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 Post subject: Rotary engine question
PostPosted: Wed Mar 20, 2019 10:45 am 
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Joined: Tue Oct 08, 2002 10:17 am
Posts: 2669
Location: Innsbrook, MO
OK...…..this is a really strange one.

Building a 13B powered miata for Chump...….. Got to shorten the oil pan for chassis fit...…..so planning to use a 3qt accusump with check valve …..maybe 2 of them in parallel for 6 qts pressurized oil total......not sure how good of a job can be done on baffling with so little volume. So here is the real question.

IF someone accidentally left the accusump valve open during engine shut off (who hasn't done that?) and the 13B crankcase took the 6 qts of oil........could any damage occur upon restart?????. I'm thinking some kind of hydraulic lock due to oil leaking by a rotor seals but don't confine your imagination.

I'm no rotary guru so please enlighten me. Ears open! Jay

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Thanks, Jay Lutz

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PostPosted: Thu Mar 21, 2019 7:10 pm 
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Joined: Thu Dec 10, 2015 12:55 am
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I do not think you can hydraulic lock a rotary from the bottom. Any oil would be washed out of the exhaust ports. I think It could from the intake ports but you would have to pour it in the intake. And the ecentric shaft does not sit right above the oil in the pan so it could not churn in the oil of the pan like a Piston engine will. Oil starvation is not really a problem I know of even with stock pans and no accusump etc.. I have always run a baffle to help get the air out.

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Rob Garrison

FP Mazda Miata
IT7 RX7
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PostPosted: Fri Mar 22, 2019 5:19 am 
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Joined: Mon Nov 23, 2009 12:25 pm
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Have you considered a custom oil pan? JPM is finishing up a 13B in an RX-8. He used the FC motor mounts so the stock pan was the lowest point on the car. I ended up getting a custom billet pan from here.

https://www.built2apex.com/product-page/13b-fc-race-pan

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PostPosted: Fri Mar 22, 2019 9:14 am 
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Not sure quite how much oil everything is supposed to hold, but my 13B has a ~1qt size external filter plus the cooler.. when I do an oil change, I pull the hoses and dump all that, then pour 5qts into the engine.. crank for a while to prime the system and then start it up and run for a while to purge any air. then I use the dipstick to top things off. maybe 5.5qts per change? I don't really know since I always use partial of whatevers left in bottles from previous change(s)..

but I'm running the stock pan, no baffling or accusump or anything.. ain't blowed up on me yet!

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Matt Blehm
Houston Region
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PostPosted: Mon Mar 25, 2019 8:50 am 
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There is no difference in the Keg size of an RX8 motor compared to any RX7 motor. Big difference is the RX8 has the oil level stock above the top of the oil pan sealing surface. RX7 is below. If case is sealed right when built you can hold the same oil with a shorter pan and adjust your marks on the dip stick. Yes, you are way over engineering this to add a second accusump. :D


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