OBD2 ECU options

J

jlucas

New member
After reading the GCR, it would seem that an OBD1 conversion for OBD2 cars is not possible. Is this the correct interpetation? What's the best way to modify an OBD2 ECU if OBD1 conversion is not possible?

Jeremy Lucas
 
Most OBD-2 are not flash programmable until the 2002-3 model year for honda products. But the obd-2 ecus from earlier 96+ models can have new chip with different program installed into them (be chipped). They have surface mount boards, however, so this is much more costly than earlier obd-1 and pre-obd ecus. Alternative to keep legal is to install an obd-1 board into the original obd-2 box and then run conversion harness/plugs to make it work.

-dave w
 
This isn't completely academic because I may end up running one of these cars but (a) there is no provision in the IT rules to allow the wiring harness to be changed or conversion wiring to be installed, and (B) all changes have to be inside of the black box. Yeah, the rule is dumb the way it is written but we need to remember the fine points. That said, who makes re-mapped/re-mappable chips for the '96+ SOHC vtec?

Kirk
 
Originally posted by davew:
Alternative to keep legal is to install an obd-1 board into the original obd-2 box and then run conversion harness/plugs to make it work.
Click to expand...

Are you sure this is legal (specifically the conversion harness)? From my reading of the rules it seemed to be a gray area bordering more to not being legal. If it is legal it would make my life a lot easier as I'm currently looking at having to swap OBD connectors as well as the board (OBD2 connectors onto an OBD1 board into the stock OBD2 box connecting to the stock OBD2 harness). And yes the connectors are different on Hondas/Acuras between OBD 1 & 2.

Once the OBD1 is in, Hondata seems like the best choice but they (and everyone else) won't touch OBD2.

Jeremy


[This message has been edited by jlucas (edited August 26, 2003).]
 
Originally posted by jlucas:
If it is legal it would make my life a lot easier as I'm currently looking at having to swap OBD connectors as well as the board (OBD2 connectors onto an OBD1 board into the stock OBD2 box connecting to the stock OBD2 harness).
Click to expand...


aaahhhh yes. i was talking with someone about this not too long ago once the 96-98 Civic EX was classed into ITA.

take a look around hondata's site more. They make exactly what you're talking about. They have an obd1 board with obd2 plugs soldered on the end. They do the "wiring conversion" right by the connectors. Since so many people were buying conversion harnesses and then obd1 ecu's hondata decided to get in on the action and just make an obd1 board with obd2 connectors. just just plug it in to your obd2 wired car and you're good to go with custom mapping!!

from hondata's site:
"Hondata has OBDI P28 ECUs modified with OBDII connectors. These plug straight into an OBDII vehicle with no adapter harness necessary. Available with OBDII A (96-97) and OBDII B (98-00) connectors."


http://www.hondata.com/news.html (scroll down just a little bit)

and for those that want to abide by every letter of the rules you can just take the board out and put it in your obd2 case. They are the same size.

hope that helped some!!

s
 
Thanks, actually that does help. I don't want to use a P28 but I'll probably make one with a P72 OBD1 board.

Jeremy Lucas
 
Originally posted by jlucas:
Thanks, actually that does help. I don't want to use a P28 but I'll probably make one with a P72 OBD1 board.

Jeremy Lucas
Click to expand...

no problem. how come you want to use the P72? The only advantage it has is it has a knock sensor (it can also control the secondary butterflies on a b18c1 intake manifold but i assume you're using this for a civic ex anyways) which I wouldn't assume you'd need on a race motor. just curious.

edit: the only other problem I can see with rules is that hondata stage 2,3,4 and the S200 have an external box that plugs into the ECU. The s100 system is all internal inside the ecu but I don't know if hondata will make the obd1 board with obdII plugs and put the s100 in also. I don't see why they couldn't but I just haven't seen that configuration on there site. It's not any different putting the s100 on the obdII plugged p28 board than a regular obd1 board so i don't see why not. Would the external hondata "blue box" be illegal under the rules?

s



[This message has been edited by stevel (edited August 28, 2003).]
 
why P72? Because it's for a Prelude, not a Civic and the Lude has 2 stage intake manifold like the GSR.

And yes, for Hondata you could only use the S100.

Jeremy
 
My mechanic, Todd Marcucci, has already been in contact Hondata about putting their OBD1 P28 inside our Prelude ECU. Another option we have is the AEM EMS. My mechanic has a Prelude AEM EMS and will be looking at what it will take to stuff it inside the stock ECU box in a few weeks. It is a little more expensive than the Hondata but it might be worth it.

------------------
David Rierson
#53 ITS Honda Prelude
Texas Region
 
Originally posted by jlucas:
why P72? Because it's for a Prelude, not a Civic and the Lude has 2 stage intake manifold like the GSR.
Jeremy
Click to expand...

Well, I was waiting for you to say that! I don't know how much trouble this p72 obdII-I board is gonna be (hondata might even make it for you, dunno) but one thing I was thinking is you could still use the p28 and make an rpm activated switch to trigger the secondaries. Say if a b18c1 engine was fully prepped to ITS rules, the stock activation of the secondary butterflies might no longer be optimal. I think stock rpm activation of the secondary butterflies for a b18c1 is 5750rpm or so. Well, if you've got a balanced bottom end, decked head, overbore pistons, and such you're probably making a good amount more hp/tq than a stock engine is and using more fuel also. So, if you took the time to dyno tune the engine and played with the rpm activation of the butterflies you might be able to gain some tq/hp somewhere in the middle of the power band. I would think the stock rpm activation for a fully rules prepped engine would no longer be optimal. Just my .02. Hope that helps somebody or puts an idea in someone else's head!

What class are you running a Prelude in??

s
 
Originally posted by TypeSH:
My mechanic, Todd Marcucci, has already been in contact Hondata about putting their OBD1 P28 inside our Prelude ECU. Another option we have is the AEM EMS.
Click to expand...

I already checked into the AEM and was told by AEM and a guy who uses one in a drag car that there no way the AEM guts were going to fit in a stock ECU case. It would be much more tunable than a Hondata S100.

What are you going to do about the manifold secondaries if you use the P28?

Jeremy Lucas


[This message has been edited by jlucas (edited August 30, 2003).]
 
I think the secondaries are open by default. I tested this by unplugging the vacuum line and they stayed open all the time. By keeping them open all the time you would be losing power down low under VTEC but I doubt you would be spending much time at those low RPMs.
 
Originally posted by TypeSH:
I think the secondaries are open by default. I tested this by unplugging the vacuum line and they stayed open all the time. By keeping them open all the time you would be losing power down low under VTEC but I doubt you would be spending much time at those low RPMs.
Click to expand...

Hmmm, can't remember correctly but I think the secondaries are ground activated meaning they need +12V to stay closed. SO if the signal isn't hooked up they're open by default. Which makes sense so if somethig goes wrong they're open which is better.

It would be cool to be able to change the activation rpm of them and see if it gives any benefit on the dyno. Don't know if it's in the rules though.

s
 
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