So i was going to get a Haltech and was really stoked about it til I started doing some more research on some MS stuff.

Ive now changed my mind and want to run MS specially after reading aaroncakes MS write up. I still have a ton of questions though.

I have little to zero knowledge on the pullup's, boards, cards, resistors, cables, ect. (the electronics stuff...) and so reading all this info really confuses me. I dont want a DIY kit cause I know I would F it up and fry the whole thing...


If I buy DIYautotune's MS3X kit will I need to make any internal mods to make it work fully on my S4 T2 with using the BAC, stock TPS, stock CAS, stock coils, and GM AIT and CLT. I would like to run the boost controller and water/meth and cooling fan off the MS also..

Also can I run the wiring harness according to aaroncakes MS write up and run the MS3X without modification?

 

Using MS3 with the MS3X expander and the V 3.57 board will require the fewest changes. The 3.57 has jumpers to enable pullups and the MS3X board has your 2nd trigger input. You also have the choice of using the BAC circuit on the main board or the MS3X board.

Most of the sensor wiring is the same as on my writeup. However the new wiring harnesses from DIY have the proper shielded wires for the CAS already installed and there are some changes for sequential injection. It's pretty well documented here:

http://www.diyautotune.com/tech_arti...zda_fc_rx7.htm

 

So all the CAS shielded wiring is there and I dont need to add any shielded?

How well does the BAC respond to let say... a half bridge... at idle? If not well i wont bother putting it in. But after reading your article I really WANT to leave it in..

Should I run sequential injection? How does it respond in a rotary?

Thanks for the reply aaroncake!

 

The new DIY harness has a twisted pair VR input wire, but I made a mistake as there is only one. You'll have to add another:

http://www.diyautotune.com/catalog/1...eady-p-43.html

They should clarify their description. Not a huge deal to add another wire though. The MS3X harness (needed for MS3X sequential injection) has a cam input which would need to be switched with a shielded cable.

The BAC isn't going to be much good regulating your idle since it will be around 1300 - 1600 RPM anyway but it will be a great help on cold start.

With your bridgeport sequential injection is less important, but since you have the capability on the ECU, why not run it? You might be able to achieve a bit better idle (though I don't notice this on my sequential Microtech and bridgeport).

 

With a half bridge, closed loop idle speed control may give you some trouble. Warmup only mode will work easily enough.

Sequential can make a large difference in drivability (better responsiveness) and economy. Especially on more heavily ported engines. On my stock port NA rx7, once I went to sequential and got the injection timing right, my idle AFR went down into the 11:1 range, and i was able to considerably reduce the amount of fuel needed at idle to maintain the AFR I had previously used. Additionally, I found I needed dramatically less accel enrichment to get good response.

So I highly recommend sequential fuel on the rotary. I would expect with a more aggressive port job, the effects I saw would be amplified.

Ken

 

This is surprising to me, did you ever mess with the injection timing to try to get a better result? I would expect on the more aggressive port jobs there would be things like charge stealing that proper injection timing might fix.

In any case, compared with batch injection, you should be able to improve throttle response with sequential, and possibly fuel consumption.

Ken

 

Several years ago I tried adjusting injector times but didn't see much of an effect. It is possible that the Microtech is so crude as far as PW at low loads that injection time really has little effect. It's something I should revisit when I'm bored.

 

Ill try and get the sequential to work when the time comes. It will need alot of tweeking to get it proper. The car is not really going to be a street car. More of a drift/weekend car so economy doesn't really matter. The responsiveness would be nice though..

BAC will be going in then cause i hate cold starts in a rotary.


What about the MS3X harness with having to put in the other shielded?
http://www.diyautotune.com/catalog/1...s3x-p-451.html


Also a random question.. Whats the highest hp youve seen out of a 13b with MS?

 

The cam input on the MS3X harness appears to be unshielded according to the DIY website so you'll want to swap that with a shielded twisted pair.

The highest HP 13B I've tuned with a Megasquirt (on an old Megasquirt 1) was just over 400 RWHP on a healthy half bridge and a 60-1. Also 6 port, high compression. Done several in the 380HP range as well.

FWIW I also tuned a twin GT35R 302 V8 on MS1, but that didn't work very well due to un-Megasquirt related issues. Best it did under my tuning on the dyno was about 600HP. I gave up at that point because I was fighting a lot of issues (including a MOUSE IN THE FUEL TANK).

 

So 500hp in a rotary isnt too unreal...


Looks like ill need some more electronics help with doing this shielded wire thing...

 

Aaron Cake, I have a friend here in Spokane, WA that used to build pp for racing on the local circle tracks. One of his tuning tricks was to retard the ignition timing 30+ degrees till he got a smooth idle, then he would do all of his adjustments and reset the timing. I've always wondered if you could set the MS up to idle a pp or bridgeport with the timing retarded to a smooth idle and then ramp back up to operating rpm for better drivability.

 

Not sure what that would accomplish on a modern fuel injection system. If I had timing retarded 30 degrees than set it back to the 10 degrees I would typically idle an engine at, I suspect I'd then have to pull 50% out of injector times to get the AFRs back steady.

 

I was talking about all the time, having a smooth idle with the retarded timing and transitioning to normal acceleration when the throttle is pressed down. Would kinda make it a sleeper since it wasn't idling high with a lope. Just one of those hummmmm questions the float throught the mind now and then. LOL

 

My guess is that the ultra smooth idle was obtained because the AFRs were VERY rich. A bridgeport will idle fairly smooth with AFRs in the 10s, but will foul plugs quickly and burn the eyes of everyone around.

 

LOL I'll bet. Well I'm looking at building a 1/2 bridgeport this summer. along with a ms3x so I'll let you know what happens