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!

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

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?

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.

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?

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.

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.

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...?


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).


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.

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

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?

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.

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

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.

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?

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.

I have done quite a few of them

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
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.

I know...

It's a Bosch 2-port replacement. Probably Bosch 69133?


A correct ASSumption.


Dead stock 1974 2L engine, as far as I know. Zero knowledge of its history, though evidence of having been out before. Leaks a little bit at the case bolts.

Whole lotta dick-swinging around here and yet...no one answered the OP's original question.

You can use the stock preasure regulator


Swing your own dick at the rest.

Who is swinging dick? I thought we were just having a discussion.

Not sure there is hard data on the pressure regulators range to give a definitive answer, at least i have never seen it. Like I said though, I have seen one that was cranked out to near 50PSI so I suspect the limiting factor here may be an old pump, but TBH I cant say for sure, may have been a fluke.

I really want to go test this out myself now but my test bed car currently has the fuel rails pulled off. Had to steal some lightly used NOS 2.0 injectors off of it so I could keep my Bumble Bee project totally stock (I have my limits, the LE has to stay stock)


Thats a real clean install you have going so far, I dig it! I like your coil location choice. Working on something similar for my next refresh but using a newer VW 4 coil pack. Great minds....

Click to view attachment

Was poking around a bit and and found these injectors from FiveO which look to just be the low impedance version of their A280H

https://www.fiveomotorsport.com/hose-type-e...-sport-compact/

Interestingly enough, they publish the pressure ranges for this injector on their site (along with the latency info which is a huge bonus for MS)

Notice they list a MINIMUM pressure of 36psi.
Im NOT saying these specs are going to be the same as the A280H (i have no idea), but seeing this would give me doubts about running them at 28-30PSI, at least not without getting confirmation from the manufacture.

Voltage: 8-15 Volts, Nominal 13.5 Volts
Amperage: 4.5 Amps
Latency (dead time): 0.700 ms at 14 volts - Complete latency table sent with each set of injectors.
Excellent atomization for medium compression, single- and multi-valve engines.
Injector Dimensions:
Overall length: 3 in./77 mm
O-ring to o-ring: 2.6 in./66 mm
Body Diameter: .95 in./24 mm

Will not require more than 1% trim
Pressure: Min. 36 PSI (2.5 bar), Max. 101 PSI (7 bar)

Just remembered I still have the paperwork for mine...

No minimum pressure listed, but looks like they should be good for way over 43.
Highly suspecting that they have the same pressure range based on this.

Original recommendation stands... I would find a way to get the rest of your fuel system up to run them at 43psi (realizing that was your original intention here).

Click to view attachment

@GregAmy

What fuel pump are you running?

Literally just now learned this, but it looks like the factory pumps have an over pressure relief system built in (that is apparently what that annoying 3rd port on the 3 port pumps is for) designed to not allow pressure over 3 bar, and guessing on an older pump that number might even be slightly lower due to wear. Just guessing here, but if you are running a stock pump this could explain the max pressure you are seeing.

Per https://oldtimer.tips/index.php/en/d-jetronic/81-fuelpump
It looks like the bosch universal replacement (0 580 464 999)is rated to 4 bar

https://www.amazon.com/MERCEDES-Admiral-Bos...5/dp/B00BHGUKQU

Though amazon is great and showed me this much cheaper ($35) replacement that looks physically identical and rated at 35 gal/hr @ 45 psi Max pressure - 8.5bar (125 psi) - provided you are not afraid of cheap parts.

https://www.amazon.com/Universal-Replacemen...EWG9SKBVNB4MCXX





I personally have been running this pump on one of mine with the stock regulator for 10+ years

https://www.summitracing.com/parts/msd-2225

Its probably a little overkill (good to ~500hp) as well as being on the loud side, but it gets the job done. only mentioning it as i dont have personal experience with either of the other 2 to vouch for them yet.



Im curious to know what you find out here.

Hey, looky what I found....


https://www.injector.com/cart/pc/Adjustable...No-0610-p48.htm

I would deal with/verify your pump situation first but if for some reason you still cant get your stock regulator to 43 psi this looks like it might be a fit providing the picture is an actual representation.

Edit:
Looks to be the same as an MSD 2222 (and if you look real close at the picture it says made in germany and had a bosch part number, not sure what that is about)

https://www.summitracing.com/parts/msd-2222

Also the MSD-2220 (same thing without the boost port)
https://www.summitracing.com/parts/msd-2220

Both are listed as 36-45 PSI


anyways, you have options. Thinking that should be enough info to take care of all the issues

Found another picture of the MSD 2222 where you can see the full bosch part number...

you will never guess what it is...

Since we're going deeper into the design...

And, by the way, before we get too deep into this I wanted to recognize the assistance I've received from EricP, @Montreal914 . He has his own build going on but we've been swapping info back and forth. Thanks, Eric!

My design basis an over-riding "prime directive": use as many stock components as reasonably possible, and try to design it such that anyone can install it. I also have a design cost of <$1500 in parts. Unless someone wants to take this design and sell it as a kit for the community (and if you do, please contact me), I plan to do a full write-up of parts build lists, sources, design, and instructions.

Toward this, my goal is to use the "stock" fuel pump and pressure regulator, if at all possible.

I got the pump I'm using from Chris Foley at Tangerine; it is a 2-port replacement for the factory 3-port. He thinks it's the Bosch 69133. I've yet to find any specs on that pump but I havne't looked hard; I was working under the impression that the limiting factor here was the regulator. Maybe that was a flawed ASSumption.

More later; time to go to work to pay for all this. - GA


EDIT: Current plan is to tune the engine to 35psi, with "255" as the flow number for the injectors.

Many years ago I had a project to design automotive fuel injectors working with then the Bendix company who did the initial patents on the D jet type system before Bosch got into the game.

Solenoid operated injectors take about 1.7 milliseconds to open before any fuel is delivered and an engine operating at 6000 RPM goes one full revolution in 10 milliseconds. the 10 ms is typically the 100% duty cycle for these injectiors.

Looking at the entire flow range of this system or "turn down ratio" you have about 2 to 10 ms flow range for the injector itself plus the trigger points range from idle speed of say 800 RPM to 6000 RPM max yields 8 to one for the injector and 7.5 to one for triggering interval for a total of 60 to 1 flow ratio for the system, that's pretty good.

Modern direct injection engines cannot use anything like 10 ms time as all injection has to occur in the compression cycle. new piezo injectors do not have any initial lag, so are a must for direct injection

As previously mentioned, flow rate is not linear with pressure, but varies with the square root of pressure. So if you've got to larger bore cylinders and want to match with more fuel flow, that can be done by adjusting pressure:
For a 10% larger displacement, in theory you want 10% more fuel flow. to achieve this you need 1.1 squared pressure increase ar 1.21 pressure increase.
So if standard pressure is 28, you'll need 33.9 psi. Hopefully the pressure regulator can be adjusted by this much.

Barefoot

Thank you @JamesM for the find! Exactly what I need for my build as I am taking this opportunity to relocate my fuel pump to the front with a '75 pump panel.

Looking forward reading the results @GregAmy . Still digesting your electrical discoveries...

Totally possible but you may be better off just running d-jet, l-jet, or possibly vanagon injectors, with load resistors at the stock pressures in that case. Pretty much every d-jet component except for the throttle position sensor can be re-used in a Megasquirt build (including the stock wiring harness if you are crafty enough) but having run one like that for ~15 years I can tell you it has its short comings. My first d-jet to MS conversion i think my total parts cost including the MS ECU components (I soldered it myself) was roughly around $150 bucks, but the necessary labor was beyond what i would recommend to anyone.





Not sure about the Bosch 69133 but the factory 2 ports are also supposed to have a built in over-pressure circuit. Hard to say what might be limiting your total pressure but that MSD FPR that is rated 36-42 PSI has the Bosch d-jet part number on it. So I would think that if everything were healthy you should at least be getting close to 40 if not more. I have first hand seen one that was set ~50psi.

That being said if all you can get is 36 you could just leave it there, those injectors may be fine running at that and while it is helpful to know the exact response and flow numbers at a given pressure it isnt mandatory as you build your own fuel map anyways. Given thats the top end of your fuel system output and the bottom end of acceptable pressure on the injectors though I think Jeffs point as to a safety margin may be something to be considered.

Compromises like this are why i have moved more and more away from using a lot of the d-jet bits over the years. I can elaborate on the details a lot more if you like but that only matters if you are interested in changing your goals slightly. I get your current goals, I used to share them, and they are totally doable, just realize they involve compromises and one of those being running as optimally and reliably as it could, though no more so than running a d-jet system. You just wind up inheriting its short comings.

Eric, I'm actually starting to "write all this shit up" like I promised I would; I got into a writing spree yesterday and drafts are going up on my Blogger site now.

I'm looking for some time with a local DynaPack buddy, maybe get it in either this or next Saturday for a general baseline auto-tune and fiddling. Mostly depends on the weather (the 914 does not see the roads until all the salt crap is rained off.)

Anyone know what AFRs these engines like to run at?


Eric and I discussed injectors. Eric took the "go with DJet" direction; I'm interested to see where he ends up. I, on the other hand, compared the cost of cleaning/testing my injectors ($125 incl shipping round-trip), the risk of one failing (a good used one $75-150), and the availability of replacements in the future (low, and getting worse). Coupled to the need for a resistor pack, I chose to replace all four injectors with FiveO's for ~$300 shipped (they offer 15% off coupons all the time).

Same goes for a lot of the other D-Jet components. There's a strong argument for using parts readily available from FLAPS.

All of my design decisions and results will be part of the Blogger writeup.


ASSuming this is a consistent result - in other words, I have nothing "failing" - then I'm planning on tuning the car at 35psi. I can always re-tune to a higher pressure later.

Check this.

"35 gal/hr"

Seems a bit ridiculous for 1 injector, no?

To be clear, I cant vouch for that pump, never ran one, it just popped up in amazon when i was looking at other pumps. It could be complete cheap garbage like a lot of the other knock off crap on amazon these days. But for 35 bucks with a prime guarantee, not a lot of harm in trying.

This one is even cheaper... how low do you want to go?


https://www.amazon.com/Electric-Universal-P...14B2ZEZG3SWM9F7

What is the flow rate on the factory pump?


The pump I have on my car is 43/gal/hr, and yes, it is overkill.

Wait, missed this...D-Jet part? Not the one with the boost port...?

My mistake, apologies. I had mistakenly thought this was an injector...it’s a pump.

Both the one with the boost port and the one without have the same Bosch part number on the body, at least in the pictures I was seeing. Only difference between the two appears to be the adjuster screw. The part number in question though shows it to be a VW/914 d-jet pressure regulator, so if the MSD published specs are believed it leads me to believe that the stock d-jet regular should go to 42PSI, and given I have seen one go higher than that in the past I have to think its accurate. Still has me curious why you are only seeing ~35.

Also, given it looks like the only thing needed to add boost reference to these things is to port the adjustment screw to add pressure to the back of the diaphram, im wondering if its not also possible to affect the max pressure by shimming the adjustment screw??? Ill have to take one apart and examine it a little closer.

- Pump can't go that high (capability or internal bypass);
- Regulator can't actually do it;
- Bad regulator.

I've got some dyno time scheduled for the 14th. I think I'll drop the coin with Summit and buy one. Edit: Items appear to be no longer available.


Yeah, that would have to happen inside; I ran out of threads then I screwed it all the way in.

It's not the pump. I went out there, jumped the FP relay, and used pliers to squeeze off the return line. It hit 90psi before I lost my nerve and released it.

Edit: Looks like these are all similar. No info on max-avaialble pressure, though.

Bosch 0280160001
Delphi FP10545

I have a few FPRs here. You're welcome to try one of mine to see if it gets closer to your desired operating pressure.

Thank you sir!We're already overdue for a beer visit. I may pass by tomorrow if you're in.

Here's some docs I found when I was going through paperwork. The injectors should be OK at higher pressures. Just not clear where I *should* run them. I clearly do not need the flow rate at higher pressure, but I wonder if reducing the duty cycle improved efficiency. I wonder if I'll even notice a difference at all by bothering to go over 35psi.

I would run them at 43 If possible as that is the lowest pressure you have all the datapoints for. Increasing the pressure may improve the atomization but if your pulsewidths get to small mixture control at idle can become a problem.

But... if those injectors can make a decent spray pattern at 35psi I doubt you would notice much if any difference by going to 43, the only question is how well do they fire at 35?

Just catching up on the thread this morning.
Greg, 90 psi on the pump, that is impressive! Regulator...


Thanks James, obviously, I am fully aware that these are what they are . but WOW, $20!!!!
I really wonder if there is actually a quality difference between a $35 and $20 one. Both are low quality for sure. I might just buy two $20 ones...

Quick update... per Summit Racing, MSD has discontinued the MSD-2220.

Rock Auto has the Delphi version, says it's 29psi.

I tried two used ones from Chris; one only got to 34psi, the other had the locking nut stuck so I didn't force it.

NAPA can get me a "FPR for the Porsche 914" but it's special-order only, and they don't know how adjustable it is.

Rock Auto looks like the Delphi version as well, 29psi listed.

I can't find a FPR for the car on Pelican's web site.

I'm guessing that if I'm running more than 35-36 psi I'll have to go aftermarket on the FPR...

Bosch Fuel Pressure Regulator at Pelican

And...they're out of stock. Refers me to "Genuine Porsche" version for $145 which "in some case...must be imported from Porsche's German warehouse -- which requires longer shipping times and an additional "Germany shipping" surcharge."

I'll call my local dealer, see what their tithe is.

You might want to start soaking the three used ones from my shop, and yours for that matter too.