON ( 92 MON ) ,,, beyond 10 psi you took 1 degree out for every psi
( at 10 psi you should have already pulled about 5 degrees from the base 25* )

with the low comp rotors,, those plots beyond 10 psi may have had up to 3 degrees more timing

so,, retarding your stock ECU ( with a defender for the cut )
,, is going to give you that 3 degree buffer at medium boosts you want
-- but is going to rob the off boost and low boost all the time

 

thats about equal to 95 octane here. What are you doing injector wise? Have you run into any other issues with your setup?

 

when it was petrol,, i would use 4 x 550
( low ohms and ring main fuel rail set up )
with 2 x 550 more coming in as a microfueler up top for boost above 12 psi
( LTX with the microfuel out option )( thats in the 6 port rx2 )

the injector selection is always going to be about the needs at max flow,, and not about the initial compressions



now,,in the FC i run propane/ butane from an impco 225 mixer blow through,, and that around 105 RON and another hybrid 6 port
( actually i try and buy just propane at specialist places and its even better )
so i dont have to retard so much now at all!
( in fact i run a fairly normal looking curve as if i have 8.5 rotors ,,bar a little more off boost timing )


personally,, i am a fan of 6 port engines,,
and in relation to using the higher comp 9.4 rotors provided the turbo will always be mildish and boost limited below 1 bar,, i am all for that too!
( in perth,, australia we have one refinery and it pays not to tune at 10/10 with petrol ,, as they sell to a closed market and can get away with some funny **** )

so taking in that above,, and that your consistency and quality a bit more assured you can possibly run just a little more boost or timing than i would put on it here
( personally a little stunned at the boosts you guys have the 9.7 at ,, couldnt do that here !! )