Pat Hamilton

My wife and I bought a 1987 RX7 several years ago, and, about a year ago, decided to have a new exhaust system installed. Our mechanic (we don't work on it ourselves) had recently bought a bunch of exhaust system equipment, and said that he thought he could build one instead of getting a factory-built system.
This may have been a mistake.

After he put the new system on, it started running very noisily....almost sounded like an old truck, and soon would barely run (we didn't even take it home and left it with him...where it still is today). He is not specifically a Mazda mechanic, but is a very sincere and honest man. He says now that the compression is testing badly, and that he thinks the engine is shot. It was running really fine when we left it, and he thinks it's only coincidental that it developed the problem immediately after he put the new exhaust system in.

I'm wondering if it's possible that it simply needs to have a factory exhaust, and then everything will be fine, but I hate to spend the money to test a theory.

Does anyone have any thoughts and/or experience with this or a similar situation?

jdi_knght

Just a note on the compression check - you said he's not specifically a Mazda mechanic. There's a special compression tester that's supposed to be used on rotaries, so if he was using the basic one it may not be reading accurately.

petex

it's not easy to damage a rotary engine, it doesnt happen as coincident or minor mistake.

it's always repeated process and the person who is doing it, knows that something is not right.

your engine is fine.

what kind of exhaust your mechanic installed? cat? what about aux ports? emissions?

what were the compression numbers?

you dont need mazda compression tester, u can use standard tester, just use common sense.

what led him to declare the engine as shot in first place? any other signs of low compression?

Pat Hamilton

I'm sure that he was using a standard (non-rotary) compression tester.
Thanks for the tip

Pat Hamilton

Thanks for the info.
I've printed your reply and will show it to him. I don't know the answers to your questions, but it's reassuring to hear someone say that the engine is fine.
One thing I didn't mention (tell me if I'm hearing him incorrectly) is that it tested o.k on two of the cylinders, but nothing on one of them. Does that make sense?
Thanks.

gio64

iTrader: (1)

Well, the engine doesn't have cylinders, but rotors, 2 of them. Each rotor fires on each face, therefore, it fires 3 times. What you should see on the compression test is 3 values from each of the rotors (this is assuming, obviously, that you don't have a 3 rotor conversion, which I believe we can pretty much rule out).
If you have a problem with a seal on one of the 2 rotors, your compression test will show 2 out of the 3 compression numbers on that rotor to be 0 or sadly low.

I don't want to speculate on what your mechanic meant to say with that, but it doesn't sound right, even referring to 3 compression values on the same rotor (it that's what it is).
More info is quite necessary here.

TurboNitroso7

Yes i also agree it does not make any sense unless he went by each spark plug hole (in which case he forgot one cause there are 4) he might have checkec compression on two spark plugs on the same rotor therefore getting 2 "good" readings and then he went to the next spark plug which would be the 2nd rotor where he got nothing, now unless he stopped there and this is why he ended up with three readings because he thought he found the problem or what is where it doesn't make sense to us, but I agree even with a normal compression tester (non-rotary) he should be able to get a reading from all four spark plugs but to help simplify this process for y'all all he needs to check really is both bottom spark plugs the front one then the rear one cause the top spark plugs are in the same chamber as the bottom ones. Hope this helps!

gio64

iTrader: (1)

Interesting, theory, I didn't think of it...
We still need to get more/better info.

Pat Hamilton

Thanks to all of you who have given thought and time to this problem of mine.
I probably won't get to talk to the mechanic until this weekend at the earliest.
I will give him the questions and thoughts that everyone has on this issue.
Hopefully I'll be able to get more and more specific information.
Much appreciated!

Pat Hamilton