"Effects of Fuel Pressure on Pintle Type Fuel Injectors.

Fuel velocity through a pintle type fuel injector [type code EV 1] can dramatically affect its ability to atomise fuel. The profile of the pintle used in a fuel injector has a direct relationship to the operating pressure it is designed to operate under. Whilst Bosch produce various fuel injectors that may flow the same amount of fuel at a given specification, the system operating pressure will influence the pintle profile. Correct pressure will result in a well atomised spray, while insufficient pressure will result in a “hosing” effect. Excessive pressure will result in either “hosing” or a spray angle that is too large for the targeted area dependent on the pintle profile.

The consequence of excessive fuel pressure on a pintle type injector may well be that as the pressure is increased the mixture values of the engine may appear to get leaner. This is of course not the case, but the fuel being injected is no longer atomised and is entering the cylinder as a liquid mass. This will typically cause the Hydrocarbon [HC] values to rise due to the raw fuel exiting the cylinder, and the Carbon Monoxide [CO] to drop due to insufficient combustion.

Later design fuel injectors [type code EV 6] use “director plate” multi-orifice technology to better atomise fuel across various operating pressures. These injectors allow more flexibility in relation to operating pressures without compromising spray efficiency or fuel atomisation. "

my emphasis.

Luke recently mentioned he tuned a car recently w the Injector Dynamics injectors which, i think, are based off the new Bosch E14 design and was very impressed w the linearity of delivery.

 

ID uses EV14. EV6 is about 15 years old.

The older pintle style injectors are a main reason why Mazda used a base fuel pressure of 2.5 bar (36psi) on the FC and FD (see the technical data sections of the respective service manuals). The FB and FC used top feed Denso pintle-type injectors that were likely licensed from Bosch just like the rest of Denso's 80s fuel injection system. Interestingly enough, newer Subarus uses 3 bar (43.5psi) on their fuel systems which are return-style like the FD. Depending on the model year they use side feed injectors as well.

The Rx-8 has a returnless fuel system that uses higher base pressure. According to the 2009 service highlights document the Rx-8 has a 12-hole primary injector and a 4-hole secondary injector for the series 2. Series 1 had an additional set of 4-hole injectors called the Primary 2 injectors. Combined with Mazda's revised fuel atomization system the new injectors greatly reduced HC emissions. The base fuel pressure (engine off) on the Rx-8 is listed as between 3.75 and 4.5 bar in the technical data section of the series 1 Rx-8 service manual. This is similar to the fuel pressure of a late model GM with port injection.

 

Someone i know just tuned a 13B with the new Injector Dynamics 2200 cc injectors as pri and sec. And the car runs smoother on idle then his 1000cc bosch pri injectors. And the fuel map was so much easier to tune according to the tuner. As far as i know the 2200cc injectors atomize somewhere between 550cc and 750cc injectors and does this for almost any kind of fuel pressure.

I will be going for these injectors on my Autronic SM4 setup on the bridge port 13b engine i have. As i at the moment have 6x Bosch 1680cc injectors. And is a pain to get it to idle at less then 1500 rpm. And it's a bit tricky to tune vacum while normal driving. Esp on E85.

My 4 rotor PP idles smoother then the 13B BP engine. As the 4 rotor has 550cc pri injectors

And the good thing about the IJD injectors is that they are not that expensive

JT

 

Quite the opposite I would say especially for the 210 & 160 lb sizes.

I can understand their use in the primary spots but the secondaries where you don't need as precise injection at minimal fuel openings they don't. Specifically those running 4 injectors for secondaries you could run 160 lb injectors and a smaller 75 lb primary and still be less cost than 4 210 injectors without the idle issues.

Don't get me wrong they awesome for what they allow you to do in primary positions but there are other options that can get you to the same point at a more reasonable cost.

 

Good topic, one I am VERY familiar with!

Thanks for the quote Howard, good info from Bosch.

Fritts, the ID injectors are a bit pricey in comparison to others, but I believe in you get what you pay for. One thing that people don't think about, especially with the older bosch 1600's, is the very wide spray angle of older pintle injectors. You are in effect spraying a semi-atomized fuel cone that will hit the walls of the runners in the secondaries, and dribble into the engine, ruining the nice homogenized mixture we set out for. The ID2000's are much narrower than older 1600's, while maintaining better atomization, and million times better linearity.

 

You will always have fuel on the intake walls no matter what injector you use. An ID or an old 160 will have the same issue of fuel following the walls into the chamber. How much I can undestand is a different story. We inject so much fuel though the design of the manifold as well as injection angle will have just as much effect on this situation.

When tuning what would you see as the advantage of using the ID injectors in a Secondary position?

 

The spray characteristics of older injectors are a big reason why Mazda used the air bleed (atomization port) and spray diffuser on the stock injectors for the FB through FD.

 

I would agree that in the primary position they would help with atomization but in the secondary position where the injector is used at mid to high load the effect would be reduced. Has anyone noticed a different in engine running with and without the diffusers in the secondary positions?

 

Better spray pattern, more cooling of the air and a better mix of air and fuel. So overall and easier engine to tune would be the sutioation.

Im def looking forward to tuning my 13B-Rew BP engine with those injectors as i will be running E85 as well.

 

Much easier to tune, especially in the transition. With ID, you know that the injectors are matched within +/-1.5% of each other all the way down to 1.5msec, so where ever I decide to bring them in, they are good. You might argue that nobody would transition them in that low, but I bet you'd be hard pressed to find old 1600's that are as close even at 50% duty cycle. Most injector suppliers are only testing the injectors static.. They are linear much higher in the operating range, so you can take them to higher duty cycles without any surprises. Also, being a saturated drive injector, there are no need for a resistors (if running PFC at least), which lowers the voltage at the injectors resulting in even worse linearity.

 

Haven't tuned with them but transition really is not that difficult to tune with 160 lb injectors. I have serious doubts a customer in the end would notice any difference between 160 lb Ford injectors verses the ID's in that position anyway. Now in the primary position I can understand. Though I don't like mixing high and low impedance injectors (Haltech). Also getting all the fuel you need for most cars out of 4 injectors based on the ID injectors size would be great. Had even thought of running primary only injectors in an NA vehicle. My guess would be that the anti detonation characteristics or cooling due better atomization at high load would never be realized (think carbs). Trying to find an SAE paper on it to quantify. Matching is one of those side items thats great to have but we have been getting away without it for a long time. I also run dual egt to verify individual rotors are matched anyway.

 

Tune some ID injectors, and I guarantee you will notice a difference, even in the secondary position.

 

Send me over a set to test.

 

send a cc number and i'm sure he will.

Or i'll send you a set to test but i'll need your cc for testing.

 

There in lies the problem. It would be a very expensive test as I wouldn't plan on mixing injectors primary/secondary.