CRX HF '91 Federal ECU in '88 CA? - Fuelly Forums

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Old 01-17-2008, 02:03 PM   #1
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CRX HF '91 Federal ECU in '88 CA?

I picked up a 91 Federal HF ECU for $33 shipped off fleabay.

It looks like the engines are the same, injectors, oxygen sensor, camshaft etc. Do you think this alone would push the HP from 62 to 70?

I'm thinking this might push up the FE a little too. The federal has the 10% higher gearing than the CA, but I think around town this is not that big of an advantage. It's rated 10% higher around town 49 as compared to 45 for the 1988 CA model and the 88 is more than a hundred pounds lighter.

I just did a bunch more stuff to my car so I will need a couple of months to establish a baseline to compare to and then I'll try this.
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Old 01-17-2008, 03:08 PM   #2
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I don't know if you'll see that much of a jump, but I would expect you might see a jump of 5% or so. After you get your base established, give it a try. I would be very interested in your results.
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Old 01-17-2008, 06:40 PM   #3
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I didn't think there was much of a difference between the two ECUs and thought the main difference in EPA mileage was the transmissions.
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Old 01-18-2008, 01:16 PM   #4
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I didn't think there was much of a difference between the two ECUs and thought the main difference in EPA mileage was the transmissions.

This is why I'm going to do this test. I figure something must be different in the ECU for CA to require it's own version for emissions reasons. Pretty much all honda engines prior to this were lean burn engines running 5:1 in the tiny spark plug CVCC chamber and 18 - 20:1 in the combustion chamber. So the first gen crx hfs had lean burn and the VXs afterwords but not the CRX HF federal? I don't buy it. So I have to test it myself

I can't see how 10% higher gearing in the Federal version would help FE around town. I know I'd get better FE with a lower geared transmission around town with the CA version. I could keep it a lot closer to the sweet spot if 2nd gear was not 100% higher than first. I have to take it to 3K RPM in first to be at 1.5 starting out in second. 2.5 in second to hit 1.5 in third.

I figure for a $33 experiment it's worth trying anyway. I wanted to have a spare ECU anyway since 5 years from now if mine dies who knows how much it would cost to buy then when the car does not run and I needed one now.
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Old 01-18-2008, 07:21 PM   #5
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This is why I'm going to do this test. I figure something must be different in the ECU for CA to require it's own version for emissions reasons. Pretty much all honda engines prior to this were lean burn engines running 5:1 in the tiny spark plug CVCC chamber and 18 - 20:1 in the combustion chamber. So the first gen crx hfs had lean burn and the VXs afterwords but not the CRX HF federal? I don't buy it. So I have to test it myself

I can't see how 10% higher gearing in the Federal version would help FE around town. I know I'd get better FE with a lower geared transmission around town with the CA version. I could keep it a lot closer to the sweet spot if 2nd gear was not 100% higher than first. I have to take it to 3K RPM in first to be at 1.5 starting out in second. 2.5 in second to hit 1.5 in third.

I figure for a $33 experiment it's worth trying anyway. I wanted to have a spare ECU anyway since 5 years from now if mine dies who knows how much it would cost to buy then when the car does not run and I needed one now.
I'm interested in your results. If you gain anything, I guess I'll be hunting Ebay for a Federal ECU.
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Old 01-18-2008, 11:45 PM   #6
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When it comes to HP, I always read that ALL 1988-1991 HFs had 62HP. It was the 1988-1991 Civic STD (four speed model) that had 70HP.
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Old 01-21-2008, 01:42 PM   #7
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Well maybe this thread should be moved to general as this is not a scientific test but:

I got my wheels alligned only a tank ago but it doesn't seem to have made a difference. I just did it because the struts were replaced.

Anyways I put the Federal ECU in there and my first impression is impressed as compared to the stock one. It really seems to have lowered the RPMs for max torque, is this possible? You can floor it at 45 mph in 5th ~1500 rpm and it does not lug it accelerates. We'll see how the FE does with it. Also much smoother cold start in the morning. No pedal necessary
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Old 02-01-2008, 09:01 AM   #8
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I have to assume there are two different part numbers for your 2 different ECUs (Federal p/n and California p/n)? If so, could you please post the two numbers...and let us know which is which? I also have two HF ECUs, but they both have the same #s on them. Thanks a bunch.

**OH, and what's the update on your ECU swap?
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Old 02-01-2008, 09:29 AM   #9
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37820-PM8-L020 = CA version
37820-PM8-A030 = Federal Version

As for the difference in MPG it is a little too soon to tell. It seems a little better but I need a couple of full tanks to prove it. If someone was doing the federal transmission swap I think one of the federal ecus would be a must. It's lugs less at lower rpms than the CA version. As I said before, the federal also does much much better on cold starts than the CA. I think I need to retune my car with the new ecu as I've noticed a little pinging on short freeway onramps.

My car is also a little too kludged for this to be a valid test for anyone else though, with the HF body, Dx block, Hf head, CA transmission, and Federal ECU. I'm not going to take the federal out as it runs better with it than the CA. It would be worth a try for someone else to do a more scientific test with a stock CRX HF. ECUs are going for $25 or less on ebay. I think Gary Palmer was correct in guessing a 5% increase from my results so far. It did a little better and it's been really cross windy on my drives with some rain.
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Old 02-12-2008, 06:50 PM   #10
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Gone through another tank yet? I'm very curious about all of this. I'd also like to figure out once and for all whether or not there really are HP differences between the 1988 and 1991 model CRX HFs. Does anyone have any actual manufacturer's information on this?
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