rxturbo

Hello there,

Can anyone explain why mazda have made the side seal clearance between the side seals and the corner seals so big, I mean even with the longest side seal that mazda has to offer for the rx8 rotors it still has a 10 thou gap and thats the smallest. It does come down to 8 thou when you push the seals down into the groove but still this is way to big. I can only imagine with the side seals now running past an exhaust port that because of the exhaust temps that mazda are allowing them to grow. Which might explain why Ive heard a lot of them flooding when they are cold and the seals havent grown then.

JCC

Hi, I can't offer a better theory than yours - picking up heat from the side exhaust ports. Here is a Mazda diagram of the seals and ports.

rxturbo

yeah i would say that mazda have put in the blow-by seal or cut off seal to help stop exhaust gases from entering the intake port when the rotor is on TDC like your diagram, but say if you are using rx8 rotor in a normal motor say 13b then you dont need them. so Iam wondering if Mazda Factory Race is going to offer longer side seals for there race cars to help close up this huge gap.

rotarygod

Where did you hear the gap was that big?

rxturbo

Where did we hear about it!

well we didn't we found it

Here at Selectmaz we have been working on rx8 motors and mainly rotating assembly ie rotors gears eccectric shafts stat gears for use in our race motors. we have built race motors with rx8 guts because of the higher comp but mainly because they rev to 9000 factory, thats got to say something good about these new design gear profile they are using. We do rx8 race rotors that have been clearanced and balanced along with the shaft using MFR comp bearings and also we can groove the apex seal grooves to 3mm and also deeper to suit other seals like the 1 piece and 2 piece twin spring ceramic seal that we sell here. We are the aust dealer for these new ceramic seals. We also do this because if running a bridge ported motor than because of the small height of the RX8 seals(4mm) then the assitance piece would simply fall into the port were the Earlier 8mm seals are held in by the bridges eyebrow. We have researched and developed these motors for high performance racing applications and along this R&D we have found the shocking side seal clearance, we are overcoming this problem but we still need to know why they have it in the first place.

Thanks

JCC

One problem at high rpm may be that the side seal tends to flutter from inertia and gas pressure like with too heavy a top ring on a piston. Making the side seal a little leaky could stop the flutter.

86rx7

rxturbo, what side plates with the rx8 stat gear swap into? im assuming 3rd gen only...?

rxturbo

The stat gears will fit into Rx4 13b ser 4,5,6 13b and 12a turbo as well as rx7 12a, you do have to use ser6 spacers and needle bearings on the front of the crank and the rx8 front bolt is now bigger, 18mm x 1.5 thread were all other motors are 16mm x 1.5 but. The rx8 rotor, gears and eccentric shaft still work in the these motors, We even have a client who has got a 13B pp and has put RX8 rotors, gears and shaft and the factory seal for rx8 into it and has had wonderful result, he revs it to 10000rpm all the time and its pulls so much harder and because the rx8 apex seals are smaller in height hence lighter they can handle the revs, now we are going to try this combo in a 20b pp, I cant wait for the results. Its mainly the extra torque you pick up thats impressive and the whole set-up is cheaper to do.....

rxturbo

JCC we have contacted Mazdaspeed whom there Engineer is contacting Mazdas head Engineer who is going to give us an answer, will post when answered back

CERAMICSEAL

Very very good stuff. I just commented about the excessive side seal clearances in another thread. The troubling thing is Mazda's current specs have not changed to these large numbers, just the actual figures being measured.
The other thread was about oil being found in the airbox and intake hose. Blowby due to excessive side seal clearances?

rxturbo

Hello ceramic seal,

Thanks for your input, we haven't done much work on RX8's but we have done a lot of research on the motors and its interesting to know about the oil. I could understand a turbo motor getting oil in the intake but maybe oil from sump blow by and then into the breather hose to the intake. We have learnt that mazda had a lot of prototype engine out there that also made it into the first batch of RX8's, they had 13b efi 9.7 rotors in them with no blow by seal. Maybe mazda had to think fast and solve some issues by putting in tapered side seals and blow by seals. How much oil was in the intake.

Thanks

CERAMICSEAL

A fair amount of oil. A little puddle.
What are you finding with the depths you can cut apex seal grooves to? Are the ceramics you're using from the 'doctor'?

rxturbo

hello Ceramicseal,

Yeah with the oil I would say that it compression leaking into the sump and pressurizing the sump leading to excess pressure on the pcv valve, Its just a good guess.

With the rx8 rotor apex seal depths we bit the bullet and cut one up to see how it would handle the deeper groove. Luckly the cost of the rotor was worth it and its ok to cut the groove deeper. but we first tried to cut the groove deeper but still retain the 2mm groove but its doesnt work so we decided to cut them 3mm instead and have a perfect groove cut, all grooves are cut with cnc wire cutting and its the closest to perfect we can get. About the DOCTOR i dont know or heard of him, maybe because we are based in Australia, can you be more specific,

Thanks

CERAMICSEAL

Are you at liberty to say whether your seals are manufactured in Australia or elsewhere?

rxturbo

Not in Australia, thats all iam saying. We are working along side the manufacture and have tested some of his seals in our own race car engines and with some minor changes we have asked him to do, they just how we want them. He is also going to make us some 2-piece 2 and 3mm twin spring ceramic seals, cant wait. But i would have to say that after all the seals we have brought around the world these would have to be the best, even better than lannetti seals and half the price, and trust me we have have lanetti seals and had them x-rayed once delivered and found small fragtures in them were as these seals have none.b