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Hacking up Honda's ECU
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PostPosted: Sat Nov 20, 2010 10:14 pm 
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My son and I rescued an '87 CRX Si from the crusher and got it running good as new. He's been driving it for seven months. He has a B16A at the machine shop, and we'll be dropping it into the CRX after Thanksgiving. It is up to me, the uber-nerd Dad, to do the electronics. I'm up to the challenge, having 31 years experience as an electronics tech, with the last 16 years as a test development engineer for circuit boards on automated test equipment. I am not afraid, but I'm no fool, either. I'm here for help. This post is my intro, but I'll post questions where they belong, and I hope to be posting something helpful to others, too.

First task - putting a socket under the stock Oki M38256AP-58 chip. I don't own a desoldering station, so this will be a "government job" at work. Ah, the things we do for love.


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PostPosted: Tue Dec 21, 2010 11:31 pm 
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Interesting project. I have swapped a 1989 Integra motor into a 1985 crx si. The challenges overlap to some degree since the crx wiring only supports electronic fuel injection. The B16 and Integra distributor signals require an add on harness.

I used the stock ECU plugs and added pins to pick up the additional distributor connections for the Integra motor and ran it through the fire wall to the distributor. I would suggest the same approach for the B16

My suggestion is to first get the car running, then explore chipping.

You have matched the ECU with the motor so duplication of the "stock" setup is possible with one significant exception. The B16A ECU needs a VSS (vehicle speed sensor) signal or it will not engage Vtec. The VSS signal comes from the speedometer in the dash. The 1985-1987 CRX si's do not have VSS equipped speedometers. All of the later 1988-1991 CRX do Have VSS equipped speedometers. The car will run but it will always be on the Low cam or non-vtec program in the ECU and Vtec will not engage. (88-91 speedometers will not fit in a 85-87 crx without major modification...I tried) VSS simply tells the ECU the car is moving versus stationary. VTEC will not engage if you have the clutch pressed and rev the motor. Vtec will engage if the car is in gear and moving. The way Honda set it up. My 85 si - Integra swap has the Check engine light on all the time. CEL error code = No VSS thrown by the Integra ECU. There is no performance penalty for no VSS since the motor in non-Vtec, just the aggravation of having the light on all the time. B16 no Vss = No Vtec

OK, fast forward a few months, pretend the car is now running and you want to get Vtec working.

options:

rpm switch outside the ecu..they work, you do get a power boost however it is short of max power possible if you could get the ECU to engage vtec

Find some way of incorporating VSS. I have heard the 1987 HF models had VSS but I have not verified it to be true. If true, locate a 1987 Hf model speedometer. If not, adapt a 88-91 speedo in some manner. or...if you are an electronics whiz, synthesize the necessary signal and get the stock ECU working at 100%

purchase an aftermarket ECU that is programmable and transcribe the base and VTEC fuel and ignition maps from the stock PR3 ECU into the aftermarket ECU. Specify the Vtec engagement RPM and you have essentially duplicated the Stock PR3 ECU without needing a VSS Signal.

Develop a chip for the Pr3 that ignores the VSS signal and triggers off RPM like the aftermarket ECU. If you can do this, you will be a true hero, worthy of praise.

Note, I have not mentioned performance beyond what is already in the stock PR3. Just duplicating the factory programming up to this point. That is the next level....and you may see why most choose a 88-91 car instead...easier.


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PostPosted: Tue Dec 21, 2010 11:47 pm 
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I've never done this, but I just looked at BRE and you can disable the VSS check like you can in Crome. That fixes your VTEC problem with minimal effort.


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PostPosted: Wed Dec 22, 2010 9:50 pm 
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sounds interesting. Does VTEC enguage with the VSS check disabled. If it does you only need to work on the wiring


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PostPosted: Wed Dec 22, 2010 10:29 pm 
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As far as i know it does. I think someone figured it out for race cars where you remove the speedometer,


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PostPosted: Wed Dec 22, 2010 11:38 pm 
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Awesome...disable VSS so VTEC will work in non VSS hondas. Still have to take on re-chipping the ECU which is a challenge if never done before.


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PostPosted: Wed Dec 22, 2010 11:53 pm 
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You can always send it out to have it chipped


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PostPosted: Thu Dec 23, 2010 10:15 am 
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Thanks for the responses!

I put a socket in the ECU and re-inserted the stock chip. It was a delicate operation, even with professional tools. I could not have done it cleanly at home using hand tools.

The engine is still at the machine shop, although I don’t know what the hold up is. That’s my son’s side of the project (and his money.) His body kit has arrived, but that doesn’t go on until after the engine swap.

I still need to get the VTEC sub-harness, the TTL-to-USB cable for data logging, some blank PROMS, and a VSS speedometer, although disabling VSS in BRE seems to be the obvious solution. I could build the harness and cable, but I don’t mind spending the money to save myself the hassle. I have a friend with a PROM burner, so that’s money saved.

I’ll post an update once we’ve started the actual swap, probably in late January. We still need to write our checklist, which I insist on having before cracking the first bolt. That’s the Air Force vet in me.


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PostPosted: Thu Dec 23, 2010 11:17 am 
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I have done 2 mini-me swaps on D15's, a B18c3 GSR swap, a ZC swap and a B16A Turbo swap/upgrade...and of course the Integra swap in an 85 crx. The turbo was the biggest challenge. Latest project is an 88hf with a body kit. Not sure where it will go yet.


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PostPosted: Tue Dec 28, 2010 10:01 pm 
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Thought of another way to get VSS in a 87 crx. 92 and up civics have electronic speedometers. Sending unit plugs into the older transmissions. 4 wires. One is the VSS signal. Means going without a working speedometer (cable unplugged), using a GPS speedometer or integrating an electronic speedometer out of a 92+ civic or Integra into the crx


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PostPosted: Tue Dec 28, 2010 11:35 pm 
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Location: Cincinnati, Ohio
the 84-87 hf speedometer was the only 84-87 civic that used a vss. You can use this gauge cluster. Or you can use the 86-89 integra cluster which also uses a vss. With the integra cluster you will have to drill your own holes to install the cluster.

As for wiring the vss. Use a speedo drive gear from any D-series transmission to eliminate the B-series tranny mounted vss. This is needed to retain the cable driven speedo. Then wire from the vss on the cluster to the ecu.

Or just delete vtec speed check. By doing this you are NOT deleting the VSS. You are just telling the ecu that it no longer needs to know how fast the car is moving to engage vtec. The ecu still knows the speed the car is moving but doesn't care about it when it comes to engaging vtec.


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PostPosted: Sun Jul 15, 2012 10:27 am 
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Wow. It's been almost 8 months. My son has poured most of his time and all of his money into this swap, but it is FINALLY running. However, it badly needs tuning. The AFR is totally out of whack, according to the WBO2. I'm guessing it's because of 320CC injectors with an aftermarket fuel rail, and a 70mm throttle body with aftermarket intake manifold. The ignition is suspect as well, because of new cams and adjustable timing gears. The 4-1 header and Flowmaster muffler (which muffles nothing) might also be a factor. With all the mods, the stock chip has no chance. The ECU is socketed, and I have the BRE software and TTL-to-USB adapter, however, I can collect data 'til the cows come home, and it's just a bunch of data. I have no idea what changes to make.

My son enlisted the help of a guy who has done this and other swaps. The dude knows his scheiB and rescued the project, but he can't help with the tuning. Bottom line, we need a pro. Anybody close to Roanoke, Virginia who can get the maximum potential out of this sick little ride?


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PostPosted: Mon Jul 16, 2012 1:54 pm 
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Location: Running in illogical circles
If you've collected data, email it to me and I'll take a crack at it.

theacidbeaver@gmail.com

You basically need to make sure the fuel pressure is set correctly at first, which, typically should be about 3BAR with the vacuum line pulled off. Cams that are larger than stock tend to pull less vacuum, which usually leads stock-based ECUs to run pig rich at idle and low RPMs.


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PostPosted: Tue Jul 17, 2012 11:05 pm 
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The mods you describe to the B16A (assume it is still a B16a and the project was not diverted to a b20) do not change the fuel requirements all that much. The stock ECU and programming was designed to run with 240 cc injectors (peak hold) Reverting to the 240cc injectors may bring the Air fuel ratio back in line (assuming you still have the stock 240 cc injectors) You are supplying 33% more fuel across the entire operating range with bigger injectors. Not surprised it is running rich.

Another option is to cut the fuel injector pulse duration across the entire operating range by 33% to simulate stock 240 cc injectors. tune from there

tune means adjust fuel pulse durations up or down to add / subtract fuel across the operating range for optimum performance

I determine optimum performance by a 12.5 air/fuel ratio under power via a wide band air fuel ratio meter.

It is trial and error. Drive, watch meter, tweak up or down, drive, watch meter, tweak up or down....


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PostPosted: Sat Jul 21, 2012 9:27 pm 
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Location: Cincinnati, Ohio
m184689 wrote:
I determine optimum performance by a 12.5 air/fuel ratio under power via a wide band air fuel ratio meter.


Wow 12.5 N/A THATS RICH :shock:


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