Dual Stage Fuel injectors? 1

[TurboME]

Hi, I've been reading this board for awile but this is my first post.
I'm wondering if anyone here knows much about "dual stage" fuel injectors. I'm not talking about using two differnt sized injectors. I have been told that there are new large injectors that flow like a small injector at low rpm's inorder to give good idle and low end response and flow like a large injector at higher rpm's. I haven't been able to find much info on these. I did find one Japanese company, Power Enterprise, that seems to make a dual stage injector for the WRX but thats all I know. Does this type of injector actually exist and if so who makes them?

 

[2ofdem]

Low impedence injectors can open and close very quickly and can give decent low end response with large flow numbers at full duty cycle.

 

[pulsewidth]

The dynamic range of the injector can be doubled by operating them in once-per-cycle-sequential mode rather than once per rev group mode. Sequential operation is probably the easiest way to get better flow range.

 

[optimum]

Why couldn't you build an injector with two coils. In idle, low load strategy the ECM would energize the first coil to expose a small orfice, then at higher load energize both coils to open it fully? Are you listening Injector Designers? The racing community thanks you.
Tim

Or using two coils one coil would control a 'limit' stop.

 

[Azmio]

Dual stage injector? Interesting, but I would rather let the ECU to command the injector to inject fuel for a short time at idle. At WOT, the ECU would inject the fuel at longer period of time.

Having two orifices or two solenoid for the fuel injector would increase the size of the injectors. This would cause the intake port and water jacket designs to be more difficult than the conventional design.

I also want to add that for fuel vaporization purposes, it is good to have injector as close as possible to the combustion chamber thus giving a good part load response, performance, mixture and emissions. Not to mention the benefits during cold winter in Sweden.

On the other hand, for WOT at very engine revolution, I would like to place the fuel injector far away from the combustion chamber thus giving good fuel vaporization.

Given a choice between two stage injector and two injectors (one near and one away from the combustion chamber), I would rather choose two injectors.

AO

 

[optimum]

W/ 42V it would be small....on race engines big injectors are hard to clean up at idle. The opening time becomes longer than the on time. They are sized for the possible highest load, not idle. Sometimes the shortest possible pulse injects to much fuel!

 

[Azmio]

For 42v, I would imagine that the solenoid injectors would be different from what's available in the market today.

For big race engine, the injector sizing is a bit tricky. Still there are ways around it, for example, we can choose the suitable pressure regulator, we can increase the idling speed, etc.

The F1 engine for example can rev up to 19000rpm, still, it is the same injectors that inject fuel at idle. Of course the idle speed is not low, but they dont really care about the idle emission and fuel consumptions.

On the other hand, the new sport bikes have dual injectors for each cylinders to enable them to have high output while at the same time low idling speed and good idle fuel consumption and emissions.

Once again, there are ways to avoid having to use dual stage injector.

AP

 

[PSlem]

The new Mustangs use a voltage control to the electric fuel pump. Less pressure at idle cleans it up and still allows full flow at high RPM's.

 

[Azmio]

PSlem
Interesting, can you check for me whether the variation in voltage is controlling the built in pressure regulator or the electric motor itself? Nowadays, returnless fuel pump integrates the pressure regulator within the same housing.
The idea of using variable controlled fuel pressure regulator is not new. It is hard to control the electric motor itself because it depends a lot on factor like electric motor aging, battery performance,etc.
On the other hand, if the voltage controls the pressure regulator at certain pressure 3.5, 4 or 5 bars, it will be much easier to control the fuel injector flow.

AO

 

[pulsewidth]

The systems I've seen use a differential pressure sensor to measure MAP against fuel pressure. The fuel pump is then pulsewidth modulated by an ECU to give the desired pressure differential over MAP. This saves a lot of power owing to the fact that at light load the pump's duty cycle can be reduced. It also makes the operation of the pump much quieter.

With regard to fuel injectors intended for racing use, they should be low impedance, fast response models. Injectors originally designed for turbocharged engines have way better low end linearity.

 

[PSlem]

I'd like to get some more info on a pulsewidth modulated electric pump. I've been looking at this, and other sources such as aquamist use a pulsewidth modulated solenoid valve in line to control flow, but it's one more item to buy. I'm still looking at a batch injection system so it makes no sense to use injectors with individual solenoids. Ideally I want a Walpro pump with some kind of flow control to 4 throttle bodies with fixed orifice jets as a retrofit for old Stromberg/Rochester intakes.

 

[imhuge999]

I would suggest looking into injectors that are used in multi-pulsed HCCI applications. I think I know of some companies that make what you are talking about. Let me dig through my piles of stuff and see if I can find some info. I believe AVL makes something like what you are talking about.

Here is an interesting addition that I am asking back. What about injectors that are cam driven (similar to large CAT or Detroit Diesel engines) and use a varable cam system to deliver the fuel you want relative to engine speed. It is possible that you would have incorporated a variable cam for the valves so why not add a few lobes for the injectors. Granted it will put more stress on the cam , lifters, drive gears etc...which would add to the cost...Just some additional thoughts

I started rambling but I still think my idea is an intersting one. Anyhow i'll look for some info.

 

[imhuge999]

I went through some piles stuff and cannot find anything. I suspect it is in my shop and it looks like a bomb went off in there. Anyhow since injectors are pulsewidth modulated simply vary the pulse to get the flow you are after. You don't have to have a fancy injector for that.

 

[PSlem]

I've been searching too, and think I have found the answer in the Parker Hannafin Pneutronics line, a .116" orifice 12V solenoid valve with 2 ms response time and 1/8" NPT ports. That's a large enough orifice to feed a healthy V8 and fast enough to run off injector signals. Add cheap jets and I may have something.

 

[PSlem]

I found an aftermarket RPM controlled voltage regualtor for EFI fuel pumps at

http://216.242.145.16/products/product.phtml?p=31

I also found an article on make your own at

http://www.autospeed.com/cms/A_1522/article.html

and two follow up articles, but schematic is available at small charge. My question is does limiting the voltage cause any loss of motor life?

 

[WGJ]

Just noticed this thread and wanted to add a comment or two.

DC electric motors don't respond too well to being run at voltages much below their design condition.
Battery voltages in cars are often pulled down by electrical load, battery condition and operating conditions. Starting voltages in cold climates can be down to 8V, with idle voltages down to 10 or so at idle with lights, heaters, etc. on. The result is that the motor performance is not linear with voltage changes. Different samples of the same pump will perform in a different way at the same reduced voltage.

I have worked on the development of fuel systems using pulse width control of the electric fuel pump, in closed loop with a fuel pressure sensor plus system calibration control which can either maintain a fuel pressure drop across the injector regardless of engine load, or can vary the pressure depending upon other sensed conditions.

The Walbro pump mentioned will perform well in a system with PWM and pressure sensor feedback. The pump is a positive displacement type (gerotor design) similar to Pierburg pumps I have experienced in high power applications.
Another US Ford which uses PWM fuel pump control is the Lincoln Towncar (not sure if the names right, but it was coded DEW98 by Ford) - the associated 'S' Type Jaguar uses a similar electrical control system.

As already noted - pump noise (always a problem with positive displacement pumps) is better controlled.

Another informative web site ref PWM is

http://www.4qdtec.com/pwm-01.html

 

[hotrodwrx]

I think what you have been hearing about dual stage fuel injectors is what folks have seen with the larger PE injectors on the subaru WRX. Some of the tuners were trying to make sense of the way the fuel tables had to be setup.

My understanding is that these injectors have a relatively slow opening rate. As a result at very low duty cycles they act like smaller injectors than they really are because then never have time to fully open and get to max flow rate. As the duty cycle gets higher they suddenly seem to flow more fuel as the finally are getting enough pulse width to completely open.

It makes tuning at the low rpm of the fuel map somewhat complicated because you have to anticipate where this threshold of full flow will be the dominate mode of operation. Folks would add x percent to the fuel at low rpms and get x + y fuel and they couldn't figure out why. I think the original "dual stage hypothesis" has entered the early stages of an urban legend.

Larry

 

[dgallup]

Highly turbocharged engines like the WRX and high RPM engines like F1 or sport bikes do need high dynamic range injectors. The "dual stage PE injectors" sound like a bandaid attempt to get a high dynamic range from a slow responding pintle injector. ContactRuss Collins at RC Engineering and get some fast acting plate valve injectors. They will opperate at significantly shorter duration of injection than pintle injectors. The moving mass is less than 0.5 grams compared to 4 gram pintles. They have been used as OE injectors by BMW, Jag, SAAB, PSA, etc. Russ has them available in many different flows, coil resistances and fuel rail fittings.

A lot of aftermarket systems also jack up the fuel pressure to extend the high end fuel flow rate.

 

[ChristopherTurner]

You may want to check our

http://www.sturmanindustries.com

 

[turbocohen]

Turn down ratios of 15:1 (20ms period) are good for low impedance and 10:1 for saturated switch. An optimized solenoid injector with 23:1 was demonstrated by a now retired engineer. It was intended for oem's that who wanted to stay closed loop on decel at higher rpms where decel cutoff was not desired, ie, keeping excess o2 from storing in the cat. It was built from a very fast opening low lift version of a CNG injector with an adge orifice. Search uspto.gov and you will find it.

It had dual coils and a molded in circuit, one coil a low impedance one optimized for opening speed and the other counter wound coil supplied a high impedance hold. Part of the strategy was to reduce the decay time to reduce the delayed start of armature close flight time. It would open under .4ms and close at about .5 or less. Another issue is opening and closing bounce that the cng design minimised by using low valve mass and lots of spring load aside from other sophisticated yet simple design features. It was proposed for a low smog application but would have been great for racing apps due to the high 300+lb/hr flow capability at 6000rpm.

For more dynamic forget solenoids and actuate the valve with terfenol and the turndown ratio will exceed 100:1