RippinShee Posted August 7, 2009 Report Posted August 7, 2009 I see some people have advanced their timing to +5 or +6 to squeeze some extra power out... Anyone have experience with this? Quote
J-Madd Posted August 7, 2009 Report Posted August 7, 2009 You may have to run higher octane to do so. I run +5 on my stocker with 150 psi on 93 octane. The rest are on alky and run +7 - +10. Quote
RippinShee Posted August 7, 2009 Author Report Posted August 7, 2009 So if i run 110 octane and run +6 it should be fine? Quote
dajogejr Posted August 7, 2009 Report Posted August 7, 2009 I have always been a firm believer of a more generous squish band (.050s or so) less compression but more timing. IMO...high compression and tight squish bands put more stress on a motor than needed. Higher compression motors also don't like to rev out nearly as far. You could argue that a lot of timing will take away overrev, which...it will. But it's easier to take a degree or two out than it is to change compression. Compression ratio has more to do with the need for higher octane than timing does...but, with moderate to strong advances in timing (more than 4 IMO) you'll start to need more octane as well. Here's the question...if you bump the timing and get race fuel, are you going to slowly take away octane to see how much it needs? No...probably not. Like most of us, you'll just run higher octane than you need because it's safer. Are you getting 100% performance? No. Are you in better shape than not enough octane? Absolutely. Higher octane fuels burn slower. With the added heat from more compression and timing, you need a slower burning fuel... When the engine doesn't need fuel to burn that slow, it is hampering performance a bit. Not a lot, but a bit.... I probably just created more questions than what was asked...but...I'm bored at work, so there you go... Quote
RippinShee Posted August 7, 2009 Author Report Posted August 7, 2009 So as far as my milled head down to the .030... It wouldnt really hurt to go to +6 and 110? Quote
Ieat4strokes Posted August 7, 2009 Report Posted August 7, 2009 I have always been a firm believer of a more generous squish band (.050s or so) less compression but more timing. IMO...high compression and tight squish bands put more stress on a motor than needed. Higher compression motors also don't like to rev out nearly as far. You could argue that a lot of timing will take away overrev, which...it will. But it's easier to take a degree or two out than it is to change compression. Compression ratio has more to do with the need for higher octane than timing does...but, with moderate to strong advances in timing (more than 4 IMO) you'll start to need more octane as well. Here's the question...if you bump the timing and get race fuel, are you going to slowly take away octane to see how much it needs? No...probably not. Like most of us, you'll just run higher octane than you need because it's safer. Are you getting 100% performance? No. Are you in better shape than not enough octane? Absolutely. Higher octane fuels burn slower. With the added heat from more compression and timing, you need a slower burning fuel... When the engine doesn't need fuel to burn that slow, it is hampering performance a bit. Not a lot, but a bit.... I probably just created more questions than what was asked...but...I'm bored at work, so there you go... Dave go do some work! hhahah Quote
tundish2800 Posted August 7, 2009 Report Posted August 7, 2009 I ran race gas at plus four. I run +8 for alky, i know some guys running plus 11 or 12 on alky, personally i would go over +4 on gas just my .02 Quote
J-Madd Posted August 7, 2009 Report Posted August 7, 2009 So as far as my milled head down to the .030... It wouldnt really hurt to go to +6 and 110? Since stock heads vary in actual combustion chamber volume, you'll probably need to check compression and squish to see where you're at. But, I think you'll be fine. Quote
RippinShee Posted August 7, 2009 Author Report Posted August 7, 2009 +6...110 octane...and pwk 35's...will be next up. lol Quote
AKheathen Posted August 7, 2009 Report Posted August 7, 2009 running +5 and 20cc domes here, and it has an awesome midrange, but less rev out than before. 95 octane (50/50 90 pump& 100LL avgas) no detonation, good high altitude power riddin the mountain. i like to keep near the limit, running just enough octane. i did try strait 100LL and yeilded less power. basically, going +6 and running domes that could be between 22 and 19, you may be loosing power, or pretty close, but i doubt you need strait110, if jetted properly. take your readings to determin the octane need Quote
RippinShee Posted August 11, 2009 Author Report Posted August 11, 2009 I still dont understand...How would going to 110 octane and bumping timing up to +6 hurt my power? Quote
Nor*Cal Kid Posted August 11, 2009 Report Posted August 11, 2009 It may be a dumb duestion but what is "squish". Im still new to quads. just wondering Quote
AKheathen Posted August 11, 2009 Report Posted August 11, 2009 basically, the higher the octane rating, the slower the burn. higher compression makes it burn faster, and advanced timing makes it ignite sooner. too much octane for the cr, and timing, and you will only burn partially, and with less force, which is safer than burning too short, leaving heat to build up in the chamber, or rather, on the chamber surfaces. best thing is to find your actuall compression ratio and go from there. squish is the clearance between the top piston edge and the chamber. squish is what happens when you step on a bug, squish is what happens when the f@#%n airline seats you between 2 oversized individuals squish is what you do with solder when you are checking your squish. Quote
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