I am building an R motor with JUN III head, and was wondering if any of you were running 13:1 or greater compression. I really wanted to go 15:1, but everyone tells me 12:1 is high enough.. so I'll compromise and go 13:1, I'm just wanting to see what steps any of you have taken with this high compression NA motor route.

 

Do you have any idea what it takes to get 15:1 outta a 87.2mm stroke?

hahah

Suprdave

 

you really wanted 15:1 CR??? for a street motor???

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Suprdave &raquo;</TD></TR><TR><TD CLASS="quote">Do you have any idea what it takes to get 15:1 outta a 87.2mm stroke?</TD></TR></TABLE>

care to explain??? I'm a n00b

 

im not the brightest crayon in the box, but i have never seen anyone run a 15:1 motor on the street.


Modified by andrewasf77 at 5:05 PM 5/25/2003

 

ctr pistons in a jdm r motor with the head milled 20k...According to my calculations I believe its around 12:8, thought SGT explained to me that it was more like 13:1, hope this helps! Im also running the J&S.

 

I am running 14.5:1 CR on my motor... basic setup as follow:

- ENDYN Rollerwaves (14:1)
- Decked block and Milled head
- 85mm bore
- PowerFC Standalone and 94 oct

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by advanracing62 &raquo;</TD></TR><TR><TD CLASS="quote">I am building an R motor with JUN III head, and was wondering if any of you were running 13:1 or greater compression. I really wanted to go 15:1, but everyone tells me 12:1 is high enough.. so I'll compromise and go 13:1, I'm just wanting to see what steps any of you have taken with this high compression NA motor route.</TD></TR></TABLE>

damn crazy guy here.. build block bore and sleeve 85mm with 13 compression u can put down like 240 + i blieve.. it's g@y.. 15 will be ownage on the street

well but if it's not daily drive or it's only for drag... why not turbo ???

 

hey have u ever ran ur car at the tracks?
what did u run?
most recent please.
later.

 

This car will/is becoming a track only car. That's why I want to run high compression. I will be drag/SCCA/and HPDE. So basically, this will be an all around car. I know that the high compression will be a bitch for the SCCA events, but eh... it's gonna be fast and fun.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by AutoMan &raquo;</TD></TR><TR><TD CLASS="quote">hey have u ever ran ur car at the tracks?
what did u run?
most recent please.
later.</TD></TR></TABLE>

I have a B16 with JUN III cams.. stock bottom and stock compression... heck the head hasn't even been worked and I put 13.5 @ 99.8 at 2700ft.

 

talk to Erick at 310-320-5788 http://Ericksracing.com he can provide you High CR pistons up to 15.1CR if you want , but you will need to run more then c-12 to run that type of CR

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Suprdave &raquo;</TD></TR><TR><TD CLASS="quote">Do you have any idea what it takes to get 15:1 outta a 87.2mm stroke?

hahah

Suprdave</TD></TR></TABLE>

I am not seeing the corelation between the 87.2mm stroke and compression here?
Correct me if Im wrong, but couldnt you get high compression pistons, mill the head, mill the block to get your desired compresin ratio?

 

Think of it this way. The same piston in a motor that has a larger stroke will have a greater comp ratio. That is why b16a pistons in a b18 block yields a higher comp ratio than in a b16a block. When you come to the realm of 15:1 compresion, this is a serious motor and a stroke of 87.2 is relatively small. With that stroke you'd need a piston that woiuld basically fill the combustion chamber almost completely. This would leave the only room for combustion to take place is in the valve reliefs and this would also split the mixture into two seperate groups, located in the intake and exhaust valve reliefs. Splitting the mixture is not efficient and will lead to rich and lean spots and detonation. Oh and this is also assuming a bore of 81-82mm. A larger bore would make running that comp ratio a little more feasible with that stroke.

 

get a diesel engine...you can run 25:1 compression on those

Actually, Look for JDM_DOHC_SIR; he runs 13:1 compression on his b18c CRX...


Modified by MiraiZ at 5:30 PM 5/27/2003

 

My first daily driver ran 19:1 or so.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Splat &raquo;</TD></TR><TR><TD CLASS="quote">My first daily driver ran 19:1 or so.</TD></TR></TABLE>
is this sarcasim?
if not lets get some info
(better not be a damn deisel...)

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by hybrid_KJ &raquo;</TD></TR><TR><TD CLASS="quote">Think of it this way. The same piston in a motor that has a larger stroke will have a greater comp ratio. That is why b16a pistons in a b18 block yields a higher comp ratio than in a b16a block. When you come to the realm of 15:1 compresion, this is a serious motor and a stroke of 87.2 is relatively small. With that stroke you'd need a piston that woiuld basically fill the combustion chamber almost completely. This would leave the only room for combustion to take place is in the valve reliefs and this would also split the mixture into two seperate groups, located in the intake and exhaust valve reliefs. Splitting the mixture is not efficient and will lead to rich and lean spots and detonation. Oh and this is also assuming a bore of 81-82mm. A larger bore would make running that comp ratio a little more feasible with that stroke.</TD></TR></TABLE>
thanks
great explanation

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by hybrid_KJ &raquo;</TD></TR><TR><TD CLASS="quote">Think of it this way. The same piston in a motor that has a larger stroke will have a greater comp ratio. That is why b16a pistons in a b18 block yields a higher comp ratio than in a b16a block. When you come to the realm of 15:1 compresion, this is a serious motor and a stroke of 87.2 is relatively small. With that stroke you'd need a piston that woiuld basically fill the combustion chamber almost completely. This would leave the only room for combustion to take place is in the valve reliefs and this would also split the mixture into two seperate groups, located in the intake and exhaust valve reliefs. Splitting the mixture is not efficient and will lead to rich and lean spots and detonation. Oh and this is also assuming a bore of 81-82mm. A larger bore would make running that comp ratio a little more feasible with that stroke.</TD></TR></TABLE>

i had to read that over twice to start understanding it!

 

I was planning on running a deck plate it going to 15:1. Realistically, I don't think it's going to happen with this motor due to time constraints. Thanks everyone for their insight!

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by B18C_DC2 &raquo;</TD></TR><TR><TD CLASS="quote">
is this sarcasim?
if not lets get some info
(better not be a damn deisel...)</TD></TR></TABLE>

It was a damn diesel

Is 19.1 even possible with a gasoline engine?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by advanracing62 &raquo;</TD></TR><TR><TD CLASS="quote">This car will/is becoming a track only car. That's why I want to run high compression. I will be drag/SCCA/and HPDE. So basically, this will be an all around car. I know that the high compression will be a bitch for the SCCA events, but eh... it's gonna be fast and fun.</TD></TR></TABLE>

Then make the car reliable and learn how to drive.

 

.RJ - Have you ever made a post that helps someone out? I sure as hell have never seen one.

 

Thats probably the best piece of information he could recieve if he wants to autocross and/or do HPDE events.

 

I was running 12.8:1 compression until recently when I had an Eagle rod snap on me.

I was running Endyn Rollerwave(wiseco) pistons 12.8:1
Eagle rods with stock stroke

I also ran Hondata, which with 15:1 compression you'll definitely need, or at least some form of stand alone. If you run race gas all the time, you can try and put your timing close to 16 degrees, on pump gas, you'll be lucky if you can even run 14 degrees, if you can run pump at all....

That's more compression than you need, I run the Toda Spec-C cams which are pretty similar to the Jun Type-3 cams, and Toda recomends 12.6:1 compression.

On top of that, if it's gonna be a road race car, reliability is more important than HP, it would really blow to kill a motor after only a couple laps.... Anything over 13:1 is a little much...but I guess what ever floats your boat.

Later,
Aj

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Splat &raquo;</TD></TR><TR><TD CLASS="quote">

It was a damn diesel

Is 19.1 even possible with a gasoline engine?</TD></TR></TABLE>

I've seen some N/A Race cars on meth in the 18:1 range, I dunno if i've ever seen a 19:1 car though.