I have a 1987 with 172k. This is my first rotary and I'm not sure if the problem I'm having is natural or if it's an actual problem. I went to Aaron Cake's link (sorry i can't find the exact one now) and he says it is ok to redline and is actually good for it. (to clear out carbon and such) Is this true? If so, when I get the R's up around 5500 I get a crazy vibration that I can feel in the shifter and in the seat of my pants. I've never gotten to redline just out of fear of blowing the motor. Now that I think of it, I'm not in danger of VTP contact so is there any danger in over-revving the engine? And what's the vibration that's gonna rattle my fillings out?

 

It's ok to redline. Just not every time you accelerate. High RPM's cause increased wear, but certainly the rotary likes being driven hard.

Sounds like your problem is your driveshaft. Take it to a local driveline shop and see if the u joints can be replaced, and have it rebalanced. Alternativly replacement driveshafts are available. Mazdatrix.com carries them.

Fix your problem and then you will be able to redline without vibration.

 

Strong vibration is not normal. A rotary should be smoother up to redline than a piston engine simply due to the fact that everything rotates. It's also more forgiving if you happen to go a bit above redline. There are no valves to bend, but the internals will be stressed more than normal, which isn't great for longevity.

For the vibration, I'd be looking at the motor and transmission mounts for signs of damage. Also consider the water pump, which has the clutch fan attached to its pulley. I had a bad one that would give me a vibration around 4.5-5k rpm, then go away somewhat up to redline.

Can you cause the vibration free-reving it out of gear, or does it only happen when the engine is under a load condition (driving)?

 

need new motor mounts is my guess

 

sounds like something drivetrain and or exhaust related... double check all the bolts down there and take a look at your exhaust system

 

Correct. If it IS related to driving, it's a problem with your driveshaft, and it's pretty common once you get up to the mileage you are at.


Also, it is okay to redline a rotary engine. However, redlining an engine that is not running properly can cause problems. If everything is running properly, you can redline every gear if you wanted to, just don't expect to go anywhere past 7k rpm's.

 

can be anything from driveline unbalancing or wheel torque. I have seen people not tighten there wheels down before. Especially after watching that FD. haha.

 

You think I don't know how to torque my wheels? Come on man, I would have snapped a wheel stud before I got a vibration.

Thanks to everyone for the advice. I guess I'm just gonna throw it on a rack and do a more thorough inspection of everything...chassis, driveline, and under the hood. I will post my results when I find something. If not, I'll be back.

 

check the u joints from the drive shaft. I had the same problem

 

Yea it might be the drive shaft...you won't know until you take it of lol cause I remembered looking at it and I couldn't tell until I took it off...

 

maybe this might help http://mazdatrix.com/g2.htm

 

seems like if it occurs at exactly 5500 rpms everytime then it seems like a drivetrain concern would be less likely. Like RotaryRocket88 was asking, does it occur while free-reving or while under load. that would be the for sure way to determine if it was possibly draveshaft related. also you would think that it would occur at different RPMs in different gears if it was related to the speed of the drive shaft since with the exception of every gear except 4th the shaft would be rotating at a slower speed and then a higher speed in overdrive (5th gear).

 

also, marking the correct position of your u-joints before removal is not a bad idea since incorrect phasing of the u-joints will cause a speed related vibration.

 

Ok, I can rule out the drivetrain as the cause of my problem. I tried free-revving the motor as previously suggested and it still makes the vibration at 5500, cuts out, then comes back around 6500. Could a rotor with low compression be the cause? Or maybe a harmonic balance problem?

 

hmmm.....it definitely seems like it is going to be related to the engine then. do you know if the flywheel might have been replaced or swapped? just because there is a flywheel counter weight on the front of the e-shaft that has to be replaced with one that is matched to the flywheel. possibly an unbalance of weight on the clutch pressure plate etc. other than this i don't know, certainly seems like an issue related to the balance of the engine. i would also check the fan, and other accseories driven by the engine. i mean any cracks, missing blades or even just some mud, or debris on your cooling fan might throw off the balance at certain engine speeds. just a few more suggestions, hoe this helps.

 

Like I suggested before, check the water pump pulley / fan assembly. You can get away with taking the fan off, reving the motor brieftly, then shutting it down. Just DO NOT let it run long enough to overheat. The fan's only held on by four 10mm nuts, and can be removed without taking the shroud off.

This will take 15 minutes and at least let you rule it out as the cause. You'd be surprised how much vibration the stock fan can create when the pulley is imbalanced. Replace the water pump if you find it the cause.

 

yeah, that is what i would do. and if it does end up being the fan, and you've got the money, i would go ahead and just upgrade to an electric fan.

 

My car had that same problem a strong vibration at 5500rpms. The driveshaft looked fine until I took it out and the u joints were shot out. You should definately check it out and if you need to replace the u joints you can fix your car for cheap.

 

If the vibration is always at 5500 rpm, regardless of gear selection or speed, then it's engine related. Push the clutch pedal in/out. if no change, then it's a belt driven accessory on the engine. If the vibration is heavy, I'd check the fan first.

 

i have the same problem on my 88 n/a and i think its because bad tranny mounts or shocks