my compression, for boost?

NYSpeed Automotive
1

Okay so ive been debating what pistons to run in my bseries motor, combining headgaskets and that.

I was thinking of running n/a this year, and then going boost next year. the thing is, i want to get my car completley done this year as far as motor work and then just be able to turbo it next year, (obv with proper fuel adj. and tuning)

But if i run low compression pistons (like 9.7:1), i calculated the compression using a calculator and my compression was low as fuck and my car would be slow as fuck n/a (yes its a honda, i know):banghead:

Using:

For jdm itr p73-00 pistons w/ stock 81mm bore in a b18c block and a 0.393701inch (1mm) thick headgasket, my compression ratio ended up being

11.17:1 static

Would this be safe for my boost goals? Im guessing prob not…

For the life of me i could not fine the dome of a 84mm 9.7:1 CP Piston, so i just used a 84mm PR4 Piston, which has a -3.2 dome, as opposed to a +5.96 of the itr pistons

For N/A i could run a 1layer gasket, and then when i go boost i could use a 3layer or thicker gasket to help lower my compression

with a “84mm CP Piston” the static was 10.05:1 w/ oem3 layer gasket and 10.4:1 with single layer

I “would” like to make atleast 400wheel…

Either way, im looking to get my block sleeved/gaurd/posts w/e in order to make it safer.

Should i just go with the cp piston, and will it still be fun n/a ?

all values were calculated with 8500rpm limiter

2

what cams? itr/ctr or better and it will still be fun to drive…

static is one thing, but if ur running bigger cams >ITR/CTR then you’re making up for lost air out the valves anyway so your true compression will drop down anyway ya know?

Any decent sized t3/t4 turbo will make 400+ so don’t worry bout that.

Anyway, its not worth it to rip the head off and swap pistons later, its a pain in the ass just to make the slow allmotor setup .2 seconds and 1 mph faster ya know. Just leave it at 9.7(by the way that’s not really “low”… my personal scale is high>9:1>low) or whatever you plan on running for your boosted setup and deal with it. 1 point of compression wont make that big of a difference anyway.

Just deal with it being slow cuz even at 11:1, thats pussy compression for an all motor setup anyway. Throw in the forged shit, and hook up a wet kit if its so unbearably slow as a holdover till u boost the bitch.

Alternatively, if you absolutely don’t mind pulling the head and swapping pistons, i’d just throw CTR pistons in there instead of JDM ITR… make it worth your while

3

oh yeah - fuck a block guard, they are bullshit wastes of money.

400 on stock sleeves with forged pistons & rods is totally plausible and safe provided you get tuned…

4

I was prob going to get itr cams w/ itr valvtrain, or skunk2 stage2 Pro series cams w/ skunk2 valve train. either way it wouldnt be gsr. (i know about the springs being the same as itr on the one side as gsr, i just dont remember how it goes at the moment lol)

and yeah my pt exactly, i dont really want to go and tear apart the block 1 year later after i just redid the entire thing,

and i was actually thinking of using spray, i should still be in the 250 range w/ that and it should be “kinda fun” on the street.

As far as sleeves go… do u think i should get new thicker sleeves, or just run with the stock ones, i would be at 84mm

5

nvm u just answered my question lol

6

i thought GSRs have a 81mm bore?

7

they do, im boreing it, i couldnt find a 81mm piston in the 9:1 range

edit: nvm, i suck at searching lol

would there even be much of a power difference between 84mm and 81mm? the pistons are the same price

8

http://www.tunertoys.com/CP_PISTONS_B18C1_GSR_81MM_9_0_1_p/cp-sc7010.htm

9

ninja edit lol :wink:

10

Well with more displacement you’ll make more power…how much more? I’m not sure lol…I’m sure Toda will chime in. He really knows his stuff :tup:

:edit:

lol @ ninja edit

11

lol at 9s being low compression.

I am around 8 flat.

12

x2

I think there was an integra for sale on here that had a 9:1 ratio, it was N/A. I believe it was a LS/VTEC.

13

its low relative to slow n/a hondas that make like 130wheel :frowning:

14

well keep it slow and N/A until you boost it. Break the engine in, save yourself $$ from driving slow and avoiding tickets lol.

15

^^^ fuck that break it in how you’re going to drive it.

Small torque difference with bigger bore and no don’t bore your block to 84mm no need for it.

16

last i checked the largest bore on a b18/b16 was 82 or 83. im pretty sure if you want 84mm you need a b20 block or a sleeved block.

17

+1 *2

Boost helps seat rings.
Boring produces negligible gains in a boosted 4 cylinder.

18

Then my car will sit til i get another 3-4k :frowning:

i think you’re right, if it was 84 i was gonna do sleeves, the walls would be way too thin, but i think ill just run stock, seems like a waste of money for what im doing,

19

83 is the largest u CAN go on stock sleeves but no one is that ballsy haha…shit I’d be scared w/ 82 on stock.

the reason why ppl punch the bore out to 84 or 84.5 or 85mm is because they are installed sleeves anyway, and its no big deal to just get the sleeves bored out at the same time, save on machine work etc…and its free power to step up 3-4 mm from stock.

power diffs are not that much, but that depends on the setup, and for the 400 hp level, it wont matter, you’ll hit it regardless, whatever bore you are.

also, if you dont see an off the shelf piston application, u can always contact them and get a custom piston to your specs if you choose, its not all that much more expensive.

20

how many times have we gone over this you moron?