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308 Posts
Discussion Starter #1
This has been posted before but here it is again. The z6 y7 y8 pumps are the SAME! The only difference is in the outside and how they mount up.

20190512_145755 by rabidflickr, on Flickr
20190512_145827 by rabidflickr, on Flickr

The z6 is the dirty one. Notice the area that meets the oil pan. This means they oil pans are not the same. There is a crank sensor mount on the y8 pump, and the oil dipstick hole, and a different size stud for the oil pickup tube. The y8 pump will mount to a z6 block just fine.

20190512_145859 by rabidflickr, on Flickr

The y8 end plug must be installed with red loctite. The z6 uses a crush washer.

20190512_150607 by rabidflickr, on Flickr

Same pump cover.

20190512_150732 by rabidflickr, on Flickr
20190512_150735 by rabidflickr, on Flickr
20190512_150921 by rabidflickr, on Flickr

The rotor is interchangeable.

308 Posts
Discussion Starter #2
20190512_151113 by rabidflickr, on Flickr
20190512_152357 by rabidflickr, on Flickr
20190512_152408 by rabidflickr, on Flickr
20190512_152535 by rabidflickr, on Flickr
20190512_152541 by rabidflickr, on Flickr

The internal passages are identical. The cross drilled pressure outlet has the same diameter as well.

20190512_153410 by rabidflickr, on Flickr

Same over pressure bypass parts.

20190512_152229 by rabidflickr, on Flickr

Same rotors. They both measure within 0.0001" of each other. Outside diameter 2.8686" Inside rotor tip to tip is 2.3222" 0.3113" thick.

This is a positive displacement pump. There is a certain volume of oil moved per rotation. It doesn't matter if it is 20 psi or 60 psi. (unless there are bad leaks) Because everything involved in the movement of oil is the same on both pumps, they have the same oil flow (regardless of what the Honda service manual says).

You can port these all day long and it won't make a difference for oil flow. If the bypass doesn't open, you have a set amount of flow. It can make a difference for how hard the pump is working though.

Premium Member
'92 CX Twincharged D
750 Posts
Are these OEM pumps?

You may want to see this then

This should clarify the main differences between D-series oil pumps. Here is the measured numeric data. All measures in millimeters.

Rotor tooth count, inner/outer
PM3 9/10
P7A 10/11
PLC 10/11

Rotor outer dia.
PM3 77.9mm
P7A 72.9mm
PLC 76.9mm

Rotor thickness
PM3 6.5mm
P7A 7.9mm
PLC 7.5mm

Inlet port diameter
PM3 oval shape, around 14mm
P7A 14.3mm
PLC 14.3mm

Outer port diameter
PM3 ~12mm
P7A 12.2mm
PLC 12.2mm

Pocket depth, from oil pocket between inner/outer rotors
PM3 12.6mm
P7A 10.8mm
PLC 10.5mm

Pressure relief valve setup was identical in all pumps. Also spring tension feels same. Here is a small summary and notes/comments about those pumps;

PM3: Supposed to be highest flow rate. Abrupt inner shapes, smallest inner volume but smoothest outlet.

P7A: Supposed to be around 25% down in flow rate compared to PM3, no clear reason found for this. Most significant difference is outlet curve shape. Higher tooth count (=higher pumping frequency). Rotors are smaller in dia and pocket depth, but also thicker compared to PM3 so pocket volume should be quite close. Has clearly largest internal volume of all these pumps.

PLC: Very much the same as P7A, but has way smoother internal shapes. I mean here the transitions to pump part where it moves the oil from inlet to outlet side. In/out passage transitions to pump/rotor chamber are equally poor in all pumps. Minor differences in rotor dimensions, but rotor ID and oil seal are a lot bigger because of 4mm bigger crank snout in '01-> engines.

I don't know almost anything about different pumps, so I can't tell what makes the supposedly big flow difference between these pumps. Like I've said one possible culprit is the poor outlet design and implementation in newer pumps, but there might also be difference in rotor pocket volume too.

So, I chose the Y8 P7A oil pump for my D15 build. I'll continue soon with the information about what I actually did for the pump to perform strong in performance application.

I checked some Service Manuals too,

D16Y8 pump displacements is 33.4 liters/min @ 6800rpm
PM3(D15) 45 liters/min @ 6300rpm
D16A8/9 DOHC oil pump is 63 liters/min, something over 6000rpm too.
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