Traction Vs Boost and Clutch Set Up

[Fords4life]

Could be wrong wouldnt be the first or last...lol but i think i remember seeing a yamaha rep saying 180 hp up to 10,000 feet was were the advertised hp came from.

 

[1nc 2000]

Could be wrong wouldnt be the first or last...lol but i think i remember seeing a yamaha rep saying 180 hp up to 10,000 feet was were the advertised hp came from.

I dont remember the exact elevation they said, but it was in one of their video clips from the launch in 16/17.

 

[AAdavis]

Ever consider 1.5" lug track? Possibly better suited to your varying conditions.

Not really I like the loosey goosey of a smaller track on the trails. I am not a powder rider. I do that on skies.

 

[AAdavis]

Need more details such as who's tune or tunes, clutch details you are running now, track lug hieght, reason i'm asking is i went threw this type thing 2 seasons ago, im also at elevation had header, big pump all the garbage that goes with it.

Stock clutches with dalton arms. Hurrican header and above hood cold air intake, Mc Express intercooler. Hurrican hi alt header tune.

 

[AAdavis]

The key for consistency from deep snow spinning and hardpack hookup is in the secondary helix angle and spring settings. If clutched correctly for the both, you should not see more than a few hundred RPM difference with temps and pressures being the same. We'll need to know what the setup is prior to making suggestions. Myself, I'd be using a 35 helix with a Dalton B/O set at 90 and Hi-Torque rollers for those type of conditions. Hardback you can get by with more helix like a 39-35 or a 41-37 type of deal, but spinning in snow requires a different less aggressive setup because of the track spinning.

14.5 lbs isn't much for boost and why intake temps are easily in check, and it should boost the same wether hardback or loose snow, should be no difference there. Should you not be up at 17 lbs or more in the mountains. 14.5 would be a pretty low HP number at altitude even with a header.

17.5-18 lbs at sea level is 300 HP with a header setup. You need more boost at altitude to compensate for the lack of air. As I recall 14.5 at sea level is only 240 HP with a header and intake never gets warm at that little bit of boost level.

This brings up the effective range of a small turbo and over speeding the impeller. Their are opinions out there the hp limit of a stock turbo is 240hp. Beyond that you are just chopping up the air. Whatever hp I have at present it is plenty for the trails I ride.

 

[AAdavis]

My first thought was those clamps on the backside of throttle bodies.

I have done all of that. It does not leak at present.

 

[AAdavis]

Boost has to be higher at altitude to compensate for less density, hence at altitude it would need to increase in pressure to make up for it. Boost should read higher than at sea level for same given HP. The turbo is going to work harder yes.

The ECU compensates for barometric pressure, allowing for more boost as you go up in elevation to keep HP levels. The boost is not fixed and it’s gonna be different every day based on barometric pressure differences, with the ECU compensating for it.

Well the day I hit the rev limit I am sure it had more than 14.5 pounds of boost.

 

[AAdavis]

Not sure what's on the dash as I never look at it anyway, it should be intake manifold boost, but on the logs, boost is actual boost in the manifold taken there, and the ECU compensates for going up in altitude, or a decrease in barometric pressure, as its taking in to consideration the barometric pressure and compensating to keep the HP in close proximity to what the power level is supposed to be. What's in front of the throttle bodies for pressure should also be what's behind the throttle bodies for pressure at wide open. Boost measured at anypoint in the intake tract should measure the same no matter where you pull it from, with the exception of measuring behind the throttle bodies if not in a wide open state.

The issue is the boost (MAP) sensor psi, which is the pressure behind the throttle bodies, is only using the stock map sensor and it ends up being tapped out at that 16-17 lbs. even if you are boosting upwards at say 20 psi at the intake manifold. So if the air density gets worse as you climb, or a low pressure day, the boost is supposed to increase. Now if the tuners change these parameters in the ECU, then all bets are off on that, but in essence more altitude is going to need more boost to make the same power at sea level, so yes, the turbo is going to be working harder and be less efficient in doing its job. I doubt 300 HP is attainable when you get to a certain point on the stock turbo like we can achieve at sea level, my guess is 270 HP at best may be maxing it out for these guys at mile high and above.

All I know is NA sleds get real anemic and slow at altitude, and thats why everyone boosts them up there to help them get thru the snow.

No matter what, 14.5 lbs of boost as he states he had, would barley be making much for power. I'd guess about 240 with a header tune depending on altitude, and that little bit of boost level certainly isn't taxing the intercooler much at all. It seems like it should be boosting higher than that by a wide margin. I'd only be guessing you need 17-18 lbs of boost on the logs to get 270 at altitude, vs getting 300 at sea level. Like I said thats only a guess, but 14.5 lbs isn't much at altitude and its not the spinning the track and soft snow causing it. They still boost up even spinning the track.

Well my experience this week was with better traction it was making more power (I assume from more boost) at tagged the rev limit for the first time ever.

 

[AAdavis]

As i recall working with Dave from hurricane a few seasons ago dialing in my 240,270,300 header tunes out here @ 6500 feet of elevation 300hp was alittle over 20psi, 270 was making around 18psi and 240 as close as we could get her tamed down was 16-17 psi

 

[AAdavis]

I need to data log again to see the boost # if I tag the rev limit again. That 14.5 # was a very short pull.

 

[Simplespeed]

Interesting to say the least and not normal and makes no sense… You had sled apart to fix leaks so I would start by checking your work , checking for broken spring, waste gate and or blow off value problems, since your problem is inconsistent performance…

 

[Doc Harley]

Very complex to be sure. Ever changing conditions, make it almost impossible.
I was taught from the group to figure out traction B4 clutching.
So, if it were me, I'd try to narrow that down, first. Suspension changing can yield big dividends, dependent on riding style & conditions.
With the limiting factor being a 1" track, that you like to get sideways with.
I'm assuming the climate is on the warmer side of things. And trail never gets a chance to really tighten up.

 

[KnappAttack]

This brings up the effective range of a small turbo and over speeding the impeller. Their are opinions out there the hp limit of a stock turbo is 240hp. Beyond that you are just chopping up the air. Whatever hp I have at present it is plenty for the trails I ride.

At sea level its closer to 300HP, at altitude I suspect you'd be up at 270 or so I suspect. The higher the boost of course the more intake heat as you know already.

The stock turbo has made 400 at mid 30's for boost on the pro-mods, but they only make 5 second blasts at that. Doesn't mean it efficient there, but max kackle is what you do when racing.

 

[DooZ]

At sea level its closer to 300HP, at altitude I suspect you'd be up at 270 or so I suspect. The higher the boost of course the more intake heat as you know already.

The stock turbo has made 400 at mid 30's for boost on the pro-mods, but they only make 5 second blasts at that. Doesn't mean it efficient there, but max kackle is what you do when racing.

Is it possible that he's not loading the engine enough?

 

[AAdavis]

Well after mother nature pumped 60 inches of snow in a week at the Tetons the sun came out and I got a ride in and did some data logging. The snow was soft and loose. I was digging 3 to 4 inches deep into the trail any time the throttle was wide open up to 90mph. The boost would run from 14.5 up to 16psi, the high number coming in between 80 and 90 mph. The rpm was between 8200 to 8500rpm. A/F ratio was 11/1.The logs were taken at 9000ft. On the same trail with better traction I was tagging the rev limit. I would guess the boost on that day 17 to 18psi. I suspect I have less traction than anyone. I am at a higher elevation than anyone else running trails. If someone has a data log on a trial at this elevation I would love to see it! I have no doubt that traction does affect boost and clutch tuning. I also believe that altitude affects boost. Having said all that I am satisfied with how it runs and the set up of the track for what I like to ride.