new feature, hope its ok here?

[offtrack]

I'd like to see a feature this is in my stock OEM ECU.
it is called spark fail, no injection feature.

they have a 2k resistor tied to the - term on the coil back to ECU pin.
the back emf is measured in such a way that it detects this huge pulse.
(coil missing will not trigger this feedback path).

if this back kick is not present , injection is shut down , saving car owner ,
from hydrolock. [ ouch ]

in addition ,one can enable it or disable it , for testing on bench ,etc. (stim)

the circuit need only be a voltage divider 5 to 1 so that 25v back pulse will give 5v to ECU input. and a 5.1v Zener clamp to protect ECU.

this would assure the coil is getting hit and hit hard.
a nice feature of most ECU's.

that's my list for future, MS3 or ?

ALso , make MS3 wider with 2 heat sink rails so I can mount , my
other driver transistors, like Dashpot fast idle and my Direct drive to IAC solenoid (12 ohm coils on both). my transistors look silly on me lid.
The other rail is full due to low impedance injectors.

IMHO, cheers

[gross polluter]

if this back kick is not present , injection is shut down , saving car owner ,
from hydrolock. [ ouch ]

Highly unlikely. If an air/fuel charge does not get ignited, the majority of it gets expelled on the exhaust stroke.

Factory ECUs check for coil signal as a means of detecting a misfire, or failed coil and then throw a check engine light to alert the driver that there is a problem.

[AbeFM]

To first order, air can be compressed as much as you want, and fluid not at all. The fuel would have to make up your compression ratio, by volume, before there was any issue. So if you're running 10:1 pistons, you would litterally need to have engine displacement divided by compression ratio per engine cycle to have a concern about too much fluid.

Figure 2 liter motor, 10:1 compression means 200cc/cycle, or 100/rev. At 1000 rpm, you would be burning 100 liters of fuel per minute. My guess is your motor uses less than that.

[offtrack]

just quoting Jeff hartmans new book.

Imagine a pistion at the top of the stroke, TDC.
you would only have to have more gas in liquid form in that chamber to cause hydrolic lock (forget air that is not an issue).

if the chamber is 20 CC and the fuel is 21cc then you have lock. see?
during lock the air goes right by those rings. see?

the purpose of the spark / fuel lock out is 3 fold (at least)
1: hydrolock
2: crash stops crank ,cas stops fuel , code saves day
3: gas washing down cyl. on to rings is not too good for lubrication.

BTW: the records show people doing exactly this. cranking like fools as most do.

this is not an obscure issue , many books ond EMS discuss these issues at great detail.
IMHO, regards.

[offtrack]

my factory ECM is on my bench test jig right now (running )
test jig applies all signals and monitors all outputs.

the spark feed back pin on this suzuki is pin A1 , if you cut this signal
the injections halts and spark and fuel pump , instantly. (nearly)


the issue is , how many minutes off cranking can fill the combustion chamber.

my tBi can squirt 456 CC/ min at 80% and 43.5psi line.
at cold temperatures the fuel flow at start can be predigious.
300% for required fuel.

it is common for people to crank unit the battery goes flat and they do not care at all, how many lamps glow on the dash board. IMHO.


i think ours is ok , just by loss of CAS.
The spark monitor is just in case , CAS is good and coil dies.

thats my take.

[hassmaschine]

it is common for people to crank unit the battery goes flat and they do not care at all, how many lamps glow on the dash board. IMHO.

that is true, but those are probably not the same type of people who would put MS on their cars.

[MegaScott]

A properly functioning Megasquirt will not inject fuel other than is required to operate the engine, this should never give you a hydrolock condition even if you have no spark, after a certain amount of time with no spark the engine will inevitably stop rotating, no ignition input to MegaSquirt and no injection.

OEM computers that monitor the Spark feedback are doing so primarily as an OBD2 requirement to check for misfire...believe it or not, the ignition voltage can actually increase when there is misfire, so the ECU is looking for a normal window which firing would occur. The OBD2 requirement is such that ANY misfire will be detected and raise a MIL (Malfunction Indicator Light) and store the misfire information into NVRAM.

[AbeFM]

Imagine a pistion at the top of the stroke, TDC.
you would only have to have more gas in liquid form in that chamber to cause hydrolic lock (forget air that is not an issue).

if the chamber is 20 CC and the fuel is 21cc then you have lock. see?
during lock the air goes right by those rings. see?

On a motor like mine, which I concider to be pretty representative, it's 500 cc/ cyl displacement - with
(500 + x)/x = 9
500 + x = 9x
500 = 8x
x = 62.5 cc volume/ cyl

Sure, it would only take a motor with 500 cc injectors 7.2 second to fill that chamber. But at idle my motor has a pulse width of ~1 ms. Tripple that, as you say, and it's 3ms. 3ms once every 1/200 of a minute (cranking speed), and half again since I don't fire every revolution (actually, it's that I fire half as much, bu the factor of 2 remains) and you've got 3 injection per second of 1.5 ms each.

That's 4.5 ms of injection per second. To reach the 7.2 second to fill the cyl (assuming ALL The fuel goes right into the cyl, and none leaks out, evaporates, goes out the tail pipe...) you would need to crank the motor for 7,200 ms / 4.5 ms = 1600 sec.

That's over 25 minutes of continual cranking.

I'm going to say this isn't an issue. Not from that math.

[6040solder]

Well said Abe, glad someone bothered to prove the point. Furthermore, assuming none went out the exhaust ports is ludicrous, a significant portion will remain in vapour form, and the liquid will get sloshed out long before its an issue. Anyone that ever washed out a cylinder on a stored motor with some oil/gas mix and cranked it would know that for sure :-)

[offtrack]

OBD1 ( not 2 , 89-95 all sidekicks, 8v and 16 have this feature) 1.6L
[ a 2k ohm resistor feeding back EMF pulses from coil to ECU)
and fully bench tested and confirmed by J.Hartman. book , he's see it too.

the worse case : (approx)
-40 Degrees, Wisconsin. Canada , etc.
car pointed up hill in driveway.
so cold almost no vaporization at this temp. ( Jeff says worse case is 1:1 fuel ratio in coldest climate, by weight of course) ours is 300% Req_Fuel?

again worse case is TBI and the liquid gas forms, the single injector
flows across the plenum and down to #4 cylinder . (down hill)
Not sure what exact CC in of the combustion chamber,
but cyclinder is 398cc, so 10:1 (to use a simple number) is 40cc compustion chamber. size so hydalock is 41cc.

4 squirts per 720degress.
5.8 mS , required fuel . 456cc/min TBI single inj.

dont some cars engines have upward sloping exhaust ports and is it not possible to be parked with left side up hill?

enough to get 41cc of raw gas?

it is how many cranks do you get , after coil or ignitor shorts or opens.
or if dirving, and the coil opens.

you could be driving down hill too , under moderate power.
I have CAS , I have Injections, and pop the ignitor , smokes.
make a hard left turn down a mountain or maybe going up hill
under hard wot , on sweeping left turn,
exhaust ports , up hill and leaning back all at once.

looks like the engineer that designed my 91 Kick , was worried about something, and it is NOT OBD2, back in 91. sorry.

I suspect most cars just only cut injection on loss of crank CAS.

just 1.3 oz ( tad more than 1 shot glass of whiskey and BOOM , right?)


I learned this by accident , I was sucking the Ign timing advance with a
ECU running on my bench (test jig i made) it would not run or start with out, that coil feed back resisitor.
did lots of cussing ,than light bulb came on, why the resistor? and then jeffs bood has it right there.
any way it is interesting.

I actually played with this line, trying to get it to like 12v square waves.
but no dice, it wanted a hard kick back ,so I put an large inductor where the IGN coil would residd ( didnt use REAL IGN coil cuz of HV issue)

Bingo The ECU woke up and ran like a champ.
i pulled out all timings at all rpm and loads.

thanks for helping with cc am minute math. !

best wishes and cheers to all.

[offtrack]

the key here is it is cold out. very cold.

it doesnt matter how much air is flowing, it will compress no matter.
(mostly)
it is the amount of non vaporized fuel flowing into a given cylinder.
it's a liquid, (spraying fuel helps vaporizartion but is not a guarantee)

if the pistion comes up with 41cc of liquid fuel and hits the 40cc camber
the air will compress to a huge amount and litterly bast around the rings.
what doesnt, just helps the hydolock. see?
no matter , as you can see , there is no more combustion chamber and the compression ratio of the air + petro gas vapor, is infinity. see?

cold engines run real rich when cold, in fact it is mostly liquid
at the low extreme.

the reason it must be so rich is because almost none of the gas vaporizes at these temperatures.

I have the charts here in my book showing these rates.
That is why almost all smog is made at start up. do mostly for this reason.
The CATcon gets real busy.

that is way Propane cars need no choke or the EMS equivalant. CSE.
its a gas vapor already.

this is gasoline ,and it behaves very strangly at -40 degress.
even , I was suprised too.

does this make any since?

[MegaScott]

Fact is, your ECU manufacturer may have documented this issue and programmed the feature into their ECU. Thing is I have never heard of this problem happening with a fully functional Megasquirt.

Find a few instances where this has happened using Megasquirt, and you might have a chance.

[offtrack]

thanks for helping !
well , there is no one here, that would just crank away. anyway as prev. person said. just wanted to add it to the misc. features not needed list.
LOL.

would like to see , fail safe feature,
if map dies, car will run on TPS (alpha N safe mode) (automatically)
that hot CLT (ECT) protection was a cool add. RC1?

yah, I know, MS2 guy connects MT and flips Alpha bit,bingo...... hehehehe

I note that Chev. engines today all have this feature and
will even cut cylinders to shed heat. (retarded timing makes heat)

just saw my friend Blake save his Chev with blown hose.
it never made steam, quite a feature. going real fast on freeway.
I am not asking for that, just a thought for MS3.
was developed on the Corvette and I read they almost never blow engines on the track now, for coolant loss.

cheers,
to ALL !

[Pimp_daddy_Patty]

If you're cranking, the starter will not have enough power to break anything if you in fact do have too much fuel in the cylinders. This has happened to me with an injector that was stuck open. I had to remove the spark plugs to let all the fuel come out.

The point is, the starter didn't have the power to break anything, and if this happened while the motor was running, it wouldn't fill fast enough, any accumulation would go out the exhaust port.

[offtrack]

depends on the battery.
the starter is series wound motor and as such the torque will try to
go to infinity. the only thing stopping it is the winding resistance
and the battery internal resistance (CCA 300 maybe ok, 600CCA bang)

also the ratio of the ring gear to pinion is very high.

many people have posted on other forums, all about see this.
shop owners, etc.

10 hp can be achieved with a starter. 6 avg.

[6040solder]

10 hp can be achieved with a starter. 6 avg.

You are dreaming. I have a 100 amp breaker to my starter, assuming voltage does not sag, the most it can "make" is 2hp, most likely a lot less delivered, all things being inefficient...

I've tested it cranking around without engine help, and never popped the breaker.

I would say though, starters do have enough leverage and torque to damage the rods/headgasket though, but I still have my doubts about this really happening on a well designed motor. strong doubts.

[offtrack]

look again, there is no break from the starter solenoid to the pos. battery post. See that label on on the battery , 500cca ,thats for when its cold outside, and many cars can hit that easy.

the 100 is the charge line.

[6040solder]

look again, there is no break from the starter solenoid to the pos. battery post. See that label on on the battery , 500cca ,thats for when its cold outside, and many cars can hit that easy.

the 100 is the charge line.

CCA is the current the battery makes at a dead short... when at a dead short, the internal resistance ensures that external voltage is not even close to 12v...

I don't need to look again, my vehicle is virtually scratch built, i bolted down that breaker myself ;-)

ps, my battery is 650CCA ;-)

[offtrack]

look up series wound moters DC type.
as you begin to stall the motor (electic motor) the current tries to reach infinity.
ever stall a 1/2 drill motor drilling a hitch reciever for a ball?

it will throw you to the ground. ( experienced by me many times)

why , well again it is a "series wound motor."

is it stalls the field and rotor currents rise together (Kirchhoff law).
and so does the torque. ( limited by the battery and the smoking starter copper windings)
in a parallel motor field current is constant.

Look at your cars schematic of the starter circuit more carefully.

now look at the ratio of the starter pinion and the fly wheel ring gear.
divide big tooth count by the small tooth count,
now you can calculate the torque applied to the rods.

next time you are in a junk yard, try it.
water in the cylinder and crank away. GOODBYE something.
it will make a real bad sound.

these cars start down to -40.

if that isnt clear i can give you the ASE or NEMA pages that explain it all.
with math , photos and computer models.

hope this inspires research.


http://www.engineersedge.com/motors/dc_ ... _motor.htm

1 page: T=KI2a

notice that sharp curve upward that will be the rods bending.

[6040solder]

All true :-)

ever stall a 1/2 drill motor drilling a hitch reciever for a ball?

Ever stall a petrol powered post hole borer?

it will throw you to the ground. ( experienced by me many times)

A 1/2" drill? not me...

Look at your cars schematic of the starter circuit more carefully.

Clear as day in my head right now, once again I designed it from scratch...

DiyAutotune! < the best!

This is true too :-)

What you have forgotten however is the internal resistance of the battery and the very real resistance of the cable to and from that starter. As current tries to go up, voltage goes down, and power doesn't increase as much as you would like.

BTW, I don't disagree that a starter can do damage, just that a well engineered engine will ever have a cylinder full of fuel...