Stand off injectors

[NEK®]

Like seen in this video there are engines with stand off injectors.
http://youtube.com/watch?v=q7FSrJ-FZFI
Even in F1 they use this type of injection.
But wat is the extra effect on it, because it is mostly used with full trottle.
So there's twin injection per cilinder, is this the only improvement?

[dtype38]

Welcome to 10-10ths NEK. I believe the reason for stand off injection is that the fuel can be very evenly distributued into the intake air without any intrusion into the intake tract. This would give benefits both in combustion efficiency and inlet tract efficiency, but has obvious risks from having a fuel mist "out in the open" like in the video. Wouldn't want anyone smoking while doing that sort of test, would you ;-)

[Notso Swift]

The biggest benefit is having a smaller (and hence easier to control) primary injector to handle the low range and the bigger secondary injector that has sufficient fuel delivery not to compromise power at the top. The idea is you have a nice even fuel delivery allowing the maximum from the motor at any particular point. There s also a benefit in mixing the fuel and the air. At Low air velocity the fuel from the high injectors will “fall out” of the air stream, while at higher speeds the air from the low injectors doesn’t have enough time to mix properly. With the current generation of directed injected cars they try and compensate for this by running much higher fuel pressures, between 10 and 25 times higher than conventional systems, and with injectors that can handle very small opening times.

Usually at full load both sets of injectors are firing, so there are 2 switching points, low, high, then low and high together..

I suppose, fundamentally it is the same as a two barrel carbie, at low speeds only one barrel is open, as the volume of air comes up the secondary opens.

[EfiOz]

The biggest gain is in the charge temp drop.

The bit with the dual injectors is just to get around bad injector control in the ECU.

[NEK®]

So it's for a better air/fuel mixture at high revs and so a better effentiency.
But liked said I can imagine that with a poor setting it can not that save.

maby my english is not that good, but your comments are clear enough to understand to me, thanks

[Notso Swift]

Originally Posted by EfiOz

The biggest gain is in the charge temp drop.

The bit with the dual injectors is just to get around bad injector control in the ECU.

Unless you are using an ECU built around the time Noah was trying to fire up the Ark it is nothing to do with the ECU, electrons move at the speed of light and any modern ECU can control then doun to the fraction of a m/S, more to do with the injector hardware. The 'valve' just can't open and close fast enough. Without time fully open the fuel doesn't mist/atomise properly. The new Piezo (sp?) type injectors operate/switch more than 10 times faster than conventional injectors and they have smaler field of motion, to do this they run around 60V, as 12V just cant trigger the switches fast enough.

[EfiOz]

Originally Posted by Notso Swift

Unless you are using an ECU built around the time Noah was trying to fire up the Ark it is nothing to do with the ECU, electrons move at the speed of light and any modern ECU can control then doun to the fraction of a m/S, more to do with the injector hardware. The 'valve' just can't open and close fast enough. Without time fully open the fuel doesn't mist/atomise properly. The new Piezo (sp?) type injectors operate/switch more than 10 times faster than conventional injectors and they have smaler field of motion, to do this they run around 60V, as 12V just cant trigger the switches fast enough.

Unfortunately, that's not always the case, especially with lower end ECU's. They can really struggle to control large injectors when you start talking usecs not msecs.

[EfiOz]

Originally Posted by NEK®

So it's for a better air/fuel mixture at high revs and so a better effentiency.
But liked said I can imagine that with a poor setting it can not that save.

maby my english is not that good, but your comments are clear enough to understand to me, thanks

No, it's more to do with the idea of spraying a liquid into a fast moving air stream and creating a refridgeration effect on the gas as a whole. The nett result is the charge temperature is much lower (and therefore denser) going into the cylinder.

[Notso Swift]

Originally Posted by EfiOz

Unfortunately, that's not always the case, especially with lower end ECU's. They can really struggle to control large injectors when you start talking usecs not msecs.

Fair call, you do get what you pay for (laws of deminishing returns not withstanding) and some of the cheap ones (can you say Saloon cars) are pretty old tech

[Chucky]

I saw a sign on a dyno room wall once that read

"Microtech. Painting dyno room walls black for over 10 years."

I had to look twice as it was done with all the correct logo's and looked legit at first!!