Injector Positioning

blued888 · Post by **blued888** » Sun Dec 25, 2005 1:58 am

Does the angle position of the injector make any difference?

Image attached of two different injector setups.

Thanks.

78Spit1500Fed · Post by **78Spit1500Fed** » Sun Dec 25, 2005 8:24 am

Injectors have (usualy) about a 30 degree spread at the nozzle... The more fuel you can prevent from spraying on cold, solid surfaces the better.

If you want some details about an intake design for port injection, take a look at the "Air Metering" section of my website, link below.

-Brian

efahl · Post by **efahl** » Sun Dec 25, 2005 9:21 am

78Spit1500Fed wrote:The more fuel you can prevent from spraying on cold, solid surfaces the better.

Yup, from what I can tell the max HP guys with no restrictions place the injectors as far from the valve as possible, F1 motors have the injectors 10-20 cm from the air horn shooting directly down the center. For emissions, you typically see injectors as deep in the system as possible, with OEM installations shooting the fuel on the back of the hot intake valve and using timed injection pulses to squirt when the valve is open and thus avoid loss of atomization.

Eric

efahl · Post by **efahl** » Sun Dec 25, 2005 11:06 am

Here's a thread with a (very) pretty picture:

http://www.msefi.com/viewtopic.php?t=12252

Although I've never seen it myself, I've heard from authorities that are very reputable that some race engines have pointed the injectors backwards against the airstream in order to increase transit time and maximize vaporization...

Eric

blued888 · Post by **blued888** » Sun Dec 25, 2005 8:36 pm

78Spit1500Fed wrote:Injectors have (usualy) about a 30 degree spread at the nozzle... The more fuel you can prevent from spraying on cold, solid surfaces the better.

But the first picture will work? This stuff is for our thesis work at school.

PSIG · Post by **PSIG** » Sun Dec 25, 2005 11:25 pm

efahl wrote:
78Spit1500Fed wrote:The more fuel you can prevent from spraying on cold, solid surfaces the better.
. . .squirt when the valve is open and thus avoid loss of atomization.
Eric

Although a minor point perhaps; but rather than keep the fuel atomized - it is an attempt to keep the fuel airborne. Timing the injection allows airflow to draw the cloud of fuel along and into the chamber rather than having it shoot into and stick on a runner wall affecting the mixture (and emissions) for 1 or 3 cycles.

On the other hand - F1 intakes are packing homogenous mixtures into the runners at supertuned velocities, so even when the flow stops momentarily, the A/F mixture remains well mixed even with differential fluid inertia. In-fact, the fuel inertia can help with the vaprization process. Just a different way to 'keep it airborne'.

That's my story and I'm sticking to it. For now.

David

tony2ltr · Post by **tony2ltr** » Wed Dec 28, 2005 5:51 pm

I'm using a jenvey setup on my turbo'd Cosworth vega, but I won't see above 8,500 rpm. The jenvey throttles are bored for secondary injectors, as well as the manifold but I am running into trouble with having room for that secondary rail, it is going to be in the way of the plenum I am putting around the velocity stacks.

Would that "Italian Manufacturer's" setup be ok for my secondary injectors instead of using the bores in the throttles?

Thanks,
Tony

78Spit1500Fed · Post by **78Spit1500Fed** » Wed Dec 28, 2005 9:23 pm

blued888 wrote:
78Spit1500Fed wrote:Injectors have (usualy) about a 30 degree spread at the nozzle... The more fuel you can prevent from spraying on cold, solid surfaces the better.
But the first picture will work? This stuff is for our thesis work at school.

If by "first picture" you mean an arrangement where the injectors are perpendicular to the flow of air, then yes, it will work.

Perhaps better at high RPM's than low, but it will work.

By the by, what's the thesis?

-Brian

blued888 · Post by **blued888** » Fri Dec 30, 2005 2:20 am

Correction, the injectors are tilted by 5° or 10°.

So even though they're somewhat spraying to each other. It will still work? I was worrying because it might take a while for the fuel to drip down from the throttle body walls and onto the intake manifold and into the cylinders.

Another follow-up, it will work because the incoming air will 'push' the fuel downwards onto the intake manifold?

The thesis is an adaptive air/fuel mixture controller. It adjusts based on the driving style of the driver. (Changes are probably not too drastic though)

78Spit1500Fed · Post by **78Spit1500Fed** » Fri Dec 30, 2005 10:57 am

blued888 wrote:Correction, the injectors are tilted by 5° or 10°.

If you're going to go to the trouble of fabricating the intake to tilt the injectors, why not do so in a way that minimizes the very situation you're concerned about?

blued888 wrote:So even though they're somewhat spraying to each other. It will still work? I was worrying because it might take a while for the fuel to drip down from the throttle body walls and onto the intake manifold and into the cylinders.

If there's fuel "dripping" down to your intake valve, you've got bigger problems than injector placement!

blued888 wrote:Another follow-up, it will work because the incoming air will 'push' the fuel downwards onto the intake manifold?

Yes, that's why I suggested that the setup may work better at higher RPM's.

blued888 wrote:The thesis is an adaptive air/fuel mixture controller. It adjusts based on the driving style of the driver. (Changes are probably not too drastic though)

Interesting. The Mercedes ECU's have done this for a while... the Toyota VVTI ECU's (used in their Scion brand) do this to a certain degree as well. All of the present technology is aimed at better economy and emissions, I'm not aware of any adaptive reactionary software aimed at improving power or response.

Keep us in the loop! We're grassroots to the max around here!

-Brian