Since it's already come up a couple of times in other threads, I thought we could all just have an open discussion of it here. For those who don't know, the '09 RX-8's have gone to only 4 fuel injectors total rather than the 6 that the pre-09 cars had. There have been some other changes as well including some accounts of more power from the newer engines. What I'd like to see in this thread is differing opinions as to why they would have gone back to 4. A few of use have talked about this for a while so now we'd like feedback from others. I'm a fan of it personally.

Discuss...

 

The P2 and P1 basically put fuel in the same runners....so they likely went to bigger primary and secondaries...and used some nice new great atomizing primaries to get the idle smooth

 

RG, I know you said you discussed it previously, but could you state your opinion/analysis of this here also?

I wish there could be a comprehensive thread made that focuses on detailed analysis of the changes made to the "Series II" RENESIS by the more distinguished rotorheads here...

 

the problem is we dont know them thoroughly. we are just now after circling the issue for a month getting around to talking about the injector change. and we dont have all the facts about that yet. then there is the OMP change, pcm change etc.

lets stay on injectors here.

there are so many questions

why change now?

why was it done with 6 before if you can do it with 4?

is there more dynamic range to the Primary that allows the new PCM finer control?

Is it the new PCM that allows this set up?

what is the staging like- which we will find as soon as an accesport or other datalogging device gets connected

does this make more power?

can we make more power over stock with just the 2?

what changes have the RACE TEAMS made?

 

What Dan said is one reason I've always thought the 6 injector setup was a bit strange. Why on Earth would you have 6 different intake runners and 6 injectors but then not have them all in corresponding runners? This never made sense to me. You have a total of 4 in the primaries, 2 in the secondaries, and no injectors in the auxiliary ports which are open later than the others. I don't like the idea of nearly 2/3 of the total fuel going through only the primary ports at high rpms.

The 6 port 2nd gen RX-7's had only 4 fuel injectors but they also only had 4 intake runners. The auxiliary ports were fed from the same runners as the secondary intake ports. This was actually a good thing from a fuel standpoint as the secondary injectors in those runners could feed fuel all the way to the closing time of the auxiliary ports which can not happen in the Renesis.

The GSL-SE 1st gen RX-7's of 1984, and '85 were the first 6 port 13B equipped RX-7's in the U.S (Japan had 6 port 12A motors in '81-'82 which used a carb). These were also the first fuel injected RX-7's. I just happen to have one. These cars only had 2 fuel injectors located in the intermediate housing much like the primaries in the Renesis. It wasn't until the 2nd gens that they went to 4 injectors and then held this practice through the 3rd gen RX-7's.

I prefer the 4 injector setup. It's simple and easily staged. Strangely enough on engines under about 200 rwhp or so, I actually like going back to 2 injectors! I'm in the minority here in the community as I run 2-720cc injectors and set fuel pressure at 60 psi. That's it on my RX-7. Simple. That's the whole reason I like it. Simplicity. Do I see anymore power from it? Not that I know of. I don't think I see any less. I'm sure emissions suffer a little bit and I'm not sure about mileage. Maybe at best. But, it's simple. There are of course many arguments to use 4 instead of the 2 that I do and I understand them. I just like the simplicity.

The simplicity reason my be Mazda's justification. If 4 can do what 6 can, why use 6? Fuel injector technology has come a long way and so has computer control. Now what I'd like to know is what size are the injectors? Are all 4 equal size or are the primaries still smaller?

 

I haven't found any specific CC size on these yet. Did get part numbers for the primary and Secondary injectors.

Primary N3R213250
Secondary N3R113250

 

That's interesting. The pre-09 parts #'s are N3H not N3R however only the letter is different. The numbers are the same. Incidentally the numbers match the primaries and the auto's secondaries.

 

looks like injectors are 450s and 570s for a total of 2040 vs previous old total of 2100. these injectors are supposed to be a much better spray etc

 

What sort of impact, if any, do you think this will have with regard to preventing instances of flooding? That is, will the "Series II" RENESIS be harder to flood due to the new injectors and PCM/programming?

 

Bigger injectors that atomize the mixture better could get more power but I can't figure y woujld they not stick with 6 good injectors to make even more power?

 

flooding isnt a big issue after the 04/early 05's anyway..

if they can get the granularity they desire out of it and better atomizaion than previously along with more total fuel flow... its probably cheaper to use 4.

maybe not the driving force behind the change, but possibly a factor

 

Just throwing this in here...may it have something to do with engine "space" why Mazda went to the 4 Injectors?..

There are TWO Electric Oil Metering Pumps not one which are joined together by an oil hose. The two pumps are located right on the top of the engine in dead centre.

I am not prepared to pull mine apart (yet) to look , but there ain't a lot of room there.

Just a thought...

Here is the WS manual on the EMOP..
https://www.rx8club.com/showthread.p...=1#post2796208

 

The first 4 alpha/numerical part number combination is the model code applicable to the car, the next two '13' is the location of the part installed (13 means fuel system) and the next 3 or 4 numbers which may include letters is the actual part number.

The Mazda system has always used this type of combination for Spare Parts, the first group is Model, next 2 are the parts location, and the final is the part number.

In the injector case it is model specific and I doubt the new will supersede the old as a replacement part for obvious reasons.

You can however have a part/part number that has a specific front model code from a RX-8 or Mazda 6 that is used across many models but retains the original models code and part number..

Example the new Series II oil filter is..
N3R1-14-302 ( which is a larger original filter) may be used on another model of Mazda but would retain the RX-8 part number.

Again N3R1 (New RX-8) 14 (oil system location) 302 (Part Number)

 

I've run up to 730 in the primary with a satisfactory idle and such, so I doubt that plays into the equation.
The new setup is staged exactly like the old setup, only no third set comes on at 6250.As far as all the fuel coming in one port or another, it simply doesn't matter at this power level.
The volume of fuel isn't high enough.

 

^^, the air/fuel intake port size are unchanged so the overall volume remains the same.

 

I was talking about injector volume.

 

While looking for something else RG mentioned in another thread I stumbled upon this which I am sure most have seen but just in case I thought might interest some here.

Cheers

Andrew

 

Speaking of 6 v 4 injectors -- are they the same type of injector. just a different size or are they different. Is there a better replacement for the 6 injectors that simply cost more?

Basically what I am asking pertains to Mazda's motives regarding the new injectors. Is it for cost/ production reasons or for performance/ efficiency?


I may simply be confused but I was wondering if this was answered yet.


Part 2 -- Is there any design differences in pump, lines, filter, fuel rail,etc...

Part 3 ---I realize there are different plugs now -- is this directly related to only 4 injectors? different reason?

believe it or not all these questions are asked around the idea of the injectors -- with this in mind -- are they really better? Did Mazda figured something out?

many other posts hinted at these but then stopped. (I apologize for reading multiple threads and may not be making total sense in advance.)

 

You have to consider is that, for this kind of cars (sport compacts) it is usually related to a mix of what you say: production costs vs efficiency.
The strange thing is that they made some significant improvements for an engine that will be dumped after this car.
I wonder which of the implemented technologies will be adopted by the 16x.

 

I doubt that they would be using 6 Year old technology if they have taken the opportunity to change things.

Cheers

Andrew

 

Perhaps that is why .. they are making the changes ... data collection for the 16x ... trying out new things on an engine already in production... Yeah for guinea pigs!

 

This is a good theory but since the new engine is expected to be direct injected what would the point be of trying some new injectors options when you will have to dump them anyway?

 

these- at least the primary are a better injector than the originals

 

forgive my ignorance. Since they scaled back the injectors did they change the number of ports too? I'm trying to figure out whether they rolled back to the 4 port or just improved effeciency with fewer (assumedly better positioned / better powered) injectors.

 

It's still a 6 port motor but with improved injectors. The old ones were good. These are better.

Ash is correct about the part numbers: 13-250 is almost every injector part number Mazda has ever sold. The N3R, which precedes it, represents the new RX8engine and they can use whatever digits are required to further identify a part. Chassis and body related parts will now tend to be FF instead of FE but that gets even more complicated

Paul.