Introduction to ECU Tuning

What is a chipped ecu?
A chipped ecu is a modified factory engine control unit (ECU) which is setup to read a 28 pin eprom chip which contains custom fuel/timing maps along with other settings. offers chipped ecus for those who don’t have a obd1 ecu or for those whom do not want to experience any downtime by mailing in their ecu to be chipped. customizes ecus specifically for your vehicle.

What is ecu chipping?:
Ecu chipping is the modification of a factory engine control unit (ECU) to read a custom programed 28 pin eprom chip with custom fuel & timing maps for your vehicle’s application along with custom options such as revlimit, vtec activation points etc. allows you to mail in your obd1 ecu for chipping/socketing services.
For more information on our ecu chipping services, please click here.

What Honda ecus are chipable?:
Only a few select type of obd1 92-95 honda/acura engine computers are chipable to use with popular engine management softwares.
USDM Vtec: P28, P72, P61 JDM Vtec: p30, p72, p08, p27, pr3, p91
USDM Non-Vtec: P75, PR4, P05, P06
Some obd0 honda/acura ecus are chipable but these ecus are not compatible with nicer eprom editors, hence we do not support obd0 ecus.
Obd1 ecus will plug & play into 92-95 honda/acuras, while pre-92 & 96-01 vehicles will require a ecu plug conversion harness to use the ecu (sold separately).

How do I know if I need a conversion harness to run a obd1 ecu?:
Any Honda/Acura vehicle newer then 95 requires a obd2 to obd1 conversion harness.
Most Honda/acura vehicles older then 92 require obd0 to obd1 conversion harness.

What is a obd2 to obd1 conversion harness?:
A conversion harness is a jumper harness which plugs and plays into an obd2 vehicle and allows you to run an obd1 ecu.

What is a obd0 to obd1 conversion harness?:
A conversion harness is a jumper harness which plugs into an obd0 vehicle and allows you to run an obd1 ecu. Obd0 to obd1 conversions require you to run a obd1 distributor along with a 4 wire oxygen sensor if you plan on using narrow band oxygen sensor feedback which not needed if your car is properly tuned.

Picture of a conversion harness:
conversionharness Introduction to ECU Tuning

What can a chipped ecu do for me?:
A chipped ecu will allow you to make the most horsepower you can possibly make on your vehicle via custom fuel maps, ignition timing etc. ecus come with basemaps specifically for the specifications you provide.

What program do I ask for when I have my ecu chipped or I order a chipped ecu?: provides you with the best basemap possible for your vehicle/motor.
The order form will ask you for specs/details on your vehicle which will allow for the best basemap possible to be put onto your ecu.
If you are unsure about a setting such as vtec activation point, leave it blank so that we can provide you with the best setting for your setup.

* General intro into tuning systems/hardware:

What is Hondata, eCtune, Crome, Uberdata, Neptune etc?:
These systems are different eprom editors. They all have the same concept of editing fuel & timing values along with other settings to properly tune a obd1 honda ecu for your motor setup. All of these eprom editors edit binary data which is programmed onto a 28 pin eprom chip. This is why socketed/chipped obd1 ecus are compatible with all of these systems.
Hondata is the only eprom system which makes you run a hardware unit to be able to use a hondata eprom chip i.e. the hondata s100/s200 units.

What is Hondata S300 & Neptune RTP?:
These systems are different eprom editors, however these systems use computer hardware instead of an eprom chip or romulator. These systems use a single usb cable to allow you to program them without the use of a chip being programmed. They also allow you to datalog without the use of a datalogging cable. We HIGHLY recommend the use of one of these systems!

- Tuning Systems:
* Apexi AFC, Greddy Emanage units: These units are piggy back systems which alter the signals being sent to your factory ecu. You should prevent from using a piggy back system.
* eCtune, Neptune, Crome, Hondata, Uberdata: These systems are all obd1 eprom editors. They work off the factory ecu. Some systems have more options then others.
* Aem EMS, Motec: These systems are standalone systems which operate on their own ecu. They have a lot more features then a system based on a factory ecu.
* There are a lot more systems on the market but these are the most popular.
~ So which system should you run?
We always recommend you choose a system which your tuner recommends for your application & needs.

What is the difference between all of these eprom editing systems?:
Pricing & Options are the most common differences.
So, which eprom editor or tuning solution should you go with?
Use the one which your tuner wants to use & has the features you need.

Screenshot of crome (Hondata/Uberdata look simular):
cromess Introduction to ECU Tuning

How does an eprom editor or tuning software work?:
Most systems such as hondata, eCtune, crome, uberdata, neptune are based of the factory honda ecu. These programs allow you to edit the factory values in a socketed/chipped obd1 ecu.

There are several different things which you can modify which will allow you to properly tune your car using an obd1 honda eprom editor.

A brief run through: Low Cam = Non Vtec / High Cam = Vtec

There are high & low cam fuel & ignition maps on a vtec ecu. As you can imagin a non-vtec ecu does not have a high cam map.

Now each map can be edited cell by cell via rpm & load. For example, most motors idle around 21″ of vaccum which is about 288 millibars. These figures are measures of pressure. Using the low cam fuel map, you can add or remove fuel to the idle via editing the proper rpm & vaccum collums. Using the low cam & high cam fuel maps a vehicle can be properly tuned via load/rpm using a wideband oxygen sensor by monitoring the air/fuel ratios per load cell etc.

The low cam & high cam ignition timing maps are maps which work the same way as the fuel maps except for the fact that you are editing ignition timing values per load & rpm instead of fuel values.

What is a basemap?:
A basemap is an ecu program that is specifically modified for your vehicle & its modifications. A basemap contains fuel & ignition timing values along with other important settings such as revlimit etc. uses basemaps which are only from actual vehicles which have been tuned by using a wideband oxygen sensor and a dynojet. This is what separates from other modified ecu distributors.

What is an eprom chip programmer/burner?:
An eprom burner is a device which is used to program binary data to a 28 pin eprom chip which is then installed into an obd1 ecu for a vehicle to run off of.

What is a romulator?:
A romulator is a device which allows you to emulate a 28 pin eprom chip being in your ecu. (The romulator is actually connected to a pc which sends it data to run the ecu off of) This unit basically pretends to be an eprom chip in the ecu. This allows you to make changes without having to remove the eprom chip while tuning. Once your final binary program is done being edited via crome, hondata, uberdata etc, you or your tuner would save the binary file to a eprom chip using a chip burner. You would then install the eprom into the obd1 ecu which would enable the vehicle to run off of the binary file just created or edited by you or your tuner.

What is datalogging / a datalogging cable?
A datalogging cable is a cable which is connected from your computer to your obd1 honda ecu. This cable allows you to use feedback from your ecu to log or view information which is live from your ecu. Using datalogging along with a wideband oxygen sensor and a good eprom editor will allow you or your tuner to view critical air/fuel information.

General obd1 ecu tuning equipment:
tuningequip Introduction to ECU Tuning

What is a wideband oxygen sensor?
A wideband oxygen sensor is a sensor which allows you to monitor parts air to fuel. Most people have the preconception that a basic autometer air/fuel guage using the stock oxygen sensor in their vehicle will give them all the information they need about being in a lean or rich condition. This information is false, the factory narrowband oxygen sensor will not provide you with an accurate reading because the oxygen sensor is a narrowband sensor which does not have a wide enough of a range to accurately sense air/fuel mixtures needed to properly tune a vehicle. The purchase of a wideband oxygen sensor is not required due to the fact that almost every tuner provides one with his services etc.

What is a 3 bar or 2.5 bar map sensor or an aftermarket map sensor used for?:
An aftermarket map sensor is used for forced induction vehicles which are to be tuned over 11 psi of manifold pressure. The factory Honda map sensor only supports up to 11 psi of map pressure.

Can I run my vehicle on a basemap & not worry about it?:
No matter how good the basemap, every forced induction or heavily built motor should be dyno & or street tuned by an experienced tuner to ensure engine safety.

Why piggybacks (vafc, emanage) “suck” by pgmfi:
Piggy Back controllers allow stock ECUs to do things that they normally can’t do, like run larger injectors or deal with boost. Remember that piggyback controllers work by altering sensor signals before they get to the ECU.
Most of the time, the primary signal being messed with is the Map Sensor. This is critically important in a Speed Density car. The Map Sensor is used by the ECU to guess how much air is going into the car, and therefore how much fuel to supply in order to match airflow. When you “lean” out a car with an AFC, you are simply decreasing the Map Sensor signal – the ECU responds to the decrease in manifold pressure by supplying less fuel. When you “richen” a car with an AFC, you are simply increasing the Map Sensor signal – the ECU responds to the increase in manifold pressure by supplying more fuel.
The change in fueling happens for a reason: if you look at a fuel table, Map Sensor values correspond with columns. When you increase or decrease the signal from the Map Sensor, you are simply making the ECU use a different column than it originally would have used. (see Understanding Maps if you need some help understanding reading Fuel and Ign tables)
But wait, isn’t the Map Sensor used for determining ignition requirements too? When you “lean” out a car with a Piggy Back, you also in all likelyhood advanced timing. When you “richen” a car with a Piggy Back, you also in all likelyhood retarded timing. Look at trends horizontally (as MAP changes) in an ignition table, and you will see why this happens. This helps explain why so many boosted cars running on the “AFC hack” have issues due to excessive ignition advance.
The bottom line: Piggy Back Controllers suck because you cannot independently adjust fuel and ignition. Any changes to fueling will produce a change in ignition too, and often this is undesirable.

What is an fmu?:
A Fuel Management Unit (FMU) is a special rising rate fuel pressure regulator placed in the fuel return line of the fuel injection system. This is a very common approach to handling the increased fuel demand required by turbo kits and supercharger kits. It does work. It will make the injectors flow more fuel than their rating. These are used in addition to the factory or aftermarket fuel pressure regulator and only have an affect under boost.
FMUS are rated by the ratio of fuel pressure to boost pressure. For instance, a 10:1 FMU will give you 100psi fuel pressure at 10 psi boost pressure.

Why you shouldn’t run an fmu/missing link?:
Fmu’s are considered a “hack” they overload your injectors with high fuel pressure to compensate for boost pressure. This is the improper solution for fuel management on a forced induction vehicle. Most stock engine computers do not retard timing under boost hence causing dangerous engine conditions. A missing link simply stops the manifold pressure sensor from seeing positive pressure, hence preventing a check engine light.

Where do I find a local tuner?:
check on forums, or just use Google.

A lot of people do not understand the importance of tuning a vehicle. Most people assume tuning is to make horsepower, what they do not realize is tuning is extremely important due to the fact that an untuned engine will eventually fail without proper tuning by an experienced tuner.

- Before you have your vehicle tuned check list:
* Oxygen Sensor Bung: You must have a oxygen sensor bung which is accessable & installed in a proper location to where a good air/fuel pickup can be achieved. The oxygen sensor bung MUST have clean threads & be clear of any welds which may stop a larger wideband oxygen sensor from being installed into the bung.
* Fuel Pump & Injectors: You must have the proper size & type injectors & fuel pump for your vehicle setup. Please consult with your tuner to ensure you have the proper combination.
* Spark Plugs: Proper spark plugs & spare spark plugs for your application.
Please consult with your tuner if you are unsure as to what spark plugs to run.
Most all motor applications call for NGK BKR7E-N-11 [NGK-1283]
Most sub 400 whp forced induction applications call for NGK R5671A-7 [NGK-4091].
Most sub 400whp forced induction applications should use plugs gapped to around .028.
* Check engine light: Resolve all check engine codes before you have your vehicle tuned.
* Charge piping: Charge pipe couplings must be secure to prevent pipes from blowing off during tuning & causing delays.
* Engine compression (No more then 20psi between cylinders.)
8:1-8.5:1 c/r = 150-170 psi per cylinder 8.5:1-9.5:1 c/r = 170-210 psi per cylinder
9.5:1-11:1 c/r = 210-275 psi per cylinder 11:1+ c/r = 250+ per cylinder
* Electrical issues: Please resolve all electrical issues before tuning.
* Brakes, Suspension, Tires: All of these components are extremely important, especially if your going to have your vehicle street tuned. Please make sure they are all in good condition.
* Proper octane fuel for your application: Please inform your tuner of what fuel you are running. You should run the highest octane which is widely available in your area such as 93 octane. Try to prevent having your vehicle tuned with gas which has been sitting in your vehicle for more than 20-30 days.
* Forced Induction vehicles should invest into a pcv catch can system such as the endyne kit.

- What is required to have your vehicle tuned:
1. A vehicle/motor/setup in good mechanical condition.
2. A chipped/socketed obd1 ecu & a obd conversion harness if your vehicle requires one.
(Consult with your tuner to provide you with a chipped ecu or ecu chipping services)
3. The proper sized & resistence injectors for your application. (Ask your tuner)
92-00 Civic/Integra vehicles require Saturated HIGH RESISTANCE injectors (11-14 ohm)
LOW RESISTANCE injectors maybe used in 92-00 Civic/Integras using a resistor box.
240cc = 180-190whp 310cc = 200-220whp 370cc = 220-280whp
440cc = 280-330whp 550cc = 330whp-380whp 660cc = 380whp-425whp
720cc = 425whp-475whp 880cc = 475whp-525whp 1000cc = 525whp-600whp
4. The proper sized fuel pump. (Most street applications: Walbro 255lph fuel pump).
5. A couple of sets of spark plugs. (NGK BKR7E-N-11 for most applications under 400 whp.) Consult your tuner for his recommendation. Your spark plugs should be gapped properly (.018-.030 depending on the application)
5. Optional: Fuel pressure regulator & Guage
6. Optional: Cam Gears for dyno tuning purposes.

- What is Air Fuel Ratio & Ignition Timing:
Air/Fuel ratio is the ratio of air to fuel. Ignition timing is the point at which spark is produced to create combustion. 25-30% of air/fuel mixture energy actually becomes “work” aka thrust. The remaining 70-75% becomes exhaust. Ignition timing & A/F ratio are both used to control the heat which an engine produces during combustion. For example, in most cases forced induction motors require a richer air fuel mixture of 12 parts fuel to 1 part air at wide open throttle using pump gas. Where as naturally aspirated motors usually run 13 parts fuel to 1 part air at wide open throttle. Running a richer air fuel mixture on a forced induction motor, helps absorb the heat which is produced due to the higher charge density.

- What is detonation:
Detonation occurs in the combustion process when the advancing flame front, which is pressurizing and heating the unburned mixture ahead of it, does so at such a rate that unburned fuel in that zone achieves its auto-ignition temperature before the arrival of the actual flame front. The result is that the unburned mixture combusts “spontaneously” and over the entire zone where the auto-ignition temperature has been achieved. The apparent flame speed in this zone is many orders of magnitude faster than that in conventional combustion initiated by a normal flame front, with the result that the local rise of pressure and temperature is significantly sharp. This produces the characteristic “knocking” or “pinking” sound, and the local mechanical devastation that this can produce on piston crown or cylinder head can be considerable. Actually, “knocking” is the correct terminology for what is a really a detonation behavior over a small portion of the combustion charge. A true detonation process would be one occurring over the entire compressed charge. However, because detonation in this strictly defined sense does not take place in the spark-ignition engine, the words “knocking” and “detonation” are used interchangeably in the literature, without loss of meaning, to describe the effects just discussed.

- What causes detonation?:
Detonation occurs when several conditions / factors inside the combustion chamber exist at the same time. Increased compression, high temperatures, lean fuel/air mixture, advanced ignition timing, and lower octane fuels are all factors that PROMOTE detonation conditions. The good news is that, because there are so many factors in play, you can always find a way to eliminate detonation if it exists.

- What is cam timing:
Cam timing is the rotating position of your camshaft(s). This position maybe altered using an adjustable cam sprocket. Using cam timing adjustments a tuner can usually change an engine’s working environment & create more horsepower.

- What is a wideband oxygen sensor:
A wideband oxygen sensor is a sensor which allows you to monitor parts air to fuel. Most people have the preconception that a basic autometer air/fuel guage using the stock oxygen sensor in their vehicle will give them all the information they need about being in a lean or rich condition. This information is false, the factory narrowband oxygen sensor will not provide you with an accurate reading because the oxygen sensor is a narrowband sensor which does not have a wide enough of a range to accurately sense air/fuel mixtures needed to properly tune a vehicle. The purchase of a wideband oxygen sensor is not required due to the fact that almost every tuner provides one with his services etc.

- What is dyno & street tuning:
Dyno tuning is the use of a dynamometer to measure wheel horse power and torque. Using a dyno to tune a vehicle is very important. A dyno provides a controlled platform for a tuner to make adjustments & see the repercussions to those adjustments. This will allow your tuner to make the safest horsepower/torque with your vehicle.

Street tuning is the tuning of a vehicle while being driven on the street. Street tuning is a good idea after dyno tuning to ensure that a vehicle’s tune is spot on in real world conditions (air temperatures, vehicle load etc.). Street tuning is also important to ensure that partial throttle tuning is correct.

In most cases both Dyno & Street tuning methods of tuning are necessary to achieve the best possible results. Street tuning is extremely important because it simulates real world conditions. I.E. Temperature, Wind, Engine Load etc. By street tuning a vehicle, you can monitor real world drive-ability, engine conditions & general fuel economy. The reason dyno tuning is needed on-top of street tuning is to monitor wheel horse & torque power and torque so that you can achieve maximum horsepower results in a controlled environment using ignition & cam timing adjustments.


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Posted in Honda, Tunning, Tunning

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