The problems with Megasquirt will be the same as with any other form of aftermarket ecu, yes even the wonderful but expensive top of the line Motec. A gun at a knife fight is worthless without ammo. It's not a matter of can we get any of the ecu's to control the engine properly. We can. The issue is can we get the aftermarket ecu's to do it and fool the stock ecu into thinking it has control so it doesn't throw a CEL? There must be a way but at this time I'm not completely sure how to do it. Only one way to find out.

There won't be any problems with the fuel injectors. We'd merely run them 2 stage rather than 3. The primaries injectors would always work. The other 4 injectors would come online together at a programmed rpm in MS or any other ecu for that matter. MS has the ability to do fast idle and they have now gotten the leading and trailing ignition working with fully adjustable split. It is no longer just a fuel only computer when used on a rotary. We are also very quickly approaching the ability through use of a wideband O2 sensor to program the fuel maps based on air fuel ratio! Low loads for economy and high loads for power all in the same map. The Motec has the advantage of being able to run the drive by wire but I fear that the stock ecu will not like this. I plan on leaving the motor to the stock throttlebody hooked up but use a conventional cable throttlebody instead. This way the stock ecu doesn't know what I am doing. All of the port valves can be operated through MS.

 

Just out of curiosity, if we are able to get a reliable TPS reading for Megasquirt... what's the need to go to a cable driven throttlebody? I'm just thinking along budget constraints here... of course I'd prefer a cable driven one where "I" control its opening and not Ford's engineers... but does it do more other than change WOT points according to accelerator pedal position? If so I'd rather just not switch tbodies... Or should we start talking about what t-body we need to get this working.

As far as my fuel question goes, I remember reading somewhere that the RX-8's fuel system lacks a return line... My question was more along the lines of am I going to need to completely redo my fuel system i.e. pump and regulator... Again I'd MUCH prefer not to...

Do you have any volunteers for a test mule in Houston? I'd love to see if the two of us could get one working w/o CEL's but I just don't see myself being able to leave D/FW anytime soon...

 

First off MS can't control drive by wire. For this reason we need a cable style. We use a Ford TPS on a new throttlebody and let the MS read it. The stock motor and TPS for the factory throttlebody is still hooked up to the ecu but tucked neatly away. The stock ecu will have no idea it isn't in control of this. Even if we get the car running off of a standlone and foll the factory ecu into not throwing an error code, we still lose traction control on the cars that have them.

There is already a person here in Houston who is going to test this. That person is brillo. We are doing all the research we can first before attempting anything though. He doesn't have traction control on his car btw.

Your stock fuel system will be fine.

 

the engineers of whom you speak work for Mazda not Ford. Even if you consider Ford owning Mazda as workign for Mazda they are the same ones who worked for years on the side over and above their regular duties to bring us the new rotary in the first place. no need to disrespect them just because their goals in programming the PCM are different then yours.

 

I think that the TB is probably optimized for flow at whatever the ECU thinks that is ...based on MAF,load, TP etc.....I'm sure that with the stock ECU it is better than a cable actuated one. I would bet that adding the magasquirt on a NA application would loose power. On a FI application It will allow tuning the areas that would be in closed loop in the stock ECU......but will it result in better power in the open loop areas that can be controlled OK by the e-manage??

I hope you do this so we will find out :D

 

Well "IF" I end up doing this... the stock ECU will be staying completely in place, with all its sensors etc still connected so as to pass inspection, why won't the stock ECU still open and close the TB? The ECU will still be working in EVERY aspect as before... except for fuel and spark.... I need to get a CANScan to check out pedal position sensor vs TB % open...

If you and Brillo are going to have a weekend where you do this I'd love it if I could come down to Houston and check it out...

I'll bring Shiner or Lone Star, your pick...

 

Mmmm. Shiner. Good stuff.

Leave the electrical throttle in place. You are not gaining anything with the MS by opening it with a cable.
The PCM will run it fine.

 

Yup... Shiner is one of my favorite beers... I had one of the best times of my life touring the brewery at Shiner, Tx... REALLY nice people and they basically get you drunk throughout the tour.

Back to the throttle, ok... that sounds much nicer... If it can be shown that there's alot of untapped power by ditching the electric throttle then I'll definitely upgrade eventually, but for now I'm not going to mess with it...

Gosh, I wish the UltraMegaSquirt would come out! That's my dream ECU.... I finally read up on the upcoming versions after you mentioned the ability to use thw WBo2 to tune the fuel maps for econ and power based on load...

 

You can get a daughterboard upgrade for MS called MSII. It does 90% of what UMS will do.

 

Jeff you sure about that? Not saying your wrong, but my fear is that since the DBW throttle is also a emissions device, if we start altering the air/fuel maps with the MS, and the on board Wideband sees that the car is running to lean for the ECU's likes, I'm worried the ECU will start trying to correct the AFR by screwing with the throttle. Hence why I wanted to take the DBW throttle out of the equation all together.

Not trying to make this more difficult than it has to be, just want to eliminate headaches from the ECU, and remove the possibility of a problem from the ECU and the MS fighting and creating havoc.

 

PCM only pulls the throttle for TCS and really bad knock.

 

good to know. Did you figure this out when you were tuning early on with your emanage?

 

Yes. I have never managed to get the ECU to pull throttle on the dyno, even by doing stupid things like unpluging the E-Manage in the middle of a pull (no leading ignition and no MAF).

 

Well that settles my decision with the electric T-body... if TCS and knock are the only things that are going to do pull throttle then I don't see a need to find a different throttle body and fab up a cable linkage.

Brillo, are you going to do just fuel? or are you going to do a MSII and control ignition... this is my first rotory and I'm still realizing that I don't have a camshaft... so how do we get the timing recognition to the MSII?

Please forgive me if I asked a dumb question there... I've only got 1400 miles on my 8 and its the first vehicle in over 80,000 miles that hasn't been an LS1 or an LS1 derivative V8 under the hood...

 

If this goes as we plan, RG and I will go with the MSII and control fuel and spark. He has it up and running on the 1st gen, so right now we are going to start working out how to most easily integrate the MS into the car. How timing works is something I'm still working out, but there is a way to make it work.

My goal would be to have a DIY, that would allow you to integrate the MS with relative ease, cut as few wires as possible (we are going to see hwo we can tap the current wiring harness) that way it can be easily removed for dealer service issues.

There are some other odds and ends issues, but tomorrow we are going to ID all the sensors and wires and starting working out a plan to test RG's MS on my car once he gets his 1st gen fully tuned.

 

The nicest option that I have found so far is also fairly expensive. That would be using a wiring harness extension that Rotary Performance sells. It costs $198.00 so it isn't cheap but it just gets plugged in between the ecu and the stock harness and is nothing more than an extension that you can cut into without altering the factory harness. You can also just unplug it to remove it with no alterations anywhere else. I like this idea but I don't like the price.

MSII is nothing more than a daughterboard upgrade for MS. It is all the same ecu. Just think of MSII as an add on card. Currently MS can run off of the 2nd and 3rd generation RX-7 ignition systems. I haven't looked into how the RX-8 differs but the 2 generation of RX-7 ignitions are very different from each other.

If the stock ecu only pulls off throttle for knock or traction control then that settles that and makes life much easier. I just plan on hooking it up the way I think it should be done and then deal with issues as they pop up. The good thing about this is that if we figure out how to make the MS work with the RX-8, it will also mean that we will know how to make other aftermarket ecu's work with it as well so others can choose what they want to do. I fully expect to get a CEL at first just due to tuning issues and the car not seeing what it wants to with the O2 readings. My hope is that after it gets tuned in, the ecu will not have an issue with it and we can reset the CEL with no further issues. We'll see.

 

RG - That wiring harness can also be purchased by some shop out here in Dallas or Garland I believe... Its the same Rotary Performance sells. I had the same idea, I know it significantly adds to the price... but it also lets me revert to stock in the future with minimal effort... which I think is well worth the 200 bucks... If someone can find the matching connectors online we can make the harnesses ourselves... its just time consuming, not difficult.

I fully expect to throw CEL's while tuning and getting everything sorted out. But if no lights are thrown after everything is finished that's the ideal situation.

As far as other standalones go... I don't really see which one's you'd pick over MSII or UMS... once UMS comes out they'll handle sequential injection which will add about the last feature it doesn't have... (correct me if I'm wrong... remember I'm from the world of pushrods)

Are you going to attempt to use the stock IAT and coolant sensors or are you going to buy the GM sensors? I read about having to modify the wiring if you're trying to use the stock sensor that's still connected to the stock ECU...

 

Same people. Rotary Performance is in Garland.

 

If we can find a way to hook the MS up with as little hacking and cutting as possible, it won't matter if the computer throws a CEL or not, b/c if your worried about emissions testing or a dealer trip, you can just take it out and revert back to the stock ECU.

Obiously, we want to dial the MS in as best we can hopefully the AFR's will be a range that the ECU is ok with. That said, it can be rather nanny like, and I remember with my Mazda6 how the AFR would get to lean (not in an unsafe way) with a CAI and throw a CEL. We use to refer to the CEL as the High Power Mode Light

 

I've been going throughout he RX8 wiring diagram to start mapping out the various wires from the PCM that control all the various functions (fuel, spark, O2 etc....) I want to tap. This is my first step in creating a wiring harness.

I was hoping that the PCM even controlled things like the ignition/starter switch, but I'm not seeing that on the list. There may be one or two none PCM controlled devices that we may have to cut/splice to tap into. What we could do is create a switch so that if you wanted to remove the MS you could flip a switch and the starter/ignition would flip back to the original system. I'd like to do this with as little modification as possible to the stock wires.

My next area to address is the variable intake system. Jeff mentioned that the throttle should be happy if left alone, so I'm operating under that assumption for the moment. This makes me wonder what the PCM would do about the staged intake port openings. If the PCM wouldn't freak out and not open those ports even if it saw a ARF it didn't like, that would also be very useful. I could build some RPM switches to control them if necessary, but I'd rather not have to cut into those wires if I can help it. The intake ports should basically operate as either on or off, so I would think the PCM would open them regardless of AFR when you approach the proper RPM. I need to revisit Richard Paul’s thread on his car, as I thought he may have had issues with his intake ports opening that could have been PCM related.

 

they are opened by vacuum at rpm. they are not afr dependant at all. after one opens the pcm adjusts the afr with more or less fuel. thats all. of course the one is a switch then vacuum but Fred knows that already

 

I wouldn't worry too much about the VFAD system... its only point is to reduce intake tract noise... I assume you're putting the MS on to make FI a viable solution in the future (which to me... the Emanage is just not an acceptable way to tune a vehicle) which would make the VFAD system kind of useless...

I'd read somewhere it was vacuum controlled as well...

 

Some progress was made today. We played around with the car running some tests and doing general mutimeter verification of different sensors. We now know exactly how to hook in Megasquirt to the stock wiring harness. We have located the water temp sensor, the intake air temp sensor wire which is built into the maf, the tps signal wire which there are 2 of to choose from built into the drive by wire system, The biggest thing left to work out is ignition control. I currently do not have the new wiring schematic for the rotary ignition setup for the MS. I do know which wires to tap into for the stock e-shaft sensor and the ignition coils. The holdup is on the MS side. I also know which wires control all of the different intake valves and how to make them work. I plan on trying to get the MS working with the stock ecu controlling them first to see if they still open when they normally do. If so there's no reason to change it. If they don't open correctly it won't be too hard to make these controlled by MS and be able to open them at whatever rpm I want to.

Another big problem with the ignition system is the strange shape of the stock Renesis crank trigger wheel. It is a unique design that MS can not read. I'm sure someone could write the code to make it work but I don't have that ability. Fortunately Paul Yaw sells new trigger wheels in a 36-2 configuration that he used with a Motec system. MS can read this. It would also utilize the same pickup sensor. This wouldn't be a very involved install and is no harder than changing pullies. The ultimate goal would be to get the MS to interpret this so someone get busy.

From the way we have everything laid out right now, the Megasquirt will be able to plug into an extension harness and be fully programmable. This means 100% control of fuel and ignition! No piggybacking of the signal. The install would be simple. You would unplug the 5 harnesses from the factory ecu.
Literally just plug the new harness inline between the stock harnesses and the stock ecu, replace the crank trigger wheel and you have a fully programmable ecu. I know for a fact the car will work good like this. The part I don't know yet is if it will throw a CEL or not. We'll see when it gets that far. If this ends up working it will be very easy for anyone to make a map and save it as a file. You can then uplaod it online and others can try it out at the push of a button. Just a quick download away. If you don't like it go back to the old one. Simple.

This is an exciting little project. Unfortunately don't expect us to have this running next week. I still need my MSII daughterboard and they are back ordered for at least the next month. Then it takes almost a month to get it here after it is ordered. Then we have to work out the bugs of tuning and testing it for reliability. The wiring harness will be built and ready by the time the daughterboard upgrade arrives though.

I have been thinking about this being a possible easy solution for forced induction users. For turbo applications it would work just fine. For supercharged applications though such as with roots, twin screw, or axial flow units that place the throttlebody before the blower, there will be one important mod needed. The intake temperature sensor is located in the maf. This is before the blowers and their hotter air. The ecu compensates for barometric pressure and temperatures. We need to sensor to be after the supercharger. For this we would not tap into the sensor in the maf but rather add a new one to the intake manifold or any other place that would be after the blower. This will require direct wiring to the MS rather than going through a harness. Fortunately this is only 2 wires, a signal wire and a ground so it's no big deal.

TO give a little insight as to how the MS tuning will work, we will be using staged injection. The Renesis (high power) uses 6 injectors. They each come online in succession in pairs. I however only have 2 stages to work with through MS and not 3. This isn't a problem though. The primary injectors in the intermediate housing of the engine will always spray just as it does now. The other 4 injectors will all be wired together and all come online at a specified point. Since I have control of the maps and fuel flow, matching their added flow to the primaries smoothly will be no big deal. I've done it on my car seemlessly. The nice thing about MS and the fuel injection staging is that I can bring them online at any rpm I want to. I could even bring them online based on map load if I wanted to such as when boost kicks in rather than at a set rpm. Lots of possibilities. Add this to the potential to have the intake port valves controlled by MS as well if we wanted to and you could completely retune the intake tracts to suit your needs such as the different tuning requirements with engine porting or forced induction. I love this thing!

That's your update for now. It will be a drawn out project as we try to acquire the neccessary parts but it will be well worth it in the end. The days of total engine control are coming in the near future. We WILL get around the stock ecu. It's just a matter of time now.

 

great read, i am in amazment of what you are doing. please keep it up and keep us informed.

beers

 

Wow.

I'm gonna be perfectly honest -- I don't know what half that **** means. But I do know that it's nothing but good news. Very happy to hear it.