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Old 7th October 2009, 16:48   #1
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Default Advantages of OBD 2 over OBD 1

Hey guys,

I just wanted to know if there are any functional advantages of OBD2 over OBD1.

Or is it just a change of interface?

Does it have a better processor?
Higher resolution of the fuel map?

Or was it introduced just to prevent chipping?
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Old 8th October 2009, 07:11   #2
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OBD2 can be chipped as well
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Old 8th October 2009, 10:27   #3
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The capabilities of the ECU have little bearing on what kind of OBD port is on it. Of course, there are a few prerequisites about what all need to be reported over OBD2, but the resolution of the fuel maps or the capabilities of the processor don't really matter.

OBD2, like many technologies of late, was introduced for emissions reasons.
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Old 8th October 2009, 10:51   #4
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OBD1 and 2 both are diagnostics interfaces, and have nothing to do with emissions etc.
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Old 8th October 2009, 11:08   #5
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On the contrary, they do. OBD2 was formulated so that it would be possible to monitor quite a lot more data than OBD1 so that a car can be more thoroughly tested and calibrated for emissions compliance.
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Old 8th October 2009, 14:41   #6
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Quote:
Originally Posted by ImmortalZ View Post
On the contrary, they do. OBD2 was formulated so that it would be possible to monitor quite a lot more data than OBD1 ...
True. What could be done in 2001 with a twisted pair of wires was much more than what one could do in 1984 with the same pair of wires. Also, an engine in 2001 had many more parameters that could be read than in 1984.

Quote:
Originally Posted by ImmortalZ View Post
car can be more thoroughly tested and calibrated for emissions compliance.
So I can go to GM, Ford or Tata service center and they can give me an emission certificate just by connecting the diag tool over OBD2, or reduce the emissions coming out of my car?

The motive for making OBD2 mandatory was
a. making emissions related data available on call and
b. preventing an escape route for manufacturers by citing inability to measure or inability to present measurements.

The *reason* for introducing OBD2 was quite simple - faster / higher volume data communications - similar to USB replacing RS232 in computers.

Quote:
Originally Posted by Sprucegoose View Post
... any functional advantages of OBD2 over OBD1. ...
No functional advantages for an end-user of a car

Quote:
Originally Posted by Sprucegoose View Post
... Or is it just a change of interface? ...
Yes - faster communications at hardware level (serial comm), more data elements at the application layer

Quote:
Originally Posted by Sprucegoose View Post
... Does it have a better processor? Higher resolution of the fuel map?...
Not in the context. OBDx is not associated with a 'processor' or 'resolution of fuel map'. OBD is a set of specifications:
1. At the hardware level, it is just the definition of voltages, baud rates and signal duty cycles (there are 5 variants)
2. At the logical level (data content) it specifies what data must be made available by an ECU to a connected diagnostics equipment

OBD is only an interface definition/implementation, like an iPod interface. The processor power used on either side of the OBD2 interface, as well as what is done with the data generated/presented, is left to the interpretation of the manufacturers of the ECU and diagnostics equipment. For example, OBD does not specify/limit whether the data is to be used for closed loop parametric calibration, or for the simple vicarious pleasure of looking at various engine parameters presented on one's OBD-connected carputer (nothing wrong in doing that, right?).
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Old 8th October 2009, 14:42   #7
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hmmmm...
So essentially the differnce between OBD 1 & 2 is like the difference between USB and Firewire?

I was reading somewhere that some people are using p28 [I think] ECUs.
So there are P28 OBD 1 & P28 OBD 2 ECUs?

Last edited by Sprucegoose : 8th October 2009 at 14:43.
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Old 8th October 2009, 14:48   #8
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No OBD2 P28s. Only OBD1, though you have USDM (through-hole soldered) and JDM (surface mount) versions.
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Old 8th October 2009, 14:54   #9
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P28 is Honda-specific. It is definitely OBD, not sure if OBD2 is implemented. Other engine makes use ECUs from Bosch, Siemens, Delphi, Denso etc. (FIAT uses Magneti Marelli most of the time). There are very few generic ECUs, almost all are engine specific - so model numbers are not important / public domain information.

Yes, it is possible for an ECU to have OBD and OBD2 version - quite likely the OBD2 version would have replaced the OBD version.

Usually manufacturers mate a certain version of an ECU to an engine, but don't talk of upgrading the ECU alone for such purposes as OBD to OBD2 change. If there is a change in ECU for an engine, it is quite likely many other things would have changed in the engine warranting an ECU change.
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Old 8th October 2009, 16:10   #10
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1> So is it possible to use another ECU?
Like if, hypothetically, i get an RD ECU, I will have to get one that is designed for my OHC [or for a certain set of similar engines.]

2> I've read alot about people switching over from OBD2 ECUs to chipped OBD1 ECUs

3> So by switching from on OBD2 to an OBD1 ECU, the only thing one is doing is restricting the amount of information that you can check?
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Old 8th October 2009, 16:36   #11
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1. Yes. Of course, unless one wants to be stranded in the middle of nowhere, one should test the combination out on a dynamometer. One would also need intimate knowledge of the engine, and the corresponding values of the parameters used by the 'driveability' map

2. The reason wouldn't have had anything to do with diagnostics, but someone's knowledge of modifiability of the older gen ECU

3. Not so simple. Quite likely one would fall back to an older control method / strategy, apart from lesser diag data
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Old 8th October 2009, 18:12   #12
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I think the thread title should be changed to Advantages of Honda OBD2 over Honda OBD1 ECUs.

Sprucegoose: Between OBD1 and OBD2 ECUs, there are a few differences, least of which is the number of things able to be logged. Please keep in mind that some of them are there even between USDM, EUDM and JDM ECUs. With OBD2 came a few more things like a secondary O2 sensor (Not on all though), knock sensors (present on few OBD1 engines/ECUs as well, and not on all OBD2 engines/ECUs). Now USDM OBD1 ECUs have provisions for ELD, which JDM OBD1 ECUs do not. So it's more about the differences between different ECUs rather than about OBD2 vis-a-vis OBD1 features.

Suffice to say that when you move over to Honda OBD1 ecus, you will not be stuck with less things to log or less diagnostic information. You move over to OBD1 ECUs for the exact reason that you've been asking about - Chipping and infinite moddability.

As for the RD ECU, I do not know if they have a harness converter or not, but if they don't you will have to say bye-bye to your original stock engine harness as it will be cut and spliced according to RD's specs. The Honda ECUs, OTOH, can be connected using a wiring harness converter as most of the stuff is common externally between the 2 standards, only with different wiring schemes. Do not know if RD has different spec ECUs for different manufacturers, will let Bangalore boys answer that one.
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Old 10th October 2009, 00:47   #13
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@pranavt - yes you have it - OBD1 was the emission regulation at electronic control of the engine & its emissions. OBD 2 has basically taken it to the next level.

Ex1: most OBD1 applications have 2 O2 sensors (one for each bank) - this will confirm if the engine ran at stoichimetric conditions. Now, the 3 way cat is highly dependant upon the engine runing at stoic. The OBD2 has 4 O2 sensors (for a V config) where there are 2 more O2 sensors after the cat. This monitors the Oxygen level downstream of the cat. Several tests would have been run during development to determine how much O2 is absorbed/released in the cat to convert CO to CO2 and NOx to N2 etc.
The Civic is a Port injected engine and so during knock, fuel is cut and ignition is retarded until knock is eminiated - this is monitored cycle by cycle

The best way to bypass some of this is a piggy back ECU that takes in the inputs from these sensors and tells the ECM what you want it to know.

Cheers.
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Old 10th October 2009, 09:11   #14
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Quote:
Originally Posted by DerAlte View Post
So I can go to GM, Ford or Tata service center and they can give me an emission certificate just by connecting the diag tool over OBD2, or reduce the emissions coming out of my car?

The motive for making OBD2 mandatory was
a. making emissions related data available on call and
b. preventing an escape route for manufacturers by citing inability to measure or inability to present measurements.
Quote:
Emission testing
In the United States, many states now use OBD-II testing instead of tailpipe testing in OBD-II compliant vehicles (1996 and newer). Since OBD-II stores trouble codes for emissions equipment, the testing computer can query the vehicle's onboard computer and verify there are no emission related trouble codes and that the vehicle is in compliance with emission standards for the model year it was made.
On-board diagnostics - Wikipedia, the free encyclopedia
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Old 10th October 2009, 14:35   #15
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Quote:
Originally Posted by 7600 View Post
The best way to bypass some of this is a piggy back ECU that takes in the inputs from these sensors and tells the ECM what you want it to know.

Cheers.
Piggybacks on Honda OBD1 ECUs are useless, as the ECUs can be chipped and made to behave exactly like full-blown standalones with datalogging, remapping et al
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