Different E-manage setup?
 

Hi.

Since I have some first hand experiance with E-manage/CZ tuning and read a lot on this forum I see RX-8 tuning with this setup is quite close to the definition of a 'hard case' :(

The problem is the ECU constantly monitors a lot more input signals then just the maf, throttle and rpm signals the E-manage is aware of. Moreover like other new cars the RX-8 ECU seems to run in closed loop mode even at WOT and in all RPM ranges, sadly. So changing just the maf readings via a piggiback ecu brings varying or no results since the PCM signals change depending on a much wilder group of measurements.

In older designs the a/f metering was more like a safety feature. Value readings were slow and limited in range thus not really suitable to control engine management. However nowdays and much more specific in the RX-8 there is a WBO2 sensor which gives fast and more importantly axact reading of the a/f ratios. So why do an open loop fuel control system with speculations based on maf readings and RPM when we can build a proper closed loop system? And this makes the E-manage seup obsolete, sadly.

Just look at the nicely set a/f-s of the RX-8 form 3000 to 5000 RPM at 14.7. Those graphs would be close to impossible to reproduce without closed loop control of fuel injection.

But not all lost, since closed loop mode can be controlled as easily as open loop just instead of changing the imput signals we have to change the feedback signal! Which in this case the WBO2S reading.

So my idea is this: why not change the WBO2S signal readings insted of the maf reading? Sure there are some technical problems like the maf signal is a voltage level while the a/f signal is current but E-manage output can be converted.
A resistor and different map values to the E-manage table are neccessary and a constant imput voltage. Sounds possible.


So, am I totally nuts or might this work?
What do you think?

Tamas

Sounds like a good( MAGYAR) idea to me but i am not experienced enough to know if its possible , sorry .

Sheesh a RX8 in Hungary , you must be the envy of all the locals :D

cheers
miklos

the RX8 goes into open loop above 5500 rpms. Above that the e-manage works well, below that there is no reason to change anything.

The firdt time I heard open loop occurs merely due to rev rnge but not throttle position.WTF????? :confused: :confused: :confused: :confused: :confused:

To further mess things up, I am finding myself quite satisfied with the 20 h.p. increase and better driveability that the "M" flash is giving me. The only reason I would want to alter the ECU now is to reduce the amount of ignition advance so as to better accomodate my continuing nitrous upgrades. Any ideas?

Charles

5500 rpms is where it seems to go into open loop control no matter what the throttle position is.

a CZ/E-manage will control timing partially (it doesn't control both the leading and trailing plugs - only one of them). I believe Mazdamaniac put in an aftermarket ignition box that he could control both the leading and trailing plugs.

;) that is clearer - thx

I have tried contacting Jeff in the past. I have yet to hear back from him.

Charles

Ignite both, but not control.

The E-Manage will "control" both leading and trailing plugs, but it won't change the split. I do't know if the CanZoomer boxes are controling the trailing plugs or not.
What needs to be addressed is that the trailing plugs fire before the leading at idle. You have to be certain that the E-Manage is zero in that range.

Seems, but doesn't.

Open loop versus closed loop is based on load, which is a combination of RPM, airflow and throttle position.

Generally, it is in open loop above 70% throttle and 3200 RPM.

What do you mean? I haven't received anything from you. Feel free to e-mail me or PM me.

As far as the original idea, it is novel but not practical. You would need to decide when to suppress the WBO2S and that would be very complicated since, as noted, it is difficult to ascertain exactly when the ECU is going to settle on closed loop. Even though it is definately in open loop at some points, it isn't necessarily running a certain amount rich at that point.

It was quite a while ago that I sent a p.m., or two, but I didn't hear back. That was around the time that the CZ vs. E-Manage conversation was at it's peak. Anyway, since you are following this thread let me ask you two questions.

Since I am happy with the M" flash at this point, the only thing I need to do is be able to reduce the amount of ignition advance so as to accomodate the nitrous activation. I would like the reduction in timing to occur only when the nitrous system is activated, as opposed to when it is armed. Any ideas as to which way is best?

Second, since I am having a difficult time locating a "window switch" that will read the waveform from the tach send wire do you have any ideas on how to automatically cut the nitrous at 9,000 rpms? I contacted G-Tech to see if there is a way to use the G-Tech as a circuit controller. I can build my own DB-9 cable to wire into the nitrous send line.

Thanks Jeff,
Charles

as a quick and dirty, use the line for the rev buzzer. Tough I'm not sure what signal level that is though. or exactly what rev's it is triggered at. Just a thought...

discuss.. ;-)

The only reason I would want to alter the ECU now is to reduce the amount of ignition advance so as to better accomodate my continuing nitrous upgrades. Any ideas?

build a bracket and move the crank sensor around a few degrees :)

hey, you didn't say good ideas, just ideas. :D

Do you actually need to reduce the timing?
If you are using a wet kit and a conservative shot (50HP or so), the timing should be acceptable.
A dry kit is another matter.:(

Greddy has a new device that allows you to trigger two events over the RPM range. It is about $150.
MSD makes a similar box with "pills" that allow you to pick the RPM points in 50 RPM intervals.

I have been discussing, perhaps ad nauseum for some, the success that I have had with the Zex 55 h.p. wet shot. The 55 is no problem on a stock 8, but I now want to take it to 75 h.p. I have tried octane and cooler plugs as detonation management tools but the factory ignition is really finicky about it. I don't want to alter any aspects of the engine's tune until the nitrous is actually activated, hence the avoidance of modifying the crank trigger positioning.

I have also thought about using the voltage from the dash chime to activate a normally-closed relay installed in the 0-5v line that activates the Nitrous Management Unit from the Zex. It would be quite simple to find the specs on that lead and find a relay to do the job. That is a good idea but I would really like to hold the nitrous to 9,000 rpm's as I am still pulling real hard all the way to 9,500 and I want to get the maximum performance in the 1/4 mile. I have contacted MSD asking if the window switch works with the waveform signal. They haven't responded. I would imagine that the GReddy will accept and understand the waveform because they are a Japanese company dealing with Japanese-built cars. I'll look into the device you are talking about for $150. Thanks for that heads-up, Jeff.

What I really need is quite simple; to activate a second ignition map when both the nitrous is armed and the throttle body hits 3.9v, and to activate a relay when the engine reaches 9-9.5K rpm's. The more important of the two is the first one as that will allow me to experiment with larger doses of nitrous. I have become pretty good at shifting the gears at 9K by sound alone, but I would just like to have a little insurance against the accidental.

Thanks to all for your input and guidance. I am sure we'll come up with something and then I can report back what worked and how I did it. With a 75 h.p. shot, "M" flash, and tires that stick, I am sure I'll be reporting e.t.'s in the mid-12's@115 mph.

Charles

Be careful about taking the car engine too high on nitrous Charles. The last thing you want is for the engine to hit fuel cut at the rev limiter. That would be very bad. I'm assuming this is what you want a relay for.

That's exactly what I need the relay for. I have some good news for other Renesis owners; I have hit the fuel cut several times with the nitrous on and the engine is fine. I wouldn't suggest anyone rely on that fact as enough to protect the engine, just letting everyone know that the Renesis is as strong as you and I originally thought. I have had no problems going to 9K, and beyond, with the nitrous. I have also had no problems keeping my "foot in it" with the nitrous on while racing to the top-end. We were fast approaching 150 when I finally remembered that the nitrous was still on. That 3000 GT was a damn fast car!! He gave props to the RX-8, though.

Charles

Funny you mentioin a 3000GT, Charles. My other car(sig)!
Hope my 8 will be that fast soon :)