Can chassis/driveline noise trigger deto/knock light?

[Turboflash]

Be curious if anyone has experienced knock/deto light due to chassis/driveline noise?
As we all know, if/when deto light comes on, ECU is already in process of reducing boost and timing thus "detuning" engine.
This past weekend, I was observing testing on a '17 TCat on Stage 3 PEFI in a well-covered hayfield with ice base. 192 ea 1.50 Triggers on 1.25" Ripsaw II, Turbosmart BOV. Running fresh 93 octane non-oxy gas. Boost test showed no leaks at 25 psi. Sled has about 5ooo miles on it all with Stage 3.
Sled would leave line great and at approx 1000'+ the deto light would come on bright and engine would detune. Running about 8900 RPM. Did not overshift nor hit rev limiter. Boost gage shows run starts at 17-18 psi and once deto light comes on it goes down immediately. Seems like deto system is working right.
Repeated run several times and more or less, same thing. Next pass, pilot waited until deto light came on and then lightly applied brake. Deto light immediately went off. Repeated and same thing. Light brake drag shuts deto light off.
Sled just had track drive bearing replaced (just for maintenance as old one still looked good) and does have BOP wedge. Chain case was just serviced. Chain and gears (21-38) looked great, no wear, all was well. New oil and tension chain properly.
Fiber optic camera inspection of all cylinders showed engine is definitely not detonating.
Sled has Woodys angled backers with Triggers. On stand, IMO lots of "noise" coming from drive wheels and idlers hitting the angled head of Triggers (compared to my sled which doesn't have angled backers).
Sled has recently been changed to use Bill Mohr center spring.


Questions: Could change to Bill Mohr center spring be pushing front of rail down with enough force (and subsequent track clip noise/and or stud heads hitting center idlers hard enough) to cause deto light to come on?
Could mechanical noise in driveline cause enough noise to trigger deto light?
Sled also will flash deto light upon deceleration after WOT burst. Why would decel trigger deto light?

An ideas on what's doing on so I can pass to sled owners? Any ideas welcome. It's like knock sensor is too sensitive. BTW- knock sensor was electrically checked to be within Cat spec.

 

[DooZ]

I remember @eightpilot had some deto issues with his TD tunes that he thought were from noise or a bad knock sensor. Can't remember outcome. Maybe he'll chime in.

 

[NYTurbo]

Yes but not usually at 1000 feet, I've found false knock seems to happen much earlier when things are loading up. I've also seen a loose track cause issues which could be your issue.

 

[STAIN]

Could mechanical noise in driveline cause enough noise to trigger deto light?

I cant speak for sleds but in cars----YES. I have seen a chopped set of snow tires trigger a knock sensor in a car making it run down on power.
I dont know why a sled would be different

 

[jonlafon1]

I have seen issues with knock sensors being over torqued ?

 

[kinger]

I have Bill Mohr spring and now deto light after being WOT for 3 seconds every time on PEFI 250 repeatable over and over. So many issues with the sled hard to say its the spring...I will try the brake tap if it ever runs again.

 

[cannondale27]

If that triggers it the knock program is faulty.

 

[eightpilot]

Absolutely sounds like it’s chassis related if applying the brake stops it. I battled knock for the first year I had my 2017. Tried everything. Finally chased it back to a bad sensor on the front of the motor. Mix up some C16. If you still get knock it’s a chassis issue or knock sensor.

 

[74Nitro]

Agree with eightpilot. Just add some race gas and see what the knocklight does.

 

[cannondale27]

Absolutely sounds like it’s chassis related if applying the brake stops it. I battled knock for the first year I had my 2017. Tried everything. Finally chased it back to a bad sensor on the front of the motor. Mix up some C16. If you still get knock it’s a chassis issue or knock sensor.

It can also still be the tune of the knock sensor. Getting that right is way more difficult than tuning ignition fuel and boost. There are issues out there and some tuners are worse than others. Research it. Knock protection has been the most difficult thing to accomplish for 20 years now easily. This kind of power should not be easy and it isn’t. Can’t count number of times my NA Viper waxed Turbo sled and excuse was always oh my knock light was on. Just saying buyer beware. It’s not as simple getting 250-300hp as it seems.

 

[74Nitro]

I run 260 with stock muffler and CAI all day long on 91 and don't trigger the knock light.
Heading out today as we got a big dump of snow yesterday and trails are mint!

 

[fourload]

My friend had those angled backers on his Doo. Noisy as hell. I would get rid of them first. Are the limiter straps all the way out? New stronger front spring could be putting lots of pressure on front end of rail on acceleration causing vibrations?

 

[Turboflash]

Limiter straps are in stock position which is 2nd hole from longest. I told him to try pulling the limiters up 2 holes for testing purposes to see if problem goes away. Yes, I too think those angled backers are noisy on drive sprockets and skid idler wheels. Wouldn't run them in a trail sled. Not needed.
Interesting though that lightly dragging brake shuts deto light off. He has ran this sled for 4 years now without this issue. It was tuned to 280 from day one. No deto light issues until he installed the Bill Mohr spring about 3 weeks ago.
Again, for testing purposes, I suggested he put the stock spring back in and see if problem goes away.
Engine is definitely not in deto. Running fresh 93 octane unleaded. Fiberoptic camer

 

[Turboflash]

Limiter straps are in stock position which is 2nd hole from longest. I told him to try pulling the limiters up 2 holes for testing purposes to see if problem goes away. Yes, I too think those angled backers are noisy on drive sprockets and skid idler wheels. Wouldn't run them in a trail sled. Not needed.
Interesting though that lightly dragging brake shuts deto light off. He has ran this sled for 4 years now without this issue. It was tuned to 280 from day one. No deto light issues until he installed the Bill Mohr spring about 3 weeks ago.
Again, for testing purposes, I suggested he put the stock spring back in and see if problem goes away.
Engine is definitely not in deto. Running fresh 93 octane unleaded. Fiberoptic camer

Meant to conclude by saying fiber optic inspection of each cylinder shows perfect color. Engine is not in deto. Knock sensor is picking something up so it thinks it's in deto but it's not.

 

[justinator]

If light brake drag makes it go off.......is it possible somethings going on with rotor thats transmitting into the chassis and /or maybe caused by the wedge . Maybe be worth removing wedge for a test or swapping out rotor. Its a far stretch to think that could be it but light brake drag makes it disappear so id think I would personally start there.