Author Topic: Air assisted injectors? Is it ok to use them?  (Read 10215 times)

Offline josh-stateside

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Air assisted injectors? Is it ok to use them?
« on: February 15, 2010, 04:53:16 am »
Ok I have some questions:

The 4.2L v8 has air assisted injectors bosch part # 0280150441 (15.9) Resistance (ohm)
At 3bar:   180cc/min
The audi stock fuel pressure regulator is a 4 bar unit so
At 4 bar:  208cc/min
The car came stock with a 12v v6 engine with these injectors: 0280150552 (15.9)Resistance (ohm)
At 3bar: 156cc/min
The audi stock fuel pressure regulator is a 4 bar unit for the v6 engine   
At 4 bar: 180cc/min
So If I wanted to use the v6 injectors i'd have to bump the fuel pressure all the way up to 5 bar
to get
At 5 bar: 205cc/min


Is it ok/safe to run 5bar and use 8 v6 injectors?
Is the stock air assisted injectors ok for now? 
If I replace the injectors should I consider getting injectors for a less pressure based setup?


Thanks
Josh

Offline gunni

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Re: Air assisted injectors? Is it ok to use them?
« Reply #1 on: February 15, 2010, 05:31:39 am »
What exactly do you mean by air assisted injectors?

Offline josh-stateside

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Re: Air assisted injectors? Is it ok to use them?
« Reply #2 on: February 15, 2010, 06:14:15 am »


I read something along the lines that the air assist helps better atomization by making the spray pattern wider or something along the lines.    It's controled by a valve that you typically would find from a carbon canister valve.   So I would have to have an output on vems control the valve to add air to the injectors?  Sounds kinda like a headache no?  There is only one air assist valve for all 8 injectors.

The only catch with swapping injectors is that i'm going to have to have custom adapters made because the nozzle is quite a bit larger than the average injector. 
« Last Edit: February 15, 2010, 06:16:08 am by josh-stateside »

Offline josh-stateside

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Re: Air assisted injectors? Is it ok to use them?
« Reply #3 on: February 15, 2010, 06:29:10 am »
Some more information about them from a different forum and also from a toyota setup and not an audi.  However after looking online for a bit I did notice that BMW, Volvo,kia, and a few others have all used air assisted injectors at some point:

Toyota does claim air assist helps prevent fuel from clinging to the port walls, improves emissions performance, and also idling and overall engine drivability.

Since the older 2-hole non-air assisted injectors lack the air hole just before the injector nozzle, what you'll see, generally, is decreased efficiency and increased emissions - mainly in hydrocarbons, as there will be more unburnt fuel from the larger atomized fuel particles. This is the main reason Toyota's CA emissions 93-95 2JZ-GE adopted an air-assist injector specifically where the non-CA emissions 2JZ-GE did not. The 7MGE injectors will have a spray pattern consistent with older style injectors with less atomization and air-fuel homogenization.

You have to remember that the air assist is actually engine driven air assist (which is why there is a metering device). So, the air going through the air assist hole collides with the fuel particles in the stream just before they reach the 2 holes in the nozzle. This furthers the atomization and mixture of air and fuel even before it is injected into the combustion chamber with the accompanying intake air flow, resulting in greater efficiency. I still don't fully understand the concept behind the reduction of port-wall wetting with these injectors, but maybe someone else can explain that.





« Last Edit: February 15, 2010, 09:29:34 am by josh-stateside »

Offline josh-stateside

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Re: Air assisted injectors? Is it ok to use them?
« Reply #4 on: February 15, 2010, 09:38:39 am »
I'll be honest here.  I'm not that rich of a guy.   I'm allways looking for the easy way out of things.
I started to look at injectors that I could source pretty easily from the junkyard that would work for my application. So far I found some decent injector setups to replace the air assisted injectors.

VW vr6 injectors bosch part # 0280150953 (15.9) Resistance (ohm)

196cc/min at 3bar
 
Vw 2.0L ABA injectors bosch part # 0280150955  (15.9) Resistance (ohm)
182cc/min at 3bar

Vw 1.8L PF injectors bosch part # 0280150902 (15.9) Resistance (ohm)
218cc/min at 3bar
« Last Edit: February 15, 2010, 09:50:23 am by josh-stateside »

Offline gunni

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Re: Air assisted injectors? Is it ok to use them?
« Reply #5 on: February 15, 2010, 08:39:45 pm »
Go for the biggest ones?

These are all relatively small and the ecu will be able to handle controlling them rather easy.

People are running at least double that without issues.

Offline jrussell

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Re: Air assisted injectors? Is it ok to use them?
« Reply #6 on: February 16, 2010, 07:33:05 am »
It's the same principle that Mazda used on the RX7 for those injectors. Only the RX7 has passages in the "block" for the lower injectors and passages in the intake manifold for the upper injectors rather than use specialized injectors. In any case, using them or not may change the fuel maps some but the ECU will run the engine fine either with those or standard injectors. The difference in maps would be dependent on how effective the setup is at increasing atomization.
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