Xm turbo gearing

ktmsx350f

Active VIP Member
Joined
Nov 9, 2014
Messages
587
Reaction score
514
Location
fort mcmurray
163 T3 xm 7-8 psi BD setup. What gearing combinations are guys using and really liking ? Doing a service and I have quite a few different gears for the skidoo and a few different chains so woundering what guys are liking
 

mountainsledmania

Active VIP Member
Joined
Dec 28, 2009
Messages
1,187
Reaction score
1,231
Location
sherwoodpark
i run 2.42 and i think its a great choice. but with the boost your running i think you can get away with 2.33. I haven't tried 2.33 but from what i understand it has benefits of spooling the turbo. Im curious what everyone else is running as well. the 163 t3 comes with 2.42 gearing factory.
 

ktmsx350f

Active VIP Member
Joined
Nov 9, 2014
Messages
587
Reaction score
514
Location
fort mcmurray
The lower ratio will definitely load the turbo harder and make it spool. I was thinking of trying a 21-49 2.33 or 23-51 2.21. Have both setups and got a cabin coming
 

NoBrakes!

Active VIP Member
Joined
Nov 13, 2011
Messages
6,002
Reaction score
11,802
Location
Edmonton
Silly question, is there more than 1 combo to achieve the same ratio and if so is there a benefit to bigger vs smaller top/bottom? Just trying to sharpen up...
 

oler1234

Active VIP Member
Joined
Nov 20, 2008
Messages
3,592
Reaction score
5,976
Location
Calgary, AB & Golden, BC
The lower ratio will definitely load the turbo harder and make it spool. I was thinking of trying a 21-49 2.33 or 23-51 2.21. Have both setups and got a cabin coming


23:51, yup make it so difficult that the sled won’t really move until it’s on boost. Seems logical with a 1:1 shift at 130km/hr let alone what overdrive would yield.


load the motor and build exhaust heat through clutching and fuel.

Best results for myself are agressive helix angles and tuning your fuel box to give a small burst of fuel down low for 500rpm time frame, no more. Fuel should only be added on a base map (not boost) for 80% throttle opening just before spool up.
 

ktmsx350f

Active VIP Member
Joined
Nov 9, 2014
Messages
587
Reaction score
514
Location
fort mcmurray
With the gtx it makes boost almost instantly. It’s has no lack of bottom end and clutching is great and it already has an aggressive helix. It has way more then enough power to handle more gearing. It doesn’t need any more bottom end it’s about as good as a etec with a turbo will get but you can tell it spins the track effortlessly in deep snow it could easily have more gearing. With the gtx it makes more power at 5psi then another kit did at 8-9 at 8-10 it pulls hard you can tell it could easily handle more gearing.
 

oler1234

Active VIP Member
Joined
Nov 20, 2008
Messages
3,592
Reaction score
5,976
Location
Calgary, AB & Golden, BC
to get a proper idea of what gearing you should run from opinions of others you need to list specific details of clutching, gearing, turbo size, when seeking the opinons of others. Other than that its just internet talk. Who knows mayby someone has run a similar setup with success or failure.
 

ktmsx350f

Active VIP Member
Joined
Nov 9, 2014
Messages
587
Reaction score
514
Location
fort mcmurray
Most 800’s will always run a 2860 when using a Garrett but I can post more details on clutching. Most turbos make more then enough power to benefit from a hearing change
 

Lund

Active VIP Member
Joined
May 4, 2013
Messages
4,243
Reaction score
11,242
Location
Vernon/Kelowna
Well it sounds like you guys really know what your talking about on this thread LOL.
Changing your gearing will basically do one thing, change where the belt operates on your clutches. It DOES NOT change when boost comes in as stated below.

23:51, yup make it so difficult that the sled won’t really move until it’s on boost. Seems logical with a 1:1 shift at 130km/hr let alone what overdrive would yield.

Engagement speed is is engagement speed, controlled by the spring and weights in the clutches and gearing changes will NOT effect engagement speed of the motor.
But like i said it will effect where the drive belt operates in the clutches, low gearing will cause the belt to use the higher portion of the clutch while taller gears will cause it to use the lower portion of the clutch.
Here is the deal, clutches operate most effectively in the upper 2/3, best belt bite. But not all clutches can be operated in that area as it needs to be effective also in the lower 1/3 and shifting out. Why, HEAT. When you gear up (taller gears)you essentially increase the load through the entire range on the belt. When you increase the load you also increase the heat.
Like i said some clutches handle getting geared up, while some don't like it and you end up chasing your tail with clutching issues.
BRP clutches already run too hot and taller gears will just amplify the heat and eventual belt failures that they are already known for.
If you do gear up as your saying, expect much hotter clutches, even with boost.

Sorry i made a correction in my post, i had it reversed and didn't notice till i reread it.
 
Last edited:

ktmsx350f

Active VIP Member
Joined
Nov 9, 2014
Messages
587
Reaction score
514
Location
fort mcmurray
Well it sounds like you guys really know what your talking about on this thread LOL.
Changing your gearing will basically do one thing, change where the belt operates on your clutches. It DOES NOT change when boost comes in as stated below.

23:51, yup make it so difficult that the sled won’t really move until it’s on boost. Seems logical with a 1:1 shift at 130km/hr let alone what overdrive would yield.

Engagement speed is is engagement speed, controlled by the spring and weights in the clutches and gearing changes will NOT effect engagement speed of the motor.
But like i said it will effect where the drive belt operates in the clutches, low gearing will cause the belt to use the higher portion of the clutch while taller gears will cause it to use the lower portion of the clutch.
Here is the deal, clutches operate most effectively in the upper 2/3, best belt bite. But not all clutches can be operated in that area as it needs to be effective also in the lower 1/3 and shifting out. Why, HEAT. When you gear up (taller gears)you essentially increase the load through the entire range on the belt. When you increase the load you also increase the heat.
Like i said some clutches handle getting geared up, while some don't like it and you end up chasing your tail with clutching issues.
BRP clutches already run too hot and taller gears will just amplify the heat and eventual belt failures that they are already known for.
If you do gear up as your saying, expect much hotter clutches, even with boost.

Sorry i made a correction in my post, i had it reversed and didn't notice till i reread it.

yes clutch engagement will be the same but changing gearing will still load the motor hard which turbo engines like. Look at evey turbo car going they run very low hard vs NA or other power addres. Clutches now have no heat issues at all do 5 pulls back to back belt isn’t hot and can hold your hand on both clutches. Same hill on a stock 850 4 times and burnt my skin bumping the primary. Over 3000km and this sled has had 1 belt swapped. With the setup it has now your 90 + hp over what stock is i don’t see why it couldn’t handle more gearing. I’ve rode a 174 with boost and compair d to that the 163 gearing is way way better I can’t see one more step in the same direction over stock haveinf a negative effect with that much extr hp. Clutching is great and wouldn’t change a thing unless boost was going to get turned up and just add more weight. I’ve rode a lot of turbo xm setup and the gtx makes boost fast and pull the hardest I can’t see why you think it wouldn’t benefit from a gear seap you can tell when riding it has more then enough power.
 

Lund

Active VIP Member
Joined
May 4, 2013
Messages
4,243
Reaction score
11,242
Location
Vernon/Kelowna
I’m not saying you would not benefit, you just need to know the draw backs of it.
If your clutching is what you say then you might be golden.
I also caution anyone who tries to compare auto performance tuning to sled performance tuning. Car don’t use centrifugal clutches that compensate for load changes.
I’m busy at the moment but later today I can give you a better understanding of gearing changes and effects. It doesn’t really change the load on your motor till you have actually maxed out the old ratio.
 

ktmsx350f

Active VIP Member
Joined
Nov 9, 2014
Messages
587
Reaction score
514
Location
fort mcmurray
Doesn’t make a difference what trans a turbo engine like to be loaded hard. Gearing won’t change clutch engagement but sure will change how it spools.
 
Last edited:

ktmsx350f

Active VIP Member
Joined
Nov 9, 2014
Messages
587
Reaction score
514
Location
fort mcmurray
Almost forgot to report back but gearing change is awesome sled pulls out of the hole hard and has loads of track speed awesome in the trees and climbing
 

bayman

Active VIP Member
Joined
Nov 11, 2008
Messages
913
Reaction score
725
Location
Calgary
Got a couple of gearing ratios in mind for XM summit 174. Running 7lbs of boost with a QR11 helix, 225/330 secondary, 200/290 primary, walk around about 280lbs with gear. What are your guys thoughts on high versus low gearing? i have a set up that will yield 2.83 ration and another that will yield 2.32, both running without a chain tensioner to avoid the dreaded dogleg. School me on what would be better and why.
 

mountainsledmania

Active VIP Member
Joined
Dec 28, 2009
Messages
1,187
Reaction score
1,231
Location
sherwoodpark
Got a couple of gearing ratios in mind for XM summit 174. Running 7lbs of boost with a QR11 helix, 225/330 secondary, 200/290 primary, walk around about 280lbs with gear. What are your guys thoughts on high versus low gearing? i have a set up that will yield 2.83 ration and another that will yield 2.32, both running without a chain tensioner to avoid the dreaded dogleg. School me on what would be better and why.

I run 2.42 on my boost it t3 @5lbs. and it perfect, belt sits exactly where its supposed to be. PS i put a p85 and team secondary on my machine.... and the difference is freakin rediculous.
 

mountainsledmania

Active VIP Member
Joined
Dec 28, 2009
Messages
1,187
Reaction score
1,231
Location
sherwoodpark
School me please, in what ways? Tunability? Driveability? Seen this mod and wonder

I all aspects. they are consistent, they are easy to service, i can tune it in under 3 min without removing the primary from the machine, i can remover the secondary and service everything behind if need be, me clutch heat issues are virtually non existent anymore, the track speed is faster, the infamous etec turbo bog is no more from a dead stop full stab and it lights rite up. i can go on and on. Im gunna go out on a limb and say my 5lb xm with the p85 and team will give an 850 turbo at the same boost with the stock ****ty doo clutches and embarrassing spanking. I can say that because i have an 850 silber turbo...
 

kingcat162

Active VIP Member
Joined
Dec 16, 2013
Messages
1,292
Reaction score
1,582
Location
Alberta
I all aspects. they are consistent, they are easy to service, i can tune it in under 3 min without removing the primary from the machine, i can remover the secondary and service everything behind if need be, me clutch heat issues are virtually non existent anymore, the track speed is faster, the infamous etec turbo bog is no more from a dead stop full stab and it lights rite up. i can go on and on. Im gunna go out on a limb and say my 5lb xm with the p85 and team will give an 850 turbo at the same boost with the stock ****ty doo clutches and embarrassing spanking. I can say that because i have an 850 silber turbo...

Where should a guy pick up the p85 and team secondary for the xm? Price? Local in Alberta?
 

mountainsledmania

Active VIP Member
Joined
Dec 28, 2009
Messages
1,187
Reaction score
1,231
Location
sherwoodpark
Where should a guy pick up the p85 and team secondary for the xm? Price? Local in Alberta?

Ken from mountain magic is the man behind the set up. 3k is the cost for the jackshaft, secondary clutch with his custom cut helix, primary with thunder shift adjustable arms, and a carlise 803 belt. nice park is you can use it on ur 850 wen u buy one later on. best money i ever spent. Tell em Justin sent you maybe it worth something maybe not. I was just talking with him bout an mpi turbo for lunchbox's machine.
 
Top Bottom