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Hacking up Honda's ECU
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PostPosted: Thu Dec 07, 2017 10:10 pm 
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Joined: Sat Dec 02, 2017 4:30 pm
Posts: 2
Hey everyone,

I'm new around here and new to tuning these Honda ECU's, so I wanted to stop in and ask some questions.

Here's a little bit about my build. I've got a '92 Prelude with an F22A1 (P12) in it that I use strictly for road racing. We race it in one of the cheap-o car race series you've probably heard of :D. We bought a junkyard engine to have as a backup, but we decided to rebuild it and put it in the car. We aren't going crazy, keeping the stock bore and compression ratio. We had the block and head checked for flatness, honed it, new bearings all around, new pistons, timing belt, etc. We did the balance shaft delete kit from Kaizenspeed and I just got the cam back from Delta after getting the 272 grind on it. Since this is for road racing only there is no cat with a 2.25" exhaust straight back.

When we bought the car it came with some random stuff, one of which being a P28. I started doing some homework and I see P28's are good to chip. I took the cover off this one and low and behold it already had the chip kit in it. Along with the 2 sockets it has some other mods. The RP17 resister has been removed, which I believe makes it into a manual gearbox which is good. The J1 resister has been removed and replaced with a 0 ohm wire, and the J12 resister has been removed. While inspecting it I also see that the Q31 transistor is shot, but from my homework it sounds like that shouldn't be a big deal. It has what looks to be a real SST 27SF512 chip in it. All in all, it looks like it's in pretty good shape.

I haven't been able to find a 100% clear answer on this one: Is there anything extra involved with using the P28 aside from the tune? If that's the case all I need to do is burn a chip that will run the F22, and plug the P28 in?

Now for some more tuning questions. I've downloaded Crome and plan to use that, and a BURN2 is on the way.

I downloaded a stock F22 rom so I have the spark and fuel maps. My plan was to modify that rom, but then I realized it probably makes more sense to start with a P28 rom and tweak it for the F22. I got the P28 rom and started tweaking it for the F22. I disabled VTEC and copied in the F22 spark and fuel maps.

I know it will take some significant changes to the fuel map and idle speed to get it to idle and run right, but am I on the right track?

I've got an AEM Wideband that'll be going in that I'll be doing the tuning with, but at this point I'm mostly concerned with getting it running with the P28.

That's it for now, I'll have some more questions after you guys tell whether I'm crazy or not!

What do you guys think?


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PostPosted: Mon Dec 11, 2017 11:29 pm 
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Joined: Sat Dec 02, 2017 4:30 pm
Posts: 2
Any wisdom here any more, or am I the only one still tuning these engines!


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PostPosted: Tue Dec 12, 2017 3:22 pm 
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Joined: Fri Aug 20, 2004 6:33 pm
Posts: 2231
Location: chicago burbs
Most of the truly good tuners on here have either moved on to other vehicles, created businesses around these skills or simply moved on in general. There are a few of us that still happily answer questions, but we don't have a lot of time to check the forums either. (life happens)
anyway, you're questions:

it sounds like you are on the right track. The ECU sounds like it's ready for your maps. (as far as your description of things)

http://www.xenocron.com/bins/index.php? ... /H-Series&
checkout the first one. :)

some thoughts:
Q31 being shot - classic sign that your IAT and EVAP purge plugs are swapped. Also typical due to this that your IAT is now toast. (IAT - intake air temperature)
Don't worry about Q31, worry that your ECU is not reading the IAT.


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