rpm loss with hps can

farmboy88 · Jan 3, 2012

I have a pro rmk 163 with 700 miles on it. It reved 8200-8250 consistently at 8000 feet with 62 gram weights. I put an hps can on, and now it wont rev over 8050. Tried putting lighter weights in and no change. Can anyone help me???

trackvs2wheels · Jan 3, 2012

Did this occur after the sled sat for the summer?

If so, I'd be freshing up the primary and secondary springs and I bet you get your rpm back!!

Just a thought...

farmboy88 · Jan 3, 2012

It had sat all summer, but did ride it with stock can and was fine. I have a friend that has a new 2012crossover pro and is having the same issue.

AndrettiDog · Jan 3, 2012

trackvs2wheels said:
Did this occur after the sled sat for the summer?

If so, I'd be freshing up the primary and secondary springs and I bet you get your rpm back!!

Just a thought...

I'm wondering the same thing. I have a Pro with 1200 miles on it and I haven't changed the primary spring. I put an HPS can on at the beginning of this year and I've lost a good 200 RPM. I'm going to buy a new spring this week.

farmboy88 · Jan 3, 2012

BugIto, please keep me posted!

MNSLEDNECK56308 · Jan 3, 2012

Bug... Interested as well, installing my HPS tonight.

rmk2112 · Jan 3, 2012

Installing a new primary and secondary spring every year is like changing your oil every 3000 miles. It's a given.

$12K sled and spending $40 a year on springs is nothing, if you want peak performance all the time, it's nessacary IMO.

Boston Racing · Jan 3, 2012

Take 5 minutes to put the stock can back on and see if the rpm's come back. If not replace the springs.

Is it possible for a can to lose power resulting in the lower rpm's?....yea but the HPS cans have a very loyal following claiming they have to increase the flyweight due to the additional power.

AndrettiDog · Jan 3, 2012

Before we all chalk up RPM lose to bad clutching do a little searching. There are a lot of people questioning the HPS can for the Pro. Yeah it sounds crazy good. But things are happening with it on. I don't have consistent evidence yet but I'm working on it. There are a couple other people that I know have said the same thing. I'm waiting on them to chyme in.

t stone · Jan 3, 2012

I have that can on mine and it runs up at 8150-8250 all day long until I lost rpm last saterday. Would only pull 7800 tops. Broken primary spring with 150 miles on the sled. IMO is the springs

Stone

crf118r · Jan 3, 2012

Hell, my stock can sounds great and the sled runs 8250-8300 all day long... and it didn't cost me $300+. Just sayin' :face-icon-small-win

granto · Jan 3, 2012

I agree with boston racing put the stock can back on and see if the problem is still there. this will tell you if its the can or the clutching. I have a jaws on mine and have zero issues it pulls 8200 to 8250 all day.

farmboy88 · Jan 3, 2012

i will put stock can back on and if it doesnt change then i will investigate the springs. i am just baffled because like i said in an earlier post my friend has a brand new pro and is experiencing the same problem. his springs should be fine. anyway, will go to the hills saturday and do some testing. is it possible the can is not letting the pipe get hot enough therefore not allowing peak rpm??? just a thought, i am stumped!!!

polaris6 · Jan 3, 2012

If there is not identical back pressure with any aftermarket can it will affect performance. The entire set up is a tuned closed loop system that can't compensate for loss/gain of stock exhaust pressure and stock shock wave resonance. I looked real hard at all the cans and not 1 manufacturer will guarantee or give evidence that their can has identical back pressure. They claim weight savings and better performance. Ask yourself where is ANY dyno evidence that a can alone will not hurt or improve performance from stock. There is none. If there was I would already have on on my sled. Not bashing any can makers, but you need to be careful with adding anything on these new cfi sleds that affects the air, fuel, or exhaust on the tuned system. Good luck with the testing and I look forward to your results from Saturday with the stock can vs the hps.

HiWaYman92 · Jan 3, 2012

ditto

I just changed back to the stock can and traded out my slp blue/pink spring this morning and got my rpms back. Two changes at once, so not sure which one did the trick. A spring that had 500 miles on it replacing a spring with 500 miles on, or the can. A buddy has the exact same sled with an MBRP can. No rpm loss. HPS can for sale.

t stone · Jan 3, 2012

HiWaYman92 said:
I just changed back to the stock can and traded out my slp blue/pink spring this morning and got my rpms back. Two changes at once, so not sure which one did the trick. A spring that had 500 miles on it replacing a spring with 500 miles on, or the can. A buddy has the exact same sled with an MBRP can. No rpm loss. HPS can for sale.

Why didnt you do one change at a time? It would be nice to realy know what the fix was. I bet it was the spring.

Stone

HiWaYman92 · Jan 3, 2012

One only has so many chances to ride. I was desperate to get the rrrs back so I changed both. Now that I got it I can put the can back on and try it.

R44guy · Jan 3, 2012

polaris6 said:
If there is not identical back pressure with any aftermarket can it will affect performance. The entire set up is a tuned closed loop system that can't compensate for loss/gain of stock exhaust pressure and stock shock wave resonance. I looked real hard at all the cans and not 1 manufacturer will guarantee or give evidence that their can has identical back pressure. They claim weight savings and better performance. Ask yourself where is ANY dyno evidence that a can alone will not hurt or improve performance from stock. There is none. If there was I would already have on on my sled. Not bashing any can makers, but you need to be careful with adding anything on these new cfi sleds that affects the air, fuel, or exhaust on the tuned system. Good luck with the testing and I look forward to your results from Saturday with the stock can vs the hps.

P6, You sure called that as fact! I have tried several style cans/mufflers and on the dyno they just lose power and your right on with too much or too little flow changes everything on these CFI Polaris motors. The only 2 advantages a can gives you is weight savings and sound if that is what your looking for ? Now pipes do help with some power gains but in general only with the stock poo muffler/can.

farmboy88 · Jan 8, 2012

well, had a chance to do some testing yesterday. put the stock can on and only gained about 100 rpms back. bottom and mid range throttle response really seemed to suffer when i put the stock can on. i put a new belt on, and changed my weights to 60 grams. i put the hps can back on, and man that sled came to life. 8200-8250 the rest of the day. i now have faith in the hps can! going to put new springs in too, so it can only get better. still wondering why i had to drop weight, but really dont care at this point...the sled rips now! i know cans arent supposed to do anything but reduce weight and make noise, but the hps can really seems to wake up the sled bottom through mid range. have two other friends with pros and they both agree. my friend who has the new pro found out his clutch was binding, thats why he couldnt get his rpms. he put a different clutch on and it was fine.

rpm loss with hps can

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