b16a pistons in b20a

[B20A_3G_CiviC_HatcH]

hi all
i heard b16a pistons fit in b20a's the bore is the same but just to confirm will the pins go through the stock b20a rods? has anyone done this before? they are suposed to have higher compression around 10.5:1 will the stock rods be ok with that kind of higher compression if they will fit.
anyone with something to contribute would be good heard

cheers,
AleX

[Kabuki]

I'm not 100% sure on the Accord/2G Lude B20A, but on the USDM B20A5/A3, the answer is no. The Carbed B20A3 uses a 20mm wrist pin, the B16/18/20B uses a 21mm pin, and the B20A5/B21A1/F&H series all use 22mm pins. And of course, the ES and A18/20 engines use 20mm pins, like the carbed Lude.

Also, the Prelude Power folks have found that the F22/H23 rods are identical in length and bores to the stock units from the B20A5 and B21A1, but are much stouter. This is likely the case with the Accord B20A as well.

[B20A_3G_CiviC_HatcH]

are all those measurements for USDM engines? i am in new zealand we mostly have JDMs would their be a difference. i have a b18a that spun a berring i could rip and investigate b18a is the same apart from stroke isnt it?

[carotman]

You need to have the piston enlarged to accept the 22mm wristpin. That's what I did on my B20A and it works fine.

[B20A_3G_CiviC_HatcH]

i have here in my hand a piston and rod assembily from a b18a which is the same as b20a wristpin size is 21mm according to my eyes so they shud fit
power increase i THINK is worked out as
every 0.1 point of compression is 3% power increase
i also believe the stock b20a pistons have 9.4:1 ratio the b16a pistons are 10.2 or 10.5:1
giving therotical power increase of 24% if its 10.2:1
33% increase if it is 10.5:1
thats a lot more power either way.

i also heard that the accord b20a is 160hp stock
which would make the power output 200-215hp ISH

does this sound correct to anyone?

[thegreatdane]

B18A uses 21mm wristpin? I wasnt aware of that. Is that the only difference between B18A and B20A rods?

The B16 pistons might be a certain c/r ratio in the B16 engine, and another c/r ratio in the B20A engine.

[B20A_3G_CiviC_HatcH]

i am in new zealand and so mostly get JDM engines iv been told there is no difference but i think thats bull

this b18a piston is definately 21mm
as for weather it will give more compression im sure it will there is a pic of a b20a with head off (blown headgasket as u can see) pistons are flat


next image is of the b16a pistons. new ones even. as you can see they have a lot more material on top which will increase compression.



i will have to see what exactly is different in a b20a when i get an engine in a few days. but the wrist pins shud be the same or the same length rods so i could use these b18a ones i have here.

AleX

[Kabuki]

That's not a B20A, unless the Accord version uses the same 83mm PK3 Pistons that the B21A1 uses. I suppose it's possible, but doesn't really make sense, unless the Accord B20A has a shorter stroke, allowing higher revs, which gives it the higher horse power.
You should difinitely MEASURE the pins, because it's only a 1mm difference across a 21-22mm distance. It'll be very close visually.

[thegreatdane]

That's not a B20A, unless the Accord version uses the same 83mm PK3 Pistons that the B21A1 uses. I suppose it's possible, but doesn't really make sense, unless the Accord B20A has a shorter stroke, allowing higher revs, which gives it the higher horse power.
You should difinitely MEASURE the pins, because it's only a 1mm difference across a 21-22mm distance. It'll be very close visually.

It's not PK3 pistons, it's PH3 which is the ones the B20A use.

Yes the c/r ratio will get higher with the B16A pistons but I'm saying that it might not be the same c/r ratio when you put them in the B20A as when they were in the B16A.

[Kabuki]

It's not PK3 pistons, it's PH3 which is the ones the B20A use.
Yes the c/r ratio will get higher with the B16A pistons but I'm saying that it might not be the same c/r ratio when you put them in the B20A as when they were in the B16A.

Whoops... Sorry, it looked like the Pistons said PK3... Upon closer inspection, they don't.

Yeah, the CR all depends upon the combustion chamber. Like with the D series engines. Most of them have somewhere between 9.0 and 9.5 to 1 stock, but if you take one of the VTEC heads and use it with the pistons from a non-VTEC engine, the compression becomes insanely increased. Like, 10-12:1 depending upon the exact combination.

[thegreatdane]

Excactly

[B20A_3G_CiviC_HatcH]

sweet i can do a compression test to figure it out when its all together cant i or figure the math out now. anyone know how?

[Kabuki]

sweet i can do a compression test to figure it out when its all together cant i or figure the math out now. anyone know how?

Measure the combustion chamber size in the head. then mesure the dish or dome of the piston and do the math.

[carotman]

I'm using P73 pistons in my B20A so I know it's possible to use them

My B20A had PK2 pistons in it too.

[B20A_3G_CiviC_HatcH]

hmm theres a difference in piston types? well il see what my b20a has when i get it in a week as well as the wrist pin size is for it. would there be a difference cos i hav b16a1 pistons to go on what did you use carotman

[Civvy]

you would be better off taking .40 thou from the head and leaving the shape of the combustion chamber alone.
Vtec combustion chambers are penthouse ours arn't.

[Kabuki]

I have since asked my machine shop about the wrist pin size issue. They said that it's a pretty common practice to just use the smaller pin that matches the pistons and machine bushings for the rods. In fact, it's something that many domestic cars come with stock.

[carotman]

The problem is that the bushing has to be 0.5mm thick. It's almost impossible to install a bushing that's so small. You either have to machine the rod to accept a bigger bushing that will be pressed in, or machine the piston to use the bigger pin and forget the bushing.

[Kabuki]

Hmm... My machinists didn't seem to think that would be a problem.

[Lok]

Please Read here:

http://www.preludepower.com/forums/s...ght=B20A+specs

Maybe here we have a cheap mod?

B16A pistons on B20a give 11:1 C/R as somebody had measure..........ITR
pistons like Carotman's set up give more than 11.5?
if that is true, will be great! because stock B20A has 9.5:1 C/R.
So 11:1 C/R with B16a pistons ( realy cheap) will give a very noticeable increase in power and torque.

[carotman]

Ideeed!

The B18C pistons I have give a nice upgrade. I could hve gone with JDM ITR for a even higher compression but the USDM type-R was more than enough for my cheap canadian gas

[mykwikcoupe]

so carot did you ever do the math to figure out exactly what CR you have and when you had the pin holes reemed did they ask you if you wanted the new holes offset up or sown or did they just take a larger bit to it and center it? Im asking because Im going this route and am also going with a large turbo setup and 11:1 CR is very bad with high boost. Ive got my choice of 8.5 or 9.0 pistons and I want an overall higher than 9 but lower that 10 or 9.6 for that matter.

If your added just a point or 2 ill get the 9.0 and end up perfect but if it adds more than Ill have to get the lower 8.5 and hope its below 10. Thanks again. Mike

[thegreatdane]

Raceengineering has Wiseco turbo pistons that will fit your B20A. They are listed as B20A5 pistons. These use a 21mm wristpin.

[Kabuki]

Uh... Something isn't right there, because the B20A5 uses 22mm wrist pins. It's likely a misprint. I'd still really like to know for sure about the JDM Accord B20A. I know they are a different piston than the B20A5 (PH3 versus PK2), but if the B20 uses the same length rods with the same large end bore, but the 21mm pin, then that would be the best thing ever! Then the Lude guys can use those rods with the "normal" B-Series pistons without modification.

[thegreatdane]

Oops, sorry I meant to write 22mm wristpin lol. This is what the Accord B20A engine use.

I cant remember what the deal is with the JDM B20A engines, but with the European B20A '88-'89 engines they use PH3 pistons as the standard sized pistons, and when using oversize pistons they use PK2 oversize pistons.