hondavtec24

Greetings.
I'm going to put the repair size pistons in my B18C Spec98. I ask to give advice on pistons PR3 in this engine. What will be the compression ratio?
Is it necessary to somehow modify the connecting rod or piston?
Thank you in advance and I apologize for my English.

civic-steve-94

It all depends on what cylinder head you have there is a honda engine compression calculator I'll post the link. If you an all B18C engine the casting number should be p72 if you have a Type-R head then i believe its p73. Just input the data and it will tell you the compression ratio.


Honda B-Series Compression Calculator by ZealAutowerks

hondavtec24

I have the entire engine P73, Type R DC2 JDM. Calculators I tried to count, but they all for some reason show different data. Thank you.

The calculator you propose is from the very beginning. The compression ratio of the factory engine is incorrect.

jdblock

What crank did you use on the calculator?

You can always blueprint your engine and enter those numbers.

hondavtec24

Crank B18C
All components of B18C P73 calculator considers compression ratio 11.32
This is not reliable information

Compression ratio stock B18C-R JDM 11.1

jdblock

The calculator says "This calculator is intended for use as a general estimate of your compression only. Not all values are verified. "

Still an easy way to see how compression changes when you use different parts.

JRCivic1

The Zealworks calculator shows a compression ratio of 11.20 using stock sized pistons AND a head gasket thickness of .030" (which is the factory thickness, not .026"). The math is only as good as the data variables that you put in. These calculators are designed to give you a general idea of what it will be... not exact to the thousandth of a decimal.
I thought it was generally accepted that the JDM ITR engine was half a point higher in compression than the US version... and since the USDM ITR engine has a compression ratio of 10.6:1, that would suggest a JDM ITR compression ratio of 11.1:1 actually. The calculator gets you within a tenth or two...

Can you share with the forum the reason that you need the EXACT compression ratio, and when you find a calculator that provides the data results that meet your expectations, would you please share them here.

hondavtec24

Here is the calculator I found, it shows values ​​similar to the truth
Compression Calculator - Honda, Acura Tech Website, tutorials, tuning and HOW-TO's. Drag racing, street racing, road racing - C-speedR.com

civic-steve-94

If you input all of the p73 info in either calculator it shows 10.8. Which cylinder head are you selecting?

hondavtec24

In this calculator Compression Calculator - Honda, Acura Tech Website, tutorials, tuning and HOW-TO's. Drag racing, street racing, road racing - C-speedR.com

Block B18C1/C5
Head B16A/B - B18C5
Piston pr3 (USDM B16A)
Headgasket Thickness OEM B-series 3-layer
Piston-to-Deck Height OEM B18A/B/C1/C5 - B20B/Z
COMPRESSION RATIO 11.11

Block B18C1/C5
Head B16A/B - B18C5
Piston p73-00 (JDM B18C5)
Headgasket Thickness OEM B-series 3-layer
Piston-to-Deck Height OEM B18A/B/C1/C5 - B20B/Z
COMPRESSION RATIO 11.10

It's right?

the_unknown

Assuming the calculator is off by 2/10ths of a point in compression, what difference would this make to you? It doesnt make a noticeable difference in any way other than the number you are going to tell people so not sure why it is so important to be that exact. If you are looking for exact numbers to the decimal point you should be measuring the compression of your engine, not using a calculator, although again I am not sure what purpose this would serve. Static compression is just a reference point and is not meant to provide any hard data in any way. Dynamic compression is what truly matters in regards to knock (not sure why else you would need to know the compression ratio) but is tough to get numbers on.

As long as you are using factory or OEM style parts in applications that make sense, even a ballpark compression figure should suffice because you are not reinventing the wheel here. If your parts were all custom made and specced differently than the factory pieces then it may be of some value to know the approximate compression ratio..

Aside from hard-parking and telling your bros how you run 13:1 on pump 91 octane in your daily driver, I dont see why you would need to know this figure...