OK so i am doing a compression test on my turbo vert. It was running fine then stoped and started to go bang, bang, bang, when i was trying to start it. So I pull the trailing plugs and turn it over for a few seconds to clear any fuel. Note: the egi and the inj fuses where pulled and my pedal was all the way down. Next I screw in the the tester and turn it over for 5 secs. It sounds good just like befor. Pulse, pulse, pulse. Got the results, which where very nice, and when on to the rear. This time when i turn it over, it goes bang bang bang.

So what the hell is makeing my engine go bang? It sounds like a mechanical bang, not like a fuel exploding bang.
The trailing plugs are both the right NGKs 9s iirc, but it has the two blue stripes so i know thats right. I forgot to check the leadings but i'm assuming they are the ngk 7s.

When this first happend i assumed that I blew a seal and that was why i was getting that damn banging. But now spinning it without the plugs in makes me wonder.

Compression results Front: 95 97 91 RPMs at 226 Rear 56 88 81 rpms 246
Front is great, back not so much. I'm really curious about the 56

Help!
and thanks
AUG

 

sounds like a dislodged apex seal , i would stop turning it over till you can locate the bang

may not be completely dislodged , but chances are the more bangs=more dents in rotor housing

 

Although its probably not these things can spin bearings, and that gives off an awful noise in the process. I would be inclined to believe not an apex if you are pulling 80+ psi in the offending rotor.

 

But why would it only bang with certain holes pluged?

 

its not trying to start up and running so rough that the engine is shaking really bad is it?. have somone crank it over while you listen

 

If it was an (i.e., one) apex seal, you would "see" the pulses from two adjacent rotor faces significantly lower than the third face (see example below). The numbers you got for your rear rotor do not fit that condition.

I would suggest you redo the test on the rear rotor with all spark plugs installed except leading #2 where you will be taking the readings. Make sure that whoever is cranking the car fully depresses the gas pedal while cranking. That can make a big difference in the readings. Repost the results.

 

OK new test results.

Rear 88 80 50
RPM 231

I also played around with the plugs.
With the front plugs both in and rear one with the L in and T used for the tester. BANG BANG BANG

With both fronts in an Rear L in and T open to air, bang bang bang
With both rears in and Front L in and T open to air no bangs
This is really weird.
Side Seal maybe? But why only bang with both plugs in my not all the time?

Arggg

 

Those numbers suggest a failed side seal as you postulate. The other 2 faces are not too bad considering the engine rpm at the time of the test. Not sure what the banging is all about.

Try doing what I suggested: test with all plugs installed except the leading #2 which you will use for the test. Not sure what that will tell you, but it may be another data point.

 

It appears (sp?) that if the trailing plug is out of the rear then I get just the puff, puff, puff. But as soon as i plug it, the puffs turn to bangs. Really weird.

I'm done with testing on this.
1. I don't have the tester anymore, I borrowed it and shipped it back to the owner. and
B. I really don't want to cause anymore damage then I alreading have. I'm going to go down to atkins on wed or thurs and talk to them about a rebuild. I am actually leaning twords Pinapple right now though. Prices would be about the same . Atkins uses 3mm apex seals. but i'd have to pay extra to get "new" housings. Pinapple I would have to pay extra for the 3mm seals but they put "new" housings in all there builds.

I'm also going to check some local, rotary, shops and see if they have any ideas what the hell is going on.

Of course, I'm also considering blowing my head off. So there's that.

 

never heard a banging sound from the internals of a rotary..those are piston problems, lol. but in all seriousness what made you want to do a compression test in the first place?

 

thats an easy one dude , bang from internals

 

Let us know what the rebuilders find when they open the engine.

 

It wouldn't start and the banging noise made me think that I had a something FUBARed in the housing.

 

sounds like the heat from the plug warped the housing just enough for the apex to catch it . not surhow they warp but i have heard of this being a problem due to inefficient cooling passage designs. maybe you lose compression before it hits