tom582 Posted September 21, 2011 Report Share Posted September 21, 2011 hello all i have an 01 banshee fmf gold with powercore 2. i have mild portjob. .040 over pistons with about 6 hours on them. i am at 1200feet above see level. The bike runs incredable i did a compression test held gas wid open and kick afet prob 8 kicks im hitting 150 psi on both sides..sounds little high to me. i had 90 psi before rebuild..? what im trying to find out is 150 psi too much for pump gas and what should i watch for..? It does run great currently on 93 pump gas. im just little scared i guess i dont want to scarp my new top end. here is short vid of it .thanks for any feedback. Quote Link to comment Share on other sites More sharing options...
mopar1rules Posted September 21, 2011 Report Share Posted September 21, 2011 Don't use the cranking psi figure from compression gauge to dictate octane. Need to use compression ratio to know for sure. What domes you running now? Quote Link to comment Share on other sites More sharing options...
tom582 Posted September 21, 2011 Author Report Share Posted September 21, 2011 Don't use the cranking psi figure from compression gauge to dictate octane. Need to use compression ratio to know for sure. What domes you running now? im just running stock head. Quote Link to comment Share on other sites More sharing options...
tom582 Posted September 21, 2011 Author Report Share Posted September 21, 2011 150 is alright for pump.. its 160 + for race... in most occasions.. howerver... if you go down in elevation it can / will effect compression and jetting.... so if you lets say jump down to for EX (not exact numbers 500 Feet you compression will jump up and your jetting will be lean) if you go higher in elevation... the less psi you will have and richer jetting... thanks for the info. very helpful Quote Link to comment Share on other sites More sharing options...
Jereme6655 Posted September 21, 2011 Report Share Posted September 21, 2011 Don't use the cranking psi figure from compression gauge to dictate octane. Need to use compression ratio to know for sure. What domes you running now? How exactly do you find your compresion ratio to determine whether you require a higher octane. It could be something completely obvious.....but currently im having a brain fart from hell...... Quote Link to comment Share on other sites More sharing options...
mopar1rules Posted September 22, 2011 Report Share Posted September 22, 2011 To figure out your UCCR (un-corrected compression ratio), you take the swept volume of cylinder (radius of cylinder sqaured X pi = "something" X stroke) and add on the volume of the head dome volume, and head gasket volume (if applicable.....like if you have a steel head gasket), then you take that total volume and divide that by the trapped volume (volume above the piston, when piston is at TDC). To find out the trapped volume and head volumes, you will need a lab burrette (sp?), and some kerosene, and some grease. I like to get the piston within 1/2" from TDC, then smear grease all around the top portion of the cylinder bore. Then bring the piston to exact TDC. The grease just insures that the kerosene is sealed from leaking past the rings. Be sure to wipe off the excess grease that piles up. Of course the head is off for this. Once piston is at TDC, and the head is a cast stock unit, I will smear a thing film of grease to both sides of the head gasket, and then when the head gets bolted down, nothing will leak. Make sure engine head gasket surface is flat/parallel to the ground. Start filling the engine w/kerosene thru the spark plug hole. Stop when the kerosene gets to the top of the spark plug hole. Look on burerette of how many cc's were needed to fill that area up. Then subtract approx 2.2cc for the spark plug hole and that's your trapped volume. Take this value and divide by the total volume of what I said before. Hopefully this sheds some light for you guys. Quote Link to comment Share on other sites More sharing options...
Jereme6655 Posted September 23, 2011 Report Share Posted September 23, 2011 To figure out your UCCR (un-corrected compression ratio), you take the swept volume of cylinder (radius of cylinder sqaured X pi = "something" X stroke) and add on the volume of the head dome volume, and head gasket volume (if applicable.....like if you have a steel head gasket), then you take that total volume and divide that by the trapped volume (volume above the piston, when piston is at TDC). To find out the trapped volume and head volumes, you will need a lab burrette (sp?), and some kerosene, and some grease. I like to get the piston within 1/2" from TDC, then smear grease all around the top portion of the cylinder bore. Then bring the piston to exact TDC. The grease just insures that the kerosene is sealed from leaking past the rings. Be sure to wipe off the excess grease that piles up. Of course the head is off for this. Once piston is at TDC, and the head is a cast stock unit, I will smear a thing film of grease to both sides of the head gasket, and then when the head gets bolted down, nothing will leak. Make sure engine head gasket surface is flat/parallel to the ground. Start filling the engine w/kerosene thru the spark plug hole. Stop when the kerosene gets to the top of the spark plug hole. Look on burerette of how many cc's were needed to fill that area up. Then subtract approx 2.2cc for the spark plug hole and that's your trapped volume. Take this value and divide by the total volume of what I said before. Hopefully this sheds some light for you guys. Fuck me......now i know why people opt to just try and use the kicking compression to guage whether they will need a higher octane..... Quote Link to comment Share on other sites More sharing options...
blast off Posted September 23, 2011 Report Share Posted September 23, 2011 To figure out your UCCR (un-corrected compression ratio), you take the swept volume of cylinder (radius of cylinder sqaured X pi = "something" X stroke) and add on the volume of the head dome volume, and head gasket volume (if applicable.....like if you have a steel head gasket), then you take that total volume and divide that by the trapped volume (volume above the piston, when piston is at TDC). To find out the trapped volume and head volumes, you will need a lab burrette (sp?), and some kerosene, and some grease. I like to get the piston within 1/2" from TDC, then smear grease all around the top portion of the cylinder bore. Then bring the piston to exact TDC. The grease just insures that the kerosene is sealed from leaking past the rings. Be sure to wipe off the excess grease that piles up. Of course the head is off for this. Once piston is at TDC, and the head is a cast stock unit, I will smear a thing film of grease to both sides of the head gasket, and then when the head gets bolted down, nothing will leak. Make sure engine head gasket surface is flat/parallel to the ground. Start filling the engine w/kerosene thru the spark plug hole. Stop when the kerosene gets to the top of the spark plug hole. Look on burerette of how many cc's were needed to fill that area up. Then subtract approx 2.2cc for the spark plug hole and that's your trapped volume. Take this value and divide by the total volume of what I said before. Hopefully this sheds some light for you guys. waaaaaaaay too much work for me just to figure out what gas to use, no wonder people just check compression Quote Link to comment Share on other sites More sharing options...
mopar1rules Posted September 23, 2011 Report Share Posted September 23, 2011 Too much work?? I guess replacing pistons every few hrs of operation, due to damage from deto, is easier than figuring out the trapped volume and then knowing EXACTLY what octane is needed?? Well, the good side is that you idiots are going to keep the site sponsors and wiseco in business, w/your compression gauge octane dictator. Quote Link to comment Share on other sites More sharing options...
Jereme6655 Posted September 23, 2011 Report Share Posted September 23, 2011 Too much work?? I guess replacing pistons every few hrs of operation, due to damage from deto, is easier than figuring out the trapped volume and then knowing EXACTLY what octane is needed?? Well, the good side is that you idiots are going to keep the site sponsors and wiseco in business, w/your compression gauge octane dictator. hey now.....dont have to toss "idiot" at me.........i just said now i know why people just try to use kicking compression.. NEVER said that i wouldn't do it..........its just alot of work. Quote Link to comment Share on other sites More sharing options...
crash&burn Posted September 23, 2011 Report Share Posted September 23, 2011 To figure out your UCCR (un-corrected compression ratio), you take the swept volume of cylinder (radius of cylinder sqaured X pi = "something" X stroke) and add on the volume of the head dome volume, and head gasket volume (if applicable.....like if you have a steel head gasket), then you take that total volume and divide that by the trapped volume (volume above the piston, when piston is at TDC). To find out the trapped volume and head volumes, you will need a lab burrette (sp?), and some kerosene, and some grease. I like to get the piston within 1/2" from TDC, then smear grease all around the top portion of the cylinder bore. Then bring the piston to exact TDC. The grease just insures that the kerosene is sealed from leaking past the rings. Be sure to wipe off the excess grease that piles up. Of course the head is off for this. Once piston is at TDC, and the head is a cast stock unit, I will smear a thing film of grease to both sides of the head gasket, and then when the head gets bolted down, nothing will leak. Make sure engine head gasket surface is flat/parallel to the ground. Start filling the engine w/kerosene thru the spark plug hole. Stop when the kerosene gets to the top of the spark plug hole. Look on burerette of how many cc's were needed to fill that area up. Then subtract approx 2.2cc for the spark plug hole and that's your trapped volume. Take this value and divide by the total volume of what I said before. Hopefully this sheds some light for you guys. Quote Link to comment Share on other sites More sharing options...
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