bolling

Have had my Z for about a week now and after reading on here about injectors I checked mine out and they are RC 205's. Is this good or bad?

Dynomite

That is great RC 205s are Top of the line Stainless Injectors.

Restoration of the Injectors

As a comparison I have calculated the use of RC SL4 205s.....
I use RC SL4-205 injectors in a 1991 500 horsepower LT5 which RC Injectors are 20 lb rated at a Fuel Pressure of 43.5 psi.
You would use RC 225s for 650 hp or more.



Horsepower = (Fuel Injector Rating)(Duty %)(Quantity of Injectors)/(BSFC)

If we assume Brake Specific Fuel Consumption (BSFC) of .50 lbs of fuel per hour per horsepower......
The Injector Rating required for 500 hp (80% duty cycle and 16 injectors).....
We would get 19.53 lbs/hr for each injector is required for 500 horsepower.

There would be NO correction for Fuel Pressure Differences on the Injector Flow Rate since RCs are tested at the same pressure we are operating with in the LT5 (43.5 psi Fuel Pressure). 20 lbs/hr actual flow rate of RC 205s is greater than the 19.53 lbs/hr required for 500 hp.

Another way of looking at the RC 205s Injector Capabilities.......
For the RC 205s in an LT5......Horsepower = (20)(1.0)(.80)(16)/.50 = 512 hp

bolling

Thanks for the info, mine look like the picture.

Dominic Sorresso

To be accurate, the stock calibration assumes 22.8# injectors. so it would run a bit lean and the fueling tables would need to compensate for that by about 12%. Then there is a the issue of having the correct Injector Offset for the RCs, which the calibration may have.
If you are pleased w how it runs, fine. I'm finicky when it comes to that stuff.

pushrod-v8

Who tunes better? You or Pete?

Dominic Sorresso

Tuning is not a competition. Depends on what the objective is. I focus a great deal of time on idle and part throttle operation. If that's right, then WOT is more accurate. It's not a quick or inexpensive approach.

pushrod-v8

I know...just joking around!

Goldcylon

They are neither.. they are Great!!! Those are top of the line injectors. I have been running them for years. Very expensive with stainless inserts.

bolling

Thanks for the great info.

Dynomite

This from RC.....I have three sets of RC 205s in two 90's and one 91' (The 91' is 500+ hp)

Hello Mr. Dynomite,

A fuel injector’s offset time is the minimum amount of time it takes for an injector valve to move from fully-closed to fully-opened. Generally, most injectors will open fully within 1.0 milliseconds, at 13.5 Volts and 43.5 psi (3 BAR) of fuel pressure. With that said, small flow rate injectors usually open faster than large flow rate injectors because small flowing injectors will have smaller valves, less mass, and less weight. Also, the higher the voltage, the quicker the opening time (smaller offset). Conversely, the higher the fuel pressure, the slower the opening time.

Similar-sized injectors, like the stock LT5 injectors and RC Engineering’s SL4-205 injectors, will have very similar offset times and similar electronic characteristic all together. If you change to a significantly larger injector (20% more or larger), than you’ll need to reprogram your ECU fuel map, including the injector offset tables.



On another subject....I just read that the original LT5 injectors which were rated at 22.5 lbs actually provided around 20.5 lbs.....and further the GM replacements are actually rated at 19 lbs......so there

Dominic Sorresso

As an FYI, here's an illustration of the difference in offset when comparing stock to what I am using at the moment. As you can see, in the typical voltage range of 12.8-13.5 BATT, if you assume a 1ms PW for idle as suggested by RC, that means in my situation I would have a 15-20% error in PW.
Just to be clear, I am using Accel 21# injectors, not RCs. The RCs could have the same offset as the stock injectors, but as someone who spends much time on his own tune, particularly for idle and part throttle driveability, confirming the offset is a critical piece of information.