The biggest difference that separates the 07 from the rest is the cooling system.
The 07 does not have a thermostat system.
If on a hard pull and the coolant system is getting lots of snow the coolant temperature can become lower, overtaking the heat produced by the enigne under w.o.throttle - timing/fuel comp/rave opening start to vary to limit the output on the engine as the climb increases and suck the engine down to 7500 rpms.
On Mar 21st, last Saturday morning I sat with Turbo Al for an hour discussing what I seen when I was at Dynotech running an 08xp. The engine ran at best power when the coolant temp from the head was below 141 degrees. When up to 140 the engine produce 151hp, when at 141, lost 8 hp or so and Turbo Al confirms this happens. His mechanic has an 07R with a mechanical coolant temp gage on the engine and started to observe the same thing all the time; when the temperature reaches about 98 degF on the crankcase, the engine starts to drift rpms, drifting lower on a pull that is just hard enough to maintain peak rpms. Keep the case temp above 98 and runs fine. Start to get cooler than 98 and rpms drift low.
Mike blew the 07R engine, got an 08 engine installed under warranty....
Mike asked the mechanic "are you going to put a thermostat in it?"
Dealer said "no, the 07R does not have a thermostat"
Mike "but this is an 08 engine with changes that were reasoned upon the failures of the 07 engine which require a thermostat.
Dealer "too bad, we're not doing it"
Dealer did not want to put a thermostat in....Turbo Al did.
Now the engine runs at correct temperature all the time and rpms fluctuate due to load....not coolant temp. So now he has an 07R with a thermostat installed.
The 08 comes with bypass thermostat now...WHY???
Quote brp "to ensure consistent engine temperatures"
Why does the engine need consistent engine temperatures? Could it be because the coolant system has the capacity to overcome the engine heat under wide open throttle?
Could it be, because the coolant sensor tells the ECU to pull timing out? IF temp gets low - THEN pull timing out.
IF buying an 07R,
THEN think about modifying the coolant system to incorporate a thermostat.
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Its like guys who put boondocker timing systems on other sleds, Cat's, SDI's, Poo's; They make a change to the box and observe the change did not change the personality of the sled, or it only works sometimes. The boondocker must see proper coolant temp before the box will take over different timing.
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One way to tell is when you have had fluctuating rpms from coolant temp, if you can stop somewhere at the top of a run and let the engine idle for about less than a minute, then drive away, you'll see the snow will have a black/brown discolor in about a foot diameter...black slobbering crap. A hot engine won't reveal a patch that big when idling, then pull away.
How does an engine produce puke big slobbering exhaust? Adjusted timing/fuel compensation/rave opening settings at reduced power.
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Why does a clutch calibration work good for about a 1/2 hour of running then just stop working good and have drifting low rpms?
I have been observing comments of my clutch kits for 08 models vs 07 models.
Seems when gents have fluctuating rpms then can fix with flyweight change.
If making a change then I have the tuner check their clutch parts.
More likely than not the tuner tears down the primary and finds wobbling rollers, the bushings are worn. Sliding sheave bushing worn.
...change to new parts and the sled is like new again.
Now do this on an 07
Seems when gents have fluctuating rpms then can fix with flyweight change.
If making a change then I have the tuner check their clutch parts.
More likely than not the tuner tears down the primary and finds wobbling rollers, the bushings are worn. Sliding sheave bushing worn.
...change to new parts and the sled is like new again for only certain periods of time. Clutch calibration work good for about a 1/2 hour of running then just stop working good and have drifting low rpms.
Over the weekend I worked on 2 xp154's and both had worn rollers and sliding sheave bushings. The one the rollers were cut right into the pins. The clutches were checked on last Wednesday and rollers seemed fine then over the weekend run 120 miles put on them 2 tanks of gas each and Sunday night strip down clutches and rollers need changing.
WHY?
Totally disgusted!!!!!!!
