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Engine Management FAQ (Please Read Before Posting!)

Engine Management eCtune , Crome , AFC , FMU , Zdyne , Hondata , EMS , TE , Uberdata Anything to control your fuel, spark needs!

Engine Management FAQ (Please Read Before Posting!)

Old 01-08-2004, 02:17 PM
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Join Date: Apr 2003
Posts: 2,260
Default Engine Management FAQ (Please Read Before Posting!)

Keep all your posts on topic in this forum. "noob bashing" without tech content included should be kept to the GD.


This Engine Management FAQ is a collection of literally frequently asked questions in this forum. I will try to answer the more popular questions, and keep this updated as new ideas, concepts, and technology appear.

If you feel a question should be listed here that is not or there is misinformation, please PM it to me, and I'll get it added/changed as soon as possible. This thread will remained locked as to not clutter it.


ROM Editor FAQ Threads

Uberdata Support (OBD1) - Current Version: 1.7 w/ Datalogging

TurboEDIT Support (OBD0) - Current Verison: 2.6.x

BRE (OBD0 VTEC) Support...Current Version 2.2.X

Commercial Editor Websites

Crome Website

eCtune Website

Neptune Website

Other Makes and Models Tuning Info

ECU Flash by Slo_crx1


General Questions

1-1) How much boost can I run with X motor and X turbo?
1-2) Which Engine Management should I use? ..FMU, AFC Hack, ECU Mod, what is the difference?
1-3) What is a CEL (Check Engine Light) and what do the different ones mean?

V/S-AFCs, AFCs in general (Air Fuel Computers/Controllers/Converters)

2-1) What is an AFC (how do they work, and what is thier purpose)?
2-2) What size injectors can be used with the "AFC Hack"?
2-3) I have heard using an AFC Advances your ignition timing, is this true?
2-4) What settings should I use for X size injectors with X amount of boost?
2-5) What is the maximum amount of boost I can run using the "AFC Hack"?
2-6) Will the "AFC Hack" in conjunction with my X size injectors effect my idle?
2-7) I can't find information to install on my OBD0 car. Where do the wires connect?

ECU Modification (DIY Standalone Systems)

3-1) What free software is available for my ECU?
3-2) Can my ECU be chipped?
3-3) What do I need to do to "chip" my ECU and burn ROMs?
3-4) Which ROM burner should I buy?
3-5) How much boost can I run on these DIY stand alone systems?
3-6) What is datalogging, and what do I need in order to accomplish this?

Misc. Reference Links (Outside Sites)
TurboEF9 is offline  
Old 01-08-2004, 02:21 PM
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Join Date: Apr 2003
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Default General Questions

1-1) How much boost can I run with X motor and X turbo?
This is a difficult question to accurately answer due to the number of factors that play a part in engine stability. From an engine management stand point, an OBD0 MAP sensor can read up to ~9.5psi, where as a OBD1/2 MAP sensor can read ~10.5psi. Other limitations include which engine management solution you are going to use, FMU at ~6psi, AFC Hack at ~10psi, standalone limit based on MAP sensor support. The biggest, and most difficult part of judging how much boost you can run on a specific motor lies in the current state of your motor. How many miles? How hard has it been beaten? The motor itself.. are the rods strong? Please refer these questions to the Hybrid/Tech section of the website.

1-2) Which Engine Management should I use? ..FMU, AFC Hack, ECU Mod, what is the difference?
A popular question indeed. First, there are a few questions that should be answered. How much boost can I run on my vehicle? How much boost do I *want* to run on my vehicle? What is my budget? How serious am I about tuning and modifying (do I just want a little more power, or do I want a mad phat race machine)? Once there questions are answered, I believe you'll be able to accurately choose which one of the following DIY management solutions will best fit your needs.

FMU (Fuel Management Unit) - These devices are also known as rising rate fuel pressure regulators. Thier function is increase fuel pressure as manifold pressure increases. This allows for more fuel to be pushed through the injector opening during the same pulse duration. How does this work as a management solution? As manifold pressure increases, so does the amount of air pushed into the combustion chambers, this air needs to be compensated with fuel, otherwise, a lean condition is created, and engine damage will occur. The ratio of fuel increase to air increase is normally dictated by an interchangeable "disc" or "plate" in the FMU. Others maintain a static ratio. These devices are normally used in conjuction with checkvalves. These are small, on way, air valves (available at Pet Shops that sell aquarium accessories) that are connected in-line with the vacuum line of your vehicles MAP sensor. Honda ECUs are not designed to "deal" with positive manifold pressure, so when the ECU sees this, it will throw a check engine light. The check valves are used to "bleed off" the positive pressure (several check valves may be needed depending on your maximum boost setting), and the FMU is used to compensate fuel. Stock injectors are normally used on these low boost, high fuel pressure setups. This setup is normally good for ~6psi.

AFC Hack - The AFC hack refers to a MAP sensor input scaling device (AFC) "hacking" the signal to your ECU and fooling it into thinking that it is not seeing positive manifold pressure. These are normally small electronic devices connected in-line with your ECU. Some more elaborate devices, such as A'pexi's V/S-AFC, SMC, and so forth, accomplish the same thing, but have the feature of being able to tune a specific percentage of "cut" at designated RPM increments. How does this work as a management solution? As positive manifold pressure builds, the MAP sensor sends a voltage signal to the ECU. This signal, if above ~3.1volts on a stock Honda MAP sensor, will cause the ECU to "shutdown" and go into limp mode, rendering your vehicle inoperable until it is turned off and restarted. The AFC intercepts this signal and scales it by a user-defined amount. This scaling allows positive manifold pressure to build while keeping the ECU happy. Fuel compensation for this setup is done by installing larger injectors. These higher flowing injectors allow more fuel to flow through during the same pulse duration to compensate for MAP signal scaling (which decreases fuel flow). No fuel pressure regulator is needed. No upgraded fuel pump should be required. This setup is normally god for ~10psi.

ECU Mod (Standalone) - ECU modification is quickly becoming one of the more widely used management solutions. This is due to the abundance of great, FREE, software applications out there. ECU modification beings with removing the chip (EEPROM) that contains the software program that runs your vehicle. In this chip, the key to your entire vehicle lies. Everything from Fuel and Ignition tables, Rev Limits, Launch Control, Boost Management and more can be edited or added to this program code! How does this work and a management solution? There are several different approaches to dealing with the positive manifold pressure situation. One has been to write code into the ECU program that acts as an AFC, scaling the MAP sensor voltage by a static percent. Another has been to rewrite the fuel and ignition routines of the ECU program to redirect to expanded maps in the ROM. All of these methods are functional and work well, telling the ECU how to deal with boost, rather than making it think it doesn't see it. Commercial or DIY, ECU modification in conjunction with larger injectors is a benefitial way to manage boost. These setups are good for the maximum manifold pressure read by your MAP sensor (stock Honda between ~9.5psi - ~10.5psi).

1-3) What is a CEL (Check Engine Light) and what do the different ones mean?
A CEL or Check Engine Light is a diagnostic indicator triggered by the ECU to denate abnormal operation in the ECU or one of the vehicles many sensors. Diagnosing a problem should always start by checking for codes. OBD0 ECUs have a small LED on the ECU itself that blinks a certain number of times to indicate which problem is occuring. OBD1 and OBD2 requires you to use a jumper to make the actual Check Engine Light blink on the console gauges of your dashboard. Use the following link to Hybrid Garage to match the blinking code to it's repsective problem.


This is the most complete set of codes I have found available free on the Internet.
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Old 01-08-2004, 02:25 PM
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Default V/S-AFCs, AFCs in general (Air Fuel Computers/Controllers/Converters)

2-1) What is an AFC (how do they work, and what is thier purpose)?
Refer to question 1-2 in General.

2-2) What size injectors can be used with the "AFC Hack"?
Injector sizing is key to the AFC hack working properly. This is not because of fuel compensation demands, really, it is more of "how far" you must scale based on your maximum boost setting. To elaborate: As positive manifold pressure builds the MAP sensor signal voltage sent to the ECU builds.

Once ~3.1volts is reached, the ECU shuts down, and goes into "limp mode", rendering the vehicle practially in driveable until it is turned off and restarted. The use of the AFC here is key because depending on how much scale the signal back by direct effects how much pressure is takes to bring the modified MAP sensor voltage up to what the ECU thinks is 3.1v. How does this effect injector sizing?

If your injectors are not large enough, and your maximum boost setting is too high, you'll create a leaning condition or a check engine light.
I have not seen a definative scale as to the corolation of injector size vs maximum boost. If anyone has and solid, proven information on this I would low to post it. Typically, 450cc injectors are used with the hack at 8-10psi reliably. Others have boasted 12psi on the hack without a check engine light.

Link with good info about RX7 Injectors:

2-3) I have heard using an AFC Advances your ignition timing, is this true?
Yes. This is very true. How when the AFC is not connected to your distributor? It all lies in the fundamental basis of how the AFC works. Visualize this, You have a grid of say 15 x 17. This is your OBD0 (10x20 for OBD1) ignition table. As we know, the AFC scales down the MAP sensor input to the ECU, thus, shrinking the resolution of the ignition map to fit more points in the same space. Now, if we look at what happends when we are in vacuum, this part of the table is squeezed into the left most half of the ignition map. If you have ever looked at an ignition table before, you'll notice that this is the most radically advanced section of the table!! This is how your AFC decreases fuel (same thing happends on the fuel table, and to increase, it scales everything to the right part of the table)!! To compensate for this advance in timing, some of used a BTM (Boost Timing Master), retarded their static ignition timing at the distributor, or even chipped thier ECU and modified the ignition table itself.

2-4) What settings should I use for X size injectors with X amount of boost?
This is one of the most misunderstood concepts about using the AFC hack. Lets examine each part to determine your correct settings. To begin, please read question 2-2 before continuing. Now that you understand a little bit about injector sizing with an AFC, we can talk about settings. If you decide to use something other than 450cc injectors, you may want to start with lower boost settings (at the wastegate) and build up from there, keeping the same fuel compensation settings in the AFC.

This will give you the upper limit for the current injector size.
As for obtaining those settings there are a couple of things to explain. Fuel flow rate difference.

This is the difference in flow based on the stock injector flow rate. For a Honda, 240cc injectors are stock. If you increase to 450cc injectors, your flow rate difference is a 46% increase. How do we figure that? Simple math: percent_of_difference = ((240 / new_injector_size) - 1) * 100
Second, an AFC does not control fuel injector pulse duration. This means we cannot compensate for injector latency in the fuel table for our larger injectors. Injector latency describes the scientific characteristic of how long it takes the injector to physically open. The larger the injector, the higher the latency. Since AFCs do not control the pulse duration directly, we compensate with a fixed percentage subtraction, otherwise, we would run lean in lower RPMs, even though our fuel flow rate has been adjusted based on the exact percent difference. The scale for common injector sizes used is 5% for 440-450cc, 4%, 390cc, 3% for 310cc.. then subtract 1 percent per 500 RPM increase. This will give us are starting point. For a boosted application, running stoichiometric is dangerous because of the high volume of air. To "play it safe", you want to run a bit on the stoich/rich side, so we increase fuel flow by 1% per 1000 rpms, trying not to top out a 5% overall increase. Why 5%? ..because your fuel maps are still increasing in pulse duration. So you're increasing pulse duration, and percentage
of flow rate at the same time. You'll get rich, very quickly. If you have VTEC, enrich by 1% more over VTEC VTEC crossover.
So, lets apply everything we've learned, and come up with base settings for 450cc injectors.

1) 240/450 = 0.53
2) 0.53 - 1 = -0.46
3) -0.46 * 100 = -46

So we have a 46% difference, we add our 5% for injector latency compensation, which leaves us with these settings:

1000 - 40%
1500 - 40%
2000 - 39%
3000 - 38%
4000 - 37%
--- VTEC set to 4400 RPMs ---
5000 - 35%
6000 - 34%
7000 - 34%
8000 - 34%

Application of these ideals will find your AFC Hack producing the smooth, safe, reliable power.

2-5) What is the maximum amount of boost I can run using the "AFC Hack"?
Due to the scaling of MAP sensor signal, and maximum read boost amount by the MAP sensor, ~10psi is obtainable. Some of boast numbers reaching ~12psi. Other limitations apply, please refer to 2-2 for more information.

2-6) Will the "AFC Hack" in conjunction with my X size injectors effect my idle?
Yes. However, if the proper settings are applied, and a reliable AFC is used, your idle should be smooth as stock. Refer to 2-4 for information on how to calculate settings.

2-7) I can't find information to install on my car. Where do the wires connect?
Instructions for newer cars are available in the manual downloadable from http://www.pgmfi.org/~jparker/host/A...AFC_Manual.pdf

Or another helpful thread for installing your AFC is located here:

(As posted by mechanic_b)

Apex-I AFC VTEC controller
for PM6 (88-91 civic/crx) or PG7 (88-89 1.6L integra) ecu application only

V-AFC VTEC controller -------> ECU PIN location
Red & Orange wire splice/connect to A15 (yellow/black)
Green wire RPM signal splice/connect to B15 (white1)
Pink wire VTEC signal output to VTEC solenoid (green/yellow)
Purple wire VTEC signal input not used on PM6 ecu
Blue wire VTM signal not used on PM6 ecu
Gray wire Throttle signal splice/connect to C7 (red/blue wire)
Yellow wire Pressure signal output cut/connect to C11 ECU side harness
Si/Hf = white1 , DX = orange
White wire Pressure signal input cut/connect to C11 ENGINE side harness
Si/Hf = white1 , DX = orange
Black wire Ground splice/connect to A16 (brown/black wire)Engine side harness
Brown wire Ground splice/connect to A16 (brown/black wire)has to be connected closer to the ECU
TurboEF9 is offline  
Old 01-08-2004, 02:33 PM
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Posts: 2,260
Default ECU Modification (DIY Standalone Systems)

3-1) What free software is available for my ECU?
http://www.PGMFI.org (Official home of the hacked Honda ECU) has brought together some of the best minds in ECU hacking and coding. From this great place, free DIY engine management solutions have come about, and are running vehicles around the globe. Some of the free software applications available are.

Uberdata by Blake Warner - http://www.ecimulti.org/uberdata (Honda OBD1)
TurboEDIT by Jason Parker - http://www.TurboEDIT.org (Honda OBD0)
ECUControl by Nick Mailloux - http://www.ECUControl.com (Honda Datalogging OBD0 & OBD1)
Crome by John Cui - http://www.radicalperformance.com/download/ (Honda OBD1)
ZControl by Mike Robichaud - http://www.ZControl.net (for Nissans)

3-2) Can my ECU be chipped?
As far as the more common Honda ECUs:
OBD0: 90-91 PM6, JDM PM7, PR3, PW0, 90-91 PR4

What about 88-89 ECUs? Well, there are three ways of going about this. Get an adapter for your ROM burner, or a burner itself that will burn 40-pin 8051 MCUs, or, you can make a simple "daughter board" for your external EEPROM from parts from RadioShack. These schematics tell show you exactly how to make them. Users have had good results with them! (Added option #3 in WIKI link)


OBD1: Any of them (some more work than others, some have more potential than others)
OBD2/2.5: None.

(If I missed important ECUs let me know, or if I got osmething wrong, let me know)

3-3) What do I need to do to "chip" my ECU and burn ROMs?
In general, you need a "chippable ECU" (refer to 3-2), a ROM burner (refer to 3-4), EEPROMs (27C256 UV erasable? 29C256 electroniclly erasable) and Engine Management Software (refer to 3-1).

Honda OBD0 (External EEPROM) Chipping Process: (Supplies: Soldering iron, Desoldering braid (or other means), 28-pin ZIF or Lo-Profile Socket)
1) Using a soldering iron/desoldering iron of your choice, locate the external EEPROM, and desolder all 28 pins from the PCB. CAREFUL: There is protective gel over the chips and needs to be melted otherwise, you'll tear a trace under the chip. If this does happen, patch with a jumper wire.
2) Insert ZIF or Lo-Profile socket, and solder socket in. ...all done.

Honda OBD1 Chipping Process:
1. Desolder all holes for the components.
2. Solder in a 28 pin socket. (Empty footprint)
3. Solder in the 74HC373. (Empty footprint)
4. Solder a 1.1K ohm resistor into R54 location marked in white lettering (not needed on P72 USDM GSR) (Note: 1K - 10K resistors seem to work ok. This is a simple pull up/pulldown resistor. 1K resistors seem to work well with ROM emulators that have trouble with 10k resistors)
5. Solder in two 0.1uF ceramic disc capacitors into C51 and C52.
6. Solder in J1. This jumper can activated by utilizing an unused resistor lead or extra section of spare wire.
7. Insert the 28 pin DIP PROM in the proper orientation and start the car.

Notes: Caution: If you plug in an EPROM or EEPROM backwards it will overheat and erase or damage the device. If you are getting an error that was not there with the stock ECU, write the appropriate stock .bin file to a blank chip and install in your ECU. If there is still an error, there may be a soldering problem. Cut J1 to return the ECU to stock.
(Information by Fabrik8, from PGMFI.org FAQ)

3-4) Which ROM burner should I buy?
This choice is up to you. There are a lot of affordable options out there. Some are limited by the different EEPROMs they can burn, others are limited by ease of use. Below are links to these different products.

Willem - http://www.willem.org (find them on Ebay)
Transtronics (Pocket ProgrammerII) - http://www.xtronics.com/memory/EPROM.htm
Batronix (EEPROMer) - http://www.batronix.com/electronic/c...eprommer.shtml

Willem Burner (Dual Power/Enhanced) How-To Thread

3-5) How much boost can I run on these DIY stand alone systems?
Maximum boost is limited not by the tuning software, but by the MAP sensor currently in play. All applications that allow tuning of the fuel and timing maps, theoretically, can support larger 2 and a 3bar MAP sensors, but the degree of difficulty in tuning becomes the deciding factor. Some of the DIY management applications have 2 and 3bar MAP scaling features built in, some do not. Consult the individual application's site for futher information (refer to 3-1 for a list of applications).

3-6) What is datalogging, and what do I need in order to accomplish this?
Datalogging is the real-time capture of a vehicle's sensor information for later analysis. The use of datalogging to performance tune a vehicle, be it naturually aspirated or force inducted, has been a vital tool for many years. Several different commercial applications natively allow for the collection of this data. Hondata, Motec and Zdyne (ZDYNE does not offer daalogging) to name a few, have this feature. Support for datalogging is currently available is a few of the DIY Engine Management solutions available for download.
ECUControl, TurboEDIT, Uberdata, Crome, and ZControl all support datalogging at different stages for thier respective ECU Generations. All, however, use virtually the same setup to accomplish this.
A TTL to RS232 converter board is nessisary to convert the ECUs stock communications protocol into a standard protocol that our PCs (and laptops) can utilize. A link to the MAX233A (the morepopular unit, available for $23) is in the Misc Links section of this documents. Simple soldering skills are required to assemble the unit (clear, color instructions are included) and pinout instructions for Honda ECUs are available on the ECUControl website under "How to mod my ECU" ( http://www.ECUControl.com ).
TurboEF9 is offline  
Old 01-08-2004, 04:17 PM
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Thread Starter
Join Date: Apr 2003
Posts: 2,260
Default Misc. Reference Links (Outside Sites)

* How to make your own set of DET Cans for Knock Monitoring

* ECU Pinouts - PLX Devices

* Bosch LSU4 Oxygen Sensors - VW Part# 021-906-262-B

* EEPROMs ($3.30 each! 29C256s):

* ZIF Sockets (P/N: A347-ND):

*MAX233A Serial Adapter for Datalogging from your ECU: http://www.compsys1.com/workbench/On...3_adapter.html

* Trailer Park AFC (100% functional) by Joseph Davis:

* OBD2 to OBD1 Conversion Harnesses (At time of post $7

* Injector List (massive compilation)


TurboEDIT Reference Links:
* How to make basemaps (v2.0.10+) -

* http://www.-------------/te
TurboEF9 is offline  
Old 06-21-2006, 07:12 AM
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Join Date: Jul 2003
Posts: 6,449
Default Re: Engine Management FAQ (Please Read Before Posting!)

DSM Information:


Originally Posted by boost_guy
If you have an eprom ecu(which is pretty rare for a dsm) there are a few options. You can learn hex and change the code yourself. There is a Yahoo group with all of the information you need: http://autos.groups.yahoo.com/group/dsm-ecu/

There is http://www.evilscribe.net/ which is a very basic rom editor, it's been the same for a few years, although the website claims they are working on upgrades.

There is dsmap http://home.meatchunks.com/%7Esmaug/dsmap/index.htm I've heard that it works very well.

http://home.earthlink.net/~grey2.0/ECUedit.html General info on dsm ecu's

Dsmlink is a good setup, but it's a bit pricey if you don't need all of features. Although the next version is going to be completely different and offer a lot of features that will make it worth the money.
Chris Harris is offline  
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