Sammy Posted November 10, 2009 Report Share Posted November 10, 2009 I have a stock port stock stroke setup. It has a coolhead w/ 19cc domes, +4 timing, v force 3 reeds, pods, and lrd rfx's. I compression tested it, I got 155psi per side on a dead cold engine. I've been using straight leaded 111 mixed 50:1 with Golden Spectro. I was wondering if I even need this much octane. Would it be ok to use 93 or would I need to blend in some 111 with the 93? Quote Link to comment Share on other sites More sharing options...
blowit Posted November 10, 2009 Report Share Posted November 10, 2009 I have a stock port stock stroke setup. It has a coolhead w/ 19cc domes, +4 timing, v force 3 reeds, pods, and lrd rfx's. I compression tested it, I got 155psi per side on a dead cold engine. I've been using straight leaded 111 mixed 50:1 with Golden Spectro. I was wondering if I even need this much octane. Would it be ok to use 93 or would I need to blend in some 111 with the 93? 91 octane or above. Mull Engineering Quote Link to comment Share on other sites More sharing options...
Sammy Posted November 10, 2009 Author Report Share Posted November 10, 2009 Thanks Mull... Would I be safe to add a little more timing. Perhaps 1-2 degrees more and still use the 93 octane or would I have to add a dash of 111 to it? Quote Link to comment Share on other sites More sharing options...
blowit Posted November 10, 2009 Report Share Posted November 10, 2009 Thanks Mull... Would I be safe to add a little more timing. Perhaps 1-2 degrees more and still use the 93 octane or would I have to add a dash of 111 to it? You are fine to add +4* with pump fuels on that setup. Probably could push a little more but would have to watch for detonation. Quote Link to comment Share on other sites More sharing options...
LIM_Whiteboy4life Posted November 10, 2009 Report Share Posted November 10, 2009 What you need to do is check your compression ratio, im runnin 19cc domes with .44 squish 180psi, and 10.2:1 compression. Think about it.... Stock banshee is 8.2-8.5:1 and requires 90+ oct. I would run 100 or more. Im running 110 because idk where to get 100 at the moment. My 2 cents spent.... Quote Link to comment Share on other sites More sharing options...
Rodneya Posted November 10, 2009 Report Share Posted November 10, 2009 What you need to do is check your compression ratio, im runnin 19cc domes with .44 squish 180psi, and 10.2:1 compression. Think about it.... Stock banshee is 8.2-8.5:1 and requires 90+ oct. I would run 100 or more. Im running 110 because idk where to get 100 at the moment. My 2 cents spent.... A stock Banshee is 6.5:1 according to Yamaha, and will run on regular 87 with no problems. Quote Link to comment Share on other sites More sharing options...
blowit Posted November 10, 2009 Report Share Posted November 10, 2009 What you need to do is check your compression ratio, im runnin 19cc domes with .44 squish 180psi, and 10.2:1 compression. Think about it.... Stock banshee is 8.2-8.5:1 and requires 90+ oct. I would run 100 or more. Im running 110 because idk where to get 100 at the moment. My 2 cents spent.... The CR is always the right way to select a proper fuel but since the OP indicated stock porting, I know pretty much where he is at. If he had porting, this would all be a guess without knowing some durations... Quote Link to comment Share on other sites More sharing options...
AKheathen Posted November 10, 2009 Report Share Posted November 10, 2009 ok, now i'm confused @ your process. porting would lower the ccr. please explain.... Quote Link to comment Share on other sites More sharing options...
00tbanshee Posted November 11, 2009 Report Share Posted November 11, 2009 155 with 19cc sounds alil low to me.what is your elevation? Quote Link to comment Share on other sites More sharing options...
RILS Posted November 11, 2009 Report Share Posted November 11, 2009 Blowit knows what he is talking about. The 6.5/1 is by japans method. Using a basic method about 12.7/1 with 22cc or stock head would be stock. Your flow changes alot with porting giving you a lower cranking figure however your cranking figure really has no relation to actuall compression ratio just gives you a base point to work from stock and people have transfered this over to what you can get by with from experience. Imo the guy above is fine with pump. Quote Link to comment Share on other sites More sharing options...
AKheathen Posted November 11, 2009 Report Share Posted November 11, 2009 Blowit knows what he is talking about. The 6.5/1 is by japans method. Using a basic method about 12.7/1 with 22cc or stock head would be stock. Your flow changes alot with porting giving you a lower cranking figure however your cranking figure really has no relation to actuall compression ratio just gives you a base point to work from stock and people have transfered this over to what you can get by with from experience. Imo the guy above is fine with pump. haha, you neither answered my question, nor told me someting new. the thing is, domes aside, the the corrected compression ratoi, or "japaneese method" if you prefer, is the largest with stock porting. the higher the exhaust port, the lower the ccr. i've always baased the need for higher octane by a ccr of 10.1:1 or more, based on sea level. i'm just currious how porting will raise cr or need for higher octane Quote Link to comment Share on other sites More sharing options...
LIM_Whiteboy4life Posted November 11, 2009 Report Share Posted November 11, 2009 (edited) Here's two more cents.... I will use my bike as reference 19cc domes, 10.2:1 CR, 180psi Over time the psi will decrease with wear but when it gets down below the said "threshold" for race fuel, i should run pump gas??!!! haha hell no. The compression ratio is still 10.2:1 no matter what. His motor is either @ 20,000 feet or its worn out and needs a rebuild. EDIT: or faulty O rings. If you want to run pump fuel 21cc domes or larger. I use this site to calculate compression ratio. http://www.csgnetwork.com/compcalc.html enter 2 for metric Then your bore size. I used 65.5 for .060 over Then your stroke. stock stroke is 54 Don't really need to know gasket bore size but if you do type it in. Now the gasket thickness and deck height, I divided my squish(.44) by 2 and entered .22 for each slot Now if you know the Piston dome CC enter that as well. Then the dome size. 19 Edited November 11, 2009 by LIM_Whiteboy4life Quote Link to comment Share on other sites More sharing options...
blowit Posted November 11, 2009 Report Share Posted November 11, 2009 (edited) haha, you neither answered my question, nor told me someting new. the thing is, domes aside, the the corrected compression ratoi, or "japaneese method" if you prefer, is the largest with stock porting. the higher the exhaust port, the lower the ccr. i've always baased the need for higher octane by a ccr of 10.1:1 or more, based on sea level. i'm just currious how porting will raise cr or need for higher octane I never mentioned a thing about the CR going up with porting, I simply stated that it changes the game. Reasons are that without knowing the durations, we would have no clue as to the CCR thus the fuel requirement. Why would a ported engine require more octane with the same CR? The effects of reverse wave gas flow in the exhaust of course.... This acts as more of a super charger at certain rpms (on the pipe) and stuffs A/F mixture back into the engine. Obviously if the window of time is open longer, more of the A/F mixture can be shoved back in there. This will NOT increase the static CR but WILL increase the "dynamic" CR which is something we look at very closely when designing engine components, heads, porting maps, etc. The "Japanese" method of testing the CCR is called such because it was innovated in Japan and it is a valid test indeed and still has huge considerations when selecting fuels, spark timings, etc. Hopefully that answers your questions. Regarding the 19cc dome on a stock port engine. Yes, pump fuels have been well proven in our shop to work, even with 4* of timing. I am making a few assumptions of the OP's engine but I will spit ball a .040"" squish clearance, 50% squish, etc. I was not really looking at the pumping numbers because that is not very relative as mentioned and really should pump up 170-180psi at sea level but a junk gauge can cause you problems and still not not change the fuel requirements. I have no idea how many engines we have had here that were comp tested "low" by the owner only to find out that they are fine when tested correctly with a good gauge. I am not trying to beat on bike owners but rather stating how things can be thrown out of context by simple using the magic "comp" number as the rule for rebuilding an engine. Other factors must be considered. I have seen pistons that were cracked, falling apart, rings worn out, and they still pump up good numbers. B Edited November 11, 2009 by blowit Quote Link to comment Share on other sites More sharing options...
AKheathen Posted November 11, 2009 Report Share Posted November 11, 2009 guestimating that mutch can throw your numbers off a bit Quote Link to comment Share on other sites More sharing options...
blowit Posted November 11, 2009 Report Share Posted November 11, 2009 guestimating that mutch can throw your numbers off a bit What am I guessing on?? You seem to want to ruffle my feathers with nearly every reply. Did you want to step outside.. I don't quite see what I am guessing on. Thousands of Banshees through the shop here, worked with plenty, yet to have one blow up on me. Personally owned a stocker wtih 19cc domes and 4* on pump. I beat the piss out of it. By doing the numbers, I am not really guessing..... B Quote Link to comment Share on other sites More sharing options...
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