yungone501

iTrader: (4)

I've had several people here lately ask me about if using other 89mm pistons for the j32/j35 is possible and although a few of them (89mm pistons) are made, only the k20/k24 (+3mm) pistons match their specs.

A typical j32/j35 and k20/k24 (+3mm) piston uses the following specs:

Compression height (pin center to piston top)- 1.181" or 30mm
Pin diameter- .866" or 22mm
Bore diameter- 3.504" or 89mm

The thing to be careful of is that the stock k20/k24 piston uses an 86mm bore which is 3mm too small for the j32/j35 89mm cylinders. You MUST use the oversize pistons that are 89mm in diameter and are usually noted to have "+3mm". Do NOT try and use the H-series pistons, they have a different compression height. There are several piston manufacturers that make them such as Wiseco, CP, Ross, Arias, JE (and a few more) but to my knowledge Wiseco is the cheapest in regards to value. JE is considered by many to have the best quality and strength.

Here's a small list that I made with part numbers and compression ratios of k20/k24 89mm pistons from various manufacturers. One thing to remember is that the k20/k24 combustion chambers do not have the same volume as j-series heads so this means that any compression ratios given with pistons on manufacturers websites will NOT be accurate. For those who know how to use Google, search for "compression ratio calculator" and use the chamber size of 53.5cc's to determine the correct CR for what ever +/- volume the piston will possess.

Wiseco-

K634m89 +5 dome

K568m89 -9 dish

K573m89 +8 dome

K650m89 +10.5 dome

JE Pistons-

242869 8.2:1

309420 9.0:1

309423 10.0:1

309426 11.5:1

CP Pistons-

SC70453 9.0:1

Though it's clearly not a full inventory list, this will help some of you to have an idea of what to look for in the catalogs.

Some of you may be wondering why not just "do things right and order the correct CUSTOM pistons". Well, that's because most manufacturers charge a bit more for each piston and will also take them typically 3-5 weeks to manufacture them. Lastly, the last two sets of Wiseco pistons I've seen have the same part numbers as the k20/k24 pistons do right on the crown. The k-series pistons are tried and true for fitment.

Here's a few pics I took comparing the K568M89 Wiseco piston to the stock j35 piston from an 05 Odyssey.








And just to show off the beauty in machining & design...

KN_TL

iTrader: (3)

I'm not sure if it's a common practice to just take these off the shelf pistons and install them after a quick hone.

I took all of the measurements to make sure my bore was within spec and I couldn't find any off the shelf pistons that were large enough to meet the clearances. The +3mm piston is a 3x overbore for the target engine and I assume is at the service limit for that block.

I'm just passing on my experience so you aren't caught by surprise like I was. Customs were $300 more than stock.

yungone501

iTrader: (4)

My stock bore in my j35a6 block was exactly 89.010mm with new hone. A stock j35a8 piston measured 88.985mm in diameter. The Wiseco piston measured 88.980mm. Both pistons are new. Most aftermarket piston makers will do the lower end of spec (especially performance pistons) and that's because chamber temps are much higher. The would obviously be bad for material expansion if tolerances were left higher in spec. Though I don't think a piston would ever seize or gall the cylinder wall, it would probably increase the wear rate on forced induction applications.

You may have read or seen something that happens when forged pistons are used called piston slap. This is the exact reason why slap occurs. It's only audible/present until operating temps are reached.

yungone501

iTrader: (4)

Forgot to ask KN ,where did you take specs from on the piston? Because if it was on the top near the crown, that can be as much as .3-.5 mm smaller than the largest part of the piston which is usually 1-2 inches down below the top. Pistons are tapered for heat expansion om the crown.

KN_TL

iTrader: (3)

All I am doing is providing information to someone less informed as I was.

Much information is given without prerequisite details so I just want to try and pass on what I have learned and mistakes made along the way.

It's nice that your block was within spec of purchasing a piston off the shelf, I wasn't as lucky and just want to put that information out there.

KN_TL

iTrader: (3)

CP provided that location (1/2 from bottom).

Stock was 16mm from bottom

yungone501

iTrader: (4)

****

Euro-R_Spec_TSX

Coolness.

Euro-R_Spec_TSX

For reference, here are some pics of several different J-series pistons with weights listed as follows...

R9P (new J35 with direct injection): 390 grams
RKG (J37A2): 379 grams
RJA (J35A8): 371 grams
RDA (J32A3): 391 grams

Weights are just the piston, no pin and no rings.





What's interesting here is that only the J37 piston is without coating on the skirt. The J37 block does not have iron sleeves, so this makes sense. But the coating on the R9P piston suggests that it has iron sleeves. Why would Honda go back to iron sleeves with this new engine block?

screaminz28

iTrader: (1)

Can you take some more pics of the new J35 piston? The top appears to have a large trapezoidal relief. What purpose does that serve? Does the injector protrude that far for DI, or is there something else? Could these be the next "roller waves"? lol

Euro-R_Spec_TSX

The circular part of the relief is under the injector. The larger rectangular part of the relief is under the spark plug. I would assume that the shape is such to optimize the flame propagation. I highly doubt that the injector protrudes into the chamber.

Mondo375

iTrader: (3)

I love engine internals!

yungone501

iTrader: (4)

First of all, thank you for doing this Eric. I've got dozens of various rods and pistons that I've either collected or purchased specifically for weight and measurement specs but have yet to actually weigh them all.

Secondly, in regards to the weights that you've taken, I'd assume that the R9P and the RDA pistons are heaviest because of the added material in the dome. The RDA has a raised rectangular portion in the center of the dome to increase the compression and the R9P has raised material of which forms the lower portion of the DI systems quench shape. The j37 piston, IMO, is probably Honda's worst piston ever produced. Its a very brittle material due to the high silicone content (aka hypereutectic) but is manufactured using this process for weight savings ONLY...it's very weak. In my experience, the RJA j35a8 piston is one of the toughest made yet. Though it can be considered to have weak ring lands, the overall strength of it is surprisingly very high. I would comfortably run this piston up to 450hp with added gap in the upper rings and if installing new, coat the dome with a ceramic coating. I've ran them in my previous j35a8 boosted at 15lbs and they handled very well. Again, stay out of detonation and make sure your tuning is done right and these pistons are by far the best 3.5's I've seen yet.

Finally, you mentioned the decision of Honda returning back to the use of iron cylinders. Two possibilities here. One was that Honda had to keep up with the whole "downsize" thing in engine manufacturing or making the most out of the least. Though the j37 engine was an excellent engine IN STOCK FORM, it was essentially the j-series block pushed to the absolute limits. It was something new and I think Honda realized that it was the absolute limits and being the conservative company they were in engine reliability, made the decision to change this potentially disastrous design before it became just that: a disaster. Downsizing and potential engineering flaw were my two points there. Iron sleeved engines just make way more since. Its a truly delicate process and one that is generally only done in situations where long term reliability isn't a factor such as Formula 1 racing.

MyKL

Hi, yungone501
How do you think, is the CP pistons 70453 more powefull (heavier, thicker wall) than Wiseco K568M89?

And one question. What radical loose leaves and studs you used?

Euro-R_Spec_TSX

I'm guessing that the "Crazy Russian" is using Google translate?

I wonder what a "radical loose leave" is?

kingkong_dav

Tony the Tiger was the one who tried this k series piston in the j and it was sucessful.700hp

Atlas.46

the j30a4 is 86mm....

MyKL

Yes ))) sometimes
Maybe "connecting rod bearings"?

MyKL

And how long did it work?

Euro-R_Spec_TSX

Another OEM piston for comparison: RK1
This is used in the J35Z6 (4th gen base TL).
Looks identical to the J35A8 piston except for the coating pattern. Same weight as the J35A8 piston.

yungone501

iTrader: (4)

Awesome, great info Eric. Thank you.

You wouldn't happen to have specs for the 08-10 Accord 6MT j35z3 pistons using the "R72" part number would ya? I'm about to do a build for a customer and we will possibly be using these pistons to acquire a lower CR but unless you can help, I'll end up having to buy one for specing....which would have to be done anyhow if its never been done. I'm hoping they have (just as the RK1's did) the same profile, design and density as the j35a8 RJA pistons that have notoriously proven their strength over the yeas by handling decent levels of boost and not to mention....detonation. Lol

Euro-R_Spec_TSX

Negative on the R72 piston. And by the way, the J35Y4 rod is definitely better than the J35A8 rod. More meat on the cap and side beams. As I suspected, it's designed to throw around a heavier piston and thus more material in the right places. Using the J35Y4 rod in place of a J35A8 rod should allow revving a bit higher without worrying about blowing up the engine.

yungone501

iTrader: (4)

I missed that. How much more material are we talking here? Have you done any weight comparisons out of curiosity?

Euro-R_Spec_TSX

It's not a huge difference. The RJA rod weighs about 528 g and the R9P rod weighs about 534 g. You can see from the pics where the extra material is.





Also, I discovered that my scale reads about 3.4% high, so the above piston weights should be re-calculated as follows:

R9P (J35Y4): 377 grams
RKG (J37A2): 366 grams
RJA (J35A8): 359 grams
RDA (J32A3): 378 grams

yungone501

iTrader: (4)

Yeah, now that I look closer, it's plainly obvious on what you're talking about here. Especially around the small and big end bores, it appears between 1-2mm's have been added. Also, the lower portion of the beam has some minor changes to it. That could make a big difference in regards to power handling capabilities. I know both of the RJA (j35a8) pistons and rods are some of the strongest I've seen yet and they could've just met their match with the R9P components.

I've recently purchased two brand new R70 short blocks that are the j35z3 series engines. One of them will be used and the other will be dismantled for the block on my 2.7 build. I'll be able to compare the rods/pistons from it very soon. I do know that the TSX and the Accord 3.5 w/6mt's use the engine but the tougher 4g TL 3.5's use different internals which tells me the j35z3's could have weaker internal components. I'm also anxious to measure the bearing clearances just to see where Honda sets them in regards to the scale. I've always heard that they make them on the tighter side and if that's true, we're talking a mere .0008" of main clearance! Dayum!

Standard and new clearance is normally set between .0008-.0017"

Service limit is .0020"

KN_TL

iTrader: (3)

Robert, can you tell me what the pin end width is on the Wiseco K568m89 piston?

gerzand

iTrader: (3)

22mm known as the wiseco s550

KN_TL

iTrader: (3)

I'm looking for this measurement:

MyKL

I didn't have pro tools
27mm

yungone501

iTrader: (4)

I'm assuming you mean the distance between the pin bores beneath the piston on the Wiseco piston and NOT the pin diameter. If I'm correct in saying this, the distance is 26.670mm. Remember the stock k20 SE rod width is the same as the j-series so if this rod works with the k20, it will also work with the j-series. Besides, I don't believe there's any side thrust against these bore walls. If there were, we would either see wear marks or thrust bearings/washers between the pin and bore wall. It seems logical to say that it's both the alignment of the rod and piston as well as the fitment clearance between the pin and bore that keep the small end of the rod centered perfectly between the bore walls. I honestly wouldn't worry too much about this....especially since its a tried and true j-series interchangeable part.

KN_TL

iTrader: (3)

Thanks
When ordering custom rods they wanted this spec
How long did Wiseco take to produce these for you since they are listed as non-stocked?
Were you able to get 6 instead of 8?

MyKL

Why you don't want to buy Pauter rods instead of custom?

KN_TL

iTrader: (3)

I meant when I bought my rods (Pauter) they wanted this spec. Their rods on the shelf are larger and they milled/balanced them to the 1" width.

yungone501

iTrader: (4)

They took roughly 2 weeks and I went through Jegs to order them. Some people actual show them as an "in stock" item but be careful because this generally means its just a still available product from the manufacturer. As for the quantity, you can order any amount you desire. I ordered one initially for specs and mock up and then once I knew they would indeed work, I ordered a set of four and then a single. If you order them in sets, you can find them priced pretty low. I found a set of four for around $450 from nolimitmotorsport. Check the link out below:
No Limit Motorsport: Wiseco Piston Set K568M89 Acura 4V R/DME -9cc STRUTTED 89.0mm

Though they list them $100 higher, I think I got the $450 when I called and inquired.

thisaznboi88

iTrader: (7)

just a stupid question here but what is the dome side on the head? Is there a significant difference between the j35a8 and j37a1 heads? 86mm? 89mm? 90mm?

KN_TL

iTrader: (3)

Ah, I see. The kit is K568M89 and the single piston is 6568M89.

Thanks Robert!

KN_TL

iTrader: (3)

another question on the Wiseco 536M89's. Are they 4032 or 2618?

yungone501

iTrader: (4)

Dome side of the head is an odd way of saying the heads combustion chamber. There can be two domes when talking about an engines cylinder: the head and the piston dome. Obviously the piston doesn't always have a dome and it can be dished for low compression. And though its not as common, a head also may not have a combustion chamber. I've seen older racing heads have a flat deck with the intake and exhaust valve 90 degrees to the decks surface and be as flat as could be. It's not anywhere as efficient as a small fast burn chamber against a flat top piston and generally required the piston to have the chamber (dished) designed into it.

As for the question on the j37 heads compared to the smaller liter j-series heads, I'm assuming this is coming from the debate over on V6P right? Sonnick (Bryan) asked me to comment on the thread and have simply forgotten. I'll answer this one question and end the debate by saying this one thing: Honda used the exact same heads between the 10+ MDX 3.7 as well as the 08+ Accord 3.5 (and nearly every other motor they built). They are the same notorious R70 castings that are used on the HPD HR28TT and HR35TT engines.

You're welcome and remember that the K568M89 piston is the part number for the -9cc dished dome. Their are other KxxxM89 part numbers that feature other dish and dome sizes to appropriately accommodate the engines displacement or purpose too. Just thought I'd add that in case somebody thought these were the ONLY applicable pistons that Wiseco made for the j-series...or I guess technically the k-series. Lol...

thisaznboi88

iTrader: (7)

Thanks for the answer. We were talking about it over there on the j32a3 swap thread.

I also forgot what the head combustion chamber was called. *studying diabetes right now*

Accord325

What happens if the heads Dome side (J37 90mm CC heads) overlap on a J30 (J30 86mm pistons) ? I would assume the overhang in the combustion chamber is not improving power. That is the main question on V6P.