Real World Dyno

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Essarex

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Dec 1, 2007
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I'm having trouble justifying to myself why dyno results do not always correlate to the on-trail results. For example, the Apex consistently beats the other big sleds in the 1/4 mile and on top end (XP, IQ, F1000, etc) even though it has less dyno hp and is heavier. How can this be? Torque is the common response to this question, but in reality the torque is higher for all the sleds I mentioned at the shiftout rpm, hence the higher hp numbers.

Yesterday I ran against an Apex with my Bender ported and VForce reeded SRX. A 2002 SRX with porting/reeds should make close to 160 hp. I have a Drag&Fly setup that was shifting out perfectly for the conditions, 8500. No under or over rev. I also have a 1 1/4 camo 6 pitch and expert x rear suspension that hooks like crazy. At launch, I jumped 2 lengths, held this for 100 feet, then he caught and passed me and held 2 lengths until we let up.

Based on "dyno" numbers, the heavier Apex with less hp should not have been able to do what he did.

Anybody have a good explanation?
 
Your not making 160 hp. Porting should net about 5-7 hp at the very most. The HP numbers I see here on TY are off the charts. Reeds nothing. Yamaha reeds are very best straight from the factory. You can't improve the reeds.
 
Not sure with porting, but 8500 is high for an SRX. 8400 is perfect. What gearing do you have in it? Do you have a can on it? 1 1/4 track is going to cost you a little, what height was his? How far did you run?

Light weight could get you out front early, but great torque catches him up. If you hold it for a mile, you'd probably go by him again.
 
OK, only 5 - 7 hp would explain the Apex pulling away, but what is the explanation for the 12 - 14 hp that shows up on an engine dyno?

Is it the dyno operator running way lean jetting, with a cold motor and hot pipes? Or is there another way to 'fool' the dyno thru manipulation of the load control?
 
DOUBT YOU HAVE 160 HP AND STILL BEING A 700 cc. YOUR V -FORCE REEDS FORGET IT, THEY AIN,T ADDING ANYTHING. PORTING, MAYBE 6 HP. SO THAT PUTS YA SAME HAS THAT APPEX AT AROUND 150. NOW THIS IS VERY SIMPLE. SET-UP, CONDITIONS, HORSEPOWER YOU THINK YOU HAVE, BUT DON,T. HORSEPOWER THE GUY YOUR RACING HAS BUT DOSE NOT TELL YA. I RUN A WELL SET-UP STOCK 2002 SRX WITH DEAD ON CLUTCHING. MARGINAL SNOW I CAN BEAT SOME APPEX,s. SNOW CONDITIONS CHANGE THEY WILL BEAT ME. 3:16 (yammie tony)
 
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Thanks for all the responses. Still, how does the 149 hp 580 lb Apex out accelerate and top end a 154 hp 470 lb 800IQ? The 800IQ is making more torque than the Apex at shift-out rpm (where both sleds settle in during the run).

????
 
bender trail port w/ vforce 2's & bender can is 158 - 160 h.p. on dyno @ 8500. don't know much about the expert x but i do know the m10 will knock 8-10 mph off top end. ran my bender trail port srx on radar many times & always about 8 mph faster than a good running apex.

bob
 
A dyno run from the motor is worthless. You need a track dyno to let you know what power is put to the ground. Just like in cars, bikes, etc.....
 
THAT EXPERT X SKID IS KILLING YOUR MPH I SHOULD OF ADDED IN MY POST. FARR AS THE APPEX AGAINST THE IQ, 4 HP DEFFERENCE AIN,T THAT MUCH, MAYBE THE YAMAHA CLUTCHING IS BETTER THAN THE POLARIS. BOB, VERY HARD FOR ME TO BELIEVE YOU GET 15 HP WITH V-FORCE REEDS, TRAIL PORT, AND A CAN. BUT YOU GO TO THE DYNO ALOT SO WHO KNOWS. 3:16 (yammie tony)
 
Essarex said:
Thanks for all the responses. Still, how does the 149 hp 580 lb Apex out accelerate and top end a 154 hp 470 lb 800IQ? The 800IQ is making more torque than the Apex at shift-out rpm (where both sleds settle in during the run).
????
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chassis friction?
 
tony:

safe trail bsfc on the dyno is high 150's. leaned out for short runs is low 160's.
i think the expert x is killing his top end. never used dragon flys but the 8dn's work well w/ that motor.

bob
 
bufalobob said:
bender trail port w/ vforce 2's & bender can is 158 - 160 h.p. on dyno @ 8500. don't know much about the expert x but i do know the m10 will knock 8-10 mph off top end. ran my bender trail port srx on radar many times & always about 8 mph faster than a good running apex.

bob
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maybe on yours because you seem to know them very well,but on mine i was sadly dissapointed.my self ported with race logic templates 98' could wax my bender ported 01' .after trying a hundred different set ups i pulled the cylinders off and mapped the ports to find that the bender porting was much less agressive than my templates. i'd say 5-8 h.p max for what was done to mine.maybe the guy on the pin grinder that day had a bad hangover?lol.
 
BOB, I AGREE THAT SKID AIN,T FOR RACING AND SCUFFING MPH BIG TIME. GREAT IF THERE RACING ACROSS MOGULS. AND HEY I LIKE TO THINK MY 2000 WITH PORTED CYLS IS IN THE 150,s. NEED TO GET IT TO JIM,S. 3:16 (yammie tony)
 
snogoer's latest mag dynoed the polaris 800 at 144hp. they contacted polaris who said they had some warranty probs on the spring releases. so they fattend up but that they expect it to be in the 149 150 range. Hp # sell so they leave it high I geuss. The claim hp that is.
 
WHy do you guys say the expert x hurts on the big end? I was under the impression they had very little rolling resistance. Which they do per my experience. So the pro action is a better top end susp.? Lets hear it.
 
If you throw a long travel skid in a short travelled sled... The geomtry is Hurtin in all aspects of speed. Low is go go go.
 
Yamidude59 said:
If you throw a long travel skid in a short travelled sled... The geomtry is Hurtin in all aspects of speed. Low is go go go.
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Agreed but you can lower the ride hieght on an expert x to about 7 inches or crank it up to 11". About a 2 minute ordeal trail side. Still wondering why an X scubs top end?
 
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