like everyone else I am undertaking a hybrid H22/F22 build and I am about to order some pistons but I just want to make sure I have the right specs. I don't want to end up with the wrong pistons just because of a mathmatical error. So heres what I want

I want forged 85.5 mm pistons with a CR of 8.5:1

H22 head = 53.8cc
Cylinder vol(85.5 bore,95mm stroke) = 545.4 cc
Head gasket(85.5 bore, .026" thickness) = 3.8cc
Total volume = 603 cc
compression vol at 8.5:1 = 70.9 cc

piston dish = 13.3 cc???

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Speedra500 &raquo;</TD></TR><TR><TD CLASS="quote">like everyone else I am undertaking a hybrid H22/F22 build and I am about to order some pistons but I just want to make sure I have the right specs. I don't want to end up with the wrong pistons just because of a mathmatical error. So heres what I want

I want forged 85.5 mm pistons with a CR of 8.5:1

H22 head = 53.8cc
Cylinder vol(85.5 bore,95mm stroke) = 545.4 cc
Head gasket(85.5 bore, .026" thickness) = 3.8cc
Total volume = 603 cc
compression vol at 8.5:1 = 70.9 cc

piston dish = 13.3 cc???</TD></TR></TABLE>

I just spent an hour trying to come up with the numbers you are getting for cylinder volume and i keep coming up a few cc short of what you have.....I'm still learning this stuff so i am sure im prolly entering a wrong number into the equation.

How are you determining piston dish volume?

 

by figuring the total uncompressed volume, then dividing it by 8.5 which will yeild the desired compressed volume, then I added the head vol to the head gasket vol and then subtracted it from the desired volume. Are you calculating the cyl vol by 42.75^2 * Pi * 97 / 1000?

 

so far so good, but your volume that is left when the piston is at TDC may be off. you need to know stock f22 piston to deck hieght. most honda motors don't sit at exactly top dead center.

its been a while since i had to do this, so i can't remember what the piston to deck height of the h23/f22 is and the h22.

make sure to post in my thread on the hybrid. im at school so i don't have alot of time to dig for numbers. but you can check http://www.c-speedracing.com look in thehow to. they have a good cr calculator. maybe taking the specs from the f22 or h23 you can find pistont o deck hieght by backing into it.

also search the archives, there is a thread on calculating all this and it may be in there too

 

here is a quick h22 piston to deck calc , thanks piratemcfred

Deck Height = 8.643" (source: Helms manual)
1/2 Stroke = 1.785"
Rod length = 5.630"
Piston compression height = 1.223

8.643 - 1.785 - 5.630 - 1.223 = .0057"

now just do the same for the f22

and i pluged you numbers in to the calc at c-speedracing.com and i was getting 8.69:1 with your specs.

 

alright, well I guess see if I can fix that then, this is why I posted I was hoping you would chime in little, i'll post it in your thread when I figure it out

 

my bad, im an idiot.. i was think cubic inches and not cc's


Modified by Rosko at 8:31 AM 10/12/2006

 

I am getting confused, here. I was told the corrent compression height to use for using an H22 rod with a H23/F22 crank was 1.45" but after looking at stock F22 specs it appears that the piston comes out of the deck which doesnt seem right

8.643" - 5.572" - 1.87" - 1.203" = -.002
DeckH - Rod L - Strok/2 - CompH = Piston-deck clearance??

 

**** i just spent a ******* hour writing up how to figure cr and I lost it ALL!!

you want an h23/f22 rod right? or are you getting custom pistons for h22 rods?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Speedra500 &raquo;</TD></TR><TR><TD CLASS="quote">I am getting confused, here. I was told the corrent compression height to use for using an H22 rod with a H23/F22 crank was 1.45" but after looking at stock F22 specs it appears that the piston comes out of the deck which doesnt seem right

8.643" - 5.572" - 1.87" - 1.203" = -.002
DeckH - Rod L - Strok/2 - CompH = Piston-deck clearance??</TD></TR></TABLE>

thats right.

 

I'm looking to have custom pistons made for use with the H22 rods, so on a stock f22 the pistons come out of the deck?

 

can anyone verify that the pistons come above the deck on f22s?

 

see thats the thing, depending on the rod length you use it carries your calc by +.002 or -.002, in reality thats not a huge difference and own't affect compression too much.

may i ask why your going with such a low 8.5:1 , are you shooting for 600whp plus?

 

im shooting for 550ish, I guess it is a little low but I've seen alot of people running the arias pistons for the h22 and they have the 8.4:1 compression and that is in a larger bore. I guess the tuning is the main thing but I guess it might be smart to have a little higher compression than that so I have at least a little something on the bottom end, although the smaller bores tend to be a little more likely to detonate. Maybe ill go with something around 8.7ish