how much compression are you guys running on pump gas........i'm tryin to figure out if i can run around 12.8-13.0 on pump gas tuned on hondata?

 

me thinks not. alot of people on here are going to flame for even thinking 13.0:1 on pump, most of the headporters (omniman/maxcfm) are more into 11:1 or lower for a street motor. but they are also producing 210+whp out of smaller domes

wonder what omniman could create with 12:1 compression on one of those crazy motors he builds?!

 

Weve run as high as 13's on pump gas... I would personally would say go no higher than 12.8:1 and suggest 12.5:1 or under but to each his own... A higher CR is possible on pump gas though... I cant stress enough how IMPORTANT tuning is on a 12.0:1+ motor... Tuning is so key to a motor like that...

 

ive heard of 12.5 with fine tuning thats about it. But if u can get a 13.0+ i wanna see the results.. GL to ya

 

i am running pump gas now on 12.6 since i got my new fuel pump an hondata

 

If you are going to run on pump gas at 12.5 to 1 or higher please use toda cams. For everyday driving becasue of their bigger duration primary lobes you will be relieveing the cylinders of compresion. Big cams lower dynamic compresion, static compresion is the same but the longer those valves stay open the more presure you can bleed off and the more toelrant to pump gas the set up will become. With profiles like JUN and even skunk where the primaries are nto much bigger than a stock ITR cylinder pressure will be throught the roof at normal city driving rpm's and that is a fast track to a hole on a piston on pump gas.

 

i'm gonna be running some like 2 year old crowers.....the 63403's and i'm gonna have type r head done by rlz i think........and i guess maybe around some 12.5 je's in my gsr shortblock wich will be at least 84mm.........i wanna stick with the stock valve size but have the headed fully p&p.......could i run 12.5 safely on pump gas, or am i gonna have to maybe make it a little lower........i wanna run like low 12's on this setup......and i think i'm gonna need all the compressoin i can get.........

 

I wouldent pass 11.5
but hey thats just me. some people run 12.1 some people even higher but thats them
i think 11.5 is ideal and as high as i would go with 91 octane

i am curentely building my ls vtec and i'm going to use p30 pistons to get 11.5 cr i was thinking about useing ctr's but that would be 12.1 cr with in my opinion is too high with 91 octane

 

I have run 12.6-1 on 93 octain on a daily driver

 

12.5-1 with your crowers will be fine on 91 octane so long as you meet a few critereia. Hondata is a must. Efficient fuel pump and injectors. And the most important thing no more than 14 degress of timing BTDC. At the track mump it up to 18-19 with your 100 octane race gas and you will be good to go.

 

i'm running a walbro pump, prelude injectors, aem reg, rail..and i have an msd and i'm running like 23deg right now on a b16 a with ctr pistons and r head and r cams........no detnation and it runs strong......but my other shortblock will be run on delphi's and hondata, just tryin to figure out what to do with my new setup, cause i wanna be able to hit like 12.0.......i wanna be on the ragged edge of a race motor

 

Are you running 23 degress of timing at BTDC as in 5 whole degrees past the red mark on your crank pulley? Maybe you are talking about total timing advance with your ECU on the top end. But 23 degrees of timing at BTDC would be harming performance. To much advance does not take advantage of full compresion of gas and air and will hurt performance, and cause some major major detonation, as it will be igniting the mixture before the piston is anywhere near the top of its stroke, and that will create an explosion that is pushing down against a piston that is in its upward stroke. Coutneractive to power and dangerous for a stock cast piston top. Just my thoughts on that scary *** 23 degrees of ignition advance.

 

yea i'm runnnig 23deg......it doesn't detonate, and i understand your explanation, but the more timing you can get into a motor......obviously before it/s detonating and doing more harm then good and robbing horsepower the faster it will be.........a couple years back, i had a stock sir 1 with a msd, chipped ecu, and a set of 00 si cams.........it had ihe.......and it ran 13.80's on nitto drags in my 89 si hatch, full interior.......and that car was running 28deg of timing, stock everything just msd and chipped ecu.....

 

im running P30s with spoon headgasket on stock b18c5, its good for around 11:6:1-11:8:1 compression. im running on 93octane and runs fine, then again....im still breaking in my motor also.

 

im planning on running 12.5ish:1 on my daily driver...JUN 3 cams, hopefully ill have money for tuning...need a job

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by TwistedHatch &raquo;</TD></TR><TR><TD CLASS="quote">i'm gonna be running some like 2 year old crowers.....the 63403's and i'm gonna have type r head done by rlz i think........and i guess maybe around some 12.5 je's in my gsr shortblock wich will be at least 84mm.........i wanna stick with the stock valve size but have the headed fully p&p.......could i run 12.5 safely on pump gas, or am i gonna have to maybe make it a little lower........i wanna run like low 12's on this setup......and i think i'm gonna need all the compressoin i can get.........</TD></TR></TABLE>

It'll be fine. That's exactly the setup I'm running right now. 85mm JEs w/ 4.8cc dome and crower 63403s. I swapped valves to flat skunk2 ss valves. Static c/r is actually around 12.2:1 and dynamic compression with those cams(46 degrees ABDC) is 11.43:1. Cylinder PSI is 280-285@1000ft elevation. There's enough clearance to go with a thinner head gasket if a bit more compression is desired provided you don't go nuts with the cam gears. I'm afeared to go past 3 degrees +/- on the gears with stock gasket.

 

anyone else?

 

Ran 14.1+CR over 2 years ago, on pump gas..fully built motor, with only a chipped p28 and a VAFC, never had a problem with pinging. Was equipped with the J&S system however, but it never really did what it was supposed too, just there for saftey.

 

I would keep it around 12.3-12.5:1

 

thats what i was thinkin, like 12.5