JETPILOT

iTrader: (51)

Introduction

For the purpose of simplicity we will only deal with injectors that have applications for the 350Z with the VQ35DE.

The stock VQ 35DE comes with injectors from various manufacturers. The injector brands are installed at the factory randomly. What ever the factory had in stock is what your car received. You may notice that your stock injectors are a different color than your friends. Regardless of color or manufacturer they are the same size and performance. They are all high impedance injectors flowing 320CC per min @ the stock 52psi of fuel pressure or 3.5bar.

Injector Impedence

Injectors are classified as high impedance or low impedance depending on their electrical resistance. High impedance injectors have a minimum electrical resistance of 8 ohms or more with a typical resistance of 12 ohms. They are called saturation type injectors and use simply constructed saturated driver circuits. Low impedence injectors are less than 3 ohms the most typical being 2 ohms. Low impedance injectors use peak/hold circuits. Their flow is more precise and the injectors and control circuits are more expensive to manufacture.

Low impedance injectors respond faster to signals from the ECU giving the car better idle characteristics. During high performance use the high impedance saturation control injectors get hot and can fail because of the heat generated by the continuos current. Low impedance injectors use reduced power and run cooler. With low impedance injectors the spring that closes the internal valve shutting off fuel can be stronger resulting in faster closing times and more precise metering. A low impedance peak/hold injector sends a 3 ohm signal to open the injector and then holds the injector open with a 1 ohm signal greatly reducing heat.

Most aftermarket injectors we deal with concerning the VQ35DE are high impedance saturation injectors because of the ease of the direct swap for the OE injectors. The bigger the high impedence injectors you go with generally the worse your idle will be due to the above mentioned nature of the saturation injector having less control at idle. The bigger you go the worse the control.

HKS has several sizes to choose from in low impedance injectors for use with their FCON V-Pro and the Haltech PnP standalone. Low impedance injectors will not work with the UTEC.

Fuel Injector Flow Rating

The industry standard for rating the flow of an injector is 3 bar of pressure or 3 atmospheres which equals 44psi. The APS injectors are flow rated @ 3bar while the other popular injector Deatschwerks are rated @ 3.5 bar because as previously mentioned the Z runs a base fuel pressure of about 52psi or 3.5 bar. A 550 Deatschwerks injector will only flow approx 500 cc per min when being rated at the industry standard of 3 bar. Deatschwerks has since changed their rating method and are now offering injectors rated @ the 3 bar standard. The injectors they sell now are 380, 440, 600, and 850 with custom flow rates available so they can now be directly compared to the flow rates of the RC, APS, PE and HKS injectors. All the new Deatschwerks injectors now come with new Denso cores instead of used cores they received back from customers.

How To Choose Injector Size For Your Application

At 52psi of pressure on a turbocharged motor the injector flow rating should be what you can expect to make in terms of rear wheel horsepower with that injector @ 85% duty cycle. So if the injector is a Deatschwerks 600 rated at 3 bar then you can expect to make 600whp @ 52psi of fuel pressure @ 85% duty cycle. For longevity of the injector 85% of the injector duty cycle should not be exceeded. The exception to this above rule is supercharged applications. Expect to need about 20% more injector for your given whp than a turbocharged application would use. These power levels are based on a constant fuel pressure across the RPM band which may necessitate upgrading to a return type fuel system.

Top Feed Or Side Feed

The VQ35DE uses top feed injectors.

So Which Are The More Popular Injector

As far as ease of use the Deatschwerks are direct drop ins. The RC injectors used to require soldering pigtail connectors into the factory wiring harness, but now come with a patch harness making them plug and play as well. As far as reliability both injectors are good, but there have been more issues concerning the RC injectors than the Deatschwerks. I have never heard of a Deatschwerks injector having issues. I have heard of a few concerning the RC injectors. But RC does stand behind their product and puts an effort forth to make things right. Deatschwerks injectors are a little less expensive than the RC’s. It is very easy to get technical assistance from Deatschwerks by calling their number and talking directly with someone from tech support.

Cleaning and Servicing

Both Deatschwerks and RC offer cleaning and flow bench testing of injectors. Porsche Club of America promotes Chevron Techron concentrate as being a safe and effective fuel injector, valve, and combustion chamber cleaner when used as directed on the label. From tests I have reviewed other in tank injector cleaners proved to do little if anything and are usually a waste of your money.

Fell free to add any info you'd like or correct any mistakes.

JET

westpak

iTrader: (19)

nice write up

RC now has patch harnesses to avoid splicing in the clips

Audible Mayhem

iTrader: (48)

RC has had the clips that clip into the stock plugs and the injectors for a while now to avoid cutting them up.

i still am not a big RC fan. Maybe if they would repay me all the hours of labor i have had to spend pulling them back out of a car, then i wouldnt mind them.

Deatschwerks puts soo much into their injectors to make them perfect every time. i have sold many many sets of Deatschwerks and have had no issues at all. i have tuned over 40 different sets last year and is still my number one injector to have in a car.

Dynosty

iTrader: (27)

For a quick and easy drop-in replacement, the deatschwerks are definitely a nice injector.

For the high power setups, we offer 880, 1000, 1200 and 1680cc injectors. These require high-flow fuel rails, which we stock (link).

Regarding Impedence - the Haltech Platinum PnP standalone is setup to drive both high and low impedence injectors without any trouble. We use it combined with 6 1680cc injectors in our shop car, and it idles rather well

rcdash

iTrader: (18)

Good write up. I believe there is an error though. High impedance injectors use less current, not more (because current and impedance are inversely related) and therefore generate less heat. Low impedance injectors use more power and run hotter. Everything else is spot on though.

EDIT: After discussing with JET, this issue about current draw may or may not tell the whole story. JET provided some data that while low impedance injectors initially use more current (peak), the hold current is less than high impedance injectors so the net power utilized is actually less. I found several references that do not corroborate these conclusions but don't directly contradict it either. Bottom line is low impedance injectors respond more quickly and if the ECU supports it, is a better performing part (to improve idle and throttle response).

EDIT: Hal what brand are those high performance injectors of yours? They are low impedance but less expensive than the RC high impedance I have now (I think they were priced per set, not individually)! Are they individually flow tested like the DW or RC? And will they fit a CJM fuel rail or are your rails specifically needed?

Dynosty

iTrader: (27)

Precision Turbo & Engine - and yes they are individually flowed and sold in matched sets. We have installed many before and never had a problem (and Precision is a great company to work with if there ever is a problem).

Regarding the CJM rails, I checked their site and don't see a clear answer.
The injectors we list are standard domestic injectors, so you may ask them if their rails are compatible with domestic injectors.