ECUtune Stage 2 version 3 ( 2v3 )
 

We have decided to replace the nitrous oxide tuning software with the much asked for software for using a larger mass air flow meter.

As many of you know, the SVX mass air meter is maxed out at the factory peak horse power and needs to be upgraded if you want to get more peak power than you already have. There is the possibility that this upgrade will improve your performance beyond that of stage 1v4 without any further hardware modifications but this is not yet known. We are not going to do any dyno measurements on our own right away but one of our customers is and we will share that information when it becomes available.

Of course the real impetus behind this upgrade and the reason we've gotten so many requests for it is because many of you do want to do mechanical upgrades to your svx to increase power. This software paves the way for supercharging, turbocharging, and running higher rpms.

Now to the nuts and bolts of it. The stage 2v3 software is the stage 1v4 software further modified to run a z32 mass air flow meter instead of the factory svx mass air meter. Just like the stage 1 software there is a second version of software on the memory adaptor with 5 degrees less ignition advance and without the aggressive ignition advance seek used in the base stage 1v4 software. When power is sent to the input pin of the memory adaptor it runs off of the second version of software. This enables you to run premium unleaded fuel or regular unleaded fuel at the flick of a switch. It also provides a good tune for forced induction.

Here are the particulars on the mass air meters and some of the basics on the adjustments made for the switch. The z32 mass air meter can measure two and a half times as much air as the svx mass air meter; however due to a mathmatical limitation we can only utilize it to measure about 1.9 times as much air in this version of the software. Still that's good for about 440 hp.

The mass air meters give a voltage signal between 0 and 5.12 volts according to how much air is flowing through them. In the ECU software there is a highly acurate table used to translate this voltage into a number used to represent air flow. I'm not calling it an actual airflow measurement because the # isn't in any particular unit for measure of flow and most importantly it isn't scaled to represent the actual airflow yet.
Here is a plot of both translation tables.
http://www.ecutune.com/posts/stage2/maf1.gif

You'll notice there that the plot of the z32 meter is lower than that of the svx meter. That does not mean that it is measuring less air. Remember that all mass air meters measure in a range of 0 to 5.12 volts. The value generated by these curves is multiplied by a constant the size of which varies depending on the flow rate of the mass air meter and the flow rate of the fuel injectors. A higher flow rate mass air meter has a bigger constant. Lower flow rate fuel injectors have a bigger constant. The z32 mass air meter flows 2.5 times as much air as the svx mass air meter and the constant should be made 2.5 times larger when switching mass air meters. Unfortunately with the size fuel injectors we only have enough digits to make our constant about 1.9 times bigger before it maxes out.

Of course we can't have our constant and translation table values not generate the correct #'s so our work around is to use the commutative property of multiplication/division and adjust the values in the translatoin table by the ratio of what the constant would be with the factory 300z translation table and what it actually is in our software. You'll notice not supprisingly that now the curves match up very closely. You'll also notice that while the meter makes accurate measurments on up to 5.12 volts we lost some of the top voltage measurements because now the table values are maxed out. Because of this we are only able to measure 1.9 times as much air instead of 2.5 so we will max out at 440 hp instead of the 575 that the stage 3 software maxes out at.
http://www.ecutune.com/posts/stage2/maf2.gif

This graph shows the comparitive airflow measured by each mass air meter. It shows the value output by each translation table multiplied by the ratio of the constants.
http://www.ecutune.com/posts/stage2/maf3.gif

That about sums it up. The software gives all of the benefits of stage 1 but now uses a z32 mass air meter so that timing is accurately controlled for loads up to 440 horse power and fuel will be accurately supplied to the utter physical limits of the fuel injectors.

Great explanation Michael.

-Chike (now just offer this for the OBDII folks and then we'll be talking... ;) )

Do you have a timeline for when this will be available?
Sounds like a great project.
Already trolling ebay for a used MAF. :D

It's available now. I haven't done a bang up job with the stage 2 page of the website yet but it has been changed to the new stage 2v3.

http://www.ecutune.com/svx-stage2.htm

So do you think we could combine this stage 2V3 with a Apex-i Super AFC and run larger injectors for a turbo (like sti 550s, or even the Q-45 370cc?)

No, you definitely do not want to mess with the voltage signal from the maf meter--that would completely mess up the ignition timing which would be dissasterous. I would first build your system and see if you need additional fuel. I think you will find that if you run a walboro fuel pump the increased fuel pressure and the fuel injectors being able to be driven to 100% duty will give you enough fuel unless you have an engine built to a lower compression ratio. If you need additional fuel then use additional injectors with a seperate controller to add the fuel.

Most people don't have a very thorough understanding of what happens if you go beyond the ability of the fuel injectors to deliver fuel. It's important to note where/when you would actually run low on fuel. When we talk about the size of a fuel injector we are talking about it's flow rate, the amount of fuel over a set time. It's when the time is short for fuel delivery that the injector is most limited in it's ability to deliver fuel. That means high rpms. The higher the rpms the shorter the time the fuel injector has to deliver the fuel necessary for the intake charge in the cyllinder. In driving that means the first place you can expect to go lean is the last place you will find yourself, high rpms at top gear. In the lower gears you will be shifting before you get up to redline. Our shift point is 5600 rpms. 5600/2 = 2800 intake rpms 2800rpms/60sec=46.67 rps 1 sec/46.67 rps = 0.0214 sec per rev = 21.4 milliseconds to deliver fuel. This is quite a bit of time. I certainly wouldn't recomend sacrificing accurate engine managment for 99.9999% of your driving time to get a higher flow rate for high rpms. The stage 2v3 software will run forced induction well--it lights up the tires on our stage 3 system at will. Build your system first after it's running if you find you need more fuel add it without messing with engine management.

Any idea how long it will be till we see some dyno results on this? I'm pretty sure I have a friend that should have like 2 MAF sensors laying around. And depending on how many people are looking for these I may be able to talk to some of my old Z buddies and see what I can do about getting some of these cheap. In case you can't tell I can't wait to get enough money to get my hands on one.

We won't be dynoing the stage 2 code ourselves any time soon. Our demo car has a blower on it which i think would qualify as cheating. Like I said though one of our customers has indicated that he will dyno the stage 1v4 and the stage 2v3 back to back on his car before installing his turbo system. He has a low miles engine and manual transmission so he should get some good clear results for us.

So running a upgraded fuel pump, and running higher fuel presure will be acounted for in the engine managment. I just thought the ECU ran off of a constant fuel presaure and doesnt check up on it, if it were to change.

when will that be happening, any idea?

Possibly discount about the price of dyno costs, if Im willing to do the same thing? :D

Michael,
Based on your understanding on how the SVX's ECU operates, how does it "close the loop" with the injectors with regards to factoring in injector duty cycle and BSFC??
Thanks.
-Bill

This thread finally prompted me to hook up the MAF signal and tachometer signal to my LM-1 data logger. Below are the results for a WOT run that I made this morning on the way to work. The outside air temperature was about 82F, so there was a bit less oxygen than usual. The MAF is peaking right at around 4.5 volts in all four gears. According to Michael's plots, that leaves about 20% headroom for engine mods. But there should be at least 10% reserve for driving in cold temperatures where the air has about 10% greater density. So, realistically, the stock MAF does indeed have only about 10% headroom for engine mods which isn't much (only about 230*1.1 ~ 250 max HP).

http://www.subaru-svx.net/photos/fil...czko/27877.gif

Great plots Mychailo. That definitely explains sheds light on the situation. I couldn't accurately tell from the graphs, but what was the richest afr you saw? Seems like you got pretty rich at the top of 4th gear...

-Chike

Actually 4.56 volts is 86.3% and 4.64 volts is 90.2% of the theoretical max of the svx mass air meter and is only 4 and 3 readings down respectively from the theoretical max--as you can see resolution at this far extreme of the meter is poor. With the z32maf this reading would be around 3.76 volts and lie right in the meaty belly of the curve.

what model airflow meters
 

Well I have access to a few 90-96 maximas and two 94 na 300zxs.Do I have to switch connectors.