Bridged

Im currently building a pp to go into my rx4 coupe. preety much got it sorted whats getting thrown in there but i know there's a few hardcore n/a freaks on here so tell me what im doing wrong

12a small port plates ( nitrided and lapped)

s4 na rotors lightend

3mm carbon apex seals

rx4 eccentric shaft

rx8 stat gears

rx4 housings with around 50mm ports done by Rohan Ambrose (im sure a few you guys have heard of him)

1 piece dowels

machined sump plate (bolts on over the sump to helps stop twisting)

hi volume watter pump (12at i think)

hi volume oil pump

2 60 mm ida throtle bodys with 4 injectors (not sure what size injectors to use yet?)

micro tech digi 1 ( its not the best but its cheap and i hope it is up to the job)

thats about all i can think of rite now so wat do you guys think, anything i've missed?

Im looking for some fairly respectible numbers out of this What should i be expecting??

kahren

s4 na rotors lightened? they will weight what, as much as stock s5 rotors?

why not lighten s5 rotors or use them stock. or go for the renesis rotors and machine them for the old apex seals?

Bridged

they shoud weigh a lil less than standard s5 rotors and they have the higher comp therfore a bit more midrange. Rx8 rotors are too much stuffing around to fit decent seals plus iv'e heard a few poeple saying there not much good in pp's because of the shape of the "bathtub" and s5 rotors will actually make more power

The Ultimate 7

I'm confused! You are using lightened S4 NA rotors but yet you keep praising the S5 ones? S5 rotors are 9:7 while the S4 are 9:4. S5 rotors are already lighter than the S4 ones. So again why did you go with the lower compression heavier S4 rotors as a starting point?

sidewinderx7

s4 rotors are great for high boost engines... but yeah, pp na, I'd stick with the s5 na rotors

kahren

this is a first time that i hear that rx8 rotor will make less power then s5 ones

there is a reason compression went up on the renesis rotors and them getting ligher then s5 ones, and its not to loose power.

Bridged

Im not realy an expert on what motor had what spec rotors. first i was told to use s5 low comp rotors which i thought was strange then the guy thats putting it together told me that he had a chat to Rohan Ambrose and he told him that s4 were the go. Would it make much diference on whitch rotors i use?



About the rx8 rotors

I believe the combustion chamber is such a bad shape that it may be detrimental to performance when using the rotors in an earlier engine. Sure they work well in the RENESIS engine but that doesn't mean they will work well in other applications, the RENESIS has a lot of different characteristics including 2 psi of manifold pressure due to the intake design. This in itself could make up for the poor combustion chamber shape. The RENESIS was designed for, among other things, emissions and fuel economy. Higher compression ratios help with these points but doesn't necessarily mean higher hp (in this case anyway I think).



Points to consider:

1. Squish is improved.

2. Flame speed may be reduced due to shallower combustion chamber.

3. Engines ability to draw in intake charge is reduced due to smaller chamber volume.



Please correct me if I am wrong, this is how we learn.



I know of a person who lost 30 odd hp when they changed from S5 n/a rotors (9.7:1) to RENESIS rotors. They are also running methanol which ofcourse is a slower burning fuel and I believe would be more succeptable to poor combustion chamber shape.



I have not found anyone who can honestly say they are making more power with RENESIS rotors than with earlier types, most seem to be making less hp. S5 rotors definately work well and are widely used so why don't the RENESIS rotors with only .3 difference in compression??

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Ideas anyone or someone know someone making more hp?



Using rx8 rotors in 13pp (factory housing) altronic ecu 55 mm TB couldnt make more than 290 FHP. Tried different exhaust set ups etc. Rebuilt using hi compression s5 rotor all else the same and tuned extra 85 FHP.

heretic

I don't understand why Series 4 rotors would be "the way to go". Nor for that matter why anyone would suggest intentionally using the low compression rotors in a naturally-aspirated engine build.



Then again, I also don't see the point of taking new rotors and potentially ruining them by machining for 3mm seals. Or the point of a sump plate to "prevent twisting", or one piece dowels.





It almost sounds as if the recommendations were made by a shop that exclusively does turbocharged engines, and really knows how to work preconceptions.

PDF

I suggest you base your engine on a s4/5 block, that way you can use the larger oil pump and 13b turbo housings which can be exhaust ported without removing the sleeve. RX4 type housings require removal of the sleeve(restrictive) which I feel is not ideal for gas flow. If you already have the rotors s4 n/a will be fine but if you don't, get s5 n/a as they are a proven item. Slotting to 3mm won't be necessary unless the 2mm apex slots are worn. Factory dowels will be fine unless you plan to use a turbo and a thick sump plate won't be needed although it wouldn't hurt (except maybe your wallet). Gilmer drives or something similar that underdrive the waterpump and alternator are a good idea. 50-55mm IDA style throttle body will be plenty. I wouldn't use a digi 1, I'd get a newer Haltech or Microtechs all motor ecu when its released in a month or so.

Bridged

thanks guys i'll take some of that on board although a few things are set now like the housings, rotors and 3mm seals. I ptobably shoud have done a bit more research instead of listening to one or two poeple that i thought were in the know. Im using the digi 1 because im on a pretty tight budget (will probably upgrade later). What are your thought on how to shut it up for the street. I was thinking twin 2 1/4 system primarys running to just before the diff then into 1 over the diff through a fairly large mufller?