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froxy cool
Samba Member
Joined: June 19, 2012
Posts: 4
Location: Belgique
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 Posted: Thu Sep 28, 2017 11:18 pm Post subject: 914 raising fuel pressure |
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Hello,
I have replaced injectors into my european 2liter 914 from 1975.
injectors are not NOS bosch but new generation for replacement.
Purchaser say i need to increase fuel pressure to minimum 2.5 bar to have a good working result.
What's the standard pump pressure in a 914?
Regulator will it be able to rise to 2.5/2.7 bar?
Will the start cold injector accept 2.5 bar?
Nominal pressure is 2 bar.
Thanks for your advice |
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raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 21520
Location: Oklahoma City
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| Posted: Fri Sep 29, 2017 7:50 am Post subject: Re: 914 raising fuel pressure |
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| froxy cool wrote: |
Hello,
I have replaced injectors into my european 2liter 914 from 1975.
injectors are not NOS bosch but new generation for replacement.
Purchaser say i need to increase fuel pressure to minimum 2.5 bar to have a good working result.
What's the standard pump pressure in a 914?
Regulator will it be able to rise to 2.5/2.7 bar?
Will the start cold injector accept 2.5 bar?
Nominal pressure is 2 bar.
Thanks for your advice |
Whomever you are speaking to has no idea...."0".....knowledge of what they are talking about.
1. Is this still D-jet injected?
2. The D-jet system uses a FIXED fuel pressure and manipulates baseline fuel disage based on temperature and manipulates the load based enrichment with pulsewidth based on manifold pressure.
Understand this.....EVERY 1 PSI OF FUEL PRESSURE CHANGE EQUAL 3.57% OF FUEL MIXTURE CHANGE ACROSS THE ENTIRE RPM RANGE!
No! DO NOT increase your fuel pressure!
3. The original Bosch injectors had major problems at 35 psi and higher because they are very low impedance "peak and hold" style injectors with low spring pressure. At highway rpms and higher 35 psi and higher causes the injectors to not reseat properly when they close.
Because the new pattern injectors....IF.....they are the correct injectors....should be built the same way with the same resistsnce as the original or the ECU will not have the power output to drive them correctly.
What brand of injector and what part number are you using?
You cannot just put in a newer pattern/type of injector from another system into a D-jet system.
If you need extra enrichment....the proper way is to adjust the MPS. If for some reason you have some variations....you CAN go upwards in pressure to a MAXIMUM of 33 psi....but onoy if you are using an ACCURATE gauge.
Ray |
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froxy cool
Samba Member
Joined: June 19, 2012
Posts: 4
Location: Belgique
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| Posted: Fri Sep 29, 2017 1:03 pm Post subject: Re: 914 raising fuel pressure |
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Hello,
Injectors i have installed are this one :
https://www.fiveomotorsport.com/hose-type-ev1-flanged-euro-sport-compact
Flow rate is the same and pressure is Min. 36 PSI (2.5 bar), Max. 101 PSI (7 bar)
This pressure will just satisfy the 366cc flow i hope.
Injectors are already installed and motor run like a shit. It looks like it turn on 3 cylinders with no idle.
i try to turn the big screw on the calculator but nothing change.
It's the reason of my initial question
New injectors are EV1 type. I will first install correct connector. Djet connector are similar but enough different to make bad connection;
Next step is changing fuel pressure |
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raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 21520
Location: Oklahoma City
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| Posted: Fri Sep 29, 2017 1:42 pm Post subject: Re: 914 raising fuel pressure |
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| froxy cool wrote: |
Hello,
Injectors i have installed are this one :
https://www.fiveomotorsport.com/hose-type-ev1-flanged-euro-sport-compact
Flow rate is the same and pressure is Min. 36 PSI (2.5 bar), Max. 101 PSI (7 bar)
This pressure will just satisfy the 366cc flow i hope.
Injectors are already installed and motor run like a shit. It looks like it turn on 3 cylinders with no idle.
i try to turn the big screw on the calculator but nothing change.
It's the reason of my initial question
New injectors are EV1 type. I will first install correct connector. Djet connector are similar but enough different to make bad connection;
Next step is changing fuel pressure |
First...is this still the original D-jet fuel injection system?
Second...why do you require 366cc/min? The stock Injector flow rate was 320cc/min or 30.5 lbs/hour.....and 100% of all injector flow rate charts are incorrect for this injector...and all D-jet injectors...for the flow rating listed at 36 psi.
This is the problem with 100% of people selling injectors....and has been for 30 years or more.....they do not have the knowledge of ALL of the engines or vehicles they are selling injectors for.
There have NEVER, EVER, EVER...been any D-jet injectors from the factory or on any system in any car ever built with D-jet....that used 36 psi for the test for flow rate capability or ......ever used this pressure setting in the vehicle.....because the injectors simply are not capable of operating reliably at that pressure at maximum pulsewidth.
You also find most of the charts listing the standard flow rates of ALL injectors as tested at 42 psi..... 
ALL D-jet systems are rated at 28 psi....and can go up to 30 psi in hot weather running....but thats it.
If these injectors are proper replacements...they should be putting out the required 320cc/min at 28-30 psi.
You do not just have the option of bumping your fuel pressure up to 26 psi....that would give you an average of 28% excessive fuel enrichment.
Also...none of the D-jet systems came with an injector that uses the EV-1 connection. While I fully agree that the EV-1 connector is superior and should be used....what this is telling you is that they are selling you an injector that has been modified or improved...or was designed for something else in mind like L-jet injection.
While the impedance they list is close enough....the actual resistance should be 2.3 ohms.
Since from their site they may make custom injectors....you have to know what it is they have made for you.
Ray |
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froxy cool
Samba Member
Joined: June 19, 2012
Posts: 4
Location: Belgique
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| Posted: Fri Sep 29, 2017 2:21 pm Post subject: Re: 914 raising fuel pressure |
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sorry for my uncomplete answer.
Yes, i still have the original Djetronic
Original green injectors for 2 liter motors have 380 cc/min @ 2.0 Bar, 3V, 0.15 mm ± 0.05 mm lift. Mine are made to measure with 380cc flow rate (it's write on it).
The only unknow element is the pressure needed to obtain this flow rate.
i have ask the information to the seller and still waiting the answer |
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raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 21520
Location: Oklahoma City
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| Posted: Fri Sep 29, 2017 5:59 pm Post subject: Re: 914 raising fuel pressure |
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| froxy cool wrote: |
sorry for my uncomplete answer.
Yes, i still have the original Djetronic
Original green injectors for 2 liter motors have 380 cc/min @ 2.0 Bar, 3V, 0.15 mm ± 0.05 mm lift. Mine are made to measure with 380cc flow rate (it's write on it).
The only unknow element is the pressure needed to obtain this flow rate.
i have ask the information to the seller and still waiting the answer |
The green iniectors....that is absolute macimum flow rate....only higher because they are "CAPABLE" of a higher pulsewidth rate.....at WOT.....but otherwise the injector is identical to the lower rated injector....in 99% of driving situations. Unless you are road racing you would never know the difference.
The required fuel pressure....is the stock listed fuel pressure to reach maximum REQUIRED flow. That would be 28 psi.
Also.....the problem the injector people do not realize.....is that it does not matter at what pressure they test and rate that injector for "X" pounds per hour.....it matters what the fuel injection system is capable of running that injector at.
Understand this.....the 1.7L injector is rated at 25.5 lbs per hour.....but that is only at their stupid and unusable test pressures of 36-42 psi......and the engine only requires 19 lbs per hour to run in 99.9% of all instances. It may reach about 23 lbs per hour....at maximum rpm, pulsewidth and wide open throttle. How much time do you spend in that condition?
The US version of the 2.0L injector is rated at 30.5 lbs per hour.....again....at 36-42 psi....a pressure range that no D-jet system has ever operated at......yet the 2.0 only requires about 23 lbs per hour.....and again.....ONLY at wide open throttle...maximum rpm and maximum pulsewidth.
The European 2.0 injectors....are IDENTICAL to the US 320cc injectors.....swme pintle size, angle, spring pressure and opening size and fuel pressure ....except.. that they have a coil .....and driver in the ECU....that allows them to achieve about 5% higher/wider pulsewidth witjout overheating......and that capability is used maybe 1% of the time.....unless you are road racing.
So in 95-99% of your driving....you would never notice the difference between the 320cc injector and the 366cc injector. At idle, off the line and part throttle....there is no difference.
But....to answer your question directly.....all injectors you will buy....that work with your ECU...MUST be used at 28-30 psi. What pressure they tested them at....is irrelevent to what your system is designed to use. Ray |
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froxy cool
Samba Member
Joined: June 19, 2012
Posts: 4
Location: Belgique
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| Posted: Sat Sep 30, 2017 4:02 am Post subject: Re: 914 raising fuel pressure |
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| So, you said this injectors will never work properly or the problem is somewhere else than pressure? |
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raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 21520
Location: Oklahoma City
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| Posted: Sat Sep 30, 2017 8:32 am Post subject: Re: 914 raising fuel pressure |
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| froxy cool wrote: |
| So, you said this injectors will never work properly or the problem is somewhere else than pressure? |
No.....thats not what I said.
What I said....is:
1. that......IF....the injectors they are trying to sell you are the correct size injectors.....they will work properly when used at the correct fuel pressure....which is 28-30 psi.
If they do not put out enough fuel volume at 28-30 psi....they are not the correct injector and will not work....because you cannot use higher pressure...either with that type of low impedance injector....or without recalibrating your whol system.
2. The difference in the 320cc and 366cc injector.....is insignificant in daily driving. If you want to use the normal 2.0 injector you will probably do just fine. Many have done this with no issue.
3. People why typically sell injectors have little or no knowledge of early injection systems like D-jet. They always tell you to make changes to higher pressure....which is incorrect for out system.
You can get rebuilt injectors for the 914 2.0.....here
http://www.autoatlanta.com/Porsche-914-Fuel-Injector-srch.html
Or you can buy brand new properly sized injectors from Standard Motor Products. Ray |
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