[The_Acid_Beaver]

The high dome and low quench necessitates using higher octane and pulling the timing curve waaaaay back just to keep detonation away. Flat tops or low domes (as exhibited in the build by JD running 87 octane with a stock cam and putting down almost 140WHP) prevent detonation, allow for more complete combustion events, and do not require as much octane to perform perfectly reliably.

A typical Z6 head/P29 combo totally requires 93 octane and some perfect tuning to prevent detonation from pinging the engine to death. Does the combo work? Yes. But it will always be octane and timing limited. Better piston/head combos would put out the same or more power with less tuning hassle and less expense at the gas pump.

The effects of high dome pistons are exceptionally well documented outside the world of Honda D-series engines. The B-series crowd even has more experience with them not working quite so well, even with closed-quench designs like the GSR head. If you would like to see what is really possible, look at the latest crop of small, efficient head designes for Small Block Chevies, and then pay attention to the pistons that come out of shops that consistently build the fastest engines for all the big names in the NHRA. (That's what I've ben doing lately.)

Learning about the difference quench makes, and trying to keep the combustion chamber as compact as possible to propogate good motion and mixture of the air/fuel, without interfering with the burn, is definitely something worth doing, and is relatively easy in our engines. P29s are, in my opinion, about one of the worst piston designs Honda ever made for our beloved Ds. They have a very high dome coupled with low quench. The PDNs have higher quench and a much lower dome, but, if you are willing to wack the deck a bit, you have a completely superior base for your combustion chamber. If you are willing to spend more time, try to find some pics of Endyn Rollerwaves after they have been run in an engine for a few thousand miles. If you pay attention, you'll find some very interesting properties in the carbon patterns that form (as long as the tuning is right).

Granted, much of this is theory, but the preliminary research suggests that a flat top or low dome piston in our engines will provide you with a much easier to tune and less detonation prone engine. The OEM pistons with dishes are ok, but generally require more extremes to get the compression level to desireable levels. One person in the know, and whom I trust, has run several Ds over 13:1 SCR (static compression ration) on 89-91 octane. It is possible, and hopefully, time will tell that it is a superior combo.

I myself have a set of modded LS rods with used PDNs attached. I got a smokin' deal on them, so, I bought them. However, I'd like to eventually mess around with the PG6s, just for the heck of it.

 

[The_Acid_Beaver]

Oh, and as far as rods go, people occasionally snap rods when running over 8500RPM.

LS rods are much beefier and should hold up better to such abuse. =)

 

[builthatch]

GX pistons and pg6b pistons have been discussed for years, the dynamics of flat tops have been hashed over and over, i def understand all that, but what i'm saying is, it seems as if there is a recent resurgence on this forum regarding these and i don't know if it's really necessary. this is such a low power profile we are talking about here, with these d's, that to invest the extra labor for the same result would be defeating the purpose of the typical d-series enthusiast building the engine. that's what i mean. i acknowledged that there is a physics advantage to using flat tops, like i said it's been a topic of interest on here for years, that i totally understand, however, it seems to me that you can run a p29 setup on california piss if tuned well and not worry....and invest little to no add'l labor for nothing. i don't want everyone who comes on here thinking that he has to deck the block and aim for a zeroed piston to deck value in order for it to work properly, that's all.

i mean, i did it. that's why i'm saying anything, hehe. granted, i went overboard with trying more add-on parts than one probably needs to attain the goals in mind, but still. the basic build was p29 based and it worked GREAT when tuned...lasted for tens of thousands of daily driven miles without issue once it was tuned well.

but i see what you are saying...that there is a demand evidently in this crowd to be able to make more power vs. octane availability and give a little more tuning flexibility. it's a progressive thing and that is totally cool. i tend to think a little more old school, that, if it works, don't mess with it, but there is an element out there that likes to tinker even more to find added benefits that might be of value to others in the community, that previously were not really a concern. a prime example is the use of low octane fuel vs. high octane.

Oh, and as far as rods go, people occasionally snap rods when running over 8500RPM.

LS rods are much beefier and should hold up better to such abuse. =)

i wasn't aware that there were that many people approaching 8500 rpm with these things now. revving that high was not very common and/or needed before because of the low end efficiency of long stroke, but i guess it's happening now. learn something new everyday.

 

[The_Acid_Beaver]

There are a few cams ont eh market that support making power at 8500+RPM. Now, as to whether or not many people can build the rest of the engine to use that capability . . . I'll leave that up to the person building the engine. heh I will be attempting this after I get everything broken in on my A6/PDN/LS/Z6/B2/RDX build. If I can ever finish it. LOL!

I agree with you as to "if it ain't broke, don't fix it," but, I think that if more people are willing to experiment with what has been proven in other engines for quite a while now, there will be more and more people enjoying the fruits of that knowledge in more reliability, easier tuning, and ultimately more power. Progress can be a very fun thing. =)

 

[civicflow]

Wow, I am loving this thread. Awesome info!

Someone mentioned before that the pg6 pistons might need the valve pockets to be modded if used. I plan on staying obo0 with an a6 block/head and a level 2 bisi cam.

Anyone with experience know if the pistons really need to be modified to fit with this combo?

 

[builthatch]

Progress can be a very fun thing. =)

i agree!

 

[cervan]

I right now have p29's in my d16z6 bored over 1mm. I have to say if i had the chance i would go back to stock z6 pistons and mill the shit out of the head to make it a closed deck chamber. The p29's suck in tons of different ways, for one they have absolutely no quench they are 2mm down in the hole their ring lands blow ( in my opinion if your going to spend that much money on the ycp pistons, your better off going aftermarket) and that gigantic fricken ass dome interrupts flame propagation probibally increasing chance for detonation.

Im just waiting for mine to blow a hole in them so i can pull them out and slap some flat tops in there.

 

[builthatch]

I right now have p29's in my d16z6 bored over 1mm. I have to say if i had the chance i would go back to stock z6 pistons and mill the shit out of the head to make it a closed deck chamber. The p29's suck in tons of different ways, for one they have absolutely no quench they are 2mm down in the hole their ring lands blow ( in my opinion if your going to spend that much money on the ycp pistons, your better off going aftermarket) and that gigantic fricken ass dome interrupts flame propagation probibally increasing chance for detonation.

Im just waiting for mine to blow a hole in them so i can pull them out and slap some flat tops in there.

to each his own, but man...waiting for pistons to break that work just fine and can make ample power, so you can buy other ones that will yield very similar power sounds like a waste of money for an engine that is making, what, 150whp or so? i ran a decent amount of timing with my p29 setup throughout the maps and didn't have any detonation issues for what, 70k? i had the KS activity monitored every second that engine was running and it was tuned to run like a top without unusual timing curves....again, if your focus is to run lower octane with the same type of timing events, then yeah, p29 won't be the ticket as mentioned earlier in the thread.

keep in mind too, a head that is milled severely like you've mentioned leaves NO room for corrective machining if the thing overheats and warps from a blown HG or something, meaning, if it needs to be resurfaced, you've got a junk head. and, if it's a ported and massaged head, that is a big loss. best bet is to use a piston combo that doesn't require such aggressive milling, or if you are set on a certain CC shape, reshape the chambers through welding, or deck the block if you must run something that requires closer quarters.

i'm not sure i like where this is going on this forum with the pistons. it seems like some people are sort-of losing focus of what the d is built in the first place and some people might get in over their head, make things too complicated for little to no yield, get discouraged, and move elsewhere where the money and time spent will yield more satisfaction.

just be careful guys with what info you spread and why you are spreading it, that's all.

 

[cervan]

to each his own, but man...waiting for pistons to break that work just fine and can make ample power, so you can buy other ones that will yield very similar power sounds like a waste of money for an engine that is making, what, 150whp or so? i ran a decent amount of timing with my p29 setup throughout the maps and didn't have any detonation issues for what, 70k? i had the KS activity monitored every second that engine was running and it was tuned to run like a top without unusual timing curves....again, if your focus is to run lower octane with the same type of timing events, then yeah, p29 won't be the ticket as mentioned earlier in the thread.

keep in mind too, a head that is milled severely like you've mentioned leaves NO room for corrective machining if the thing overheats and warps from a blown HG or something, meaning, if it needs to be resurfaced, you've got a junk head. and, if it's a ported and massaged head, that is a big loss. best bet is to use a piston combo that doesn't require such aggressive milling, or if you are set on a certain CC shape, reshape the chambers through welding, or deck the block if you must run something that requires closer quarters.

i'm not sure i like where this is going on this forum with the pistons. it seems like some people are sort-of losing focus of what the d is built in the first place and some people might get in over their head, make things too complicated for little to no yield, get discouraged, and move elsewhere where the money and time spent will yield more satisfaction.

just be careful guys with what info you spread and why you are spreading it, that's all.

well for one, i have nippon p29's wich seem to be very weak. Two, they are at about 11:1 compression even with my .24 taken off the head because they sit 2mm below deck. and third because they sit below deck there is allmost no quench to help fight detonation.

With flat tops, they are zero decked and if you mill the head abit you can get some more quench and probibally run more timing. It would also help with the flame front as that dome doesnt get in the way so everything burns more evenly.

I know that ben swears by ycp p29's but me personally i would rather get OEM z6 pistons that have a very slight dish to them, and then mill the head to make up for the lost compression, doing this would also result in higher squish.

 

[civicflow]

Someone mentioned before that the pg6 pistons might need the valve pockets to be modded if used. I plan on staying obo0 with an a6 block/head and a level 2 bisi cam.

Anyone with experience know if the pistons really need to be modified to fit with this combo?

 

[The_Acid_Beaver]

You won't get any definite answers about the PG6s from around here, with the one exception being Mista Bone who says they do and another source of mine says they won't. I don't think you will run into issues unless you wack a whole chunk off the head, probably not until you start getting to the 2mm mark, however, I would definitely want to clay the combo before cranking. =)

 

[sl@sh]

interesting topic and equally interesting points given on both kinds of pistons

the p29s (high dome below deck) and the pg6/pdn styles..

while theory is good and the understanding/explanation behind it is indeed appealing (i for one am up for this)

for some reason i agree with builthatch.. theres a sudden boom in this aproach.. making the p29's look bad..

NPR is a good brand ( i know numerous B's running 200whp with them) daily..
now if the dseries NPR suck? i do not know as far as quality goes but knowing theyre the same brand with the B's replacement and in the B world they live/survive well..
il say theyre more than enough (as far as quality goes)

i like the low dome less splitting in the combustion process/quality but i guess for me.. il leave it to when i order custom arias/cp and have a welded a6 chamber head..

i think people get too cought up in the idea.. without noting the fact that our chambers are deep.. unless we resolve that? everything else is half worth..
^^^ so i go with rushi in whats wrong with just decking the block 0.040"
^^^then i realize the piston would be flush to the block but the chamber still deep?
^^^ so id go for 0.010" mill on the block to bring the piston to 0.030" below deck
and mill the head 0.040" to try to make the depth of the chamber a little shallower
but then thats just a thought from my perspective..

dont get me wrong.. i like the idea of having an efficient combustion process/quality letting one run a little less timing than usual (possibly save bearings) and run a little leaner maybe...

but remember one of the few early build/cars that ran fast i still think the simpler p29+arp rod bolt aproach is bang for the buck..

remember simon/djsgtrip 13.15sec p29+crower3 + vafc
unless we're talkin bout dipping into the 12s? il take the p29s

how bout bisi's old 12.68 motor.. p29+1mm welded a6 chamber head..

just my opinion hehe

 

[clubEF9]

Another option is PM3. Probably mill the 0.7mm off from their tops to make them flush.

That's the option I went with minus milling them and I run a Bisi 2.2 cam, no issues. Hella fun! unk:

 

[civicflow]

The pm3 npr pistons w/rings are pretty cheap too on ebay. I might go with that if I don't use my p29 pistons. I already have the p29 pistons used but in good shape still in a dohc zc.
I am not sure if I need to bore my d16a6 block though so I don't even know if I could use them. I haven't had a chance to tear it apart and get it checked out yet.

Anyone have any dynos using anything other than p29 pistons in a d16a6 block/head or even other block/head combos?

 

[marcin]

I right now have p29's in my d16z6 bored over 1mm. I have to say if i had the chance i would go back to stock z6 pistons and mill the shit out of the head to make it a closed deck chamber. The p29's suck in tons of different ways, for one they have absolutely no quench they are 2mm down in the hole their ring lands blow ( in my opinion if your going to spend that much money on the ycp pistons, your better off going aftermarket) and that gigantic fricken ass dome interrupts flame propagation probibally increasing chance for detonation.

Im just waiting for mine to blow a hole in them so i can pull them out and slap some flat tops in there.

im not picking on you but right there you are reciting the latest thinking & what seems like a trend.

I do not disagree with the theory, quite the opposite. However, PLENTY of people have used p29's as a low $ solution that has shown great gains.

m.

 

[The_Acid_Beaver]

Civicflow-

http://www.d-series.org/forums/showthread.php?t=95775&highlight=87+Octane

 

[civicflow]

Thanks for the link, I seen his thread on honda-tech before the site changed and never found it again.

I do like the gx piston/y8 head setup but don't think I will have the money to do that, plus I want to stay obd0 and non-vtec.

Right now I figure p29 w/bisi stage 2 cam or buying pm3 w/bisi stage 2 cam.
If I have the money I will go for the pm3 pistons but we will see.

Although I am open to more sugestions and setup numbers/dyno charts.

 

[cervan]

im not picking on you but right there you are reciting the latest thinking & what seems like a trend.

I do not disagree with the theory, quite the opposite. However, PLENTY of people have used p29's as a low $ solution that has shown great gains.

m.

I agree they are a cheap drop in replacement with a good bang for the buck trade off. But i personaly would not install them again because for one if you want to get the high compression like the 12:1 compression that the calculators all say, you have to mill the deck a good 2mm (.40) and if you do that, your scrwed if you use any other piston.

Here is a little snippet i took from a webpage, its all bones information.

Using LS Rods in a D series:

The crank ends of the LS rods and D series are same size around at 1.890" (48mm). The crank end bore width needs to be milled to match the D16 crank rod journals. Shave .022" off each side of the crank end of the rod.
The piston end bore needs to be bushed to match the D16 piston's smaller pin size. The pin on the LS pistons is 0.826" (21mm), the pin on the D16 pistons is 0.748" (19mm). You need the custom made aluminum-bronze bushing with a width of 0.786, ID. 0.748, OD. 0.827 +(over) three thousands due to the bushing will be pressed in the small-end of the LS rods, so the bushing won't come out of the hole. Crower sells these for around $40 a set.

B16A Rods matched with non-US Supra 1G-GTE pistons:

I calculated the following #'s for this combo
Piston volume = -7cc dish
Compression height = 33mm
Rod length = 134mm

Pro's of this setup = Strong B16 rods and forged Supra pistons

This is information has been gathered from Turbopanda ( username on www.honda-tech.com ). He sells this set-up for about $400.

The shorter B16 rods with a D16 stroke will result in a 1.49 rod/stroke ratio, down from the stock D16 1.52 R/S ratio.

The Toyota pistons' height make up for the length of the rod, that's why it’s still usable in a D series engine.

1G-GTE Supra pistons are 75mm. B16A rods are a lot stronger than D16 rods, and can handle boost way better. The rods are modified in order to accept the Toyota pistons. Installation is as simple as replacing your pistons and rods. The Crankshaft needs no modification, although the bottom of the short block will need to be notched a little so that there is enough clearance for the B16A rods


I checked out the compression with the 1g-gte supra pistons with stock d16 rods in a d16 block, it turns out to be 12:1 compression. even before milling.

And coupled with LS rods your set for a very good n/a monster.

 

[The_Acid_Beaver]

How much do those pistons weigh? With that much of a compression height I would think the Supra pistons would weight quite a bit. The Rollerwaves I have are 252g, and that is for an awesome design. I am wary of using pistons designed for other manufacturors engines in our hondas.

That being said, what times or how much power have people made with these Supra pistons?

 

[sl@sh]

yeah the supra pistons i asume should be quite heavy.. i mean the p29's in 1mm oS is already significantly heavier than standard 75,

another option for the people who dislike p29's

is (as mentioned) the pm3's which should sit around more than half mm above deck..
have the chamber counter bored to match the dia. of the bore on the block , and mill to taste hehe..

i for one will still run p29's in the future..
i guess i wana run as fast as djsgtrip or bisi on p29's atleast bfor trying a more "tech" aproach.. but thats just me.. i wana make sure i can squeeze the most out of it bfor goin to a better configuration.. cuz obviously a beter configuration will yield more power..

just my way of not overbuilding a motor (then making less power than it should)
^^^^ this has happend quite alot of times hehe