I'm redoing my block and trying to dicde what to do. My block is sleeved

My block is sleeved & bore to 85mm w/eagle rods ,Crank is balance & blueprinted.
just trying gain some opinions to help my disicion

 

You can run higher ratio with big cams and a light race car.A heavy street car with small cams is more limited.If this is a street driven car be conservative.You will make less power having to retard the timing a bunch than running a little less compression.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by NJIN BUILDR &raquo;</TD></TR><TR><TD CLASS="quote">You will make less power having to retard the timing a bunch than running a little less compression.</TD></TR></TABLE>

quite a misconception there...

 

Not really.

 

too many variables to just state it downright... so its a misconception

 

i ran gsr w/ rev flat valves, p73 pistons, hitting agound 11.8 CR...
had pinning coming out at the hills or fwy ramps...
used 101 gas and bye bye pinning...

i should confess it was so loud i thought my axles were poping out...

 

despite what xyzalvarez has stated, i have found the "sweet spot" to be around 11.5-11.7

 

how about 12:1 can i get away w/ pulling out 2 degrees timing and a colder plug. I only got access to 91 octane

 

on 91 no... i would greatly go against it...

 

12:1 on 91 aint gonna happen. ur gonna have to pull so much timing out of it that ur not going to make any power.

 

thanks for your reply's

 

You should invest in some endyn pistons. Help prevent predetonation. just my 2cents.

 

Why do they do that?

 

Should point out that elevation has so much to do with detonation.
I get away with alot at 3400ft. My buddy has supercharged rsx at 9psi
with 11.4:1 on shell 91.
When he goes to lower elevations though, he has to get 94octane.
You only need to go high compression with really wild cams. Then it pays big dividends. For a street bruiser with mild cams, doesn't seem worth it for the hassle. Just go 11.5:1.

 

well i run 12:1 on (3 tho and its my daily driver tuned and runnings like a champ

 

what octane are you running, and how much did you retard your timing?

 

I have roughly 12:1 and only have 91 octane living at about 3600 ft. above sea level.
Street tuning A/F's and running base P30 timing as of now. Haven't really ran it hard yet but once to 8k for ring seating and it seemed to do alright.

Waiting for free dyno time on a mustang dyno for timing tuning.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by xyzalvarez &raquo;</TD></TR><TR><TD CLASS="quote">i ran gsr w/ rev flat valves, p73 pistons, hitting agound 11.8 CR...
had pinning coming out at the hills or fwy ramps...
used 101 gas and bye bye pinning...

i should confess it was so loud i thought my axles were poping out... </TD></TR></TABLE>

Damm where you tuned and what injectors,fuelpump, regulator ???

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by cartune network &raquo;</TD></TR><TR><TD CLASS="quote">12:1 on 91 aint gonna happen. ur gonna have to pull so much timing out of it that ur not going to make any power. </TD></TR></TABLE>

depends on the cam choice and the amount of valve overlap.

valve overlap lowers dynamic (true) compression.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by NJIN BUILDR &raquo;</TD></TR><TR><TD CLASS="quote">You can run higher ratio with big cams and a light race car.A heavy street car with small cams is more limited.If this is a street driven car be conservative.You will make less power having to retard the timing a bunch than running a little less compression.</TD></TR></TABLE>



more weight = more load = harder working engine

 

so by increasing overlap by advancing EX and retarding IN gears by say 1 or 2 degrees, can i get away with 12.1 CR w/ bc3 cams on 91 octane until i get a tune?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by all-mtr-teg &raquo;</TD></TR><TR><TD CLASS="quote">so by increasing overlap by advancing EX and retarding IN gears by say 1 or 2 degrees</TD></TR></TABLE>
That would reduce overlap. Advancing the intake cam and retarding the exhaust cam will increase overlap.

 

that also lowers valve to piston clearance right?


Modified by all-mtr-teg at 9:54 PM 9/4/2007

 

[QUOTE=98vtec]

depends on the cam choice and the amount of valve overlap.

valve overlap lowers dynamic (true) compression.

Some times, unless the cams increase the efficency of the motor, or raise the torque, then the dynamic compression goes up.
Overlap only changes specific rev ranges the engine runs in. Less efficent @ 3000 but more efficent @ 6000. Someday, someone will figure out why we have VTEC cams, and variable cam timing, and VTEC, on K motors, but not in the near future on here.

 

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

quite a misconception there...</TD></TR></TABLE>

not so much, most factory honda ignition maps are pretty close to optimal for the typical HT all motor street engine. pulling a decent amount of timing to make a high CR engine drivable will really hurt power output and give you some pretty high EGT's. ive seen this firsthand on some basemaps (albeit more with turbos).

most people arent really asking the right question either. instead of asking what is the optimal compression for such and such build they are simply asking whats the most i can run on the street w/pump gas. the typical street cam is some variant of a jun3 cam (ie skunk2 blox whatever) and those run fine on mid 11:1.

my .02

 

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

most people arent really asking the right question either.

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

there u got to the point... most people dont even know how to use a compression calculator... they use all generic numbers and hit calculate...

last time reading here i found a guy that claimed 1 full point in comp from flat faced valves

its like people that tell me they got 13:1 pistons on a b16... YEAH RIGHT

and thats why i said a misconception. If u dont have a real understanding bout the concept of actual static compression, timing/timing map discussion is not going to help you much.


Modified by Chris Tune at 10:58 PM 9/4/2007