I would try messibng with the timing.Too much timing will mph it will be faster from point A to B but your going for mph.
valin
Active member
Before I know what the timing curve is with the '97 SX ignition, I am not going to change the timing. Does anybody happen to know what the timing stats are for that CDI?
I have a price 1000 that I am running a 97 sx ignition in with 15.6:1 and 112 with no problems. But I am only running 660'.
Timing
Won't too much timing only hurt your top end on long distance runs......especially speed runs? I definately don't have the experience that some guys who have previously posted here do but I know when I took timing out of my Viper it helped top end.
Madmatt
Won't too much timing only hurt your top end on long distance runs......especially speed runs? I definately don't have the experience that some guys who have previously posted here do but I know when I took timing out of my Viper it helped top end.
Madmatt
mbarryracing
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Sounds like the stingers are too small / restricted on your pipes for more than 1000ft causing too much back pressure when really heated up.
No timing or fuel will help that.
For warranty reasons Polaris use to design their OEM pipes with rather large stingers to withstand long blasts across a lake, but the stingers were too large to produce enough backpressure for peak power in short 660 ft drags or 10 second dyno runs...
A good dyno session, like at www.dynotechresearch.com would be $$$ well spent before field testing, and should be close enough for you to drive to. You'll have to do an extended run to simulate a 2000ft blast.
You'll probably find an article in the archives from an older dyno session regarding this very issue...
No timing or fuel will help that.
For warranty reasons Polaris use to design their OEM pipes with rather large stingers to withstand long blasts across a lake, but the stingers were too large to produce enough backpressure for peak power in short 660 ft drags or 10 second dyno runs...
A good dyno session, like at www.dynotechresearch.com would be $$$ well spent before field testing, and should be close enough for you to drive to. You'll have to do an extended run to simulate a 2000ft blast.
You'll probably find an article in the archives from an older dyno session regarding this very issue...
Last edited:
valin
Active member
Stingers are 29.3mm. That stinger diameter is more than sufficient for the distance. We're running that diameter on 4 of our sleds.
As I have said in a previous post block off the coolant hose that goes to the top of the tank and make the coolant go down to the heat exchanger. I had my sled plumbed the same as yours and it would not cool sufficiently. I found this out when I went to the dyno and it took forever to cool it between runs
mbarryracing
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valin said:
Consider the amount of exhaust flow thru same 29.3mm diameter. What are the displacement of the other 4 sleds? same as this 1108?
Just tossing out ideas, nothing negative intended...
valin
Active member
mbarryracing, the other sleds are 1000's, 1050's and 1080's, making very close to the same power.
I do not believe the problem lies within water temperature. What is happening in the motor is that it is building extreme heat, nearly instantly. The question is why? Well, I believe the fuel I am running (Torco Mach 112) is pre-igniting, causing the temperature to rise instantly at a rapid rate, resulting in overexpanding of the piston. Since it is not mixture related, the problem lies somewhere within 3 things.....the type of fuel, timing, and compression ratio. The compression ratio is good for the distance at 13.5:1, but the timing is still quite steep (I believe the SX ignition sits at 18 degrees BTDC after 7000 rpm). Since octane is simply the resistance to burn, I have to increase the octane I am running to stop the pre-ignition of the fuel. I am going to jump up to Torco Mach 116, which is 115 octane, instead of the Torco Mach 112, which is 109 octane that I was previously running.
I do not believe the problem lies within water temperature. What is happening in the motor is that it is building extreme heat, nearly instantly. The question is why? Well, I believe the fuel I am running (Torco Mach 112) is pre-igniting, causing the temperature to rise instantly at a rapid rate, resulting in overexpanding of the piston. Since it is not mixture related, the problem lies somewhere within 3 things.....the type of fuel, timing, and compression ratio. The compression ratio is good for the distance at 13.5:1, but the timing is still quite steep (I believe the SX ignition sits at 18 degrees BTDC after 7000 rpm). Since octane is simply the resistance to burn, I have to increase the octane I am running to stop the pre-ignition of the fuel. I am going to jump up to Torco Mach 116, which is 115 octane, instead of the Torco Mach 112, which is 109 octane that I was previously running.
valin
Active member
I do appreciate everyone's input. It's nice to see the opinions and experience.
Srxspec
Your #1 performance shop!
According to the 1997 Tech Update book the 700 SX ignition does run a max advance of 28* BTDC from 5500-6000 RPM and then falls to 18* BTDC from 7000 RPM and higher.
valin
Active member
Yes, that the information I have as well. Thank you for that. I was skeptical if it stayed at 18 degrees after 7000, so I appreciate clarifying that.
valin
Active member
if you look inside the piston on the underside of the dome, it tells you whats happening inside the engine...................
jabber800
New member
Ryan who's running the XCR? and how did it run?? Let me know the next time you go out... Whould like to get a few 1000ft. passes in before Alliston runs..
mbarryracing
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valin said:
valin,
how old is your fuel?
valin
Active member
mbarryracing....the fuel is a brand new drum, just too low of octane.
Dan, the XCR is owned by Ken Laurin. He's still working on it, but ran 138.9 mph in 2000' with no RPM. He'll be in the low to mid 140's this year. His motor built 245 hp and 134 ft. lbs. at 9800.
Dan, the XCR is owned by Ken Laurin. He's still working on it, but ran 138.9 mph in 2000' with no RPM. He'll be in the low to mid 140's this year. His motor built 245 hp and 134 ft. lbs. at 9800.
valin
Active member
The motor is back together. Instead of attempting to solve the problem with fuel, I took a shortcut and pulled out some timing with a 4 degree keyway. Now the timing above 7000 rpm is back to 14 degrees. I decided to cut the timing instead of simply increasing the fuel grade because I could not find a definitive answer as to what the flashpoint is on the various types of fuels (even Torco couldn't answer the question). I was also concerned about running such a low compression ratio and throwing alot of octane at it.......resulting in a very slow burn and probably incomplete burning. Anyways, I will head back out on Monday for testing. Hopefully it comes home running this time 
2000' is a pain in the ***!
2000' is a pain in the ***!
valin
Active member
Well, testing didn't go so well today. My sled decided it was hungry and ate a reed pedal. I was also having an issue prior to the reed eating incident, and am not sure if it is fuel related, timing related, or if it was reed related. The pedals are on order, and I will have to get back out there on Saturday.
valin
Active member
Well, the motor does not like the final timing at 14 degrees with the 4 degree key. I will be heading back out in the morning with a straight timing key back in it to rule out any other issues that might have occurred. When it runs fine, and I am sure it will, I will install a 2 degree key to cut the timing back to 16 degrees. I will keep you posted.