RX-7 height apex seal rev limit
 

Hi all
I'm having RX-7 tall apex seals installed as a part of my rebuild to future proof it for future FI, but I'll be looking to run it in NA form for a year or two post rebuild for my own convenience while I put together the funds for FI. Are there any considerations that need to be made regarding the rev limit when running taller seals? (chatter, etc.).

Older RX-7s had limits around 8k which is pretty close, but I'm not sure that makes 9000 safe.

Bump

Seems like a lot of users have done this modification, NA or not I'm curious to hear what your rev limit is set at.

I set my turbo Rev limit to 8200 ... no issue at that.

I was told by the shop that built my engine (rotaryengine.com) to set rev limit to 8750 for longevity. My engine has the rx7 apex seals as well.

as per most dyno graphs, NA hp typically peaks around 8300 - 8500 rpm on a Renesis regardless of Mazda’s claim

excessively over revving a Renesis only only results in engine wear and going slower assuming the situation allows an upshift.

in some racing situations riding the limiter is sometimes a necessary evil as opposed to an upshift due to the cornering dynamics etc. of the given situation, then you accept an accelerated rebuilt/refreshing maintenance schedule as an accepted practice.

they should otherwise be fine to 10k if you went there, in the sense that the seals can take it, but component wear increases substantially. The issue generally tends to be the EGT will exceed 1650°F when over revving a Renesis. Which is going to weaken the side seals to eventually result in lower compression and power output. The heavier weight of metallic apex seals is also going the wear the rotor housing surface more as well as the rotor seal slot and seal springs ski-jumping off sparkplug mountain and then chatter skipping on the landing as rpms increase. Which then adds more of the same decreasing performance result quicker.

the one thing to remember is the rotor only orbits at 1/3 the e-shaft revs. So a 9000 rpm e-shaft rev limit is only a 3000 rpm orbit rotation for the rotor. Just the same, for NA high revving situations the preferred choice would be lighter ceramic apex seals such as Iannetti ($$$) rather than the metallic OE seals. The general point being you din’t want to rev any higher than necessary. Which on your application is going to be 300 - 500 rpm past the peak hp rpm. Which is going to around the limit that REC recommended in the prior post
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I'm aware that lighter seals are the way to go when building a high rpm engine, but unfortunately that doesn't work in my use case. I'll have EGTs available to me, so I'll make sure they stay under control as the revs rise. RB recommends not to rev the FD higher than 8500 on stock seals likely due to seal chatter/float, so I might proceed with the assumption that 8500 should be my limit

you aren’t aware of anything even after I plainly told you, so stop pretending already.
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No, I read your previous message. I don't really want to engage your tendency to be unnecessarily cynical, snarky, and generally rude, but I will cave for now. Your points are as follows:

1. Seals can take 10k rpm, but with increased wear (obviously)
2. EGTs tend to be very high over-revving the Renesis which is bad for side seals (I didn't know this was an established issue, so I'll make sure to pay close attention when tuning)
3. The heavier seals increase wear to both housing and rotor slot (obviously)
4. High rpms cause chatter (obviously)
5. Ceramic seals are better for high rpm engines (obviously)
6. Don't rev it higher than necessary (obviously)

I appreciate you spending the time to write your previous informational message, as it's nice to hear confirmation about what I had already assumed. Unfortunately, that doesn't actually help me pick a starting rev limit. The car goes to 9000 stock, and as you've said regarding the internal wear and high rpm chatter, it might be wise to not allow it to reach the stock rev limit.
For you to "plainly tell me", I'd prefer a numerical suggestion. Renesis street car with RX-7 height apex seals, how high would you suggest it should rev?

My Pettit engine has RX7 FD apex seals. I spoke with Cam about if street porting moved the power band upwards like bridgeport does and if I should change the redline, which Cam disagreed with. He mentioned there's no benefit spinning past 8500 RPMs and didn't mention setting redline lower. Seems like Cam would have told me to change the redline to 8500 if 9000 was super dangerous.

Make sure you get your rotating assembly balanced. A properly ballenced assembly will reduce vibrations at high RPM, increase seal life and is a good idea if you have lightened or machined rotors.