Injector Positioning - Max distance from intake valve

[danc8000]

Gentlemen,

Can anyone offer any information on this?

What's the longest distance people have used for injector positioning relative to manifold face (or intake valve position) that has been fine for cold starting with no form of heating for the intake? If you do put forward an answer on this can you say what engine size you are using, cranking speed and a few notes about your intake shape/design.

I'm not talking about having a second set of injectors behind the butterflies here, purely the distance from your closest set of injectors.

The wet manifold I am using is not working out great for cold starting. I'm still playing with pulsewidths a little but it's a battle between too much fuel for the small cranking airflow to carry and liquification on the port/manifold runner walls.

Just wanted to see how other people's setups compare. Anyone got a heater anywhere?

Cheers

Dan

[danc8000]

Anyone??

[efahl]

Here's a picture showing one Italian manufacturer's injector location; I believe they warm up the engine before starting.



I don't think many people can help you, most of us have the injectors right down on the valve. Mine are located right in the head, not even back in the manifold, and I get instant starting even in negative F temperatures.

Eric

[cng1]

"efahl" wrote:
> Here's a picture showing one Italian manufacturer's injector location; I believe they warm up the engine before starting.

They also couldn't care less about what happens below about 10000rpm
which helps a bit!
Posted by email.

[Mike_Robert]

Well, on my rotary, there is about 17" from the injectors to the intake ports in the housings. It took a bit of trial and error to get my warmup correct but it works OK now. Luckily I'm in S FL so don't have to deal with extreme cold; I imagine this would be problematic with wall wetting, long time to manifold warmup, etc.

-Mike

[danc8000]

Thanks for the replies guys and nice pic too.

[alfa75ba]

Hi,

In my racing car I have 1,4 lit engine from FIAT Tipo. For fuelling I used 2x Dellorto DCOE 40 carbs, but after I put together my Mega Squirt and sorted out sensors, fuel pump etc. I had to put the fuel injectors somewhere.
I did not feel like drilling holes in the manifold ( to be able to switch back to the carbs if neccessery) so I just put four pieces of aluminum pipe in the carbs ( after taking the chokes and venturi and fuel jets protruding down in the air inlet- it takes like 5 minutes), and mounted the fuel rail with the injectors outside.
It did not look great, but worked like charm.
Later on, I managed to make some sort of cold air intake with Alfa Romeo air box and hide those injectors inside-also removed those ugly looking braces and screws).

Summary:
Although four 38mm (1,5 inch) ITB might be too big for this small engine ( 1372 ccm= 84 CID), fuel injectors are also quite big (170 cc = 18,3 lb) and positioned some 25 cm ( ca 10 inches) from intake valves, the engine starts and idles great ( better than ever on carbs).
It idles on some 850 rpm /60 MAP (I have quite low but stable MAP signal) and is happy when slightly richer (0,8 Volts on narrow band O2 sensor).
This I still cannot fully understand:
The injectors are spraying directly into the closed butterflies ( just barely cracked opened-with this 38 mm intakes it takes 1 mm to rev the engine ) but the engines idles smoothly and stable. And it drives great as well, although not yet fully tuned
The Mega Squirt Rocks!
Many thanks to all who made it happen.

Regards, Drazen

PS. I tried to attach some pictures, shall see if they would appear