Ian's 99 post-TB screw re-rebuild. - Page 28 - Miata Turbo Forum -Boost cars, acquire cats.

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Old 05-11-2016, 03:17 PM   #541
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I agree 100%. An LS RX7 would be a phenomenal car to drive, no doubt. But the rotary is so, so cool.
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Old 05-11-2016, 03:18 PM   #542
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Eh.

Quote:
fuel economy of an ‘80s cruise liner and the torque output of a clothes hamper falling down the stairs
The Rotary Engine Sucks

But it makes ian happy and thats what matters
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Old 05-11-2016, 03:19 PM   #543
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there is nothing cool about that piece of crap engine

but doesn't matter, cause the car is still awesome
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Old 05-11-2016, 03:22 PM   #544
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Quote:
Originally Posted by codrus View Post
The **** on the panel? It's pretty simple, really, has three positions:

- low ('fast'): This cuts power to the boost solenoid, so it's only generating mechanical boost
- medium ('MOAR'): Enables power to the solenoid, but the tableswitch input to the MS3 is unchanged so it targets the normal boost level.
- high ('ALLOFIT'): Leaves power enabled to the solenoid and also flips tableswitch, telling the MS3 to go to the alternate boost tables.

The switch itself is a 3-position rotary switch with two sets of contacts in each position.

--Ian
table.switch.buh?
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Old 05-11-2016, 03:24 PM   #545
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table.switch.buh?
Manuals for Megasquirt-3 - Megasquirt EFI
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Old 05-11-2016, 03:25 PM   #546
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It's inefficient, impractical, unreliable, and makes poor torque. But it's unique. It's a different driving experience with a unique sound. It's interesting.

I think it's cool, and I'd have a hard time dumping the rotary if I bought an FD.
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Old 05-11-2016, 03:26 PM   #547
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that tableswitching/boost control thing is really awesome.
always wanted to set that up on my car, always was too lazy to do it lol
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Old 05-11-2016, 03:28 PM   #548
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Ed, you are sounding like a drift tard

Its unique man. Don't hate because its unique.

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Old 05-11-2016, 03:29 PM   #549
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Old 05-11-2016, 03:33 PM   #550
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Quote:
Originally Posted by psyber_0ptix View Post
table.switch.buh?
'tableswitch' is a generic digital input on the MS3 that can be configured to do one of a number of different things. I have it set up to switch between boost target table 1 and boost target table 2, when you flip it the MS starts looking at the other tables.

--Ian
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Old 05-11-2016, 03:42 PM   #551
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--Ian
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Old 05-11-2016, 03:48 PM   #552
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Did you order your pallet of apex seals yet?
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Old 05-11-2016, 03:57 PM   #553
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Don't these things typically last 80k miles or so? I mean, about the same amount of time as Subaru head gaskets?
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Old 05-11-2016, 03:58 PM   #554
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It depends, but from all I've seen/heard its nowhere near that, and despite being problematic also, Subaru hg's are still nowhere near as bad.

But knowing IAN he'll probably use the opportunity to rebuild using way cooler parts and do a fantastic job of it as he does with everything.
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Old 05-11-2016, 04:44 PM   #555
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It varies, there are cars that got new warranty motors at 20K, but there are also cars with 100K on their original engine. I don't know what the median value is, but take the things you read on the Internet about them with a grain of salt. If you believe everything you read on the internet, all the 99 Miata motors are doomed to die from thrust bearing failures, remember?

Rotaries are not inherently unreliable, consider that the 787B won Le Mans not because it was faster the competition but because it outlasted them. The piston engined cars all broke, the rotary went through to win the race. They're also used in experimental light aircraft because, unlike a piston engine, a rotary can't break a rod or drop a valve and convert itself from working to a useless lump of metal in an instant. Earlier generations of Rx-7s didn't have the same evil reliability reputation as the FD does.

So what kills the FD'd reputation? I know of a few things. For one, the sequential turbos have 3 or 4 flapper valves that control which turbo is making boost at what point. Since it's a late 80s/early 90s design, there's an incredible rats nest of vacuum lines to control the sequential turbo system, all of which have boost in them at some point. Boost + vacuum lines means they have a tendency to blow off, which means the turbos won't do the sequential thing properly. This makes for a lot of cars that don't run right, the fix is to replace all those vacuum lines with silicone ones and secure them properly.

Another thing that kills them is overheating. Rotaries are inherently way less tolerant of this than piston engines are, and I've read that the factory cooling system is somewhat marginal.

The big killer is detonation, this will smash apex seals much faster than it blows holes in pistons. The FD is a turbo engine, but one with a late 80s/early 90s ECU that doesn't have much ability to cope with increased boost. It's also got a very restrictive pre-cat in the down pipe, a fairly restrictive muffler, and a small intercooler. Sell the FD to a bunch of kids who loved The Fast & The Furious and they start going to town with bleeder valves, cat-delete downpipes, etc. Being loyal miataturbo.net readers, we all know how important it is to get the ECU right before adding additional boost, right? Need I say more?

There's also an issue with carbon buildup and large chunks of carbon breaking off and jamming apex seals in certain conditions. I'm still researching that one, seems to be more of an Rx-8 problem than an FD one.

The Mazda dealer did a compression test on the car I'm buying, using the fancy Mazda OEM compression tester. (Rotary compression tests are different, to do it properly you need a digital compression tester that can identify the three faces of the rotor and sort out which is which). You need to do the test while the engine is hot (it seals better when cold, so those numbers can be misleading), and this one is good. Barring abuse, failures seem to be progressive rather than catastrophic, so I'm hoping that means that this motor should live for a while. Keep in mind that I'm not going to put a lot of miles on it.

I have been watching rotary engine rebuild videos on youtube though. Wankel engine ****!

--Ian
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Old 05-11-2016, 04:51 PM   #556
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This is an interesting video. It's an hour and a half long, but they build an entire 20B start-to-finish in it:


--Ian
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Old 05-11-2016, 04:53 PM   #557
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all of that is true. but I was more talking about my cousin who had his engine rebuilt on 93 bolt on fd3s 3 or 4 times within a period of a couple years. but he may be partially one of those ricer kids so you might be right

and yes, his was overheating or close to it, very often.
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Old 05-11-2016, 08:16 PM   #558
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Heat has always been a design problem with a rotary. The "firing" stage of a rotary never gets a cool charge like a typical 4 cycle engine. That part of the engine is a constant hot spot leading to excess heat.

A friend of my father's used to campaign in SCCA a GT3 (?) class FD against C4 vettes and whatnot of that era and while he said his corner speed was much faster than competitors, straight line power was weak and he struggled to even finish a race without a mechanical failure (turbo failure due to excess heat was the main culprit).

It is no secret that while the car has an amazing history for handling, the rotary engine was/is always a let down. Having owned a proper LSx RX-7, I find it hard to believe there is a valid argument on why the rotary is superior.
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Old 05-11-2016, 08:26 PM   #559
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It is no secret that while the car has an amazing history for handling, the rotary engine was/is always a let down. Having owned a proper LSx RX-7, I find it hard to believe there is a valid argument on why the rotary is superior.
The point you're missing is that I don't want it to have the superior power plant, I want it to have the original power plant. This is not a rational purchase (how many 5th cars are?)

I've got a 340 rwhp Miata (which is what this build thread is really about), I'm not going to take the FD on track.

I'll also point out that doing an LS3 swap properly (no junkyard/ghetto conversions for me, thanks anyway) is a $20K+ proposition, more than doubling the price of the car. It's also a huge project undertaking (see previous comments about not wanting a second project car) and would make it impossible to get past the smog ***** here in California. No thanks. If I wanted a 2-seater LS motor car I'd have bought a C5 for way less money out the door.

--Ian
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Old 05-11-2016, 08:49 PM   #560
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Yeah, nobody is saying the rotary is superior. It's just cool. Part of the RX7 experience. LS3 would be superior in every single way.
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