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!

[914Sixer]

Stock set to run 28-30. In vapor lock areas up to 32. Know nothing about micosquirt pressures.

[JeffBowlsby]

43.5 PSI is the conversion from 300kPA which is the test pressure for standard 914 injectors, not the service pressure.

You sure your injectors are rated that high for in service conditions?

[GregAmy]

You sure your injectors are rated that high for in service conditions?

https://www.fiveomotorsport.com/a280-a380-h...-fuel-injector/

I could adjust the tables to accomodate it (just fired it up yesterday) but if I can easily get it to the rated pressure I'd know what to put in TunerStudio as my proper injector setting.

I'm trying to learn more about if I'm losing injector efficiency by running longer dwell times on the lower pressure.

[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?

[Bleyseng]

The Ljet has a variable fuel pressure regulator to can go up to 40psi IIRC. I don't see how vapor lock would occur using a Djet regulator if you run higher psi.

[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.

[nordfisch]

- You Posted: Injector Table

Hi Jeff,
the table you posted isn't correct.

There are three different flow rates at D-Jetronic injectors:

yellow: 265 ccm/min

green: 318 ccm/min

blue: 380 ccm/min

(All types very early without color code, black plastic, very rare, to be identified by parts# only)

The D-Jet 914 (and other Volkswagen D-Jet) were equipped with yellow (1.7l) and green (2.0l) only.

Blue injectors were used on other car brands only.

You can use the page of Stan Weiss Injector Flow Table for a reference, you find also a calculator for re-calculating the flow rate at different pressure there.

I will send you the historic Bosch table in German language.

Regards
Norbert

[JeffBowlsby]

Hi Norbert, thank you for the Bosch list its very helpful. I can see that that my chart above needs updating, I did not have that Bosch list available back then. I had used other web sources listed in the references, many were injector rebuilder shops.

I developed my chart maybe 15 years(?) ago, based on the references available at the time, which are indicated on the chart. It took quit a bit of time as I recall. Looking those up now, I see many of those sites have gone away. A couple are interesting though. The Weiss chart was a reference for me back then, but it currently lists the 0 280 150 019 injector at 320.6 cc/min, and the Witchunter chart lists it as 406 cc/min at 3 BAR. I wonder why they changed it?

One would think rebuilders would use accurate info.

I did not see an indication of what the test pressure was for the Bosch chart values. Do you know?

[ChrisFoley]

no problem running these at 36psi and putting in "255" as the flow rate

Why even go up to 36? Calculate the flow at 30psi and use that number. Seems a whole lot easier than trying to run at higher pressures. A proper functioning injector should have an adequate spray pattern even at 30psi.

[GregAmy]

Why even go up to 36? Calculate the flow at 30psi and use that number. Seems a whole lot easier than trying to run at higher pressures. A proper functioning injector should have an adequate spray pattern even at 30psi.

:shrug: Fair point. I don't have a preference. Just trying to figure out what will work best.

But the lower the pressure, the lower the flow. And with lower flow, the more time in the combustion cycle (duty cycle) the injector will have to spray to provide sufficient fuel.

The length of time doesn't bother me much, because I was (and still am) perfectly fine using the old CIS system in my Rabbits, which sprayed fuel into the back of the intake valve 100% of the time...plus, this thing is batch injection anyway, so it's already doing double duty.

So..."just trying to figure out what will work best" within the range of equipment I have.

[nordfisch]

... The Weiss chart was a reference for me back then, but it currently lists the 0 280 150 019 injector at 320.6 cc/min, and the Witchunter chart lists it as 406 cc/min at 3 BAR. I wonder why they changed it?

One would think rebuilders would use accurate info.

I did not see an indication of what the test pressure was for the Bosch chart values. Do you know?

Hi Jeff,
I don't know the reason why some guys publish strange data...
maybe they measured 'blue' injectors instead of 'green' ones.
Late 0 280 150 036 injectors (type 'blue') do have a real strange color and look more light green than blue.y
406 cc/min would fit a blue injector at 3 Bar... or using another fluid or both.

This is only a suggestion.
But I can definitely say incorrect values are published in Germany, too.

Be aware Bosch produced only three types of D-Jetronic-injectors (265 ccm, 318 ccm, 380 ccm) (another type with higher flow rate was developed, but never produced).

The D-Jetronic-injectors are numbered from 0280150001 to 0280150045. All injectors outside of this range are no D-Jetronic-injectors.

So are the injectors of the 1.8 L-Jetronic not compatible with the D-Jetronic.

Sorry, I can't tell you which medium Bosch used to test the injectors now.
I'll try to get the information.

'ASNU' - rebuilders normally don't measure the flow rate but check the spray pattern and the difference between the injectors of the same type they test together only. Bosch testing procedure for injectors doesn't include flow rate measuring, too.

Regards
Norbert

[JamesM]

Higher pressure provides better fuel atomization, one reason newer cars dont run at 29psi.


Not understanding what the concern with running higher pressure/having a "safety" margin is about. Those are completely custom injections so nothing d-jet applies here (except for maybe the pump and pressure regulator if you retain those). Injector flow rates can potentially get sketchy when run above 80% duty cycle, that is where I would have concern with a safety margin and running lower pressure means higher duty cycle needed to deliver the same amount of fuel, so in that respect you are potentially safer running the HIGHER pressure depending on your fuel needs.

If there are concerns about the injectors though I would say contact FiveOMotorsports about them.

I would run them at the pressure with the known flow rating.

As for the stock pressure regulator, not sure what its maximum pressure spec is but I have seen a d-jet car sitting at ~50psi at the rail before (DAPO, dont ask), so not sure if that is something attainable with most stock regulators and pumps but i have seen it.

[JeffBowlsby]

The concern about constant operation at maximum pressure is that you would not want to use any critical part that was to be dependably reliable at its peak output, for very long. Unless you are racing and that's an extreme condition. I had understood this topic was an about everyday application which assumes reliability over extreme conditions - i.e a safety factor.

it would not be reasonable to run 100 PSI pressure rated fuel hose routinely at 100 PSI. Motor oil rated for 300F @ 300F. Your engine constantly at redline. Etc.

Why the heartburn?

[914_teener]

Higher pressure provides better fuel atomization, one reason newer cars dont run at 29psi.


Not understanding what the concern with running higher pressure/having a "safety" margin is about. Those are completely custom injections so nothing d-jet applies here (except for maybe the pump and pressure regulator if you retain those). Injector flow rates can potentially get sketchy when run above 80% duty cycle, that is where I would have concern with a safety margin and running lower pressure means higher duty cycle needed to deliver the same amount of fuel, so in that respect you are potentially safer running the HIGHER pressure depending on your fuel needs.

If there are concerns about the injectors though I would say contact FiveOMotorsports about them.

I would run them at the pressure with the known flow rating.

As for the stock pressure regulator, not sure what its maximum pressure spec is but I have seen a d-jet car sitting at ~50psi at the rail before (DAPO, dont ask), so not sure if that is something attainable with most stock regulators and pumps but i have seen it.

I think that is what Foley is saying. The OP didn't say if he was going to retain the stock pump and I'd assumed he was going to use the linked high impedance injector which is rated at 280 cc/ min at 300Kpa. The OP didn't mention displacement.


I know some folds have done MS systems so maybe they'd chime in.

[JamesM]

I know some folds have done MS systems so maybe they'd chime in.

I have done quite a few of them (IMG:style_emoticons/default/piratenanner.gif)

[JamesM]

The concern about constant operation at maximum pressure is that you would not want to use any critical part that was to be dependably reliable at its peak output, for very long. Unless you are racing and that's an extreme condition. I had understood this topic was an about everyday application which assumes reliability over extreme conditions - i.e a safety factor.

it would not be reasonable to run 100 PSI pressure rated fuel hose routinely at 100 PSI. Motor oil rated for 300F @ 300F. Your engine constantly at redline. Etc.

Why the heartburn?

Which leaves the question, what is the peak output of these parts?

Fuel Hose - I would hope anyone swapping out their injection has installed at least 30r9, all of which I have seen has at least a 100psi working pressure (newer gates hose is rated 225PSI working pressure) with a burst pressure usually 5-10 times that, so 43psi shouldn't be a concern.

Fuel pump - Stock pump may be an unknown, especially with age, however if we are swapping parts its just a matter of right sizing the pump.

Pressure regulator - I wouldn't anticipate this being an issue provided the pump is sized properly, but even it it was its a simple swap.

So that pretty much just leaves the injectors, the actual limits of which are currently unknown. But... given injectors are flow rated at 43 psi I wouldnt have concerns about any immediate failure. As to long term use, without actual data (IMG:style_emoticons/default/confused24.gif) (IMG:style_emoticons/default/confused24.gif) (IMG:style_emoticons/default/confused24.gif)
but, i think it should be pointed out these are not 50 year old injectors and modern injectors/cars run at higher pressures, heck even later vanagons push close to 40 psi if i recall.
Something else to consider is that if you take an injector designed to run at 43psi and then run it at a lower pressure you potentially run into issues as well, generally more issue than you would have vs increasing pressure as you have the possibility of inconsistent spray pattern and atomization issues. But without the data, who is to say?

Personal opinion, I think ~43 is the safest place to start (if possible) with the injectors, and having seen the difference in atomization between 2 bar and 3 bar pressures first hand, if proven to be reliable either via long term testing or additional data from FiveO, I see no reason to go lower.

When working with something like megasquirt a lot of the time you are in undiscovered country, if you are not comfortable testing things yourself then it might not be for you. Thankfully now there is a LOT more information on available than there was 15 years ago as a few of us have been out there trailblazing and testing this stuff out.