[FAQ] D Series piston project update!

[Sonny]

I have 2 more (D16Y8 - P2P; D16A6 - PM6) ready to go, but I need to press out the wristpin first. My worksheet is almost done! Thanks to all who have contributed pistons. Sonny

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[johnny hatchback]

just out of curiosity, will the 88-89 integra pistons work ok in the 86-87 integra motor? I assume they do but you never know unless you ask. They look like they would be a lot stronger, whats your opinion?

-johnny

[89civicdx]

I may be wrong

BUT the P29 piston pictured looks like it is .050 oversize as the stock bore size(for 88-89 teg) looks like the PG6B ,doesn't it?


[Modified by 89civicdx, 5:47 AM 5/3/2002]

[Sonny]

Johnny: The 86-87 Teg pistons will work in the 88-89 engine. The heads are the same. I measured them myself. 86-87 Teg pistons will yield 9.3:1 vs 9.5:1 for the 88-89 Teg pistons. To get that compression ratio, you must have an 86-89 Teg head or a ZC head.

89civicdx: That is a stock bore P29. Maybe it looks a little bigger because it's cleaner than the rest?

Sonny

[keithv]

good stuff man....keep us informed!

[Mugen Dom]

im tellin u try the d15 pistons they are higher than a d16 suposidly says mista bone

[Zer0DazE]

the d15 pistons sit up a little higher

this project kicks ass still

[l]

do you know the CR of PG6B in a d16a6(crx si) ? ? ?

i have these pistons and im curious to know what the CR will be... i was hoping to get the P29's but goofed... any info... .

[Sonny]

do you know the CR of PG6B in a d16a6(crx si) ? ? ?

i have these pistons and im curious to know what the CR will be... i was hoping to get the P29's but goofed... any info... .

My calcs show ~10.5:1 using the stock D16A6 (.048") headgasket. If you use a D16Y8 gasket (.037"), it will be 10.78:1.

Sonny

[Sonny]

Here's part of my piston worksheet. It's not quite done yet, but I used the compression calculator formula at the bottom of the sheet so that you can plug in the values for different heads/pistons and get the compression ratio.

This sheet makes a couple of assumptions:

1) The headgasket has the same bore as the piston. Usually the headgasket is a touch bigger to allow for oversized pistons, so the numbers that I generally are probably just a touch high.

2) Heads have not been milled and blocks have not been decked. Ie, no material was removed from either surface.

3) Note: You cannot use a DOHC head/gasket on a SOHC block and vice versa. It actually can be done, the head and gasket must be modified. Not really worth the hassle, IMO.

4) The piston dome is a calculated value. Using the factory specs for the compression ratio, I know that number. Compression height, head gasket thickness, chamber volume, piston-to-deck clearance, and bore/stroke are all values that I know. Using all of those variables, it's easy for me to plug them in and derive the volume of the dome/dish of each piston.

5) The bottom of the chart is where you can specify the specs of each part and get the compression ratio by using that combo. The example shows JDM ZC pistons with a D16Y8 head and a D16Y8 headgasket. You would need to check to see if you have clearance problems with this configuration if you're gonna try it!



Sonny

[89dxhunchback]

My question is, if I put 92-95 d16 pistions ( or the whole block ) with my factory d15b7 head would I get real low comp ?? I know I would lose Vtec, but I would gain alot more boost...

mini-me=d15b7 block, 92-99 head=11.5:1 comp.
unmini-me=d16z6 block, 88-91 16v head=8:1,8.5:1 ???

I bet you spend a lot of time on this pistion project of yours... Great idea though.


[Modified by 89dxhunchback, 7:32 PM 5/3/2002]

[OneScarySOHC]

what would be the best oem piston to use in a z6 to bump the compression to around 10:1 or so

[l]

what are the calculations??? i multiplied them and go some large large number... and then if you have .0000 for piston to deck clearence it will calculate 0

[Sonny]

BTW guys, since my worksheet isn't "active" yet, you can take the data that is in it and use C-SPEED's excellent compression calculator to figure out what compression you get using various parts:

http://www.c-speedracing.com/howto/c.../compcalc.html

Sonny

[89dxhunchback]

Funny, everyone told me that a mini-me makes about 11.5:1 comp. but if you plug the numbers it's only 9.9:1 comp on a d16a6 doesn't that mean it would be 10.1:1 comp on a d15 ?

[Sonny]

Funny, everyone told me that a mini-me makes about 11.5:1 comp. but if you plug the numbers it's only 9.9:1 comp on a d16a6 doesn't that mean it would be 10.1:1 comp on a d15 ?

I don't have any info on the D15 engines yet, so I can't comment on that. Your previous post said a 92-99 head, but those heads are not the same so that one number that you've been given cannot be right. The 96+ head has a the smallest chamber and will yield higher compression than the 92-95 head.

Sonny

[Todd00]

This is all very good info. You should definitely post on a webpage somewhere permanent. There are very few who knows about the underrated D series motors.

[89dxhunchback]

I know, I used the figures for a 92-95 ( sense I have a 94' si head )... 9.9:1 on a d16a6 and d16z6 head w/ 92-95 head gasket.. I could live with that and my Zex for a good time to come... But if comp. is really somewhere around 11.5:1, I'm only going to use Zex at the track on 116 oct.

And yes, You really should post this info on a web page !!! It is very help full when thinking about a "next motor build-up", mines a low comp. t-25 turbo car.. d-series of course !!!


[Modified by 89dxhunchback, 8:46 PM 5/3/2002]

[Mugen Dom]

Funny, everyone told me that a mini-me makes about 11.5:1 comp. but if you plug the numbers it's only 9.9:1 comp on a d16a6 doesn't that mean it would be 10.1:1 comp on a d15 ?

I don't have any info on the D15 engines yet, so I can't comment on that. Your previous post said a 92-99 head, but those heads are not the same so that one number that you've been given cannot be right. The 96+ head has a the smallest chamber and will yield higher compression than the 92-95 head.

Sonny

that is correct im gonna figure out my compression tonight when im done working... im thinking it will be very similar to ur 12.2 :1 due to teh d15 has higher compression already and with the d16y7 head witch is about the same compression chamber to the d16y8.... if i use the d16a1 pistons that would eb some high compression eh

[brent_G]

This is a good post. I orginally ran into the problem with using the d series compresion calculator and not entering the right piston to deck heights and got way wrong numbers. So that chart you posted was the deterimining factor in me getteing the correct info. I knew 14:1 compression was wayyyy to high for p29 pistons in z6. MY final compression numbers i came out to was 12.03:1 which is about what im looking for.
Thanks

[91civicDXdude]

I've personally taken apart an 89 D16A1 integra, and guess what? It yielded PM7 pistons, not P29.

[Sonny]

Yeah, me too! There were P29's in one engine and PM7's in the other. (wtf??) I did a little bit of digging and found that the P29 was a .25mm oversized piston. If you go to the dealer and ask for oversized 88-89 Integra pistons, you get P29's. However, the stock ones are PM7. Nice logic they used there, huh?

Sonny

[89dxhunchback]

As an update to what I posted 6 months ago, I'm running a D16Z6 block, D16A6 head ( un-mini-me ) and it runs great with the WRX turbo I'm using. With my .043 Mr. gasket MLS HG its 8.5/1 compression.

Funny it felt like more than 6 months ago...

My friend also used Z6 pistons in his A6 block and he is happy with them too ( even though he refused to listen to me about getting the rotating ass. re-balenced b/c the different weight of the pistons ). He is using a Greddy kit with DSM SMIC.

I've gone to 10psi without a problem on pump gas ( going back to 10psi as soon as I can get to a dyno ), but my friends is using a FMU, so he's stuck at 6psi...

[djphonics]

Originally Posted by Sonny

Yeah, me too! There were P29's in one engine and PM7's in the other. (wtf??) I did a little bit of digging and found that the P29 was a .25mm oversized piston. If you go to the dealer and ask for oversized 88-89 Integra pistons, you get P29's. However, the stock ones are PM7. Nice logic they used there, huh?

Sonny

That's weird. The parts diagram for the '88-'89 Integra motor shows P29 pistons for all (normal, .25mm over, and .5mm over).