We video a flow test of 4 injectors:
2 hole truck
4 hole truck
Decapped truck injector
eBay 80# cheap injector

 

Neat test! The decapped injectors seem to do pretty well.

 

I'm planning on running decapped injectors in my low boost 4.8 daily. I doubt I'll ever come close to maxing out the 69+ flow of the decapped. Keep in mind as you increase the fuel pressure for every pound of boost the flow would increase. I'd like to do another test increasing the fuel pressure from 58# to 68# then 73#

 

Unless I’m reading that wrong, That’s not correct…


Each psi of boost pressure on the injector tip side drops injector flow. So if you run 50psi base and 10lbs of boost your injector is only flowing 40psi of fuel pressure since it is fighting the pressure in the manifold.


When you install a 1:1 rising rate FPR all it does is negate this effect. It adds 1psi of fuel pressure per pound to keep your injector flowing the same in boost as it does out of boost. Your fuel system/pump then has to account for the added pressure demand required in boost.

 

The wording was odd, it was a presumption people know when you Boost reference the regulator, even the factory setup, it will increase the pressure up to a certain point.
"Keep in mind as you increase the fuel pressure for every pound of boost the flow would increase."
By looking at the base pressure of 58#, I then offered normal boost ranges as options for more testing pressures, to simulate higher Boost levels. We flowed the ebay 80# at 78# fuel pressure they flowed 104#.
The truck decapped injector with the fuel pressure at 78#.... I'm trying to recall the flow rate... hold that thought.

 

Just got the text, we setup the flow fixture with the factory regulator, added 20# boost to the regulator:
The Factory decapped truck injector flowed 78# More than enough to make some decent power.

 

If I'm reading this right you added pressure to your test as is? If so your numbers are not correct. A 1:1 rising rate regulator will not increase flow as boost increases. It will increase pressure at the rail but the differential pressure will remain the same and thus flow will as well.

 

This... It's all about the pressure differential.

 

Ok, to clarify, the original static flow test was your basic GM setup. We used a factory return style fuel rail, 255L pump, and flowed the injectors.
In our supplemental flow test on the same 4 injectors, we added 20# of positive pressure to the port on the factory fuel pressure regulator.
Results: With positive pressure the regulator raised the fuel pressure in turn increased the volume of flow. Stock decapped 69# to 78#

 

When we added 20# of positive pressure to the factory regulator the pressure increased as did the flow. We observed a flow increase from 69# up to 78#.
I wouldn't think a stock decapped injector could handle 20#, we have no data on duty cycle. But for guys running 10-15# of Boost the decapped injector should be a great fit. JD

 

You're not getting the point. To perform a proper test you need to add the pressure into the vessel that your injector is firing into to simulate the boost the motor would be seeing. Your test is adding 20lbs of fuel pressure to a naturally aspirated motor, not one with 20lbs of extra pressure in the intake manifold. Add the 20lbs and your injector flow will not increase.

 

Ok, now this makes sense! You're talking about the potential compression force against the injector correct? With the injector in the intake, how much affect would the boost in the intake change the flow?
You're the first person to mention an opposing force capable of a marked restriction. Interesting concept. JD

 

I talked to Richard, he would like someone to show him anyone who owns a fixture to flow injectors against Boost pressure at the injector.
Not only do they not exist, but you would also have to replicate Boost pressure fluctuations since the intake track doesn't maintain a static boost pressure. Can you show us an example?

 

This isn't a concept it's basic fluid dynamics. You must have differential pressure in order to have flow. If you had 58lbs of fuel pressure at the injector and 58lbs in the intake you would have zero flow. You can increase the flow of the injector by increasing the base pressure as long as you have a strong enough pump. I found an article that can explain it better than I can.

http://injectordynamics.com/articles/fuel-pressure-explained/

Hope this makes more sense, cheers.

 

You don't need to flow it against boost pressure it's very simple math.

 

Interesting information, the point your making consist of a theory not a testing procedure. Long/short. What ever the injector flows statically should stay roughly the same because as the fuel regulator starts to see Boost, any increase in fuel pressure will be counteracted by the same pressure inside the intake. This is very interesting, I do still question the static versus fluctuation in Boost pressure of the intake track during operation. But I finally see what you're saying! Thanks JD

 

Correct as long as you have a boost referenced regulator the injector flow rate will stay the same. Any fluctuation of boost pressure would be corrected by the regulator if it could react quick enough. Cheers.

 

Good shit.....whatever you smoked when you were younger. It musta been good, or bad depends on how you look at it.

 

So he didn't totally understand the science behind it... what's the big deal? He learned something, and he'll pass it on. That's what the forum is about, and we've all been there. What its not about, is a probie coming in and busting his balls.

 

Richard who? Clark?