I am doing a rebuild and one of my rotors are bad on my S5 motor. I was pushing 17psi. Is running S4 rotors a good idea if I plan on boosting high? I know that the S4 rotors have .5 lower compression but also weigh heavier than the S5. So I don't know which would make the most power. I was also planning on running water injection so I don't know if it is neccessary to run the lower compression. Please help as I need to order the rotors as soon as possible.

 

just stay with the s5 rotor and go 3mm, i was thinking of doing the same thing going with the s4, but u have change some parts like flywheel and other ****.

 

For higher boost levels run S4.

 

Ok, I have already decided to go with the 2mm that seal better. I plan on using the water injection to prevent detonation so I would rather use 2mm because they seal a lot better than the 3mm.

As for the counter weights, I have an S4 TII motor on the side which I can use the rotors and the counter weights so that's not a problem.

So, has anyone had any real good whp numbers off S4 rotors? I know you can boost higher, but there is the fact that it is heavier and the fact that when its not fully boosting the lower compression will cause less power on the bottom end. I guess its a give-and-take thing but if there are solid numbers to show the S4 rotors really help and at what boost level, then I can make a good decision. Is there anyone running the S4's?

 

The weight difference is a matter of a pound or two, check http://www.mazdatrix.com for details. Search the dyno and time slip section and see what people use for their rotor choices and then their power.

Are you running a standalone?

Good luck!

 

Yes, I'm running an Autronic SM2 standalone with a Greddy Td06 and 550/1600cc injectors. So I've read the dyno section and there isn't anyone saying if they're running lower compression rotors but there is one where a guy is running 9.7:1 compression rotors @25 psi w/ stock ports and is pushing over 500hp. I'm guessing that means the higher might be better as long as its tuned correctly.

 

A ping is a ping, if it is big enough it will take out a 3mm or a 2mm apex seal. I would go with the s4 rotors and 2mm apex seals. Just get the thing tuned right. There have been several people that have run high boost with the 2mm's.

 

Who's building / tuning your car???


-Ted

 

I've built the motor and did all the wrenching and have a shop tuning the autronics. I think I've decided to go with the S5 rotors. I've put in my order to Mazdatrix for a new one this morning. I figure I'll be pretty safe with the water injection. Plus, this new rebuild I re-ported everything so with new stuff, the water injection, bigger ports, and when I turn up the boost, I should have some good numbers. After the shop tuned my car, I was pushing 315whp @12psi. They think my Td06 exhaust side is restricting me from more power because when I raised the boost, my curve got way better but top end power wasn't gained. I now don't know what turbo to go with. Maybe just upgrade to a Td07? I have no idea...

 

Izumi?


-Ted

 

And don't forget, less boost on higher compression = same power as more boost on lower. It's all about the tuning!

 

You bought 1 rotor? So you're going to have one new one and one used? Isn't that...well bad?

 

Why would it be bad? As long as they were the same series and stamped the same, the rotors new or used shouldn't matter much, since it's all of the peices that go on them that spec, the rotor itself just has to keep it's grooves in spec, and I don't think if the other one is still good those will make a very big difference.

 

why dont you go all rx8 internals?or are you on a buget?
rx8 internals are lighter and lower comp

 

wtf have you been smoking? RX8 is 10:1, last I checked that's a bit higher!

 

What for???
Even though you got the compression ratios all mixed up, what does RX-8 rotors offer you that's superior?
Remember, this is a TURBO motor...


-Ted

 

oppss my bad ment to say higher
alot of high hp turbo cars in nz & aus are using rx8 rotors and internals.results speek for themselfs

 

The only results I've seen of RX8 rotors being dyno'd vs the nearest other option (S5 N/A) showed the RX8 rotors about 3hp less. Results can't speak if nobody has them!

 

im only going on wot ive seen and wot ive been told by well known rotary engine builders you have outher results and thats fine .but i will be using rx8 internals in my next engine build

 

There is a device the detects ping and retards timing. I've seen a 3rd gen using it, but I dont know what the general concensus is on using them.

 

Oh, so have you done it yourself?
Or your only relation to these "other" people is the fact that you live in the same country as them?

So how many of them are street cars?
How many of them use "pump gas"?
What octane are they running?
How much boost are they running?
What kinda computer are they running?
How much did it cost to build their cars?


-Ted

 

Hmmm...the Japan tuners LIKE to use 8.5:1 rotors with high boost.
Go find out why...
I'll give you a big hint...DENT.


-Ted

 

no i havent done it myself .
im only going on what ive been told mabe ive been misslead?
mabe they arnt running rx8 internals?

 

No not Izumi. I bought the system from him but he didn't wanna do the tuning as he's never done a rotary before. I had Gary at Sonics do the tuning. He's done a 13b in an SA earlier.

Ah, just realized you're from Hawaii! You must be the infamous Ted K.? If you are, I've heard you're name around. Its hard as no one around here really knows about rotaries, especially the shops. Do you still do the services you offer on your site? Oh, do you know of any machine shops that can lap the side housing?

 

the reason the factory and almost everyone loads up a turbo with lower compression is to avoid having to get higher octane fuels. If you've got access to avgas or race fuel the higher compression can only benefit you as far as I know. But i've never done turbos, only know what people say on here.

Something interesting I found in car&driver recently was that the ford cobalt has a 10:1 compression ratio running a factory turbo and accepts 87 octane gas. If anyone can explain that one, please let me know.