Hello all,

I seem to be about to run into the limit of my fuel injectors it seems like. I was hoping to get some opinions on what they should be upgraded to as I am no expert for fuel injector sizing based on the parts I have shy of taking an educated guess that will be hopefully close. I would rather get it right now.

Below is a list of everything done to the car at the moment. I would love to go boosted one day, but I am unsure when that will be as I do want to just drive the car and enjoy it for a bit.

Parts List:
1989 Auto
AFR 195 cc street heads with 65cc Chambers
Comp cams CL08-503-8 cam/lifters kit
Comp Cams Ultra gold 1.6 roller rockers
Cloye's true roller timing chain set
Mini Ram intake 1205 port
Racetronix fuel pump upgrade kit with standalone harness

I am currently in the works of installing an EBL Flash II ECM and would prefer to change the injectors before any major changes are made to the tuning which may set me back a little bit.

Currently, I have 22lb Bosch 3 injectors that are about 8 years old and to keep my BLM's at a normal rate, I am running my AFPR at about 75psi. This is not the running pressure, but just the key on pressure.

Let me know your thoughts or if you have any tips! I should have the EBL ECM up and running today so that I can start some VE Learns, but again I don't want to do anything too crazy if I need to change injectors. If these injectors are doing fine as well and y'all don't think I need new ones then I will take that advice too!

 

Recommend calling Southbay Fuel Injectors. They'll get you set up with the right ones for your needs.

But I'd probably get something 25 lb/hr at least for your setup.

 

Hello,

Re-visiting this as life and other stuff got in the way and I never got around to purchasing newer injectors.

Just putting a feeler out there to see if anyone else had any opinions on the matter, or if I should just make some calls to some of the companies to see what they recommend.

 

If you're in socal near me I have several sets from 36/42/60 lb injectors all with low miles on them. (I'd sell them cheap) If you're hitting 70+ lbs fuel pressure those injectors you have now are really out from the latency tables.

 

I am in the bay area sadly, wish I had posted this earlier as I was in socal last month for a few days....

I am definitely at the far end of the range for some stock pressure injectors and have been having a slight stumble every now and then under high loads and I think this is the issue. Plus my injectors are from roughly 2012-2014, so I am sure that doesn't help much.

Just trying to figure out an appropriate pressure rating/flow rate to maximize for my setup.

 

I have a very similar setup on my 85 Corvette, only difference is I am running a 280XFI cam. With 36lb/hr injectors at 43psi I am around 85% duty cycle at 6200rpm. I originally bought a set of 30lb/hr injectors and many told me that would not be enough. Doing the math 36lb/hr injectors should be well under 80% dc but AFR is right where it should be and my fuel pressure is rock solid at 43psi up to redline. I've considered increasing fuel pressure but since the injectors are rated at 43.5psi and I am still below 90%dc I've left it alone.

Are you currently running EBL Flash II?

 

I am currently on an EBL Flash II

 

Latency is the time it takes for the injector to be open from the time it was commanded. How is fuel pressure, or any fuel pressure level, related to that?

 

If you increase fuel pressure significantly it changes the flow rating of the injectors and also effects the latency. My last 60lb injectors (FIC) were hitting 95% duty cycle, so I went from 43.5 psi to 58psi and had FIC (fuel injector clinic) recalc them-it was a significant difference. I've since gone to 100lb injectors since I'm hitting higher boost.

 

I agree that the amount of fuel dispensed by the injector with vary with fuel pressure. My injectors are rated at 1500cc / 142lb at 58psi and 1300cc / 125lb at 43.5psi. But that is not what I was asking about.

Latency is time, not flow.

 

For injector sizing you need to consider a few things. First off don't use what someone else had success with as a guide. It's a great data point. But shouldn't be the deciding factor. The first thing to look at is a injector size calculator. I like this one.

https://deatschwerks.com/pages/fuel-injector-calculator

The next thing to consider is the fuel pump. If you increase pressure the injectors will flow more but your pump will flow less. So you also want to look at a fuel pump calculator and verify that it can handle what you want to do. I also use a calculator for this

https://deatschwerks.com/pages/fuel-pump-calculator

Last is the fuel lines. Once you get to a certain LPM volume the factory lines just can't flow enough. So once you find a pump and injector set you're happy with double check that the line size is large enough. Because I'm running flex fuel I needed a Walbro 450 with 76 pound injectors at 60 psi. I'm using 8an feed and 6an return lines. Later this summer I'm upgrading to 100 pound injectors and lowering my pressure to 43.5 psi.

A budget friendly option for injectors that a lot of people overlook is flex fuel injectors from a salvage yard. Most all GM flex injectors are around 35 to 40 pounds. There is a lot of available injector data for these online. They have a much better spray pattern than the older style large body injectors. You will need injector "hats" and wiring adapters to use them. But those are really inexpensive on Amazon. I would pull two sets of injectors with matching part numbers at a wreaking yard and send them off to be rebuilt and flow matched. You'll end up with a really nice set of flow matched injectors that will give you way more volume and still idle well.

 

And according to FIC per the values they provided me with for the same injectors from 43.5psi to 58psi, higher pressure/flow the latency/time is different also.

 

Interesting. Could you post that please?

 

https://www.thirdgen.org/forums/diy-...0-voltage.html

 

What needs to be done to my battery to get the Bosch D3 to run right, the link posted shows conflicting info which one is it?

Low Slope 23.76
High Slope 19.26
Breakpoint 0.00001

VOLTAGE OFFSET

voltage ms
16.00 0.78
15.00 0.78
14.00 0.78
13.00 0.936
12.00 1.093
11.00 1.25
10.00 1.47




6.4 V: 3.07851247
8.0 V: 1.85340073
9.6 V: 1.30766195
11.2 V: 0.99121428
12.8 V: 0.76537403
14.4 V: 0.60906068
15.0 V: 0.55248610*

Can round as required and extrapolate from the 14.4 V and 15 V for the 16 V entry.

Minimum PW is: 0.853 mSec




VDC = uS
1.6 = 2714.47
3.2 = 2464.86
4.8 = 2215.25
6.4 = 1965.64
8.0 = 1716.03
9.6 = 1466.42
12.8 = 967.2
14.4 = 717.6
16.0 = 467.99
17.6 = 218.38
19.2 = -31.23

 

Apologies for the delay. Here is data for you at 43.5 psi. If you need a Small Pulse Width adder table, please let me know and provide me with a screen shot of the table so I can match the axis values.



Volts

µsec



Inj Flow Rate

0

8117.59



cc/min

730

1.6

6381.62



lbm/hr

71.1

3.2

4893.99



Min PW

4.8

3654.70



µsec

325

6.4

2663.75



msec

0.325

8

1921.14







9.6

1426.86







11.2

1180.93







12.8

916.86







14.4

757.72







16

655.14







17.6

655.14







19.2

655.14







20.8

655.14







22.4

655.14







24

655.14







25.5

655.14







Here is data for 58 psi. You can reuse the same small pulse width table as the values do not change from 43.5 psi to 58 psi.



Volts

µsec

Inj Flow Rate

0

8.833

cc/min

825

1.6

6.944

lbm/hr

80.58

3.2

5.325

Min PW

4.8

3.977

µsec

325

6.4

2.898

msec

0.325

8

2.090

9.6

1.553

11.2

1.232

12.8

0.998

14.4

0.824

16

0.713

17.6

0.713

19.2

0.713

20.8

0.713

22.4

0.713

24

0.713

25.6

0.713

I copy and pasted this from their email, sorry the format didn't come thru. Also in one is microsecond and one in millisecond-just note the decimal location, but you can see by this they state there is a difference.