Fuel injection

[Grove]

Hi all.

Ive got a slingshot 1100 engine, it’s a dot engine and been bored to 1216. How easy is it to fit fuel injection and what parts would be needed? It’s being fitted into a Martek pikes peak frame and the carbs I’ve got won’t fit into the frame.

cheers paul

[Upshotknothole]

Check over in the forced induction section, that's where most of the FI conversions happen around here. How tight is the space around the intakes?

[DAZ]

Also check @imago 1100g  and @davecara 750m in the project section as they are both on with fitting 1250 bandit/gsx based injection ...

[Grove]

5 minutes ago, Upshotknothole said:

Check over in the forced induction section, that's where most of the FI conversions happen around here. How tight is the space around the intakes?

it’s quite tight. Can’t get the carbs high enough to line up with the rubbers they hit the top frame rails

[Upshotknothole]

28 minutes ago, Grove said:

it’s quite tight. Can’t get the carbs high enough to line up with the rubbers they hit the top frame rails

Using standard CVs or flat slides? The dot heads do raise the intakes up a bit. You could probably fit flat slides in there, these are RS38s mocked up on a b12 engine in an 1100 frame.

I also run RS38s on an 1127 in a 750 frame, which your frame looks closer to clearance wise.

I think most of the FI conversions are still a mix of GSXR 600 or bandit 1250 intakes and aftermarket computers and trigger wheels.

[Grove]

9 minutes ago, Upshotknothole said:

Using standard CVs or flat slides? The dot heads do raise the intakes up a bit. You could probably fit flat slides in there, these are RS38s mocked up on a b12 engine in an 1100 frame.

I also run RS38s on an 1127 in a 750 frame, which your frame looks closer to clearance wise.

I think most of the FI conversions are still a mix of GSXR 600 or bandit 1250 intakes and aftermarket computers and trigger wheels.

They are cv standard carbs. The rs38’s do look a bit smaller top end and could possibly fit 

[Dezza]

When you say dot engine do you mean you have a dot head on an 1100 slingshot engine bored to 1216? If so, wouldn't that send the compression ratio through the roof? As upshot states, BST38s are a physically large set of carbs and a dot head changes the angle of the carbs reducing frame clearance. RSs are definitely more compact and will also probably be a lot easier to set up.

[Grove]

On 6/30/2024 at 10:57 PM, Dezza said:

When you say dot engine do you mean you have a dot head on an 1100 slingshot engine bored to 1216? If so, wouldn't that send the compression ratio through the roof? As upshot states, BST38s are a physically large set of carbs and a dot head changes the angle of the carbs reducing frame clearance. RSs are definitely more compact and will also probably be a lot easier to set up.

Hi mate. I’m going to be totally honest you have lost me. I brought the engine like it fully rebuilt. The bloke told me it was a dot head, it’s got the dots on the side. He said it would be great for the frame and a good strung engine. Changing the angle of the carbs could well explain the clearance problem as I’ve seen these frames with the 1100 engine in and the standard carbs.

[Upshotknothole]

Dot heads came off 88/89 750s originally and were a cheap upgrade for bandit 1200s, as you got higher compression and more aggressive cams. Usually don't get used on built up engines as most 1216 kits are high compression and the dot head raises the compression even more to where they're not usable on anything but race gas. That can be fixed with the addition of a spacer in the base plate to get the compression back down to something reasonable for street use.

[Gixer1460]

Or if it has Busa pistons (to give the 1216 capacity) that would lower the potential CR down to reasonable levels?

[Upshotknothole]

7 hours ago, Gixer1460 said:

Or if it has Busa pistons (to give the 1216 capacity) that would lower the potential CR down to reasonable levels?

Yeah, seems like there are a few ways to get reasonable CR while using a dot head. Other thing I was thinking was maybe they swapped it to replace a shim head to have access to more cams.