J.S.J

I did a compression test (13b TT) and found over all it looks good. I do see using a normal compression gage a small difference in the rhythm in one rotor than the other. One seems to have for a lack of better terms a slight glitch in its rhythm compared to the other. My engine builder said this is likely due to balance. He said when all the rotating parts are balanced as a unit this does not happen and its normal for this engine. I need a second opinion on this.

gambone

iTrader: (3)

OK up front I'm going to say he is snowing you or he doesn't know what he is talking about. My frist thought is some crome as come off and as the apex passes this spot there is that glit you see on the one rotor

J.S.J

I had another conversation and he did say its possible one of the apex seal/springs is still seating/breaking in. I have dealt with him and he is real prompt in getting back to me and has shown real concern with all my questions however thats not real hard on the bank account. I will keep an eye on this and see if I can get a Mazda compression unit. I am going to shoot a video of the reading and slow it down. That way I can see things clearly. I plain to do this in a few days. I think this will show me all I need to know. John

RacerXtreme7

iTrader: (2)

First off, the mechanic your talking to sounds like rather then dazzling you with his rotary brilliance, he’s baffling you with bull chit. Rotor imbalance/balance will not affect compression at those slow cranking speeds.

Second, chrome missing from the housing would show a lack of compression on ALL faces (3) of that particular housing / rotor chamber.

If you’re seeing a constant "bump, bump, bump" on your guage then it’s all-good. If you’re seeing a "bump, bump, small glitch of a bump" (in any order), then it’s a SIDE SEAL problem. If you see a "bump, bad bump, bad bump" (again, any order) then its a APEX seal (or two bad side seals). A bad apex seal will show on TWO rotor pulses because the seal seals off two rotor flanks. Were a side seal seals only one rotor flank.
Sounds as though its still breaking in??? If so, get some easy miles on it and change the oil and break it in proper. After its broken in (at least 2500 miles with a gradual load applied to it), then test compression, if there’s still a glitch, then worry. Refer to a manual (I don't recall the specs off the top of my head at the moment) for minimum/maximum compression psi and for a min/max psi rating between rotors.

~Mike................

J.S.J

RacerXtreme7 ( Mike)
The post was very informative. I don't see a blip in two pulses. I see one and it seems to be a bit inconsistent but its there. I have about 750 miles on the engine now and will surely take your advice as well as shoot a video t keep just encase things don't go well. John

RacerXtreme7

iTrader: (2)

if your seeing two bad pulses on your guage, then it most likely is a bad seating/sealing apex seal. It possibly could be two bad side seals also. Its common to see differences and even low compression on a fresh rebuild especially if its used housings and new apex seals. As long as it runs OK, just break it in properly, then compression test it when things are nice and seated. I tend to be careful with break in...... first 200 miles NO boost and a 3500 rpm limit, change oil. Then over the next 1000 miles gradually raise your rpm limit to 5200 and NO boost above 2-3 psi, change oil. For the next 1000 miles add more boost and rpm limit till after 1000 miles you should be able for full throttle and full boost. Change oil..... This is really cautious and may be over kill, but maybe not so much if its used rotor housing and new apex. New apex seals and new housings might not take as long. youcan always do a search on others break in proceedures.

~Mike..............