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I was sitting around pondering things the other day and realized that I don't really understand how fuel injection works on the RENESIS.
My understanding of a conventional fuel injection system (which may be wrong) is that there is one injector per cylinder. Pure air is drawn in through the intake valve on the downstroke and the injector sprays in fuel to create the mixture there in the cylinder right before compression. Or am I wrong, and the injector injects the fuel into the intake manifold leading to each cylinder's intake valvue?
So where is the injector on the RENESIS? Is it on the intake manifold and sprays fuel into the air before being drawn in through the intake port? From diagrams I have seen, it does not look like there are injectors mounted to inject fuel directly into the combustion chamber in the engine block during the intake cycle. Also, does the same intake manifold service all three intake ports or are there individual manifolds/injectors?
Unless the engine is diesel, or has direct injection, then the fuel is sprayed into the intake manifold. In the Renesis there are 6 staged injectors, 3 per rotor, that spray into the intake manifold. There are many posts that discuss this in detail. do a search. The intake manifold has a plenum with 6 staged runners, 3 per rotor. If you want to know the details of the intake manifold do a search for S-Dias.
I went digging in the tech manual and found the attached diagram which matches what everyone is saying. The P2 and the S injectors are relatively far back on the intake manifold. The P1 injector looks to be mounted right at the primary engine intake port and uses that port to inject the fuel rather than having a hole in the block of its own.
So the A/F mixture is still pretty much created in manifold and sucked into the engine which, as I learned above, is the way most piston cars work.
for the P1s i believe there is an air injection nozzle to atomize/ homogenize the fuel. ive seen it (if i am remembering correctly) on one of those pics from the press kit.
This probably showing my ignorance. The diagram shows both the P1 and P2 injectors providing fuel to the primary intake port and the S injector providing fuel to the secondary intake port. The 3rd intake port on the High Power (6 port) engine seems to be for air only. Does anyone know if this is true?
And on how many injectors does a rotor run on idle? When does it run on 1, when on 2 and when on 3?
My RX-8 runs on idle 2 injectors per rotor, 4ms each. I've seen an RX-8 running 2ms and 1 injector per rotor, until it got above 4000rpm, it activated the 2nd injector and activated the 3rd after 8000rpm. Both are Renesis HP.
That's not correct. It idles on the two P1 injectors, one dedicated to each rotor. None of the injectors are shared between rotors or at least not on the factory setup. If only one injector is firing then only one rotor is running; not very likely.
The other injectors kick in based on engine load and injector duty cycle demand as determined by the PCM.
S1 6-port
S-1 4-port and S-2 6-port (actually a 13B diagram, similar representation for illustration purposes)
That's not correct. It idles on the two P1 injectors, one dedicated to each rotor. None of the injectors are shared between rotors or at least not on the factory setup. If only one injector is firing then only one rotor is running; not very likely.
The other injectors kick in based on engine load and injector duty cycle demand as determined by the PCM.
S1 6-port
S-1 4-port and S-2 6-port (actually a 13B diagram, similar representation for illustration purposes)
Thanks for the quick reply! Copypasting my case from another thread:
Brettus Well ............ you should only be getting a pulse from the reds and only when engine is turning over ..................
Originally Posted by dannobre
Cause cranking and idle and low load they are the only injectors firing
So the Renesis HP has 2 Red Injectors and 4 yellow ones, right?
So I should have 2 injectors active on idle, 4 others not.
I connected my computer to the Mazda ECU and it reads that 4 injectors are active. They values are not doubled, each injector has its own value.
How can my Renesis HP run on 4 injectors, 4ms each on 800rpm and have a 42% engine load? It's terribly hard to start, it floods, and it would atleast explain alot. When I add throttle a bit (adding more air) it also start better. When I finally start it, it just sends out a giant cloud of unburned fuel, sputters into the 3000rpm and my neighbours closed their windows from the gasoline smell. Once it started? Performance is great, I ran 230km/h on the highway without much hassle. When I let the car idle for a long time and turn it off and on again, it starts just fine. During normal driving, it won't start when I stall the engine by accident. In January the problems began and it was terrible to start. April, the car started like new. Then the problems came again, then when I was abroad with the car I had no starting issues at all besides a battery that made the car start at 10Volts. Come back home, problems returned.
Right here in the same program you can see that at Idle only 2 injectors are active. Why are there 4 active in mine then??? Is it a PCM update or what?
I might strongly consider just disconnecting Primary 2 and Secondary injectors and see how the car starts then. I also get ticking from the engine bay which according to many is a stuck SSV valve. Could it be stuck open and activating the Primary 2 injectors?
Thanks for the quick reply! Copypasting my case from another thread:
So the Renesis HP has 2 Red Injectors and 4 yellow ones, right?
So I should have 2 injectors active on idle, 4 others not.
I connected my computer to the Mazda ECU and it reads that 4 injectors are active. They values are not doubled, each injector has its own value.
How can my Renesis HP run on 4 injectors, 4ms each on 800rpm and have a 42% engine load? It's terribly hard to start, it floods, and it would atleast explain alot. When I add throttle a bit (adding more air) it also start better. When I finally start it, it just sends out a giant cloud of unburned fuel, sputters into the 3000rpm and my neighbours closed their windows from the gasoline smell. Once it started? Performance is great, I ran 230km/h on the highway without much hassle. When I let the car idle for a long time and turn it off and on again, it starts just fine. During normal driving, it won't start when I stall the engine by accident. In January the problems began and it was terrible to start. April, the car started like new. Then the problems came again, then when I was abroad with the car I had no starting issues at all besides a battery that made the car start at 10Volts. Come back home, problems returned.
Right here in the same program you can see that at Idle only 2 injectors are active. Why are there 4 active in mine then??? Is it a PCM update or what?
I might strongly consider just disconnecting Primary 2 and Secondary injectors and see how the car starts then. I also get ticking from the engine bay which according to many is a stuck SSV valve. Could it be stuck open and activating the Primary 2 injectors?
Bump.
It could have to do something with the engine load!
The ECU calculates the engine load with the following equation:
LOAD_ABS = [air mass (g / intake stroke)] / [1.184 (g / intake stroke) * cylinder displacement in litres]
Therefore, the engine load may be incorrect if one of These values is incorrect.
----Cylinder Displacement - I assume this is a fixed value in the PCM.
----Intake stroke - RPM dependent, and depending whether the cylinders are 2 or 4 stroke, and how many cylinders and this is hardwired into the PCM aswell. Our engine makes an intake stroke every half RPM.
----Mass Airflow - Dependent on the Mass Airflow Sensor. If this sensor is underreporting (telling the ECU less is coming in than it actually does), you end up with a lean engine. If it overreports, you end up with a rich running engine.
Since the injectors activate depending on the load, which by reverse calculating into the Engine Load calculation, it comes down to the MAF.
My MAF should be reading between 3,7 and 4,3g/s (I don't remember the exact numbers anymore, it is in the Workshop Manual).
Instead, it is reading anything between 6 and 7g/s as of now. You can imagine that when you send the double of the airflow to the PCM, the engine load would double aswell. As soon as the engine load is high enough, it will just activate Injector 3 and 4 and flood the engine , by my theory and understanding so far.
Besides that the MAF readings are far from the ranges that the Workshop Manual prescribes and WOT max RPM it Reports only 170g/s instead of the old 230g/s and jumps anywhere between 140 and 160 g/s during WOT within every PID update, I can't conclude anything else besides that the MAF is just DEAD.
@Preppie: No, i definitely won't from now on. That could very well explain the erratic readings when the engine is running.
@TeamRX8 Choke on a dick.
Now I want to add some more Information both relevant to me and this thread that I found on rx7club.com and some of my own backup on this Information.
The PCM has 2 injection Timing modes you could say. Under 500rpm, the PCM considers that the engine is cranking, and uses seperate Timing for cranking and starting the engine. After 500rpm, PCM consideres that the engine is started and Switches to another Timing, as explained in the Image below.
My backup on this is my diagnostic tool which can read the injector pulses of the Petrol injectors of my RX8, and note that exact Point where the engine just hits 500rpm. The PCM seems to Switch the injection Timing from the 'Starting program' to the 'Running program' and actually starts my engine. You may not see it clearly in the graph, but the Moment the PCM reads 500rpm, it Switches to another Timing.
This could also explain why my engine used to start very well with fuel trims reset to 0% and started horribly with fuel trims on 12%, because the PCM may be trimming the cranking injector Timing under 500rpm aswell, which makes it crank richer. Before it gets to the 500rpm Point, it just floods itself.
It also explains why the car starts better by adding a bit of throttle, because it reduces manifold vacuum and Brakes the engine less, so it can crank at higher rpm and reach those 500rpm more easily.
The engine may lack the power because it's flooding from the start and has difficulty reaching those 500rpm. But I have nothing to back this up, so that remains a theory.
Concluding from this, my car starts fine when it hits the running program, but the starting program Fails to give the engine enough power to get over the edge of 500rpm. Well, honestly it runs like **** now, but that may be because the injection Timing relies on the MAF after 500rpm, and not under 500rpm, but again I have no proof to back this up and it remains a plausible theory.
Also note that the engine in all 4 cases fires right up when the injectors hit 6ms at 500rpm after the PCM Switches from Cranking to Started injector mode.
I have somewhere another graph where I have cranked the engine for a solid 30 seconds until it started right way, because the fuel injection times dropped steadily after those 30 seconds. Which is again exactly what the workshop manual describes. If the engine does not start after 30 seconds of cranking, it will reduce the injection times and in my case, start because it hits the sweet spot of injecting 6ms at around 480rpm. This kicks the engine over 500rpm and switches to running mode.
You should also be able to identify when the PCM Switches from cranking to running on your Dashboard, which is typically when your oil pressure gauge goes to the middle as I have experienced, but for this aswell, I have to prove this with actual numbers.
I especially want to know why the engine is flooding in Starting Mode. Maybe it has something to do with the wiring of my LPG Controller and that somehow activates 4 injectors instead of 2 and just floods everything. The car also used to start quite often during the deflooding procedure. In any case, there is lots of data and proof from the workshop manual that my engine is just flooding itself in the first injection mode and prevents itself from getting in the second injection mode where it would function correctly. Now I have to find out what is causing this.
01-25-2006, 09:52 AM
