D-Jet Fuel Pressure Regulator, How high should it go? Options

[GregAmy]

What should be the maximum capability of the stock D-Jet pressure regulator? Mine only goes to 36.

If that's normal, is there another similar-format regulator that can go up to around 45psi?

Background: Microsquirt project. Was hoping to use the stock regulator, but now need something that I can easily mount in the same location, if possible. Injectors I'm using are rated at 43.5psi.

Discuss!

[JeffBowlsby]

As I thought...thats maximum flow, without a safety factor.

[GregAmy]

As I thought...thats maximum flow, without a safety factor.

So then...where should it be run? Higher pressures reduce duty cycle and vice versa. It'll never run more than 85% duty cycle regardless or I'll swap to higher-flow injectors (which is highly unlikely, given the dead-stock engine's original awesome <90 horsepower and 5800 RPM redline...these should be easily sufficient.)

BTW, I don't see the word "maximum" in there anywhere...all I see is a flow rate at a specified pressure, which as you note you note is standard practice.

Are you recommending not running it at 43.5psi? If not, then where?

[914_teener]

As I thought...thats maximum flow, without a safety factor.

So then...where should it be run? Higher pressures reduce duty cycle and vice versa. It'll never run more than 85% duty cycle regardless or I'll swap to higher-flow injectors (which is highly unlikely, given the dead-stock engine's original awesome <90 horsepower and 5800 RPM redline...these should be easily sufficient.)

BTW, I don't see the word "maximum" in there anywhere...all I see is a flow rate at a specified pressure, which as you note you note is standard practice.

Are you recommending not running it at 43.5psi? If not, then where?

I'm confused. Flow and pressure are related however from Jeff's chart for the low impedance injectors yields 380 cc per minute @ the stock aprox. 2 Bar.

The link you provided for the high impedence injector flows 280 @ aprox 3 bar?

A longer duration would increase the flow rate but isn't this deduced by displacement?

I love to learn.

[GregAmy]

I'm confused. Flow and pressure are related however from Jeff's chart for the low impedance injectors yields 380 cc per minute @ the stock aprox. 2 Bar.

With much respect, Jeff's chart is not relevant to this discussion. I am not using 914 D-Jet injectors.

EDIT: Although, is Jeff trying to point out is that D-Jet injectors are all rated at 300kPA but are not actually used at that pressure...?

The link you provided for the high impedence injector flows 280 @ aprox 3 bar?

Correct, thus the point of my query. I'm looking for a factory fuel pressure regulator that will allow me to run 43.5psi. "Factory" because it would be an easy install; "43.5psi" because I want to start with a known 280cc flow rate capabilty in the tuning software (it's one of the required inputs).

I love to learn.

As do I, thus my self-flaggelation instead of staying with a perfectly-functioning D-Jet system (really, it was working fine...even had a newly-rebuilt unable MPS...)

The relationship between pressure and flow is not linear: https://help.summitracing.com/app/answers/d...or-flow-rate%3F

Using that formula, my 280cc (rated) injectors are 26.67 lbs-hr. Using that formula, at 36psi it would be 26.26 lbs/hr or 254.75 (we'll call it 255 for short). That is confirmed by this calculator:

https://deatschwerks.com/fuel-calculators/f...sure-calculator

That said...Jeff is implying that running injectors at their standard rating is not good, that there needs to be a "safety" margin. If I infer that correctly, then there actually may be no problem running these at 36psi and putting in "255" as the flow rate (the Microsquirt has no input of fuel pressure).

I'm just curious if running them at higher pressures is not advantageous in terms of spray pattern and efficiency. Most electronic fuel injector manufacturers are suggesting pressure of 40-80 psi. But for a 100hp (max) crank horsepower 4-cyl engine, 280cc injectors (@43.5psi) are way more than enough...they'll probably be running way low on duty cycle, so maybe lower starting pressure is better...

Regardless, I can tune it to any usable value. And I suspect 36psi is a usable value. Just looking to understand my options.

[914_teener]

I'm confused. Flow and pressure are related however from Jeff's chart for the low impedance injectors yields 380 cc per minute @ the stock aprox. 2 Bar.

With much respect, Jeff's chart is not relevant to this discussion. I am not using 914 D-Jet injectors.

EDIT: Although, is Jeff trying to point out is that D-Jet injectors are all rated at 300kPA but are not actually used at that pressure...?

The link you provided for the high impedence injector flows 280 @ aprox 3 bar?

Correct, thus the point of my query. I'm looking for a factory fuel pressure regulator that will allow me to run 43.5psi. "Factory" because it would be an easy install; "43.5psi" because I want to start with a known 280cc flow rate capabilty in the tuning software (it's one of the required inputs).

I love to learn.

As do I, thus my self-flaggelation instead of staying with a perfectly-functioning D-Jet system (really, it was working fine...even had a newly-rebuilt unable MPS...)

The relationship between pressure and flow is not linear: https://help.summitracing.com/app/answers/d...or-flow-rate%3F

Using that formula, my 280cc (rated) injectors are 26.67 lbs-hr. Using that formula, at 36psi it would be 26.26 lbs/hr or 254.75 (we'll call it 255 for short). That is confirmed by this calculator:

https://deatschwerks.com/fuel-calculators/f...sure-calculator

That said...Jeff is implying that running injectors at their standard rating is not good, that there needs to be a "safety" margin. If I infer that correctly, then there actually may be no problem running these at 36psi and putting in "255" as the flow rate (the Microsquirt has no input of fuel pressure).

I'm just curious if running them at higher pressures is not advantageous in terms of spray pattern and efficiency. Most electronic fuel injector manufacturers are suggesting pressure of 40-80 psi. But for a 100hp (max) crank horsepower 4-cyl engine, 280cc injectors (@43.5psi) are way more than enough...they'll probably be running way low on duty cycle, so maybe lower starting pressure is better...

Regardless, I can tune it to any usable value. And I suspect 36psi is a usable value. Just looking to understand my options.

Ah...love the comment on self flagellation.....humility is a rare commodity.


Now when I read rated test pressure at 300 Kpa that is the metric equivalent to test the injector correct?

My understanding of how these things are tested is that under a mean pressure this is to test the injector body where the molded plastic housing for the "pintle" meets the metal injector body IIRC. To see if that point leaks or not.

I am ignorant what the ultimate pressure is for these things but it reads like we are saying that the 300Kpa is testing pressure and not running pressure and the rated flow? Does this make sense?

And yes...I'd share your concern about fuel atomization and efficiency. I know enough about fluid dynamics to be dangerous.

Edit: Forgot to add....300Kpa = 43.5113 psi. So I quess without speaking for Jeff....this is what I think he was talking about...referencing the chart on his website.

Flagellate on please.