Are these injectors good?

TYTILIDIE

TYTILIDIE

METH HEAD
Re: Are these injectors good?

It's just a six said:
Are you running out of injector?
Click to expand...

14.5psi we are at 102%dc. Seems a little much. Fuel pressure may not be rising as much as it needs to but I have not yet confirmed that. In fact, we are having pretty bad cold start issues so with that in mind we went ahead and ordered a new Walbro for the truck. So, once I get the new pump in, I will do some more logging and find out for sure.
 
It's just a six

It's just a six

Super Member
Re: Are these injectors good?

Did it have a stock pump?
If so,,that is most likely the problem.

I know when I was running about 16-18 psi range w/the stock pump,it was running too lean.

Installed a new 255 HP Walbro,& that took care of it.

Was able to run low to mid 12's w/ATR street chip & was still pretty rich, even up to 20 PSI.


From what info I have gathered,it seems just by going by the D.C. on the injectors is not all that reliable,even guys w/there Buick GN's will see 110-120 % duty cycle or a lot more than 100%,how can that happen?

Can an injector flow more than 100% D.C. ? I'm no expert.
 
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TYTILIDIE

TYTILIDIE

METH HEAD
Re: Are these injectors good?

It should have a Walbro as it has the racetronix harness with hobbs switch. I would like to ditch the hobbs switch though. Sometimes during the cold start routine (and I mean cold temps outside) the pump doesn't want to stop priming.
 
turbodig

turbodig

Active member
Re: Are these injectors good?

Don't waste your time... put the 60s in and save yourself the headache.
 
The_Bronze

The_Bronze

Donating Member
Re: Are these injectors good?

It's just a six said:
Can an injector flow more than 100% D.C. ? I'm no expert.
Click to expand...

Duty Cycle is a function of the amount of injector on-time in regards to the actual amount of time available to spray fuel. (Two complete engine revolutions).

DC = Injector Pulsewidth/Cycle Time.

Cycle Time =120,000/rpm or more cleanly: Inj PW x RPM / 120,000 = Cycle Time

At 4800 rpm, there is only about 25ms time between when the intake opens, closes and when the intake opens again. If the PCM is commanding 28ms, then it would be reading over 110% duty cycle, but would only have enough time to spray 25ms before the intake valve would be opening for the next intake stroke. The 3ms just don't happen and forces the injector to run all the time (while at 100%+ DC), which isn't healthy for the PCM drivers.
 
dgoodhue

dgoodhue

BuSTeD 4.3
Re: Are these injectors good?

The_Bronze said:
Duty Cycle is a function of the amount of injector on-time in regards to the actual amount of time available to spray fuel. (Two complete engine revolutions).

DC = Injector Pulsewidth/Cycle Time.

Cycle Time =120,000/rpm or more cleanly: Inj PW x RPM / 120,000 = Cycle Time

At 4800 rpm, there is only about 25ms time between when the intake opens, closes and when the intake opens again. If the PCM is commanding 28ms, then it would be reading over 110% duty cycle, but would only have enough time to spray 25ms before the intake valve would be opening for the next intake stroke. The 3ms just don't happen and forces the injector to run all the time (while at 100%+ DC), which isn't healthy for the PCM drivers.
Click to expand...

What he said. Also as you approach 100%, the injector will constantly be on as well. The number will vary by injector but a 95% DC might very well be on 100% of the time as well.
 
turbodig

turbodig

Active member
Re: Are these injectors good?

It's just a six said:
From what info I have gathered,it seems just by going by the D.C. on the injectors is not all that reliable,even guys w/there Buick GN's will see 110-120 % duty cycle or a lot more than 100%,how can that happen?

Can an injector flow more than 100% D.C. ? I'm no expert.
Click to expand...

It can't.

What usually happens is that the scan tool in question calculates %DC based on parameters that it knows about. It often gets the DC calculation wrong.

DM is a good example of this - I've had cases where I was at 102% duty cycle, kept increasing fuel, and the wide-band kept getting richer. If the injectors were really static, this wouldn't happen.
 
It's just a six

It's just a six

Super Member
Re: Are these injectors good?

turbodig said:
It can't.

What usually happens is that the scan tool in question calculates %DC based on parameters that it knows about. It often gets the DC calculation wrong.

DM is a good example of this - I've had cases where I was at 102% duty cycle, kept increasing fuel, and the wide-band kept getting richer. If the injectors were really static, this wouldn't happen.
Click to expand...

That's sorta what I was thinking.:tup:
 
The_Bronze

The_Bronze

Donating Member
Re: Are these injectors good?

Sure, add theoretical to my post. My DSM Scanner did that as well. Scan data should always be questioned as they can give false data and/or relay data packets at the wrong time, making data look invalid. I am looking forward to getting more experience with DM.
 
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