Never knew how to do this

[jamesA]

Ok so I've sourced this b16 block to use for my turbo build project.

I want to have it bored to 1.9ish and then have it sleeved so the displacement of the bore will equal that of 1.8Ls I want to get the same r/s ratio and i don't want to stroke the motor, so i'll have a b16 stroke, but a b18 bore. I was thinking about sourcing this b18c1 head someone had for sale in the market; parts thread.

So I'd have an overbored Si block with a (ported and polished at a later date) GSR head.

Question One: Can someone give me the simplified manner of figuring out the displacement so that I can write it down and memorize/use it for later need-age (i just made up a new word)

Question Two: would this be a decent setup for a turbo? I would think I'd be raising my compression ratio by doing this, but I'm not sure because of boring the cylinders out by 200 CCs.

Thanks.

 

[MikeBergy]

This is exactly what I am doing, only going the sky-high cr NA route. In order to atain the same displacement of a ls, you need to bore it to like 87mm, which isn't very good, especially for a turbo motor, because you will be making the walls too thin. And I am talking the wall of aftermarket sleeves- if you tried to bore out a stock b16 sleev this much, you'd have invisible walls or transparent walls. You get my point. Here is the way to calculate the volume of the motor.

PI * Diameter^2 / 4 * Stroke * # of Cylinders (in your case, 4).

This is always a good conversion factor; 1liter = 1000 cubic centimeters, or cc's
another good one is 2.54 centimeters = 1 inch

Compression Ratio = (Total Volume of Cylinder (computed above)) / (Chamber Volume - Piston Dome Displacement)

You can usually get someone who knows the volume of the the combustion chamber for the standard heads, ie, gsr, b16a, ls, etc..., or a machine shop can cc a chamber for you if you have done work on the chamber for whatever reasons. The dome displacement is usually given in the piston specs when you buy them.

 

[jamesA]

PI * Diameter^2 / 4 * Stroke * # of Cylinders (in your case, 4).

This is always a good conversion factor; 1liter = 1000 cubic centimeters, or cc's
another good one is 2.54 centimeters = 1 inch

Compression Ratio = (Total Volume of Cylinder (computed above)) / (Chamber Volume - Piston Dome Displacement)

Wow...ok Lemme see if I can get some of this filled in then...


3.14*Diameter^2/4 * stroke (77.4) * 4

Diameter of What, the cylinder?? So it'd be 81, right?

^2 = squared??


3.14(81^2)/4*77.4*4=1594559.196

That doesn't sound right... I'm lost on the bore side because the c1 and a2 have an 81 mm bore...so that's throwing me on a tangent here.

 

[MikeBergy]

Here is an example

Stock b16a; 8.1cm bore , 7.74 cm broke, 4 cylinders

3.14*8.1*8.1*7.74 = 1595.37 cc = 1.595 liter, round up to the 1.6 liter mark

w/ 85mm bore

3.14*8.5*8.5*7.74 = 1756.83 cc = 1.75 liters, which is where I'll be sitting.

 

[NotUrAverage_Si]

Originally posted by MikeBergy@May 11 2004, 05:04 PM
In order to atain the same displacement of a ls, you need to bore it to like 87mm, which isn't very good, especially for a turbo motor, because you will be making the walls too thin.

86mm and up are strongly recommended for N/A applications.

 

[jamesA]

So if I bore to say 86 and then put sleeves in, would that drop me to like an 84 mm bore?? I want to get this thing overbored and throw in iron sleeves so I can hold higher boost than the Edelbrock kit will be able to make (max is 6-7 psi on their wastegate)

 

[MikeBergy]

They pretty much cut the old cylinder walls out of the block, and put new ones in. They are thicker, and need to be bored after they are installed. Color the old cylinder walls gone. Good Luck bro.

 

[jamesA]

Ok so now that I got the first equation figured out... I need help on the second one...

I want to bore it to 84mm... .sooo....

3.14*8.4*8.4*7.74=1731.194 cc's or just over 1.7L

Now...

Compression Ratio = (Total Volume of Cylinder (computed above)) / (Chamber Volume - Piston Dome Displacement)

Compression Ratio =(1.7) / (Chamber Volume MINUS Piston Dome Displacement)

Edit: should I stick in 1731.194 instead of just 1.7?

Say I'm using a stock GSR head and stock B16a2 pistons...any help here??

 

[K2e2vin]

Originally posted by NotUrAverage_Si+May 11 2004, 07:26 PM-->

MikeBergy

@May 11 2004, 05:04 PM
In order to atain the same displacement of a ls, you need to bore it to like 87mm, which isn't very good, especially for a turbo motor, because you will be making the walls too thin.

86mm and up are strongly recommended for N/A applications.

i think 85mm or 86mm pistons is the biggest they make for an overbored b-series. i guess larger ones have to be custom ordered.

 

[Bl6CRX]

have you checked out the compression/displacement calculator here http://www.c-speedracing.com/howto/compcalc/compcalc.php

 

[jamesA]

Originally posted by Bl6CRX@May 12 2004, 01:43 AM
have you checked out the compression/displacement calculator here http://www.c-speedracing.com/howto/compcalc/compcalc.php

No. but good link. it says with my setup my compression would raise from 10.4:1 to 11.0955.

So stock USDM B16a2 pistons are called PR3 pistons? Thats what I've been seeing this whole time and not knowing?

 

[MikeBergy]

Originally posted by revolution8k@May 11 2004, 10:32 PM
Ok so now that I got the first equation figured out... I need help on the second one...

I want to bore it to 84mm... .sooo....

3.14*8.4*8.4*7.74=1731.194 cc's or just over 1.7L

Now...

Compression Ratio = (Total Volume of Cylinder (computed above)) / (Chamber Volume - Piston Dome Displacement)

Compression Ratio =(1.7) / (Chamber Volume MINUS Piston Dome Displacement)

Edit: should I stick in 1731.194 instead of just 1.7?

Say I'm using a stock GSR head and stock B16a2 pistons...any help here??

Just make sure your units are consistent. Usually, on an aftermarket piston, they give a dome displacement in a certain number of cc , and usually that is how a combustion chamber is sized, so I'd say stick with cyl. displacement in cc, i.e. 1731.etc...Your CR shouldn't have units, just keep that in mind.

 

[jamesA]

Originally posted by revolution8k@May 12 2004, 12:32 AM
Ok so now that I got the first equation figured out... I need help on the second one...

I want to bore it to 84mm... .sooo....

3.14*8.4*8.4*7.74=1731.194 cc's or just over 1.7L

Now...

Compression Ratio = (Total Volume of Cylinder (computed above)) / (Chamber Volume - Piston Dome Displacement)

Compression Ratio =(1.7) / (Chamber Volume MINUS Piston Dome Displacement)

Edit: should I stick in 1731.194 instead of just 1.7?

Say I'm using a stock GSR head and stock B16a2 pistons...any help here??

Ok so assuming that website is right on all the piston dome displacement stuff, the PR3 has a 6.01cc Piston dome displacement and the GSR head has a 41.60 cc displacement...so the equation sits as this.

Compression ratio = (1731) / (41.60 - 6.01)
Compression ratio = (1731) / (35.59)
Compression ratio = I'm gettin some crazy number that makes no sense

What am I not seeing?

 

[MikeBergy]

Ok so assuming that website is right on all the piston dome displacement stuff, the PR3 has a 6.01cc Piston dome displacement and the GSR head has a 41.60 cc displacement...so the equation sits as this.

Compression ratio = (1731) / (41.60 - 6.01)
Compression ratio = (1731) / (35.59)
Compression ratio = I'm gettin some crazy number that makes no sense

What am I not seeing?

You are only supposed to use the displacement of one cylinder

(1731) / (4) = 432.75

CR = 432 / 35.59 = 12.1:1
That is assuming the above numbers for the chamber and pr3 piston displacement are correct. That CR is in NA race engine territory, do not use that setup with your turbo. Go with a less domed piston for sure.

 

[jamesA]

ah ok, just ONE cylinder. a'ight. that helps...

 

[katman]

Originally posted by revolution8k@May 12 2004, 01:52 AM
So stock USDM B16a2 pistons are called PR3 pistons? Thats what I've been seeing this whole time and not knowing?

Yes thats right, and as a side note, they are the exact same piston found in JDM 89-91 B16A engines.

If you want .2 points more compression, go for the JDM P30 B16A pistons (92-00).
US never got the P30 piston(s)

 

[wildbillhatchbac]

i ran the P30s in my ls motor with stock rods for 11.1 to 1 compression . . . . stock bore.

 

[posol]

a b16 will never be a b18, regardless fo stroking and boring.

the block casting it self is physically shorter than the b18's, and thus, will never be able to have the same rotating dimensions. if you want 1.9, get a b18 block to 84mm

 

[jamesA]

I would if Maasey didn't give me a killer deal on the B16...

 

[97CTR]

well then sell the b16 and use the money to buy a b18