Originally Posted by Brettus (Post 4634257)

There have been a few threads on the subject with most opinion saying the lubrication of the apex and side seals becomes an issue . Your one wore out or ?

Originally Posted by RIWWP (Post 4632951)

Wait, so you want another engine that has less power than the engine that doesn't require any extra work to replace? I am honestly trying to figure out your reasoning for doing all the work to put in a slower engine, rather than just getting another Renesis..


The RX-8's ECU will not be able to run a V6. Different injector behavior, different spark count, different spark sequence, etc... You will need to use another ECU, which will mean that all the existing RX-8 electronics will need to be removed or completely re-written with custom firmware.



Have you measured the difference in where the output shaft ends up being placed? The Renesis exits from the center, a V6 exits from the bottom. Same dimensions of the total block means you have a much lower transmission mounting location, or the entire engine has to sit higher, potentially creating different problems.


They did, it's called a Mazda6. "RX" means Rotary Experimental, so anything else in the chassis is called something else other than "RX".


Physically fitting the engine in a location is perhaps the easiest problem to solve in any engine swap. For the RX-8, the significant additional problems will show up with the electronics, which is seperate from the wiring problem.

I get the appeal of engine swaps, though I struggle with your choice. Your goals are met by the engine that will take you less than a day to install, but you are instead choosing to install an engine that will require significant amounts of work and you will never recoup the costs of.

Originally Posted by KFC (Post 4634829)

I'm glad you asked because I love the conversion, I've had it running on my car for over a year now. I never intending it to be the tidiest installation as I knew it would be coming off with the engine. The system is AEB. I bought this one but at £625 minus the tank.
LPG gas conversion kit Range Rover Super Charger V8 sequential injection AEB

The only tricky thing about the installation was splicing into the cars loom for the injectors. The lpg ecu is now the master, it tells the cars ecu when to go on petrol. On start up it needs to use petrol until the threshold is met on change over. As in, when the water temp reaches 30 degrees C, the revs are over 1200 rpm, the lpg ecu changes over seamlessly. You can't feel it, well, only a tiny bit but you have to be waiting for it.
At 1200 rpm the engine is so smooth anyway. I'm not sure the time frame but it changes 1 injector at a time but I think its all six over a second or 2.
The engine coolant water runs through the vaporizer as it gets very cold and can freeze if the you were to change the threshold temperature lower than 30C.

In the summer (25c to 30c) in changes over nearly instantly or a 1/4 of a mile. In the winter (15c to 0c) it can take up to 3 miles so it's not to bad. I've thought about putting in block heaters to plug in for an hour just to see if it changes over a lot quicker.

The tank sits in where my spare tire goes. In the 24 years of driving, I've only ever had 2 flat tires, I carry a tire repair can if I get a flat.
the whole installation took me 4 days so I expect it to be a bit quicker putting it on the 8 as I know what I'm doing with it. Oh, I recently put a flash lube kit on it, meant to give added protection to for the valves but it's not needed on this engine, I just thought it would be good to have it as it's cheap.
I hope this helps.

Originally Posted by BigCajun (Post 4634847)

That's very interesting. I've heard of it, but never really looked into it, so I admit I'm ignorant of all the pros & cons of it.
It's one thing to read about it, but another to see it used in normal everyday circumstances.
How does the LPG meet the octane requirements of the Renesis?

Our premium gas is currently on a price decline, but it's only a matter of time before it goes back up.
That is something i will definitely be reading up on over the winter.
Thanks for the link.

Originally Posted by RIWWP (Post 4634862)

BigC, octane matters for preignition from the heat of compression. Think about what happens when a substance reverts to a gas from a liquid (ie, liquid propane gas)... :)

Posted From RX8Club.com Android App

Originally Posted by KFC (Post 4634866)

There are YouTube clips of RX8 LPG conversions. They work, sertainly can't shorten the life of the engine for the amount of years you plan on having the car for?

Originally Posted by RIWWP (Post 4634868)

I'd bet LPG would, on average, increase the lifespan of a Renesis by 50-100%. Gasoline as a fuel, and it's attributes, are significant factors in almost every critical reliability problem the engine has. Virtually any other fuel would be better, with alcohols and lpg better for cooling reasons, diesel better for lubrication and performance reasons.

Edit: and hydrogen for emission reasons

Originally Posted by RIWWP (Post 4634862)

BigC, octane matters for preignition from the heat of compression. Think about what happens when a substance reverts to a gas from a liquid (ie, liquid propane gas)... :)

Posted From RX8Club.com Android App

Originally Posted by RIWWP (Post 4634911)

...and no carvon to deal with.

Originally Posted by RIWWP (Post 4634911)

...and no carvon to deal with.

Originally Posted by SiNfidelity (Post 4635163)

Seeing as carbon is the most common renesis killer, u are correct. My last 2 engines had major carbon issues, and another I had after 50k km from rebuild still had more carbon caked on my rotors than is right & and I thrash the thing 7-9k rpm every gear change nearly every time.
I'm going lpg on my 20b conversion, but not dual fuel. (Dual is rubbish)
U run straight lpg, u tune the car for optimum performance (including different plugs) on said lpg, and because it's straight lpg it runs way more efficient, in fact almost the same bang as 98 per Lt and for those out there who disagree with that then I say ur not doin it right. And of course, higher octane=more boost, easier tune-ability, and at half the price of 98.!!
U buy an aluminium tank which is 50% lighter than conventional lpg tank. U remove the factory tank to cut down weight. Mount the new tank in the boot as forward as possible- mines gonna be 60lt usable Lt.
I will adapt/modify the omp for 2stroke and my lube is sorted.

Sht did I just high jack the thread??! Soz. Saw an opening to preach lpg.

Originally Posted by RIWWP (Post 4635260)

No, it's a misconception that oil is the source of the carbon. If you look at pics of rotors that have come out of dead engines, you can see that the rotor is cleaner where the oil injection was hitting it. Virtually all of the carbon buildup in a rotary, or any other gasoline engine, is from the gas alone. We want to encourage people to switch to 2-stroke oils simply because they show even cleaner rotors where the oil hits them, and the carbon that is there is a bit 'softer'.

Originally Posted by KFC (Post 4635247)

I thought a lot of the carbon build up was caused by the oil injection? I know why carbon build up happens but isn't the oil a contributor? How are you going to stop the vaporizer from freezing up if you run it only on lpg from cold? It does happen. When mine is on lpg, it's either on or off, unlike some systems inject petrol 10% of the time while lpg, crap. Also, where do you find the ally tanks? Are they still certifiable?

Originally Posted by SiNfidelity (Post 4635608)

vapour inj system doesn't have this problem.

Originally Posted by BigCajun (Post 4635628)

Perhaps you should start an LPG discussion thread.

Originally Posted by RIWWP (Post 4635626)

Sinfidelity, I was replying to KFC on my last reply, not you :) Your understanding of the carbon issues is correct

Originally Posted by 9krpmrx8 (Post 4633717)

I am certain I have more experiences than you do with the Renesis. I have torn apart a few and have had four of my own so I am well aware of how reliable and how unreliable they can be. They can fail in a number of ways, just like any other engine, especially when you start making serious modifications (such as kickers turbo dreams). But as RIWWP pointed out, we are not talking about just engine reliability.

You sound like you have your mind made up so rock on. But I won't hold my breath, these type of swaps never get finished. The only legitimate piston engine swap into an RX-8 that I can think of recently that looks to be a solid build is north $25,000.00 and is not even finished yet.

Originally Posted by KFC (Post 4636871)

-and do a swap over a weekend.

Originally Posted by KFC (Post 4636871)

Good for you. :rollingla
I love clever engineering and I can see the appeal with the rotaries but they have a fundamental weakness, the corner seals... A massive stress raiser..
Every single designed engine or highly stressed moving part has has a curved or round surface. It's a shame because it would be used more.

For me it's far too expensive to run on a daily basis, 25mpg at the best and just doesn't sound right. The cars heart is the engine, if it doesn't sound cool then it's a let down. How many films use cars with great sounding engines?? Can't say they use the RX7 or RX8?

Cars must be very expensive in the US if someone actually spent $25000 on a conversion?? I bought mine with a dead engine for $600. Everything else I spend money on, I should be able to get most of it back if this fails, ebay is a good friend to me, ha ha.

I've had the bumper removed for a while, much easier to work on while I'm using the mock up eengine. Oh, the real engine I'm putting in is coming out of my 18 yr old MX6 as a cheap test, if it's good and works well after 6 months then I'll rebuild my spare and do a swap over a weekend.