vafc on obd2
02-18-2004, 04:56 PM
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vafc on obd2
unlike hondata you can run vafc on obd2 correct? but somone mentioned you will see better tuning and more power w/ obd1 conversion, is this all true and if so why? i searched!
03-09-2004, 01:07 PM
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Re: vafc on obd2 (SleepnCiViC)
Qouted from MichaelDelaney (team-inetgra)
again, the advantage of an OBD1 with only 1 O2 sensor and no cat function monitoring for emissions is that it has less error codes associated with emissions and so you won't trip the check engine light off the second back O2 sensor. Secondly OBD1 is easier to re-program and cheaper.
No-one I know has publicly analysed the fuel tables (fuel map program commands) or ignition timing tables (ignition timing map program commands) comparing OBD1 to OBD2, including the Derek at Hondata. There's no proof that these are "more aggressive" in the OBD1 version.
There was an old late 90's Import DETuner magazine article that compared an OBD2 GSR to an OBD1 GSR dyno after a DC 4-2-1 header install (with i/e already on) and they reported a lower gain in the OBD2 car sparking the rumor (which they never analysed on a follow up article) that OBD1 must be better. No proof was ever shown by looking at the programs of each,... there was no tuning done on either car, and we don't know the engine temp or ambient temp fluctuations in either car. The "evidence" was suspect in the first place.
So OBD2 does not DE-TUNE. The only DE-TUNING happening is DISinfo you get from the magazines.
You need to tune the car's torque curve into the desired shape you want (powerband location) in terms of air:fuel ratio across the entire rpm range regardless of whether you are OBD2 or OBD1.
A VAFC is a good basic piggyback tuning tool. Most people get it with their cam upgrade because more aggressive cams require the VTEC to be moved higher and the nonVTEC & VTEC fuel tables need to be shifted and adjusted (leaned down) with a higher VTEC switchover.
It's not as good as a full re-program, since it only affects fuel delivery in 16 rpm points (low resolution).
How does the VAFC work?: The fuel injectors are tricked into opening for a longer or shorter time by altering the Intake Manifold Absolute Pressure voltage (a measure of how much air flow you have) going to the ECU. The ECU is tricked into thinking you have either a lot more or a lot less air flow than you actually have. It has a limited range for increasing fuel flow effects (+14% on the MAP voltage) and in most N/A setups, it's used to lean down fuel, since the stock ECU programs are usually too rich as it is.
All of the fuel tuning is done on the dyno with a wideband O2 sensor placed in your exhaust to get air:fuel ratios at each rpm. Do not copy other people's settings..they don't apply to your car. So you have to know how to work it. It's NOT a plug and play.
The fuel controller on the VAFC can be used by people with stock cams but it's not going to give you dramatic gains. I usually recommend that people hold off getting one until after they've made the very serious commitment of doing their cam/valvespring upgrading and possibly headporting. Most people who buy these usually don't have a clue as to how they work or how to tune them. I suggest you go to the http://www.apexi-usa.com website and read the documentation on it first to familiarize yourself with the product and the instructions before buying it...you can get in over your head fast, if you aren't familiar with tuning.
again, the advantage of an OBD1 with only 1 O2 sensor and no cat function monitoring for emissions is that it has less error codes associated with emissions and so you won't trip the check engine light off the second back O2 sensor. Secondly OBD1 is easier to re-program and cheaper.
No-one I know has publicly analysed the fuel tables (fuel map program commands) or ignition timing tables (ignition timing map program commands) comparing OBD1 to OBD2, including the Derek at Hondata. There's no proof that these are "more aggressive" in the OBD1 version.
There was an old late 90's Import DETuner magazine article that compared an OBD2 GSR to an OBD1 GSR dyno after a DC 4-2-1 header install (with i/e already on) and they reported a lower gain in the OBD2 car sparking the rumor (which they never analysed on a follow up article) that OBD1 must be better. No proof was ever shown by looking at the programs of each,... there was no tuning done on either car, and we don't know the engine temp or ambient temp fluctuations in either car. The "evidence" was suspect in the first place.
So OBD2 does not DE-TUNE. The only DE-TUNING happening is DISinfo you get from the magazines.
You need to tune the car's torque curve into the desired shape you want (powerband location) in terms of air:fuel ratio across the entire rpm range regardless of whether you are OBD2 or OBD1.
A VAFC is a good basic piggyback tuning tool. Most people get it with their cam upgrade because more aggressive cams require the VTEC to be moved higher and the nonVTEC & VTEC fuel tables need to be shifted and adjusted (leaned down) with a higher VTEC switchover.
It's not as good as a full re-program, since it only affects fuel delivery in 16 rpm points (low resolution).
How does the VAFC work?: The fuel injectors are tricked into opening for a longer or shorter time by altering the Intake Manifold Absolute Pressure voltage (a measure of how much air flow you have) going to the ECU. The ECU is tricked into thinking you have either a lot more or a lot less air flow than you actually have. It has a limited range for increasing fuel flow effects (+14% on the MAP voltage) and in most N/A setups, it's used to lean down fuel, since the stock ECU programs are usually too rich as it is.
All of the fuel tuning is done on the dyno with a wideband O2 sensor placed in your exhaust to get air:fuel ratios at each rpm. Do not copy other people's settings..they don't apply to your car. So you have to know how to work it. It's NOT a plug and play.
The fuel controller on the VAFC can be used by people with stock cams but it's not going to give you dramatic gains. I usually recommend that people hold off getting one until after they've made the very serious commitment of doing their cam/valvespring upgrading and possibly headporting. Most people who buy these usually don't have a clue as to how they work or how to tune them. I suggest you go to the http://www.apexi-usa.com website and read the documentation on it first to familiarize yourself with the product and the instructions before buying it...you can get in over your head fast, if you aren't familiar with tuning.
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