I bought this for a turbo rebuild. It's an FD rotor. I recieved it literally fresh out of the engine, still dripping with fluids. I cleaned off the carbon and found it had been detonated..or at least that's my assumption

Is it usable?



One thought I had, can I swap it to the other housing so that the damage is facing the opposite direction. So that the momentum of the engine is always pushing the apex seal away from the damaged area rather than into it?

 

rotor is done imo

 

time for some 3mm apex seals.

 

I would swap it to the other housing. As long as the apex seal moves through the groove smoothly and the clearance between the apex seal and groove is at least 0.002" its within specs and will function great.

Check this out: http://www.rebuildingrotaryengines.c...leaning_rotors
I would give it few passes with my honing stone like the one Rob uses in that video. From your pics I think there is a little burr?

 

Seller is replacing the rotor, so it won't be used...

It's for a turbo build. I've read to stay away from 3mm for turbo.

I've watched most of the vids over there, good stuff.

 

Yea, it was really nice of Rob to take the time to share his knowledge. I've learned some good tips from his videos.

 

Where have you read this? Everything I've read has been in contrast to this (3mm doesn't seal as well but resists against detonation better)

 

the 3mm is stronger, but 2mm seals better.

so what does better sealing get you? higher compression = more power

one of the root causes for detonation in the first place is the hot exhaust gas getting into the intake charge. better sealing minimizes this.

or in other words, all else being equal, a 3mm engine will detonate first, and detonation will break the 3mm seals too, if its serious

 

Thank you for clarifying. I understood what I read, but couldn't have explained it like you did.

 

lol, thanks! version 1 didn't make sense, good to know v2 does...

 

As a general observation from a first time engine builder who is trying to soak in all the pros and cons involved in choosing parts this is what I've learned.

Everything is a trade off and there is no ideal 100% guide to building a indestructible engine. Everything is contextually based on what your engine is being used for.

3mm and 2mm apex seals is a perfect example:
-2mm seal better and have better compression
-3mm are stronger.... detonation aside

So you have to choose if you want lower compression and possibly more longevity or higher compression and possibly a shorter lifespan. But then the whole detonation thing throws a monkey wrench in that.

This is my first turbo I've owned so being relatively new to all this, on top of being new to engine building, and having limited tools and knowledge for fine tuning fuel, timing, etc...I'm at a greater risk of detonating.

My car is in my signature. Before detonation and starting my rebuild I had upgraded exhaust, intake, and fuel. Once the rebuild is done I'll have an Rtek 1.7. So I should be good for controlling my mild upgrades.

 

The three piece stock Mazda apex seals seal the best / make the most compression / make power.

Building an engine to resist detonation is a backwards way of thinking.

If you don't figure out why the engine detonated in the first place you will be rebuilding your rebuild very soon...

 

3mm seals actually increase wear so they reduce longevity over the 2mm seals.

i don't have an issue with overbuilding an engine with 3mm seals, i used to think the same way that going 3mm was overkill and a bandaid but at the cost of definitely blowing a rotor and housing versus just an additional small bit of wear isn't a huge issue. but there is additional cost and if someone isn't shooting for over 400 WHP i don't see the need to try and push 3mm seals on people.
regardless of everything people say, cars won't always be in 100% tune 100% of the time unless you are a tuner and have your car setup for doing a tuning session every single time you drive it, at which point it becomes un-fun to drive. even in which case, a sudden failure can still happen, no matter how careful you think you are, parts fail.

 

Nothing backwards here, I know why it detonated. I was running 3" exhaust and a custom TID, I had upgraded fuel pump and secondary injectors...but hadn't added control for fuel or timing. I was actually waiting for the Rtek S5 turbo chips to come out of beta testing. With the rebuild I'm also adding the 1.7 chip and a manual boost controller.