What rpm is the MS and MSII accurate to with leading and trailing spark with the stock CAS?

I had a v2.2 MS running fuel only on my fc a few years ago, but have just recently been getting back into the MS thing.

 

MS2 is more accurate than MS1 with spark timing b/c it uses the closest tooth on the CAS to calculate when to fire the spark instead of the first tooth after the TDC trigger, but in terms of absolutes, I'm really not sure. Steady-state and with properly adjusted lag factors, there's no real reason why it wouldnt be accurate to the degree (MS1) or less (MS2). When accelerating, any form of spark control will be off slightly one way or the other just b/c the computer doesnt always know exactly where the engine is, only when a tooth passes the sensor does it precisely know.

 

Im thinking more along the lines of real world applications. The falling VE at the rpm's Im looking at will probably make even a couple of degrees variation negligable, but Ive heard stories of other EMS's having very serious ignition timing issues at high rpm. Soon Ill be putting together a 12A PP that could see 11k+ rpm.

 

I've never seen a problem up to 7.5k with the MS1, and have been driving with it (and auto-xing) for a year and a half now. MS2 is more capable and faster, it just doesnt have the years of coding that MS1 does, but its catching up fast.

 

I've tested both MS1 and 2 well past 20,000 rpm in a simulated environment (router spinning CAS) and both were spot on when configured correctly. I've personally ran a 12A w/ 8500 shift point for many miles with nothing negative to report.

 

Jitter on the ignition outputs should keep accuracy within .5 degrees (10 usec jitter) at 8000 rpm. I've never done the same test at 11000 rpm, but I'd expect around the same jitter.

Ken

 

Now thats what I wanted to hear. I was shifting at 9700 rpm in my fc, but I was only running the MS as fuel only back then.

Also, I noticed the daughterboard you need for the v2.2 boards also has support for map switching, boost control, onboard EGT amplifier, and launch control. Do any or all of those work on rotary applications, or with the MSII?

 

The MS universe can be a little confusing. I'll try to clarify. There are 2 main variants of the circuit board (the PCB). They are the v2.2 and v3. There are 2 processors that can be purchased. They are the MS1 and the MS2. Either one can plug into either PCB. Each of the processor variants has it's own codebase, they are not interchangeable. MS1 code is written in assembler, MS2 code is written in C. There are 2 main variants of the code; the B&G code (that's named after Bowling and Grippo, the primary developers/inventors/originators of the MS project) and the MS-Extra code, brainchild of James Murray and Ken Culver (aka muythaibxr). B&G's concept was that the project is open source, they develop the hardware and a good solid base code then let other folks extend and modify it if they wish; this what Ken and James have done. The base B&G code does not have rotary support, if you want trailing ignition suppport as well as support for a myriad of input wheels, Extra's the only game to play. There's a metric buttload of other enhancements as well. The v2.2 board has no builtin provision for VR sensing (the variable Reluctance sensor is the thing that senses each tooth on the CAS wheel), the stock V3 board can read one VR sensor. The CAS has 2 wheels so you must provide a separate circuit to read the other VR sensor. A small circuit using an LM1815 chip can be built on the prototyping area of the V3 board or there are a couple of smaller boards you can purchase that have this same circuit. Some of these auxiliary boards also provide for more ADC channels, EGT amps, etc. For example I've attached images of the auxiliary board I use for VR sensing as well as an image of a V3 board with the proto area identified. MSExtra.com is an excellent resource to try and get up to speed on the Extra side of life. It has a phenomenal amount of information in it but has one major flaw that many people find daunting, namely that is has a phenomenal amount of information. The learning curve is steep and you absolutely must understand the general physics and theory of EFI in general. The MS community is pretty good about not flaming newbs and helping people if people are sincere about wanting to be helped so no question is "stupid". Civility is the general rule. Anyway, more than you asked but I'm trying to help folks navigate their way. msextra.com, msefi.com and megamanual.com all have lots of info, some of which has nothing to do with rotaries, please keep that in mind. The MS has been used on everything from lawnmowers to land speed record holding Bonneville Studebakers to bikes to jetskis; I seem to remember a guy in the UK had run a Rolls Royce Merlin or some such really large aircraft engine on it.

 

VR conditioners and proto area

 

Did another scope test, Jitter was occasional, and less than 10 usec.

At 11000 rpm, 10 usec of jitter is .66 degrees.

So I can say with relative confidence that James' and my code is accurate to about .66 degrees at 11000 rpm.

Ken