MSII software and firmware

zymodude · Post by **zymodude** » Mon Mar 20, 2006 5:57 pm

Hi all

A couple of things I wanted to ask about.

1. Does any one else have issues with the 'real time display' hanging after a few minutes use?

2. Rev limits - I can set either fuel cut or ignition retard in the software. seeing as I am running a turbocharged LPG setup, I have no injectors to cut. My only option is to retard timing by the max limit of 10 degrees.
As I suspected, this will not hold back an angry turbo motor! Retarding by 10 will only drop it to 2 deg BTDC from 12 BTDC. I over revved the motor twice yesterday. Once was taking off hard with intent to wheelspin, the other was just taking off, nail the pedal, boost comes on, tires go bye bye, engine wailed to over 8000 in a blink before I could back off! This was with the ignition retard set to 7500.

So, is there any code out there to actually cut the ignition instead?

Pete

mops · Post by **mops** » Mon Mar 20, 2006 6:21 pm

i believe there's a spark cut available somewhere..... at least I remember ppl talking about it....

i have sometimes issues with realtime display, but i traed it down to faulty com port on the docking station.

I aswell noticed that with seriabl cable connected to computer and running megatune the MS2 unit runs hotter....

turbo lpg... how that compare to turbo petrol ? do you have like lpg carb or maybe just single point big lpg injector ??? i mean... uh.... if you got no injectors then why do you need ms for ?

zymodude · Post by **zymodude** » Mon Mar 20, 2006 6:47 pm

http://zymo.homemail.com.au/bmw2.htm

Something has gotta run the spark ?

Pete

zymodude · Post by **zymodude** » Tue Mar 21, 2006 1:42 pm

no more takers on cutting the spark?

any official comments on the Real-Time hang issue?

Pete

mops · Post by **mops** » Tue Mar 21, 2006 1:55 pm

well, yes, there is a cut spark way you could implement.

it's a bit of mucking around really....

you would have to use a relay and one of the spare outputs of MS.

now, realey would be driven by one of the serial outputs in MS and will join the ground and negative side of coil.

basically all the time you want the relay closed, unless your rpm is too hight, then you open it, so that coil cant ground = no spark. you might close the relay again once revs drop to 7k rpm or something...

jonfx4com · Post by **jonfx4com** » Thu Mar 23, 2006 2:15 am

I see a problem with ignition cut in this application. The spark cuts but the engine keeps pumping compressed mixture into the exhaust manifold, turbo and system, then when the spark comes back you might have a big bang. I'm not up on this particular subject but it sounds like a bad idea to me. Can the relay not we wired to do a fuel cut somehow.

Jon

zymodude · Post by **zymodude** » Thu Mar 23, 2006 2:24 am

I hear what you are saying, yes it will probably make some almighty cracks out the exhaust, but it also depends on the coding as well to a degree.

Another thing is that if the primary and secondary cut is used, the 'off' time is guaranteed to make some almighty bangs! However, if the primary and secondary are both set to say 7500rpm, the effect is a lot softer with a much higher repeat rate and less time for fuel to build up.

Another thing is that the limiter is not there to tell me when to change gears, it is there to stop the engine turfing its rockers off the pivot posts or even throwing a rod through the side should the revs really get high. I have already seen how quickly it shot past 8000rpm, the danger of it blowing is pretty real. A missed shift would be worst of all, forget wheelspin! A popped muffler I can deal with, broken engine parts sucks!

Pete

rb26dett · Post by **rb26dett** » Thu Mar 23, 2006 11:18 am

any of the fast drag cars use a spark cut to keep the revs constant for a few seconds prior to launch. they seem to have the hysterisis set very low though, so its more of crackle crackle than BANG.

I have a basic system on my ute to do the same (until the megasquirt and dohc motor replace the sohc carby one) and there are no big bangs there either.

busta9876 · Post by **busta9876** » Thu Mar 23, 2006 7:24 pm

the MSD ignition rev limiter claims to drop cylindrs, and fire those same ones on the next cycle, to prevent a large build up of fuel, however, on high horse power motors, damage can occure if sitting on the spark cut rev limiter too long.

I saw a guy with a big nitrous fogger stay on the rev limiter for not more then a second and melted the ring land.

if someone could write code to ignore tach pulses randomly at a giving rpm, you could come up with some sort of safer spark cut.