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[lrs110]

Hey guys, question for all you running modified 110s, at what point does compression negatively effect daily street-ability?

S&S has pistons at 10.6:1 and fuel motos big bore kits start at 10.5:1 and go up from there. 10.5+ just seems a little high but a lot of guys seem to be doing it. if the street manners were good, id be tempted to do the S&S 10.6:1 pistons with the S&S 585 cams

i ride every day for fun/commuting, with 1 or 2 long trips a year.

[johnsachs]

10.5 , 10.6, not unreasonable for 585 S&S cams in a 110". As far as compression negatively affecting the build, depends on the combination.
Remember, it's all in the tune. 
John

[North Star]

My GMR 113 build is 10.8-1 with 215 ccp. It is tuned by a reputable tuner with 91 octane fuel not 93, as 91 is what is most available where I live.

I did a 3000 mile trip out west this summer- Beartooth pass and lots of mountains in BC and Alberta, 2 up and loaded up.  Always found at least 91 octane gas. No pinging or any driveability problems with my build and higher compression

[lrs110]

Thanks guys! that really helps!

[Scott7d]

I'm sure there are other factors (my cam swap maybe?) but mine starts easier and has lower CCP with added compression. But, it's still pretty modest at 10.2, not 10.5+ like you were asking about. Hope that helps.

[110tHunDer]

I am running 11.0:1 static with my T-Man 110" build.  Would have to go back and look at where the ccp ended up at again, but it's somewhere in the 215-220 range if I remember right.  I also tuned using mid-grade fuel but have run a couple of tanks of 87 through it just to see if I could.  No problem.  Tuning is definitely key.  The motor has 15,000 miles on it now.  Runs great and is very mild mannered.  Keeps pulling all the way to redline, which it sees quite often. 

[prodrag1320]

good tune or not,215-220 is a bit much for a touring bike that actually gets toured on

[110tHunDer]

So, maybe it's less ccp than my memeory recalls.  Gonna be 50!next month, ya know.  But it ain't been 15,000 miles of bar hopping. 

[Yellow09SERG]

Looking to be around 195 with a 24d cam

[FLTRI]

IME 195ccp is a good limit for heavy FLH bikes.
If you can run 87 octane without issues you should run it. More power.
That said, most folks run under 91 octane simply due to 87 octane leftovers in the pump hose from the last vehicle that used 87.
Just 8oz 87 octane with each fill up. Pretty soon you are running somewhere between 87-89 octane at best.
Always look for separate hoses for each fuel grade. You minimize the watering down with 87 octane because most of it is in the 87 hose.
Bob

[FLSTFI Dave]

My 13 SERK had 10.8 compression the first build with a 259E cam.  It did not like anything less than 93 octane pure gas.  It was a bit much for touring as I always had to carry octane booster.  Still had to worry about detonation with ethanal gas and octane booster.

The bike now has 11.4 compression, TW-9B-6 cam and I do not have to use octane booster, or pure gas.  I have not had it detonate yet and have 5K on the build.  Not sure I would tour on it west of the Mississippi, but no problem east of it.

Compression you can run has a lot to do with the cam choice and its timing and duration.

[coloradotom]

Canada always has good gas. Europe has race gas. That is not always the case in the states. You will find remote places still selling only 81, especially at elevation, so the octane boost is a must.

[GMR-PERFORMANCE]

I do not feel 210 is too much but then again the CVO is in that  area to start with stock  . It is in the tune. I have tuned bikes that have 215 on 87 octane . With the right timing curve no issues. Just did one for a guy that lived in NM at 5500 feet. Don provided the parts to him and he wanted it to be at a CCP of 190 ish there!!!! so once at sea level or close it had another 20 CCP added into it. along with a SE 585 cam. Tuned out well made good power. Sure the timing tables where a bit more work but no issues .
Don could tell you more about that build than I can maybe he will chime in

[HD Street Performance]

Canada always has good gas. Europe has race gas. That is not always the case in the states. You will find remote places still selling only 81, especially at elevation, so the octane boost is a must.

If you are at 9000 ft 82 octane may be fine, there is 21.4" air pressure VS sea level average of 29.9". Cylinder pressures are dramatically lower.
Sooner or later you will be at sea level and octane requirements are greater. I suggest that guys that spend most of their time at high elevations keep the cam timing a little shorter than they may typically see in a lot of builds, keep the ports on the smaller size at choke point(s) (+velocity), set the static compression a few tenths higher than typical, and have the bike tuned at sea level with premium 91 octane. Tuning at high elevation is problematic when you can't achieve 100 Kpa pressure at WOT. Many VE and timing cells can't be properly fixed. When tuned at sea level the bike will compensate properly going up or down, provided there is a reboot like a gas stop.

[FlaHeatWave]

If you are at 9000 ft 82 octane may be fine, there is 21.4" air pressure VS seal level average of 29.9". Cylinder pressures are dramatically lower.
Sooner or later you will be at sea level and octane requirements are greater. I suggest that guys that spend most of their time at high elevations keep the cam timing a little shorter than they may typically see in a lot of builds, keep the ports on the smaller size at choke point(s) (+velocity), set the static compression a few tenths higher than typical, and have the bike tuned at sea level with premium 91 octane. Tuning at high elevation is problematic when you can't achieve 100 Kpa pressure at WOT. Many VE and timing cells can't be properly fixed. When tuned at sea level the bike will compensate properly going up or down, provided there is a reboot like a gas stop.

Very informative  Thanks for the Post!!