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Knock Light Causes

Schmecman

Newbie
Joined
Feb 14, 2016
Messages
16
Location
Oconto Falls, Wisconsin
Country
USA
Snowmobile
15 viper
17 sidewinder
I have had problems with Knock light all year long. Have been working with Dave and he is convinced its a boost leak in my case. Building my own sensor tonight. I used the one we have all been passing around on this site. This is frustrating as hell. Cannondale I'll call you tonight to discuss. Bang our heads together to see if we can't figure this out.
 

cannondale27

Staff member
Moderator
Vendor
Joined
Feb 20, 2007
Messages
20,299
Location
Manitowoc,WI
I have had problems with Knock light all year long. Have been working with Dave and he is convinced its a boost leak in my case. Building my own sensor tonight. I used the one we have all been passing around on this site. This is frustrating as hell. Cannondale I'll call you tonight to discuss. Bang our heads together to see if we can't figure this out.
Thank You! Its been awhile.
 

bhall80

VIP Member
Joined
Mar 27, 2017
Messages
28
Age
46
Location
Cedarburg, WI
Country
USA
Snowmobile
2017 Sidewinder LTX-DX
2014 Viper LTX-SE
2002 SX Viper
1998 Polaris Indy 600 RMK
I put the Hurricane trail muffler and tune bundle on at the start of year. With the 240 and 270 tune I ran 91 oct non ethanol Esso gas, I had a knock light flashing all the time when pinning it. Flash would happen very fast. I couldnt react. At the start when it flashed I would back off the throttle then back on throttle. Sometimes it would flash again but I would just keep it pinned. So the after a bit when it flashed I just stayed on throttle and only a couple of times it would flash twice so that is when I would let off. I switched to Huskey 94 oct fuel with ethanol no more knock flashes on 270. I haven't tried it on the 240 or 290 tunes. Plan it to move up to 290 tune right away. Just wanted to make sure only 94 is left in fuel tank.
Full shift- this is exactly what is happening to me! Feathering the throttle at higher speeds will lead to LESS knock but if you abruptly pin it...it will knock. I was using 91 gas with 3 oz Lucas octane per 5 gallons to make 94. Maybe I need more? I will try sea foam too for possible moisture in the tank. All getting frustrating when my “free” gift from last years TY giveaway (flash only) cost me $1500 in add ons and now it’s like a chemistry experiment each time I fill up with gas. Sucks when it’s cold. I will say the flash is very impressive 0-100 but right now no point in me racing a buddy across the lake because the light will come on. Not a huge deal for me since I’m a trail rider more than a drag racer but I don’t want to risk motor failure either. Hopefully we can all get this figured out.
 

Hammer70

GRIPNRIP
Joined
Sep 6, 2015
Messages
662
Location
Niagara, Ontario.
Country
Canada
Snowmobile
82SS440/96VMAX/02SRX/08APE/15SRVIPER/17SIDEWINDER
DE06F7F1-6B1D-472B-BDFB-8E4945D9C11C.jpeg
Full shift- this is exactly what is happening to me! Feathering the throttle at higher speeds will lead to LESS knock but if you abruptly pin it...it will knock. I was using 91 gas with 3 oz Lucas octane per 5 gallons to make 94. Maybe I need more? I will try sea foam too for possible moisture in the tank. All getting frustrating when my “free” gift from last years TY giveaway (flash only) cost me $1500 in add ons and now it’s like a chemistry experiment each time I fill up with gas. Sucks when it’s cold. I will say the flash is very impressive 0-100 but right now no point in me racing a buddy across the lake because the light will come on. Not a huge deal for me since I’m a trail rider more than a drag racer but I don’t want to risk motor failure either. Hopefully we can all get this figured out.
Torco wants 8 oz to make plus 4 octane for 5 gallons your 3 oz seems low IMO
 

ClutchMaster

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Jan 18, 2016
Messages
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Location
tomahawk
Country
USA
Snowmobile
2015 Viper 270 hurricane,
2002 Viper W/162 A.C. skid, SRX pipes &CDI, 780 BB
LOCATION
Wisconsin
Torco or Klotz work much better than Lucas IMO.
If something isn’t working for you try something new.
 

bhall80

VIP Member
Joined
Mar 27, 2017
Messages
28
Age
46
Location
Cedarburg, WI
Country
USA
Snowmobile
2017 Sidewinder LTX-DX
2014 Viper LTX-SE
2002 SX Viper
1998 Polaris Indy 600 RMK
View attachment 145988
Torco wants 8 oz to make plus 4 octane for 5 gallons your 3 oz seems low IMO
The Lucas octane says 15 oz per 25 gallons so I figured around 6 oz per 10 gallons would work. I spoke with Dave at Hurricane today and he doesn’t feel a knock should go off at all at 240 tune based on gas. He also thinks 14.8 boost on 240 tune is a little high. He is turning on datalogger for me and I will test again this weekend.
 

ClutchMaster

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Messages
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tomahawk
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2002 Viper W/162 A.C. skid, SRX pipes &CDI, 780 BB
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Wisconsin
Boost leaks generally don’t cause knock, they actually cause lower boost levels. They can however cause the IAT’s to rise somewhat.
Like I said before, get some 110 octane and put a couple gallons in the tank, if your knock goes away then it’s fuel quality.
Just because the pump says “91” that is no guarantee that’s what it really is.
 

ClutchMaster

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Messages
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tomahawk
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2015 Viper 270 hurricane,
2002 Viper W/162 A.C. skid, SRX pipes &CDI, 780 BB
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Wisconsin
The Lucas octane says 15 oz per 25 gallons so I figured around 6 oz per 10 gallons would work. I spoke with Dave at Hurricane today and he doesn’t feel a knock should go off at all at 240 tune based on gas. He also thinks 14.8 boost on 240 tune is a little high. He is turning on datalogger for me and I will test again this weekend.

If you still have the stock map sensor it is pegged at 14.8 psi. Your boost is likely higher than that.
 

KnappAttack

24X ISR World Drag Racing Champion
Joined
Feb 19, 2004
Messages
3,443
Location
Welch MN
Country
USA
Snowmobile
2017 Sidewinder LTX-LE
Boost leaks generally don’t cause knock, they actually cause lower boost levels. They can however cause the IAT’s to rise somewhat.
Like I said before, get some 110 octane and put a couple gallons in the tank, if your knock goes away then it’s fuel quality.
Just because the pump says “91” that is no guarantee that’s what it really is.


This is true ClutchMaster, however the way a Winder is configured, a boost leak at the MAP sensor up in front of the sled would create a higher boost level and lower AF ratio. The MAP sensor in front of the Winder is controlling the boost and fueling. A leak at that sensor or going to it would allow it to boost higher and go lean too. Think about how a manual boost controller works bleeding off pressure to a wastegate in an aftermarket turbo system. This leak at or going to the map sensor would be the same effect, in essence it could be bleeding of a bit of pressure prior to getting to this MAP sensor. It would be the small lines going up front, not the large boost lines going to the engine leaking boost.


If you still have the stock map sensor it is pegged at 14.8 psi. Your boost is likely higher than that.

The stock 2 Bar sensor will read to 16.5 16.8 or so, beyond that is where it won't read higher. 240 tune is well below that threshold and not a concern.
 

ClutchMaster

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tomahawk
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2015 Viper 270 hurricane,
2002 Viper W/162 A.C. skid, SRX pipes &CDI, 780 BB
LOCATION
Wisconsin
Ahhh I thought a 2 bar would be all done @ 15 psi or so, they must build a little extra into that sensor.

Isn’t the Map sensor reference point after the throttle plates?
 

ClutchMaster

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Joined
Jan 18, 2016
Messages
2,996
Location
tomahawk
Country
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Snowmobile
2015 Viper 270 hurricane,
2002 Viper W/162 A.C. skid, SRX pipes &CDI, 780 BB
LOCATION
Wisconsin
I see your thinking is the line going to the sensor is leaking?
Yea not good
 


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