DynoTech on the Poo 800-Some thoughts

[dynotechjim]

I believe that the 09s don't light up when det sensor is pulling timing/ adding fuel like earlier sleds. But it's reaction is severe enough (a good thing) to protect the engine that you should feel the power drop.

 

[AKSNOWRIDER]

I believe that the 09s don't light up when det sensor is pulling timing/ adding fuel like earlier sleds. But it's reaction is severe enough (a good thing) to protect the engine that you should feel the power drop.

Jim is correct, mine never lit up,but you can feel it pull power..

 

[Ron]

Don't count on the deto sensor saving your engine. According to Carl's the electronic's are a lot more sophisticated than earlier versions so you can sqeak the pistons. The ECU will attempt to make small adjustments to fuel and timing but not necessarily fast enough to "save it". Must be the reason you have a seperate map for Ethanol.
Sleds remapped by Carl's for BB's or porting will have the deto light operational.

 

[Bubba700]

Been lurking in this thread quiet a bit and was wondering if perchance anyone of the people doing the dyno runs had thrown a 700 on right after the 8's for a comparrison between the 2.

 

[rab]

Det light operational on cfi

does anyone know if Carls does own mapping in house or if its farmed out and done to thier specs?

I would be interested in having the DET light operational on my new sled even with the same map intact ,has anyone researched if this is possible and how much for the service

 

[buckshot]

We need a light so you can confirm if the sled is compensating for detonation or if there is something else wrong. IMO

 

[voodoo]

^^Yes, it is the DET sensor/check engine light. It blinks every second when you have a lean condition, usually from bad fuel.

It does not sense a lean condition. Please do not post this type of info as it starts all sorts of other sidebars that take these threads the wrong direction. You can have plenty of gas and still detonate if the octane won't handle the timing or compression. Lean and detonating are 2 different things.

 

[shortstop20]

Lean and detonating are 2 different things.

If it's lean it will detonate, so what's the difference?

 

[voodoo]

If it's lean it will detonate, so what's the difference?

Not necessarily, I'll let someone else write the book, my answer will be short. Detonation is actually pe-ignition. This means the mixture starts to burn too early. The octane of the fuel retards the burn. So if you have radical compression or timing the high octane resists pre-ignition. That's why if you run race gas in a low compression engine they run like ****. If boosted applications are different I'll let someone else elaborate.

Lean is a lack of fuel or the air/uel mixture has too much air. It burns hot and fast and overheats parts. Pistons destroyed by detonation typically look different than pistons that get destroyed by lean. Lean burndowns usually take off the leading edge of the piston near the exhaust port. They look melted. Detonation usually holes a piston and sometimes sticks a piston because the rapid heating of the psiton causes it to swell too fast and they stick. You can also destroy ringlands with detonation as it is like a jackhammer on the piston edges hence the "pinging" sound. If you have **** gas but a ton of it you may not detonate or the detonation may be light enough parts aren't destroyed due to the over-rich condition. Once you started leaning on bad gas bad things happen. They can go hand in hand and depending on the length of time thse bad things happen you can have a piston in such bad shape it is hard to figure out what the true cause is.

Word to the wise, don't lean your 800 down with good gas and expect the DET to save you. You will be disappointed with the results.

 

[penguinpoo]

Not necessarily, I'll let someone else write the book, my answer will be short. Detonation is actually pe-ignition. This means the mixture starts to burn too early.]
Pre-ignition often leads to detonation but is not detonation. Pre-ignition is caused by an ignition source before the spark occurs. Hot carbon or glowing piece of metal(broken plug thread or too hot of spark plug for instance).

 

[AKSNOWRIDER]

detonation is the fuel/air mixture exploding uncontrollable in the combustion chamber..normally caused by too much compression for the octane of the fuel,too lean of a condition can advance an engine into detonation but doesnt cause it.if it happens bad enough(as in a big amount of nitrous or on a nitromethane drag motor) it can actually flatten bearings,bend connecting rods, bend crank throws..normally piston fails long before this but I have had it pound rod bearings flat on a big block nitrous motor running 2 500 hp fogger kits...yes it was expensive to fix...guy I bought fuel from gave me 110 octane instead of 118....at 15.5 to 1 compression and dumping 7 pds of nitrous out of each kit in a 200 ft pass you have to have the right octane...

 

[Ron]

Here are some textbook definitions that might help (confusing terms for most of us). Some of the same factors contribute to both conditions:

Detonation (also called "spark knock") is an erratic form of combustion that can cause head gasket failure as well as other engine damage. Detonation occurs when excessive heat and pressure in the combustion chamber cause the air/fuel mixture to autoignite. This produces multiple flame fronts within the combustion chamber instead of a single flame kernel. When these multiple flames collide, they do so with explosive force that produces a sudden rise in cylinder pressure accompanied by a sharp metallic pinging or knocking noise. The hammer-like shock waves created by detonation subject the head gasket, piston, rings, spark plug and rod bearings to severe overloading.

Another condition that is sometimes confused with detonation is "preignition." This occurs when a point within the combustion chamber becomes so hot that it becomes a source of ignition and causes the fuel to ignite before the spark plug fires. Preignition, in turn, may contribute to or cause a detonation problem.

Potential detonation causes:
Rich fuel mixtures resist detonation while lean ones do not.
Lower octane rated fuel
Higher engine compression
Ignition timing advance
Wrong heat range plug
Engine overheating
Accumulation of carbon deposits
Preignition

 

[shortstop20]

Detonation occurs when excessive heat and pressure in the combustion chamber cause the air/fuel mixture to autoignite. This produces multiple flame fronts within the combustion chamber instead of a single flame kernel.

......and those flame fronts pound and pound on metal parts before the mixture was meant to be burnt, a lean condition does the same thing doesn't it? .......burn before it is meant to, pounding on the piston, bearings, rods, crank, etc. correct? Detonation is "knock", won't the motor knock from a lean condition?

Let me put it this way, if the fuel/air mixture is lean, does it still burn at the correct time, but just too fast(heating up all the parts and stressing them), or does it burn too early like detonation? Just when I thought I had it figured out you guys throw me a ringer. I like to learn though so I don't mind.

 

[penguinpoo]

Too lean a condition makes conditions favorable for detonation to occur, but doesn't necessarily cause detonation every time. Think about a lean low speed stumble. Pressures are too low in the cylinder for detonation, but there is not enough fuel in the mixture to support a stable burn.

 

[AKSNOWRIDER]

......and those flame fronts pound and pound on metal parts before the mixture was meant to be burnt, a lean condition does the same thing doesn't it? .......burn before it is meant to, pounding on the piston, bearings, rods, crank, etc. correct? Detonation is "knock", won't the motor knock from a lean condition?

Let me put it this way, if the fuel/air mixture is lean, does it still burn at the correct time, but just too fast(heating up all the parts and stressing them), or does it burn too early like detonation? Just when I thought I had it figured out you guys throw me a ringer. I like to learn though so I don't mind.

when the motor goes lean, it acts like a cutting torch inside the chambers....lean melts things....(normally seen as the exhaust side piston ring lands melted..where as detonation breaks the lands off...

 

[Koodat]

So what about getting the light operational? Anybody done it?

 

[AKSNOWRIDER]

So what about getting the light operational? Anybody done it?

carls cycle makes it work when they reflash for a bigbore/ porting and such...

 

[Ron]

Rpm

How valid was the DynoTech run on the stock 800? I've had a nagging doubt for a while & as I mentioned several times-peak power on the DTR run was far below what worked in the snow last year. Jim made a point at one time that they ran the pipe smoking hot, another time mentioned that SLP getting power at higher R's was probably running a hot pipe. Just got my service manual from Polaris and they have peak HP at 8250. So by my tally it's Polaris, SLP & practical experience in the field with peak HP at 8200+. DTR at 7900!
If elevation doesn't make a difference (DTR statement), then the only logical conclusion is that the dyno run didn't last long enough to get the pipe as hot as we see in the snow. Or they had sled, fuel, warm ambient air temps, or other issues?
If the air/fuel ratio is rich at 7900 what happens at 8250? HIgher R's the engine pumps more air-might this result in a leaner mix?

 

[hilinerider]

leaner = power =


this is also one reason why seat of the pants feel isn't up to par unless you get the r's up,

just what i seen on the snow, i don't ride my sled on a dyno so i wouldn't know what that would feel like

 

[dynotechjim]

Ron thanks for keeping this going on--the RPM where you get best HP is totally dependent upon pipe center section temperature. When we talk about pipe center section temp we are referring to average temp of the gas in the tuned pipe from front to back. That temp affects the speed of sound, the higher the temp the higher the speed of sound and the higher RPM peak HP will occur. The laws of physics occur here, not the laws of DynoTech.

My next quest is to find an open element exhaust probe 3-4" long that will reach into the middle of the pipe's center section where temperature is most accurate. The typical ex probes we fit to the pipes' center sections only measure the outside 1" or so because they're designed to fit in narrow Ypipes, and we need to get deep into the center section body to measure what's happening there more accurately.

If everyone could have such a long EG probe in their center section they could know exactly where their HP peak occurs at every temperature, from data obtained on a fully instrumented dyno.