What would you build?
 

Hi,
hypothetically for fun lets say you had a budget of 8,000 usd for the motor in your beloved turbo II. if you could choose which series motor to build up from which would it be? S4 or S5, why? and what would you do?(assuming you are knowledgable and equipped enough not to have to pay someone for labour)

For a Turbo, with that budget I'd personally be using cermat coated S5 housings and S4 Turbo rotors, with 2mm ceramic seals and 10 lb apex seal springs, Extrude honed matched S5 intake.

And probably a Haltech.

so which is a better base motor an s4 or s5 for a full rebuild for about 400 hp

I'd go full cermet (housings, end & intermediate plates, rotors) ceramic apex seals, extended street port, CLR rotors (scalloped S5), balanced internals, type 2 stat gears, race bearings, re-jetted e-shaft... have I gone over budget yet? :)

Does it matter which motor i start with or are all the parts mix and matchable? like what about the 5th and 6th ports? or oil injection pump etc. I have 20,000 to build a race car and im not sure if i should buy an s4 tII or s5 TII to start with or if it even matters? please dont flame. i know alot about rotaries but not rx-7's inparticular

5th and 6th ports are on non-turbo models. If you're building a turboII then you don't need to worry about these.

I'd start with an S5 motor. I'd probably use an S4 LIM, or full S4 manifold if I needed a lot of flow (it flows more than S5, but doesn't have VDI, so I'd only use the UIM if flow was crucial). S5 rotors were lighter, and higher comp. If you mix and match internals you may want to look into getting it balanced, and make sure you have all the right counterweights. It depends on what's important to you as well. For example, pretend that between the S4 and S5 Metering Oil Pump one suited your needs better (reliability vs function, etc) then it would be a factor, but for others who premix it wouldn't. Instead of asking which is better in general (not that it's a bad question) you need to look at all the differences, and ask questions about specific differences in relation to a specific need.

oh i feel dumb i thought all s4's had 5th and 6th ports :) so ive tried searching but i cant find a clear answer, what exactly is thel difference between the s4 and s5 motors. for example, i know that one has mechanical oil injection and the other has electronic which, correct me if im wrong, can't be readily changed on either motor because it is ecu controlled,and expensive? I also know the s5 has higher compression, but is this beacause the rotors are different or is it beacause of the housings are differnet or both? can you mix and match s4 housing and s5 rotor or vise versa? is there anything else between the motors that cant be easily changed during a rebuild? and which of these things, of the things that cant be changed, is better?

VDI and aux ports are not found on Turbo motors

i started writing that last reply before you posted kontakt. If i were to use premix would i just disable the oil metering system? does premix affect the injectors, which of the oil injection methods is more reliable? which is more effeecrive? sorry if my ?'s sound dumb, everything i know about these systems on the mazdas ive learned today. i do know alot of theory behind rotary engines, i just never knew how mazda actually implemented the necassary systems. im not sure what vdi is but ill look it up in the abbr. sect.

I would say that the s4 oil metering system is more reliable on a stock car, as when the s5 goes bad it tends to take the ECU with it (I've lost 2 ecus to this problem).

However, if you go standalone EMS, personally I would just premix. If not, use the s4 oil metering pump, as it is mechanically driven from the throttle body and would be one less thing to tune for.

Also, if you're mixing and matching engine parts, the OMP must match the same series' front cover... so if you use an s4 OMP, you need an s4 front cover. Hope this helps.

ya it does thanks for the info!

are there any other differences between s4 and s5, besides rotor weight, compression, oil injection, and intake manifold? i.e. redline, ecu, etc. and can someone confirm that vdi didnt come on turbos?

icemark is the best. if he says it. its right

VDI did not come on turbos, I got to talking about the N/A motor I'd build and it slipped out (mostly the same as the turbo motor i'd build internally, just with NA rotors and such). If you need verification of anything Icemark says, just double check that Icemark is spelled correctly. If it is indeed him, it is right...

Edit: Damn you K-Rok

Icemark teh PWNS all...

My next project may be an s5 turbo block, rediculous streetport, CLR scalloped rotors, dual 38 weber downdraft carbs....in an FB....

s5 cerment coated irons
s5 cerment coated housings
ceramic apex seals
s5 LIM
FD UIM and TB
MEGA BRidge port
Haltech E.11 v.2
steve kahn tune
strengthined racing beat stationary gears
stage 2 bearings

and a case of beer

well atleast one of those are going to happen on my list the cerment rotor housings

S5 N/A redline was upped to 8k, but not turbo. The ECUs and wiring harnesses are different as well. Housings are pretty much the same. I believe the S5 T2 rear iron had additional reinforcement. As stated the front cover must match the OMP. To "go premix" which IMHO is the way to go, you remove the OMP, and plug the holes for the injectors. The OMP sorta drips oil onto the apex seals, but one spot right in the middle. Pre-mix coats anything that the gas touches (everything). Pre-mix also reduces carbon deposits from the oils being cleaner burning.

Hope this helps.

oh and a t51 r