derrack

*** Edit the following problem turned out to be the Q31 spot on the board. Common easy fix. I would like to thank Dave at Moates.net for sorting it out.***

I just purchased a p72 ecu, the long rectangle style, and it seems to be missing something in the Q21 spot. A part seems to have been fried and removed. Do i need this part of the ecu? Can anyone enlighten me to what number is on the piece missing? There is also a capacitor above the chip that is damaged. Anyone know the replacement? C14 ,capacitor by the missing piece, has some wear on a top corner should I replace that too? Any tips or suggestions on how to get this squared away would be great. I was going to use this to drop in a h23a vtec into my 93 prelude.

motoxxxman

wow. I don't even know what to say. ok, maybe I do:
-that's officially the worst solder job I've ever seen on an ecu
-the chips are fake, they are knockoff brands printed as name brand SST, and they fail very quickly, often instantly
-I don't remember what goes in that q21 spot
-personally, I'd throw that ecu right in the trash. or use it for spare parts.

derrack

Well then, looks like I was ripped off pretty bad. Could I have someone use the extra board to turn a p28 into a p72 functionality wise? If anyone knows of someone who I should go to to not get screwed that would be great. I was hoping to have a p72 but budget wise it looks like I'll probably have to downgrade to a p28.

motoxxxman

sorry to hear that. I always hate giving people bad news.
the extra board in the p72 is actually for the knock sensor, not IAB function. and honestly, the knock sensor function becomes pretty useless with anything besides a stock gsr motor, so there's really no need for it. if you want p72 for IAB functionality, that's an easy thing to add to the ecu, and the below companies should be able to encorporate it for you. or if you plan to go with hondata, you don't even need to have IAB function added, you can use alternate outputs to control the IAB's. Or you can connect the IAB diaphragm directly to a manifold port and have them open according to manifold pressure instead of rpm. It's not the ideal way to operate them, but it works quite well because they will be closed for low throttle allowing good gas mileage and torque, and open at high throttle for the better power in higher rpms where you usually only use high throttle anyway.
If you wanted p72 strictly for knock function, scrap the idea and just go for a p28.

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derrack

It is what it is. So the knock sensor wont do anything on the H23A Vtec? That was the reason I went that direction. I was thinking of having a P75 converted with this units knock board since I have it. I thought having the knock sensor would add added security if I ever went with a mild boost in the future. I also wanted the IAB functionality but read I could use an RPM controlled switch that would have to be adjusted manually for that if I went with a P28.

motoxxxman

well, like I said, IAB functionality can easily be added to a p28 type ecu, and the above companies i linked can do it. or yes you can use a manual rpm dependent switch. or the other option I mentioned above.

in my experience, and in many others' experience, the knock board does not work well at all on anything except the stock engine that the knock board was designed for. it can trigger false knock on rare occasions, but more often the issue is that it simply does not register actual knock. every motor has a different knock frequency. even just changing the internals and/or changing bore or stroke can alter the frequency. and then there's the issue of the sensor itsself. not all honda engines use the same knock sensor, and the original knock sensor and knock board are designed to work together, not mixed and matched.

A lot of tuning companies for hondas are actually removing knock function in their software for these very reasons because so many people have attempted to tune their own motors relying on knock readings and blew their motors up because it detonated and didn't register any knock in the ecu, and then attempted to blame the software company.

Spunkster

The knock boards can be configured for the different sized engines so that it detects properly, you just have to set the jumpers correctly on the knock board.

motoxxxman

good to know, though I wonder if anyone knows how to actually configure them lol

B and B

iTrader: (3)

Spunkster knows.

B and B

iTrader: (3)

Is that spattering around the joints exascerbated by not cleaning the board with Brake Kleen before soldering, as I read to do?
Seems like I ran into that once..(I've only worked on a couple)
Wanting to order a capacitor/Ecu restoration kit and replace the old components in mine as preventive maintainance.

derrack

It looks like really cheap flux, I would suspect that plus iron temp being the cause of the splattering.

motoxxxman

rosin core silver bearing solder is king.
like the guy above said, looks like crap flux, crap application of flux, too much iron heat, shaky hands, and more. I suspect the desoldering job was also garbage, especially from the other pics posted where components have not been added. I think it's safe to assume there a lot of damage to the tracing on that board