[Diy_efi] Can anyone diagnose this engine problem?

[Rick McLeod]

I have herd a very similar 'audio' from one of my
cars, it has a park/neutral rev limiter that modulates
the injectors anytime it sees RPM in park/neutral
exceed about 3000 RPM.

Therefore, my question: is your injection computer rev
limited? Could it be it came from an application that
is 4stroke low rev?

Just a thought, based on the audio clip, it actually
sounds like everything is working as prgrammed, and
hitting a rev limiter?



--- Bret Levandowski <skishop69 at yahoo.com> wrote:

> We do a few mods with our sleds as well. Though, we
> use Arctic Cats because they're already injected.
> Injectors in the cylinders instead of at the crank
> base aren't as efiicient and generally suffer form
> heat soak. That's why 'Cat moved them to the base.
> I'd hook your injectors up to a good scope and check
> the readings. Also, make sure you've got good ground
> and driver connections. In the video, it sounds like
> the injectors or ignition is cutting out. Since you
> say you've eliminated the ignition, that only leaves
> the injectors. If you're not running an O2 sensor,
> you should consider hooking one up. A wideband would
> be your best bet to monitor if it's going lean
> enough to cause you're problem. Unfourtunately, the
> reason they don't use them on two strokes is the oil
> doesn't react well with them. It should be useful
> long enough to see what's going on. My best guess
> (all though not that great) is that you've got an
> ECM hardware problem or you're injector windings are
> cooking. Ski
> 
> joeld <joeld at ualberta.ca> wrote:
> Ok, been trying to figure this out for far too long.
> Maybe someone on here can 
> provide some insight.
> 
> What we've got:
> -polaris 600cc 2-stroke 2 cylinder snowmobile engine
> bottom end
> -our own billet cylinders and head
> -injectors in the cylinder walls
> -running a motec M4
> -centrifugal supercharger
> -45psi fuel pressure
> -88pound/hour injectors
> 
> What its doing:
> It will rev up and idle perfect, right to 4500rpm or
> so and then it surges, as 
> can be seen in this video
> http://www.putfile.com/media.php?n=100_0008 . When 
> it is surging, I am holding the throttle steady.
> 
> We've tried timing, all sorts of fuel map changes,
> fuel pressure, 3 different 
> crank sensors (2 magnetic and one optical), adding
> fuel with a squirt bottle 
> right at the supercharger, running without the
> supercharger. Nothing changes 
> at all. We are totally stumped. Its not the rev
> limiter, we've ruled that out 
> as we have it set at 18,000 and it sounds different
> when it cuts in. Even the 
> motec guys have no answers yet. Does anyone here
> have any ideas? This is a 
> university SAE project and we have to go to
> competition in 2 weeks.
> 
> Thanks,
> 
> Joel Day
> 4th Yr. B.Sc. Min Eng
> 2004 C.S.C. Project Coordinator
> Home: 780-434-9294 Cell: 780-722-5376
> C.S.C Team Website: www.ualberta.ca/~uacsc
> 
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