Apexi LJetro Vs Apexi Djetro - Whats the deal??
For some time this debate has gone on with various opinions and ideas with no real concrete evidence/proof or logic to back it up.
There are two distinct differences between the LJetro and Djetro PowerFC (and presumbably other LJetro/Djetro ECU's) and we will discuss them as this is a hot topic.
Having since worked out the mathematics behind the Load axis calculations for both the Ljetro and Djetro versions of the PowerFC I can show you how they are both calculated.
First we should look at each base model and how it works;
Apexi PowerFC Ljetro Version
Uses standard airflow meter
20x20 Load Map
Other addtional supported airflow meters (selectable on menu)
Apexi PowerFC Djetro Version
Uses optional supplied Apexi Map sensor
20x20 Load Map
Other addtional supported map sensors (selectable on menu with correct voltage and offset)
Both units are scalable upto 1100bhp with supported modifications, sensors, injectors etc.
i suspect the ljetro version was created first, and then Apexi following demand added the Djetro version for some select cars as they found customers were migrating to other ECU's to map sensor support.
Ljetro Vs Djetro Load Axis:
Both have arbitary values for Load indiciation, Djetro has higher RPM as its from RB26 Djetro
Airflow Meter Ramp:
Voltage Ramp for Airflow meter load signal. Infinitely scalable, as we can rescale any given airflow meter.
The most commoin airflow meters are supported out of the box, Z32, Q45 and Apexi Power Intake.
Seemingly all the Apexi Power Intake does it alter the ramp values, which should yield slightly higher airflow load values, which should drop them on the map 1.3rows if that, ever so slightly.
Map Sensor Ramp:
Voltage Ramp for Map Sensor. Each sensor has a single Offset and nothing more. Fixed offset value
Optional Map Sensors include GM5bar map sensor and Denso unit's also. The Apexi one is in fact a Denso unit. The only map sensor supported out of the box is the optional Apexi one (denso rebadged).
GM 5 bar and other sensors need their scale and offset placed into the PowerFC to work.
Apexi Ljetro Load Calculation:
LOAD = CORRECTION * (16384 * Airflow lookup(MAFSV) / RPM)
Airflow is proportional to RPM so this is why we are divisible by RPM.
We obtain MAFSV from our running environment.
We lookup the Airflow value from the Airflow ramp table (viewable by datalogit) and use this value.
We lookup the CORRECTION value from the Airflow corretion table, for 4.48v and higher my correction is 84%
ACR MAPN MAPP Rpm Load MAFS1 V MAFS2 V Inj ms Inj +/- IGN Dwell Boost Duty WtrT AirT Knock
0 11 14 4694 10725 4.705 0 15.568 256 21 51 -760 95 75 175 7
0 10 14 4591 10918 4.73 0 15.88 256 21 51 -760 95 75 175 4
0 11 14 4725 10915 4.745 0 15.952 256 21 53 -760 95 75 175 1
0 11 14 4950 10956 4.835 0 16.08 256 21 54 -760 95 75 175 3
0 12 14 5175 11121 4.9 0 16.528 256 21 58 -760 95 75 175 7
0 12 14 5202 11153 4.93 0 16.632 256 21 58 -760 95 75 175 7
0 13 14 5561 10997 4.99 0 16.464 256 21 62 -760 95 75 175 3
LOAD = 0.84 * (16384 * 3598 / 4950)
The answer gives us 10003.57 and we can see for load point 14 we have an Load value of 9642.
The load value for point 15 is 11571 so we place our load axis on 14 with a value of 10003
As we can see here the load will always increase as the engine speed increases.
More and more air comes into the system and thus airflow load will always keep increasing until redline.
There have been doubts over this as many people see bog stockish R33 GTST's drop to load points 15 and shoot across.
This is due to the fact they are maxing our the airflow meter at 5.10 or very close to.
The reason it drops to load point 15 is because the majority of them have airflow % correction somewhere near 80% for 4.48v and higher.
Appexi Djetro Load Calculation:
LOAD = Map Sensor Offset * Map Sensor(PIMV)
We lookup the Map sensor offset and use this value (viewable by datalogit).
We obtain PIMV from our running environment
BatVolt MAPN MAPP Rpm PIM PIM V TPS V Inj ms Inj +/- IGN
14.3 2 8 1515 6565 1.996 0.501 2.111 152 14
14.3 2 8 1499 6414 1.95 0.501 2.007 152 14
14.3 2 9 1536 6782 2.062 0.501 2.176 152 14
14.3 2 9 1529 6696 2.036 0.501 2.184 152 14
LOAD = 3289 * 1.95
The answer gives us 6413 and we can see for load point 8 we have an Load value of 5938.
The load value for point 9 is 11571 so we place our load axis on 14 with a value of 6681.
As we can see once pressure is fixed or doesn't increase any more, the load value doesn't.
This will result in a horizontal shoot across method once target boost pressure is reached.
This is because the Djetro version uses air pressure and runs a guesstimation method to calculate airflow.
As the engine speed increases more and more air comes into the system, pressure remains the same and the load axis remains the same.
The Djetro has two additional features which are;
IGN vs TPS correction
INJ vs TPS correction
These are there presumably to assist in correction for the throttle position sensor.
These will have an affect on the output figures but don't appear to adjust the load bearing.
These are much like Airtemp correction or water temp correction, they affect values but don't adjust load bearing.
-> Out of the box, works great, plug and play nothing more to add/change
PR: This is suitable for the majority of customers
-> Supports factory airflow meters and larger models
PR: This is suitable for the majority of customers and tuners (less fiddling the better)
-> Some tuners/owners believe the airflow meter is a restriction
PR: Turbocharged cars have a restriction after the compressor outlet, not before.
-> Once you max out the airflow meter it can't show any more useful load to the ECU
PR: Once you max out a given airflow meter, move to a larger unit with higher resolution.
If you stay with an airflow meter maxing out (stockish GTST customers) then you basically have the same
load bearing as Djetro customers. Once you peak or reach max airflow (the most the AFM can show) then Load doesn't increase anymore.
This is dead obvious for stockish GTST customers who do a map trace.
-> No air intake restriction
PR: Turbocharged cars have a restriction after the compressor outlet, not before.
-> No airflow meters in pipework
PR: This can be helpful for large twin applications. It may also help avoid chuffing or compressor shuffling.
With correct pipework and bends you should be able to run twin MAF's or even a big single MAF relocated in the after FMIC pipework
-> Can't max out airflow meters
PR: This is a valid Pro. But once you max out any airflow meter simply change to a larger unit or more scalable unit.
-> You loose load point resolution once you reach target boost (horizonatal shoot across, as pressure never changes)
PR: This would be my main caveat of moving to map sensor system, the lack of tuning points, as the map isnt a 20x20 useable map anymore.
Apexi PowerFC Djetro PRO - Does it exist???
From time to time there are various rumours or confusion over specific ECU models. The Apexi PowerFC DJetro PRO does not exist for retail sale / standard production use. The Apexi drag car is believed to run a Djetro PRO version which gives it spark cut, 0kmh launch control and djetro. I believe Apexi have simply modified the mainboard firmware to include both chipsets, being Apexi they can do whatever they like.
There are two ways that I can think of to achieve this goal;
Apexi PowerFC Pro & HKS VPC (Vein Pressure Conveter)
The VPC is an old legacy HKS device which lets you run map sensors and emulate standard AFMS.
I dont think it is supported on the mainstream skyline branch but I have seen it for z32 300zx.
I have also seen someone run an rb26 Djetro PFC on a 300zx as they are compatible (with changes).
Apexi PowerFC Djetro & Gizmo Launch Interface
The Gizzmo launch interface is a spark cut / anti lag box which runs in parrallel of the 6 igniton drivers.
This provides on demand spart cut for anti lag launches and flat shifting.
Why buy a PowerFC? Aren't they discontinued????
As everyone knows the PowerFC's future is in doubt. Apexi have had some financial issues and now there are delays with ordering models.
Some units have been scrapped and wont be made anymore. But nevertheless the are still thousands of second hand units on the market.
There are still plently of tuners around and still plently of workshops who support it. I am even trying to resurrect the RB20/RB25 powerfc by using an RB26 PFC and a custom loom.
So needless to stay its not like all the PowerFCs in the market will magically vanish or disappear tomorrow so keep on 'trucking'.
There are however some alternatives to the PowerFC on the market and we should not be biased here, as that is not fair.
I'm a proven Apexi PowerFC fan but like any ECU it has downfalls and bad sides, most things do.
So let's look at some of the alternatives and how they compare;
Apexi SAFC & SITC
Below is some brief ntoes on each of the units and my thoughts / knowledge on the them.
This is by far no means of a techincal comparison or tuners views on each of them.
You should ALWAYS discuss any ECU choices with your tuner before you even start.
The Greddy Emanage is a piggyback system onto the stock ECU.
That is, its a generic remapper for stock ECUs. So if you have a GTR, GTST, Evo, Subuaru etc the emanage can sort it out.
Its a stage 1 interceptor which intercepts IGN, INJ, and all the main sensors to control the car and let you "tune" the main system.
The stock ecu is still present so complex things like 4wd, traction control, abs systems etc work just as normal.
The unit needs a main harness to suit your car but the unit is generic so you can sell (or buy it from) it to anyone.
Once installed you can make relevant changes as needed such as airflow meter changes, AFR tuning, IGN timing etc.
There are some limits into the size of the injectors you can run and other changes as its an interceptor but all in all a good unit.
I have never been a fan on a remapper/interceptor but if I was going to choose one, the emanage would be the one.
The HKS FCON is by far one of the more advanced and suprior ECUS for the japanese domestic market.
This bad boy suports EVERYTHING known to man and more than you can poke a stick at.
AFMS, Map sensors, twin kits, everything is virtually supported and it includes a 32bit ecu with 32x32 map area.
The HKS FCON has its drawbacks however, in Australia only one place can tune the FCON which is BD4's in Sydney.
SO if you live in Melbourne, forget it you can't touch jack shit on the ECU. There is a graphical FCON unit but I dont think its the equiv of the PFC hand controller.
The HKS FCON is locked to the HKS pro writer software so you can touch it with laptop software of your own hacking. Tuners need to be official HKS pro tuners to get the software. So if there are local HKS FCON tuners in your area go nuts, get it and enjoy, but for most there are no local HKS FCON tuners so its useless. Much like a mines ecu, no local tuners. I would love to try out this ECU and see how far and how much you could tune it, but sadly I cannot as I am not a certified HKS tuner (haha).
Apexi SAFC & SITC
These two little brothers are like pea's in a pod. You cant link them together directly but they give a good comprimise for standard ecu owners.
These two mates are favourable among the Auto market which the PFC does not support Auto cars (well nissan anyway).
Running both of these lets you bend IGN timing to your hearts content and make the ecu think your AFM is drunk to get some more power in and out.
All in all not a bad comprimise if you dont have a choice or cant go for a good supported stand alone (ie: auto ecu etc).
Cheap, cost effective and works well. You will be limited by this setup so be careful.
Enter SATAN. The bad boy of the ECU market that dominates all.
The Motec is a complete stand alone ECU for any car, any setup, any scenario.
You can choose inputs, outputs, engine control, batch or sequential fire, anti lag, fuel or spark cut, complete map control and 3rd dimension selection.
There is nothing the Motec cannot do. It is mainly used for rally and race cars but can be used on a street car. This ECU costs a fortune and is the ultimate stand alone ecu.
I would not recommend it for a mild skyline but you certainly can use it, it will just cost a lot. There are lots of local tuners so that shouldnt be an issue and everything is supported.
I do not have much to say about the Autronic as I know very little about it. As far as I know its a stand alone mutli-purpose ECU to suit most cars.
It has good local technical support and a range of tuners as well. I believe you have options of AFM or Map sensor and it also enters the 3rd dimension letting you tune in 3d via Throttle Position Sensor (maybe others too?).
The Autronic has things like antilag, launch control and a few other cool features so its not a plain vanilla ECU. This is aimed at race/competition cars.
I know jack shit about Haltech
The Wold 3d has been one of the older generation ECUs for generic cars.
It has been locally supported and developed in australia for some time now. I think you get the choice for AFM or MAP so thats a bonus.
The newer Wold 3d v500 has extensive support for most of the comon features and extra stuff most users need, they say it even rivals motec/autronic.
I dont see any issues with running a wold 3d, but like most ECU's you need to find a range of good local tuners to sort it out for you.
Running a remapped ECU is cool and cost effective. It lets you tune the stock ecu (providing its supported and doesnt cost a bomb) and gives you good bang per buck.
You can support almost anything within reason, such as larger AFMS, bigger injectors etc and still retain factory control.
The main issue with remaps is you cant adjust jack shit once its remapped and most tunes are expensive each time as they do a complete burn of the chip.
Ie; its not like they can just change timing via a hand controller each time. The user also has no control or real time interaction with the tune.
I know jack shit about Link
So there you have it, a quick glance over some of the more common ECU's and what they have to offer.
If you disagree with any of these comments, please send me a pm on SAU or email me (firstname.lastname@example.org
) and let me know.
I am happy to correct any incorrect info, mistakes or bad opinions. If you have an ECU you think should be on this list let me know also.
What's the Apexi D1 Limited Edition Hand Controller?
There was a limited build run of approx 100 units of the D1 Limited Edition D1 style hand controller. This was a gold stylish hand controller and worked just the same as the normal hand controller units. I Suspect it was a plain run of X001 hand controller to suit most models as there was only 100 made. From all that I can see its simply a gold case - I have no working photos of the unit in action etc.
Special Thanks to Skylineowners for the picture.
If you have any working pictures or a copy of "ETC, VERSION" from this hand controller please send it through to my email address
I have the older PowerFC that did not come with a hand controller can I buy a new hand controller separate and use that?
You may be able to depending on the version of the ECU and hand controller. If the version between the ECU and Hand Controller is different the Hand Controller will boot up the Apexi logo and freeze. Take this as a precaution as a few people have experienced this. If you experience the hand controller freeze problem click here to get some help on it.
My Hand Controller freezes at the Apexi Logo. Why???
Pay attention to the version matching and you can't go wrong. Your local supplier can order the correct hand controller for you. If you can't find a supplier can source the older styler and newer style hand controller (N001 and X001) for you new at a new price. If you are after a 2nd hand unit you can try Yahoo Auctions, Ebay or even Jap Parts at
What's the new Apexi PFC EL Hand Controller and what is different?
Apexi have released a new version of the PowerFC Hand controller which is the Apexi EL PFC Hand controller.
The part no is 415-A030 and this is the new "multi-version" PFC Hand controller.
The new version is confirmed to suit all powerfc models including Pro, Djetro, AP Engineering etc (only exclusion is Toyota JXZ100 Auto)
It essentially looks like FCC3 with a different screen model. The original units had LCD (Liquid crystal display) vs EL (Organic LED).
The EL / Organic LED screen's are found in the Apexi AVCR, SAFC and VAFC controller so it should look the same as this.
The official version is FCC4 on the hand controller
Knock bar chart display in 4 channel view (prev only display as bar chart in 1 channel view)
English only text in ETC, FUNCTION SELECT (previously japanese characters)
Here is the official product - thanks Duncan from Skylines Australia