Hey Everyone

I have engine vibration and need some guidance for my next move. I would like the car to be ready for summer. Also I have a little racer on the way so my budget is shrinking by the day.

Here’s the story

Back in 2001 I had a reputable engine builder in NC build me a 1988 TII engine. I was on a budget so the engine was built with used parts. I was told it was a built with 8.5 compression rotors. It has run perfectly for 9 years, and made 230 rwhp with a Camden supercharger. I switched to turbo setup (ran great) and then switched to a light weight flywheel (ACT streetlight and clutch). I ran a S5 counterweight because I pulled off a N370 flywheel. Now I have an increase in engine vibration above 2000 (very mild), and at 2000 rpm I have more severe vibrations (moderate to heavy). Below 2000 rpm it has the same level of vibrations as a stock engine. The engine pulls strong to 7500 rpm redline, and power does not seem to be effected.

Options to vote on (1, 2, or 3)

1. Put the stock flywheel back on (no fun, I like the new one)

2. Pulling the front cover, inspection the bearings and front counterweight to make sure it matches the rear counterweight. Then buy a matching set and hope it works.

***Can I identify the engine rotors without opening the engine (beyond the front cover)? If so I could be 100% on which set of counterweights to buy.

3. Drive it until it dies, because it pulls like crazy. I wouldn't reuse much from my engine, and I might not be able to afford a project car for a long time. I will not get any money for the car together or in parts.


Thanks in advanced, flame suite in on.

 

the S5 rear counterweight is not balanced to your 8.5:1(8.5:1 is 87 turbo II rotors) compression rotors and is likely eating up your rear stat bearing. put the stock flywheel on or don't drive the car until you can get the correct rear counterweight.

 

I think I have 8.5, but it was built with a N370 flywheel and ran great. So my engine could have a S5 front counterweight to match the stock flywheel I have. It would be nice to 100% ID my rotors and counterweights.

Thanks for your vote.

 

the only way to know for sure is to break the engine open.

balance issues aren't common in rotaries so i do think there is something wrong with the balancing of your rotating assembly.

 

Except for the 8.5CR rotors, I've got the exact same vibe situation. I suspect the ACT Streetlight flywheel wasn't balanced properly at the factory and your story confirms that. Pull the tranny, rebalance the ACT flywheel, and reinstall. A ton of work (dreading it myself), but better than replacing the stock N370 flywheel.

 

never seen an ACT flywheel out of balance.

 

I recently pulled the tranny on our recently purchased 86 for this very reason. The flywheel nut was loose, just enough to allow it to not seat the flywheel against the crank. The clutch looked almost new. The vibration was mild but may have been part of the reason this car was donated to charity. I knew from experience what I would find so I had a new lightwieght flywheel ready to install. I cleaned everything up and replaced the seal, retorqued the housing bolts, etc. I bought a big torque wrench and put 350 lbs./ft on the nut and it's perfect again. Whoever did the clutch prior didn't know it or didn't take the necessary torque seriously enough and it worked loose.

Vernon

 

+1, its more likely that the OP used the wrong counterweight.

 

If it ran perfect for 9 years then there was nothing wrong with the balance of the rotating assembly. I know you said it was an S4 engine but if you pulled an S5 flywheel then the builder used S5 turbo rotors and a S5 front CW. Is it possible the flywheel ACT sent was really a S4 turbo flywheel? If I was you I would pull the transmission and check the flywheel for a part number and double check it. If it's wrong then replace the ACT with the stock and hope the bearings last until a rebuild.
It sounds like your bearings are shot. I wouldn't rev it up or see how hard it still pulls until you have the time and money for to open the engine up and replace whats out of specs.

 

While the e-shaft nut could be loosening, it would take time for this to happen. In my case at least, the vibration began immediately. OP can comment on his specific symptoms.

I should have stated that an imbalance in the the ACT flywheel/rear counterweight combination is the likely cause of the vibes. The issue could either be the flywheel or counterweight (or less likely both). In any case you have to pull the tranny and remove the flywheel. Is yours an ACT counterweight?

To PvillKnight7, a single ACT flywheel part number covers S4, S5 and S6 models. The OP should check the P/N of the counterweight however, since the CW01 and CW02 differ from S4 to S5.

 

It's not the E-shaft nut, I checked the flywheel with a pry bar. I also installed a brand new nut during install.

I have a used OEM S5 counterweight, not an act unit.

Where can you balance a clutch and flywheel combo? After I verify my front counterweight I could send them out to be balanced.

 

you need the s4 turbo counter weight. And you need to pull out your rear stat gear and inspect the bearing(doesnt require much more work then swapping the CW out).

 

the only way to balance it correctly is to send off the rotors, e-shaft, front and rear balancers. i doubt you want to do all that when the only issue you are likely having is the rear counterweight is incorrect.

the other way you can get an idea of what you have is by pulling the exhaust or leading plugs off and rotate the engine until you can get a good look at the rotor compression pockets. an 8.5:1 compression rotor has a rough cast pocket, a 9.0:1 compression rotor has a smooth machined pocket.

again, i doubt your light flywheel is out of balance but i do think you have the incorrect rear counterweight regardless of what you pulled off of it. somehow you also could have gotten the wrong rear counterweight as well. i don't recall they have any part # stamps on them so someone could have fooled you.

http://mazdatrix.com/faq/Rcounterweights.htm

 

An out of balance or uncentered pressure plate will do this also.

Vernon

 

it would have to be a cheap *** clutch kit, i have also never seen a PP out of balance enough to cause a vibration issue either in about 100+ cars. it's possible but not likely. at any rate you take a look at what was changed and start to divide it into likely possibilities from highest to lowest like this(basically in weight of rotating mass is highest in likelihood):

1) rear counterweight, these have no part# stamps so they can easily get mixed up even if you order it directly from mazda because you can't easily check it
2) clutch kit, although unlikely it is still possible that the clutch wasn't bolted down properly and it is out of balance
3) pilot bearing/tranny input bearing. this is fairly unlikely because it didn't have an issue prior to replacement
4) flywheel out of balance. the least likely because a lightweight flywheel is machined perfectly flat and the ACT ones are CNC cut by machine, unless the machine was turned off prematurely and missed cutting some of the lightening slots i find this near impossible to be out of balance enough to even feel
5) an accessory failing. this can cause vibrations but i have yet to see it happen, there could also be dirt or another foriegn material in the front hub pulley grooves that is causing a balance issue. i have seen dirt caked inside the main pulley which actually weighed close to 1lb after i scraped all the crap out. even then the engine did not show signs of a balance vibration.

one thing i did not notice though is how the OP is determining the vibration. is this with the car stationary? if the car is moving and you have a vibration there is many other factors to consider such as driveshaft u-joints and tires out of balance.

 

1) rear counterweight, these have no part# stamps so they can easily get mixed up even if you order it directly from mazda because you can't easily check it

I used the mazdatrix method to ID the cw.


2) clutch kit, although unlikely it is still possible that the clutch wasn't bolted down properly and it is out of balance

It works and doesn't have play so I do not think this is the issue.

3) pilot bearing/tranny input bearing. this is fairly unlikely because it didn't have an issue prior to replacement

Both selas are brand new from Mazda dealership

4) flywheel out of balance. the least likely because a lightweight flywheel is machined perfectly flat and the ACT ones are CNC cut by machine, unless the machine was turned off prematurely and missed cutting some of the lightening slots i find this near impossible to be out of balance enough to even feel

I had it turns less than .001 to take off some surface rust, but I saw no machining errors.

5) an accessory failing. this can cause vibrations but i have yet to see it happen, there could also be dirt or another foriegn material in the front hub pulley grooves that is causing a balance issue. i have seen dirt caked inside the main pulley which actually weighed close to 1lb after i scraped all the crap out. even then the engine did not show signs of a balance vibration.

My car is clean (because I take it apart soo much). I only run altenator and water pump.

6). one thing i did not notice though is how the OP is determining the vibration. is this with the car stationary? if the car is moving and you have a vibration there is many other factors to consider such as driveshaft u-joints and tires out of balance.

It is stationary and moving. The driveshaft and axles are good, just installed them last years. I have driven like 200 miles with the vibration. It's not that bad except at 2000 rpm (like a harley or v8 with solid lifters @ 2000)


I heard on another post the front thrust bearings coulds make this vibration if they were damaged during install (I put a new seal on my rear sationary gear when I changed flywheels). I still think I need new counter weight or weights but It could be an issue.

Thanks for the help Karack

 

You are fully aware you need the proper counterweight to match your lightweight flywheel...Thats your problem right there.

 

Are you saying I need an ACT counter weight to run an ACT flywheel? Why?
As far as I know plenty of people run OEM rear counter weights.

 

Well your changing the weight of the flywheel, so yes you need the weight to match.

 

You don't need the ACT counter weight. The flywheel is a balanced unit, then you attach the counterweight to balance the rotors.

 

i still think something doesn't add up, perhaps the flywheel nut worked loose.

 

The way he described the vibration to me (over the phone), I don't think its a counterweight. But until he pops the trans off there is no way to confirm that.

 

Then the question to answer would be did the vibration show up immediately or has this set up been working for a while without vibration.

Also an off center pressure plate will work perfectly, it's not going to be off that much. My Racing Beat flywheel came with new bolts that were so tight in the old pressure plate I had to knock them through with a hammer then bolt it upto the flywheel. The factory bolts had a shoulder.

I haven't done a hundred Rotary clutches but I've done at least a hundred clutches as I'm a shop manager and do a lot of performance work. With stock replacement parts I can't recall many issues but when mixing and matching parts as SuperchargedSC has done I've seen it happen several times. In many of the cases I worked or consulted on it was an off center pressure plate due to incorrect alignment hardware for the mix of parts, ie. pins vs. bolts vs. shoulder bolts, etc. Sometimes it's a defunct pilot bearing. Only on my latest Rotary was it due to a loose flywheel. I don't know if it took long to loosen up as it was like that when I got it. And it wasn't flopping around loose, but it didn't take more than 40 lbs./ft. breaking torque to spin the nut off. I could see evidence of the flywheel having moved on the keyway. Not much but enough to cause a light vibration.

Something is causing it, if it's not the incorrect counter weight then it's the flywheel and pressure plate. Why is the question.

Also on #3 up there when asked about the pilot and input shaft bearings you said "both seals are new, from the dealership". Did you mean bearings? Though if it were the input shaft bearing you would have shifting problems so that's not it. The pilot bearing though needs to be there and in good condition, sealed or not.

Vernon

 

Just another possibility..... Perhaps when you removed the original fly wheel you accidentally bumped the eccentric shaft and knocked the needle thrust bearings loose and out of their cages. Then upon retorqing of the new fly wheel the needle bearings got crushed or the cage got crushed thereby causing a vibration? Check your engine and tranny mounts also, I've had an engine mount break (rubber separated from the metal) and it caused weird vibrations.

~Mike.........

 

Let me explain a little more.

I accidentally put a S5 counterweight on a S4 assembly, incidentally I purchased that rear counterweight from Supercharged FC (SFC), but thats a different story.

The vibration characteristics I had do not match what SFC is experiencing as my vibrations started at 3k and got extremely violent up to 6k where it then went vibration free. If I recall correctly SFC is experiencing a less violent vibration that builds throughout the entire RPM range starting at some number and persisting until redline.