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You'd need a real compression tester to be sure, but the wide variance between rotors on a piston tester is not confidence inspiring.You can try manually rotating the rotors with the spark plugs out and see if you can actuate the apex seals by hand to eliminate their being stuck in the rotors. It is possible a corner seal fell out or any number of possibilities, if compression is the source concern.
Most common post-rebuild no start/hard start/rough idle with the RX-8 relate to the fuel injector connections being swapped around. It can mirror weak compression in the sense that it cleans up as RPM increases and the other injector sets are engaged (secondary ports open), though that happens higher in the RPM band than you indicate the engine will remain operational.
This doesn't provide RPM windows, but the second injector set comes online with the secondary intake ports, fueling the two primary ports in addition to the secondary ports. The tertiary ports do not have injectors and are 'air only'.
Most common post-rebuild no start/hard start/rough idle with the RX-8 relate to the fuel injector connections being swapped around. It can mirror weak compression in the sense that it cleans up as RPM increases and the other injector sets are engaged (secondary ports open), though that happens higher in the RPM band than you indicate the engine will remain operational.
You are correct that fuel injectors and other reinstallation errors can cause problems associated with low compression but that doesnt seem to be the case here. That's why a compression test is so important. It needs to be the absolute first thing to check because it focuses strictly on the engine itself.
The symptoms of running fine cold but stalling and not starting hot combined with rough idea compression results show something isnt right in the engine itself. It's not really necessary to have a true compression done at this stage due to added costs that should really be put back into the engine.
A regular compression tester is fine just to confirm the issues are engine related.
I got to the primary injectors. The old rubbers were still in the iron. I removed one set and the made a plop sound as they seated correctly. Think might of been my problem....
Ok so I placed it back together what I thought was correctly, and drove it. Same problem. Parked it in the garage and one of the primary injectors was spitting fuel out. Went back in, bad oring got pinched in the rail, see picture. It had also threw me a misfire on 1 rotor, which was the one leaking. Autozone had OEM ones replaced them, started it and wow it idle d well. Then went to **** and started shooting gas out again. Going back in again tomorrow. I am a f'n pro at removing upper intake now....pretty sure no vac leak.
Furansu is gonna get my comp tested this week ! Thanks everyone for the help !
Still very low numbers but glad he helped you to get it running. There is definitely an issue in your rear rotor, I dunno how long it will last. Even the front rotor numbers aren't that great. Give it a good blowout and see what happens but I think it looks like you may be tearing this down again.
Your right not going to last long. I drove for an hour tonight. Got 5 hot starts outta her. Gonna have the comp tested again after 1k miles.
I have learned a ton and I believe my next build will be even better. Gonna enjoy it while it lasts.
The only problem I got with this is that you may do damage to the new components you put in running the car on low compression. It's risky, but in rotary world, what isn't risky?
Got about 400 miles on it now. It's actually decent. Keep you updated on the longevity.
Thank you for doing this and posting it on the forums as you go.
This is your first attempt at building a rotary right? I mean at least it cranked and it drives!
Threads like this give me hope for the future when I have my own place to take an engine apart and learn to build myself.
The way I see it is, the experience is invaluable. Material possessions come and go, but experience lasts forever.
09-21-2019, 11:34 PM
