Detonation at 1/2 throttle......

[lt1bird]

well at 1/2 throttle around 6K rpms up I get detonation...I hear it start and get off quick...

Its a 535 with 165PSI.... I run 93 octane...had the timing advanced +5 on the plate.... Some folks said it would run just fine at +5 even on pump gas.... Trinity said NO way.... Put it to stock banshee timing for 165 PSI as the strokers inhernatly have timing built into the crank? What does that mean? Maybe he did not explain it properly.... someone want to chime in?

 

Thanks!

[lowbuckracing]

Ask them if they advanced the timming with a woodriff key for the stator already...If they did then put a stiocker on and advance your timming with a adjustable instead..your timming may be way out if they advanced it with a key plus your +5 on your adjustable..If not then try runnning on 110 and see if it goesw away..If your to much compression and not enough octane you will detinate and blow that pearl up..

[lt1bird]

It not advanced at the key...I built the engine...its an adjustable plate set at +5....shows it on the wheel with a timing light.. 22 degrees at idle... I put the timing back to "0" and will see how it runs...I really do not want to run race gas...its a street bike so I want to ride it and do not want to get stuck without race gas.... I have seen where folks say that a 10mil loves timing...others seem to run 93 octane on similar setups...... weird?

[2001Stroker]

I just finished building the same motor, with 25cc domes and +7 timing. I'm burning Sonoco 110. If I remember correctly, you have 27cc domes. I would be willing to bet that you need around 100 octane, to make it not detonate. Maybe even 104ish. What's you elevation?

[blowit]

Put it to stock banshee timing for 165 PSI as the strokers inhernatly have timing built into the crank? What does that mean? Maybe he did not explain it properly.... someone want to chime in?

 

Thanks!

 

 

 

NO, that would not be accurate. Stroking a crank, alters timing slightly due to the rod angle delta but change in minimal. Timing is relative to clocking or indexing of the flywheel relative to TDC. What does change is piston velocity and that is more relative for timing adjustments. The faster you compress the air fuel (piston velocity), the more volatile the mixture is, thus requires less timing to achieve max cylinder pressure at 20* ATDC.

 

 

Head design, fuel, AFR, ambient air temp, etc, all will have an effect on what optimal timing should be. 165psi does not mean much to me in terms of engine dynamics. head design, squish clearance, CCR, and UCCR are much more relative for deciding what fuel is required.

 

 

Hope that helps.

 

 

Brandon

Edited May 5, 2009 by blowit

[lt1bird]

yes, I do have 27 domes.... im at 500 from sea level... to run +5 trinity said I would need race gas....I told them this was a 93 octane engine only...If I run stock banshee timing(0 degree adavnace at the plate) should I be ok?? I really dont want to use race gas!!

 

Thanks!