FUEL Octane with TD Tune?

[stevewithOCD]

Interesting. Major differences.

I started talking to DOO techs on this & they agreed with my analysis.
More noticeable on this little 6 cuz its only 90ish mph and i was riding rail road beds all week in the County.
Hard to see this at 110 to 120 mph on the Big Bores.

I know this is a big HP 4-stroke forum, but i think this info shows how edgy all new motors are & how gas effects them all.
AND how all motors pull timing & add fuel regularly.

The POO flashes lights & bucks the whole sled.
The DOO just slows it down without notice.

 

[SledFreak]

I think the big question is what additional protection does PERF offer in their compared to TD or Hurricane which uses GAP, instead of relying on stock Knock protection and this could be just the reason as to why some of those motors went down.

 

[Turboflash]

SledFreak, if you're referring to PEFI (Precision EFI) IMO the answer is NONE. At the end of this riding season I've seen and heard way too much evidence that the supposed premier PEFI Knock Protection system is non-existent or marginal at best. I'm in the process of doing complete engine rebuilds on 3 TCats (including mine) all w Stage 3 PEFI tunes. Granted sleds have about 6000 miles with this tune but all 3 have serious deto - enough for serious piston damage. Most of the time, these sleds have been run on 93 octane non-ethanol. Why didn't their great knock protection work as they advertise?
Everything possible was done to these 3 sleds to set them up for trouble-free 280HP riding. And I mean EVERYTHING. Every precaution to get best possible gas was taken always.
This is probably a totally different discussion but in some cases, pistons showed no damage from deto but they simply got too hot. The areas around the valve reliefs actually got so hot the aluminum material became "soft" and the relief sagged inward causing the top ring groove to become quite a bit wider (and therefore top ring lost support in that area). As Fleecer stated, multi-mile or extended WOT is most likely the cause (and myself and the 2 other guys who own the TCats are retards LOL). The cooling system in this 998 was designed for 200 HP. That included thickness of head castings, coolant passages, oil sprayers at the bottom of piston, water pump, heat exchangers, etc. At 280+ HP and long multi-mile WOT pulls, IMO the engine is making so much more heat (than at 200HP stock level) the cooling in head (and possibly rest of system) cannot carry away enough heat to keep it cooled properly. The chances of deto goes up and up, the longer the pull is.

 

[DMCTurbo]

SledFreak, if you're referring to PEFI (Precision EFI) IMO the answer is NONE. At the end of this riding season I've seen and heard way too much evidence that the supposed premier PEFI Knock Protection system is non-existent or marginal at best. I'm in the process of doing complete engine rebuilds on 3 TCats (including mine) all w Stage 3 PEFI tunes. Granted sleds have about 6000 miles with this tune but all 3 have serious deto - enough for serious piston damage. Most of the time, these sleds have been run on 93 octane non-ethanol. Why didn't their great knock protection work as they advertise?
Everything possible was done to these 3 sleds to set them up for trouble-free 280HP riding. And I mean EVERYTHING. Every precaution to get best possible gas was taken always.
This is probably a totally different discussion but in some cases, pistons showed no damage from deto but they simply got too hot. The areas around the valve reliefs actually got so hot the aluminum material became "soft" and the relief sagged inward causing the top ring groove to become quite a bit wider (and therefore top ring lost support in that area). As Fleecer stated, multi-mile or extended WOT is most likely the cause (and myself and the 2 other guys who own the TCats are retards LOL). The cooling system in this 998 was designed for 200 HP. That included thickness of head castings, coolant passages, oil sprayers at the bottom of piston, water pump, heat exchangers, etc. At 280+ HP and long multi-mile WOT pulls, IMO the engine is making so much more heat (than at 200HP stock level) the cooling in head (and possibly rest of system) cannot carry away enough heat to keep it cooled properly. The chances of deto goes up and up, the longer the pull is.

Multi mile wide open pulls?

I thought I was nuts running 3000'. Do you guys not worry about losing tracks?

 

[74Nitro]

Multi mile wide open pulls?

I thought I was nuts running 3000'. Do you guys not worry about losing tracks?

Yes, high speed really shortens the life of a track.
As far as knock goes, I could easily trigger the light after only 1/4 miles pulls if I tried running the 285-290 hp levels on 91

 

[justinator]

Anyone that owns a flasher, should spend the extra for a datalogger option regardless of what you think your riding style is.......unless it is literally tight trail systems that you struggle to find room for pulls a couple seconds long or rarely go wide open at all. It will let you know if what you are running for fuel is what you need for what you do or if you need more. It will give you an idea if the fuel at your favorite fill up spot is close to what it says it is or if its crap. It will show you if your favorite octane booster is doing anything to help you at the recommended mix ratios or if you need to mix stronger or find a different brand. You will see that your sled is happy for the first X number of feet but as that distance grows it becomes less impressed indicating fuel octane too low for the distance you plan on running and show you a direct relationship with intake air temp and timing retard. Not seeing the knock light does not mean your not pulling a fair amount of timing, it just means your not pulling enough to activate the knock light. A few oz of booster may drastically reduce that timing being pulled or completely eliminate it or show you the product your using does absolutely nothing for you. No way to know whats going on without being able to see it. Its a fairly inexpensive option thats easy to view and understand and after you use it and see you have a “happy” snowmobile it makes you feel better, atleast it did for me.

 

[Fleecer]

Multi mile wide open pulls?

I thought I was nuts running 3000'. Do you guys not worry about losing tracks?

At 3000 feet, things just start to get interesting, the weak start to fade, and the men get separated from the boys!!

After a mile WOT, tunes and setup really come into play. All the mitigating factors culminate together when running long distances, and the biggest tune wont always win.

It requires looking at temps/conditions for Saturday, then working several hours Friday night putting the right gearset/clutching/tune etc. The right boost level, iat temp, fuel pressure, AFRs, lane choice, how you sit and where you sit, all come together and dictate who the last man standing is. In my group, it's so tight, it often takes 4-5 multiple back to back 1 mile pulls to decipher who the king is!! As ridiculous as it sounds, there is nothing more fun!!

Blowing tracks is always a concern, and can be very dangerous especially on ice. Once the track comes out, the skid rests on the wheels and actually picks up speed initially. Blowing a track at 140mph on ice will cause the sled to free wheel about 1.25 miles before it stops. Meeting the treeline before that will definitely ruin your day. I've blown more than I care to count, but i only race on snow, so it isn't nearly as dangerous, albeit I've had one come around at WOT and pile drive me in the back of the head.

Some guys I run with that go fast change track every year. If you find yourself having to tighten the track 2-3 rides in a row, this is a telltale sign that the cords are breaking. Although ithe track may still look/appear new.....change it, as it is about to come out!!

 

[kinger]

SledFreak, if you're referring to PEFI (Precision EFI) IMO the answer is NONE. At the end of this riding season I've seen and heard way too much evidence that the supposed premier PEFI Knock Protection system is non-existent or marginal at best. I'm in the process of doing complete engine rebuilds on 3 TCats (including mine) all w Stage 3 PEFI tunes.

Tflash and I have talked a lot privately. You have 3 sleds in and you are 2 hrs north of me, I have 5 down here I think we can confidently say PEFI IS JUNK!! There is one in NY area that we know of. ANYONE READING DO NOT RUN PEFI!