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Old 12-28-2009, 11:33 AM   #1 (permalink)
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Is the peak horsepower band at 8600 RPMs?? See Amsnow article below.



1999 Indy 800 XCR
The Storm has passed. In its wake comes a new breed of power
By AmSnow staff
Published: Tuesday, September 01, 1998
Our first glimpse of Polaris' new 800 XCR came at Canterbury Park near Minneapolis, Minnesota, last January. At the unveiling, Polaris Snowmobile General Manager Bob Nygaard boasted that this new machine was significantly
stronger at both the top end and the midrange. We listened, but reserved judgment until we could see for ourselves at our spring test session, and hopefully on a dyno. Afterall, it ain't braggin' if it's doin' and this brand new motor showed us it's definitely doin'!

As usual, our resourceful dyno guys commandeered an early release of the hot new 794cc Fuji mill as we requested. Based on what we've seen on the dyno, we can truthfully say that this is the strongest production 800 motor ever!

The new motor uses RAVE-like variable exhaust valves, actuated by pressure in the cylinders to smooth out the acceleration curve and gain another four to six horsepower in the midrange. What makes the Polaris Variable Exhaust System different is that the guillotine valve opens and closes the subports on either side of the main exhaust port, where Rotax's design only modifies the main center port. "The fact that Polaris' design handles all the port openings instead of only one definitely helps it make its power," explained Dynoport's Rich Daly.

The powerband is extremely generous on this new motor. Tuners have a 400 rpm spread to hit for more than 155 horsepower. Our test sled hit its peak at 159.2 ponies at 8600 rpm. "We wanted to get it to hit 160," said Daly. "We hit peak power on the third pull. The pipes definitely like to be heated up, but not over-heated."

One of the many new features on the XCR is a temperature sensor which automatically retards the timing if the water sensor exceeds 160 to 170degrees Fahrenheit. The sensor is also throttle-position sensitive, so at trail speeds, it allows for slightly hotter running temperatures before it begins its fail-safe mode. If the water gets significantly hotter once the timing has been modified, it will begin a controlled misfire.

Other engine safety features of the new mill include an overrev limiter, which will not allow the motor to run at unhealthy speeds. There is also a Low Octane/ Premium fuel switch onboard the sled. This allows owners to make a slight timing change based on the quality of the fuel available. "We played with the fuel switch a little," reported Daly. "We found it richened up the motor by about one or two main jets. That's a nice feature for guys who ride in rural areas where gas quality can be sketchy. The richening didn't affect performance enough to be noticed from the seat."

Daly estimated that there is definitely some room for aftermarket shops to massage more power out of the new motor. "You can expect to see about 10 more horses from a set of pipes. Silencers can add three to four more. It should be responsive to porting, too, since it has such a broad powerband."

Polaris is finally offering a competitive sled in the 800 class. It has the power and torque throughout the operating range to satisfy both lake runners and trail riders.

1999 Polaris Indy 800 XCR
Air Density: 98.0
Fuel: 94 Octane Pump Gas
RPM CBT CBHP BSFC FUEL H2O
5600 65.0 69.3 .84 57.3 99.0
5700 65.3 70.8 .80 56.3 99.5
5800 65.6 72.4 .79 56.8 99.5
5900 66.8 75.0 . 77 57.0 99.5
6000 68.0 77.6 .75 57.6 99.5
6100 68.3 79.4 .74 58.4 100.0
6200 68.8 81.2 .75 59.9 100.0
6300 68.9 82.7 .76 61.8 100.0

6400 70.4 85.8 .76 64.3 100.5
6500 73.7 91.2 .75 67.5 100.5
6600 76.5 96.2 .75 71.0 100.5
6700 79.4 101.3 .74 74.1 100.5
6800 83.1 107.6 .71 75.8 100.5
6900 83.8 110.1 .72 78.7 100.5
7000 87.1 116.0 .70 80.1 100.5
7100 87.4 118.2 .70 82.3 100.5
7200 89.6 122.8 .68 83.1 100.5
7300 89.7 124.7 .68 83.5 100.5
7400 90.3 127.2 .67 84.7 101.0
7500 90.1 128.7 .68 86.0 101.0
7600 90.0 130.2 .68 88.1 101.5
7700 90.3 132.4 .69 90.7 101.5
7800 90.8 134.8 .69 91.6 102.0
7900 91.4 137.4 .68 92.0 101.5
8000 92.3 140.6 .67 93.1 102.0
8100 94.3 145.5 .66 94.8 102.5
8200 95.0 148.3 .65 95.8 103.0
8300 96.9 153.1 .63 95.2 103.0
8400 97.4 155.8 .62 95.7 103.5
8500 98.2 158.9 .63 99.2 103.5
8600 97.2 159.2 .64 100.6103.5
8700 95.0 157.3 .64 99.5 104.0
8800 92.4 154.8 .65 99.2 104.5
8900 89.4 151.5 .68 101.9104.5
9000 86.0 147.3 .71 103.4105.0
9098 81.8 141.7 .75 104.8105.0



RPM: Engine crankshaft speed.
CBT: Corrected Brake Torque.
CBHP: Corrected Brake Horsepower.
BSFC: Brake Specific Fuel Consumption.
FUEL: Actual fuel flow pounds per hour.
H2O: Water temperature in degrees F.
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Old 12-28-2009, 12:45 PM   #2 (permalink)
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I saw another dyno sheet that showed it peaked at 8500-8600 rpm as well. Highwayheavy has told me he saw best radar speeds running at 8600-8700 rpm. Mine has gone 119+ mph on GPS with the tack sitting at 8900 so there definitely still making power at hight rpms. BUT its pretty much been proven for drag racing to run them at 8-81 off the line and let it climb up to 8300. The way these dyno sheets read it would seem the stock clutching is almost perfect but who runs stock clutching in there XCR? With cold pipes mine hits 7800 off the line and with hot pipes it will hit 8200 and is making allot more power.
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Old 12-28-2009, 03:00 PM   #3 (permalink)
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I saw another dyno sheet that showed it peaked at 8500-8600 rpm as well. Highwayheavy has told me he saw best radar speeds running at 8600-8700 rpm. Mine has gone 119+ mph on GPS with the tack sitting at 8900 so there definitely still making power at hight rpms. BUT its pretty much been proven for drag racing to run them at 8-81 off the line and let it climb up to 8300. The way these dyno sheets read it would seem the stock clutching is almost perfect but who runs stock clutching in there XCR? With cold pipes mine hits 7800 off the line and with hot pipes it will hit 8200 and is making allot more power.[/b]

here is part of the dyno run from dt a stock 99 with 420 mains

RPM CBT CBHP BSCF
7900 101.4 152.5 0 0.707 105.6 0 55 95
8000 101.5 154.6 0 0.735 111.4 0 54 95
8100 101.3 156.2 0 0.707 108.3 0 54 95
8200 100.2 156.4 0 0.759 116.4 0 54 95
8300 98.4 155.5 0 0.726 110.7 0 54 95
8400 96.1 153.7 0 0.735 111.1 0 52 96
8500 91.1 147.4 0 0.789 114.2 0 53 96

even at the end of the tuning from this report 8100 - 8300 seem to be the magic # on a stock ported motor
with OEM or Aftermarket Pipes
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Old 12-28-2009, 08:33 PM   #4 (permalink)
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Don't believe the dyno tests. It's not real world. When you drag race, you don't have a hot engine/pipes. 8100-8200 is peak hp. A long run might need 8300-8500. I can't tell you how many 8500-8700 rpm XCRs I've smoked. NEVER, EVER, been beaten by one running at those rpms.

Like Larry Rugland once told me: "You don't race dynos. If you did, we would all just send in our dyno sheets".

I've spent years finding what rpm works best.
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Old 12-28-2009, 08:49 PM   #5 (permalink)
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Quote:
Don't believe the dyno tests. It's not real world. When you drag race, you don't have a hot engine/pipes. 8100-8200 is peak hp. A long run might need 8300-8500. I can't tell you how many 8500-8700 rpm XCRs I've smoked. NEVER, EVER, been beaten by one running at those rpms.

Like Larry Rugland once told me: "You don't race dynos. If you did, we would all just send in our dyno sheets".

I've spent years finding what rpm works best.[/b]
When I purchased my clutch kit from Goodwin they said target was 8100-8300 RPMs. I trust Greg for clutching.
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Old 12-28-2009, 08:58 PM   #6 (permalink)
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When I purchased my clutch kit from Goodwin they said target was 8100-8300 RPMs. I trust Greg for clutching.[/b]
Maybe on a non- calibrated tach to 8,300.
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Old 12-28-2009, 09:17 PM   #7 (permalink)
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Don't believe the dyno tests. It's not real world. When you drag race, you don't have a hot engine/pipes. 8100-8200 is peak hp. A long run might need 8300-8500. I can't tell you how many 8500-8700 rpm XCRs I've smoked. NEVER, EVER, been beaten by one running at those rpms.

Like Larry Rugland once told me: "You don't race dynos. If you did, we would all just send in our dyno sheets".

I've spent years finding what rpm works best.[/b]

what I have always taken away from dyno measuremants
is the RPM of the peak torq and peak HP not the actual tq # or hp # as that
would more than likley be the variant

the consistent # should be the rpm from my understanding
of reading a few of the dyno sheets I have seen

I hope my clutching get me close to if not the peak tq rpm on the hit and let it run to the peak hp rpm

in my book tq gets me there hp keeps me there

howerver if there is conflicting dyno measurements of what rpm peak tq and peak hp are being measured at
then something is not right one of the dynos is wrong..


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Old 12-28-2009, 09:26 PM   #8 (permalink)
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Dynos don't create the same conditions seen in the field. They usually control rate of rpm increase by a pre-selected program. They don't usually have the effects of cold air on the pipes. They don't measure acceleration rate or throttle response. NOT REAL WORLD!

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Old 12-28-2009, 10:42 PM   #9 (permalink)
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Just for the heck of it at the shoot out I can remove weight make my XCR run at 85-8600 just to see what happens.
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Old 12-29-2009, 07:57 AM   #10 (permalink)
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Just for the heck of it at the shoot out I can remove weight make my XCR run at 85-8600 just to see what happens.[/b]
Good luck. I can predict the results based on personal testing against a similarly setup pace sled over 9 years. I bought a brand new set of Dynoport pipes for my 800 a few years ago. As I remember, the instructions were to use near stock 440 mains and 8500 rpm. My BIL and I compared acceleration on ice. He beat me pretty badly for a change. So, I added more weight to my Heel Clickers and reduced mains to 400s until it pulled rpms down to 81-8200. I finally was back to identical to stock pipe performance. I was beating him as before. What a waste of $800. Removed the pipes and went back to stock pipes. He wrecked his sled and damaged his stock pipes, so purchased the Dynoports from me. Didn't do anything for his Flannery-ported sled either. Feedback and comparisons with other stock piped, non-ported and ported/piped XCR 800s over the years confirms this. :beer_cheers:
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