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Author Topic: Rotary question for Simon  (Read 3594 times)
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34hup
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« on: Friday, 14 January, 2011, 02:36:41 PM »

Simon,

Some Rotary advice please. My son has just bought an RX7 167k on the clock 13BT. Has the typical hard to start especially when hot syndrome. Is it likely at 167k to need a rebuild and if so any rough idea what he should expect to pay and if he is rebuilding are there any worthwhile tweeks he should get done while they have the case open.

Appreciate you opinion.

Kym
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The Metalsmith
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« Reply #1 on: Sunday, 16 January, 2011, 12:42:57 AM »

Hi Kym,
              A good N/A rotary would have a few thousand k's left in it but a turbo one would get tired a lot quicker. Everyone would've put their foot down in it: it's hard not to! It'll definately need a rebuild, mate. The hard hot starting is a classic symtom of tired apex seals/low compression.

I don't know how much you want to spend or how hard you want the engine to go, but there's a couple of "tweaks" I'd do while you're banging in new seals.

Porting: A mild port or an extend port would be the limit if you're keeping the turbo. This will allow better airflow through the chambers. All other port types after that will experience overlap during the rotor cycle where the inlet and outlets are open at the same time, blowing the inlet charge straight out the exhaust.

Apex seals: A lot of conflicting views here. Again depending on your performance requirements, the standard 2mm seals from Mazda are high quality but if you want to step up, a set of aftermarket ones from a reputable company are the go. There's no need to go up to the 3mm sets until you're getting serious. Even then I know Pac Performance still use 2mm apex seals in there 13BT race cars. It's probably a good idea to buy a complete engine seal package recommended by a dedicated rotary workshop.

Turbos:
I'm guessing your turbo is the standard factory item. The bare minimum upgrade would be a GT 30 or equivilent but for optimum street performance I recommend a Garrett GT 35/40R, as they are perfectly matched to the 13B.

Further upgrades for a street rotary are un-necessary: crankshaft aligning, dowelling the housings, oil gallery mods. A proper air filter and aftermarket exhaust system including manifold, high flow cat and low restriction muffler will add considerable HP to the package. For the above engine mods and rebuild I'd be looking at around 4 to 6 gorillas max, without the turbo.

I hope this helps out a bit.

     Simon  
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34hup
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« Reply #2 on: Sunday, 16 January, 2011, 05:06:14 PM »

Thanks Mate and yes it does.
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shipy59
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« Reply #3 on: Monday, 17 January, 2011, 02:04:32 PM »

Hi KYM, if you want some firsthand knowlage(spellcheck?) give me a PM and we can run you through some things. i have rebuilt my sons S4 rx7,that was after we fitted a import S5 turbo (14 psi) that he ran lean and killed.And just finished resealing my 79 RX7 that should have had a full seal kit. They can get expensive real quick when you open them up but can be done to a budget if need be.(transeals for seal kit). Check out perthrotary.com
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34hup
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« Reply #4 on: Monday, 24 January, 2011, 04:39:59 PM »

PM sent
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