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A few months ago I put together a 13B PP for my 1st gen. It has RX8 rotors, all new OEM seals except for ALS Ceramic apex seals. I've made a couple of posts trying to diagnose an issue where it essentially rev-limits itself at WOT and wont rev over 5k. Today I did a compression test and got the results below. It starts cold and hot perfectly, but it only has 10 or so miles on it with a few hours of idling. The rotor housings were all resurfaced, but there was still some edge wear just barely within spec. Side housings were also lapped, there was one small gash maybe 0.5mm deep in the combustion area, but it was very small.
What do you make of these numbers? I'm very happy with the front rotor, but the rear scares me a bit. I did have some trouble cutting the side seals (RX8 seals are notoriously annoying) and from memory 1 seal came out of the packet with 0.007" while the rest I got to around 0.003".
I'm pretty sure I know the answer is going to be tear it down and have another look, I just want some more opinions. The even compression across all rotor faces makes me think I cut the seals well enough and it could be a housing. Maybe I just got unlucky and cut them equally poor. Could it just use some miles putting on it? I know comp goes up after break in, but surely not enough to bring that rotor into spec
I would give it some more time to for the seals to seat before condemning the motor. I haven't read your other threads, but I would suspect tuning or ignition being the main culprit. Could also be detonating. Story time..back in the late 90s, I had a factory peripheral port engine with Mazda competition race rotors that I drove on the street. I can't recall the compression ratio of them, but they where higher than factory, and had a bath tub shape like the 13Bs do. It had a similar issues as you. I ended up running 11 range spark plugs, and super unleaded to keep it from detonating. For what its worth, the motor, timing 48/51 IDA was set by Rob at Pineapple racing. He knew what he was doing. The lightened rotors, lightened pressure plate, aluminum flywheel, and 3 puck clutch really let that motor rev insanely fast! 7,500 to 11k was alot of fun. I also had .488s and a gsl-se gear box in a 81 FB.
I would give it some more time to for the seals to seat before condemning the motor. I haven't read your other threads, but I would suspect tuning or ignition being the main culprit. Could also be detonating. Story time..back in the late 90s, I had a factory peripheral port engine with Mazda competition race rotors that I drove on the street. I can't recall the compression ratio of them, but they where higher than factory, and had a bath tub shape like the 13Bs do. It had a similar issues as you. I ended up running 11 range spark plugs, and super unleaded to keep it from detonating. For what its worth, the motor, timing 48/51 IDA was set by Rob at Pineapple racing. He knew what he was doing. The lightened rotors, lightened pressure plate, aluminum flywheel, and 3 puck clutch really let that motor rev insanely fast! 7,500 to 11k was alot of fun. I also had .488s and a gsl-se gear box in a 81 FB.
I'm giving it some more miles today, so we'll see. That was also a cold comp test, so the number might be even worse. Maybe I'm just being paranoid.
Do you really think it could be detonation? I thought with the ceramics, theyd shatter at the first hint of it. Certainly should've by now with all the testing I've done. I'm using 95 RON petrol (87 US) and 9 heat range plugs. Just took them out after a ~50 mile drive and they're pretty pitch black, so it probably tuning as well, need to hook my AFR gauge up again.
