800 EFI Big Bore fueling?

Idcatman3 · Apr 21, 2014

What's the largest big bore anyone has run on an 800 EFI with a fuel controller?

Just want to make sure there's enough adjustment to run a 975. I'm not that familiar with the EFI setups.

Reeb · Apr 22, 2014

I won't know until next winter. But the plan is to do exactly that. I'll tune it with a box first, but if I can get it to be fairly consistent across the board, I'm just going to adjust fuel pressure as needed and go that route.
After running the Cutler 1 Liter with no controller for the past 8(?) years and going thru half a dozen controllers only to find it runs the best it ever had without one, I'm hoping the 975cc might end up similar.
I'm interested to see if someone chimes in and sheds some light on the subject.

mike_s · Apr 22, 2014

Subed...

Idcatman3 · Apr 22, 2014

It's just annoying that the 800 and 900 ECUs are physically different. You can't just re-flash the 800 to the 900 specs.

I see that the fuel pump and injectors are the same, so assuming you can control to 100% duty cycle with a controller, you should be able to run the same amount of fuel through the 800 system as the 900? Someone correct me if that's wrong.

RACINSTATION · Apr 22, 2014

You should be just fine. We did a couple King Cat's with 1150s on them with an EFI setup and they worked just fine. Not as consistent as a carb on this engine, but works fine either way.

arcticcatwill · Oct 28, 2014

I used a 2.5* advanced timing key and ran it backwards in my 800 motor that I converted to stock 900. The only difference I could find other that part numbers and shapes was the timing between the 800 and 900. Before the timing key I had a super hot mid range without bumping the throttle a lot like 1400-1600 if I wasnt paying attention. After the timing key 1200 was all I ever saw. Thought the info might help ya.

Only other thing I used was a fuel pressure regulator. 49psi I think???? Put about 5000miles on with this if thats enough to prove anything...

Will

Booster · Jan 7, 2015

I have an 1150 cutler in my M8 running efi and a Boondocker CB, have had no problems so far. I have twin Jaws and a 2 degree advance key with the medium domes. I run at 9 to 12k feet and basically just run the mid-range on the richer side to keep it under 1150 degree at mid-throttle.... these setups hate cruising speed. You can see my sled in 'Member sled builds" under "King big twin in M series"

Booster · Jan 7, 2015

There is another M-Series we did in the 'Member Sled Builds' under the title
"1147 found a new home" if you guys are curious but this one uses 46mm carbs

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800 EFI Big Bore fueling?

Idcatman3

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Reeb

Modding mini's

mike_s

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Idcatman3

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RACINSTATION

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arcticcatwill

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Booster

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