12P Displacement/Inj Flow rate

American Delco GM ECUs and PCMs, ALDL, OBD 1.5.
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12P Displacement/Inj Flow rate

Postby Mark_ZZ3 » Sun Jul 22, 2018 2:15 pm

I'm stumped with an easy question. Can someone help me understand and calculate the value for Displacement/Inj Flow rate?

I've tried to convert from what I know as Lb/hr at a known fuel pressure. In the end, I watch the Wideband at idle and try to adjust the number up or down to get the idle where it wants. It's been marginally successful. It doesn't seem to change the way I thought it would.

Let's use 30lb/hr injectors as a test case.

How do I convert from Lb/hr to Litres/Grams per second? 30 lb/hr works out to 315 cc/min. That is .315 Litres/min and then 0.00525 Litres/second. Correct?

Then you multiple by the number of injectors in your setup? So if this was a V8, then 0.042?

Sorry if this a beginner question. I never understood the value.


My setup seems to run in the 0.07 - 0.08 grams per second ... but I'm still tuning. I have other injectors to use, as well as I want to swap in a high pressure pump.

Mark.

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Re: 12P Displacement/Inj Flow rate

Postby Mark_ZZ3 » Sun Jul 22, 2018 2:30 pm

I've used the KinjFlow spreadsheet and tried out a few combinations. Does this assume there is one injector per cylinder? I'm running a modified TBI setup so only two injectors on a 4 cylinder engine. Does that change the value?

Mark.

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Re: 12P Displacement/Inj Flow rate

Postby immortality » Sun Jul 22, 2018 4:06 pm

Yes, I do believe it works on a injector per cylinder basis. Change to 2 cylinders and see what that does.

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Re: 12P Displacement/Inj Flow rate

Postby Charlescrown » Sun Jul 22, 2018 4:07 pm

My first question is the car running? If so you can go off the wideband and increase or decrease the flow rate so it runs OK then start tuning. If you run out of VE increase the flowrate and drop your VE numbers. I have a Starion 2l with TBI 2 injectors of unknown value so I took a guess and the changed my injector flow rate to get it running good at idle/low rpm then started tuning.

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Re: 12P Displacement/Inj Flow rate

Postby Mark_ZZ3 » Sun Jul 22, 2018 4:18 pm

Charlescrown wrote:My first question is the car running? If so you can go off the wideband and increase or decrease the flow rate so it runs OK then start tuning. If you run out of VE increase the flowrate and drop your VE numbers. I have a Starion 2l with TBI 2 injectors of unknown value so I took a guess and the changed my injector flow rate to get it running good at idle/low rpm then started tuning.


Yes it runs. I got it to idle well enough with the wide band. Runs lean once you get into the boost. Also when you start to get into the throttle it goes lean before it goes rich. I was looking for a setting like an accelerator pump shot to get over the hesitation.

Interesting idea to increase flow rate and lower VE to allow more room up to so to speak. Never thought about it like that.

Mark.

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Re: 12P Displacement/Inj Flow rate

Postby Charlescrown » Sun Jul 22, 2018 5:31 pm

Great. My method of tuning is simple and I hope it's right. Take reading at a couple of hundred revs apart up to say 4 grand with steady throttle and adjust the VE figures to get it close then drive the car and hold it on 0 vacuum as the speed increases and that will give you some idea what to adjust. It's not till you get that right that you go into boost danger zone.

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Re: 12P Displacement/Inj Flow rate

Postby Mark_ZZ3 » Mon Jul 23, 2018 12:20 pm

Well did some testing. Seems to run better ... albeit richer.

One issue is that we are using a wideband O2 and outputing the narrowband from the gauge. The output seems too digital and does not have the swing of the normal narrow band. The computer jumps in and out of close loop and always thinks it's too rich (BLM's are in the 100's). We did a test with the O2 disconnected and it seems to be more consistent. We will have to install the narrow band back in and run the wide band in a different spot. See if that is more consistent. :-/

Mark.

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Re: 12P Displacement/Inj Flow rate

Postby immortality » Mon Jul 23, 2018 3:26 pm

That seems to be a common problem with the simulated narrow band O2 output from a WB. Your best bet is to use the factory O2 sensor and weld in anohter bung for the WB.

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Re: 12P Displacement/Inj Flow rate

Postby vlad01 » Mon Jul 23, 2018 4:04 pm

What WB are you using? simulated NB depends on the controller, the 14point7 ones are excellent while the innovate ones are junk. I use the 14point7 controller and NB is perfect on it, can't even tell it's simulated and the ECU is happy as a pig in shit with the cross counts at a nice consistent and fast rate.
I'm the director of VSH (Vlad's Spec Holden), because HSV were doing it ass about.

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Re: 12P Displacement/Inj Flow rate

Postby immortality » Mon Jul 23, 2018 4:09 pm

That sounds about right, I do believe the ones i've heard about have been the innovative ones.

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