Over 25 sprint races and numerous time trial, qualifying sessions and practices on the new s2 motor now. Best motor I've had so far (my fifth motor sadly). Best power, runs smooth, no problems at all. This is the first season I've started and finished every race. Hopefully this great motor will continue to hold up so well.

Well... sadly the motor blew last weekend. I was hoping to get more out of this new motor - it seemed so strong. A coolant seal blew big time which blasted the coolant out and coolant now leaks into the combustion chambers as well. So this had nothing to do with the apex seals or lubrication from pre mixing. Nevertheless, I never overheated this motor and it was running super strong until suddenly it started blowing out all its coolant during Sunday's qualifying. Disappointing these motors don't hold up better. I suppose almost two years isn't so bad for a hard worked race motor... but still... maybe time to switch to a Miata?


The motor should be easy to rebuild I think.

Zoom Zoom Boom. No chance the heat from extreme internal friction due to the lack of an OMP caused any issue? Please post tear down pics.

That seems like a stretch . Souns like he got a good run from the engine to me.

Re the coolant seal fail : ... i wonder if extra dowelling would solve this . In my FI engines that weren't dowelled i see evidence of housing flex ...this could be the issue ...........................

An engine per season is too rich for my blood :)

I think racing is just tough on these motors in general. My motor failures since I started racing the car in 2008:


Motor 1 (original) - coolant seal failure
Motor 2 - failed on start up due to incorrect assembly by builder, oops
Motor 3 (used) - some kind of bearing failure
Motor 4 (rebuilt by pineapple racing) - corner seal failure
Motor 5 (rebuilt by local guy) - oil seal failure
Motor 6 (brand new series 2 motor) - coolant seal failure


So as you can see I've seen it all!


I could give a long list of 13B turbo motor failures from my previous rx7 race car and other piston motors too... racing is a tough life!

Magnus - you seem the type to be detailed in your endeavors... any chance you have the hours logged on each of motors 4-6? I imagine (1) had more street miles, (2) obviously doesn't matter and (3) was used and in unknown internal condition...

It would just be fuel for speculation, but I would find it interesting...

Eh... I'm not as detailed as I should be. Motors seem to last me at most two years. I do a lot of racing... probably 60-70 hours of track time each year. I figure the latest motor - a brand new series 2 motor - lasted about 80 hours of track time. I suppose that's not bad in the world of racing. Motors 5 and 6 have lasted me the longest. Maybe I'm just getting better at not abusing the car! Motor 1 I used to get it too hot all the time because I had the stock radiator so I was not surprised to have a coolant seal failure. Motor 6 I kept conservatively tuned and engine temps were good at all times so I was hoping it would last longer.

80 hours doesn't sound terribly bad when always being driven at the limits - if it's rebuildable and the internals are reusable, that would be a plus as well!

Pretty interesting data.

Hmm, I had 23 track days which is about 50-60hrs on my original s2 engine, along with 51k miles when it failed. Although not great, looks like that is not terrible either.

After 1 year I have 23hrs on my pineapple rebuild, along with 14k street miles.

Hey Magnus,
sorry to bring up this old thread, but recently I ran my car overheating(So Disappointed, My Fault Though) and I was planning in swapping over the s2 engine in my s1. I was just wondering would you recommend the swap as a daily and does all your electronics work? I know everybody going to say, just put the correct engine Blah, blah, blah... I love my car and the renesis, but I want it to be more reliable, and you also pulled some impressive numbers on the dyno.

Honestly, I think you would be better off having your s1 engine rebuilt...

Any reliability benefit of the s2 core engine is really down to the oil injectors. Since you can't use those in an s1, you won't get this benefit.

There's no difference in power between s1 and s2.

AND, I doubt you want to have to premix every tank driving on the street.

The reason to do this when this thread started was that you could buy a brand new crate s2 motor. Those are no longer available.

So, if you want more reliability, get your s1 engine rebuild by someone reputable, consider having it balanced if you are going to drive it hard. Maybe add a Sohn OMP adapter, and stay on top of maintenance (coils, plugs, oil changes).

I agree with above. Premix on a street car is too much of a pain. Not really any significant reliability improvements.


S2 crate motors are still available from Mazda Comp, but officially they hold them for the Star Mazda racers.

Yeah, thank you very much for the reply. Yeah, I decided on rebuilding mines with OJImports and premixing whenever I can to make that baby last. Definitely getting that sohn, thank you so much. I hope I get to pull the same numbers as Magnus on the dyno though. Wish Me Luck!

Magnus, what did you use for premix? Looks like I may be giving this a try...

EDIT: Also, 1oz premix / gallon gives a ratio of 128:1 fuel to oil. That seems ok if it is a supplement to a working oil injection system, but is it really enough by itself?
50:1 seems more typical for a 2 cycle engine. I understand that uses the oil to lube more than just the piston rings though, so maybe 100:1 is a good ratio to shoot for in a rotary?

EDIT2: Did some searching... I'm thinking a good 2 stroke oil at a 100:1 ratio and then monitor the condition of the plugs. Less seems to work for folks as well (i.e. 128:1 seems ok with no OMP, 256:1 with the OMP). Still interested in what you used Magnus :-)

Yeah he premixed and removed the OMP. But it is a hassle to premix all the time if it is a street car. Better off with a Sohn adapter IMO

Yeah except you can't run a SOHN adapter on a Series II Renesis.

Sorry I wasn't specific enough, better off running a s1 engine w a sohn. Unless, its a track only car

I would have to agree that a Sohn is a good idea on a S1 engine.


Most racers seem to agree on 1 ounce per gallon premix if the oil injection is removed. Honestly I don't really know if more is better but I can tell you that my motor failure (coolant seal) was entirely unrelated to anything that has to do with the premix or oil injection... so 1 ounce per gallon seems to work.


I think any good quality two stroke oil is good. I get a good deal on TORCO and their product is of excellent quality so I only used TORCO synthetic pre mix.

Thanks Magnus, very good to know.

And yes, I understand about the downsides. The reason for me going down this path is that I just happen to have a good s1 chassis and a good s2 core that I would like to turn into a track car.

I run Idemitsu premix when on track in an S2 as a precaution to supplement, haven't had any issues yet.

Idemitsu is not terribly expensive either - something like $70-75 per case or so from Mazdatrix (plus shipping). at $6 or so per quart, that's an additional 19c per gallon of fuel if you're running 1oz per gallon...

So, I got my transplant running and tested it for 2 days on track. Worked flawlessly. Thank You Magnus for posting such a clear guide.

Couple of notes:

1. I made a small bracket out of a strip of aluminum to bolt down the OMP in the location magnus shows. Mine ended up pretty closest to the clutch bleed valve, so be careful of that.

2. Since I had the oil line from the s2 oil injection feed, I decided to cut and plug that, rather than crimping & welding the tube on the housing. My first attempt failed, so make sure whatever you do here can withstand some heat and pressure.

3. I used the s2 gasket between engine and transmission, since it was already on my s2 engine. In retrospect, I think it would be better to match this gasket to the transmission. Since I left the s1 transmission in the car, I should have used the smaller piece that goes on the back of the s1 motor. As it is, I think it is fine, but I did struggle a bit to get the transmission bolts correctly torqued up.

One additional note

4. The s2 motor has a different oil pan which does not appear to be as thick as the s1, and the chassis has a metal undertray to protect it. Without drilling and tapping holes the undertray won't fit on the s1. I'm not sure if this is a cause for any concern or not, but I'll be trying to avoid any off road excursions just in case :-D

Just saw this:
https://www.rx8club.com/series-i-eng...3/#post4786763

If it works, then we can leave the OMP out of the engine bay. Will try it when I get a chance...


Edit: Tried this and I was able to remove the CEL, but the engine stayed in limp mod until I plugged the OMP back in.

I remember looking this thread over before beginning my S2 swap (full power/drivetrain swap including all electronics) into my 2004 S1. I wasn't sold on the idea of blocking off the OMP and running premix only which is why I chose the route I did, but now that I have a daily RX-7 that only runs premix with no OMP, now I think this route might've been the better option. I do 1 Oz. per gallon in the SA and it's really not as unbearable as some may think for a daily driven car (like those that buy 1 quart of 2 stroke at a time rather than ordering a case of 12 from mazdatrix like I do). But I think that the route I chose was a good learning experience, I just wanted the car to run as a stock series 2 would is all and the entire swap is pretty much direct bolt on and drop in (meaning no modification to anything on the car to fit the parts, they all just bolt right up).

But anyway, thanks for posting this thread, it played a large role in deciding to pulled the trigger on my build. And yes the electronics swap is the biggest pain in the ass ever, if you want a series 2, just sell your S1 and buy a damn S2, they're more than cheap enough to where the benefits of the swap don't justify the work and effort that goes into it vs. the cost of a running S2

Link to my build thread: https://www.rx8club.com/rotary-swaps...-my-s1-261187/

https://cimg2.ibsrv.net/gimg/www.rx8...c601a81ea2.png