AT Megasquirt
 

Some of you may have seen my thread about my Megasquirt project and followed it as it progresses. My intention has always been to find a way to apply it to the AT cars as well. If all goes well, tonight an RX-8 will be running off of a Megasquirt completely controlling fuel for the first time. The good news is that there are no mods necessary to apply this to the AT cars. I can literally unplug it from an MT, plug it into an AT, change the map and drive off. Your cars aren't so different that there are any wiring changes. The only difference thus far is with the 2 extra fuel injectors that the MT cars have. Since these get wired together with the 2 secondary injectors and you don't have these added injectors, this only means that you would have 2 wires added in that just go nowhere. That means they won't affect anything. I will be working on a fuel only tune for the MT cars and will hopefully see some promising results from it. I won't know until I get there. Unlike the Canzoomer or eManage, I can fuel tune the entire powerband and not just above 5000 rpm. After I get a suitable MT map loaded in, I will save it and post the file for anyone wanting to try this setup. Once I get ahold of an AT volunteer, I will do the same with that map. The AT owner will have the advantage that there is no research needing to be done on their car. Just plug in an ecu and tune it. Yes the CEL will have to be reset after tuning is done.

The next step after this is ignition tuning. Currently the Megasquirt can not read the stock RX-8 trigger wheel but I am working on getting that resolved. The one thing that will need to be changed though is the coils. Megasquirt fires ignition in wasted spark. This means that the leading plugs fire at the same time as each other. This lets one be on the power stroke and the other in the opposite chambers exhaust stroke. This cleans up emissions a little over non wasted spark. By firing these coils twice as often, I fear that the stock RX-8 leading coils would burn up. When I get this far I will make a suitable bracket that bolts in and plugs in place of the stock coils. Then I will just let people know which coils they need to buy.

This may sound like an expensive pain in the rear but it is really only this way for me. I'm doing all of the hard work. The ignition coil and board upgrade wouldn't add too much to the project. Here are some prices just to give you guys an idea of how much is involved. As this is a do it yourself project, you will need to build the board yourself. This is easy and fun.

Megasquirt ecu kit: $140
Stimulator (Megasquirt testing unit) $45
Wiring harness extension: $198 from Rotary Performance
Misc. parts: est. $35-$50

This all adds up to the vicinity of $425-$450 or so. That gives you full fuel control. If you want igntion control you can figure the cost of the board upgrade cicuit and new coils and such to add about another $150 or so to the project.

When it gets to that point we are still only talking about a $600 full standlone ecu and that is with new stronger aftermarket coils. Not too bad.

For those of you not inclined to build one yourself but would like to try this, you can get the Megasquirt fully assembled for $325 from various places. You would not need the stimulator. If you wanted a fully integrated harness that was prebuilt with MS connections, add about $250. The full assembled ignition upgrade would be closer to $200-$225 or so. This is still only about $800 for a standalone and aftermarket coils.

Compare this to what is out there right now. Not downplaying the currently available products out there. I like Mazsports system and it should work on the AT cars just fine. I also just like to do things myself. This just merely gives you guys an idea of what can be done with a little do it yourself know how though.

Obviously full fuel AND ignition control is a ways off yet with this but you get the idea on how much this would cost if you ever tried to venture this direction.

Megasuirt has the ability to tune cold start and warm up enrichments, and I assume you are using these. My only concern with a stand-alone is, does the factory ecu change these enrichments based on ambient temps. Would the enrichments have to be tweaked whenever winter comes around?

The factory ecu can not redo anything that I have done. That's the beauty of this. I have completely severed the factory ecu from the fuel injectors. It can try to adjust all it wants but it's wires now go nowhere. This is also how the Mazsport system does it. Yes I am using the enrichments in MS. They are based on coolant temperature and go all the way down to 0 degrees. Defferent temperatures have different enrichments. In the summer the enrichments don't start as far down on the temperature scale so yes it accounts for this.

Ah. I wasn't sure exactly how MS did it. Good to know.

To give you an analogy of how a standalone works vs a piggyback system such as the eManage, image your engine is a puppet. The stock ecu is the puppeteer. The eManage piggyback system will grab ahold of the strings in the middle to try to interfere with the outcome. If the puppeteer senses this, he will make the necessary changes to the way he plays with the strings. This is why the factory ecu can compensate for certain things. The way I have the Megasquirt hooked up is different. I have completely cut the puppets strings from the puppeteer but no one knows it but me. I have my own strings and I am now controlling the engine. The factory ecu can try all it wants. It's strings aren't attached to anything.

How much power do you think this will add? Do you have an A/T volunteer already?

I bet I can get another 15whp with a proper tune on my car, as for the auto's I'm not sure, part of the power issue with my car is after about 6500 RPM it really dumps fuel. In your case you have a lower redline so part of my gain isn't really reachable for you guys since your limited to 7500RPM.

Auto's will really benefit from the FI kits as the 7500RPM limit for you won't be an issue.

Yeah--I think that the greddy kit with the new interceptor ecu will be a little faster than the 6spd. Or a low to mid 5 sec. 0-60 with a proper stall speed.

The only AT dyno i've heard of was 135whp, that'd be somewhere around 165 shaft hp. It seems that auto suffers more from the cat life de-tune than the manual, hopefully a standalone would bump that up to 150-155 or so, where it should be (assuming 190hp and 20% drivetrain loss). Fuel cuts out at 7800rpm on the stock ecu, pushing that out to 8200 or so on the standalone, should gain a little better acceleration also, though a tranny cooler would be a must. The car pulls hard to redline from 4500rpm, there should be a little more room above redline, power-wise. I'm assuming that the factory ecu only cuts fuel at the limiter and doesn't do anything crazy. :)

It runs! Check the main thread for details.