Whats the compression Ratio for CTR pistons in a B18c1 block with b16a head? Or would I be better of going with JE 12:5:1

 

12.2:1.

 

i forgot, the b16 head should yeild the same compression numbers as a type r head with the same pistons right?

 

Yup

 

b16a head volume 42.7cc

b18c5 head volume 45.5 cc

wanna reconsider your "Yup" answer?

 

How does the Type R head have more volume? It's the exact same head.

 

I was wrong , see my last post



[Modified by Tbone, 9:47 PM 12/20/2001]


[Modified by Tbone, 12:38 AM 12/23/2001]

 

Same casting but the r head has some bowl work done and different shrouding of the valves.

 

Nope. Both are 42.7
LS is 45.0

 

but the difference between the heads is the ITR head has a little P&P job...oooooo

 

12:1 CR with b16 head

 

I'm not trying to argue or prove I'm right. I just try not to pull info out of the air from nowhere and want to let you know where I got my info from. The Helms manual didn't list these in the Standards and Service Limits, Cylinder Head/Valvetrain section. Since Mike K is an Acura rep then he has all the specs from the tech manuals at his fingertips and more likely off the top of his head: I trust what he says. Where did I get my numbers from?

You know the Speedvision Touring Car series is very tight with the rules and specs. The ITR must meet stock engine tolerances or they are considered to be cheating. The ITR was not allowed any headporting except valve seat and bowl blending work. In fact, the ITR was so good that they had to place a restrictor at the TB to reduce the bore to 56-57mm during this year's series. They were not allowed CR increases from aftermarket pistons or cams or weight reductions like the Civics.

So if you go to the Speedvision online rule book for competitors which is made available to all:
http://www.speedvisionwc.com/competitors/vts.html

The stock spec they check for the ITR head volume is listed there. They list the head volume to be 45.5 cc on page 3 of 7 (Adobe Acrobat pdf file).
http://www.speedvisionwc.com/competi...-integra-r.pdf

Unfortunately they do not list the Civic Si head volume given the more liberal rules for the Civic. This is why Taz went from the ITR to the Civic Si I believe (**** they could run 12.5:1 CR)!

I got the head volume for the b16a from the appendix in Joe Pettitt's
Honda Builder's Handbook Volume 1.

Hope that clears up my sources of info.

cheers





[Modified by Michael Delaney, 10:54 PM 12/20/2001]

 

what about ctr pistons in a b18b?

 

The bowls arent in the combustion chamber. The valve faces are the same as well.
The stems were deshrouded. This also doesnt affect the CR.

I dont see how they could be different since its still a P30 Casting.

Tuan: This wouldnt be the first time a rulebook has been wrong.

B18B CR would be around 12.8:1 or so.

 

I was refering to his statement that the heads were exactly the same. I should have quoted that part, sorry.

 

I meant the castings are the exact same. Everyone and their grandma in this forum knows the difference between a B16a head and a Type R head. I was down at Portflow talking with Tom a while back and he told me that the heads themselves are EXACTLY the same with the exception of the bowl blending right before the valve seats. This would have no effect on compression ratio. He even showed me a stock B16a vs. the Type R head side by side and there was no CC work on the Type R head. And as Steve said, the valve stems are deshrouded, not the combustion chamber.

 

You know what it probably is....

If you notice, the ITR intake valves due to the sharper seat angle, sit farther into the
seat than std b18c/b16a valves. Thats probably where the extra volume is
coming from. Thats the ONLY DIFFERENCE I can think of.

 

Ok I cc'd a brand new out of the box r head today and to correct my earlier post it's definetly not 45.5. Now what I got was around 43.3cc on the nose but there's also a margine of error cause of my shakey hands(it's 30 deg in the garage today) and a drop or 2 of fluid dripped out of the burette so I guess it really is right around the 42.7 of a b16 head.

 

thanks for taking the time to check the numbers Tom.

I guess the tech inspectors in the speedvision series either use the wrong number or they lower the ITR CR even more in the series with this head volume.

cheers