New Injectors....

[ratter]

good to see you got to get them running correctly

[straughsberry]

The factory fuel system is 4 bar at 0 KPA yes? So, by adding 25psi of boost to the factory fuel reg, we should end up with just under 6 bar of fuel pressure. And if that is the case, doesn't that mean we will roughly have the capability to make 570rwkw from the Siemens 60's? At 6 bar the Siemens 60's will flow at just over 900cc making them capable of much much more than 430rwkw. What are your thoughts?

What difference, if any, will the single nozzle make in tuning? Perhaps we may get some wetting on the top and bottom of the port? Will this affect the quality of the burn?

[Headsex]

60lb injectors run out at about 450rwkw. maybe less, depending on your commanded air fuel ratio!

Sure, The injectors will flow more at higher fuel pressure, But your theory only works in a Naturally Aspirated vehicle.

Adding 25psi of boost, and rising the fuel pressure to around 6bar still has a 4bar pressure differential over the injectors feed and tip. Therefore the injector still see's 4bar pressure.

[straughsberry]

I may be missing something here. If you have a higher fuel pressure, whether by a higher rated regulator or by running 25psi boost behind the factory reg, then you have more than the factory 4 bar pressure correct?

Now lets say we are running 24psi. We should have around 5.5 bar or 80psi behind the factory fuel reg. It shouldn't open until fuel pressure reaches 5.5 bar yes? So if the fuel system is feeding 5.5 bar into the injectors, how do the injectors only see 4 bar? And if we have 5.5 bar of fuel pressure into 646cc injectors (whose flow is rated at rated at 3 bar), doesn't that mean the injectors are now flowing at about 80lb?

[Headsex]

Not to sound rude, but yes, your missing it.

Lets go back to basics.

Take these 80lb injectors.

If you have a naturally aspirated car, running 2.7bar(39.16psi) fuel pressure. The injectors will flow 75lb

If you wind the fuel pressure upto 3.5bar(50.7psi). The injectors will flow 85lbs

If you wind the fuel pressure upto 4bar(58psi). The injectors will flow 90lbs

Now remember one thing...... Your Naturally aspirated. So at wide open throttle, there is 1 Atmosphere pressure(absolute) in the engine (ie, What we all breath right now) or better yet, 0 Atmosphere pressure(relative).. ie, THERE IS NO BOOST.

Now lets take a boosted car for example. The purpose of the fuel reg is to Rise fuel pressure when the pressure inside the manifold raises. Ie, when your making boost. MOST Regulators have a 1 to 1 relationship. So every PSI boost increase, will have the same PSI increase in fuel pressure.

SO.. Example.. Once again,

If you are running 2.7bar(39.16psi) fuel pressure. The injectors will flow 75lb

If you have 15psi, your fuel pressure is going to be 15psi HIGHER than what it was at 0psi. So, you have approx 54psi (3.7 bar). But The injectors will still flow 75lb.

Although you have HIGHER fuel pressure. You now have 15psi resistive pressure on the outlet side of the injectors.

Taking our 4bar base fuel pressure, the injectors flow 90lb Base, with NO boost

Add 15psi boost to it (approx 1 bar), then you have 5bar fuel pressure, But you also have 1bar boost pressure on the outlet of the injector. So the increase in fuel pressure is negated by the boost in the manifold. Hence the injector STILL SEE"S 4 bar fuel pressure.

[Headsex]

Now lets say we are running 24psi. We should have around 5.5 bar or 80psi behind the factory fuel reg. It shouldn't open until fuel pressure reaches 5.5 bar yes? So if the fuel system is feeding 5.5 bar into the injectors, how do the injectors only see 4 bar? And if we have 5.5 bar of fuel pressure into 646cc injectors (whose flow is rated at rated at 3 bar), doesn't that mean the injectors are now flowing at about 80lb?

Your forget that there is also 24psi in the manifold, providing a resistive opposing pressure on the outlet side of the injector. So the pressure differential is Fuel Rail pressure minus manifold pressure.. Ie, 4 bar!

[straughsberry]

Nar you don't come across as rude. More of a smartarse-like attitude is prevalent But seriously, this is an open forum and we are here to discuss, learn and challenge to infinity and beyond.

But the surface area of the inlet side of the injector is much greater than the surface area taken up by the 4 orifices on the oulet. So will 24psi on the 4 orrifices of the outlet still negate the 24psi on the injector inlet, given its what, 20 times greater or so (that's a stephstimate)? Don't we have a ratio to consider here, as far as the disc(inlet) to orifice(outlet) size?

[Headsex]

the pressure difference occurs at the most restrictive point, ie, the metering disk. So there's 1bar boost on one side of the disk, and 5bar fuel pressure on the otherside of the disk.

[straughsberry]

mmm. Interesting theory

[Headsex]

Basic physics. It's fact not theory