[Diy_efi] Can anyone diagnose this engine problem?

Tue Feb 22 06:42:30 GMT 2005

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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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<DIV>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<BR><BR><B><I>joeld &lt;joeld at ualberta.ca&gt;</I></B> wrote:</DIV>
<BLOCKQUOTE class=replbq style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #1010ff 2px solid">Ok, been trying to figure this out for far too long. Maybe someone on here can <BR>provide some insight.<BR><BR>What we've got:<BR>-polaris 600cc 2-stroke 2 cylinder snowmobile engine bottom end<BR>-our own billet cylinders and head<BR>-injectors in the cylinder walls<BR>-running a motec M4<BR>-centrifugal supercharger<BR>-45psi fuel pressure<BR>-88pound/hour injectors<BR><BR>What its doing:<BR>It will rev up and idle perfect, right to 4500rpm or so and then it surges, as <BR>can be seen in this video http://www.putfile.com/media.php?n=100_0008 . When <BR>it is surging, I am holding the throttle steady.<BR><BR>We've tried timing, all sorts of fuel map changes, fuel pressure, 3 different <BR>crank sensors (2 magnetic and one optical), adding fuel with a squirt bottle <BR>right at the supercharger, running without the supercharger. Nothing changes <BR>at all. We are totally stumped. Its
 not the rev limiter, we've ruled that out <BR>as we have it set at 18,000 and it sounds different when it cuts in. Even the <BR>motec guys have no answers yet. Does anyone here have any ideas? This is a <BR>university SAE project and we have to go to competition in 2 weeks.<BR><BR>Thanks,<BR><BR>Joel Day<BR>4th Yr. B.Sc. Min Eng<BR>2004 C.S.C. Project Coordinator<BR>Home: 780-434-9294 Cell: 780-722-5376<BR>C.S.C Team Website: www.ualberta.ca/~uacsc<BR><BR>_______________________________________________<BR>diy_efi mailing list<BR>diy_efi at diy-efi.org<BR>http://lists.diy-efi.org/mailman/listinfo/diy_efi<BR></BLOCKQUOTE><p>__________________________________________________<br>Do You Yahoo!?<br>Tired of spam?  Yahoo! Mail has the best spam protection around <br>http://mail.yahoo.com 
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