How To Upgrade Injectors and Resistors on a Lexus V8 1UZFE

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I have been looking around for upgrade injectors for my Lexus LS400 which has 1UZFE engine.  I tried to contact few places for new injectors, but price is over the ceiling.  An average 440 cc  is about $100 each.  Therefore, I want to use some oem injectors from other cars.

Before I start, I would like to give some data about our 1UZFE injector specifications:  The Lexus-Toyota V8 engine has Top Feed, 251 cc (max out 50 bhp per injector) with 13.8 ohms.  The maximum out put of these injectors in a stock V8 is about 400 bhp.  However, for forced induction application those injectors are not big enough.  Therefore, we are looking out for larger injectors.

As of right now, I have only tried two different oem injectors.  The first injector I tried was the Supra MKIII Twin Turbo.  Those injectors are from 7MGTE engine.  The 7MGTE injector come with 440cc/min stock (Max 688 bhp).  Those injectors fit perfectly.  However, those injectors are low impedance.  That means its has 2-3 ohms.  If you want to used those injectors, you would have to add a 10 ohms resistor to the power wire.  If you think that is too much trouble, then you need to look for top feed, high impedance and physically fit into the fuel rail and lower intake.

Actually the 7M injectors need slight modification on the electrical wire clip.  The 7M injector has opposite plug configuration.  To fit it properly, you need to grind down an injector plug guide.  Its very easy.  However, for direct plug and play would be the 7MGE injectors (504 bhp max).  The 7MGE light green color plug is 315 cc (63 bhp per injector) with Type F connector and the yellow plug is only 295cc/min.  7MGE is not a bad fuel upgrade for a mild boost level.  I would say around 11-13 psi.  Once again, if your power desire is higher than larger injectors will be required.

Since I do not want the trouble of adding a 10 ohms resistor (local electronic stores sell them $1.00 for 5 resistors), therefore I will be using other injectors that are high impedance.  I do some search on the internet and ask few questions and made some phone calls.  I finally purchased ONE 1988-1990 Mazda RX 7 550 cc injectors (Max 848 bhp).  With 550 cc injector it would easily support 550 rwhp with potential for growth.  I purchased one just in case they do not fit physically.

The pre-1988 injectors are low impedance.  Post-1988 are high impedance.  The RX 7 injectors are about 1/4″ longer in the lower part of the injector.  Beside being longer, it fit perfectly.  I was afraid due to the extra length that might cause some problems.  I took out my disassembled engine and test it out.  The length did not affect anything.  However, the Mazda clip is slightly different therefore I need to order a set of RX 7 injector clips.  The sad thing is that Mazda dealer does not sell connector by itself.  Junk yard or online would be your best bid. Here is a usable data about Lexus\Toyota Injectors.  Below is a gallery with descriptions.

Injector Size Max per Injector Max of 8 injectors HP at 80% Desire PSI

Notes:

1UZFE 251cc/min 50 bhp 400 bhp 305 bhp 0-7 psi Stock Type F
7MGE 295 (yellow) 60 bhp 480 bhp 359.6 bhp 7-11 psi Plug & Play
7MGE 315 cc/min (light green) 63 bhp 504 bhp  384  bhp 12-14 psi Plug and Play (yellow is 295 cc) Type F
1G Eclipse Non Turbo 390 cc/min 78 bhp 624 500 bhp 14-18 Type C Clip, 13.8 ohm
7MGTE 430 – 440 cc/min 86 bhp 688 bhp 536 bhp 18-22 psi Need 10 ohm resistor and Type E connector or
grind the 440 injector guides/grooves and plug in the clips
Mazda Rx 7 550 cc/min 106 bhp 848 bhp 670 bhp 20-27 psi Need Rx 7 connector

 

 

 


Comparison between injectors. From right to left. The further right injector is the 1UZFE injector 251cc/min, middle is the 7MGTE 440cc injector, Left injector is the 1988 RX 7 550 cc

The injector clips are different among the three injectors. 1UZ and 7M is the isomer of each other (half oval & half rectangle shape). RX injector is more retangle shape.

Comparing injector opening. 1UZ has two small openings, 7M has two large and two small openings. RX has one huge opening.

A closer look at the injectors openings.

Mock fit into the lower intake with 4 screws slightly tightened. The red is the RX injector, the right injector is 1UZ.

A closer look and different angle.

The RX injector is flush to the lower intake. The injector still within the gasket impression.

Looking at the OEM 1UZ injector fitmentship. Its slight rectracted from the insertion.

Flush fit but still with the gasket impression.

Comparing both injectors openings and fitmenship.

Installed to the head. Red is RX and green is 1UZ

A closer look of the new upgraded 1988 Mazada RX 7 550 cc/min injector.



Resistor:  After months of research and asking an expert electronic engineer like Kdog from our forum.  I finally understand and get the right resistor the the low impedance injectors.  The MKIII 7MGTE has 2.9 ohm and our 1UZ have 13.8 ohm system.  A 10 ohm resistor would work.  However, resistor as have another factor, Watts. Here are the formulas:

Watt = Volt x Amp

Amp = Volt/Ohm

We know ohm is 2.9 (440 cc/min) plus 10 ohm resistor. The total ohm is 12.9 ohm.

Amp = 12 volt/12.9 ohm, therefore the amp is .93

Watt = 12 volt x .93 amp = 11.16 watt. Therefore, 10 watt would work.

You would need eight 10 ohm/10 watts resistors or you can use four 5 ohm/20 watts resistor is your are wiring batch style.  One batch has 2 injectors.  Here is the logic behind it: 

Resistors in series: R = R1 + R2

Resistors in parallel: 1/R = 1/R1 + 1/R2 (courtesy of Miles B)

The resistors are cheap.  They are about $1.00 for two resistor and much cheaper online.  I have seen $1.00 for 5 resistors online.  This is the cheapest and easiest way to change from high to low impedance.  There are other ways, like using Camry ignition driver, but the cost is very high and very complex.  With two dollars worth of resistors and solider the resistors and you are set.  From there u can run all those high performance injectors and save lots of money.  Once again, you can always reverse the setup with minimum work.  All I can say is that I save hundreds perhaps close to one thousand dollars with this setup and loving it.  Thanks to those experts help.

You can read more from this link http://www.stealth316.com/2-injectortypes.htm.  From my personal experience.  I double the resistors (2 resistors) per trigger line in the area of the ECU.  I connect two resistors in parallel configuration to reduce resistance to about 2.9 ohms.  However, if you need more fuel flow, you can get two 6.8 ohms/10 watts.  This will lower the resistance therefore greater fuel flow.

The stock ECU can manage to lower around 50%.  However, 440 cc/min would be too large for the stock ECU.  I am using an Apexi S-AFC and it can decrease an additional 50%.  Therefore, my car is running slight rich at idle, but manageable.

Any injectors greater then 440 cc/min would require a stand alone computer.  The Supra MKIII N/A injectors such as 295 cc/min and 315 cc/min would be just plug and play.  Everything fit.  Here are pictures of the whole process:


A fresh package from a local electronic store. $1.00 for two resisitors

Resistors are connected in parallel 10 ohms + 10 ohms

Resistors are solder in with the wires for solid connection.

Driver side, below glove compartment is the ECU. Find the wires (4). Please refer to wiring diagram.

Four wires, two resistors each. Check wiring diagram above for proper wiring.

A closer look at the resistors. Parallel connection.

Different angle on the resistors.

Solder the connection is a must.

What a mess, dont worry. I opened it up for picturs.



 

1G Eclipse 390 cc/min N/A injectors upgrade:

The first generation Eclipse up is perfect for mild boost level.  From my experience, the 440 cc/min is too big of injectors to run with Apexi S-AFC.  The maximum cc/min for the Apexi is 390 cc/min.  I have ran the Supra MKIII Turbo 440 cc/min for about 5 months and the car ran very rich and the idle was very poor.  I decided to down size to 390 cc/min for my application.  These 390 cc/min injectors will max out at around 500 rwhp.  That is pretty my street goal.  Since the none turbo version of the injectors are high impedance, therefore no resistors are needed.

However, you will need to change your OEM Type E clips to Type C clips.  For idle quality, I highly recommend these injectors for those owners with Apex S-AFC or Greddy E-Management.  50% reduction is perfect and able to handle some serious horsepower.  Remember, the turbo version is low impedance.  It still work, but you will need to used resistors like above.

Supra MKIII 7MGTE Injectors Upgrade:

Here are an outline of using 7MGTE Supra MKIII Turbo injectors 440 cc/min to the 1UZFE.  This is based on my personal experience.

1. Need 8 440 cc/min.  Used injectors can be obtained via Ebay or Toyota forums.  Get them balanced and tested.  The cost of used injectors should not be more than $100 for 8 and test and balance of the injectors should be around $10 each.  Total cost would be around $180.

2. 8 10 ohms/10 watts resistors.  They be obtained at a local electronic store.  Wire them in parallel at the ecu site.  The ECU is under the glove compartment.  Double check the wiring diagram for your car.

3. Use a sander or grinder, remove the new injectors two top grooves or guide.

Here is how it looks like.  Courtesy of Kdog and Harry Lemmens  (click to enlarge)

  

The two people above really contribute to this resistor wiring.  I would not able to do this without their help.  They are the experts in electrical and electronic field.  The first picture is from Kdog and the second is from Harry Lemmens.  Thank you gentlemen.

NOTE:  Some people have email about 7MGTE injectors.  As u can see, the size and the length is the same as the stock 1UZFE injectors.  They fit perfectly.  However, J-Spec 7MGTE is slightly different.  After you grind the grooves from the 7MGTE injectors, the 1UZFE clip will work fine.  However, I would recommend you use a tie lock to tie them up.  This is just an insurance so the clip would not come off.

I will have more pictures on wiring instructions and demo.  This is great stuffs.

That is all, it’s simple and you will save hundreds for this project.  I only recommend this project if you are going to fun greater than 18 to 22 psi.

Do you have any questions? If so, please head over to the forums to get a quick answer or share your experience!

This is a freelance site with no support by huge companies.  I have been doing most of the R&D and technical write-ups by myself with my personal money and literally thousands of hours of my time.  I have taken extra steps to demonstrate in details how things are done.  Currently I am one of the few people doing Lexus V8 research and performance enhancement.  This effort comes from my personal love for this wonderful engine.  Most of the modifications are from trill and errors.  There is no cookbook for the 1UZFE modifications and its a virgin territory for performance.  The parts, labor, web development and site hosting are from my personal hobby money.  If you feel my efforts help you in any form, please do not hesitate to donate any amount of money to support this site. You have no idea how much I appreciate it!

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