BarbarianFX

Hi guys, my engine just overhauled because i getting a compression reading of
1st rotor - 97 / 94 / 97 psi
2nd rotor - 110 / 108 / 108 psi
I go for another compression check about 5 days after overhauled and i get this
1st rotor - 104 / 102 / 104 psi
2nd rotor - 100 / 98 / 98 psi
All the reading is base on 250rpm.
No housing is replace because it still in very good condition as mechanic verified,
My question is why the compression still so low after overhaul, is it true that the new rebuild rotary engine need to run in 1st to get a better compression reading as some forum fellows mention?
Any bros who overhauled his/her engine can comment on this?

04RX8TX

i Would think that new seals that are set right ( clearances ) etc.
that you would get better compression right away.

I know on my motocross bike ( 2 stroke )
when i would get below par compression readings id slap a new set of rings and my compression would jump right off the bat.

So id presume if your engine was rebuilt correctly you should get better readings.
but i do not no much at all about rotary's

Can some one Confirm?

olddragger

iTrader: (3)

if the compression check was done correctly then the rebuild didnt work.

BarbarianFX

Do you mean just chnaged the o-ring? Thx

BarbarianFX

Yes the compression done correctly and adjusted the reading at 250rpm.
Apex seal + spring and all o-ring are replaced while all side seal + spring and corner seal + spring are all reused.
I do notice that the side housing have the slight groove mark which the rotor moved. Do we need to re-surface of skim the side housing during the rebuilt and replace all side seal + spring all well?

Any expert can help comment?

olddragger

iTrader: (3)

uhhh---yea --side/corner seals and most importantly the side seal springs must be replaced. The plates also need checking just like the housings.

WingleBeast

a rebuild without replacing side seals? OR resurfacing? you are pretty much dealing with the same engine you had before the rebuild when it comes to side sealing

nycgps

iTrader: (1)

why not replace ... the side seals and corner seals are not that expensive ...

question : who did the rebuild?

lastphaseofthis

Why waste cash on unnecessary ****?
(side seal) springs, apex seals, apex seal springs, and all rubber seals are all you need. "Goopy" the housings(almost always a benefit), and check every tolerance. resurfacing the side housings is a NO-NO if they're in spec. it's like turning brake rotors that have no run out! what the **** are you doing it for?

and OP, 5 days after a rebuild? i mean really? are you retarded? take it back after 1500 miles. and again at 3-4k. I've had rotaries that wouldn't even START, b/c the rebuilt compression was so low... i had to pull start it, and then drove it for 105 miles before i shut it off. next morning, starts fine. 4 months later, 115+ compression all around. i've also had a few 13b's start and NEVER flood, and NEVER have idle or starting problems.... on 100k+ mile housings with NO goopy milling.....





ALSO:
1st rotor - 97 / 94 / 97 psi
2nd rotor - 110 / 108 / 108 psi
Before? were you having starting problems or something, those compression readings are NOT bad enough to justify a rebuild, unless you had coolant seal leakage/burning too much oil.
Although the rx-8 FSM says 98.6 psi minimum and 14.5 psi difference between rotors, on previous 13bs the minimum was 85 PSI and 21 PSI diffrence, why the change? dunno... probably the side exhaust configuration... but i wouldn't focus on the numbers so much as i would HOW THE CAR RUNS. I means thats whats important right?


84 GSL-SE, 13b.