can you run 91 octane fuel with a 10:1 compression piston?
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Registered User
can you run 91 octane fuel with a 10:1 compression piston?
Registered User
yes
Registered User
what is the highest compression that is safe to run with 91 octane fuel? and will it show a big differnce on a 400ex that has a 9:1 compression stock?
HONDA FOREVER
11.1:1 is the highest for an air cooled engine
12.1:1 is the highest for a liquid cooled engine
I just got a 10.8:1 je put in mine and it ran fine on 93 but being right at the border of needing race gas I will try to run at least a 50/50 mix when possible.
04' 416 EX
JE 87mm 10.8:1 PISTON
450R CARB
JETTING: 198 KEIHEN JET MAIN
48 KEIHEN PILOT
FUEL SCREW 3 TURNS OUT
E-CLIP ON 3RD NOTCH FROM TOP
HOTCAM STAGE I
FMF POWERCORE 4
FMF POWERBOMB HEADER
REV BOX
PRO ARMOR KILL SWITCH
K&N AIR FILTER w/ OUTERWEAR
K&N POWERLID w/ OUTERWEAR
PRO TAPER BARS
DG "FAT" V PRO-SERIES BUMPER
DG "FAT" NERFS
UM AIR SCOOPS
FMF SHOCKCOVERS
BLUE LED TAIL LIGHT
ITP SAND STARS II'S ON C-SERIES POLISHED WHEELS 20"
CHENG SHINS---STUDDED 20"
DICK CEPEK SPIDER-TRAC 22"
MAXXIS RAZR II's FRONT AND REAR.
07' SUZUKI DR-Z 400-------STOCK
84' HONDA 200 S ATC------STOCK
22" WOOLY BOOGERS
Registered User
Popular opinion/experience indicates that your OK with 11:1 on premium pump gas. In my opinion 11:1 with 91 is iffy. 11:1 may be ok with 91 but you might also get some detonation under certain conditions.
I have a 10.8:1 JE piston and a rev box that advances the ignition timing a little. 91 is the highest octane available at the pump in my area. I'm getting a small amount of detonation under high load, high rpm conditions.
This is on a new build for me so I'm still experimenting on what it will take to eliminate the detonation. I'll likely start running a pump/race gas mix.
Higher compression pistons do make a significant difference vs. the stock 9.1:1 compression. The more compression the bigger the difference.
ETA: I second what JSmith said.
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