OBDIIa to OBDI Conversion

"What is known to the tuning world from dyno plots and tuning is that the ECU on OBD2- equipped vehicles will eventually "detune" modifications that alter cam timing, ignition timing, and air/fuel delivery. This includes common breathing modifications (intake/header/exhaust and port work). What this means for the average tuner is that when you bolt on i/h/e, do manifold or head (port) work, change injectors or fuel pressure, or just about any other engine-related mod, the ECU will detect the change in emissions and alter the timing and fuel maps to compensate. This has been dyno proven on multiple occasions with multiple different performance mods. It also happens that this is especially true for air/fuel controllers (AFCs).

The purpose of the EPA-mandated OBD standard was to provide a means for which factory engine controls could diagnose engine control malfunctions and identify to the driver (and subsequently the repair shop) that there was a problem. The OBD2 standard, mandated for all 1996 and up vehicles, required that the OBD interface be standardized across all makes and models, as well as monitoring emissions components performance and proper operation. This means that for 1996 and newer vehicles with OBD2 that if you remove the catalytic converter or EGR valve that the ECU will eventually identify that these components are no longer working and flag a check engine light (CEL) and OBD2 code.

Aside from OBD2 (including original OBD vehicles), Honda ECUs (from the factory) run rich at WOT and in VTEC. This is likely for safety's sake, to help reduce the chance of detonation and allow for wide variances in climate, altitude, temperatures, etc. This can have a drastic effect on power. Honda ECUs also don't deal very well with bolt-on mods due to the MAP-based system of determining airflow into the engine. What this boils down to is that whether you are stock or modified, you are probably running too rich at WOT and in VTEC. At part throttle, it is debatable that an AFC gains much if anything at all- the engine is running "closed loop" (using the O2 sensor to trim the fuel mixture) and Hondas are tuned to run lean at part throttle for clean emissions."

Taken from: http://www.ntpog.org

Is this true? Can someone shed light on this topic. If true I might look into a P28 ECU and a conversion harness so I can chip my ECU.

-KB

its very true that most if not hondas run rich ( see puff of black smoke ) at WOT... reason for it is a comprimise though on the limit.

Ive have learnt so far that our ECU layout etc is alittle held back with various sensor's + whatnot - but im sure with the right piggyback most of these varibles can be bypassed/ rewritten to allow for more limts etc ?

Cheers for Info Man!

But I should have specified more. The real Question is. If OBDII ECU's adjust themselves accordingly to modifications(Negitivly By reducing EMissions), even with a AFC. WOuld it be wothwhile getting a OBDI Ecu first before attempting any dort of AFC or 'Chip'?

Basically I want A stock P28 ECU, and want to have it chipped to increase rev limit to 7800rpm, and lower VTEC engagment to 5000rpm. The rest can be done with a AFC.
It's just I can't do it on my OBDII one because they are too complex apparently.

Kb if ur going to chip the p28 for say something like uberdata or chrome etc, u have to use an odb1 ecu...

obd2 ecu's have what is known as a long term O2 fuel trim.
This means that over time, the ecu will try and target a a/f ratio of 14.7-1

The ECU logs this information when driving, and stores it in RAM , and thus compensates accordingly. This is why increasing air intake will have a possitive effect initially, until the ecu learns to compensate.
This is also why resetting ecu's tend to make a slight difference in short term.

Remember, ECU's have a constant 12V power supply constantly, hence RAM values are not lost easily.

This is also the case for OBD1, however, aftermarket ECU's such as ProECU or Hondata can alter the ECU to ignore these long term O2 trims, hence why its an advantage to go OBD1.

Hope this helps

Cheers pornstar and proECU exactly what I needed. Thnks :D

Kb jsut to add, any standalone ecu not jsut hondata or proecu will be able to get rid of those learnings.

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Originally Posted by pornstar

Kb jsut to add, any standalone ecu not jsut hondata or proecu will be able to get rid of those learnings.

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Well technically, proecu & hondata modify the code to remove the feature.

The other standalones just dont support that feature at all.

yeah tru

but if we wanna start nit picking..

you're being nit picky, im being concise.

In fact, let it be known, you often ask ME questions relating to Honda ECU's, so what are you really trying to achieve here?

Are you trying to publically undermind my knowledge of ECU's that ive been too willing to pass onto you, or have I misunderstood your last comment?

be nice to each other : )... So is a VAFC/VAFC2 able to make teh ECU ignore the "trim"?

wow, abit touchy dude? i ask because i like to test ecus, cant ever know too much right?

whats wrong with what i said? that other standalones also do the job? geez, chillax

if i run hondata or pro-ecu or a chip or anything and say i sell my car and i part it out and want to return it back to stock (cos i have sunk so much money into it and want to see some back), is this achievable?

definately achievable to return to stock form

Cheers for replys boys!

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Originally Posted by ProECU

definately achievable to return to stock form

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cool thanks.

juts get a P28/30 and an conversion loom, make your ECU tunab le and dont even bother with VACF, spend the mony on the dyno tune instead, you will get better results

Quote:

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Originally Posted by ECU-MAN

juts get a P28/30 and an conversion loom, make your ECU tunab le and dont even bother with VACF, spend the mony on the dyno tune instead, you will get better results

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I got a P28 and I'm waiting for ProECU to get his shit up and running :p

Should be way mad :thumbsup:

indeed it is...