mike6301980 Posted August 10, 2009 Report Share Posted August 10, 2009 I recently built a 421cc motor and am running .050" squish with 165psi comp. with 110 torco and +4 timing. After 2 or 3 passese my ground strap will close up and touch the electrode. The plugs are running nice light tan color I put more fuel to it with no luck in solving the problem. It seems like detonation but dont know why. Should I back the timing off or may it be something else? Any help is appreciated The plugs are also comming loose which I would think would be due to detonation Quote Link to comment Share on other sites More sharing options...
blowit Posted August 10, 2009 Report Share Posted August 10, 2009 I recently built a 421cc motor and am running .050" squish with 165psi comp. with 110 torco and +4 timing. After 2 or 3 passese my ground strap will close up and touch the electrode. The plugs are running nice light tan color I put more fuel to it with no luck in solving the problem. It seems like detonation but dont know why. Should I back the timing off or may it be something else? Any help is appreciated The plugs are also comming loose which I would think would be due to detonation Would like to know more about your motor but you need to start back at 0 timing advance and ride it. You will be studying the burn band on the ground strap of the plug to determine optimal timing. Remember that timing is NOT what makes power. An optimal engine design will not need timing advance so don't think you need to get way up there to get it dialed. What is the displacement of your head? Shoot me a PM if you like and I can work you through the problem. B Quote Link to comment Share on other sites More sharing options...
mike6301980 Posted August 10, 2009 Author Report Share Posted August 10, 2009 Would like to know more about your motor but you need to start back at 0 timing advance and ride it. You will be studying the burn band on the ground strap of the plug to determine optimal timing. Remember that timing is NOT what makes power. An optimal engine design will not need timing advance so don't think you need to get way up there to get it dialed. What is the displacement of your head? Shoot me a PM if you like and I can work you through the problem. B I tried pm you i am new to the site and dont know if it worked if not here is what i sent The head has a cut 18cc dome approx 18.5 is what i was told. Never actually cc it. It seems like i should have more compression than i do with that dome. The motor is a vitos 68mm bb nikasil cylinders(they are not the mono blocks) with their 4mm crank and 110 rod with their weisco/vitos piston. I was going to back the timing off but everyone said that i need it for ignition advance at high rpm. Let me know if you need any more info. Thanks Mike Quote Link to comment Share on other sites More sharing options...
blowit Posted August 10, 2009 Report Share Posted August 10, 2009 I tried pm you i am new to the site and dont know if it worked if not here is what i sent The head has a cut 18cc dome approx 18.5 is what i was told. Never actually cc it. It seems like i should have more compression than i do with that dome. The motor is a vitos 68mm bb nikasil cylinders(they are not the mono blocks) with their 4mm crank and 110 rod with their weisco/vitos piston. I was going to back the timing off but everyone said that i need it for ignition advance at high rpm. Let me know if you need any more info. Thanks Mike Mike, I sent to a PM. Appears to be some setup issues. Brandon Quote Link to comment Share on other sites More sharing options...
slopoke Posted August 10, 2009 Report Share Posted August 10, 2009 someone correct me if i am wrong but advancing the timing does noting on the top end. It is meant for low end. I think retarded timing or 0 degrees would benifit the high rpm Quote Link to comment Share on other sites More sharing options...
blowit Posted August 10, 2009 Report Share Posted August 10, 2009 (edited) someone correct me if i am wrong but advancing the timing does noting on the top end. It is meant for low end. I think retarded timing or 0 degrees would benifit the high rpm Timing requirements get rather technical and subject to compression, fuel, squish, piston speed, etc. That all plays in to get max cylinder pressures to occur at right time. This is why there is an ignition curve because demands of ignition advance changes with rpm and engine load. Yes, as a general rule, you would reduce ignition timing at higher rpm. Brandon Edited August 10, 2009 by blowit Quote Link to comment Share on other sites More sharing options...
slopoke Posted August 11, 2009 Report Share Posted August 11, 2009 Not jacking here but......Does a stock cdi have a timing curve buit into it or is it just run what you got. I know on my streetbike I can map it however I want as far as timing curve and so forth. I know that the aftermarket ones have a mapping capability for the banshee. Am I correct in saying that if I bought an aftermarket module that has an interface I could program the ignition curve and throw my plate away? Quote Link to comment Share on other sites More sharing options...
blowit Posted August 11, 2009 Report Share Posted August 11, 2009 (edited) Not jacking here but......Does a stock cdi have a timing curve buit into it or is it just run what you got. I know on my streetbike I can map it however I want as far as timing curve and so forth. I know that the aftermarket ones have a mapping capability for the banshee. Am I correct in saying that if I bought an aftermarket module that has an interface I could program the ignition curve and throw my plate away? Yes, all CDI digital circuits like the Banshee will have a set timing curve that is non linear. Yes, depending on what module you use, you can eliminate the need for any type of initial timing plate. The plate will only make a linear adjustment across the board which may be good or bad for certain areas of the powerband. Problem with adjusting the timing curve is you really need to understand what you are doing. I don't think it is quite right to give all the adjustability to the end user because things can go wrong fast. Really, steady state dyno testing is the true way to do ignition mapping. Brandon Edited August 11, 2009 by blowit Quote Link to comment Share on other sites More sharing options...
J-Madd Posted August 11, 2009 Report Share Posted August 11, 2009 Very well explained. :thumbsup: Quote Link to comment Share on other sites More sharing options...
FireHead Posted August 11, 2009 Report Share Posted August 11, 2009 Yes, all CDI digital circuits like the Banshee will have a set timing curve that is non linear. Yes, depending on what module you use, you can eliminate the need for any type of initial timing plate. The plate will only make a linear adjustment across the board which may be good or bad for certain areas of the powerband. Problem with adjusting the timing curve is you really need to understand what you are doing. I don't think it is quite right to give all the adjustability to the end user because things can go wrong fast. Really, steady state dyno testing is the true way to do ignition mapping. Brandon My timing plate hss a Rolex in it......... It has China stamped on the back though. Is that good? :biggrin: Quote Link to comment Share on other sites More sharing options...
blowit Posted August 11, 2009 Report Share Posted August 11, 2009 My timing plate hss a Rolex in it......... It has China stamped on the back though. Is that good? :biggrin: That just means you have a genuine Rolex timing piece. :biggrin: Didn't you hear? every thing comes from China now. Quote Link to comment Share on other sites More sharing options...
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