# REFERENCE: Fuel Injectors for 1.8t



## groggory (Apr 21, 2003)

*REFERENCE: Fuel Injectors*

I am going to start compiling all the fuel injector info for our cars into one thread. Bear with me and please chime in with any missing information, corrections to misinformation, comments, or suggestions. 

Also, at the trailing end of this thread I will be posting questions that need answering. Please answer those in the name of completeness. 

Thanks! 

Note. This is a supplementary thread to my thread REFERENCE: Fueling FAQ. This thread will only contain information about injectors. I will post another thread in the future regarding all known injector/ MAF/ turbo/ engine size/ compression stock tunes for the 1.8t (or 2.0t stroked). 

--------- 

FAQ 


*Convert cubic centimeters pounds per hour* 
cc * 10.5 = pph 
cc = pph / 10.5 

*Excellent reference documents on many types of injectors* 

*Injector height (Middle of o-ring -> middle of o-ring)* 
..insert a picture diagramming this measurement... 

*Stock Injectors on VAG cars* 
USRT Reference Table 

*Injector Cleaning/ Testing* 

*Choosing injector sizing based on your power goals* 
Reference BobQ's thread on this subject 

Injector Resistance 


*MAF Sizing* 
Many software tunes will require a larger MAF in order for their software to run well. For BT applications, the stock intake is either restrictive or the MAF will not read a high enough number to allow the software to run properly. 

When upgrading the MAF you will also have to upgrade your TIP (turbo intake pipe). 

If you do not want to upgrade this talk to your tuner about a MAF'less file. The ECU will be able to read the MAF (for logging/ diagnosis purposes) but it does not factor it into any calculations. You could very well attach a filter straight to the turbo inlet and call it a day if you run this sort of file. 


Standard 1.8t - 2.5" 

S3/LCR/TT225/VR6 - 2.75" (People refer to this as a 3" even though the ID is 2.75") 

 

*Injector Flow Matching* 
Testing the actual flow of each injector and then bundling groups of injectors together that have a very similar flow number. This will allow a car to operate most efficiently by allowing each cylinder to act most similar to each other cylinder 

*Dirty Injectors* 
Dirty injectors will spray less fuel (causing a lean condition) and spray it using a non-optimal spray pattern resulting in less efficient (read lower gas mileage and lower power output) combustion. 

Example of dirty and clean injectors 









*Types of spray patterns* 


USRT said:


> Factory engineers have gone to great lengths to make sure that fuel is injected in the correct spray pattern for each cylinder head design. Meanwhile, tuners have put up with cold start problems, lumpy idles, misfires and other problems for years. A major reason for this is injectors that are mismatched to the application.
> 
> 
> 
> ...


 *Single Cone* 
*Wide* 
*Dual Cone* 









*Types of injector clips* 
* *ND (Nippon Denso)* 








* *USCAR / Bosch EV6* 
Example cars with this: LS2/LS7 motors and late model Ford motors 
















* *USCAR2 connector* 
Found on Genesis 430cc and Genesis 550cc injectors 
* *Jetronic / Bosch EV1 / Minitimer connector* 
Commonly found on Bosch, Siemens injectors 
This is the connector found on our stock spark plugs and our fuel injector harness. 



















*Injector Impedance* 
Injectors are just electric solenoids. They are normally closed when no voltage is present. When you put a voltage across the coil it opens the solenoid thus allowing your pressurized fuel in the fuel rail to 'squirt' into your engine (in the case of the 1.8t, into the intake runner where it is mixed with the air before entering the cylinder). 



USRT said:


> It is also important to understand that fuel injectors come in two electrical flavors -high and low-impedance. VW ECUs require high-impedance but many standalone systems are equipped to manage the lows. The primary advantage of low-impedance injectors is their faster response time. (That is, the speed at which they can be turned on/off.) When very large injectors (e.g. >580cc) are fitted, low-impedance injectors are much easier to tune for proper idle quality and for use at extremely high rpms. The primary advantage of high-impedance injectors is the fact that less heat is generated in the drive circuit and thusly less complex/expensive circuitry is required. Again, if you have a VW ECU you absolutely must use high-impedance parts.











Before I delve into whether an injector is high impedance or low impedance, it is useful to actually know what impedance is first. 

Impedance (in the case of injectors) is the combination of an inductor's reactance and resistance. 








Resistance (R) and Reactance(X) are measured in ohms (omega) 
Inductance (L) is measured in Henry's (H) 
Impedance (Z) is measured in ohms (omega) 
Frequency (f) is measured in Hertz (Hz) 

Inductance and Resistance can be easily measured by a measuring device. However, Reactance is a function of frequency as such: 
X(L) = 2fL. That is why the manufacturers list injectors as just 'high Z' or 'low Z'. If your ECU is pulsing your injectors at a fast rate, the frequency will be high. If the ECU is pulsing the injectors at a low rate, the frequency will be low. 

Thus, let's put these ideas into the impedance formula: 









And you can see that injectors can be many combinations of resistance and inductance in order to be classified as High Z or Low Z injectors. Each mfg can do it their own way. 

After all is said and done though the ECU needs to be able to drive the injectors. The ECU doesn't directly care if an injector is High or low Z. They both run off the same 12V circuit...but they will act as if they have different resistances, and thus draw different currents. 

Ohm's Law 
V=IR -> I=V/R 
voltage = current * resistance 

P = IV -> P = I^2 * R 
Power = Current * Resistance 

Example (High Z Injector) 

12V circuit. 
High Z Injector (@1000 Hz cycle rate) = 10 ohm 
I=V/R -> I=12/10 = 1.2A 
P=IV -> P=1.2 * 12 = 14.4W 

Example 2 (Low Z Injector) 

12V circuit. 
Low Z Injector (@1000 Hz cycle rate) = 2 ohm 
I=V/R -> I=12/2 = 6A 
P=IV -> P=6 * 12 = 72W 

That means that if you were to hook a high Z injector up to the ECU the ECU needs to use 14.4W to switch. If you do the same with a low Z it needs to use 72W!!! Way too much power. That is where the idea of a resistor box comes in.... 

A resistor box adds a resistor in series with each of the injectors. It is called a resistor 'box' because each box has a row of resistors all packaged up and heat sinked for ease of installation. If we add a resistor box in series with out low Z injectors our 'R' in the equation becomes R(resistor box) + Z (injector) = R 
If the resistor box were to use 8 ohm resistors then the low Z injectors will appear to the ECU the same as the high Z injectors. 


*Injector Height* 

*Injector O-Ring Size* 

 

*Recommended Injector Service Companies* 


Witch Hunter 
- Fuel Injector Cleaning, Flow Matching, Testing 

Racetronix 
- Purchase flow matched injectors at a good price 
- Excellent spec list for each injector sold 

 

Stan Weiss Injector list w/ specs 
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Note: APR Stg3/ 3+ software changed their injector size many times. Early software used >630cc Bosch injectors. Later software used ~380cc Bosch injectors. Call APR and work with them to figure out what size you need. Or send what you have to a flow testing shop to figure out what you already have in hand. The APR promotional video mentions they use 550cc injectors. So who knows. 

Note: I am not including software that runs on stock injector/ engine configurations. There are a ton of them and you don't really need any of this fancy fueling stuff to accomplish goals with that sort of software 

Note: For most every BT software you should be running 2.5"-3" downpipe and exhaust. Don't run a BT and a stock 2-2.25" exhaust! You should also run upgraded intercooler, appropriately sized fuel pump, and high performance intake. 

Note: When fueling over 1200cc it is recommended to run -6AN from the fuel tank forward. You may run into fuel starvation with the stock fuel lines. This is according to user DonSupreme as guided by MikeZ @ Unitronic 

Good read: CONTROVERSY - Injector Dynamics vs. EFI Wizzard/Wizard featuring [email protected] 

Five-O Motorsports Custom Milled and matched injectors 

*Injectors* 
Note: Rated flow is at 3bar unless otherwise noted. 3Bar is the standard pressure Bosch rates their injectors at. 

*[highlight]250cc/ 24lb*[/highlight] 


Bosch 
Model # 
Compatible fuels: 
High Z 
Medium Angle Single Spray Cone Pattern 
?? injector clip 
?? o-ring center->center 








$39 @ USRT 

 

*[highlight]315cc/ 30lb*[/highlight] 
Stock Injectors on AWD, AWW, AWP, AWV Engine Codes 

* Gonzo Stage II 



Bosch 
Model # 
Compatible fuels: 
High Z 
??? Spray Pattern 
ev1 injector clip 
63mm o-ring center->center 
























$35 @ Integrated Engineering 
$44 @ USRT 

Genesis 
Model # 
Compatible fuels: 
High Z 
Dual cone Spray Pattern 
??? injector clip 
??? o-ring center->center 








$50 @ USRT 

 

*[highlight]330cc/ __ lb*[/highlight] 

Genesis II 

*[highlight]380cc/ 36lb*[/highlight] 
Unitronic 380cc on K04 @ 3BAR w/ 3" MAF 
GIAC 380cc @ ???BAR on K03 or K04 w/ ???? 
Note: You can run the APR K04 program @ 3BAR on this injector, but it is not officially APR endorsed. Just a common forum suggestion 
 

This is the Audi TT225 injector sizing 


Bosch 'White Giant' 
Model # 
Compatible fuels: 
High Z 
??? Spray Pattern 
ev1 injector clip 
63mm o-ring center->center 
Video 
















$55 @ Integrated Engineering 
$50 @ CTS Turbo 

Siemens 
Model # 
Compatible fuels: 
??? Z 
??? Spray Pattern 
?? injector clip 
?? o-ring center->center 

Video 

Genesis 
Model # 
Compatible fuels: 
High Z 
Dual Spray Cone Spray Pattern 
??? injector clip 
??? o-ring center->center 
Video 








Video 
$69 @ USRT 

 

*[highlight]415cc/ 39lb*[/highlight] 
Unitronic 415cc @ 3.5 bar on GT28xx w/ 3" MAF 

Can be used at 3.5BAR for compatibility with [email protected] software 



Genesis 
Model # 
Compatible fuels: 
High Z 
Dual Spray Cone Spray Pattern 
??? injector clip 
??? o-ring center->center 








$75 @ USRT 

 



*[highlight]430cc/ 41lb*[/highlight] 


Bosch 
Model # 0 280 156 012 
Compatible fuels: 
?? Z (12 ohms resistance) 
??? Spray Pattern 
??? injector clip 
??? o-ring center->center 








$ ??? 

Genesis 
Model # 
Compatible fuels: 
?? Z 
Dual cone Spray Pattern 
USCAR2 injector clip 
??? o-ring center->center 








$ 69 @ USRT 

 

*[highlight]440cc/ 42lb*[/highlight] 
Unitronic 440cc @ 3 bar on GT28xx w/ 3" MAF 
 

Gonzo Stage 3 @ 3 bar on hybrid turbo w/ TT225 "3 inch" MAF Housing (Keep Stock Sensor) 



Delphi 
Model # 
Compatible fuels: 
Low Z 
Single Cone Spray Pattern 
??? injector clip 
??? o-ring center->center 








$46 @ Integrated Engineering 
$50 @ USRT 

Bosch 'Green Giant'/ 'Green Top' 
Bosch Green Top Video 
Note: Green Tops were the first version of the 430cc injector that bosch made. Around 2002 lots of tuners were having a hard time making files for the so called, 'green tops.' The Green Tops had the wrong flow pattern for our 20V engines. 
However, later, Bosch came out with the 'green giants.' The Green Giants flowed the same but they had the proper flow pattern for our engines. This is the injector you should go with if you have need of a 430cc injector for the 20V platform. 
Model # 
Compatible fuels: 
High Z 
Wide Spray Pattern 
??? injector clip 
???mm o-ring center->center 
Video 








$50 @ Integrated Engineering 
$40 @ CTS Turbo 

 

*[highlight]525cc/ 50lb*[/highlight] 


Delphi 
Model # 
Compatible fuels: 
Low Z 
??? Spray Pattern 
??? injector clip 
??? o-ring center->center 








$80 @ Integrated Engineering 


 

*[highlight]500cc/ lb*[/highlight] 

Genesis II 


*[highlight]550cc/ 52lb*[/highlight] 
Unitronic 550cc @ 4 BAR on GT28xx w/ 3" MAF 
Revo 550cc @ 3BAR on GT28R or GT28RS or GT2871R w/ 2.75" MAF 


Bosch 
Model # 
Compatible fuels: 
High Z 
Wide Spray Pattern 
??? injector clip 
??? o-ring center->center 
















$50 @ Integrated Engineering 
$50 @ CTS Turbo 

Genesis 
Model # 
Compatible fuels: 
High Z 
Dual Spray Cones Pattern 
??? injector clip 
??? o-ring center->center 








$75 @ Integrated Engineering 

 


*[highlight]630cc/ 60lb*[/highlight] 
Unitronic 630cc @ 3 BAR on GT28xx or GT3xx w/ 3" MAF 
Eurodyne 630cc @ 3 BAR on GT28xx or GT3xx w/ 2.5" MAF 

Gonzo Stage 4 , 3 bar on BIG TURBO. GT28 to PTE6262 series or similar, TT225 "3 inch" MAF Housing (Keep Stock Sensor)  



Genesis II 


Siemens 
Model # 
Compatible fuels: 
High Z 
Dual Spray Cones Pattern 
??? injector clip 
??? o-ring center->center 









$50 @ CTS Turbo 

 
[/COLOR] 

*[highlight]650cc/ 60lb*[/highlight] 
 


EFI Wizard 
Model # 
Compatible fuels:compatible with the additive MTBE 
High Z 
Wide Spray Cone Pattern 
??? injector clip 
??? o-ring center->center 



tstarkz123 said:


> you will need the injector, 12.5mm extender with 14mm orings, and a Sumitomo (Denso) electrical connector pigtail or Denso female to EV1/Jettronic male adapter




 

*[highlight]725cc/ 69lb*[/highlight] 

Injector Dynamics 
Model # ID725 
Compatible fuels: 
??? Z 
Single Cone Spray Pattern 
??? injector clip 
??? o-ring center->center 

 

*[highlight]750cc/ 69lb*[/highlight] 

EFI Wizard 
Model # 
Compatible fuels:compatible with the additive MTBE 
High Z 
Wide Spray Cone Pattern 
??? injector clip 
??? o-ring center->center 

 



tstarkz123 said:


> you will need the injector, 12.5mm extender with 14mm orings, and a Sumitomo (Denso) electrical connector pigtail or Denso female to EV1/Jettronic male adapter


 

*[highlight]780cc/ 75lb*[/highlight] 


Delphi 
Model # 
Compatible fuels: 
Low Z 
Single Cone Spray Pattern 
??? injector clip 
??? o-ring center->center 








$85 @ Integrated Engineering 

 

*[highlight]830cc/ 79lb*[/highlight] 
Unitronic 830cc @ 3 BAR on GT28xx or GT3xx w/ 3" MAF 

Delphi 
Model # 
Compatible fuels: 
High Z 
??? Spray Pattern 
??? injector clip 
??? o-ring center->center 








* Run by groggory on GT2871 + Uni. No problems. 
$65 @ Integrated Engineering 

 

*[highlight]870cc/ 85lb*[/highlight] 
Eurodyne 870cc @ 3 BAR on GT28xx or GT3xx w/ 2.5" MAF 
 

 Siemens 870 Deka 
High Z 


[email protected] said:


> The Deka 870's idle awesome, on standalone, and I've gotten them to work just fine on Maestro too... Have not played with the uni file, but when it's non adjustable, using injectors other then what the file was written for is just asking for trouble. So is putting a maf onto a car that probably leaks boost / vacuum like a sieve.











$59.99 @ Integrated Engineering 

 
*[highlight]880cc/ 85lb*[/highlight] 

Delphi 
Model # 
Compatible fuels: 
Low Z 
Single Cone Spray Pattern 
??? injector clip 
??? o-ring center->center 








$85 @ Integrated Engineering 


*[highlight]1000cc/ 95lb*[/highlight] 
Eurodyne 1000cc @ 3 BAR on GT28xx or GT3xx w/ 2.5" MAF 
 

Injector Dynamics 
Model # ID1000 
Compatible fuels: 
??? Z 
Single Cone Spray Pattern 
??? injector clip 
??? o-ring center->center 


 Genesis II 


EFI Wizard 
Model # 
Compatible fuels:compatible with the additive MTBE 
High Z 
Wide Spray Cone Pattern 
??? injector clip 
??? o-ring center->center 



tstarkz123 said:


> you will need the injector, 12.5mm extender with 14mm orings, and a Sumitomo (Denso) electrical connector pigtail or Denso female to EV1/Jettronic male adapter


 
Delphi 
Model # 
Compatible fuels: 
Low Z 
Single Cone Spray Pattern 
??? injector clip 
??? o-ring center->center 








$85 @ Integrated Engineering


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## groggory (Apr 21, 2003)

*[highlight]1260cc/ 120lb*[/highlight] 
Unitronic 1200cc @ ??? BAR on GT40xx w/ ???" MAF, EBC/MBC, and driver box (from SEM motorsports) 
 


Lucas/ RC 
Model # 
Compatible fuels: 
Low Z 
Single Cone Spray Pattern 
??? injector clip 
??? o-ring center->center 








$60 @ Integrated Engineering 

 

*[highlight]1600cc/ 152lb*[/highlight] 


Bosch 


Genesis II 


 

*[highlight]1680cc/ 160lb*[/highlight] 

*[highlight]2000cc/ 190lb*[/highlight] 


 Genesis II 


Injector Dynamics 
Model # ID2000 
Compatible fuels: 
??? Z 
Single Cone Spray Pattern 
??? injector clip 
??? o-ring center->center 



tstarkz123 said:


> you will need the injector, 12.5mm extender with 14mm orings, and a Sumitomo (Denso) electrical connector pigtail or Denso female to EV1/Jettronic male adapter


 
EFI Wizzards 
Model # 7-10-09-09-122402 / 0280158117 
Compatible fuels: compatible with the additive MTBE (VP's q16 and VP's Import blend) 
High Z 
Single Cone Spray Pattern 
??? injector clip 
??? o-ring center->center 
















$225 @ Force Fed Engineering 



tstarkz123 said:


> you will need the injector, 12.5mm extender with 14mm orings, and a Sumitomo (Denso) electrical connector pigtail or Denso female to EV1/Jettronic male adapter



 

*Tools* 
..need to add stuff 

*Adapters* 


USCAR2 injector -> Jettronic car clip 








$11.25 @ USRT 

1.8t spacers 


USRT said:


> Fuel rail spacers required for all 1.8T engines except for AEB code. Please contact us with any questions regarding fitment. Genesis injectors do not require spacers except where noted.











$10 @ USRT 

 

*Misc* 

Fuel Injector Spare Parts


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## groggory (Apr 21, 2003)

*Spray Patterns*



Genesis
Video

Bosch Green Tops
Video

Bosch Indy Blue Tops
Video

Bosch 1000cc
Video



*Comparisons/ Educational*
Early gen Bosch vs. Gen3 Bosch
Lucas discs to Gen3 Bosch
Injectors in Slow Motion
High speed camera of working 2 valve/cylinder engine --VERY COOL!!!


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## groggory (Apr 21, 2003)

....Post4....


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## groggory (Apr 21, 2003)

...Post5...


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## groggory (Apr 21, 2003)

...post5


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## groggory (Apr 21, 2003)

What do you guys think so far? Anything major I need to add?


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## TSTARKZ123 (Oct 1, 2004)

Question: Are you saying our cars are Jetronic connectors? I thought we were EV1? I could be wrong. Good start though!


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## groggory (Apr 21, 2003)

TSTARKZ123 said:


> Question: Are you saying our cars are Jetronic connectors? I thought we were EV1? I could be wrong. Good start though!


 I believe Bosch EV1 is the same as a generic Jettronic connector. 

I believe EV1 is a bosch injector form factor, not a specific connector. When you say EV1 connector, you mean the connector found on a bosch EV1 form factor injector...aka a jetronic connector in general speak. 

For instance, bosch also has EV6 and EV14 injectors that still use the Jet plug 
http://www.mksautobusiness.fi/page_injectors.html 

Feel free to keep bringing up more information, clarifications, and mistakes. This FAQ is no good if it's filled with misinformation. 

Thanks!


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## groggory (Apr 21, 2003)

What's the difference between the bosch green top and the bosch green giant 

As referenced in this thread 
http://forums.vwvortex.com/showthread.php?4056248-***-Fuel-Injector-Fuel-Pump-Specials-CTS-Turbo-***


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## groggory (Apr 21, 2003)

bump. Help me fill in the blanks people. 

For those of you who have been throwing me PMs with additional information...Thank you.


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## 18T_BT (Sep 15, 2005)

groggory said:


> What's the difference between the bosch green top and the bosch green giant
> 
> As referenced in this thread
> http://forums.vwvortex.com/showthread.php?4056248-***-Fuel-Injector-Fuel-Pump-Specials-CTS-Turbo-***


they discontinued the green tops and replaced them with the green giants


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## TSTARKZ123 (Oct 1, 2004)

FYI: If you're looking to run any of the large 2000cc injectors ie EfiWizards or ID2200s you will need the injector, 12.5mm extender with 14mm orings, and a Sumitomo (Denso) electrical connector pigtail or Denso female to EV1/Jettronic male adapter.


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## bootymac (Apr 19, 2005)

Good thread! I came across something about the TT225 injectors and I was hoping someone could clarify the differences between the white injectors from the BEA (0 280 156 063) vs. blue injectors from the AMU (0 280 155 892).

I read that the spray pattern is the only difference. If so, which one is preferable?


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## saps (Jul 10, 2009)

very cool and informational thread, definitely FAQ material. Thanks man!


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## groggory (Apr 21, 2003)

bootymac said:


> Good thread! I came across something about the TT225 injectors and I was hoping someone could clarify the differences between the white injectors from the BEA (0 280 156 063) vs. blue injectors from the AMU (0 280 155 892).
> 
> I read that the spray pattern is the only difference. If so, which one is preferable?


According to this thread...
http://www.passatworld.com/forums/archive/index.php/t-237442.html

the 0 280 156 063 is the EV6 type.

According to USRT's post
http://www.usrallyteam.com/content/tech/18t_injectors.html

the 0 280 155 892 is of the EV12 type.

So I think that would be your main difference.


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## groggory (Apr 21, 2003)

Updated to list updated details on the green top vs. green giant issue.


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## Issam Abed (Feb 12, 2004)

Always love wholesome technical threads. :thumbup:


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## Andaloons (Apr 16, 2004)

Another freakin beautiful thread from groggory! Well done! :thumbup:


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## groggory (Apr 21, 2003)

Does anyone know what maf/injector combo that malone tuning supports out of the box? I'll update the injector list to also include malone tuning.

Thanks.


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## groggory (Apr 21, 2003)

^^ Bump for updates to include 870cc Siemens Deka injectors

...also, does anyone have the info I asked about the Malone Tuning tunes?

Also, I've been trying to have tunes and injectors cross referenced. Could people chime in and add in knowledge of what injectors seem to work BEST for a given tune? I'll add in your advice to the injector listings.


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## warranty225cpe (Dec 3, 2008)

groggory said:


> ^^ Bump for updates to include 870cc Siemens Deka injectors
> 
> ...also, does anyone have the info I asked about the Malone Tuning tunes?
> 
> Also, I've been trying to have tunes and injectors cross referenced. Could people chime in and add in knowledge of what injectors seem to work BEST for a given tune? I'll add in your advice to the injector listings.


Will have an update for you on EV14 750cc and Gonzo tune StageIII/E85 file.


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## groggory (Apr 21, 2003)

Corrections per [email protected]

Point of correction...
re: the electrical connectors...
The Bosch EV6 is an injector type and not a connector type.
USCAR is the connector
Bosch EV1 is the injector type and not the connector type.
The connector used on all EV1 is Jetronic aka Minitimer
EV6 often use Jetronic/Minitimer but also often use USCAR
Bosch EV14 come in Jetronic/USCAR/Denso


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## Rod Ratio (Jun 6, 2012)

Sub'd for nerdy goodness


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## PT16V (Jun 16, 2012)

The calculation for Power is incorrect for this application, you are assuming DC source. 
Injector resistance and source voltage are not sufficient to calculate power. 
What is still missing is the inductance of the coil, frequency (related to RPM), and duty cycle. 
The inductance of the coil can be measured using an LCR meter but that wont yield accurate calculation either. the injector is an elctro-mechanical device, the force induced by the coil to move the injector plunger that is spring loaded will effectively add load resistance. 
I am not an injector specialist, meaning that I cannot confirm to you whether the specified inductor resistance does include the mechanical load or not, but these can be measured. 
Back to the calculation, if the inductance is very high, one can ignore its effect at some or all frequencies, only then you can simplify I=V/R*sqrt(D), therefore power P=V^2/R*D. 
Hope this helps. Adding resistors and or resistor boxes is not the right way of doing things (even if other people do it for lack or better resources). The added resistor will limit the current into the coil, and will slow the turn on time and the resulting programmed duty cycle. For better control of fuel injection windows it is better to have as fast as possible turn on time and turn off time so you can selectively inject the fuel at the most optima time. 
Note that some high impedance injectors can be driven momentarily at much higher voltage to "snap" them ON... 
Hope this helps


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