MagnusRacing

iTrader: (2)

So... I have this factory new series 2 motor and a seriers 1 RX-8 race car.

With about $1000 of extra parts I can adapt everything so that it bolts into my race car BUT there is no way to swap over the oil metering pump or to switch to the new style series 2 oil metering pump.

Since this car is for racing only I don't have a problem premixing my fuel all the time and elminating the OMP.

HOWEVER, I know from experience that the stock ECU will go into limp mode if it does not detect the oil metering pump.

Any ideas? Strap the removed series one oil metering pump somewhere but plug it in to the wiring harness? Would a non operational OMP make the ECU happy?

Can the ECU be reprogrammed to no longer look for the OMP?

Any advice is appeciated! The only cars I know running a Renesis without an OMP use an aftermarket ECU.

dannobre

iTrader: (3)

ECU will function fine with it plugged in and zip tied out of the way.....

There is some talk about the pump helping with side seal life...even with pre-mix

If you don't use the DBW throttle you don't need it either.... ;-)

MagnusRacing

iTrader: (2)

Thanks! One more question for anyone who is knowledgable about the series 2 motors: There is an "oil control valve" on the front housing of the series 2 motor above the oil filter. It has an electrical connector. Can this valve be left unplugged?

EDIT: Further research shows that perhaps this oil control valve simply directs oil to the oil metering pump, which I will not be using. So it should be ok to just block this off right?

9krpmrx8

iTrader: (46)

This is a series II engine, you cannot run it without the oil metering pumps. And even if you could you would not want too. IIRC some of the S1 Renesis race guys tried it and the engines failed quickly. You could use the band new S2 engine to build a new S1 engine using some S1 parts but it would take some retapping of oil pan bolt holes and some other things.

MagnusRacing

iTrader: (2)

I don't understand why you can't run it without the oil metering pump? It's not any different inside than the series 1 motor, right? I'm using all series 1 parts on it so it'll be run with a factory series 1 ecu.

My understanding is that the entire Star Mazda racing series (open wheel) uses a Renesis with pre mix only with ok results. The run a series 2 motor with an aftermarket ecu and pre mix only.

The mother's/mazda/robert davis racing team has run an RX8 in enduro racing for years with only premix.

Does anyone know why premix only would be insufficient for a Renesis?

RIWWP

iTrader: (2)

The OMP's side injector's primary purpose is to cool. The lubrication is a secondary benefit.

The basis of that belief is from teams that ran without an OMP (S1 engine), premixing only, and had side seal springs warping, pushing the side seals out of position until they clipped the exhaust port and boom, the motor blows. This was occuring after only a few hours of racing on each engine. They reconnected the OMP, which has an oil jet dumping oil onto each side seal, and the motors began lasting significantly longer. The prior peripheral port engines didn't have this problem because they aren't dumping huge amounts of exhaust heat immediately next to the side seals, only the apex seal.

There are some here on the forums that disagree with this of course, and I'm sure they will show up before long. If the Star Mazdas can run without an OMP, then perhaps you may be able to go digging for information on what other change exist in the engine in order to accomplish that. Renesis engines sourced from street cars have not been able to replicate the OMP-less durability.

Considering the Star Mazda engines are apparently sourced directly from Mazda, it wouldn't be beyond the realm of possibility that the engines are simply different, and use a different method to cool the side seals.
Perhaps it's something that they discovered after the RX-8's release and were able to change for the Star Mazda engines?
Might that change also have made it quietly into the S2 without us knowing?
Would the change have not made it to the S2 engine for some political, regulation, or PR reason?

I don't know the answer to these questions, but if you could discover them then maybe you would have your answer on how to proceed. If it was my car though, I'd have to weigh the risk and cost of blowing the engine after only a few hours of race time against the cost of getting an OMP system to work.

MagnusRacing

iTrader: (2)

Thanks for the info! I'll take this into consideration.

However, the OMP doesn't really inject onto the side of the rotor. Both the oil injectors (or all three in the case of a series 2) inject their oil directly onto the face the rotor (apex seals). How is this cooling the side seals?

Now was this side seal failure after a few hours of CONTINUOUS racing? Or a few hours of total motor race time broken into short sprint races? I am aware that side seal failure is common if a Renesis is pushed hard for an extended period, regardless of OMP etc.

As far as the motors for the star racing series they are simply a 100% factory series 2 motor right off the factory assembly. No different that in any other series 2 RX-8 street car. Of course they have a different ECU, intake, exhaust, transmission etc but that shouldn't matter.

RIWWP

iTrader: (2)

Re: Race length
I believe their races were 2.5hrs in duration typically, but I am not sure.

Re: Star Mazda Motors
I wouldn't be so sure. Quite a bit of annecdotal evidence to the contrary. Not enough to prove it, but not enough to disprove it either.

Re: Injector location
Take a look at this series 1 rotor and see if you can judge for yourself where the oil is actually being injected, and where the cooling/lubrication effect is taking place:



It may be also hitting the face of the rotor, but it's pretty clear to me where that oil is getting.

(I'm struggling to find the Series2 rotor comparison)

9krpmrx8

iTrader: (46)

Hey, that's my rotor Also relocating the S2 Renesis oil metering pumps and leaving them plugged in would be a PIA I think.

MagnusRacing

iTrader: (2)

Yes, but remember I'm using all the Series 1 parts and ECU and using ONLY the base Series 2 pumpkin/short block. So I'll only need abandon the series 1 OMP somewhere and keep it plugged in. I don't have the series 2 OMP at all - didn't come with the motor.

In regards to using Premix Only I just spoke with Robert Davis (director of marketing for Mazda USA and an avid racer I often race against) and he confirms that engine longevity in their Enduro RX-8 that use Premix ONLY is improved over using the OMP. They have run this car in the 25 Hours of Thunderhill repeatedly.

On a side note I know that they run their RX8s with a rich tune to keep the exhaust temps down and never rev past 8300 rpms so this probably helps with side seal life more than anything.

So, I think I've reached my decision. I'm going to go ahead and put the Series 2 motor into my RX-8 which I can do pretty easily. Just need some series 2 oil lines etc as they are different than series 1 and connect in different places. Everything else Series 1 should bolt up. I will then run no OMP and premix.

We'll see how it goes! At worst I'll be doing some research for the forum!

RIWWP

iTrader: (2)

This is most likely the primary factor. If you can keep the EGTs low enough, then the side seal problem does diminish. I wonder if they made the decision to limit the revs and force the EGTs lower specifically to be able to run without an OMP? I would suspect so. Chicken or the egg question there.

I also wonder on the longevity of OMP + Premix, since they aren't mutually exclusive like your comment suggests.

9krpmrx8

iTrader: (46)

I don't believe that at all. But what do I know. I would also think you would need to use the S1 front cover. I just don't see how you will address the oil lines, OCV, etc that feed the S2 oil metering pumps.

9krpmrx8

iTrader: (46)

Oh and the S2 engine has more than one APV position sensor and some other sensors that the S1 does not but I guess that won't matter since the S1 ECU won't be looking for it. But, for example the oil pressure sensor on the S2 is located in the S2 oil metering pump so I am not sure if the S2 engine rotor housing is tapped for the oil pressure sensor.

MagnusRacing

iTrader: (2)

Can't any oil passages to the series 2 OMP just be blocked off? The oil cooler lines certainly attach in a different place but this can be addressed by using the series 2 oil cooler lines.


Good point on the oil pressure switch. I imagine I can tap the motor somewhere to get an oil pressure reading if the series 1 location is not available.

9krpmrx8

iTrader: (46)

I am not sure on blocking them off but I would assume you can, I am just not sure what that would do. I have yet to find a lubrication diagram for an S2, but I do have an S2 FSM so I will take a look tonight.

logalinipoo

Water injection through the omp injectors to keep the side seals happy.

MagnusRacing

iTrader: (2)

Ok, so when I finish the swap I'll start another detailed thread but I took the Series 2 motor out of the crate and test fit some series 1 parts onto it. Looks like, other than the OMP or course, the swap should not be too tough.

Here are the issues and how I intend to address them:

1) No way to run an OMP with series 1 parts on a series 2 motors. I will eliminate the OMP and premix. I will plug the OMP oil feed line. I will abandon the series 1 OMP under the hood and leave it plugged in so keep the series 1 ecu happy.

2) Oil pressure sensor - this will need to be relocated as the series 2 rear plate does not have a provision for it. I intend to tap a new fitting on the series 2 motor near where the series 1 oil filter would have been. UPDATE: It appears that the Series 2 crossover tube that goes where the Series 1 oil filter would have been has a threaded fitting (Currently plugged) that will work perfectly for the series 1 oil pressure sensor, how considerate of mazda!

3) Oil cooler lines. I will have to buy or obtain all new series 2 oil cooler lines since the series 2 motor has a completely different location for these. This will cost about $1000 if bought new.

4) Crank angle sensor. The series 2 crank angle sensor is in a different location. HOWEVER, it appears that mouting the series 1 trigger wheel on the series 2 motor exactly compensates for this new location. Easy fix!

5) Ignition Coil mounting bracket. Some interference here due to the revisions to the front cover for the series 2 oiling and OMP system. However it seems a bit of bending or slight fabrication can address this pretty easily. UPDATE: Using the Series 2 coil bracket (a $20 part) looks like it will address this perfectly.

6) Oil Dipstick and tube. I will probably just install the series 2 dipstick tube and dipstick as they are only about $30. The series 1 dipstick might work as I doubt there is a difference in oil pan depth but for $30 I suppose better safe than sorry.

There may be a few other things such as the low oil lever sensor that I have not inspected yet.

I test fit the series 1 intake, exhaust, thermostat housing and oil filler on the series 2 motor and no problems there.

A few pictures of the factory new series 2 short block are attached for your viewing pleasure. Notice the extension of the oil pan on the passenger side. I suppose the extra oil capacity will be nice!

Redshift

iTrader: (2)

Why not just install a SOHN adapter and inject the premix that way?

RIWWP

iTrader: (2)

1: Because it is a series2 engine. There is no SOHN developed yet that can physically fit to the S2 engine. Different dimensions, mounting plate, etc... If you look at SOHN's website, you can see that he has one for every other iteration of rotary, presumably the low volume of the S2 kept him from developing one.

2: You don't "inject" premix anyway. Premix is a state of gasoline with a specific concentration of 2-stroke oil in it. "Injecting" premix would mean injecting a gasoline/oil mix. 2-stroke oil by itself is just that, 2-stroke oil. It isn't called premix.

Redshift

iTrader: (2)

1. Indeed you are correct. Just looked now. I had honestly never looked for the S2 offering before, but in my mind, I thought I had seen reference to it while looking at them for the S1. Apparently I was mistaken.

2. True. Apologies for my semantic error. What I meant may be slightly different from what I typed.

TeamRX8

iTrader: (25)

There are quite a few pro engine builders recommending OMP removal and just running premix only for race conditions. I wouldn't take one persons word as gospel on the subject, especially on this forum. That's essentially where and why most of the people here are saying don't do it, i.e. Polly wanna a cracker ....

If you use an aftermarket ECU for fuel and ignition control with just the factory ECU running the dash, e-steering, chassis peripherals, etc. the OMP and DBW systems can be eliminated.

MagnusRacing

iTrader: (2)

Thanks for the info!


Going back to my original post... I do plan to retain the factory ECU to run the motor. My understanding is that all I need to do is abandon the series 1 OMP and leave it plugged in to avoid "limp mode" problems that may be caused by the ECU not seeing the OMP. Does this sound right to you?

TeamRX8

iTrader: (25)

In theory yes along with the S1 6-injector LIM, but I haven't studied the S2 engine enough to know if there are other potential issues between it and the S1 PCM & harnesses.

Let us know what you discover along the way ...

j9fd3s

Mazda commissioned a study of oil flow inside the combustion chamber, that resulted in SAE paper 2014-01-1664 and 2014-01-1665. they did not test premix, but it does seem like increasing the oiling rate just has oil flowing onto the rotor faces IE it does little in the way of lubrication.

you of course are welcome to ask why they outsourced a study on an engine that they don't make anymore

robrecht

Interesting. Assuming that this is in fact the only purpose, would you still recommend premix?