FUEL Octane with TD Tune?

[74Nitro]

I actually like the octane guidance in the TD chart. Its always better to be conservative with the varying boost levels we are all running our 998s at.
I run the Hurricane SM and PM tune bundles and even though some of the selections are said to be safe on 87 octane I would only use 87 if there was no higher octane fuel available and then I would ride accordingly.
Typically I always use 91 fuel with Torco octane booster added no matter what tune I am using.

Agreed. It's a good guide.

 

[justinator]

Do knock sensors "wear out" or can they lose sensitivity over time? (Should they be replaced at some point?).

Thats a good question and I havent ever came across a solid answer for it. Ive been doing alot of reading on them regarding timing retard etc. Apparently on most modern vehicles if the ecm senses any irregularities with the knock sensor it reverts to a limp tuning which may or may not throw a check engine light but it will be obvious there is an issue because of poor performance and poor performance. Not having any ti ming retard what so ever is unrealistic because the only way to do that would be to run very high octane gas way higher than what was required or have an engine tune with low timing and then we would have low power output and poor fuel mpg. On a vehicle they are calibrated to run on a certain octane fuel on normal load conditions and the knock sensor takes over when their is a change in those predetermined average loads. Same as a sled normal trail riding on a cold day with low intake temps and good gas there will likely be zero timing retard. Riding after a big snowstorm where engine load is increased and intake air temp rises due to a snowfilled intercooler and increased turbo output the timing retard takes over and keeps things happy. Im pretty confident the sleds arent setup to let us know or limp the tune if somethings not quite right with the knock sensor......maybe a code on complete failure but im not sure. That leaves us finding out the hard way. Sometimes electronics are crap right out of the box so changing one as preventative maintaince may cause a problem you didnt have in the first place. ....... slim chance but possible. Maybe with the info on the manufacturer and model number of the sensor would allow access to specs for testing the sensor and know if its within range. maybe some of the sleds out there that have had issues arent directly related to the tune but maybe a sensor not doing its job correctly?? The ecm needs input to know what to do and if the input isnt accurate it doesnt know that. Wish there was a sure fire way to know everything checks out because if they do wera out or get tired over time the issues are gonna show their face on big tunes when the mileage gets up there.

 

[1nc 2000]

Run your sled on the track stand and tap on the engine or frame next to the engine with a hammer. I bet the knock protection would go off with a good sensor.

 

[fatchance]

Best way to keep these issues at Bay is too watch your AFR and make sure it's in check. I stopped watching MPH and RPM. Only thing i watch live now is engine temp, AFR, timing retarded and boost. I can go back and look at logs anytime to see what's happening, but i can't see riding without knowing these live values.

 

[justinator]

Thats the reason I got the data logging was to learn what was normal for my sled and be able to monitor it and make sure it stays normal but its only as good as the sensors providing the info. I think when turboflash asked about the sensors ever "wearing out" or not functioning correctly its for this reason. If the sensor isnt picking up early knock like it should the ecu will not know to pull timing and try to control it, instead the knock will get worse and maybe it knocks enough times before any timing gets pulled that it has time to cause damage. Proper afrs and good fuel help to keep knock from happening but I recently tried a tune that runs richer afrs and lower peak boost numbers then my previous tunes but it seems to want to pull timing easier than my previous tune.

 

[1nc 2000]

Also a lab scope can be used to test the intensity and duration of the knock being shown from the sensor.

 

[fatchance]

I agree to a degree. If the knock sensor starts to fail than one can be the safe fail to let go of the throttle when AFR's become out of the optimum range. The tuners have designed these tunes to operate at an optimum range. Once exceeded you're on your own. Wether timing is being pulled or not the motor is running lean beyond the optimum AFR range which should be mid 11's. I think the closed loop system has improved upon a wider range of conditions, but it can only do so much.

 

[justinator]

I agree to a degree lol, Ive never had my afrs get out of an optimal range ever,down to way below zero temps and big pulls. Real hot spring conditions prior to closed loop yes,on the rich side, beaides that never,even when the logs show slight timing being pulled(.2-.4 degrees) so if my knock system did not work and my afr was showing ideal numbers then continuing to hold the throttle could lead to damage if knock is present, hence why automobiles will revert to limp mode in the event of a knock sensor failure. But of course this whole conversation is assuming theres faulty knock sensors not working correctly which their maybe, or maybe its just bad tunes with poor knock protection devices??

 

[fatchance]

Well this is something that i think will be revisited after this year's many failures. We really don't want to see any timing being pulled let alone the DETO flash at 2.5-3 degrees.
.2-.4 degrees is still a sign of DETO any way you slice it and this needs to be held at bay. There's so many variables and the cooker cutter tunes witnessed their vulnerability this season with the extreme cold conditions.
Can you imagine what some of these sleds are actually running for AFR with no data logging? You would never know what was actually happening until it was too late.

 

[justinator]

I think alot of sleds get tortured without the owners knowing anything is out of the ordinary. No way to know without a log. While I agree zero degrees of retard would be ideal and perfect its almost impossible to do with toys that see forever changing load conditions and fuel qualities. I think the best part of the datalog is being able to see if you are constantly pulling timing repeatedly to some degree which indicates a problem or likely something that can be corrected or avoided. A sled that occassionaly pulls a bit of timing at random times is normal im0 and operating as designed. If your fuel quality is good and afr is good and running at proper rpm timing retard should be very minimum and not something your seeing constantly on your logs. From all the reading ive done it sounds like seeing small amounts of tming retard is harmless but without a correctly functioning method of controlling it and keeping it small that knock will grow to something damaging if not catastrophic

 

[1nc 2000]

https://www.facebook.com/video.php?v=1320628434709465

 

[stevewithOCD]

Thats almost nothing, it takes either 2 or 2.5 degrees of timing retard to activate knock light on dash. If it was a concern then I think the tuners would of activated the knock protection much earlier. Most modern 2-strokes operate the same way, they are constantly adjusting timing to keep knock at bay and when the timing retard reaches a predetermined set point it sets the octane warning on dash. Once again the manufacturers have a threshold on whats ok and what is not to determine when its time to activate protection system. Only way to see whats going on is with datalogging. I would only be concerned if sled seems to pull timing frequently and repeatedly indicating other issues with sled or fuel problems. The knock sensors job is to pick up imperceptible levels of knock and retard timing to prevent it from occuring again or reaching the point of audible knock which we all know is very bad. I would venture to say that any tuned sled, including smaller 240-250hp tunes have some degree of timing retard going on in certain/specific conditions or loads throughout the course of a ride.

Even stock sleds will detune.
My little 600R, believe it or not, did it all the time & that's only 125hp.

This is what i saw same day, same trail:

100mph on 93 Ethanol
95mph on 91 Ethanol
90mph on 90 Non-Ethanol
85mph 87

No knock light
No sign of anything
Just detuning itself
I thought the belt was wearing down
Put in 93 & BANG! 101

 

[justinator]

Even stock sleds will detune.
My little 600R, believe it or not, did it all the time & that's only 125hp.

This is what i saw same day, same trail:

100mph on 93 Ethanol
95mph on 91 Ethanol
90mph on 90 Non-Ethanol
85mph 87

No knock light
No sign of anything
Just detuning itself
I thought the belt was wearing down
Put in 93 & BANG! 101

Yes sir that is life, its gonna happen when they want max hp. Sled hp has come a long ways

 

[Fleecer]

Saw this on TD website and thought I would post. Could be old I don't know. I guess what caught my eye was the Fuel recommended for the 17 psi tunes.. thought it was interesting..
View attachment 161101

No doubt, those octane numbers are conservative if you are riding with your wife and kids, but for all other types of riding, I would follow those recommendations religiously.

Be advised, those recommendations are not retard proof. Back to back pulls extending a mile, or even fast trail riding with constant speeds over 120mph for miles on end require even higher octane.

Good fuel is like a wildcard, and will blanket a plethora of other issues such as high AFRs, high iats, too much timing, cold temps/over boosting etc.

As people pack on the miles and continue to run bigger tunes, we are starting to see more engines going down. Imo, many of these catastrophic failures could have been prevented with proper fuel.

 

[Riceburner]

Even stock sleds will detune.
My little 600R, believe it or not, did it all the time & that's only 125hp.

This is what i saw same day, same trail:

100mph on 93 Ethanol
95mph on 91 Ethanol
90mph on 90 Non-Ethanol
85mph 87

No knock light
No sign of anything
Just detuning itself
I thought the belt was wearing down
Put in 93 & BANG! 101

Interesting. Major differences.