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Old 12-25-2012, 12:41 AM   #1
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Default RX-8 engine for a Miata?

Just here gauging interest if anyone might be looking for an RX-8's drivetrain with ECU and a 6-speed trans.

Although it's running, I believe my Renesis needs a rebuild. It idles rough but it does revs fine. I have been driving it daily. That said, consider it a core.

Anyone here bent on finding a Renesis to drop into a Miata? I'll be doing an engine swap in my 8 and have the leftovers available. Not sure when. Likely this spring. That's why I'm asking here rather then posting in the forsale section.
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Old 12-26-2012, 12:36 PM   #2
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lsx rx8? Yes please. Pics of your project car, and plans for it?
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Old 12-26-2012, 01:54 PM   #3
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just attach another rotor.....I'm sure someone would pick it up then ;-)
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Old 12-29-2012, 02:42 AM   #4
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The rx8 engine is a great engine i love the Renaissance motor. All the engines run hard in the autocross have some reliability problems. Many people are blowing up the engines before 100,000 miles. It aparently needs to have a dry sump pump put in it due too oil starvation in cornering.
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Old 12-29-2012, 02:25 PM   #5
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Originally Posted by old school View Post
The rx8 engine is a great engine i love the Renaissance motor. All the engines run hard in the autocross have some reliability problems. Many people are blowing up the engines before 100,000 miles. It aparently needs to have a dry sump pump put in it due too oil starvation in cornering.
If that were the case wouldn't there be internal damage to the bearing surfaces? Most of them seem to be failing from rotor sealing issues and loss of compression. It's a fairly common problem with the rotary. That failure could indicate an issue with the oil injection pump but not the main engine oil pump used for internal lubrication. Although I could see if a bunch of air bubbles got trapped in the injection pump that would be a problem. In general the rotary doesn't have a good track record. No pun intended. I love the concept. I've owned 4 rotary powered vehicles but I wouldn't trust it to bring my family on a road trip.
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Old 12-29-2012, 06:11 PM   #6
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The Renesis has been the most unreliable rotary engine marketed by Mazda in the last 30 years. Putting it in anything is foolish. Replacing it with anything that will fit is a good idea.
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Old 12-31-2012, 01:35 AM   #7
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The Renesis has been the most unreliable rotary engine marketed by Mazda in the last 30 years. Putting it in anything is foolish. Replacing it with anything that will fit is a good idea.
The tune on the Renesis is the most unreliable tune Mazda ever put on a Rotary. Blame emissions standards not the engine. Run them on premix and there good to go...except for the horrible gas mileage...and the lack of torque...and the noise...and... well anyway my 8 is getting a v6.
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Old 01-01-2013, 03:37 PM   #8
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The tune on the Renesis is the most unreliable tune Mazda ever put on a Rotary. Blame emissions standards not the engine. Run them on premix and there good to go...except for the horrible gas mileage...and the lack of torque...and the noise...and... well anyway my 8 is getting a v6.
The RX-8 would have been quite the success if it had a turbo 4 or a 6 cylinder motor in it.
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Old 01-01-2013, 07:14 PM   #9
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The RX-8 would have been quite the success if it had a turbo 4 or a 6 cylinder motor in it.
It probably would have cost less too. Maybe Mazda wanted to leave that success to the Miata and Mazdaspeed lines. The RX-8 weighs a bit more then a Miata but having owned both, I prefer the 8. It feels as nimble as my Miata and more quiet and comfortable inside. I still miss my Miata. 15psi is fuuun. I'm hoping to get about ~350hp out of this Isuzu engine to give me the thrill I got out of my Miata.

Kia and Hyundai are coming out with (or released) some RWD vehicles aren't they? I wonder if the RWD trend of the 80s and 90s is returning. I'm sure it's government crash ratings and other "idiot standards" that are keeping the fun cars off the assembly lines.
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Old 01-06-2013, 11:10 PM   #10
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Aint no mota if no rota
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Old 01-07-2013, 12:30 AM   #11
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Aint no mota if no rota
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Old 01-08-2013, 04:21 AM   #12
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Cool Rx 8 problems

The dry sump is for clearance and safety margin and low fitment.

The rx8 renesis's motor puts the exhaust through the side plates instead of through the outside of the eng like previous 13b. This creates alot of extra heat buildup on the side seals. After about 100K miles the side seal springs metal fatigues and looses its spring and collapses. The eng then becomes very hard to start when it is warm. Once started exhaust gases get behind the seal and create enough pressure to seal. If you can find a good replacement spring (they are very thin) that would not collapse due to extreme heat that would solve one of the worst design problems of this otherwise nice , compact, light, high revving eng.
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Old 01-08-2013, 06:15 PM   #13
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Originally Posted by old school View Post
The dry sump is for clearance and safety margin and low fitment.

The rx8 renesis's motor puts the exhaust through the side plates instead of through the outside of the eng like previous 13b. This creates alot of extra heat buildup on the side seals. After about 100K miles the side seal springs metal fatigues and looses its spring and collapses. The eng then becomes very hard to start when it is warm. Once started exhaust gases get behind the seal and create enough pressure to seal. If you can find a good replacement spring (they are very thin) that would not collapse due to extreme heat that would solve one of the worst design problems of this otherwise nice , compact, light, high revving eng.
That does help the apex seals run cooler by not passing the hot gasses over the seal. The engine is loud (or use a large heavy exhaust), has **** for torque (aweful in stop and go and local driving conditions), consumes oil by design, it's an inefficient engine (poor mileage), expensive to repair (niche market). They would burn me at the stake if I said that on a rotary forum.

So, who wants to buy it?
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Old 01-09-2013, 12:07 AM   #14
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IIRC renesis motors also suffer more from carbon build up than 13bs. So if you start your car in the garage to move it to the lawn for a wash and you dont let it cool down, chances are you may need a rebuild :(
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Old 01-09-2013, 03:12 PM   #15
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if you start your car in the garage to move it to the lawn for a wash and you dont let it cool down, chances are you may need a rebuild :(
That's most likely going to cause the flooding problem. The engine will load up due to cold-start enrichment. The next time you start it you might flood it. Mazda released a firmware update to help the issue. The carbon problem you might have heard about is carbon causing apex seals to stick resulting in loss of compression.
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Old 01-09-2013, 03:38 PM   #16
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How many monies?
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Old 01-09-2013, 04:14 PM   #17
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Originally Posted by lazzer408 View Post
That does help the apex seals run cooler by not passing the hot gasses over the seal. The engine is loud (or use a large heavy exhaust), has **** for torque (aweful in stop and go and local driving conditions), consumes oil by design, it's an inefficient engine (poor mileage), expensive to repair (niche market). They would burn me at the stake if I said that on a rotary forum.

So, who wants to buy it?
Yes all correct. I cant argue with you. I still like the size of it though and its pretty light. Very finicky though. Anything gets past the air filter and your done. My friend had some small amount of dry chem fire extinguisher get in his intake and pop the motor needed rebuilt. He has rebuilt the eng at least five times. Made 450 at the wheels with single turbo for awhile. Not very long though.
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Old 01-09-2013, 07:40 PM   #18
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Originally Posted by lazzer408 View Post
That's most likely going to cause the flooding problem. The engine will load up due to cold-start enrichment. The next time you start it you might flood it. Mazda released a firmware update to help the issue. The carbon problem you might have heard about is carbon causing apex seals to stick resulting in loss of compression.
I've heard it called carbon build up. 2 second drive, no cooldown and theres a chance ur car wont start. Dont know the full details.
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Old 01-09-2013, 08:00 PM   #19
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Yes all correct. I cant argue with you. I still like the size of it though and its pretty light.
It's hard to find exact numbers for the Renesis but I've read it's 300lb dressed. An Isuzu v6 I'm considering for my engine swap is 293lbs dressed.

Renesis 13b-msp: 300lb 238hp
Isuzu 6VE1 3.5L: 293lb 260hp

The v6 in question produces >200ft-lb at 1500rpm.

A rotory doesn't offer alot in power to weight. It's a heavy little piggy. You can say that the power to size or power to displacement ratio is better for the rotary but it trades torque for rpm and it's actually pumping 2.6L worth if you want to compare it to a 4cyl. A 4cyl has to turn twice for all it's cylinders to fire once. A rotary fires twice per revolution so in 2 revolutions it's firing 4 times or twice it's displacement. A well tuned 2.6L 4-cyl could easily make 238hp so it's not an amasing feet that this "1.3L" engine makes the same. It's just in a smaller package with fewer moving parts and smoother operation.

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Originally Posted by Vilko View Post
I've heard it called carbon build up. 2 second drive, no cooldown and theres a chance ur car wont start. Dont know the full details.
If a rotary is showing those symptoms it is likely due for a rebuild. Wow, has it been 20k miles already?
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