Can direct injection engines start without a starter motor?

won't work.

for diesels, it's not the pressure of the compression stroke that ignites the fuel, it's the adiabatic heating the compression causes. once an engine stops, the heat in any compressed air charge quickly dissipates. once gone, nothing you inject will ignite.

for gasoline, while the adiabatic heating it not as extreme as diesel, it's still present and very much crucial to vaporize the air/fuel mix when charged, and to raise its temp to the point where the spark will "tip it over the edge" and ignite.

for either engine, the crank never comes to rest at or near the very top of the stroke on switch-off. the more pistons, the closer you might be to having one of course, but for most common 4, 6 or 8 cylinder engines, no cylinder will be compressed quite enough.

it's also hard to have the engine computer "choose" which piston to try and fire - most systems only know one spot on the crank, and that's tdc on #1 piston. and that's not known until the sensor is triggered, and that requires rotation - iow, it's "blind" once the engine is turned off. you could change the sensor system and keep info in non-volatile memory, but given all the above, it's something of a pointless exercise, both computationally and financially.

My 1914 Ford Model T doesn't have a starter motor, but soon as the engine is warmed up, when I shut it off whichever cylinder has a charge of gas in that cylinder the engine will usually start running when I turn the ignition switch on. cuhulin

It is doable. In the '80s Ford built an engine with no cam and computer controlled solenoids to open and close the valves.It could start without a starter motor.

One of the demonstrations I do for my students is to start an engine with a soldering iron.It works great with GM Hei. I set the motor up a bit past tdc on #1 and prime the cylinder with a few drops of gas and leave the ignition on. When the students show up I take a big transformer style soldering iron, hold it next to the distributer. When I pull the trigger the hei makes a spark and (most of the time) the engine fires up. Makes a great discussion starter. HTH, Ben

did you personally see it run? because i think that's urban legend. all the solenoid controlled cams do is allow reselection of which piston to fire, they have no more bearing on the thermodynamics inside the piston than cam controlled valves.

did you warm the engine up prior? otherwise you have a freshly primed super-saturated fuel/air mix [in excess of what would normally be possible - since condensation and run-down would prevent it], you have an inductively triggered spark [again something not normally possible] and you have a crank position never found on any normally stopped engine...

why not go for one of these?

There is a certain way/method (using the hand crank) to start a Model T Ford (and similar cars of that vintage) and if you don't abide by that certain way you could wind up with a busted wrist or thumb or knee.Those old vehicles/engines can back fire and start runing in the wrong direction. cuhulin

Mazda SISS. However, it is unclear whether this technology actually made it into production cars. Mazda seems to have planned to introduce it in 2009, but did it actually happen?

the two pain points to take away from that link are:

1. the engine has to be stopped with a piston /after/ tdc, which is no small control issue.
2. the engine needs to be hot.

neither of which are going to make the conventional starter motor go away any time soon [and certainly not for diesels], unless we all just go for hybid technology and be done with it.

Wouldn't all that stopping and starting of the engine put extra wear and tear on the starter motor? cuhulin

Any direct injection gasoline engine can start without a starter motor. The y produce a high pressure(most injectors for GAS DIRECT INJECTION/or SIDI f or GM)between 500 to 2900 PSI depending on the platform. The fuel injectors also run around 60 to 70 volts as opposed to the traditional 12v injectors . They also have the ability to fire one to three times per event and run o n compression rations of 11:1 to 13:1. They can run on multiple mods includ ing stratified, stratefied homogeneous, homogeneous anti knock, homogeneous lean, and homogeneous.

I don't think that you'd want to spin the engine over by using fuel pressure... the compression stroke would hydrolock the engine, which tends to be detrimental to future functionality.

However, you do raise an interesting point, that with modern engine controls, it might be possible for the engine computer to "know" which piston is just past TDC on its power stroke, inject a small fuel charge into that cylinder, then fire the plug, then proceed to the next cylinder etc. until the engine is running normally. Sort of analogous to an antique aircraft engine started with cartridges.

There must be a reason this approach is found lacking however - immediate thoughts off the top of my head

To my knowledge nobody has implemented this approach yet; my direct-injected BMW engine still has a conventional electric starter, as does Hyundai's and every other mass produced DI engine.

HOWEVER - I'm finding this line of thought interesting, and if it could work, would make an interesting ECM program addition for a backup starting method in the event of an electric starter motor failure; sadly not an uncommon issue with BMW N54/N55 engines from what I read on the forums. Rather than leaving one stranded, such a scheme would result in the engine starting but with an error message on the dashboard e.g. "Starter motor failed, repair at earliest convenience" or something like that.

nate

My T Model Ford car will be 100 years old in 2014

wow! excellent example of a specious argument.

GW

Geoff Welsh wrote in news:l63tb1$bng$1@dont- email.me:

Not specious, but silly. OP must be going on book-learning and nothing else. Or else he's just having fun trolling.

OP is forgetting three very important things:

2) Time. What is the duration of the injection at 2,000psi?

Why is it that 15,000 volts from a spark plug won't kill you, while 600 volts from an industrial fuse box can? OP won't be able to answer that one.

Compressed-air starters were common on higher-end cars before electric starters becme practical. There's a reason why they're not around anymore.

There were compressed air powered Locomotives that operated in coal mines too.

And of course you've witnessed this? If not, perhaps it's a candidate for Discovery Channel's MythBusters. Sincerely,

I'm not sure why anyone would think spraying high pressure fuel into the cylinder would be useful for starting. You don't get a lot of volume, and if you DID get a lot of volume, you'd get hydrolocking.

Now. a high enough pressure supercharger, THAT you might have some luck starting with.

Or just park it on a hill like I did with my Lada that had no functioning starter.

--scott

Not to mention aren't most modern fuel injected cars running between 50 and 70psi at the injectors anyways? That's a far cry from 2000psi. Maybe a diesel would be more interesting?

nd 70psi at the injectors anyways? That's a far cry from 2000psi. Maybe a diesel would be more interesting?

Wayyyy back in the Tin Lizzie years, some people would 'show off' by kickin g a front tire of their T Model Ford cars and the engine would start runnin g. What it was, the engine was already warmed up, they would switch off the ignition and then pull on the crank handle to make sure one of the pistons was on the compression stroke, then switch the igniton back on. Kick a tir e, Ipso Presto, the engine would start up.

Same basic trick you use to start some old hit/miss engines.