gear_grinder

iTrader: (4)

high, eventualy with in 2008 i plan on rebuilding my s4 trubo motor. i was wondering what should be done to make improvements for a turbo street car over the stock design when i rebuild it?
I'm planing on running a .60 trubo at around 15psi after the brake in. i was thinking about using s4 N/A rotors because i am only going to boost a max of 15psi and with the 9.4 to 1 comp. it would help the car down low and help with its steetiblity.
For the parts I plan on using an atkins rebuild kit w/ cryo treated apex seals, buying new rotor housings (yes i know it will be about $1000 for two), and new vac lines and other misc things.
i would like to know what other people think of this setup, if i need other things i have over looked, any problems that might occur with the higher comp rotors, and if anyone has run this setup with any sucsess.

thank you.

Captain Jean-Luc Picard

clean or replace fuel injectors (you'll need larger secondaries anyway unless you are talking about a hybrid stock turbo), fuel filter/strainer, pulsation damper replace or eliminate.

I would not really recommend high comp rotors for that boost level on a larger than stock turbo, it is hard enough for most people to keep stock low compression engines in one piece once modded, no use in making it more challenging unless you really know what you are doing. Not to say that it couldn't be done, though, I've run several such setups.

You might also consider using a reinforced s5 rear iron (not all s5's are reinforced, though) for your build, as the s4's are a little weak and can be broken at fairly low power levels (300 and up) if everything is not perfect with the tune.

cptpain

iTrader: (1)

get a stock mazda rebuild kit instead of atkins. i;ve seen several motors prematurely fail with atkins parts, most of them running just atkins' apex seals.

run either S5 TII rotors or get used FD rotors.

you're not going to like how hard its going to be to keep a hi-comp turbo rotary running in good shape with 15psi on a turbo that flows more than stock CFM.

you also dont mention any porting so if you keep stock ports you're gonna have good streetability. a good mild streetport will do good too

gear_grinder

iTrader: (4)

what would be some down falls to the higher comp rotors? other then getting a little unyeildly at high boost level (25psi+) to tune I havent heard any reason y not to use them. i have head that it would give me better down low power and better for driving in trafic.

i planed on doing kindof a 60k tune up after the rebuild as well. it is the same car in my siginature so it has bigger/new injectors, and i replaced the fuel filter about 6 months ago but i planed on doing that anywho, i have only run premeum from high end stations (no admiral/cheap gas) so i think the impuritys in the system will be fairly low as it is. i have banjo bolt replaced the pd, and am getting a adjusible FPR some time this winter. i also planed on getting a new oil chain because i'm preaty sure that it will be too loose as well as berings for the end of the engine so my end play will be minimum.

O yes and thankyou for the tip on the s5 housing. what is every thing i need to do to swap one and how can i tell if its reinforced?

i am going to keep my ports completly stock for relibility, duribility, and practicality.

Josh13B

At least get a port polish, it will help with airflow.

If I went to the trouble of getting a rebuild, i'd get a streetport or an extended port while i was at it. There is little if no effect on drivability and you can get up to 50hp on the motor. They increase airflow and widen the rev range, but its totally up to you...

gear_grinder

iTrader: (4)

i think i'm going to stay stock so the motor will stay as durible as posible, less ware and tear on the side and apex seals.

Captain Jean-Luc Picard

Those are certainly some unusual ideas for engine build. IT seems like you are set on what you want so I am not sure why you are even here asking for advice if you arent going to listen to that which you are given.

ANyway, most tuners won't want to go higher than 13psi on pump gas with low comp rotors, and will get even more nervous when you tell them you have NA rotors. Again, it can be done, but again, most people have a hard enough time getting these setups to hold together in the long term with the low compression rotors, so it's not like you need any additional challenge with a modded turbo rotary.

And I think it is ludicrous not to do any sort of porting at all. At least do a mild streetport and clean up the castings a bit. Dont do a mirror finish or anything, just finish off with a stone which is smoother finish than stock but rougher than a sand roll or polishing bit.

I have built and driven several high and low compression turbo engines. I could build one of each and you would not be able to tell them apart from a drive around the neighborhood. There is a small difference in mpg and low end, but very minute. You see more difference in s4 versus s5 rotors than you do in high and low compression, as far as takeoff/low end.

gear_grinder

iTrader: (4)

well i really wanted to know if there was going to be any "brick walls" for this idea, but i'm still a ways off from actualy doing any over hauling, so its not a big deal right now. i know atleast i want to get a s5 rear housing. how can i tell if its strengthined or not??

Captain Jean-Luc Picard

http://www.rotaryresurrection.com/2n...ron_break.html

gear_grinder

iTrader: (4)

well now i know that i will most defenatly be using a s5 rear housing, thanyou.

Aaron Cake

iTrader: (1)

I'd suggest moving to a real standalone instead of the RTek. This way you can replace the 20 year old wiring harness and have full control over the engine. Necessary if you want to safely run the high compression rotors.

A "polish" on the ports is almost useless.