Hi everyone =)
I have this strange issue sometimes, that remind me of a clutch going bad. Here is an example:

I am getting ready to get on to the highway, usually i am starting in 2nd and make the turn up the ramp. I usually give a liberal amount of throttle because racecar. Everything seem fine and dandy, and i go to 3rd. I stay in third past the speed camera, and then give it some more, and put it in 4th. i cruise along around 3k rpm for a while, and then get to a pretty flat straight. I floor it, and start to accelerate. Then (some times) i get what feels like "flat" area in the power curve. The engine revs, it change note, but the car does not seem to react. My ears and the rpm gauge says im going faster, but the butt-dyno and the speedo says im not. It feels somewhat similar to an autamatic shifting gear.

If i release the throttle, it sounds like the engine and car cath up again, and when i push it down again, its accelerate normaly.

Its somewhat hard to reproduce, but it happen form time to time, and has been like this for a year at least (but i rarely do much highway miles so i rarely experience it under my normal drivng.


Does this sounds like a bad clutch to you?
The car has 55k km /34k miles (i suspect a lot of that is "city-miles") on the clock.

Given that it is the clutch, what do i NEED to change while doing the job, and what is RECOMMENDED to change?
- Clutch?
- Pressure plate?
- Bearings?

And what clutch do you recommend? The car is unmodded except HKS DP, and wont se much power mods in a few years.

 

Sounds like a bad clutch to me. Replace clutch disk, pressure plate and pilot bearing. Check the clutch fork for cracks. You should consider adding a lightweight flywheel since the tranny will be unbolted.

 

I see that Banzai has three different "Kits" for sale. Im prorbaly shopping from them singe i need some more stuff from there.

- OEM replacement
- Stage 1
- Stage 1 Heavy duty

What are the recommended HP levels they can handle?

 

I would just go with the ACT HDSS and possibly the streetlite flywheel if you wanted to upgrade that while you are there. Clutches are rated in torque capacity at the flywheel. For example the Exedy stage 1 is rated at 248 ftlbs, the ACT that I mentioned is rated at 402.

ACT Clutch (93+ RX-7)

 

I wont be doing the flywheel yet (if ever).
So your recommendation is the HDSS? It should hold 350hp on twins if im not wrong in my calculations?

 

Yes, it will hold 350hp. You will need to resurface your flywheel if you are not replacing it.

 

Also many 93s had a weak clutch disc from the factory and would slip even bone stock with low mileage. I did a number of those back in the day. Mazda upgraded the stock clutch with more torque holding capacity because of this, any new OEM clutches hold much more power.

The symptoms you're listing are 100% a slipping clutch. Minimum new clutch, pressure plate, and throwout bearing. May want to go to a light flywheel while you're in there. Also, replace the gear oil in the transmission.

Dale

 

I forgot to mention the throwout bearing. Of course, Dale didnt forget it

 

Thanks guys. Clutch-job is on the list for next season then
Gear oil is only hardly driven more than a couple thousand miles, as i changed it ebfore i put her in for the winter last year. Can it be reused you think?

 

It should be ok. You will likely have the drain the tranny to remove it. Could be a big mess if you dont drain the fluid.

 

And for how little it costs (~ $12), a rear transmission seal. Consider a new clutch fork if you've never changed it and you're upgrading the clutch.

And unless it's just out of budget for you (and I get that) I second that Streetlite FW suggestion. IMO it's a power adder w/o the baggage.

 

Im trying to keep it on the low side Flywheel would be up when i upgrade the rest of the engine (BNRs++). Also, doing a flywheel requires a counterweight and balancing? Not sure how much more work is involved, but im guessing it gets expensive real quick?

How much does it affect drivability? I had a lighter flywheel on my other car (626 V6) and it was a nightmare to drive in regular traffic with start-stop and slow driving.

 

An ACT streetlite or any of them around 9.5 lbs, would be very drivable. You'd probably forget you had it within a few miles of driving until you notice the quicker acceleration. Even some of us conservative old guys like 'em. You just need a counterweight from an auto, no other special balancing. But it was just a thought, resurface the stocker for now.

 

My 93fd has 180,000 miles on it with the original clutch still. I have started to notice a crunch sound/feeling when going into 5th gear. Is this the clutch or the synchro?

 

Ideally if you could drop the transmission and inspect the old clutch before purchasing a replacement that's what you should do.

I just replaced my perfectly fine clutch with a new one because it turned out that there was a bunch of built up crap on the transmission input shaft so the throw-out bearing wouldn't easily slide on it. The clutch never got full clamping force as a result. Since I had it apart and had new parts I replaced everything, but now I have a back-up clutch and pressure plate for next time. The old stuff still looks almost brand new, has maybe 10k miles on it.

 

The 93 5th gear synchro was known to be weak. IIRC there was a TSB issued and a stronger synchro along with a stiffer shift select spindle on later models.