KnappAttack
24X ISR World Drag Racing Champion
- Joined
- Feb 19, 2004
- Messages
- 4,683
- Location
- Welch MN
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- USA
- Snowmobile
- 2023 Sidewinder LTX-LE
2017 Sidewinder LTX-LE
As for base settings I use, for the -----------RX-1, 86 octane, 140 HP stock, 57 degree cam closing, head gasket thickness is .025-------------- Apex spec is, 86 octane, 150 HP stock, 71 degree cam closing, head gasket thickness is .017 Then you would plug in your new head gasket change, altitude and your boost setting giving you the octane requirements needed. If you decide to move the intake cam, that spec is also in there. I have seen some confusion on head gasket thickness. Some have measured the gasket including the embossed sealing hump. When the head is torqued these squish flat. The thickness I give you above are true installed specs. using stock replacement gaskets. Mike Knapp#17
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I have been running 12lbs on 100ll all season with stock compression at 8000-9500', with no problems. Well, the only problem I still have is keeping it off the rev limiter right off the line. She pulls real hard off the line, as I can race a twin piped rt and come out of the hole with it, then its bye - bye 
I have a parker Knock box and have yet to see it light up yet......
I have a parker Knock box and have yet to see it light up yet......
Don't forget that load and temp and setup are all factors !!!
Buzzing down the trail and/or short drag races on a given boost of xxx and octane of xxx might be fine because it really isn't max-loading your system. Now reduce your ground speed, jump off the trail, plug the hood vents/intakes with snow, and point it up a long hill. Max-heat-load your engine with the same octane that was just fine for joe-bag-o-donuts with his setup in his conditions and the deto monster just might bite ya in the azz !!!
Calculators/Testimonials should be used as considerations but not as absolutes for every person in every condition.
Buzzing down the trail and/or short drag races on a given boost of xxx and octane of xxx might be fine because it really isn't max-loading your system. Now reduce your ground speed, jump off the trail, plug the hood vents/intakes with snow, and point it up a long hill. Max-heat-load your engine with the same octane that was just fine for joe-bag-o-donuts with his setup in his conditions and the deto monster just might bite ya in the azz !!!
Calculators/Testimonials should be used as considerations but not as absolutes for every person in every condition.
LANEO
Guest
Ken
Do not assume that "7lbs is safe" Zero pounds of boost is safe, any amount of boost has risk. The Apex engine has a very high compression ratio. Factory boosted car engines run 12 to 15lbs with roughly 8-1 compression ratio's. The apex is closer to 11-1. At 11-1 preimium fuel is recommended with no boost at all. When you add boost to a stock Apex you risk head lift, detonation and more. If you add 5lbs of boost you may still be reasonallibly safe. But if you pin the throttle 1/2 mile at a time over and over again you may still do damage even with higher octane than premium feul. Do yourself a favor, if you plan to run over 7lbs. take the engine out and build it before you damage it. If you have not damaged it already, you wont run the rebuild price up. Reduce compression, add quality head studs, adjust cam timing, then stay under 12lbs with better that 93 octane gas.
Better advise would to tune, clutch and provide traction that can maxiumize the 220 HP( or so ) that you now have. You will beat anybody with 15lbs of boost with no engine mods, poor clutching and trail studs. Not to even mention how hard it is to tune the fuel mapping for any given altitude or riding style. If the guy you race is very lucky and can make up the jump you get with traction and clutching, and if you race far enough he might get you. Then race again because he will be off to the rebuilder.
Do not assume that "7lbs is safe" Zero pounds of boost is safe, any amount of boost has risk. The Apex engine has a very high compression ratio. Factory boosted car engines run 12 to 15lbs with roughly 8-1 compression ratio's. The apex is closer to 11-1. At 11-1 preimium fuel is recommended with no boost at all. When you add boost to a stock Apex you risk head lift, detonation and more. If you add 5lbs of boost you may still be reasonallibly safe. But if you pin the throttle 1/2 mile at a time over and over again you may still do damage even with higher octane than premium feul. Do yourself a favor, if you plan to run over 7lbs. take the engine out and build it before you damage it. If you have not damaged it already, you wont run the rebuild price up. Reduce compression, add quality head studs, adjust cam timing, then stay under 12lbs with better that 93 octane gas.
Better advise would to tune, clutch and provide traction that can maxiumize the 220 HP( or so ) that you now have. You will beat anybody with 15lbs of boost with no engine mods, poor clutching and trail studs. Not to even mention how hard it is to tune the fuel mapping for any given altitude or riding style. If the guy you race is very lucky and can make up the jump you get with traction and clutching, and if you race far enough he might get you. Then race again because he will be off to the rebuilder.
KnappAttack
24X ISR World Drag Racing Champion
- Joined
- Feb 19, 2004
- Messages
- 4,683
- Location
- Welch MN
- Country
- USA
- Snowmobile
- 2023 Sidewinder LTX-LE
2017 Sidewinder LTX-LE
Apex is 11.8/1 comp. ratio and runs on 86 octane fuel stock. I agree however that there is always risk involved. We have no problem trailriding at 1000-1500 ft altitude. You cant hold it wide open anyways unless you want to explode a track at 150 on the dreameter. That is why I would say not to push it, knowing the guys in the mountains tend to stay in the throttle longer.
