I've had RX-7's lose compression before. Thing about them is that it's almost always just two rotar faces that are lost, and they're lost all together. I've never seen an RX with lower compression numbers, but even on all faces on both rotars. What I'm facing now is a 1988 TII that's alledgedly been rebuilt 20k ago with a large street-port, with 62lbs regestered across all rotar faces, on both rotars.

I've been trying to make myself feel better by saying that, with the ambient 14.6lbs or whatever, I have 76~ish psi...but I don't think that's the way it's supposed to be recorded.

I checked by removing the top plug and screwing in the compression guage. I left the schrader in...this guage just have enough resistance to register anything if I remove it. I used a 12v, high amp charger to make sure I got good amps and turned at least 300rpm. I checked each rotor 15 times to account for any variation in rotor faces. Identicle results every single time.

?

 

Do a search for a compression test. You should have to pull 2 fuses if I remember correctly, If you have 76psi then looks like you gotta spend $$$ like me right now since my rear rotor has 0-0-0 psi.

 

I disabled the fuel pump...that's why you pull the fuses. I guess I should have mentioned that.

I've done a search...hoping for some variable I didn't catch or for osmeone to tell me I did something wrong...

 

Well if you pulled the fuses then your good. Anyway 76psi... I don't think thats very good, but hey I wish I had 76psi rather then 0

 

Did you perform this test WOT?

 

yeah...actually I just took the intercooler off and tried it again (at WOT). Same results...little higher in the rear...a hair over 70psi.

 

There's a couple of things:

Not warm, flooded?, not WOT

OR

There could be clearance issues on the side seals/etc, or possibly even the side seals have become 'stuck' in their grooves, this will cause that.

 

Worn out rotor housings will cause "even" low compression and explain your other problems. Just because it was rebuilt does not mean that it was done correctly or with parts that were in spec to begin with. Throwing in a set of apex seals and some coolant o-rings does not constitute a rebuild. If the housings are worn out it will run for a short time then cause problems. This is just one of the problems with doing a rebuild on a tight "budget" you get an engine that doesn't last very long.

 

If she's flooded it'll lower the compression? Because she floods exceptionally easy due to some really leaky injectors.

I'll give her a ATF treatment or something for the side-seals, I don't know any other way to combat that.

She's a pre-mix car, if that has any effect...

Actually I don't think flooding would have an effect because wouldn't it all just push out the exhaust? as I'm turning it over?

 

If I must go down that route, can you tell me how much rebuilding my block would run if I used banzai?

 

arent u supposed to chek for compression in the bottom/leading plugs holes?

 

no difference.

 

I'm not sure if ATF will help stuck side seals if that is the issue BUT be forewarned that a compression test after an ATF treatment will raise the compression numbers so dont be so sure that the ATF solved a "stuck side seal" compression issue. Just so you dont get false hopes.

 

yeah it's just like slopping oil in and testing compression to test for bad seals.

 

I think ATF works way to slow to break up carbon, If I were you, I'd take a bottle of throttle body cleaner (not carb cleaner) and just spray the **** out of it into the plug holes while rotating the eccentric shaft. Do this a few times and let it sit till morning. Do the process one more time for added measure and try the test again, or even try starting it.

 

I just did a water treatment...used 16oz or so...not sure how much is the normal serving...didn't fix anything but she revved a little easier and drove a LOT easier...but she's still underpowered. I think I'm going to start looking for another block.

 

well, the water treatent actually got me a decent result, so I though "hey, why not some barryman's?" I went out to the shop and grabbed a can of barryman's EFI cleaner and dropped my boost-guage line down in it and pumped the throttle. Lots of smoke.

Result?

Same compression up from...pisser. However, throttle response and pull are both unrealisticly improved. The tach still climbs lethargicly, but it's gradual and steady. Stomping the gas from idle doesn't yield as prolonged a bog or kill the car, but it accellerates.

I still need to grab another motor, though...or maybe I'll just slap my S4 N/A block in there.

All the manifolds and stuff will bolt up to an S4 N/A block, right? I think they do...I'll go search some...

 

TII manifolds will physically "bolt up" to the N/A block, but the ports on the LIM will not line up with the ports on the block unless you do some serious hacking to the outside runners to make them match up with the secondary/aux ports.

 

would it really be a problem if I were just bolting it up for a temp solutiuon? Or should I use S4 N/A manifolds? I'm going to be running a front mount soon anyway...

 

If it's temporary I wouldn't worry about it. It'll bolt on but your flow just wont be even/proper. Basically part (most) of your aux port on the n/a block would be blocked off by the TII LIM if you leave it normal.

 

yeah it's not something I'd stick with...I doubt that motor would hold up to much anyway.

 

What exactly is this going to do? I've heard about the carb cleaner, water treatment, and ATF but not throttle body cleaner... I guess I could go search...

 

If you've heard about these, then you've heard about the tb stuff, too...same concept, different execution.