Rugger53

Okay folks.

Need to know the correct part number for a 91 Civic Si ECU, 5 speed, multiport with programmable ignition. This is a D16Y7 motor. Looks like I'm going to need one for testing purposes and maybe continued operation for the time being.

Any help out there?

7rrivera7

iTrader: (1)

The following letters/numbers go after "37820-" (a question mark is where a non-important number is):

Non-VTEC:

P05-A0?
P05-A5? (must be converted to manual)

P06-A0?
P06-A5? (must be converted to manual)

VTEC:

P28-A0?
P28-A5? (must be converted to manual)

There are others but these are readily available. PM me if you need to acquire one

TomCat39

D16Y7 is the OBD2A 96-00 non vtec motor ECU P2E.

The 91 SI USDM originally came with a D16A6 OBD0 motor ECU PM6.

7rrivera7

iTrader: (1)

Post says "programmable ignition", only 90-91 PM6's can be chipped and there are hardly anymore OBD0 tuners left anyway. Best option is an OBD1 ECU.

Rugger53

Local parts house confirmed that it is a PM6 but I'm still getting two options there. By "programmable ignition" I mean the timing variables are controlled by the ECU. Initial timing has to be manually set at 16 degrees BTDC.

7rrivera7

iTrader: (1)

Then PM6 it is. Try to get a 90-91 in case you want to get it chipped.

TomCat39

There may be an issue running a D16Y7 on the D16A6 ecu. I think the D16A6 (SI motor) has a more aggressive non vtec cam and so the fuel maps will be geared for that performance.

The D16Y7 won't have that same setup as it was designed as the economy motor and will be expecting less fuel especially in the upper rpm range.

You may end up running the motor rich going this method.

Rugger53

This head was purchased off the parts hotline through someone I thought I could trust. That was important as this is my first Honda. Anyway, the casting # is P2A-5. Do hope the trust wasn't misplaced.

Rugger53

Did some more digging on this site and it appears that P2A is part of an overall number and is the Y7, but no agreement on the -5. Some of the thinking on that is it's the year. Assuming this to be correct I now need to know which ECU. Again, two choices and I would have to assume they would be for either the A6 or Y7. PM6 - ...?

GhostAccord

Check out Hondata's ECU identification write up. It explains what all the numbers signify. There is also a listing of ECU and engine/chassis pairings on their website as well.

https://www.hondata.com/techecuid.html

Rugger53

Hondata I did so visit. PM6 is for the 88-91 Civic/CRX SOHC Si. The three digit numbers following those are the revisions of the ECU.

You guys have been great. Many thanks.

Peace n love ya'll.

TomCat39

From our head code list of users reporting head codes:

https://honda-tech.com/honda-civic-d...-here-3210150/

P2A has been reported on the D14A3 and D14A4, it's been reported on the D16Y4, only once on the D16Y7, usually the Y7 has been reported as the P2F.

And then again the P2A has also been reported for the SOHC JDM Non-Vtec ZC motor. which shows the -3, -4, -5, -8, -9 and -10.

I would suspect your head is most likely the ZC variant.

The P2A is the casting which looks like fits several motors, the differences between those motors will likely just be the camshaft and the springs and retainers.

The rest of the specs are the same.

I also think the P2A reported as a D16Y7 may have been a head swap as no other Y7 has been reported as a P2A.

Pulled from Wikipedia on the D-series motor:
ZC

A Honda non-VTEC SOHC ZC 1.6 engine in a 1996 third generation (DC1) JDM Integra.
A few D-series variants are labelled (Japanese: Honda ZC engine) (usually JDM), but they are not truly a different series. They are similar to the D16Y4, D16A8, D16Z6, D16A1, D16A3, D16A6, D16A9 and D16Z5 engines.

The non-VTEC SOHC ZC is similar to the D16A6 ('91–'96)

So if you run the OBD0 PM6 ECU you should be fine. The head given to you is a pretty good match for the D16A6 it was replacing.

The D16Y7 block is basically the same as the D16A6 so even though it doesn't say D16A6, your block and head are pretty much the same thing.

D16A6:
Bore and Stroke: 75.0 × 90.0 mm (2.95 x 3.54 in)
Displacement: 1,590 cc (97 cu in)
Rod Length: 137 mm
Rod Ratio: 1.52~

D16Y7:
Bore and Stroke: 75.0 × 90.0 mm (2.95 x 3.54 in)
Displacement: 1,590 cc (97 cu in)
And even though wikipedia doesn't say it, from everything I've seen the D16 rod length is always 137mm. The D15's are typically 134mm.
So the rod ratio will be the same.

You are good to go if you can located the proper OBD0 PM6 ECU.

Rugger53

Tomcat, that was awesome.

How much coffee did you have for dessert?

TomCat39

Too much, my ulcers are telling me about it.